Effects of Nicorandil, Isosorbide Mononitrate, or Diltiazem on Radial Artery Grafts After CABG: The Randomized ASRAB-Pilot Trial

BACKGROUND: The optimal antispastic treatment after coronary artery bypass grafting using radial artery (RA) grafts is controversial. This clinical trial aimed to generate pilot comparative data on the effects of nicorandil, isosorbide mononitrate, or diltiazem on RA grafts. METHODS: This was a single-center, randomized, open-label, parallel-group pilot trial. Eligible patients who underwent coronary artery bypass grafting using RA grafts were randomized in a 1:1:1 ratio to receive oral nicorandil (15 mg daily), isosorbide mononitrate (50 mg daily), or diltiazem (180 mg daily) for 24 weeks post-coronary artery bypass grafting. The primary outcome was RA graft failure (modified Fitzgibbon grade B, S, or O) at 1 and 24 weeks, assessed by coronary computed tomography angiography. RESULTS: Among 150 randomized participants, 149 (mean age, 56.8 years; 13.4% women) with 177 RA grafts were assessed at least once by coronary computed tomography angiography, including 50 participants with 64 RA grafts in the nicorandil group, 50 participants with 57 RA grafts in the isosorbide mononitrate group, and 49 participants with 56 RA grafts in the diltiazem group, respectively. At 1 week post-coronary artery bypass grafting, the RA graft failure rates were lower with nicorandil versus diltiazem (19.4% versus 25.0%; difference, −5.6% [95% CI, −20.6% to 9.3%]) and isosorbide mononitrate versus diltiazem (18.2% versus 25.0%; difference, −6.8% [95% CI, −21.8% to 8.6%]). The RA graft failure rates were slightly higher with nicorandil versus isosorbide mononitrate (19.4% versus 18.2%; difference, 1.2% [95% CI, −13.3% to 15.2%]). At 24 weeks, RA graft failure rates were lower with nicorandil versus diltiazem (16.1% versus 27.8%; difference, −11.7% [95% CI, −26.6% to 3.4%]), and isosorbide mononitrate versus diltiazem (12.5% versus 27.8%; difference, −15.3% [95% CI, −29.8% to −0.2%]), and slightly higher with nicorandil versus isosorbide mononitrate (16.1% versus 12.5%; difference, 3.6% [95% CI, −9.6% to 16.4%]). CONCLUSIONS: In this pilot trial, treatment with nicorandil or isosorbide mononitrate was associated with a lower RA graft failure rate compared with diltiazem. Larger hypothesis-testing trials are warranted. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04310995.