Chapter 25 Assessment of Cardiovascular Function

Overview of Anatomy and Physiology Three layers: endocardium, myocardium, epicardium Four chambers: Right atrium and ventricle, left atrium and ventricle Atrioventricular valves: tricuspid and mitral Semilunar valves: aortic and pulmonic Coronary arteries Cardiac conduction system (electrophysiology) Cardiac hemodynamics

Anatomy of the Heart Figure 25-1

Greater Vessels, Heart Chambers and Pressures Figure 25-2

Cardiac Conduction System: Electrophysiology (60-100) (40-60) (30-40) (30-40) Figure 25-3

Question Which of the following is the primary pacemaker for the myocardium? Atrioventricular junction Bundle of His Purkinje fibers Sinoatrial node

Answer Sinoatrial node Rationale: The sinoatrial node is the primary pacemaker for the myocardium

Cardiac Action Potential Depolarization: electrical activation of cell caused by influx of sodium into cell while potassium exits cell Repolarization: return of cell to resting state caused by reentry of potassium into cell while sodium exits Refractory periods Effective refractory period: phase in which cells are incapable of depolarizing Relative refractory period: phase in which cells require stronger-than-normal stimulus to depolarize

Cardiac Action Potential Cycle Figure 25-4

Cardiac Cycle Refers to the events that occur in the heart from the beginning of one heartbeat to the next Number of cycles depends on heart rate Each cycle has three major sequential events: Diastole Atrial systole Ventricular systole

Cardiac Output Stroke volume(SV): amount of blood ejected with each heartbeat Preload: degree of stretch of cardiac muscle fibers at end of diastole Afterload: resistance to ejection of blood from ventricle Contractility: ability of cardiac muscle to shorten in response to electrical impulse

Cardiac Output (cont.) Ejection fraction: percent of end diastolic volume ejected with each heart beat (left ventricle) Cardiac output (CO): amount of blood pumped by ventricle in liters per minute CO = SV × HR

Influencing Factors Control of heart rate Autonomic nervous system, baroreceptors Control of stroke volume Preload: Frank–Starling Law Afterload: affected by systemic vascular resistance, pulmonary vascular resistance

Contractility Contractility increased by catecholamines, SNS, certain medications Increased contractility results in increased stroke volume Decreased by hypoxemia, acidosis, certain medications

Question Which of the following best defines stroke volume? The amount of blood ejected with each heartbeat Amount of blood pumped by the ventricle in liters per minute Degree of stretch of the cardiac muscle fibers at the end of diastole Ability of the cardiac muscle to shorten in response to an electrical impulse

Answer The amount of blood ejected with each heartbeat Rationale: Stroke volume is the amount of blood ejected with each heartbeat. Cardiac output is the amount of blood pumped by the ventricle in liters per minute. Preload is the degree of stretch of the cardiac muscle fibers at the end of diastole. Contractility is the ability of the cardiac muscle to shorten in response to an electrical impulse

Assessment of the CV Health history Demographic information Family/genetic history Cultural/social factors Risk factors Modifiable Nonmodifiable

Assessment of the CV System Health history Common symptoms Chest pain/discomfort Pain/discomfort in other areas of the upper body SOB/dyspnea Peripheral edema, wt gain, abd distention Palpitations Unusual fatigue, dizziness, syncope, change in LOC

Past Health, Family, and Social History Medications Nutrition Elimination Activity, exercise Sleep, rest Self-perception/self-concept Roles and relationships Coping and stress

Physical Assessment of CV System General appearance Skin and extremities Pulse pressure Blood pressure; orthostatic changes Arterial pulses Jugular venous pulsations Heart inspection, palpation, auscultation Assessment of other systems

Laboratory Tests Cardiac biomarkers Blood chemistry, hematology, coagulation Lipid profile Brain (B-type) natriuretic peptide C-reactive protein Homocysteine Refer to Table 25-4

Electrocardiography 12-lead ECG Continuous monitoring Hardwire Telemetry Lead systems Ambulatory monitoring

Cardiac Stress Testing Exercise stress test Pt walks on treadmill with intensity progressing according to protocols ECG, V/S, symptoms monitored Terminated when target HR is achieved Pharmacologic stress testing Vasodilating agents given to mimic exercise

Diagnostic Tests Radionuclide imaging: Myocardial perfusion imaging Positron emission tomography Test of ventricular function, wall motion Computed tomography Magnetic resonance angiography

Echocardiography Noninvasive ultrasound test that is used to: Measure the ejection fraction Examine the size, shape, and motion of cardiac structures Transthoracic Transesophageal

Cardiac Catheterization Invasive procedure used to diagnose structural and functional diseases of the heart and great vessels Right Heart Cath Pulmonary artery pressure and oxygen saturations may be obtained; biopsy of myocardial tissue may be obtained Left Heart Cath Involves use of contrast agent

Nursing Interventions-Cardiac Cath Observe cath site for bleeding, hematoma Assess peripheral pulses Evaluate temp, color, and cap refill of affected extremity Screen for dysrhythmias Maintain bed rest 2 to 6 hours Instruct patient to report chest pain, bleeding Monitor for contrast-induced nephropathy Ensure patient safety

Hemodynamic Monitoring Central venous pressure Pulmonary artery pressure Intra-arterial B/P monitoring Minimally invasive cardiac output monitoring devices

Pulmonary Artery Catheter and Pressure Monitoring System Figure 25-12