Asessment of the Cardiovascular System
ANATOMY AND PHYSIOLOGY REVIEW
Heart
Structure. The human heart is a cone-shaped, hollow, muscular organ located in the mediastinum between the lungs. It is approximately the size of an adult fist. The heart rests on the diaphragm, tilting forward and to the left in the client’s chest. This small organ must pump continuously. Each beat of the heart pumps approximately 60 mL of blood, or approximately 5 L/min. During strenuous physical activity, the heart can double the amount of blood pumped to meet the increased oxygeeeds of the peripheral tissues.
Surface anatomy of the heart.
The heart is encapsulated by a protective covering called the pericardium. Cardiac muscle tissue is composed of three layers: epicardium, myocardium, and endocardium. The epicardium, the outer surface, is a thin, transparent tissue. The myocardium, the middle layer, is composed of striated muscle fibers interlaced into bundles. This layer is responsible for the contractile force of the heart. The innermost layer, the endocardium, is composed of endothelial tissue. This tissue lines the inside of the chambers of the heart and covers the four heart valves.
CHAMBERS OF THE HEART
A muscular wall (septum), separates the heart into two halves: right and left. Each half has an upper chamber (atrium) and a lower chamber (ventricle).
RIGHT SIDE. The right atrium is a thin-walled structure that receives deoxygenated venous blood (venous return) from all peripheral tissues by way of the superior and inferior venae cavae and from the heart muscle by way of the coronary sinus.
Most of this venous return flows passively from the right atrium, through the opened tricuspid valve, and to the right ventricle during ventricular diastole, or filling. The remaining venous return is actively propelled by the right atrium into the right ventricle during atrial systole, or contraction.
The right ventricle is a flat muscular pump located behind the sternum. The right ventricle generates enough pressure (approximately
LEFT SIDE. After blood is reoxygenated in the lungs, it flows freely from the four pulmonary veins into the left atrium. Blood then flows through an opened mitral valve into the left ventricle during ventricular diastole. When the left ventricle is almost full, the left atrium contracts, pumping the remaining blood volume into the left ventricle. With systolic contraction, the left ventricle generates enough pressure (approximately
The left ventricle is ellipsoid in shape and is the largest and most muscular chamber of the heart. Its wall is two to three times the thickness of the right ventricular wall. The left ventricle must generate a higher pressure than the right ventricle because it must contract against a high-pressure systemic circulation, which imposes a greater resistance to flow.
Blood is propelled from the aorta throughout the systemic circulation to the various tissues of the body; blood returns to the right atrium because of pressure differences. The pressure of blood in the aorta of a young adult averages approximately 100 to
HEART VALVES
The four cardiac valves are responsible for maintaining the forward flow of blood through the chambers of the heart. These valves open and close passively in response to pressure and volume changes within the cardiac chambers. The cardiac valves are classified into two types: atrioventricular (AV) valves and semilunar valves. Both AV valves are supported by chordae tendineae, which keep them from everting into the atria during systole.
ATRIOVENTRICULAR VALVES. The AV valves separate the atria from the ventricles. The tricuspid valve is composed of three leaflets and separates the right atrium from the right ventricle. The mitral (bicuspid) valve is composed of two leaflets and separates the left atrium from the left ventricle.
During ventricular diastole, the valves act as funnels and facilitate the flow of blood from the atria to the ventricles. During systole, the valves close to prevent the backflow (re-gurgitation) of blood into the atria.
SEMILUNAR VALVES. There are two semilunar valves: the pulmonic valve and the aortic valve. The pulmonic valve separates the right ventricle from the pulmonary artery. The aortic valve separates the left ventricle from the aorta. Each semilunar valve consists of three cuplike cusps, or pockets, around the inside wall of the artery. These cusps prevent blood from flowing back into the ventricles during ventricular diastole. During ventricular systole, these valves are open to permit blood flow into the pulmonary artery and the aorta.
CORONARY ARTERIES
The heart muscle receives blood to meet its metabolic needs through the coronary arterial system . The coronary arteries originate from an area on the aorta just beyond the aortic valve. There are two main coronary arteries: the left coronary artery (LCA) and the right coronary artery (RCA). Coronary artery blood flow to the myocardium occurs primarily during diastole, when coronary vascular resistance is minimized. To maintain adequate blood flow through the coronary arteries, diastolic blood pressure must be at least
LEFT CORONARY ARTERY. The LCA divides into two branches: the left anterior descending (LAD) and the circumflex coronary artery (LCX). The LAD branch descends toward the anterior wall and the apex of the left ventricle. It supplies blood to portions of the left ventricle, ventricular septum, chordae tendineae, papillary muscle, and right ventricle.
The LCX descends toward the lateral wall of the left ventricle and apex. It supplies blood to the left atrium, the lateral and posterior surfaces of the left ventricle, and sometimes portions of the interventricular septum. In 45% of people, the LCX supplies the sinoatrial (SA) node, and in 10% of people it supplies the AV node. Peripheral branches (diagonal and obtuse marginal) arise from the LAD and LCX and form an abundant network of vessels throughout the entire myocardium.
RIGHT CORONARY ARTERY. The RCA originates from the right sinus of Valsalva, encircles the heart, and descends toward the apex of the right ventricle.
The RCA supplies the right atrium, right ventricle, and inferior portion of the left ventricle. In most people (more than 50%), the RCA supplies the SA node and the AV node. Considerable variation in the branching pattern of the coronary arteries exists among individuals.
■ Function
■ ELECTROPHYSIOLOGIC PROPERTIES OF THE HEART
The electrophysiologic properties of heart muscle are responsible for regulating heart rate and rhythm. Cardiac muscle cells are unique and possess the special characteristics of automaticity, excitability, conductivity, contractility, and refractoriness.
Automaticity refers to the ability of all cardiac cells to initiate an impulse spontaneously and repetitively. Excitability is the ability of the cells to respond to a stimulus by initiating an impulse (depolarization). Conductivity means that cardiac cells transmit the electrical impulses they receive.
Because the cells possess the property of contractility, they also contract in response to an impulse. Refractoriness means that cardiac cells are unable to respond to a stimulus until they have recovered (repolarized) from the previous stimulus. .
CONDUCTION SYSTEM OF THE HEART
The cardiac conduction system is composed of specialized tissue capable of rhythmic electrical impulse formation . It can conduct impulses much more rapidly than other cells located in the myocardium. The SA node, located at the junction of the right atrium and the superior vena cava, is considered the main regulator of heart rate. The SA node is composed of pacemaker cells, which spontaneously initiate impulses at a rate of 60 to 100 times per minute and myocardial working cells, which transmit the impulses to the surrounding atrial muscle. An impulse from the SA node initiates the process of depolarization and hence the activation of all myocardial cells. The impulse travels through both atria to the atrioventricular (AV) node located in the junctional area. After the impulse reaches the AV node, conduction of the impulse is delayed briefly. This delay allows the atria to contract completely before the ventricles are stimulated to contract. The intrinsic rate of the AV node is 40 to 60 beats/min.
The Bundle of His is a continuation of the AV node and is located in the interventricular septum. It divides into the right and left bundle branches. The bundle branches extend downward through the ventricular septum and fuse with the Pur-kinje fiber system. The Purkinje fibers are the terminal branches of the conduction system and are responsible for carrying the wave of depolarization to both ventricular walls. Purkinje fibers can act as an intrinsic pacemaker, but their discharge rate is only 20 to 40 beats/min. Thus these intrinsic pacemakers seldom initiate an electrical impulse.
SEQUENCE OF EVENTS DURING THE CARDIAC CYCLE
The phases of the cardiac cycle are generally described in relation to changes in pressure and volume in the left ventricle during filling (diastole) and ventricular contraction (systole). Diastole, normally about two thirds of the cardiac cycle, consists of relaxation and filling of the atria and ventricles, whereas systole consists of the contraction and emptying of the atria and ventricles.
Cardiac muscle contraction results from the release of large numbers of calcium ions from the sarcoplasmic reticulum. These ions diffuse into the myofibril sarcomere (the basic contractile unit of the myocardial cell). Calcium ions promote the interaction of actin and myosin protein filaments, causing these filaments to link and overlap. Cross-bridges, or linkages, are formed as the protein filaments slide over or overlap each other. These cross-bridges act as force-generating sites. The sliding of these protein filaments of multiple myofibril sarcomeres shortens the sarcomeres, producing myocardial contraction. Cardiac muscle relaxes when calcium ions are pumped back into the sarcoplasmic reticulum, causing a decrease in the number of calcium ions around the myofibrils. This reduced number of ions causes the protein filaments to disengage or dissociate, the sarcomere to lengthen, and the muscle to relax.
MECHANICAL PROPERTIES OF THE HEART
The electrical and mechanical properties of cardiac muscle determine the function of the cardiovascular system. The heart is able to adapt to various pathophysiologic conditions (e.g., stress, infections, and hemorrhage) to maintain adequate blood flow to the various body tissues.
Blood flow from the heart into the systemic arterial circulation is measured clinically as cardiac output (CO), the amount of blood pumped from the left ventricle each minute. CO depends on the relationship between heart rate (HR) and stroke volume (SV); it is the product of these two variables:
Cardiac output = Heart rate x Stroke volume
CARDIAC OUTPUT AND CARDIAC INDEX. Cardiac output (CO) is the volume of blood (in liters) ejected by the heart each minute. In adults, the CO ranges from 4 to 7 L/min. Because cardiac output requirements vary according to body size, the cardiac index is calculated to adjust for differences in body size.
The cardiac index can be determined by dividing the CO by the body surface area. The normal range is 2.7 to 3.2 L/min/m2 of body surface area.
HEART RATE. Heart rate refers to the number of times the ventricles contract each minute. The normal resting heart rate for an adult is between 60 and 100 beats/min.
Increases in heart rate increase myocardial oxygen demand. Heart rate is extrinsically controlled by the autonomic nervous system, which adjusts rapidly wheecessary to regulate cardiac output. The parasympathetic system slows the heart rate, whereas sympathetic stimulation has an excitatory effect. An increase in circulating endogenous catecholamine (e.g., epinephrine and norepinephrine) usually causes an increase in heart rate, and vice versa.
Other factors, such as the central nervous system (CNS) and baroreceptor (pressoreceptor) reflexes, influence the effects of the autonomic nervous system on heart rate. Pain, fear, and anxiety can increase heart rate. The baroreceptor reflex acts as a negative-feedback system. If a client experiences hypotension, the baroreceptors in the aortic arch sense a lessened pressure in the blood vessels. A signal is relayed to the parasympathetic system to have less of an inhibitory effect on the sinoatrial (SA) node; this results in a reflex increase in heart rate.
STROKE VOLUME. Stroke volume is the amount of blood ejected by the left ventricle during each systole. Severalvariables influence stroke volume and, ultimately, CO. These variables include heart rate, preload, afterload, and contractility.
PRELOAD. Preload refers to the degree of myocardial fiber stretch at the end of diastole and just before contraction. The stretch imposed on the muscle fibers results from the volume contained within the ventricle at the end of diastole. Preload is determined by left ventricular end-diastolic (LVED) volume.
An increase in ventricular volume increases muscle fiber length and tension, thereby enhancing contraction and improving stroke volume. This statement is derived from Starling’s law of the heart: the more the heart is filled during diastole (within limits), the more forcefully it contracts. However, excessive filling of the ventricles results in excessive LVED volume and pressure and a decreased cardiac output
AFTERLOAD. Another determinant of stroke volume is afterload. Afterload is the pressure or resistance that the ventricles must overcome to eject blood through the semilunar valves and into the peripheral blood vessels. The amount of resistance is directly related to arterial blood pressure and the diameter of the blood vessels.
Impedance, the peripheral component of afterload, is the pressure that the heart must overcome to open the aortic valve. The amount of impedance depends on aortic compliance and total systemic vascular resistance, a combination of blood viscosity and arteriolar constriction. A decrease in stroke volume can result from an increase in afterload without the benefit of compensatory mechanisms.
CONTRACTILITY. Contractility also affects stroke volume and CO. Myocardial contractility is the force of cardiac contraction independent of preload. Contractility is increased by factors such as sympathetic stimulation and calcium release. Factors such as hypoxia and acidemia decrease contractility.
