Differences in Coronary Microvascular Spasms Induced by Acetylcholine and Ergonovine

Background There are no comparative studies on provoked coronary microvascular spasm (CMS) in patients undergoing both acetylcholine (ACh) and ergonovine (EM) vasoreactivity testing. Objectives We investigated the incidence of provoked CMS in patients with ischemia with nonobstructive coronary artery disease (INOCA) undergoing ACh and EM vasoreactivity testing. Methods We recruited 494 INOCA patients who underwent both ACh and EM vasoreactivity testing. ACh was injected at incremental doses of 20/50/100/200 μg into the left coronary artery (LCA) and 20/50/80 μg into the right coronary artery (RCA), whereas 40 μg of EM was administered into the RCA and 64 μg into the LCA. Positive CMS was defined as <75% transient coronary constriction, accompanied by typical chest symptoms or ischemic ECG changes. Results Among the 494 patients, CMS was observed in 23 (4.7%) patients. Eighteen patients had CMS alone, and 5 patients had coexisting epicardial spasm. The ACh test alone, EM test alone, and both tests provoked CMSs in 12 patients, 7 patients, and 4 patients, respectively. There were no marked differences in incidence between ACh- and EM-induced CMS (70% vs. 48%, p=0.2307). Conclusions Differences were observed between ACh-induced CMS and EM-induced CMS. The complementary use of vasoreactivity testing is essential for accurately documenting the presence of CMS in real-world settings.