Chapter 25 Assessment of Cardiovascular Function Overview of

Chapter 25 Assessment of Cardiovascular Function

Overview of Anatomy and Physiology • Three layers: endocardium, myocardium, epicardium • Semilunar valves: aortic and pulmonic • Four chambers: Right atrium and ventricle, left atrium and ventricle • Cardiac conduction system (electrophysiology) • Atrioventricular valves: tricuspid and mitral • Coronary arteries • Cardiac hemodynamics Copyright © 2018 Wolters Kluwer · All Rights Reserved

Anatomy of the Heart Figure 25 -1 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Greater Vessels, Heart Chambers and Pressures Figure 25 -2 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Cardiac Conduction System: Electrophysiology (60 -100) (40 -60) (30 -40) Figure 25 -3 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Question Which of the following is the primary pacemaker for the myocardium? A. Atrioventricular junction B. Bundle of His C. Purkinje fibers D. Sinoatrial node Copyright © 2018 Wolters Kluwer · All Rights Reserved

Answer D. Sinoatrial node Rationale: The sinoatrial node is the primary pacemaker for the myocardium Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Cardiac Action Potential Cycle Figure 25 -4 Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Contractility – Contractility increased by catecholamines, SNS, certain medications – Increased contractility results in increased stroke volume – Decreased by hypoxemia, acidosis, certain medications Copyright © 2018 Wolters Kluwer · All Rights Reserved

Question Which of the following best defines stroke volume? A. The amount of blood ejected with each heartbeat B. Amount of blood pumped by the ventricle in liters per minute C. Degree of stretch of the cardiac muscle fibers at the end of diastole D. Ability of the cardiac muscle to shorten in response to an electrical impulse Copyright © 2018 Wolters Kluwer · All Rights Reserved

Answer A. 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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Assessment of the CV • Health history • Demographic information • Family/genetic history • Cultural/social factors • Risk factors – Modifiable – Nonmodifiable Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Past Health, Family, and Social History • Medications • Nutrition • Elimination • Activity, exercise • Sleep, rest • Self-perception/self-concept • Roles and relationships • Coping and stress Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Laboratory Tests • Cardiac biomarkers • Blood chemistry, hematology, coagulation • Lipid profile • Brain (B-type) natriuretic peptide • C-reactive protein • Homocysteine • Refer to Table 25 -4 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Electrocardiography • 12 -lead ECG • Continuous monitoring – Hardwire – Telemetry – Lead systems – Ambulatory monitoring Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Diagnostic Tests • Radionuclide imaging: – Myocardial perfusion imaging – Positron emission tomography – Test of ventricular function, wall motion – Computed tomography – Magnetic resonance angiography Copyright © 2018 Wolters Kluwer · All Rights Reserved

Echocardiography • Noninvasive ultrasound test that is used to: – Measure the ejection fraction – Examine the size, shape, and motion of cardiac structures • Transthoracic • Transesophageal Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

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 Copyright © 2018 Wolters Kluwer · All Rights Reserved

Hemodynamic Monitoring • Central venous pressure • Pulmonary artery pressure • Intra-arterial B/P monitoring • Minimally invasive cardiac output monitoring devices Copyright © 2018 Wolters Kluwer · All Rights Reserved

Pulmonary Artery Catheter and Pressure Monitoring System Figure 25 -12 Copyright © 2018 Wolters Kluwer · All Rights Reserved