Coronary flow reserve (CFR) is the capability of coronary arteriolar bed to dilate in response to increased cardiac metabolic demand. Nocorandil, a hybrid of ATP-sensitive K+ channel opener and nitrates, causes coronary vasodilation of both epicardial and resistance vessels. We investigated the feasibility and safety of nicorandil as compared to adenosine in the measurement of CFR using a Doppler guide wire.

We measured CFR in 26 consecutive patients (mean age 52±19 years, M:F=16:10) during coronary intervention with a 0.014-inch Doppler guide wire. We recorded the baseline average peak velocity (APV) and the hyperemic APV induced by intracoronary adenosine or nicorandil. The heart rate, mean aortic pressure and the time interval from maximal APV to baseline APV were also recorded.

There were no significant differences between APV, diastole/systole velocity ratio and CFR induced by adenosine and those induced by nicorandil (44.4 ± 17.3 vs 45.5 ± 17.6, p=0.78, 1.59 ± 0.51 vs 1.57 ± 0.52 p=0.78, 2.22 ± 0.89 vs 2.27 ± 0.94, p=0.36). The CFR and diastole/systole velocity ratio induced by nicorandil showed a strong positive linear correlation with those by adenosine (r²=0.77, p=0.0001, r²=0.83, p=0.0001). Adenosine significantly decreased the heart rate as compared to nicorandil =-25.5 ± 9.7 vs -8.7 ± 4.9 bpm, p=0.001). There were no differences in the changes of mean aortic pressure between adenosine and nicorandil (-7 ± 9 vs -2 ± 3 mmHg, p=0.17). Nicorandil prolonged the time interval from maximal APV to baseline APV compared to adenosine (194 ± 62 vs 37 ± 12 sec, p=0.001).

Nicorandil is feasible and safe for use in measuring CFR using a Doppler guide wire and may replace adenosine.