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

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.