CAD Pathophysiology2 [Compatibility Mode]

CAD Pathophysiology2 [Compatibility Mode] - Pathophysiology...

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Unformatted text preview: Pathophysiology of Ischemic Heart Disease Etiology of Ischemic Heart Disease Heart rate Afterload Preload Contractility Demand Supply Coronary Artery O2 extraction Diastolic filling time Ischemic Heart Disease Coronary Coronary artery disease – leading cause of death in industrialized countries – type of ischemic heart disease – Leads to angina, myocardial infarction, sudden cardiac death, and chronic heart failure death and chronic heart failure Causes Causes – Modifiable and non-modifiable risk factors non– Arteriosclerosis – natural changes in the intima, connective tissue, and diameter of artery – Atherosclerosis – pathologic phenomenon occurring in the coronary, carotid, iliac, and femoral arteries as well as the aorta (coronary artery disease) 1 Normal Coronary Artery endothelium Intima lumen Media Adventia This is a normal coronary artery. The lumen is large, without any narrowing by atheromatous plaque. The muscular arterial wall is of normal proportion. How atherosclerosis develops (www.merck.com) (www.merck.com) 2 The atherosclerotic process Response to Injury hypothesis - inflammatory response resulting in proliferation of tissue within the arterial wall which may result in obstruction of blood flow Causes: -elevated levels of cholesterol and triglyceride in the blood, -high blood pressure – turbulent blood flow -tobacco smoke -glycosylated substances Response to Injury Hypothesis (pg. 52(pg. 52-55, Brubaker text) 1. 2. 2. 3. 4. 5. 6. Injury to endothelium causing to platelets adhere to endothelium Release of growth factors (mitogenic and chematotactic effects) Monocytes attach to endothelium and penetrate (also LDL receptor activation) monocytes become macrophages and receptor activation) – monocytes become macrophages and take take up LDL and SMC’s Smooth muscle cell proliferation and migrate from medial to intimal layer Foam cells are formed - migration to the intima smooth muscles with lipids form fatty streaks Fibromuscular plaque – fibromuscular layer with cholesterol core pg 53, Brubaker, 3 Atherosclerotic Plaque Blocked Coronary Artery 4 Ischemic Heart Disease A result of CAD (atherosclerosis) result Imbalance Imbalance between supply and demand Narrowing Narrowing and hardening of the arteries leads to imbalance between the supply and demand of blood for cardiac muscle Ischemia blood for cardiac muscle = Ischemia Ischemia Ischemia is either detected by a symptom (angina) or indirectly by electrocardiogram and other non-invasive and invasive nondiagnostic techniques Classic symptoms of IHD: Angina pectoris – Angina pectoris – transient, referred cardiac pain resulting from myocardial ischemia Usually Usually in substernal region, jaw, neck, or arms, may also be in epigastrum and interscapular may also be in epigastrum and interscapular regions regions Symptomology Symptomology – pressure, heaviness, fullness, squeezing, burning, aching, choking, or even dyspnea Types of Angina and Associated Pathophysiology Typical Typical Angina – evoked by exertion, emotions, cold/heat exposure, meals, and sexual intercourse; relieved by rest or nitroglycerin relieved by rest or nitroglycerin – Stable Angina – reproducible and predictable in onset Atypical Atypical Angina – no relationship to exertion – Unstable Angina – new onset of typical angina, increasing in intensity or occurs at rest – Variant (Prinzmetal’s angina) - 5 IHD: Demand > Supply An An ischemic state may result in one or more of the following symptoms or conditions – Angina – Myocardial infarction (heart attack) – Silent Ischemia Asymptomatic Asymptomatic episodes of myocardial ischemia in those with CAD Dx – Syndrome X Symptoms Symptoms of angina pectoris with no evidence of significant atherosclerosis. May May be due to problems in smallest of coronary arteries that are not visualized by angiographic techniques 6 ...
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