Vascular System
The vascular system serves several purposes:
Ø To provide conduits for blood to travel from the heart to
nourish the various tissues of the body
Ø To carry cellular wastes to the excretory organs
Ø To allow lymphatic flow to drain tissue fluid back into the circulation
Ø To return blood to the heart for recirculation
This system of conduits depends on an efficient heart and patent blood vessels to regulate and maintain systemic and regional blood flow and temperature.
The vascular system is divided into the arterial system and the venous system. In the arterial system, blood moves from the larger conduits to a network of smaller blood vessels. In the venous system, blood travels from the capillaries to the venules and to the larger system of veins, eventually returning in the venae cavae to the heart for recirculation.
■ ARTERIAL SYSTEM
■ Structure
The high-pressure blood vessels of the arterial vascular system may be classified according to their size and wall structure. The large arteries, such as the aorta and femoral arteries, follow relatively straight routes and have few branches.
Smaller arteries, such as the internal iliac and mesenteric arteries, divide from larger ones and have multiple branches.
Arteries may branch into arterioles or anastomose with other arteries. The arterioles branch into terminal arterioles, which join with capillaries and ultimately with venules to form the capillary network. The exchange of nutrients across the capillary membrane occurs primarily by three processes: osmosis, filtration, and diffusion.
■ Function
The arterial system delivers blood to various tissues for nourishment. At the tissue level, nutrients, chemicals, and body defense substances are distributed and exchanged for cellular waste products, depending on the needs of the particular tissue. The arteries transport the cellular wastes to the excretory organs (e.g., kidneys and lungs) to be reprocessed or removed. The arteries also contribute to temperature regulation in the tissues. Blood can be either directed toward the skin to promote heat loss or diverted away from the skin to conserve heat.
■ Blood Pressure
Blood pressure is the force of blood exerted against the vessel walls. Pressure in the larger arterial blood vessels is greater (about 80 to
■ INDIRECT MEASUREMENT OF BLOOD PRESSURE
The blood pressure in the arterial system is determined primarily by the quantity of blood flow or cardiac output (CO), as well as by the resistance in the arterioles:
Blood pressure = Cardiac output x Peripheral vascular resistance
Any factor that increases CO or total peripheral vascular resistance increases blood pressure. In general, blood pressure is maintained at a relatively constant level; therefore an increase or decrease in total peripheral vascular resistance is associated with a decrease or an increase in CO, respectively.
Three mechanisms mediate and regulate blood pressure:
Ø The autonomic nervous system, which excites or inhibits sympathetic nervous system activity in response to impulses from chemoreceptors and baroreceptors
Ø The kidneys, which sense a change in blood flow and activate the renin-angiotensin-aldosterone mechanism
Ø The endocrine system, which releases various hormones (e.g., catecholamine, kinins, serotonin, and histamine) to stimulate the sympathetic nervous system at the tissue level
Systolic blood pressure represents the amount of pressure/force generated by the left ventricle to distribute blood into the aorta with each contraction of the heart; diastolic blood pressure represents the amount of pressure/force sustained by the arteries during the relaxation phase of the heart. In the adult, systolic pressure is normally 90 to
Systolic pressure is affected by a number of factors, including CO. When CO decreases, systolic pressure also decreases. Diastolic pressure is primarily determined by the amount of vasoconstriction in the periphery. An increase in peripheral vascular resistance increases diastolic pressure and cardiac workload.
REGULATION OF BLOOD PRESSURE
The autonomic nervous system (ANS) and the renal system are primarily responsible for regulating blood pressure. External factors can also affect blood pressure.
Autonomic nervous system. Blood pressure is regulated by balancing the sympathetic and parasympathetic nervous systems of the autonomic nervous system. Changes in sympathetic and parasympathetic activity are responses to messages sent by the sensory receptors in the various tissues of the body. These receptors, including the baroreceptors, chemoreceptors, and stretch receptors, respond differently to the biochemical and physiologic changes of the body.
Baroreceptors in the arch of the aorta and at the origin of the internal carotid arteries are stimulated when the arterial walls are stretched by an increased blood pressure. Impulses from these baroreceptors inhibit the vasomotor center, which is located in the pons and the medulla. Inhibition of this center results in a drop in blood pressure.
Several 1- to 2-mm collections of tissue have been identified in the bifurcations of the carotid arteries and along the aortic arch. These carotid and aortic bodies contain specialized chemoreceptors that are sensitive primarily to hypoxemia (a decrease in the partial pressure of arterial oxygen [Pao2]). When stimulated, the carotid chemoreceptors send impulses along Hering’s nerves, and the aortic chemoreceptors send impulses along the vagus nerves to activate a vasoconstrictor response.
The chemoreceptors are also stimulated by hypercapnia (an increase in partial pressure of arterial carbon dioxide [Paco2]) and acidosis. However, the direct effect of carbon dioxide on the central nervous system is 10 times stronger than the effect it produces by stimulating the chemoreceptors.
Stretch receptors found in the venae cavae and the right atrium are sensitive to pressure or volume changes. When a client is hypovolemic, the stretch receptors in the blood vessels sense a reduced volume or pressure and send fewer impulses to the central nervous system. This reaction stimulates the sympathetic nervous system to increase heart rate and constrict the peripheral blood vessels.
Renal system. The renal system also helps to regulate cardiovascular activity. When renal blood flow or pressure decreases, the kidneys retain sodium and water. Blood pressure tends to rise because of fluid retention and because of activation of the renin-angiotensin-aldosterone mechanism. Vascular volume is also regulated by the release of antidi-uretic hormone (vasopressin) from the posterior pituitary gland.
External factors. Other factors can influence the activity of the cardiovascular system. Emotional behaviors (e.g., excitement, pain, anger) stimulate the sympathetic nervous system to increase blood pressure and heart rate. Increased physical activity such as exercise increases blood pressure and pulse rate. Body temperature can affect the metabolic needs of the tissues, thereby influencing the delivery of blood. In hypothermia, tissues require fewer nutrients and blood pressure sure falls. In hyperthermia, the metabolic requirement of the tissues is greater, and blood pressure and pulse rate rise.
VENOUS SYSTEM
■ Structure
The venous system is composed of a series of veins that are located adjacent to the arterial system. A second superficial venous circulation runs parallel to the subcutaneous tissue of the extremity. These two venous systems are connected by communicating veins that provide a means for blood to travel from the superficial veins to the deep veins. Blood flow is directed toward the deep venous circulation.
The venules collect blood from the capillaries and the terminal arterioles. White blood cells also enter and exit the body tissues at the venules.
Venules branch into veins, which are low-pressure blood vessels. Veins have the ability to accommodate large shifts in volume with minimal changes in venous pressure. This flexibility allows the venous system to accommodate the administration of intravenous (IV) fluids and blood transfusions, blood loss, and dehydration. All veins in the superficial and deep venous systems in the legs (except the smallest and the largest veins) have valves that direct blood flow back to the heart; this prevents retrograde flow (backflow).
■ Function
The primary function of the venous system is to complete the circulation of blood by returning blood from the capillaries to the right side of the heart. The venous system also acts as a reservoir for a large portion of the blood volume. In contrast to the arterial system, which consists of a high-pressure, continuous flow system through relatively rigid conduits, the venous system consists of a low-pressure, intermittent flow system through collapsible tubes that work against the effects of gravity.
Gravity exerts an increase in hydrostatic pressure (capillary blood pressure) when the client is in an upright position, which delays venous return. Hydrostatic pressure is lessened when the client is lying down, and thus there is less hindrance of venous return to the heart.
Cardiovascular Changes Associated with Aging
A number of physiologic changes in the cardiovascular system occur with advancing age. Many of these changes result in a loss of cardiac reserve. Thus these changes are usually not evident when the older adult is resting. They become apparent only when the person is physically or emotionally stressed and the heart cannot meet the increased metabolic demands of the body.
ASSESSMENT TECHNIQUES
History
The nurse obtains a thorough history, which includes demographic data, personal and family history, diet, socioeconomic status, and a functional assessment. The focus of the history is on obtaining information relative to client’s risk factors and symptoms of cardiovascular disease.
■ DEMOGRAPHIC DATA
Demographic data include the client’s age, sex, and ethnic origin. The incidence of conditions such as coronary artery disease (CAD) and valvular disease increases with age (AHA, 1998). The incidence of CAD also varies with the client’s sex. Women who are premenopausal have a lower incidence of CAD than do men.
CULTURAL CONSIDERATIONS
Information about the client’s ethnic or cultural background is important because some disease conditions may be more prevalent in specific ethnic groups. For example, African Americans and Mexican Americans have a higher incidence of hypertension than do Caucasians (AHA, 1998). The nurse should be aware that some clients may refer to their hypertension as “high blood.”
Age, sex, ethnic background, and family history of cardiovascular disease are considered nonmodifiable or uncontrollable risk factors for cardiovascular disease. Modifiable risk factors (e.g., high blood pressure and excessive blood cholesterol), if controlled, can reduce the risk of heart disease.
PERSONAL AND FAMILY HISTORY
The nurse reviews the client’s history, noting any major illnesses such as diabetes mellitus, renal disease, anemia, high blood pressure, stroke, bleeding disorders, connective tissue diseases, chronic pulmonary diseases, heart disease, and thrombophlebitis. These conditions can influence the client’s cardiovascular status.
The nurse asks about previous treatment for cardiovascular disease, identifies previous diagnostic procedures (e.g., electrocardiography and cardiac catheterization), and requests information about any medical or invasive treatment of cardiovascular disease. It is important for the nurse to ask specifically about recurrent tonsillitis, streptococcal infections, and rheumatic fever, because these conditions may lead to valvular abnormalities of the heart. In addition, the nurse inquires about any known congenital heart defects. Many clients with congenital heart problems are living into adulthood because of improved treatment and surgical modalities.
Clients are asked in detail about their medication history, beginning with any current or recent use of prescription or over-the-counter (OTC) medications or herbal/natural products (e.g., ginseng). The nurse inquires about known sensitivities to any drug and the nature of the reaction (e.g., nausea, rash). Clients should be asked whether they have recently used cocaine or any IV “street” drugs, because they may be associated with chest pain or endocarditis.
The nurse also asks female clients whether they are taking oral contraceptives or an estrogen replacement. There is an increased incidence of myocardial infarction (MI) and stroke in women over the age of 35 who take oral contraceptives, but only if they smoke, have diabetes, or have hypertension
The nurse reviews the family history and obtains information about the age, health status, and cause of death of immediate family members. A family history of hypertension, obesity, diabetes, or sudden cardiac death is especially significant.
DIET HISTORY
A diet history includes the client’s recall of food and fluid intake during a 24-hour period, self-imposed or medically prescribed dietary restrictions or supplementations, and the amount and type of alcohol consumption.
The dietitian reviews the type of foods selected by the client for the amount of sodium, sugar, cholesterol, fiber, and fat. The nurse or dietitian also explores the client’s attitude toward food, knowledge level of essential and nonessential dietary elements, and willingness to make changes in the diet. Cultural beliefs and economic status can influence the choice of food items and therefore must be reviewed. Family members or significant others who are responsible for shopping and cooking are included in this discussion.
SOCIOECONOMIC STATUS
The social history includes information about the client’s domestic situation, such as marital status, number of children, household members, living environment, and occupation. The nurse also identifies support systems. It is especially important to explore the possibility that the client might have difficulty paying for medications or treatment.
The nurse asks about the client’s occupation, including the type of work performed and the requirements of the specific job. For instance, does the job involve lifting of heavy objects? Is the job emotionally stressful? What does a day’s work entail? Does the client’s job require him or her to be outside in extreme weather conditions?
MODIFIABLE RISK FACTORS
Personal habits that are risk factors for heart disease include cigarette smoking, physical inactivity, obesity, and type A behavior. These factors are considered modifiable or controllable risk factors. The nurse inquires about each of the following modifiable risk factors.
Cigarette Smoking
Cigarette smoking is a major risk factor for cardiovascular disease, specifically CAD and peripheral vascular disease (PVD) (AHA, 1998). According to the U.S. Department of Health and Human Services (DHHS), cigarette smoking is directly responsible for 21% of all deaths from CAD. Three compounds in cigarette smoke have been implicated in the development of CAD: tar, nicotine, and carbon monoxide.
