Chapter 26 .pdf

Chapter 26 Assessment of Cardiovascular Function Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Overview of Anatomy and Physiology - Heart Three layers – Endocardium – Myocardium – Epicardium Four chambers...

Chapter 26 Assessment of Cardiovascular Function Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Overview of Anatomy and Physiology - Heart Three layers – Endocardium – Myocardium – Epicardium Four chambers Heart valves Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Overview of Anatomy and Physiology – Heart (cont’d) Coronary arteries Cardiac conduction system Loading… The cardiac conduction system generates and transmits electrical impulses that stimulate contraction of the myocardium. Both the sinoatrial (SA) node (the primary pacemaker of the heart) and the atrioventricular (AV) node (the secondary pacemaker of the heart). Initially, the impulse is conducted through a bundle of specialized conducting tissue, referred to as the bundle of His, which then divides into the right bundle branch and left bundle branch. Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Impulses travel through the bundle branches to reach the terminal point in the conduction system, called the Purkinje fibers. These fibers are composed of Purkinje cells that rapidly conduct impulses throughout the thick walls of the ventricles. This action stimulates the ventricular myocardial cells to contract. Cardiac hemodynamics Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Structure of the Heart Loading… Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Cardiac Conduction System Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  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 Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Cardiac Action Potential Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Great Vessel and Heart Chamber Pressures Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Loading… Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  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 Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Assessment Health history – Demographic information – Family/genetic history – Cultural/social factors Risk factors – Modifiable – Nonmodifiable Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Most Common Clinical Manifestations Chest pain Dyspnea Peripheral edema, weight gain Fatigue Dizziness, syncope, changes in level of consciousness Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Assessment Medications Self-perception, self- concept Nutrition Roles, relationships Elimination Sexuality, reproduction Activity, exercise Coping, stress tolerance Sleep, rest Prevention strategies Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Laboratory Tests Cardiac biomarkers CK, CK-MB Myoglobin Troponin T and I Lipid profile Brain (B-type) natriuretic peptide C-reactive protein Homocysteine Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Electrocardiography 12 lead ECG Continuous monitoring: hardwire, telemetry Continuous ECG monitoring is the standard of care for patients who are at high risk for dysrhythmias. This form of cardiac monitoring detects abnormalities in heart rate and rhythm. Signal-averaged electrocardiogram Continuous ambulatory monitoring form of continuous or intermittent ECG home monitoring. Transtelephonic monitoring Wireless mobile monitoring Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Electrocardiography (cont’d) Cardiac stress testing – Exercise stress testing - Pharmacologic stress testing- Patients who are cognitively impaired and unable to follow directions or physically disabled or deconditioned will not be able to achieve their target heart rate by exercising on a treadmill or bicycleVasodilating agents such as dipyridamole (Persantine), adenosine (Adenocard), or regadenoson (Lexiscan) given as an IV infusion are used to mimic the effects of exercise by maximally dilating normal coronary arteries. The side effects of these agents are related to the vasodilating action and include chest pain, headache, flushing, nausea, heart block and dyspnea Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Diagnostic Tests Radionuclide imaging When radioisotopes are injected into the bloodstream, the energy emitted can be detected by a gamma scintillation camera positioned over the body. These radioisotopes are called tracers – Myocardial perfusion imaging – Test of ventricular function, wall motion - Computed tomography - Cardiac CT scanning is a form of cardiac imaging that uses x-rays to provide accurate cross-sectional “virtual” slices of specific areas of the heart and surrounding structures. Complex mathematical and computer algorithms are used to analyze the slices to create three-dimensional images. Multidetector CT (MDCT) is a fast form of CT scanning that takes multiple slices at the same time. Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Positron emission tomography- During PET, tracers are given by injection; one compound is used to determine blood flow in the myocardium, and another determines the metabolic function. The PET camera provides detailed three-dimensional images of the distributed compounds. Magnetic resonance angiography- MRA is a noninvasive, painless technique that is used to examine both the physiologic and anatomic properties of the heart. MRA uses a powerful magnetic field and computer-generated pictures to image the heart and great vessels. It is valuable in diagnosing diseases of the aorta, heart muscle, and pericardium, as well as congenital heart lesions. Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Hemodynamic Monitoring CVP-CVP is a measurement of the pressure in the vena cava or right atrium. The preferred site is the subclavian vein,.A local anesthetic agent is used. During this sterile procedure, the physician threads a single-lumen or millilumen catheter through the vein into the vena cava just above or within the right atrium. Once the CVP catheter is inserted, it is secured and a dry sterile dressing is applied. Position of the catheter is confirmed by a chest x-ray. The normal CVP is 2 to 6 mm Hg Pulmonary artery pressure Intra-arterial BP monitoring-Arterial catheters are also useful when arterial blood gas measurements and blood samples need to be obtained frequently.The radial artery is the usual site selected Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Phlebostatic Level Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Pulmonary Artery Pressure Monitoring Pulmonary artery pressure monitoring is used in critical care for assessing left ventricular function, diagnosing the etiology of shock, and evaluating the patient’s response to medical interventions (e.g., fluid administration, vasoactive medications). A pulmonary artery catheter and a pressure monitoring system are used Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Pulmonary Artery Catheter and Pressure Monitoring System Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins  Reference; Kindly consult your course book Brunner and Siddharth, The medical and surgical nursing, 14th Edition; 2018 p.no.1860-1945 for more details and exams preparation. Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins