Feasibility of omitting provocation test with 50 μg of acetylcholine in left coronary artery.

According to the Japanese Circulation Society guideline of vasospastic angina, incremental doses of acetylcholine (ACh) are prescribed for coronary spasm provocation: 20 and 50 μg for the right coronary artery (RCA), and 20, 50 and 100 μg for the left coronary artery (LCA). However, provocation by low doses of ACh in patients with low vasoreactivity may be less needed, and the requirement of 50 μg of ACh for the LCA in these patients has not been evaluated. In the present study, patients who underwent ACh provocation test for both the RCA and LCA were included. The positive diagnosis of intracoronary ACh provocation test was defined as total or subtotal coronary artery narrowing (i.e., angiographic coronary artery spasm) accompanied by chest pain and/or ischemic electrocardiographic changes. Coronary artery constriction was visually evaluated and defined as coronary artery diameter reduction <25 or 25-90% in patients without angiographic coronary artery spasm by 20 µg of ACh in the LCA. There were 33 out of 249 patients (13%) with LCA spasm by 20 µg of ACh. In subjects without LCA spasm by 20 µg of ACh, patients with coronary constriction <25% (n = 101) by 20 µg of ACh in the LCA rarely showed coronary artery spasm induced by 50 μg of ACh in the LCA, in comparison to those with coronary constriction 25-90% (n = 115) (2.6 vs. 32.7%, p < 0.001). None of the patients with coronary constriction <25% by 20 µg of ACh in the LCA had cardiac complications associated with administration of ACh. In conclusion, omission of 50 µg of ACh in the LCA may be possible when there is little coronary artery constriction by 20 µg of ACh in the LCA during provocation test, leading to less contrast and shortens overall procedure time.