The risks to the cardiovascular system from cigarette smoking appear to be dose related, noncumulative, and transient. The smoking history should include the number of cigarettes smoked daily, the duration of the smoking habit, and the age of the client when smoking started. A person who smokes fewer than 4 cigarettes per day has twice the risk of cardiovascular disease of a person who does not smoke; a person who smokes more than 20 cigarettes per day has four times the risk. Typically, the nurse records the smoking history in pack-years, which is the number of packs per day multiplied by the number of years the client has smoked.
The nurse should inquire about the client’s desire to quit, past attempts to quit, and the methods used. The nurse may ascertaiicotine dependence by asking questions such as the following:
• How soon after you wake up in the morning do you smoke?
• Do you find it difficult not to smoke in places where smoking is prohibited?
• Do you smoke when you are ill?
Three to four years after a client has stopped smoking, his or her cardiovascular risk appears to be similar to that of a person who has never smoked. The nurse asks clients who do not currently smoke whether they have ever smoked and when they quit.
Physical Inactivity
A sedentary lifestyle is also considered a significant risk factor in the development of heart disease. Regular physical activity promotes cardiovascular fitness and produces beneficial changes in blood pressure and levels of blood lipids and clotting factors.
Unfortunately, few people in the
The nurse questions clients concerning the type of exercise in which they engage, the period for which they have participated in the exercise, and the frequency and intensity of the exercise.
Obesity
Approximately 104 million Americans adults are overweight when defined as a body mass index (BMI) of 25 to 30. Another 42 million Americans are obese, which is defined as a BMI greater than 30 (AHA, 1998). Obesity in the American population has increased 36% in the last 30 years; it is particularly a problem for African-American females, Mexican Americans, and native Hawaiians (AHA, 1998).
Obesity is associated with hypertension, hyperlipidemia, and diabetes; all are known contributors to cardiovascular disease.
The nurse weighs the client, calculates the BMI, and examines the pattern of obesity, also known as the waist-hip ratio. Chapter 61 describes these assessments in detail.
Type A Personality
Researchers have identified that people with type A personalities are more vulnerable to the development of heart disease. Type A personalities are highly competitive, overly concerned about meeting deadlines, and are often hostile or angry. The nurse might ask the client: “Have you ever experienced road rage?” or “How do you respond when you have to wait for an appointment?” The chronic anger and hostility displayed by type A people appear to be most closely associated with cardiovascular disease. The constant arousal of the sympathetic nervous system as a result of anger may influence blood pressure, serum fatty acids and lipids, and clotting mechanisms. The nurse observes the client and determines his or her response to stressful situations.
CURRENT HEALTH PROBLEMS
Inquiring about major concerns helps the nurse to establish priorities iursing care and management. The client is asked to describe his or her health concerns. The nurse expands on the description of these concerns by obtaining information about their onset, duration, chronology, frequency, location, quality, intensity, associated symptoms, and precipitating, aggravating, and relieving factors. Major symptoms identified by clients with cardiovascular disease include chest pain or discomfort, dyspnea, fatigue, palpitations, weight gain, syncope, and extremity pain.
Chest Pain
Chest pain or discomfort, a cardinal symptom of heart disease, can result from ischemic heart disease, pericarditis, and aortic dissection. Chest pain can also be due to noncardiac conditions such as pleurisy, pulmonary embolus, hiatal hernia, and anxiety. Nurses must thoroughly evaluate the nature and characteristics of the chest pain. Because chest pain resulting from myocardial ischemia is life threatening and can lead to serious complications, its cause should be considered ischemic (reduced or obstructed blood flow to the myocardium) until proven otherwise.
When assessing for chest pain, the nurse uses alternative terms such as “discomfort,” “heaviness,” and “indigestion.” Clients often do not experience pain in the chest but instead feel discomfort or indigestion. The client may also describe the sensation as aching, choking, strangling, tingling, squeezing, constricting, or vise-like.
The nurse asks the client to identify when the pain was first noticed (onset). Did the pain begin suddenly or develop gradually (manner of onset)? How long did it last (duration)? If the client has repeated chest pain episodes, the nurse assesses how often the pain occurs (frequency). The nurse asks whether this pain is different from any other episodes of pain. The nurse asks the client to describe what activities he or she was doing when it first occurred, such as sleeping, arguing, or running (precipitating factors). The client can be asked to point to the area where the chest pain occurred (location) and to describe how the pain spread (radiation).
In addition, the client describes how the pain feels and whether it is sharp or dull (quality). To understand the severity of the pain, the nurse asks the client to grade it from 0 to 10, with 0 indicating an absence of pain and 10 indicating severe pain (intensity). The client may also report other signs and symptoms that occur at the same time (associated symptoms), such as dyspnea, diaphoresis, nausea, and vomiting. Other factors that need to be addressed are those that may have made the chest pain worse (aggravating factors) or less intense (relieving factors). Chest pain may arise from a variety of sources. By obtaining the appropriate information, the nurse may assist in identifying the source of the chest discomfort.
Dyspnea
Dyspnea can occur as a result of both cardiac and pulmonary disease. Dyspnea is objectively described as difficult or labored breathing and is subjectively experienced as uncomfortable breathing or shortness of breath. When obtaining the client’s history, the nurse ascertains what factors precipitate and relieve dyspnea, what level of activity produces dyspnea, and the client’s body position when dyspnea occurred.
There are several types of dyspnea. Dyspnea that is associated with activity, such as climbing stairs, is referred to as dyspnea on exertion (DOE). This is usually an early symptom of heart failure.
The client with advanced heart disease may experience or-thopnea, or dyspnea that appears when the client lies flat. The client may use several pillows at night to elevate the head and chest or may sleep in a recliner to prevent nighttime breath-lessness. The severity of orthopnea is measured by the number of pillows or the amount of head elevatioeeded to provide restful sleep. Orthopnea is usually relieved within a matter of minutes by sitting up or standing.
Paroxysmal nocturnal dyspnea develops after the client has been lying down for several hours. In this position, blood from the lower extremities is redistributed to the venous system, which increases venous return to the heart. A diseased heart is unable to compensate for the increased volume and is ineffective in pumping the additional fluid into the circulatory system. Pulmonary congestion results. The client awakens abruptly, often with a feeling of suffocation and panic. The client usually sits upright with the legs dangled over the bedside to relieve the dyspnea. This sensation may last for 20 minutes before disappearing.
Fatigue
Fatigue may be described as a feeling of tiredness or weariness resulting from activity. The client may complain that a certain activity takes longer to complete or that he or she tires easily after activity. Although fatigue in itself is not diagnostic of heart disease, many people with heart failure are limited by leg fatigue during exercise. Fatigue that occurs after mild activity and exertion usually indicates inadequate cardiac output (low stroke volume) and anaerobic metabolism in skeletal muscle. The nurse questions the client to determine the time of day he or she experiences fatigue as well as the activities that he or she can perform. Fatigue resulting from decreased cardiac output is often worse in the evening. The nurse asks whether the client can perform the same activities as a year ago or the same activities as others of the same age. Often the client limits activities in response to fatigue and unless questioned is unaware how much less active he or she has become.
Palpitations
A feeling of fluttering in the chest or an unpleasant awareness of the heartbeat is referred to as palpitations. Palpitations may result from a change in heart rate or rhythm or from an increase in the force of heart contractions. Rhythm disturbances that may cause palpitations include paroxysmal supraventricular tachycardia, premature contractions, and sinus tachycardia. Those that occur during or after strenuous physical activity, such as running and swimming, may indicate overexertion or possibly heart disease. Noncardiac factors that may precipitate palpitations include anxiety, stress, fatigue, insomnia, hyperthyroidism, and the ingestion of caffeine, nicotine, or alcohol.
Weight Gain
A sudden weight increase of
Syncope
Syncope refers to a transient loss of consciousness. The most common cause is decreased perfusion to the brain. Any condition that suddenly reduces cardiac output, resulting in decreased cerebral blood flow, can potentiate a syncopal episode. Conditions such as cardiac rhythm disturbances (ventricular dysrhythmia or Stokes-Adams attack) and valvular disorders (aortic stenosis) may potentiate this symptom.
Near-syncope refers to dizziness with an inability to remain in an upright position. The nurse explores the circumstances that lead to dizziness or syncope.
Extremity Pain
Extremity pain may be caused by two conditions: ischemia from atherosclerosis and venous insufficiency of the peripheral blood vessels. Clients who report a moderate to severe cramping sensation in their legs or buttocks associated with an activity such as walking have intermittent claudication related to reduced arterial tissue perfusion. Claudication pain is usually relieved by resting or lowering the affected extremity to decrease tissue demands or to enhance arterial blood flow. Leg pain that results from prolonged standing or sitting is related to venous insufficiency from either incompetent valves or venous obstruction. This pain may be relieved by elevating the extremity.
FUNCTIONAL HISTORY
After the history of the client’s cardiovascular status is obtained, he or she may be classified according to the New York Heart Association’s Functional Classification (Table 33-2). The four classifications (I, II, III, and IV) depend on the degree to which ordinary physical activities (routine activities of daily living [ADLs]) are affected by heart disease.
Physical Assessment
A thorough physical assessment is the foundation for the nursing database and the formation of nursing diagnoses and collaborative problems. Any changes noted during the course of illness can be compared with this initial database. The nurse evaluates the client’s vital signs on admission to the hospital or during the initial visit to the clinic or health care provider’s office.
GENERAL APPEARANCE
Physical assessment begins with the client’s general appearance. The nurse assesses the following areas: general build and appearance, skin color, distress level, level of consciousness, shortness of breath, position, and verbal responses.
Clients with chronic heart failure may appear malnourished, thin, and cachectic. Latent signs of severe heart failure are ascites, jaundice, and anasarca (generalized edema) as a result of prolonged congestion of the liver. Heart failure may cause fluid retention, and clients may have engorged neck veins and generalized dependent edema.
Coronary artery disease is suspected in clients with yellow, lipid-filled plaques on the upper eyelids (xanthelasma) or ear-lobe creases. Clients with poor cardiac output and decreased cerebral perfusion may experience mental confusion, memory loss, and slowed verbal responses.
INTEGUMENTARY SYSTEM
Assessment and evaluation of the integumentary system are determined primarily by the color and temperature of the skin. The best areas in which to assess circulation include the nail beds, mucous membranes, and conjunctival mucosa because small blood vessels are located near the surface of the skin.
Skin Color
If there is normal blood flow or adequate perfusion to a given area in light-colored skin, it appears pink, perhaps rosy in color, and it is warm to the touch. Decreased flow is depicted as cool, pale, and moist skin. Pallor is characteristic of anemia and can be seen in areas such as the nail beds, palms, and con-junctival mucous membranes.
A bluish or darkened discoloration of the skin and mucous membranes in Caucasians is referred to as cyanosis. This condition results from an increased amount of deoxygenated hemoglobin. Dark-skinned individuals may express cyanosis as a graying of the same tissues.
Central cyanosis involves decreased oxygenation of the arterial blood in the lungs and appears as a bluish tinge of the conjunctivae and the mucous membranes of the mouth and tongue. Central cyanosis may indicate impaired lung function or a right-to-left shunt found in congenital heart conditions. Because of impaired circulation, there is a marked desatura-tion of hemoglobin in the peripheral tissues, which produces a bluish or darkened discoloration of the nail beds, earlobes, lips, and toes.
Peripheral cyanosis occurs when blood flow to the peripheral vessels is decreased by peripheral vasoconstriction. The clamping down of the peripheral blood vessels results from a low cardiac output or an increased extraction of oxygen from the peripheral tissues. Peripheral cyanosis localized in an extremity is usually a result of arterial or venous obstruction.
Skin Temperature
Skin temperature can be assessed for symmetry by touching different areas of the client’s body (e.g., arms, hands, legs, and feet) with the dorsal surface of the hand or fingers. Decreased blood flow results in decreased skin temperature. Skin temperature is lowered in several clinical conditions, including heart failure, peripheral vascular disease, and shock.
EXTREMITIES
The nurse assesses the client’s hands, arms, feet, and legs for skin changes, vascular changes, clubbing, capillary filling, and edema. Skin mobility and turgor are affected by the fluid status of the client. Dehydration and aging reduce skin turgor, and edema decreases skin mobility. Vascular changes in an affected extremity may include paresthesia, muscle fatigue and discomfort, numbness, pain, coolness, and loss of hair distribution from a reduced blood supply.
