Effect of training on outcomes following coronary artery bypass graft surgery

Abstract

Objective: We examined our coronary artery bypass surgery (CABG) experience to assess the effect of training on mortality and morbidity outcomes.

Methods: Between April 1997 and September 2002, 5678 consecutive patients underwent isolated CABG. Five hundred and fifty-five (9.9%) were performed by trainee surgeons. Multivariate logistic regression was used to assess the effect of training on adverse outcomes, while adjusting for patient and disease characteristics (treatment selection bias). Cox proportional hazards analysis was used to adjust Kaplan-Meier survival curves. Treatment selection bias was controlled for by constructing a propensity score from core patient characteristics including the additive EuroSCORE. The propensity score was the probability of CABG performed by trainee, with a C-statistic of 0.79, and was included along with the comparison variable (trainee vs Consultant) in a multivariable analysis of outcome. The propensity score is used as the sole variable for adjustment due to the low number of events, providing a more complete risk adjustment.

Results: CABG procedures performed by trainee surgeons were less likely to be female, hypertensive, obese, triple-vessel disease, redo and emergency cases. Also, trainee surgeons were less likely to operate on patients with cerebrovascular disease, renal dysfunction, and previous myocardial infarctions, prior gastrointestinal surgery, and poor left ventricular ejection fraction. The additive EuroSCORE was 2.9 in trainee cases compared to 3.5 in Consultant led cases (P<0.001) Crude outcomes were significantly better in trainee CABGs due to selection bias. In-hospital results were no longer significantly different between both groups after adjusting for the propensity score. The adjusted freedom from death in the trainee cases at 30 days, 1, 2, 3, and 4 years was 98.1, 96.2, 94.7, 93.2 and 91.8%, respectively, compared to 97.9, 95.7, 94.1, 92.3 and 90.8% for the Consultant led cases (P=0.53).

Conclusions: After adjusting for case-mix, with careful case selection, training does not adversely affect the early and mid-term outcomes of CABG.