Abstract
Coronary spasm can be induced by acetylcholine (ACh) in many patients without a past history of rest angina. However, the low specificity of ACh for diagnosing coronary spastic angina is a controversial aspect of the ACh stress test. We investigated the clinical significance of the ACh stress test following isosorbide dinitrate (ISDN) administration. In addition, to elucidate the relationship between coronary vasospasm and endothelin (ET), we determined plasma ET-1 levels in patients with vasospastic angina pectoris. Twenty-six (81.3%) out of thirty-two patients (Group P) who developed vasospasm induced by ACh following administration of ISDN, had rest angina, while only seventeen (37.8%) out of forty-five patients (Group N ) who did not develop vasospasm induced by ACh following administration of ISDN, had rest angina. The frequency of subjective chest pain at rest was significantly higher in Group P than in Group N (81.3% vs. 37.8%: p<0.01) . Therefore, the post-ISDN ACh stress test may be useful in detecting true vasospastic angina pectoris. Plasma ET-1 levels in the coronary sinus increased significantly from a basal value of 3.13 to 3.78 pg/ml in patients who developed ACh induced vasospasm following injection of ISDN (p<0.05) . These patients exhibited symptoms to the clinical symptoms of rest angina, but there was no change in the other patients. Elevated plasma levels of ET-1 might directly or indirectly increase the level of vascular smooth muscle contraction. This study suggests that the development of ACh-induced vasospasm following administration of ISDN might be due not only to injury of vascular endothelial cells but also to the increased contractility of vascular smooth muscle cells.
