Should patients receiving a radial artery conduit have post-operative calcium channel blockers?

Abstract

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether calcium channel blockers or possibly nitrates are necessary if a radial artery conduit has been used for coronary artery bypass grafting. The reported search found 98 papers of which 14 represented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group, relevant outcomes and weaknesses were tabulated. We conclude routine use of calcium channel blockers (CCBs) and nitrates, in order to reduce vasospasm, is in widespread use but none of the clinical studies that we identified provided any evidence for their benefit. Furthermore, one study demonstrated that a vasoconstrictor mediated increase in blood pressure actually increased blood flow in the radial artery, and a further study reported that serotonin induced vasospasm was not attenuated by CCBs in vivo. All these studies are underpowered to exclude a benefit of vasodilators in improving graft patency in the medium term. However, an RCT that sought to prove an increase of 5% in patency rates (which are already around 90% or more) with a power of 80% would have to recruit and perform medium term angiography on 948 patients.

The Choice of Conduits in Coronary Artery Bypass Surgery

“…finding is probably the anatomic background for the demonstrated lack of utility of long-term antispastic therapy in patients with RA grafts(15)…”

Reappraisal of a 20-year experience with the radial artery as a conduit for coronary bypass grafting

“…In addition to the aforementioned situation, competitive flow was encountered in cases with proximal left main stenosis whenever a patent left IMA-to-LAD graft provided unrestricted flow to the circumflex territory or in cases of chronic coronary occlusion whose distal run-off was supplied by an abundant collateral circulation. As in several other studies [23,24], the prescription of calcium channel blockers was not identified as a determinant of radial artery patency. For several years, we no longer recommend the systematical use of this medication in radial artery grafting.…”

Conventional Coronary Artery Bypass Graft Surgery

“…The midterm patency rates are encouraging (85% to 90% at 5 years), but are clearly inferior to IMA grafts, and are similar to of SVG grafts in recent studies [5]- [7].…”

“…Additionally, Verapamil, 0.5 mg/hr, is given to patients intravenously if they are hemodynamically able to tolerate it. Postoperatively the patient is started on amlodipine, 5 mg/day, or Diltiazam SR 60 -120 mg/ day after discontinuing intravenous verapamil [5] [7].…”