Clubbing of the fingers and toes results from chronic oxygen deprivation in these tissue beds. Clubbing is characteristic in clients with advanced chronic pulmonary disease, congenital heart defects, and cor pulmonale. Clubbing can be identified by assessing the angle of the nail bed. The angle of the normal nail bed is 160 degrees. With clubbing, this angle increases to greater than 180 degrees, and the base of the nail becomes spongy.
Capillary filling of the fingers and the toes is an indicator of peripheral circulation. Pressing or blanching the nail bed of a finger or a toe produces a whitening effect; when pressure is released, a brisk return of color should occur. If color returns within 3 seconds, peripheral circulation is considered intact. If the capillary refill time exceeds 3 seconds, the lack of circulation may be due to arterial insufficiency from atherosclerosis or spasm. Older adults typically have a prolonged capillary refill. Rubor (dusky redness) that replaces pallor in a dependent foot suggests arterial insufficiency.
Peripheral edema is a common finding in clients with cardiovascular problems. The location of edema helps the nurse to determine its potential cause. Bilateral edema of the legs may be seen in clients with heart failure or chronic venous insufficiency. Abdominal and leg edema can be seen in clients with heart disease and cirrhosis of the liver. Localized edema in one extremity may be the result of venous obstruction (thrombosis) or lymphatic blockage of the extremity (lymph-edema). Edema may also be noted in dependent areas, such as the sacrum, when a client is confined to bed.
The nurse documents the location of edema as precisely as possible (e.g., midtibial or sacral) and the number of centimeters from an anatomic landmark. Although some health care severe (or 1 + , 2+, 3 + , or 4+), there is no universal scale. In addition, these values are not precise and are subjective. Instead of using a grading scale, the nurse determines whether the edema is pitting (the skin can be indented) or nonpitting, the depth of the pit (in millimeters), and the amount of time the pit lasts (in seconds).
BLOOD PRESSURE
Arterial blood pressure is measured indirectly by sphygmomanometry.
Normal blood pressure in adults older than 45 years of age ranges from 90 to
A blood pressure less than 90/60 mm Hg may be inadequate for providing proper and sufficient nutrition to body cells. In certain circumstances, such as shock and hypotension, the Korotkoff sounds are less audible or are absent. In these cases the nurse might palpate the blood pressure, use an ultrasonic device (Doppler device), or obtain a direct measurement by arterial catheter. When blood pressure is palpated, the diastolic pressure is usually not obtainable.
Postural Blood Pressure
Clients may report dizziness or lightheadedness when they move from a flat, supine position to a sitting or a standing position at the edge of the bed. Normally these symptoms are transient and pass quickly; pronounced symptoms may be due to orthostatic (postural) hypotension. Postural hypotension occurs when blood pressure is not adequately maintained while moving from a lying to a sitting or standing position. It is defined as a decrease of more than
To detect orthostatic changes in blood pressure, the nurse first measures the blood pressure when the client is supine. After remaining supine for at least 3 minutes, the client changes position to sitting or standing. Normally systolic pressure drops slightly or remains unchanged as the client rises, whereas diastolic pressure rises slightly. After the position change, a time delay of 1 to 5 minutes should be permitted before auscultating blood pressure and palpating the radial pulse. The cuff should remain in the proper position on the client’s arm. The nurse observes and records any signs or symptoms of distress. If the client is unable to tolerate the position change, he or she is returned to the previous position of comfort.
Paradoxical Blood Pressure
Paradoxical blood pressure is defined as an exaggerated decrease in systolic pressure by more than
decrease slightly. However, the decreased fluid volume in the ventricles resulting from these pathologic conditions produces an exaggerated or marked reduction in cardiac output.
Hepatojugular reflux is determined by locating the internal jugular vein after positioning the client with the head of the bed elevated to 45 degrees. The nurse compresses the right upper abdomen for 30 to 40 seconds. Sudden distention of the neck veins after abdominal compression is usually indicative of right-sided heart failure.
Pulse Pressure
The difference between the systolic and diastolic values is referred to as pulse pressure. A normal pulse pressure for an adult is 30 to
Proportional pulse pressure = (Systolic blood pressure – Diastolic blood pressure)/ Systolic blood pressure
A proportional pulse pressure less than 25% usually indicates a cardiac index of less than 2.2, as well as a critically low cardiac output (Stevenson & Braunwald, 1998). Narrowed pulse pressure is rarely normal and results from increased peripheral vascular resistance or decreased stroke volume in clients with heart failure, hypovolemia, or shock. Narrowed pulse pressure can also be seen in clients who have mitral stenosis or regurgitation. An increased pulse pressure may be seen in clients with slow heart rates, aortic regurgitation, atherosclerosis, hypertension, and aging.
Ankle Brachial Index
The ankle brachial index (ABI) can be used to assess the vascular status of the lower extremities. The nurse applies a blood pressure cuff to the lower extremities just above the malleoli and measures the systolic pressure by Doppler ultrasound at both the dorsalis pedis and posterior tibial pulses. The higher of these two pressures is then divided by the higher of the two brachial pulses to obtain the ankle brachial index:
Normal values for ABI are 1 or higher, because blood pressure in the legs is usually higher than blood pressure in the arms. ABI values less than 0.80 usually indicate moderate vascular disease, whereas values less than 0.50 indicate severe vascular compromise.
VENOUS AND ARTERIAL PULSATIONS
Venous Pulsations
The nurse observes the venous pulsations in the neck to assess the adequacy of blood volume and central venous pressure (CVP). The nurse can assess jugular venous pressure (JVP) to estimate the filling volume and pressure on the right side of the heart . The right internal jugular vein is usually used to estimate JVP.
JVP is normally 3 to
Arterial Pulsations
Assessment of arterial pulsations gives the nurse information about vascular integrity and circulation.
For clients with suspected or actual vascular disease, all major peripheral pulses, including the temporal, carotid, brachial, radial, ulnar, femoral, popliteal, posterior tibial, and dorsalis pedis pulses, need to be assessed for presence or absence, amplitude, contour, rhythm, rate, and equality. The nurse examines the peripheral arteries in a head-to-toe approach with a side-to-side comparison.
A hypokinetic pulse is a weak pulsation indicative of a narrow pulse pressure. It is seen in clients with hypovolemia, aortic stenosis, and decreased cardiac output.
A hyperkinetic pulse is a large, “bounding” pulse caused by an increased ejection of blood. It is seen in clients with a high cardiac output (with exercise or thyrotoxicosis) and in those with increased sympathetic system activity (with pain, fever, or anxiety).
In pulsus alternans, a weak pulse alternates with a strong pulse despite a regular heart rhythm. It is seen in clients with severely depressed cardiac function. Clients may be asked to hold their breath to exclude any false readings. The nurse may palpate the brachial or radial arteries to assess this condition, but it is more accurately assessed by auscultation of blood pressure.
Auscultation of the major arteries (e.g., carotid and aorta) is necessary to assess for bruits. Bruits are swishing sounds that may develop iarrowed arteries and are usually associated with atherosclerotic disease. The nurse can assess for the absence or presence of bruits by placing the bell of the stethoscope over the skin of the carotid artery while the client holds his or her breath. Normally there are no sounds if the artery has uninterrupted blood flow. A bruit may develop when the internal diameter of the vessel is narrowed by 50% or more, but this does not indicate the severity of disease in the arteries. Severity is determined by Doppler flow studies and arteriography.
PRECORDIUM
Assessment of the precordium (the area over the heart) involves inspection, palpation, percussion, and auscultation. In most settings the medical-surgical nurse seldom performs precordial palpation and percussion. However, the critical care nurse should perform a complete assessment (McGrath & Cox, 1998). The nurse places the client in a supine position, with the head of the bed slightly elevated for comfort. Some clients may require elevation of the head of the bed to 45 degrees for ease and comfort in breathing.
Inspection
A cardiac examination is usually performed in a systematic order, beginning with inspection. The nurse inspects the chest from the side, at a right angle, and downward over areas of the precordium where vibrations are visible. Cardiac motion is of low amplitude, and sometimes the inward movements are more easily detected by the naked eye.
The nurse examines the entire precordium, focusing on the seven precordial areas and noting any prominent precordial pulsations.
Movement over the aortic, pulmonic, and tricuspid areas is abnormal. Pulsations in the mitral area (the apex of the heart) are considered normal and are referred to as the apical impulse, or the point of maximal impulse (PMI). The PMI should be located at the left fifth intercostal space (ICS) in the midclavicular line. If the apical impulse appears in more than one intercostal space and has shifted lateral to the midclavicular line, it may indicate left ventricular hypertrophy.
Palpation
The nurse palpates with the fingers and the most sensitive part of the palm of the hand to detect precordial motion and thrills, respectively. The nurse palpates by inching his or her hand in a Z pattern along the chest, starting with the aortic area and passing through all seven areas. Turning the client on his or her left side brings the heart closer to the surface of the chest. This may be helpful in achieving maximum tactile sensitivity.
An abnormal forceful thrust accompanied by a sustaining outward movement over the left anterior side of the chest usually indicates left ventricular enlargement. An outward systolic lift along the left sternal border that extends from the fourth to the fifth intercostal space represents right ventricular enlargement.
Heaves and lifts are terms found with pulsations associated with valvular diseases or pulmonary hypertension. Thrills are vibrations associated with abnormal heart valve function (mitral regurgitation, tricuspid regurgitation, and pulmonic stenosis). When palpating for heaves or thrills, the nurse should consider several factors, including location, amplitude, duration, distribution, and timing in relation to the cardiac cycle.
Percussion
Cardiac size is determined most accurately by chest x-ray examination; percussion is now rarely used to determine the size of the heart. However, the size of the left ventricle can be estimated by locating the apical impulse by inspection and palpation.
Auscultation
Auscultation evaluates heart rate and rhythm, cardiac cycle (systole and diastole), and valvular function. The technique of auscultation requires a good-quality stethoscope and extensive clinical practice. The medical-surgical nurse needs to be familiar with normal heart sounds. The critical care nurse, telemetry nurse, and advance practice nurse should be able to identify common abnormal heart sounds.
The nurse evaluates heart sounds in a systematic order. Examination usually begins at the aortic outflow tract area and progresses slowly to the apex of the heart. The diaphragm of the stethoscope is pressed tightly against the chest to listen for high-frequency sounds and is useful in listening to the first and second heart sounds and high-frequency murmurs. The nurse then repeats the progression from the base to the apex of the heart using the bell of the stethoscope, which is held lightly against the chest. The bell is able to screen out high-frequency sounds and is useful in listening for low-frequency gallops (diastolic filling sounds) and murmurs.
The nurse auscultates by inching a stethoscope in a Zpattern across the base of the heart, down the left sternal border, then over to the apex. Auscultation checks for heart rate and rhythm, murmurs, extrasystolic sounds, and rubs in the presence of a current or suspected cardiac problem.
NORMAL HEART SOUNDS
The first heart sound (S,) is created by the closure of the mitral and tricuspid valves (atrioventricular valves). When auscultated, the first heart sound is softer and longer; it is of a low pitch and is best heard at the lower left sternal border or the apex of the heart. It may be identified by palpating the carotid pulse while listening. S, marks the beginning of ventricular systole and occurs right after the QRS complex on the electrocardiogram (ECG).
The first heart sound can be accentuated or intensified in conditions such as exercise, hyperthyroidism, and mitral stenosis. A decrease in sound intensity occurs in clients with mitral regurgitation and heart failure.
The second heart sound (S2) is caused mainly by the closing of the aortic and pulmonic valves (semilunar valves). S2 is characteristically shorter. It is higher pitched and is heard best at the base of the heart at the end of ventricular systole.
The splitting of heart sounds is often difficult to differentiate from diastolic filling sounds (gallops). A splitting of S1 (closure of the mitral valve followed by closure of the tricuspid valve) occurs physiologically because left ventricular contraction occurs slightly before right ventricular contraction. However, closure of the mitral valve is louder than closure of the tricuspid valve, so splitting is ofteot heard. Normal splitting of S2 occurs because of the longer systolic phase of the right ventricle. Splitting of S, and S2 can be accentuated by inspiration (increased venous return), and it narrows during expiration.
