Interventional cardiology

Is this the final word on calcium channel blockers after radial artery grafts?

The use of calcium channel blockers (CCB) in patients with radial artery grafts improves the clinical and angiographic outcomes from coronary artery bypass surgery, a study shows.

The post-hoc analysis of data from six randomised controlled trials of the radial artery grafts found CCB therapy reduced the incidence of major adverse cardiac events (MACE) and graft occlusion.

The research, comprising more than 700 patients, found patients who received CCB had consistently fewer MACE at all time points compared to patients who did not receive CCB.

The cumulative incidence of MACE was 3.7% v 9.3% at 36 months, 13.4% v 17.6% at 72 months and 16.8% v 20.5% at 108 months in the CCB and no CCB groups respectively.

Similarly, the incidence of radial artery occlusion was 0.9% v 8.6% at 36 months, 9.6% v 21.4% at 72 months, and 14.3% v 38.9% at 108 months.

The study found the optimal duration of CCB therapy was at least one year.

When classes of CCB were analysed separately, it found that both diltiazem (HR: 0.29, p=0.008) and amlodipine (HR: 0.42, p=0.005) were associated with a lower risk of MACE compared to no CCB. A similar effect was seen with graft occlusion.

The multinational study, which was coauthored by the Austin Hospital’s Professor David Hare, said CCB was almost routinely prescribed in most centres after radial artery grafting due to concerns about postoperative spasm.

“It must be noted that in the years after implantation in the coronary circulation, RA grafts lose most of the muscular component of the media and of their spastic tendency, becoming very similar to internal thoracic artery grafts. On this basis, it is possible that the benefits of CCB are limited to the initial postoperative period,” the study authors said.

But CCB therapy was not without its downsides including side effects, precluding the use of other preventive therapies, and cost.

And accompanying editorial in the Journal of the American College of Cardiology, said the effect size in the study was ‘impressively large’.

However the editors highlighted some caution was warranted due to the lack of randomisation and differences between the CCB and non-CCB groups.

“Undoubtedly, the present paper will affect recommendations regarding the use of a CCB after radial CABG, but sometimes at the detriment of other organ- and life-preserving medications; therefore, some circumspection must remain in effect,” they said.

They acknowledged that given most centres had been prescribing CCB therapy empirically, their use may not represent enough of a healthcare dilemma to warrant the costs of a randomised controlled trial.

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