Multicenter Radial Artery Patency Study (RAPS) Study Design

The use of an internal thoracic artery rather than a saphenous vein graft for left anterior descending coronary artery bypass is associated with improved long-term outcome. Hence, expanded use of arterial conduits for other coronary targets has been advocated. The radial artery possesses a number of anatomic features that are technically advantageous compared with other arterial conduits. This study will determine the relative patency of the radial artery compared to the saphenous vein for right and circumflex coronary bypass. Patients with graftable multivessel coronary disease and an estimated left ventricular ejection fraction >/= 35% undergoing nonemergent primary isolated coronary bypass surgery are eligible. The right and circumflex vessels must have high-grade lesions (>/= 70% diameter stenosis), with target segments of reasonable quality >/= 1.5 mm in diameter. Patients serve as their own controls. The radial artery is randomly allocated to bypass the right or circumflex territory and a saphenous vein is used for the nonradial site. An internal thoracic artery is used for the left anterior descending coronary artery in all cases. Randomization is stratified by center. The primary study endpoint is graft patency as determined by angiography, 8-12 months postoperatively. The relative patency of the radial artery compared with the saphenous vein will be determined using McNemar's test. A sample size of 464 patients will provide 80% power for a two-tailed test (alpha = 0.05) for a 40% relative reduction in the rate of distal anastomotic occlusion from 12% in the saphenous vein to 7.2% in the radial arteries assuming a 20% within-patient correlation. A single interim analysis will be performed following completion of 232 angiograms. To allow for lack of follow-up angiography in up to 20% of enrolled patients, we plan to randomize a total of 560 patients. It is also our intention to assess the long-term patency (5-10 years) of radial artery relative to saphenous vein grafts in follow-up studies. Three hundred patients were recruited from 12 Canadian, university-affiliated sites from November 1996 until February 1999, of which 128 patients have undergone follow-up angiography. Approximately 80% of those who have been followed for more than 1 year have undergone follow-up angiography. This trial will determine the 8-12 month patency of the radial artery relative to the saphenous vein for non-left anterior descending coronary bypass using a novel study design which helps control for potential bias from individual patient and vessel factors. Positive results would support the use of the radial artery in particular, and multiple arterial grafts in general.