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.     

Differentiation between right and circumflex coronary artery disease on thallium myocardial perfusion scanning

Thallium defects in the inferior and lateral walls of the heart were correlated with right and circumflex coronary artery disease (CAD) in 405 patients who underwent coronary arteriography. In the 102 patients with either single right or left circumflex (LC) CAD, inferior segment defects (anterior view) were associated with right CAD, and both lateral segment defects (40 ° left anterior oblique view) and posteroinferior defects (60 ° left anterior oblique view) were associated with LC CAD. In all 405 patients, inferior segment defects had a sensitivity of 65%, a specificity of 92%, and a predictive accuracy of 89% for right CAD, and lateral segment defects had a sensitivity of 52%, a specificity of 96%, and a predictive accuracy of 90% for LC CAD. Posteroinferior defects had a low predictive accuracy for narrowing in either artery. The presence or absence of concomitant anterior defects did not alter these results. Narrowing in both right and LC coronary arteries was best identified by a combination of inferior and lateral segment defects (sensitivity 30%, specificity 96%, predictive accuracy 72% ). Narrowing in only 1 of these 2 arteries was best identified by a combination of inferior segment without lateral segment defects for right CAD (sensitivity 63%, specificity 86%, predictive accuracy 55%) and lateral segment without inferior segment defects for LC CAD (sensitivity 45%, specificity 92%, predictive accuracy 57%). Thallium scanning identifies significant narrowing in the right and LC coronary arteries, and these may be separated by the pattern of defects.