A new noninvasive method of diagnosing vasospastic angina based on dilation response of the left main coronary artery to nitroglycerin as measured by echocardiography

Second Department of Internal Medicine, Kagawa Medical School, Japan.

OBJECTIVES: The purpose of the present study was to evaluate the feasibility of diagnosing vasospastic angina based on coronary artery tone as assessed by M-mode echocardiographic measurement of the dilation response of the left main coronary artery to nitroglycerin. BACKGROUND: The definite diagnosis of vasospastic angina is done by a coronary spasm provocative test using ergonovine maleate or acetylcholine during cardiac catheterization. Current noninvasive, nonpharmacologic diagnostic methods are not sensitive enough for the diagnosis of vasospastic angina. METHODS: Thirty-eight patients who had an angiographically normal left main trunk were studied. These patients were classified into four groups based on the presence or absence of more than 50% stenosis in the coronary arteries except for the left main trunk and the results of the acetylcholine or ergonovine provocative test. At 7 a.m. and at noon on the same day, the left main trunk diameter was measured by M-mode echocardiography before and after sublingual administration of nitroglycerin (0.3 mg), and its present dilation was calculated to assess coronary artery tone. RESULTS: The percent dilation of the left main 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% and 11.2 +/- 6.9% in 9 patients with vasospastic angina and coronary stenosis, 6.1 +/- 3.5% and 7.0 +/- 5.1% in 8 patients without vasospastic 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 significantly greater in the vasospastic angina without coronary stenosis group than in the remaining three groups, and in the vasospastic angina groups, 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 nitroglycerin in the early morning as measured by M-mode echocardiography is a highly sensitive and specific criterion for the diagnosis of vasospastic angina.

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