The purpose of this study is threefold: first, to ascertain whether there are differences between mortality rates associated with coronary artery bypass graft (CABG) surgery in Ontario hospitals that perform such surgeries; second, to test whether the aggregate CABG mortality rate in Ontario is changing; and, third, to test whether the aggregate CABG mortality rate in Ontario is different than the aggregate CABG mortality rate in US states for which comparative data are available.

We find considerable hospital-by-hospital variation in risk-adjusted mortality rates in Ontario. Over the period of 2002/2003 to 2004/2005, the University of Ottawa Heart Institute and St. Mary’s General Hospital were found to have the lowest risk-adjusted mortality rates in Ontario, while Sunnybrook and Women’s College Health Sciences Centre and Anonymous Hospital 104 were found to have the highest rates in Ontario. According to the comparison of mortality rates associated with CABG in Ontario and 32 US states, patients seeking to minimize risk of death would be better off having surgery in all but five of the 32 identified US states in preference to Ontario in 2004.