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Calcium-Channel Blocker After CABG With Radial Artery
Study Questions:
Does calcium-channel blocker (CCB) use after coronary artery bypass grafting (CABG) with radial artery grafts improve outcomes and long-term graft patency?
Methods:
Patient data were pooled from six randomized controlled trials examining CABG with radial artery grafts. Postoperative CCB was recommended per protocol in each individual trial. Primary outcome was a composite of major adverse cardiac events (MACE), and secondary outcome was radial artery graft occlusion at maximum follow-up, with patency rate graded according to the Fitzgibbon classification. Treatment effects were analyzed in multivariable Cox models adjusted for age, sex, diabetes, previous myocardial infarction, surgical priority, renal insufficiency, target vessel, location of radial artery proximal anastomosis, and off-pump surgery.
Results:
Of 732 patients in the pooled trials, 502 received CCB therapy. Protocol-driven angiographic follow-up was available for 243 patients in the CCB group and 200 in the no CCB group. Median clinical follow-up was 60 months and median angiographic follow-up was 55 months. Cumulative incidence of MACE in the CCB vs. no CCB groups at 36, 72, and 108 months was 3.7% vs. 9.3%, 13.4 vs. 17.6%, and 16.8% vs. 20.5%, respectively (log rank p = 0.003). Cumulative incidence of radial artery occlusion in the CCB vs. no CCB groups at the same time points was 0.9% vs. 8.6%, 9.6% vs. 21.4%, and 14.3% vs. 38.9%, respectively (log rank p < 0.001). In the multivariate Cox model adjusting for confounders, CCB therapy was associated with significantly lower risk of MACE (hazard ratio [HR], 0.52; 95% confidence interval [CI], 0.31-0.89; p = 0.02) and radial artery graft occlusion (HR, 0.20; 95% CI, 0.08-0.49; p < 0.001), which was true for both diltiazem and amlodipine. When examining duration of therapy, CCB therapy for 1 year was associated with greater reduction in MACE than a shorter duration of CCB therapy (p < 0.001).
Conclusions:
Use of CCB therapy after CABG with radial artery grafts is associated with a significantly lower incidence of MACE and higher graft patency.
Perspective:
Either the right internal mammary artery or the radial artery can be used as a second arterial graft in CABG. Particular qualities of the radial artery include a thick muscular component that may predispose to spasm. CCBuse after CABG with radial artery is traditionally prescribed, but the practice has not been strongly supported by the literature, and the specific regimen (both in-hospital and at discharge) and duration of regimen has varied. This study attempts to determine using data from pooled randomized controlled trials whether CCB is associated with improved outcomes after CABG. The major limitation of the study is that the specific regimen and duration was not standardized across studies, that there could be selection bias as to which patients received CCB therapy, and that patient compliance could not be monitored. Regardless, the study controlled for many confounding factors, and since CCB therapy is relatively low-cost and associated with low risk of complications, it seems to be that the potential benefits would outweigh the risks. Interestingly, the duration of therapy of 1 year was associated with greater benefit, and this may influence current practice patterns for cardiac surgeons and cardiologists who prescribe CCB therapy for their patients post-CABG with radial artery grafts.
Clinical Topics: Cardiac Surgery, Cardiovascular Care Team, Invasive Cardiovascular Angiography and Intervention
Keywords: Amlodipine, Calcium Channel Blockers, Cardiac Surgical Procedures, Coronary Artery Bypass, Coronary Artery Bypass, Off-Pump, Coronary Occlusion, Diabetes Mellitus, Diltiazem, Myocardial Infarction, Postoperative Period, Radial Artery, Renal Insufficiency, Risk
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