Predictive value of coronary artery dilation response to nitrate for a positive intracoronary acetylcholine provocation test.

Background: Baseline coronary artery diameter and coronary artery dilation response to nitrate are associated with coronary vasoreactivity.

Objectives: The present study investigated the predictive value of coronary artery tone for a positive intracoronary acetylcholine (ACh) provocation test.

Methods: A total of 197 patients who underwent an ACh provocation test in the right coronary artery were included. A positive ACh provocation test was defined as transient total or subtotal occlusion of a coronary artery with signs/symptoms of myocardial ischemia. The segment, from the ostium to the bifurcation, of the right coronary artery was analyzed quantitatively. Coronary artery dilation response to isosorbide dinitrate (ISDN) was defined as the mean lumen diameter after an intracoronary injection of ISDN divided by the diameter before administration of ACh (i.e. baseline coronary artery diameter).

Results: After the administration of ACh, 49 patients (24.9%) had a positive ACh provocation test. Smaller baseline right coronary artery diameter (2.35±0.45 vs. 2.73±0.48 mm, P<0.001) and greater right coronary artery dilation response to ISDN (1.34±0.12 vs. 1.15±0.11, P<0.001) were observed in patients with a positive ACh provocation test. The receiver operating characteristic curve for baseline coronary artery diameter poorly predicted the occurrence of a positive ACh provocation test (area under the curve 0.71). The predictive values of dilation response of the right coronary artery to ISDN for the occurrence of a positive ACh provocation test (area under the curve 0.87) was significantly better compared with that of baseline right coronary artery diameter (P<0.001).

Conclusion: Coronary artery dilation response to nitrate is a more accurate predictor of a positive intracoronary ACh provocation test compared with baseline coronary artery diameter.