Comparison of three measurements of cardiac surgery mortality for the Northern New England Cardiovascular Disease Study Group

Background. There is no consensus on the optimal period during which to assess death after coronary artery bypass graft ( CABG) surgery. Three measures are commonly used: in- hospital, 30- day, and procedural ( either in- hospital or 30- day) mortality. We used a regional database to calculate the CABG mortality rate using each of these mortality measures. Methods. Data were collected prospectively on 31,592 consecutive isolated CABG surgeries in northern New England between January 1992 and December 2001. These data were linked to the National Death Index to obtain vital status through December 2001, and used to calculate 30- day and procedural mortality rates. Procedural mortality was defined as death occurring either within the hospital setting or within 30 days of the index procedure. Regional registry data were used to calculate in- hospital mortality rates. Results. Mortality rates and their 95% confidence intervals were calculated. In all but one medical center, the in- hospital mortality was the lowest rate, while in all centers the procedural mortality rate was the highest. There were 1,082 deaths captured by the procedural mortality measure. Of these, 927 were included in the in- hospital mortality measure; 956 occurred within 30 days of surgery. Conclusions. Each of the measures studied has its advantages and may be used to assess the mortality outcomes of cardiac surgery. The more important issue other than the specific measure used is our ability to measure and validate it conveniently and accurately in actual practice.