ABNORMAL HEART SOUNDS
PARADOXICAL SPLITTING. Abnormal splitting of S2 is referred to as paradoxical splitting and is characteristic of a wider split heard on expiration. Paradoxical splitting of S2 is heard in clients with severe myocardial depression that causes early closure of the pulmonic valve or a delay in aortic valve closure. Such conditions include myocardial infarction, left bundle branch block, aortic stenosis, aortic regurgitation, and right ventricular pacing.
GALLOPS AND MURMURS. Gallops and murmurs are common abnormal heart sounds that may occur with heart disease.
GALLOPS. Diastolic filling sounds (S3) and (S4) are produced when blood enters a noncompliant chamber during rapid ventricular filling. The third heart sound (S3) is produced during the rapid passive filling phase of ventricular diastole when blood flows from the atrium to a noncompliant ventricle. The sound arises from vibrations of the valves and supporting structures. The fourth heart sound (S4) occurs as blood enters the ventricles during the active filling phase at the end of ventricular diastole.
S3 is termed ventricular gallop, and S4 is referred to as atrial gallop. These sounds can be caused by decreased compliance of either or both ventricles. The nurse can best hear left ventricular diastolic filling sounds with the client on his or her left side. The bell of the stethoscope is placed at the apex and at the left lower sternal border during expiration.
An S3 heart sound is probably a normal finding in children or young adults up to 30 years of age. An S3 gallop in clients older than 40 years of age is considered abnormal and represents a decrease in left ventricular compliance. S3 can be detected as an early sign of heart failure or as a ventricular sep-tal defect.
An atrial gallop (S4) may be heard in clients with hypertension, anemia, ventricular hypertrophy, myocardial infarction, aortic or pulmonic stenosis, and pulmonary emboli. It may also be heard with advancing age because of a stiffened ventricle.
The auscultation of both S3 and S4, called a summation or a quadruple gallop, is an indication of severe heart failure. If the quadruple rhythm is present and the client has tachycardia (a shortened diastole), the two sounds may actually fuse to produce a rhythm that sounds like a horse galloping.
MURMURS. Murmurs reflect turbulent blood flow through normal or abnormal valves. They are classified according to their timing in the cardiac cycle: systolic murmurs (e.g., aortic stenosis and mitral regurgitation) occur between S, and S2, whereas diastolic murmurs (e.g., mitral stenosis and aortic regurgitation) occur between S2 and S,. Murmurs can occur during presystole, midsystole, or late systole or diastole or can last throughout both phases of the cardiac cycle. They are also graded according to their intensity, depending on their level of loudness.
The nurse describes the location of a murmur by where it is best heard on auscultation. Some murmurs transmit or radiate from their loudest point to other areas, including the neck, the back, and the axilla. The configuration is described as crescendo (increases in intensity) or decrescendo (decreases in intensity). The quality of murmurs can be further characterized as harsh, blowing, whistling, rumbling, or squeaking. They are also described by pitch, usually high or low.
PERICARDIAL FRICTION RUB. A pericardial friction rub originates from the pericardial sac and occurs with the movements of the heart during the cardiac cycle. Rubs are usually transient and are a sign of inflammation, infection, or infiltration. Pericardial friction rubs may be heard in clients with pericarditis resulting from myocardial infarction and cardiac tamponade.
The three phases of cardiac movement—atrial systole, ventricular diastole, and ventricular systole—can produce three components of a rub. Usually only one or two components can be heard. A short, high-pitched scratchy sound is produced with each movement; the loudest component is heard in systole. The nurse may be most able to auscultate the rubs when the client sits, leans forward, and exhales. A pericardial friction rub is better heard with the diaphragm of the stethoscope.
Psychosocial Assessment
To many people, their heart is a symbol of their ability to exist, survive, and love. A client with a heart-related illness, whether acute or chronic, usually perceives it as a major life crisis. The client and families and significant others confront not only the possibility of death but also fears about pain, disability, lack of self-esteem, physical dependence, and changes in family dynamics. The nurse may assess the meaning of the illness to the client and family members by asking, “What do you understand about what happened to you (or the client)?” and “What does that mean to you?” When the client or family members perceive the stressor as overwhelming, formerly adequate support systems may no longer be effective. In these circumstances, the client and family members attempt to cope to regain a sense or feeling of control.
Coping behaviors vary among clients. Those who feel helpless to meet the demands of the situation may exhibit behaviors such as disorganization, fear, and anxiety. The nurse may ask the client or family members, “Have you ever encountered such a situation before?”, “How did you manage that situation?”, and “To whom can you turn for help?” The answers to these questions often reassure the client that he or she has encountered difficult situations in the past and has the ability and resources to cope with them.
A common and normal response is denial, which is a defense mechanism that enables the client to cope with threatening circumstances. The client may deny that he or she has the current cardiovascular condition, may state that it was present but is now absent, or may be excessively cheerful. Denying the seriousness of the illness while following the treatment regimen is a protective response. Denial becomes maladaptive when the client is noncompliant with significant portions of medical and nursing care.
Family members and significant others may be more anxious than the client. Often they recall all events of the illness, are unprotected by denial, and are afraid of recurrence. Disagreements often occur between the client and family members over compliance with appropriate follow-up care.
Diagnostic Assessment
LABORATORY TESTS
Assessment of the client with cardiac dysfunction includes examination of the blood for abnormalities. The examination is performed to establish a diagnosis, detect concurrent disease, assess risk factors, and monitor response to treatment.
Serum Markers of Myocardial Damage
Events leading to cellular injury cause a release of enzymes from intracellular storage, and circulating levels of these enzymes are dramatically elevated. Acute myocardial infarction (MI) (“heart attack”) can be confirmed by abnormally high levels of enzymes, isoenzymes, or markers in the serum.
CREATINE KINASE
Creatine kinase (CK) is an enzyme specific to cells of the brain, myocardium, and skeletal muscle. The appearance of CK in the blood indicates tissue necrosis or injury, with CK levels following a predictable rise and fall during a specified period. Cardiac specificity must be determined by measuring isoenzyme activity. There are three isoenzymes of CK: CK-MM is the predominant isoenzyme of skeletal muscle; CK-MB is found in myocardial muscle; and CK-BB occurs in the brain. CK-MB activity is most specific for MI and shows a predictable rise and fall during 3 days; a peak level occurs approximately 24 hours after the onset of chest pain
EARLY MARKERS OF MYOCARDIAL DAMAGE
Newer treatment modalities for early intervention after acute MI and acute ischemia require more rapid diagnosis of MI. An assay using monoclonal anti-CK-MB antibodies (stat CK) can detect myocardial necrosis accurately 3 hours after emergency department admission when examined with an electrocardiogram (ECG). Two subforms of CK-MB (CK-MB,, CK-MB2) have also been identified. Abnormal elevations of these CK subforms may occur as early as 2 hours after MI. These subforms remain elevated for up to 12 hours after MI and appear to be very sensitive and specific early diagnostic markers of MI.
Other early markers of MI are myoglobin and troponin. Myoglobin, a low-molecular weight protein found in skeletal muscle, is an early and sensitive but nonspecific marker for myocardial injury. It can be detected as early as 2 hours after an MI but is relatively nonspecific. Troponin T and I are specific markers of myocardial injury and have a wide diagnostic time frame, making them useful for clients who present several hours after the onset of chest pain.
LACTATE DEHYDROGENASE
Lactate dehydrogenase (LDH) is widely distributed in the body and is found in the heart, liver, kidney, brain, and erythrocytes. LDH elevation starts within 12 to 24 hours after an MI, peaks between 48 and 72 hours, and falls to normal in 7 days. Because LDH is not specific to the myocardial cell, an assessment of isoenzymes and patterns of elevation is necessary for confirmation of MI. There are five isoenzymes for LDH; LDH, and LDH2 are found in the heart. If the serum level of LDH! is higher than the concentration of LDH2, the pattern is said to have flipped, which signifies myocardial damage. LDH is being used less frequently now that the newer serum markers of myocardial damage, myoglobin and troponin, have been identified.
Serum Lipids
Elevated lipid levels are considered a risk factor for coronary artery disease (CAD). Cholesterol, triglycerides, and the protein components of high-density lipoproteins (HDL) and low-density lipoproteins (LDL) are evaluated to assess a client’s degree of risk for CAD. The risk for CAD is three times greater in clients with a serum cholesterol level greater than 260 mg/dL than in clients with a serum level less than 200 mg/dL.
Each of the lipoproteins contains varying proportions of cholesterol, triglyceride, protein, and phospholipid. HDL contains mainly protein and 20% cholesterol, whereas LDL is predominantly cholesterol. Elevated LDL levels are positively correlated with CAD, whereas elevated HDL levels are negatively correlated and appear to be a protective factor.
A nonfasting blood sample for the measurement of serum cholesterol levels is acceptable. If triglycerides are to be evaluated, the physician requests the specimen after a 12-hour fast.
Homocysteine
Homocysteine, an amino acid, may be an independent risk factor for the development of CVD. Although the relationship between homocysteine and CVD remains controversial, some studies suggest that elevated levels of homocysteine increase the risk of CVD as much as smoking and hyperlipemia. Clients usually fast for 10 to 12 hours before the test, and the blood must be separated and frozen within 1 hour of collection. A level less than 12 mmol/dL is considered optimal. Most insurance policies do not cover this laboratory test, which costs from $50 to $110. Eating foods rich in B vitamins and folic acid appears to lower homocysteine levels and may decrease the risk for CVD (AHA, 1998).
Blood Coagulation Tests
Blood coagulation tests evaluate the ability of the blood to clot and are important in clients with a greater tendency to form thrombi (e.g., clients with atrial fibrillation, prosthetic valves, or infective endocarditis). They are also important for clients receiving anticoagulant therapy (e.g., during cardiac surgery, after thrombolytic therapy, and during treatment of an established thrombus).
PROTHROMBIN TIME AND INTERNATIONAL NORMALIZED RATIO
Prothrombin time (PT) and International Normalized Ratio (INR) are used when initiating and maintaining therapy with oral anticoagulants, such as sodium warfarin (Coumadin, Warfilone). They measure the activity of prothrombin, fib-rinogen, and factors V, VII, and X. INR is the most reliable way to monitor anticoagulant status in warfarin therapy. The therapeutic ranges for standard anticoagulant therapy are 2.0 to 3.0 (INR)
PARTIAL THROMBOPLASTIN TIME
Partial thromboplastin time (PTT) is assessed in clients who are receiving heparin (Hepalean). It measures deficiencies in all coagulation factors except VII and XIII.
■ Arterial Blood Gases
Arterial blood gas (ABG) determinations are often obtained in clients with cardiovascular disease. Determination of tissue oxygenation, carbon dioxide removal, and acid-base status is essential to appropriate intervention and treatment. (See Chapter 15 for a complete discussion of ABGs.)
■ Serum Electrolytes
Fluid and electrolyte balance is essential for normal cardiovascular performance. Cardiac manifestations often occur when there is an imbalance in either fluids or electrolytes in the body. For example, the cardiac effects of hypokalemia (low serum potassium level) include increased electrical instability, ventricular dysrhythmias, the appearance of U waves on the electrocardiogram, and an increased risk of digitalis toxicity. The effects of hyperkalemia on the myocardium include slowed ventricular conduction and contraction followed by asystole (cardiac standstill).
Cardiac manifestations of hypocalcemia are ventricular dysrhythmias, a prolonged QT interval, and cardiac arrest. Hypercalcemia shortens the QT interval and causes AV block, digitalis hypersensitivity, and cardiac arrest.
Serum sodium values reflect fluid balance and may be decreased, indicating a fluid excess in clients with heart failure (dilutional hyponatremia).
Because magnesium regulates some aspects of myocardial electrical activity, hypomagnesemia has been implicated in some forms of rapid ventricular dysrhythmias. Another manifestation of hypomagnesemia is hypokalemia that is unresponsive to potassium replacement.
Complete Blood Count
The erythrocyte (red blood cell) count is usually decreased in rheumatic fever and infective endocarditis. It is increased in heart diseases characterized by inadequate tissue oxygenation.
Decreased hematocrit and hemoglobin levels (e.g., caused by hemorrhage or hemolysis from prosthetic valves) indicate anemia and can lead to angina or aggravate heart failure. Vascular volume depletion with hemoconcentration (e.g., hypo-volemic shock and excessive diuresis) results in an elevated hematocrit.
