Coronary bypass mortality rates in Ontario: a Canadian approach to quality assurance in cardiac surgery

Background — This study was conducted to assess the overall mortality rate and the amount of interhospital variation in risk-adjusted mortality rates after coronary artery bypass graft (CABG) surgery in Ontario, Canada. CABG outcomes data are not publicly disseminated in Ontario.

Methods and Results — Clinical risk factors and surgical outcomes were collected on 15,608 patients undergoing isolated CABG surgery between April 1, 1991, and March 31, 1994, at the nine hospitals performing adult cardiac surgery in Ontario. The data were analyzed on the basis of a fiscal year. The overall mortality rate was 3.01%, and the risk-adjusted mortality rate declined from 3.17% in 1991 to 2.93% in 1993. In 1991, one of the nine hospitals had a risk-adjusted mortality rate significantly lower than the provincial average. Otherwise, the hospitals all had risk-adjusted mortality rates within the expected range during the time period of the study. All hospitals performed > 300 CABG procedures in 1992 and 1993, and only 2 of 42 cardiac surgeons performed < 50 CABG procedures in 1993.

Conclusions — The in-hospital mortality rate after CABG surgery in Ontario is low, and the amount of interhospital variation in risk-adjusted mortality rates is no greater than that expected by chance alone. These outcomes are probably attributable to regionalization of CABG surgery and a very low prevalence of low-volume cardiac surgeons in Ontario.