Role of coronary vasospasm in the pathogenesis of myocardial ischemia and angina pectoris.

Spasm, either of heart muscle or of coronary arteries, has long been postulated as a possible cause of anginal pain. Yet early necropsy observations of obstructed coronary arteries in cases of cardiac death so focused attention on the fixed obstruction as the source of myocardial ischemia that the role of vasospasm is only now becoming evident. Further, the fact that spasm most commonly occurs together with a fixed obstruction has obscured its presence and its role in producing myocardial ischemia. In classic angina, ischemia results when increased oxygen demand is placed on the heart; the variant form of angina results from a restriction in myocardial oxygen supply, frequently even at rest. The mechanisms of coronary vasospasm are unclear, although such factors as excessive alpha-adrenergic activity, imbalances in prostaglandin synthesis, and increased Ca++ entry into myocytes through alterations in pH and blood gas tensions have been implicated.