The leukocyte (white blood cell) count is typically elevated after a myocardial infarction and in various infectious and inflammatory diseases of the heart (e.g., infective endocarditis and pericarditis). Chapter 39 discusses the complete blood count in detail.
RADIOGRAPHIC EXAMINATIONS
Chest Radiography
Posteroanterior and left lateral x-ray views of the chest are routinely obtained to determine the size, silhouette, and position of the heart. In acutely ill clients, a simple anteroposterior view is obtained at the bedside. Cardiac enlargement, pulmonary congestion, cardiac calcifications, and placement of central venous catheters, endotracheal tubes, and hemodynamic monitoring devices are assessed by x-ray examination.
Cardiac Fluoroscopy
Fluoroscopy is a simple x-ray examination that reveals the action of the heart. Continuous visual observation of the heart, lungs, and vessel movement on a luminescent x-ray screen in a darkened room is provided. Fluoroscopy is used to place and position intracardiac catheters and IV pacemaker wires and can be helpful in identifying abnormal structures, calcifications, and tumors of the heart. In critically ill clients, fluoroscopy can be performed at the bedside for the placement of intracardiac catheters or IV pacemaker wires. Client preparation and follow-up depend on the procedure. Fluoroscopy is commonly used in conjunction with cardiac catheterization, and the client is taken to a special cardiac catheterization room.
Angiography. Angiography of the arterial vessels, or arteriography, is an invasive diagnostic procedure that involves fluoroscopy and the use of contrast media. This procedure is performed when an arterial obstruction, narrowing, or aneurysm is suspected. The radiologist performs selective arteriography to evaluate specific areas of the arterial system. For example, a coronary arteriography, which is performed during left-sided cardiac catheterization, assesses arterial circulation within the heart (see Left-Sided Heart Catheterization, p. 643). Angiography can also be performed on arteries in the extremities, mesentery, and cerebrum.
Client preparation. The radiologist explains the procedure and the risks before the client or designated responsible party signs a consent form. Because this procedure involves an injection of contrast medium (sometimes called a dye) into the arterial system, the risks are serious. Risks include allergic reaction, hemorrhage, thrombosis, embolism, renal failure, and death. The client is told to expect a warm sensation when the dye is injected.
The nurse assesses the client for any allergies to contrast medium, iodine-containing substances such as seafood, or local anesthetics. The femoral area is prepared according to the policy and procedure of the health care agency. The nurse
documents vital signs and marks and describes pulses distal to the puncture site in the client’s medical record.
Procedure. The radiologist or technician places the client in a supine position on an x-ray table in the radiology department. A radiologist usually performs this procedure and begins by injecting a local anesthetic into the tissue surrounding the artery being catheterized. Contrast medium is injected via this catheter, and fluoroscopy and x-ray studies are performed.
Follow-up care. After the procedure, the client is typically restricted to bedrest in the supine position for 4 to 6 hours. The nurse ensures that the extremity that was catheterized is not flexed during this time. A pressure dressing or bandage is kept in place over the injection site; a sandbag may be placed over the dressing.
The nurse assesses the insertion site for bloody drainage or hematoma formation, assesses the distal pulses, and compares skin temperature in the affected extremity with that in the opposite extremity. Vital signs are assessed at every dressing, pulse, and temperature check; the first measurement is obtained immediately after the client is transferred from the radiology department. These assessments usually continue every 15 minutes for 1 hour, then every 30 minutes for 2 hours, and then every 4 hours or as necessary per the health care agency’s protocol. The nurse notifies the radiologist immediately if bleeding, loss of pulses, or changes in vital signs occur. The nurse carefully administers the prescribed IV or oral fluids after the procedure, because the contrast medium may damage the kidneys.
Cardiac Catheterization
The most definitive, but most invasive, test in the diagnosis of heart disease is cardiac catheterization. Cardiac catheterization may include studies of the right or left side of the heart and the coronary arteries. Some of the most common indications for cardiac catheterization are listed in Table 33-5.
Client preparation. Many clients express anxiety and fear regarding cardiac catheterization. The nurse assesses their physical and psychosocial readiness and knowledge level.
The nurse reviews the purpose of the procedure, informs the client how long it usually takes, states who will be present, and describes the appearance of the catheterization laboratory. The client is also informed about the sensations that may be experienced during the procedure, such as palpitations (as the catheter is passed up to the left ventricle), a feeling of heat or a hot flash (as the dye is injected into either side of the heart), and a desire to cough (as the dye is injected into the right side of the heart). The nurse may use written or illustrated materials or videotapes, if available, to assist in the client’s understanding.
The risks of cardiac catheterization are usually explained by the cardiologist. The risks vary with the procedures to be performed and the client’s physical status. Right-sided heart catheterization is less risky than left-sided catheterization. Several complications may follow coronary arteriography, such as the following:
Ø Myocardial infarction (MI)
Ø Stroke
Ø Arterial bleeding
Ø Thromboembolism
Ø Lethal dysrhythmias
Ø Death
The cardiologist or radiologist obtains a written informed consent from the client or responsible party.
The client may be admitted to the hospital on the day of the catheterization procedure. Standard preoperative tests are performed, which usually include a chest x-ray examination, complete blood count, coagulation studies, urinalysis, and 12-lead electrocardiogram. The client receives nothing by mouth after midnight or has only a liquid breakfast if the catheterization is to take place in the afternoon. The catheterization site is shaved and antiseptically prepared according to policy. Nursing assessment before the procedure includes measuring the client’s vital signs, auscultating the heart and the lungs, and evaluating the peripheral pulses. The nurse questions the client about any history of allergy to iodine-containing substances (e.g., seafood and contrast agents). An antihis-tamine may be given to a client with a positive history. A mild sedative is administered before the procedure. If the client normally takes a digitalis preparation or diuretic, it is usually withheld before the catheterization
Procedure. The client is taken to the cardiac catheterization laboratory (sometimes referred to as the “cath lab”), placed in the supine position on the x-ray table, and securely strapped to the table. The nurse informs the client that this precaution is necessary because the table turns like a cradle during the procedure. The physician injects a local anesthetic at the insertion site. The nurse in the catheterization laboratory instructs the client to report any chest pain or other symptoms to the staff.
Right-sided heart catheterization.
The right side of the heart is catheterized first and may be the only side examined. The cardiologist inserts a catheter through the femoral vein to the inferior vena cava or through the basilic vein to the superior vena cava. The catheter is advanced through either the inferior or the superior vena cava and, guided by fluoroscopy, is advanced through the right atrium, through the right ventricle and, at times, into the pulmonary artery (Figure 33-13). Intracardiac pressures (right atrial, right ventricular, pulmonary artery, and pulmonary artery wedge pressures) and blood samples are obtained. A contrast dye or medium is usually injected to detect any cardiac shunts or regurgitation from the pulmonic or tricuspid valves.
Left-sided heart catheterization.
Left-sided heart catheterization is more risky than right-sided heart catheterization. The cardiologist advances the catheter retro-gradely from the femoral or brachial artery up the aorta, across the aortic valve, and into the left ventricle (Figure 33-14). Alternatively, the cardiologist may pass the catheter from the right side of the heart through the atrial septum, using a special needle to puncture the septum. Intracardiac pressures and blood samples are obtained. The pressures of the left atrium, left ventricle, and aorta, as well as mitral and aortic valve status, are evaluated. The cardiologist injects contrast dye into the ventricle; cineangiograms (rapidly changing films) evaluate left ventricular motion. Calculations are made regarding end-systolic volume, end-diastolic volume, stroke volume, and ejection fraction.
Coronary arteriography. The technique for coronary arteriography is the same as for left-sided heart catheterization. The catheter is advanced into the aortic arch and positioned selectively in the right or left coronary artery. Injection of a contrast medium permits visualization of the coronary arteries. By assessing the flow of dye through the coronary arteries, information about the site and severity of coronary lesions is obtained.
Intravascular ultrasonography. An alternative to injecting dye into the coronary arteries is intravascular ultrasonography (IVUS), which introduces a flexible catheter with a miniature transducer at the distal tip to visualize the coronary arteries. The transducer emits sound waves, which reflect off the plaque and the arterial wall, creating an image of the blood vessel. IVUS is more reliable than angiography in indicating plaque distribution and composition, arterial dissection, and degree of stenosis of the occluded artery.
Follow-up care. After cardiac catheterization, the client is typically restricted to bedrest, and the insertion site extremity is kept straight. Nursing researchers are evaluating bedrest protocols that might limit discomfort while maintaining hemostasis. The current practice is for clients to remain in bed for 4 to 6 hours. Some cardiologists allow the head of the bed to be elevated up to 30 or 45 degrees during the period of bedrest, whereas other cardiologists prefer that the client remain supine. A pressure dressing or bandage may be placed over the insertion site. A 5- or 10-pound sandbag or a C-clamp may be applied over the insertion site to ensure hemostasis.
The nurse has many postcatheterization responsibilities. Vital signs are monitored every 15 minutes for 1 hour, then every 30 minutes for 2 hours or until vital signs are stable, and then every 4 hours or according to hospital policy. The insertion site is monitored for bloody drainage or hematoma formation. Peripheral pulses in the affected extremity, as well as skin temperature and color, are monitored with every vital sign check.
The nurse must observe for complications of cardiac catheterization. Complaints of pain and discomfort at the insertion site, chest pain, nausea, or feelings of lightheadedness should be reported. The client is often attached to a cardiac monitor. If not, the nurse auscultates the heart sounds, noting rhythm and rate to detect dysrhythmias. Because the contrast medium acts as an osmotic diuretic, the nurse monitors urinary output and ensures that the client receives sufficient oral and IV fluids for adequate excretion of the dye. Pain medication for insertion site or back discomfort may be given, as ordered.
If the client experiences chest pain, dysrhythmias, bleeding, hematoma formation, or a dramatic change in peripheral pulses in the affected extremity, the nurse contacts the physician immediately and provides prompt intervention. Neurologic changes, such as visual disturbances, slurred speech, swallowing difficulties, and extremity weakness, should also be reported.
Digital Subtraction Angiography
Digital subtraction angiography (DSA) combines x-ray detection methods and a computerized subtraction technique with fluoroscopy for visualization of the cardiovascular system. There is no interference from adjacent structures, such as bone and soft tissue.
Client preparation. Digital subtraction angiography involves the injection of dye into the venous systemBefore the procedure, the nurse assesses the client for a history of allergies to contrast medium (dye), iodine, or seafood.
Procedure. For a DSA, the radiologist injects dye into the venous system via the superior vena cava. As the contrast medium circulates through the heart and the arterial system, a fluoroscopic image intensifier displays the vessels and focuses the image. A computer converts these images to numbers, and the image that was obtained before the injection is subtracted from the postinjection images.
Follow-up care. Because there is no arterial puncture and because little contrast dye is used, nursing care after DSA is not as extensive as after cardiac catheterization. The nurse monitors the client for vital signs and assesses the injection site for bleeding or discomfort.
OTHER DIAGNOSTIC TESTS
Electrocardiography
The electrocardiogram (ECG) is a routine part of every cardiovascular evaluation and is one of the most valuable diagnostic tests. Various forms are available: resting ECG, continuous ambulatory ECG (Holter monitoring), exercise ECG (stress test), and signal-averaged ECG. The resting ECG provides information about cardiac dysrhythmias, myocardial ischemia, the site and extent of myocardial infarction, cardiac hypertrophy, electrolyte imbalances, and the effectiveness of cardiac drugs.
RESTING ELECTROCARDIOGRAPHY
The ECG graphically records the electrical current generated by the heart. This current is measured by electrodes that are placed on the skin and connected to an amplifier and strip chart recorder. In the standard 12-lead ECG, five electrodes attached to the arms, legs, and chest measure current from 12 different views or leads: three bipolar limb leads, three unipolar augmented leads, and six unipolar precordial leads. Placement of the leads allows the health care provider to view myocardial electrical conduction from different axes or positions, identifying sections of the heart in which electrical conduction is abnormal.
Client preparation. The nurse explains the purpose and procedure of the resting ECG, informs the client that the test is safe and painless, and reminds him or her to lie as still as possible during the test.
