Contemporary coronary graft patency: 5-year observational data from a randomized trial of conduits

The Radial Artery Patency and Clinical Outcomes (RAPCO) study has enrolled patients into two trials to compare the radial artery with the free right internal thoracic artery (if age <70 years) or with saphenous vein (if age >70 years) when grafted onto the largest target other than the left anterior descending artery. Patency outcomes in RAPCO will focus only on the trial graft in each case. However, postoperative angiography from this ongoing study has reassessed all coronary grafts, both trial and nontrial: together these offer a valuable observational overview of likely graft patency in the current era in predominately asymptomatic patients, in contrast to symptom-directed studies that may overestimate the incidence of graft failure.

Protocol-directed percutaneous angiography has been performed at intervals weighted toward the end of the study period, or earlier when directed by symptoms. To date, 184 patients have been studied as per protocol, at time points up to 10 years (mean, 3.9), among whom there are 430 nontrial grafts in addition to the 184 trial grafts. Supplementary angiography (percutaneous or computed tomography) was offered at a fixed 5-year time point postoperatively: at this juncture, 193 trial grafts and 469 nontrial grafts have been imaged. Three masked investigators report grafts as angiographically successful if patent from proximal to distal anastomosis inclusive. Failed grafts include greater than 80% stenosis, string sign, or occlusion.

In staggered protocol-directed angiography, overall patency of the in-situ internal thoracic artery grafts and free arterial grafts was 95.5% (210 of 220) and 91.4%% (150 of 164), respectively, which did not differ significantly (p = 0.13). Saphenous vein graft patency was 83.0% (191 of 230) with a trend to higher failure rate compared with free arterial grafts (p = 0.07), and was significantly lower than that of in-situ internal thoracic artery grafts (p = 0.01). At the optional 5-year time point, outcomes are similar to the protocol-directed findings, with patency of in-situ left and right internal thoracic artery grafts of 95.8% (204 of 213), which was significantly greater than that of the other two groups (p = 0.02 and p < 0.001). Patency of free arterial conduits and saphenous vein grafts was 89.1% (139 of 156) and 82.4% (201 of 244), respectively, which did not differ significantly (p = 0.09) at 5 years.

Although trending to superior patency compared with vein grafts, free arterial conduits have not matched the gold standard achieved by in-situ internal thoracic arteries at trial midpoint. Until the results from RAPCO are available, which will test types of free arterial graft against each other and will compare radial and vein grafts in the longer term, these observational data justify for now our current practice of maximal use of in-situ conduits supplemented by free radial grafts.