Letter by Mohri Regarding Article, 'Clinical Usefulness, Angiographic Characteristics, and Safety Evaluation of Intracoronary Acetylcholine Provocation Testing Among 921 Consecutive White Patients With Unobstructed Coronary Arteries'

Angina caused by spasm of the large epicardial coronary artery has been extensively investigated for >50 years, and its risk factors, diagnostic procedures, treatments, and prognosis are well established. In 1998, we proposed coronary microvascular spasm as a possible pathogenic mechanism of myocardial ischemia in Japanese patients with chest pain and normal epicardial coronary arteries (microvascular angina),1 which was later confirmed by others.2 In the cardiac catheterization laboratory, the occurrence of coronary microvascular spasm is suspected when patient’s symptoms are reproduced in association with ischemic electrocardiographic changes after intracoronary injection of acetylcholine or ergonovine without large epicardial artery hyperconstriction/spasm. Coronary …