Clinical studies of patients with coronary spasm.

Coronary artery spasm may cause myocardial ischemia in patients without severe coronary atherosclerotic obstruction. Spontaneous rest angina, particularly at night, is the predominant symptom; most patients are smokers. Ergonovine tests have high sensitivity and specificity for the diagnosis of coronary spasm, but should be used when vasospasm is suspected but no electrocardiogram was recorded during spontaneous angina. Arterial constriction measured during ergonovine testing suggests that the arterial hypersensitivity to vasoconstrictors at sites of atherosclerotic lesions is independent of the severity of the lesion. Coronary vasospasm may also be provoked by exercise, possibly through an alpha-adrenergic mechanism. Both spontaneous and exercise-induced attacks of vasospasm are prevented by calcium-antagonist drugs that remain effective during longer-term treatment. The cyclic nature of the condition is demonstrated when successful therapy is discontinued without recurrence of symptoms and may be due to alteration of arterial hypersensitivity.