The acetylcholine administration time plays the key role for provoked spasm in the spasm provocation test.

Background: Acetylcholine (ACh) was administered for 3min in the ENCORE study, while the Japanese Circulation Society guidelines recommended the 20s ACh injection as an ACh test.

Objectives: We compared the ischemic findings between ACh administration for 3min and ACh injection for 20s in the same patients and in the same ACh doses without administration of nitrates in the left coronary artery.

Methods: We investigated 30 patients with ischemic heart disease (25 men, 67±10 years, ACh 50μg: 3, ACh 100μg: 9, ACh 200μg: 18) by the above two ACh injection procedures. Temporary pacemaker was inserted and set at the rate of 40/min. Positive provoked spasm was defined as transient ≥90% narrowing and typical chest symptoms or ischemic electrocardiographic (ECG) changes.

Results: Provoked spasm was observed in 22 patients with ACh 20s injection, while 10 patients had provoked spasm by ACh 3min administration (73.3% vs. 33.3%, p<0.05). Ischemic ECG changes (50.0% vs. 23.3%, p<0.05) and chest symptoms (73.3% vs. 43.3%, p<0.05) were significantly higher with ACh 20s injection than ACh 3min administration. Pacemaker rhythm was recognized in 19 patients with ACh 20s injection, whereas 7 patients with ACh 3min administration had a pacemaker rhythm (63.3% vs. 23.3%, p<0.01). Maximal ST elevation by ACh 20s injection was significantly higher than that by ACh 3min administration (0.47±0.94 vs. 0.13±0.51, p<0.05), while maximal ST depression was not different between the two procedures. Coronary artery diameter after ACh 20s injection was significantly lower than that after ACh 3min administration in the left anterior descending artery.

Conclusions: ACh administration procedures (3min or 20s injection) may influence the ischemic findings in spasm provocation testing.