Do angiographic results from symptom-directed studies reflect true graft patency?

BACKGROUND: Coronary artery graft patency results have been obtained from repeat angiograms in patients who presented with evidence of ischemia. The purpose of this study is to compare protocol-directed angiographic results from a randomized clinical trial with symptom-directed angiography in nontrial patients. METHODS: Repeat angiography after primary isolated coronary artery bypass grafting was performed in 337 of 2,259 patients between July 1996 and September 2004. Patients were divided into two groups: 596 graft angiograms in 192 trial patients were compared with 389 graft angiograms in 142 nontrial patients. The mean interval from surgery was 1,306 +/- 800 days versus 1,119 +/- 777 days, respectively. Grafting techniques were similar in both groups except that the right internal thoracic artery was used almost exclusively as a free graft in the trial patients. Angiographic outcomes were defined as patent (stenosis <80%) or failure (stenosis > or =80%, occlusion, or the string sign). Comparisons of trial versus nontrial grafts were made using a generalized linear mixed model. Five-year estimates of graft patency were made using survival analyses accounting for interval censoring. RESULTS: The odds ratio for graft failure for nontrial compared with trial patient grafts was 2.6 (95% confidence interval, 1.6 to 4.3; p < 0.001). Cumulative patency estimates for all grafts at 5 years were trial 91% versus nontrial 83%, p = 0.004. Five-year estimates for individual conduits were left internal thoracic artery, 99% versus 92%, p = 0.002; right internal thoracic artery, 86% versus 87%, p = 0.8; radial artery, 87% versus 86%, p = 0.6; and saphenous vein, 86% versus 56%, p = 0.003. CONCLUSIONS: Graft patency rates were superior in the trial compared with nontrial patients. Symptom-directed graft failure rates were approximately double those of trial patients.