AimTo investigate the impact of nicorandil on coronary flow reserve (CFR) in patients with slow coronary flow.MethodsA total of 44 patients with coronary slow flow but normal coronary angiography were included in this study, patients were divided into nicorandil group (5 mg/d for 6 months, n＝24) and control group (n＝20), Doppler coronary flow velocity and Doppler reserve measurement of distal left anterior descending were recorded at rest and adenosine measurement of distal left anterior descending were recorded at rest and adenosine infusion induced hyperemia state, CFR was calculated by the ratio of maximal hyperemia and baseline peak diastolic coronary flow velocity (HCFV and BCFV) before and after nicorandil treatment.Results6 months later, compared with control group and nicorandil group before treatment, 6 months nicorandil treatment was associated with no difference of BCFV (26.37±5.39 cm/s vs 24.72±4.35 cm/s, p>0.05; 26.37±5.39 cm/s vs 24.61±6.18 cm/s, p>0.05), increased HCFV (73.69±9.84 cm/s vs 55.97±7.62 cm/s, p<0.05; 73.69±9.84 cm/s vs 51.29±9.72 cm/s, p<0.05), and increased CFR (2.79±0.53 vs 1.99±0.47, p<0.05; 2.79±0.53 vs 2.08±0.44, p<0.05).ConclusionCoronary flow reserve could be significantly improved by nicorandil therapy in patients with coronary slow flow