The detection of
coronary artery spasm, which can play an important role in spontaneous
angina pectoris, may be particularly important with respect to therapeutic considerations. Since the documentation of spontaneous
spasm is a rare occurrence, provocation of
spasm under controlled conditions can facilitate the diagnosis. In our laboratory, the provocation test is carried out according to a standard protocol with the use of a bolus injection of 0.4 mg
methergine ( a close congener of
ergonovine). The 321 patients studied since 1976 were distributed into five groups: none of 99 patients with atypical
chest pain had
spasm; only one of 42 patients with typical
angina pectoris of effort had
spasm;
spasm was induced in 48 of 104 patients with spontaneous
angina pectoris, 41 of whom had
Prinzmetal's variant angina with 39 of the latter demonstrating
spasm; seven of 52 patients with angina both at rest and of effort displayed
spasm; and two of 24 patients with
myocardial infarction and normal coronary arteries were found to have
methergine-induced
spasm. The risk of serious complications (such as arrhythmias) is very low provided that an induced
spasm is immediately relieved by intracoronary injection of
nitroglycerin. Measurement of coronary sinus blood flow indicates that the mechanism is primarily that of an increase in vascular resistance due to
spasm and not an increase in myocardial
oxygen demands. Thus, the provocation test is useful and indicated for patients with isolated spontaneous
angina pectoris, especially those with Prinzmental's variant angina, patients with angina both at rest and of effort and in patients with myocardial infarcation and normal or nearly-normal coronary arteries.