D. Tam, S. Fremes
Oct 6, 2020
In patients with advanced multivessel coronary artery disease, coronary artery bypass grafting is the treatment of choice and is associated with improved survival and freedom from major adverse cardiac and cerebrovascular events.1 The longterm durability of coronary artery bypass grafting is predicated on patent grafts, and understanding factors to improve graft patency remains critically important. There remains continued debate as to what the second best conduit is for the next most important lesion.2 There is mounting evidence to suggest a multiarterial grafting approach may improve survival and freedom from major adverse cardiac and cerebrovascular events compared with a single arterial grafting strategy.3,4 The RAPCO trial (Radial Artery Patency and Clinical Outcomes) was undertaken to better understand the arterial grafting hypothesis and to better define which is the second best conduit for coronary surgery.5 In this issue of Circulation, the eagerly awaited findings of the primary analysis of the RAPCO trials are published.5 The results were initially presented at the 96th Annual Meeting of the American Association for Thoracic Surgery in Baltimore, MD, in 2016. The RAPCO investigations are 2 separate angiographic randomized trials testing the superiority of the radial artery (RA) compared with either the free right internal thoracic artery (RITA) or saphenous vein graft (SVG) for graft patency over a follow-up of 10 years. Mortality was the other primary outcome, but sample sizes were not determined for the mortality end point. The RA to SVG comparison was the smaller of the 2 studies. In 225 patients randomized to either RA or SVG, RA patency was improved at 10 years (85% versus 71%), and the hazard ratio (HR) for graft failure was 0.40 (95% CI, 0.15–1.00). In contrast, the RA to RITA comparison was much larger. In 394 patients randomized to either RA or RITA, 10-year patency was significantly better with RA (89% versus 80%), with a HR of 0.45 for graft failure (95% CI, 0.23–0.88). Resulting 10-year survival was also improved in the RA group compared with the RITA group (HR, 0.53 [95% CI, 0.30–0.95]), whereas a significant improvement in survival was not demonstrated between RA and SVG (HR, 0.76 [95% CI, 0.47–1.22]). The study started recruitment in June 1996 and completed enrollment March 2005. To put the study in perspective, the published findings are now available >24 years after the first patient was randomized. For context, it is first important to understand some of the inherent limitations of graft patency studies such as RAPCO. Generalizability of findings may be limited because patients must be healthy enough to undergo protocol-driven coronary angiography; for example, this would exclude patients with renal insufficiency. There may be concerns about internal validity of the findings given incomplete ascertainment of the primary outcome in a proportion of patients. In RAPCO, per-protocol © 2020 American Heart Association, Inc.