Effect of Nicorandil, Diltiazem, or Isosorbide Mononitrate for Oral Antispastic Therapy After Coronary Artery Bypass Grafting Using Radial Artery Grafts-A Pilot Randomized Controlled Trial (ASRAB-Pilot): Rationale and Study Protocol.

INTRODUCTION: The current evidence for chronic oral antispastic medication use after coronary artery bypass grafting using radial artery grafts (RA-CABG) is controversial. Calcium channel blockers, such as diltiazem, are the most commonly used antispastic medications after RA-CABG; other options include nitrates and nicorandil, but to date no sufficiently powered randomized controlled trials have been conducted to compare their efficacy. METHODS: This is a single-center, open-label, parallel three-arm, pilot randomized controlled trial. Patients without contraindications to any study medications and who successfully underwent RA-CABG surgery will be consecutively screened. Eligible patients will be randomized in a ratio of 1:1:1 (a total of 150 patients, 50 per arm) to receive nicorandil 5 mg orally thrice daily, diltiazem 180 mg orally once daily, or isosorbide mononitrate 50 mg orally once daily for 24 weeks. The primary outcomes are RA graft failure at week 1 and week 24. The secondary outcomes include major adverse cardiovascular event (MACE, a composite of all-cause death, myocardial infarction, stroke, and unplanned revascularization) and angina recurrence. The safety outcomes include hypotension occurrence, withdrawal of renin angiotensin aldosterone system inhibitors, serious adverse events, and other concerned adverse events within 24 weeks. CONCLUSION: This pilot trial will compare the preliminary effects of nicorandil, diltiazem, and isosorbide mononitrate on angiographic and clinical outcomes in patients who have undergone RA-CABG. Recruitment began in June 2020, and the estimated primary completion date is early 2023. Results of this study will provide much needed information for design of large confirmatory trials on the effectiveness of oral antispastic medications after RA-CABG.