3The 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.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 oxygen needs of the peripheral tissues
4RIGHT SIDEThe 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 25 mm Hg) to close the tricuspid valve, open the pulmonic valve, and propel blood into the pulmonary artery and the lungs. The workload of the right ventricle is light compared with that of the left ventricle because the pulmonary system is a low-pressure system, which imposes less resistance to flow
5LEFT SIDEAfter 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 120 mm Hg) to close the mitral valve and open the aortic valve. Blood is propelled into the aorta and into the systemic arterial circulation
6Blood 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 120 mm Hg, whereas the pressure of blood in the right atrium averages about 0 to 5 mm Hg. These differences in pressure produce a pressure gradient, with blood flowing from an area of higher pressure to an area of lower pressure.The heart and vascular structures are responsible for maintaining these pressures
8ATRIOVENTRICULAR 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 ventricleDuring 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 (regurgitation) of blood into the atria
9SEMILUNAR VALVESThere 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
11LEFT CORONARY ARTERYThe 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
12RIGHT CORONARY ARTERYThe 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
14The 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 muscleAn 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.
15The 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 Purkinje 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
16Mechanical 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
17CARDIAC 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
18HEART RATEHeart 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 when necessary 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
19STROKE VOLUMEStroke volume is the amount of blood ejected by the left ventricle during each systole. Several variables influence stroke volume and, ultimately, CO.These variables include heart rate, preload, afterload, and contractility
20PRELOADPreload 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
21AFTERLOAD.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
22CONTRACTILITYContractility 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
25Blood pressure = Cardiac output x Peripheral vascular resistance Blood pressure is the force of blood exerted against the vessel walls.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 resistanceSentence and phrases
26Blood Pressure Regulation Autonomic nervous systemBaroreceptorsChemoreceptorsRenal systemEndocrine systemExternal factors also affect BP
27Venous SystemStructure: a series of veins located adjacent to the arterial systemFunction: completes the circulation of blood by returning blood from the capillaries to the right side of the heartCardiovascular changes in the older adult: only evident when the person is active or under stress
28Assessment Techniques HistoryDemographic dataFamily history and genetic riskPersonal historyDiet historySocioeconomic status
30Pain or DiscomfortPain or discomfort can result from ischemic heart disease, pericarditis, and aortic dissection.Chest pain can also result from noncardiac conditions such as pleurisy, pulmonary embolus, hiatal hernia, and anxiety.(Continued)
31Pain or Discomfort (Continued) Terms such as discomfort, heaviness, pressure, indigestion, aching, choking, strangling, tingling, squeezing, constricting, or vise-like are all used to describe pain.Women often do not experience pain in the chest but rather feelings of discomfort or indigestion.
32Pain Assessment Onset Manner of onset Duration Frequency Precipitating factorsLocationRadiation(Continued)
33Pain Assessment (Continued) QualityIntensity, which can be graded from 0 to 10, associated symptoms, aggravating factors, and relieving factors
34Dyspnea Can occur as a result of both cardiac and pulmonary disease Difficult or labored breathing experienced as uncomfortable breathing or shortness of breathDyspnea on exertion (DOE)Orthopnea: dyspnea when lying flatParoxysmal nocturnal dyspnea after lying down for several hours
35Other Manifestations Fatigue Palpitations Weight gain Syncope Extremity pain
36Physical Assessment 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 malnoutrished, 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
37Physical Assessment Integumentary system 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 conjunctival mucous membranesA 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
38Physical AssessmentCentral 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 desaturation 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
39Physical Assessment 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
40Physical Assessment 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
42Physical Assessment Blood pressure Normal blood pressure in adults older than 45 years of age ranges from 90 to 140 mm Hg for systolic pressure and from 60 to 90 mm Hg for diastolic pressure.A blood pressure that exceeds 135/85 mm Hg increases the workload of the left ventricle and oxygen consumption.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
43Physical AssessmentVenous and arterial pulses: central and jugular venous pressures, and jugular venous distentionThe 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
47Normal heart soundsThe first heart sound (S1) 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. S1 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.
48Normal heart soundsThe 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 often not heard.Normal splitting of S2 occurs because of the longer systolic phase of the right ventricle. Splitting of S1 and S2 can be accentuated by inspiration (increased venous return), and it narrows during expiration.
49Abnormal 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.
50Abnormal heart sounds GALLOPS AND MURMURS. 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.
51Abnormal heart soundsThe 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.
52Abnormal heart soundsMURMURS. 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 S1 and S2, whereas diastolic murmurs (e.g., mitral stenosis and aortic regurgitation) occur between S2 and S1.Murmurs can occur during presystole, midsystole, or late systole or di- astole 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.
54Abnormal heart soundsPERICARDIAL 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.
58Other Diagnostic Tests ElectrocardiographyThe 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.
60Electrocardiography 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.
64Electrocardiography 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.
67Hemodynamic Monitoring Invasive system used in critical care areas to provide quantitative information about vascular capacity, blood volume, pump effectiveness, and tissue perfusionPulmonary artery catheterSystemic intra-arterial monitoringImpedance cardiography