Chapter 26 Assessment of Cardiovascular Function

Overview of Anatomy and Physiology - Heart Three layers Endocardium Myocardium Epicardium Four chambers Heart valves

Overview of Anatomy and Physiology – Heart (cont’d) Coronary arteries Cardiac conduction system Cardiac hemodynamics

Structure of the Heart

Cardiac Conduction System

Terms - 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 re-entry 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

Great Vessel and Heart Chamber Pressures

Terms - Cardiac Output Stroke volume: amount of blood ejected with each heartbeat Cardiac output: amount of blood pumped by ventricle in liters per minute Preload: degree of stretch of cardiac muscle fibers at end of diastole Contractility: ability of cardiac muscle to shorten in response to electrical impulse

Terms - Cardiac Output (cont’d) After load: resistance to ejection of blood from ventricle Ejection fraction: percent of end diastolic volume ejected with each heart beat

CO = SV x HR Control of heart rate Autonomic nervous system, baroreceptors Control of strike volume Preload: Frank-Starling Law After load: affected by systemic vascular resistance, pulmonary vascular resistance Contractility increased by catecholamines, SNS, some medications Decreased by hypoxemia, acidosis, some medications

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

Answer D. Sinoatrial node Rationale: The sinoatrial node is the normal pacemaker for the myocardium.

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 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.

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

Most Common Clinical Manifestations Chest pain Dyspnea Peripheral edema, weight gain Fatigue Dizziness, syncope, changes in level of consciousness

Assessment Medications Nutrition Elimination Activity, exercise Sleep, rest Self-perception, self- concept Roles, relationships Sexuality, reproduction Coping, stress tolerance Prevention strategies

Health Promotion, Perception, and Management Questions Ask regarding health promotion, preventive practices What type of health issues do you have? Are you able to identify any family history or behaviors that put you at risk of this health problem? What are your risk factors for heart disease? What do you do to stay healthy? How is your health? Have you noticed any changes?

Health Promotion, Perception, and Management Questions (cont’d) Ask regarding health promotion, preventive practices Do you have a cardiologist or primary health care provider? How often do you go for check-ups? Do you use tobacco or alcohol? What medications do you take?

Question Where does the nurse auscultate the apex of the heart? Erb’s point Fifth intercoastal space Pulmonic area Tricuspid area

Answer B. Fifth intercoastal space Rationale: The nurse auscultates the apex of the heart at the fifth intercoastal space.

Laboratory Tests Cardiac biomarkers CK, CK-MB Myoglobin Troponin T and I Lipid profile Brain (B-type) natriuretic peptide C-reactive protein Homocysteine

Electrocardiography 12 lead ECG Continuous monitoring: hardwire, telemetry Signal-averaged electrocardiogram Continuous ambulatory monitoring Transtelephonic monitoring Wireless mobile monitoring

Electrocardiography (cont’d) Cardiac stress testing Exercise stress testing Pharmacologic stress testing

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

Cardiac Catherization Invasive procedure study used to measure cardiac chamber pressures, assess patency of coronary arteries Requires ECG, hemodynamic monitoring; emergency equipment must be available Assessment prior to test; allergies, blood work Assessment of patient postprocedure; circulation, potential for bleeding, potential for dysrhythmias Activity restrictions Patient education pre-, postprocedure

Hemodynamic Monitoring CVP Pulmonary artery pressure Intra-arterial BP monitoring

Phlebostatic Level

Pulmonary Artery Catheter Refer to fig. 26-11

Pulmonary Artery Catheter and Pressure Monitoring System