How many arterial grafts are enough? A population-based study of midterm outcomes

Objective — Current evidence suggests arterial grafting improves freedom from cardiac events after coronary artery bypass graft surgery. It has been shown that 2 arterial grafts provide improved outcome compared with 1 arterial graft. This population study seeks to understand trends in arterial graft use and midterm outcomes of patients receiving 1, 2, or 3 arterial grafts.

Methods — This study is a retrospective population-based cohort of 53,727 patients (47,214 with 1 arterial graft, 5466 with 2 arterial grafts, and 1047 with 3 arterial grafts) undergoing isolated coronary artery bypass graft surgery in Ontario (1991-2001). The patients were followed by using linked clinical and administrative data, with complete follow-up until December 31, 2003 (average patient years of follow-up: 6 years for those with 1 arterial graft, 5 years for those with 2 arterial grafts, and 4 years for those with 3 arterial grafts). Propensity matching was used to compare outcomes between patients receiving 1 versus 2 arterial grafts, 2 versus 3 arterial grafts, and 1 versus 2 or 3 arterial grafts. The outcomes included death, repeat revascularization (angioplasty or coronary artery bypass grafting), cardiac readmission (readmission for angina, heart failure, and myocardial infarction), and a composite comprising all of these outcomes. Cox proportional hazards models were used to compare outcomes for propensity-matched patients. Subgroup analyses of various patient risk categories defined by the tercile of predicted 30-day mortality risk were conducted between propensity-matched individuals.

Results — The use of multiple arterial grafts (defined as >1 arterial graft) increased mainly in the latter part of the study, from 4% in 1991 to 27% in 2001. Four thousand nine hundred sixty-eight patients were propensity matched (91% of patients receiving 2 arterial grafts) to compare outcomes with those of patients receiving 1 arterial graft. One thousand twenty-eight patients were propensity matched (98% of those receiving 3 arterial grafts) to compare outcomes with those of patients receiving 2 arterial grafts. Five thousand four hundred ninety-one patients were propensity matched (84% of those receiving 2 or 3 arterial grafts) to compare outcomes with those of patients receiving 1 arterial graft. Two arterial grafts were shown to be protective for cardiac readmission (0.8; 95% confidence interval, 0.76-0.92) and a composite outcome (0.9; 95% confidence interval, 0.72-0.95) compared with 1 arterial graft. Two or 3 arterial grafts were further found to improve survival (0.8; 95% confidence interval, 0.72-0.99). In all patient operative risk categories, 2 or 3 arterial grafts were protective for cardiac readmission (hazard ratio, 0.7-0.8) and the composite outcome (hazard ratio, 0.8). There was no difference in the Cox hazard ratios of propensity-matched patients in the comparison of the groups receiving 3 versus 2 arterial grafts.

Conclusions — Few patients received more that 1 arterial graft in our region. There was a survival benefit in receiving 2 or 3 arterial grafts. Patients with low, moderate, and high operative risk receiving 2 or 3 arterial grafts had lower rates of cardiac readmission compared with patients receiving only 1 arterial graft. This suggests that the standard of care should include the use of at least 2 arterial bypasses in all categories of operative risk to allow for optimal midterm outcomes.