Lect 15 CAD and Acute myocardial Infarction

Ischemic Heart Disease

"Reduction of blood flow to heart tissue"

that obstructs oxygen and metabolites/nutrients

Determinants of Demand

HR, Myocardial contractility, myocardial wall tension (stress)

Determinants of Demand: HR

Each heartbeat is a contraction, using ATP and oxygen

Determinants of Demand: Myocardial contratility

The more filaments involved, the more ATP and oxygen needed

Determinants of Demand: Myocardial wall tension

Afterload determines the force the heart muscle must generate

Supply Requirements are determined by:

Inspired level of oxygen, Pulmonary function, Adequate coronary blood flow

Ischemic Heart Disease - Structural

atherosclerosis of coronary arteries (CAD)

Blocked Plumbing

Limits appropriate increases in perfusion when the demand for flow is augmented

Ischemic Heart Disease - functional

reduction in O2-carrying capacity, causing anemia or carboxyhemoglobin

Angina Pectoris

"strangling in chest"- Paroxysmal and usually recurrent attacks of substernal or precordial chest discomfort, usually caused by transient (15sec to 3min) myocardial ischemia

Angina Pectoris- Stable/Typical

predictable, most common, sudden; Caused by imbalance in coronary perfusion relative to demand

Angina Pectoris- Unstable/Crescendo

Worse, increasingly frequent pain, often of prolonged duration; caused by disruption of atherosclerotic plaque; Warning of imminent AMI

Angina Pectoris- Prinzmetal variant

uncommon, Coronary artery vasospasm

Myocardial Infarction- Pathogenesis of Blocked Plumbing

Intraplaque hemorrhage, erosion/ulceration, rupture/fissure of atheromatous plaque; Platelets adhere to collagen/plaque an activate to release and aggregate granule contents

Normal ->

ischemia -> injury -> infarction