Procedure. The ECG is performed with the client in a supine position with the chest exposed. Before applying the electrodes, the nurse or the technician washes the skin to reduce skin oils and improve electrode contact. To ensure good contact between the skin and the electrodes for the limb leads, the electrodes should be placed on a flat surface above the wrists and the ankles. A total of 10 electrodes are used for a standard ECG and are attached to lead wires that connect to the ECG machine. The 12-lead ECG reading is obtained by selecting the indicators on the machine.
Ambulatory electrocardiography
Ambulatory ECG (also called Holter monitoring) allows continuous recording of cardiac activity during an extended period (usually 24 hours) while the client is performing his or her usual activities of daily living (ADLs). The ambulatory ECG allows the assessment and correlation of dyspnea, chest pain, central nervous system symptoms (e.g., lightheadedness and syncope), and palpitations with actual cardiac events and the client’s activities.
Client preparation. The nurse encourages the client to maintain a normal day’s schedule. He or she is instructed to keep a diary, or log. In this diary the client notes the time of activities (e.g., eating, sleeping, walking, and working) and records any symptoms such as chest pain, lightheadedness, fainting, and palpitations. The nurse instructs the client to avoid operating heavy machinery, using electric shavers and hair dryers, and bathing or showering, because these activities may interfere with the ECG recorder. If the client is hospitalized, the nurse may need to make the diary entries.
Procedure. The ECG technician places the electrodes on the client’s chest and attaches them to the Holter monitor. The monitor is a small portable ECG tape recorder about the size of a transistor radio. It is worn in a sling or holder around the client’s chest or waist. After the prescribed monitoring period, the technician removes the electrodes and the monitor system. The ECG tape is analyzed by a microcomputer to allow correlation of the ECG findings with the activities noted in the client’s diary.
ELECTROPHYSIOLOGIC STUDIES
An electrophysiologic study (EPS) is an invasive procedure during which programmed electrical stimulation of the heart is used to induce and evaluate lethal dysrhythmias and conduction abnormalities. Clients who have survived cardiac arrest, have recurrent tachydysrhythmias, or experience unexplained syncopal episodes may be referred for EPS. Induction of the dysrhythmia during EPS permits accurate diagnosis of the dysrhythmia and aids in the search for an effective treatment. These procedures have risks similar to those for cardiac catheterization and are performed in a special catheterization laboratory, where conditions are strictly controlled and immediate treatment is available for any adverse effects.
Client preparation. The preparation for EPS parallels that for cardiac catheterization. Clients may express fear or anxiety, because attempts are made to induce lethal dysrhythmias similar to those that led to the initial hospitalization or resuscitation. The nurse reassures clients that EPS is a planned, controlled event and that immediate treatment will be available for any dysrhythmia induced during the studies. An electro-physiologist (a physician who specializes in these studies) usually explains the purpose of the studies, describes the procedure (including the benefits and risks), and obtains a written consent.
Procedure. The client is taken to a cardiac catheterization laboratory or a similar laboratory and lies in a supine position on an x-ray table. Electrodes are attached for continuous ECG monitoring, and defibrillation pads are placed on the client’s chest and back. After the nurse or technician prepares the insertion site, the electrophysiologist injects a local anesthetic, and a multipolar electrode catheter is inserted. Using fluoroscopy as a guide, the catheter is advanced until the electrodes rest in the right atrium, adjacent to the bundle of His, and in the right ventricle. Additional electrodes may be placed for endocardial mapping.
During EPS, baseline conduction times can be measured: the AH interval (conduction time from the right atrium through the His bundle) and the HV interval (conduction time from the proximal His bundle to the ventricular myocardium). The catheter may be programmed to pace at varying rates to determine the function of the SA and AV node, or it may be programmed to deliver premature paced stimuli in an effort to initiate and evaluate tachydysrhythmia.
If the dysrhythmia is induced, it may terminate spontaneously or be treated by the physician. The physician might elect to use properly timed stimuli, rapid pacing, medications, or countershock to terminate the dysrhythmia.
The client is advised to inform the staff about any symptoms he or she experiences. During rapid pacing, the client may be aware of the rapid heartbeat and state that he or she is experiencing palpitations. The client may also experience chest pain or loss of consciousness if he or she becomes hy-potensive. The client often experiences back discomfort during the procedure, because he or she must remain supine for 2 to 6 hours. Pain may develop at the insertion site as the anesthetic wears off.
Follow-up care. Follow-up care for EPS is the same as for cardiac catheterization. The nurse may provide comfort measures to alleviate back discomfort, including massage and position changes. If the client lost consciousness during the procedure and received electrical cardioversion or defibrillation, he or she may complain of chest discomfort over the area where the electrical current was applied. The nurse assesses the skin for any signs of redness, swelling, or burns. In addition, there may be memory loss for the events during the procedure, and the nurse needs to provide reassurance and calmly explain the events of the procedure.
EXERCISE ELECTROCARDIOGRAPHY (STRESS TEST)
The exercise electrocardiography test (also known as exercise tolerance, or stress, test) assesses cardiovascular response to an increased workload. The stress test helps to determine the functional capacity of the heart and screens for asymptomatic coronary artery disease. Dysrhythmias that develop during exercise may be identified, and the effectiveness of antidys-rhythmic drugs can be evaluated.
Client preparation. Because there are risks associated with exercising, the client must be adequately informed about the purpose of the test, the procedure, and the risks involved. A written consent must be obtained. Anxiety and fear are common before stress testing. The nurse assures the client that the procedure is performed in a controlled environment where prompt nursing and medical attention is available.
The client is instructed to get plenty of rest the night before the procedure. The client may have a light meal 2 hours before the test but should avoid smoking or drinking alcohol or caffeine-containing beverages on the day of the test. The cardiologist decides whether the client should stop taking any cardiac medications. He or she is advised to wear comfortable, loose clothing and rubber-soled, supportive shoes. The nurse instructs the client to tell the physician if symptoms such as chest pain, dizziness, shortness of breath, and an irregular heartbeat are experienced during the test.
Before the stress test, a resting 12-lead ECG, cardiovascular history, and physical examination are performed to check for any ECG abnormalities or medical factors that might contraindicate the test.
Emergency supplies such as cardiac drugs, a defibrillator, and other necessary resuscitation equipment are available in the room in which the stress test is performed. The nurse assisting the physician should be proficient in the use of resuscitation equipment, because chest pain, dysrhythmias, and other ECG changes may occur during this test.
Procedure. The technician places electrodes on the client’s chest and attaches them to a multilead monitoring system. The nurse notes baseline blood pressure, heart rate, and respiratory rate. The two major modes of exercise available for stress testing are pedaling a bicycle ergometer and walking on a treadmill. A bicycle ergometer has a wheel operated by pedals that can be adjusted to increase the resistance to pedaling. The treadmill is a motorized device with an adjustable conveyor belt; it can reach speeds of 1 to 10 miles/hr and can also be adjusted from a flat position to a 22-degree gradient.
After the nurse shows the client how to use the bicycle or to walk on the treadmill, he or she begins to exercise. During the test, the blood pressure and electrocardiogram (ECG) are closely monitored as the speed and incline of the treadmill or the resistance to cycling are increased. The client exercises until one of the following occurs:
• A predetermined heart rate is reached and maintained.
• Signs and symptoms such as chest pain, fatigue, extreme dyspnea, vertigo, hypotension, and ventricular dysrhythmias appear.
• Significant ST-segment depression occurs.
Follow-up care. After the test, the nurse continues to monitor the ECG and blood pressure until the client has completely recovered. After the client has recovered, he or she can return home if the test was performed on an outpatient basis. The nurse advises avoiding a hot shower for 1 to 2 hours after the test, because this may precipitate hypotension. If the client does not recover but continues to have chest pain or ventricular dysrhythmias or appears medically unstable, he or she is admitted to a coronary care unit for observation.
For clients who are unable to exercise because of conditions such as peripheral vascular disease or arthritis, pharma-cologic stress testing with agents such as dobutamine may be indicated. The nursing considerations are similar to those for the client who has undergone an exercise electrocardiography.
Echocardiography
As a noninvasive, risk-free test, echocardiography is easily performed at the bedside or on an ambulatory care basis. Echocardiography uses ultrasound waves to assess cardiac structure and mobility, particularly of the valves. ECGs help to assess and diagnose cardiomyopathy, valvular disorders, pericardial effusion, left ventricular function, ventricular aneurysms, and cardiac tumors.
Client preparation. There is no special preparation for echocardiography. The nurse informs the client that the test is painless and takes 30 to 60 minutes to complete. The client is instructed to lie quietly during the test and on his or her left side with the head elevated 15 to 20 degrees.
Procedure. During an echocardiogram, a small transducer lubricated with gel to facilitate movement and conduction is placed on the client’s chest at the level of the third or fourth intercostal space near the left sternal border. The transducer transmits high-frequency sound waves and receives them as they are reflected from different structures. These echoes are usually videotaped simultaneously with the echocardiogram and can be recorded on graph paper for a permanent record.
Figure 33-20 is a representation of how echocardiograms examine the heart. After the images are taped, cardiac measurements that require several images can be obtained. Routine measurements include chamber size, ejection fraction, and flow gradient across the valves.
Follow-up care. There is no specific follow-up care for a client who has undergone an echocardiogram.
■ Dobutamiee Stress Echocardiogram
A slightly more aggressive form of echocardiogram is a dobu-tamine stress echocardiogram (DSE), which is used to provoke physiologic stress and identify patterns of cardiac response to the stress (e.g., chamber size, wall motion, and ejection fraction). Clients are required to have nothing by mouth (NPO status) for 3 to 6 hours before the test, except for sips of water with medications. The nurse or technician ensures that IV access is present before the procedure and monitors blood pressure and pulse continuously throughout the procedure. The nurse also monitors for the development of such severe responses as angina, life-threatening dysrhyth-mias, and syncope, although such reactions are uncommon. After the procedure, the nurse or technician continues to monitor the blood pressure until it returns to baseline and monitors the pulse rate until it slows to less than 100.
■ Transesophageal Echocardiography
Echocardiograms may also be performed transesophageally. Transesophageal echocardiography examines cardiac structure and function with an ultrasound transducer placed immediately behind the heart in the esophagus or stomach. The transducer provides especially detailed views of posterior cardiac structures such as the left atrium, mitral valve, and aortic arch. Preparation and follow-up are similar to that for an upper gastrointestinal endoscopic examination.
Phonocardiography
Phonocardiography is the graphic recording of heart sounds during auscultation. It can be helpful in determining the exact timing and characteristics of extra heart sounds and murmurs. A phonocardiography machine simultaneously records the pulse wave, ECG, and heart sounds. A pressure-sensitive transducer is applied to the selected pulse (e.g., apical or carotid artery), and the ECG is obtained through standard limb leads. A special microphone, used in the same manner as a stethoscope, is applied to the various areas for auscultation on the client’s chest. Client preparation and follow-up care are similar to those for echocardiography (see p. 647).
Myocardial Nuclear Perfusion Imaging
The use of radionuclide techniques in cardiovascular assessment is called myocardial nuclear perfusion imaging (MNPI). Cardiovascular abnormalities can be viewed, recorded, and evaluated using radioactive tracer substances. These studies are useful for detecting myocardial infarction (MI) and decreased myocardial blood flow and for evaluating left ventricular ejection. Conducting myocardial nuclear imaging tests in conjunction with exercise or the administration of vasodilating agents such as dipyridamole and adenosine allows clearer identification of how the heart responds to stress and involves only a slight increase in risk.
Client preparation. The nurse informs the client that the tests are relatively noninvasive and that the radiation exposure and risks are minimal. The client is informed that the test involves the IV injection of small amounts of ra-dioisotope. If a dilating agent is to be used, the client is advised to abstain from cigarettes and caffeinated food or drinks for 4 hours before administration of the vasodilator. The client or responsible party must give written consent.
Procedure. The most common tests iuclear cardiology include technetium (99mTc) pyrophosphate scanning, thallium imaging, sestamibi exercise testing and scan, and multigated cardiac blood pool imaging.
TECHNETIUM PYROPHOSPHATE SCANNING. For technetium pyrophosphate scanning, a small dose of 99mTc pyrophosphate is injected into the antecubital vein. The client waits at least 2 hours while the renal system clears the unbound technetium. A gamma-scintillation camera scans the heart to identify the areas of increased uptake of the radioiso-tope. The radioisotope accumulates in damaged myocardial tissue and is referred to as a “hot spot.” This test helps to detect an acute MI and define its location and size, but it does not show an old infarction.
