Omitting 50 μg of intracoronary acetylcholine injection in the left coronary artery during spasm provocation test.

BACKGROUND

Although guidelines recommend intracoronary administration of acetylcholine (ACh) with incremental doses of 20, 50, and 100 μg into the left coronary artery (LCA) during spasm provocation test for diagnosing vasospastic angina, 50 μg of ACh rarely induced significant coronary vasospasm when no vasoconstriction was observed with 20 μg of ACh in a previous report. The aim of this study was to evaluate the safety and feasibility of omitting 50 μg according to the vasoreactivity by 20 μg of ACh in the LCA.

METHODS

A total of 556 patients undergoing ACh provocation test with 20 μg followed by 50 and/or 100 μg were retrospectively included. Injection of 50 μg of ACh was primarily omitted when vasoconstriction <25 % was observed with 20 μg, which was left to operator's discretion. Adverse events were defined as a composite of ventricular fibrillation, sustained ventricular tachycardia, and cardiogenic shock during ACh test in the LCA.

RESULTS

Positive ACh test in the LCA was observed in 245 (44.1 %) patients. Overall, patients with LCA constriction <25 % by 20 μg of ACh had a lower rate of positive ACh test than their counterpart (24.0 % vs. 88.4 %, p < 0.001). In patients with LCA constriction ≥25 % by 20 μg, the incidence of adverse events was significantly higher than in those with LCA constriction <25 % during the provocation test at doses of 50 and 100 μg (2.3 % vs. 0 %, p = 0.009).

CONCLUSIONS

Omitting 50 μg of ACh in the LCA may be safe and feasible when little vasoconstriction was observed with preceding injection of 20 μg of ACh during spasm provocation test for diagnosing vasospastic angina. However, we believe that 50 μg of ACh should not be omitted when 20 μg of ACh induced LCA constriction ≥25 %.