Best evidence topics (BETs) supporting the use of CB after RA graft
There are few randomized controlled trials (RCT) and some comparative studies that investigated the early and chronic role of CB after RA grafting (Table 1). However, given the high patency rate of the RA grafts, it is possible that all the published studies were largely underpowered to detect even moderate differences in outcome.
In Broadman et al. study13, sixty patients underwent post operative angiography between 1 day and 40 weeks; of these 28 were on CB. Patency rate of the radial arteries was 95.7% and there was no association with CB usage.
Acar et al.3 followed up 50 patients. At long-term follow-up angiography (5-7 years) there were no differences in terms of graft failure among patients on CB treatment (N=27) versus the one who had not CB (N=23).
Possati et al14 followed up 90 patients with RA. All patients received diltiazem for a year postoperatively and 51 patients stopped the medication during the follow-up. There was no difference in graft patency between patients who continued or suspended CB. The same group reported similar results in 200315. Similarly, Arena et al. did not find differences in terms of graft patency in patients with or without 6-months CB therapy16.
Shapira et al.17 randomized 161 patients to postoperative diltiazem or nitrates; key in-hospital and follow-up clinical end points such as mortality, major morbidity, myocardial infarction, use of inotropic agents and need for cardiac catheterization, and reintervention were similar between the two groups.
A 2001 RCT from Gaudino et al.18 assigned 57 and 63 patients to early regimen (1 year) and to chronic regimen CB respectively. After 5 years, patients were reassessed clinically and by stress myocardial scintigraphy; 87 of them were re-studied angiographically. They found no differences regarding either the clinical and scintigraphic results or the RA angiographic status. They concluded that after the first post-operative year the continuation of CB did not affect RA graft patency or clinical and scintigraphic results.
In 2005, the same author randomized 53 and 47 patients to receive and to no receive CCB immediately after RA grafting19. At 1-year follow-up all patients were reassessed clinically and scintigraphically; 83 of them were re-studied angiographically. Again, no differences in terms of clinical outcome, scintigraphic result and patency rate was found between groups.
Gaudino et al. in fact questioned the chronic use of CB since they demonstrated that 1 year after implantation in the coronary artery circulation, the RA tends to lose the muscular component, becoming similar to the LIMA20.
Moran et al.21 followed-up 63 and 52 patients after RA grafting with and without CB respectively. Coronary angiographies were obtained at 1-year in 50 patients. No differences were observed for clinical and angiographic end points in the patients that received CB compared with those who had not.
Cameron et al.22 performed angiogram 5 years post RA grafting in 50 patients; 37 of these patients received CB. The patency rate was high (89%) and no correlation with CCB usage was found.
A post-hoc analysis of the Radial Artery Patency Study23 found that among 440 RA patients, the incidence of RA spasm was not associated with the compliance with the prescribed postoperative CB, although compliance with CB use was high (419 of 440 patients).
Finally, a post-hoc analysis of the Radial Artery Database International ALliance analyzed24 patient-level database included 732 patients (502 on CCB). At median follow-up of 55 months, CCB therapy of at least 1 year was found to be associated with significantly lower risk of MACE and RA graft occlusion.
Nevertheless, despite the lack of definitive evidences, the use of CB after RA grafting is considered ‘routine’ in many centers. A 2003 survey of Canadians cardiac units showed that the vast majority of the surgeons and physicians prescribed CB or other forms of anti-spastic therapy after RA grafting25.