What is Ischemic Heart Disease?

Ischemic heart disease is caused by an imbalance between the myocardial blood flow and the metabolic demand of the myocardium. Reduction in coronary blood flow is related to progressive atherosclerosis with increasing occlusion of coronary arteries. Blood flow can be further decreased by superimposed events such as vasospasm, thrombosis, or circulatory changes leading to hypoperfusion. (Anversa and Sonnenblick, 1990)

Coronary artery perfusion depends upon the pressure differential between the ostia (aortic diastolic pressure) and coronary sinus (right atrial pressure). Coronary blood flow is reduced during systole because of Venturi effects at the coronary orifices and compression of intramuscular arteries during ventricular contraction.

Factors reducing coronary blood flow include:

Decreased aortic diastolic pressure

Increased intraventricular pressure and myocardial contraction

Coronary artery stenosis, which can be further subdivided into the following etiologies:

Fixed coronary stenosis

Acute plaque change (rupture, hemorrhage)

Coronary artery thrombosis

Vasoconstriction

Aortic valve stenosis and regurgitation

Increased right atrial pressure

40 micron collateral vessels are present in all hearts with pressure gradients permitting flow, despite occlusion of major vessels. In general, the cross-sectional area of the coronary artery lumen must be reduced by more than 75% to significantly affect