THALLIUM IMAGING. For thallium imaging, a small dose of 2O1T1 is injected into the client’s antecubital vein. A nuclear camera takes images of the heart 10 minutes later to detect areas of normal blood flow and intact cells, which rapidly take up the thallium. Necrotic or ischemic tissue does not take up the radioisotope and appears as “cold spots” on the scan. Scanning is repeated in 2 to 4 hours to evaluate thallium clearance.
Thallium imaging may be performed with the client at rest or during an exercise test. Dipyridamole (Persantine, Apo-Dipyridamole^) is administered before the Persantine thallium test. Dobutamine hydrochloride (Dobutrex) or Adenosine (Adenocard) may be given instead. By causing vasodilation, these drugs simulate the effects of exercise and are used for clients who are unable to exercise on a bike or treadmill. These medications may cause flushing, headache, dyspnea, and chest tightness for a few moments after injection.
Thallium imaging performed during an exercise test may demonstrate perfusion deficits not apparent at rest. First, the stress test procedure is performed. After the client reaches maximum activity level, a small dose of 201Tl is injected intravenously. The client continues to exercise for approximately 1 to 2 minutes, after which the scanning is performed. Nuclear cardiologists often compare the resting and stress images to differentiate between fixed and reversible defects in the myocardium.
Thallium imaging is used to assess myocardial scarring and perfusion, detect the location and extent of an acute or chronic MI, evaluate graft patency after coronary bypass surgery, and evaluate antianginal therapy, thrombolytic therapy, or balloon angioplasty.
CARDIAC BLOOD POOL IMAGING. Cardiac blood pool imaging is a noninvasive test for evaluating cardiac motion and calculating ejection fraction. It uses a computer to synchronize the client’s electrocardiogram (ECG) with pictures taken by a gamma-scintillation camera. The technician attaches the client to an ECG and injects a small amount of 99mTc intravenously. The radioisotope is not taken up by tissue but remains “tagged” to red blood cells in the circulation. The camera may take pictures of the radioactive material as it makes its first pass through the heart.
During multigated blood pool scanning, the computer breaks the time between R waves on the ECG into fractions of a second, called “gates.” The camera records blood flow through the heart during each of these gates. By analyzing the information from multiple gates, the computer can evaluate the ventricular wall motion and calculate ejection fraction (percentage of the left ventricular volume that is ejected with each contraction) and ejection velocity. Areas of decreased, absent, or paradoxical movement of the left ventricle may also be identified.
POSITRON EMISSION TOMOGRAPHY. Positron emission scans are used to compare cardiac perfusion and metabolic function and differentiate normal from diseased myocardium. The technician administers the first radioisotope (nitrogen- 13-ammonia) and then begins a 20-minute scan to detect myocardial perfusion. Next, the technician administers a second radioisotope (fluoro-18-deoxyglucose). After a pause, a second scan is performed to detect the metabolically active myocardium, which is using glucose.
The two scans are compared. In a normal heart, performance and metabolic function will match. In an ischemic heart, there will be a mismatch: a reduction in perfusion and increased glucose uptake by the ischemic myocardium. The scanning procedure takes 2 to 3 hours, and the client may be asked to use a treadmill or exercise bicycle in conjunction with the scan.
Follow-up care. Depending on which test is performed, the client may complain of fatigue or discomfort at the antecubital injection site. If a stress test was paired with the study, the nurse needs to be aware of the same follow-up care as for the stress test.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a noninvasive diagnostic option. An image of the heart or great vessels is produced through the interaction of magnetic fields, radio waves, and atomic nuclei showing hydrogen density. Simply put, the radio waves “bounce off’ the body tissue being examined. Because each tissue has its own density, the computer image clearly differentiates between different types of tissues. MRI permits determination of cardiac wall thickness, chamber dilation, valve and ventricular function, and blood movement in the great vessels. Improved MRI techniques allow coronary artery blood flow to be mapped with nearly the accuracy of a cardiac catheterization.
Before an MRI, the nurse ensures that the client has removed all metallic objects, including watches, jewelry, clothing with metal fasteners, and hair clips. Clients with pacemakers should not undergo an MRI because the magnetic fields can deactivate the pacemaker. Approximately 5% of clients experience claustrophobia during the 15 to 60 minutes required to complete the scan.
Hemodynamic Monitoring
Hemodynamic monitoring is an invasive system used in critical care areas to provide quantitative information about vascular capacity, blood volume, pump effectiveness, and tissue perfusion. Hemodynamic monitoring is often referred to as direct monitoring because it involves procedures that directly measure pressures in the heart and great vessels. This procedure is usually performed for more seriously ill clients and can provide more accurate measurements of blood pressure, heart function, and volume status.
Hemodynamic monitoring does involve significant risks, although complications are uncommon. Therefore informed consent is required. After obtaining consent, the nurse prepares a pressure-monitoring system. The components of this system are a catheter with an infusion system, a transducer, and a monitor. The catheter receives the pressure waves (mechanical energy) from the heart or the great vessels. The transducer converts the mechanical energy into electrical energy, which is displayed as waveforms or numbers on the monitor. The nurse prepares a heparinized solution to maintain the patency of the catheter. This solution is usually infused at 3 to 4 mL/hr under pressure to prevent the back up of blood and occlusion of the catheter.
To prepare the transducer, the nurse must balance and calibrate it according to hospital policy and the manufacturer’s specifications. Finally, the nurse must identify the phlebostatic axis and level the transducer to it. When the monitoring system is prepared, the physician inserts the catheter.
RIGHT ATRIAL, PULMONARY ARTERY, AND PULMONARY WEDGE PRESSURES
A pulmonary artery catheter is a triple- or quadruple-lumen catheter with the capacity to measure right atrial and indirect left atrial pressures or pulmonary artery wedge pressure (PAWP), also known as the pulmonary artery occlusive pressure (PAOP). A cardiac output measurement may also be obtained.
Client preparation. The physician explains the procedure and advises the client and family members or significant others of the risks. The physician then obtains a written consent for the procedure. The client and family should understand that the hemodynamic monitoring system represents an assessment tool. Although it is used to guide therapy, it is not itself a treatment. The nurse asks the client to remain still and in the supine position for insertion of the catheter.
Procedure. The physician inserts a balloon-tipped catheter percutaneously through a large vein and directs it to the right atrium (RA). When the catheter tip reaches the RA, the physician inflates the balloon. The catheter advances with the flow of blood through the tricuspid valve, into the right ventricle, past the pulmonic valve, and into a branch of the pulmonary artery. The balloon is deflated after the catheter tip reaches the pulmonary artery. Waveforms are visualized on the oscilloscope as the pulmonary artery catheter is advanced; fluoroscopy is used to monitor the location of the catheter.
Right atrial pressure is measured by a pressure sensor on the catheter inside the RA. Normal RA pressure ranges from 1 to
Normal pulmonary artery pressure (PAP) ranges from 15 to
Elevated PAWP measurements may indicate left ventricular failure, hypervolemia, mitral regurgitation, or intracardiac shunt. A decreased PAWP is seen with hypovolemia or after-load reduction. Individual values may be less important than the trend in values.
Follow-up care. The patency of the catheter is maintained with infusion of a heparinized solution under pressure. The nurse obtains and records RA pressure, PAP, and PAWP at appropriate intervals (usually every 1 to 4 hours). The trend of these pressures helps to guide medical therapy. During pressure recording, it is important that the transducer be at the level of the phlebostatic axis and that the client’s position be appropriate. The client is usually supine with the head elevated up to 45 degrees or turned slightly to the side while PAWPs are obtained (see the Evidence-Based Practice for Nursing box on p. 652). If the balloon remains in the wedge position after PAWP measurement, the nurse attempts to change the catheter’s position by asking the client to cough or by changing the client’s position. If these methods are not successful, the nurse notifies the physician immediately.
The nurse changes the occlusive dressing over the catheter aseptically according to hospital policy. The insertion site is inspected for redness, heat, swelling, drainage, and intactness of the sutures. Detailed discussion of the management and care of clients with pulmonary artery catheters can be found in textbooks on critical care nursing.
The nurse assesses for a number of complications associated with pulmonary artery catheters. For example, pulmonary infarction or pulmonary rupture may occur if the catheter remains in the wedge position. Air embolism is possible if the balloon has ruptured and repeated attempts are made to inflate it. Ventricular dysrhythmias may occur if the catheter tip slips back into the right ventricle and irritates the myocardium. Thrombus and embolus formation may occur at the catheter site. Infection may result and bleeding may be pronounced if the infusion system becomes disconnected.
CARDIAC OUTPUT
Cardiac output can be measured using the thermodilution method when the client has a pulmonary artery catheter with a thermistor. The nurse injects a specified amount (5 or 10 mL) of iced or room-temperature IV solution (normal saline or dextrose in water) into the proximal port of the catheter. The solution mixes with the blood in the right atrium and travels with the flow of blood through the heart. A temperature-sensitive device located on the tip of the catheter in the pulmonary artery registers and senses the change in blood temperature. This information is transmitted to a cardiac output computer, which displays a digital value.
MIXED VENOUS OXYGEN SATURATION MONITORING
Mixed venous oxygen saturation (Svo2) reflects the balance between the client’s oxygen supply and demand. Svo2 may be measured with a pulmonary artery catheter with fiberoptics. Light travels down one optical fiber, is reflected by the red blood cells according to the oxygen saturation of the hemoglobin, and returns to an optical module for interpretation and continuous display. The normal range for Svo2 is 60% to 80%. Using Svo2 monitoring, the nurse can individualize the plan of care so the Svo2 remains in the normal range and the client’s oxygen supply and demand are in balance.
CENTRAL VENOUS PRESSURE MONITORING
If the health care provider wants to measure pressures from the right atrium or central veins but a pulmonary artery catheter and pressure-monitoring system are not appropriate pressures may be obtained with a water manometer attached to a conventional IV system. Central venous pressures (CVPs) are similar to right atrial pressures, but CVPs are measured in centimeters of water rather than in millimeters of mercury. A normal CVP is 3 to
The physician inserts a catheter through the venous system into the right atrium. A chest x-ray film is obtained to assess placement. The nurse levels the manometer with the phlebostatic axis to ensure accurate pressure measurement.
Elevated CVPs may indicate right ventricular failure. Low CVPs may indicate hypovolemia. Caution must be used in predicting the function of the left side of the heart from a CVP reading.
Care of the site is similar to that for the pulmonary artery catheter site. Complications include pneumothorax during insertion, hemorrhage, infection, and catheter occlusion.
SYSTEMIC INTRA-ARTERIAL MONITORING
Direct measurement of arterial blood pressure is by invasive arterial catheter in critically ill clients. The physician usually inserts an intra-arterial catheter into the radial artery, but the femoral, brachial, or dorsalis pedis arteries may also be used. After the physician has inserted the catheter, it is attached to pressure tubing.
A heparinized solution is infused constantly under pressure to maintain the integrity of the system. A transducer attached to the tubing allows continuous direct monitoring of the arterial blood pressure. Direct measurements of blood pressure are usually 10 to
Because the arterial vasculature is a high-pressure system, frequent assessment of the arterial site and infusion system is essential. The nurse notes any bleeding around the intra-arterial catheter or any loose connections and corrects the situation immediately. Collateral circulation is assessed by Doppler or Allen’s tests before and while the arterial catheter is in place. Color, pulse, and temperature at the insertion site should be scrupulously monitored for any early signs of circulatory compromise. Complications of systemic intra-arterial monitoring may include pain, infection, arteriospasm, or obstruction at the site with the potential for distal infarction, air embolism, and hemorrhage.
IMPEDANCE CARDIOGRAPHY
Unlike conventional hemodynamic monitoring, impedance cartography (ICG) is a noninvasive monitoring system that consists of four ICG electrodes, four electrocardiogram (ECG) electrodes, and a portable ICG monitor. Simply stated, it measures the total impedance (resistance) to the flow of electricity in the heart. ICG can be used in any setting, including the home. It provides measures of thoracic fluid, left ventricular function (cardiac output and cardiac index), preload, afterload, and contractility of the heart (Turner, 2000).
