Dose maximal acetylcholine dose into the left coronary artery affect the positive provoked spasm in the left circumflex artery?

Positive provoked spasm in the left circumflex artery (LCX) is lower than that in the left anterior descending artery and right coronary artery (RCA).We examined the provoked positive spasm in the LCX between the maximal acetylcholine (ACh) 100 μg period (January 1991 to July 2012, 1474 patients: the former period) and the maximal ACh 200 μg period (August 2012 to August 2018, 336 patients: the latter period). ACh was injected in incremental dose of 20/50/100/200 μg into the left coronary artery and of 20/50/80 μg into the RCA. Positive spasm was defined as at least 90% stenosis and usual chest symptoms or ischemic ECG changes.Provoked positive spasm in the latter period was significantly higher than that in the former period (65.5 vs. 39.1%, P0.001). The positive spasm increase of RCA and left anterior descending artery was 143 and 159%, whereas the increase of LCX was 204%. Multiple-vessel spasm was also increased in the latter period.Maximal ACh dose into the left coronary artery may affect the positive spasm in the LCX and multiplevessel spasm.