A NEW NONINVASIVE METHOD OF DIAGNOSING VASOSPASTIC ANGINA BASED ON DILATION RESPONSE OF THE LEFT MAIN CORONARY-ARTERY TO NITROGLYCERIN AS MEASURED BY ECHOCARDIOGRAPHY

Objectives. The purpose of the present study was to evaluate the feasi bility of diagnosing vasospastic angina based on coronary artery tone as assessed by M-mode echocardiographic measurement of the dilation re sponse of the left main coronary artery to nitroglycerin. Background. The definite diagnosis of vasospastic angina is done by a coronary spa sm provocative test using ergonovine maleate or acetylcholine during c ardiac catheterization. Current noninvasive, nonpharmacologic diagnost ic methods are not sensitive enough for the diagnosis of vasospastic a ngina. Methods. Thirty-eight patients who had an angiographically norm al left main trunk were studied. These patients were classified into f our groups based on the presence or absence of more than 50% stenosis in the coronary arteries except for the left main trunk and the result s of the acetylcholine or ergonovine provocative test. At 7 a.m. and a t noon on the same day, the left main trunk diameter was measured by M -mode echocardiography before and after sublingual administration of n itroglycerin (0.3 mg), and its percent dilation was calculated to asse ss coronary artery tone. Results. The percent dilation of the left mai n trunk diameter induced by sublingual nitroglycerin at 7 a.m. and at noon was 22.4 +/- 4.7% (mean +/- SD) and 18.1 +/- 4.0% in 11 patients with vasospastic angina and without coronary stenosis, 14.9 +/- 7.1% a nd 11.2 +/- 6.9% in 9 patients with vasospastic angina and coronary st enosis, 6.1 +/- 3.5% and 7.0 +/- 5.1% in 8 patients without vasospasti c angina but with coronary stenosis and 8.1 +/- 5.6% and 7.8 +/- 5.7% in 10 control subjects. The percent dilation at 7 a.m. was significant ly greater in the vasospastic angina without coronary stenosis group t han in the remaining three groups, and in the vasospastic angina group s, the percent dilation at 7 a.m. was significantly greater than that at noon. When percent dilation at 7 a.m. exceeding 15% was defined as positive for the diagnosis of vasospastic angina, the sensitivity was 80% and the specificity 94%. Conclusions. Basal tone of the left main trunk is elevated in the early morning in vasospastic angina. Dilation of the left main trunk diameter exceeding 15% induced by sublingual n itroglycerin in the early morning as measured by M-mode echocardiograp hy is a highly sensitive and specific criterion for the diagnosis of v asospastic angina.