Safety and efficacy of a novel hyperaemic agent, intracoronary nicorandil, for invasive physiological assessments in the cardiac catheterization laboratory

AIMS: Maximal hyperaemia is a key element of invasive physiological studies and adenosine is the most commonly used agent. However, infusion of adenosine requires additional venous access and can cause chest discomfort, bronchial hyper-reactivity, and atrioventricular conduction block. The aim of this study was to evaluate the feasibility and efficacy of intracoronary (IC) nicorandil as a novel hyperaemic agent for invasive physiological studies. METHODS AND RESULTS: We enrolled 210 patients who underwent fractional flow reserve (FFR) measurement. Hyperaemic efficacy of the following methods was compared: IC bolus injection of adenosine; intravenous (i.v.) infusion of adenosine (140 μg/kg/min); and IC bolus of nicorandil (1 and 2 mg). In 70 patients, the index of microcirculatory resistance was also measured. Hyperaemic efficacy of IC nicorandil 2 mg was non-inferior to that of i.v. adenosine infusion (FFR: 0.82 ± 0.10 vs. 0.82 ± 0.10; P for non-inferiority < 0.001). There was a strong correlation between FFRs measured by i.v. adenosine and IC nicorandil (R² = 0.934). Nicorandil produced fewer changes in blood pressure, heart rate and PR interval, and less chest pain than adenosine (all P-values < 0.05). Atrioventricular block occurred in 12 patients with IC adenosine, 4 patients with i.v. adenosine and none with IC nicorandil. The index of microcirculatory resistance was 18.3 ± 8.7 with i.v. adenosine and 17.2 ± 7.6 with IC nicorandil (P = 0.126). CONCLUSION: This study suggests that IC bolus injection of nicorandil is a simple, safe, and effective way to induce steady-state hyperaemia for invasive physiological evaluations. Clinicaltrials.gov number: NCT01331902.