Mitral valve replacement combined with coronary artery bypass grafting has been reported as being associated with a higher mortality than either mitral valve replacement or coronary artery bypass grafting alone. Cause of mitral valve disease and severity of mitral regurgitation have been reported as related to mortality. To study the correlation of the cause of mitral valve disease and severity of mitral regurgitation to hospital mortality and long-term survival, we analyzed the results of 135 patients undergoing mitral valve replacement and coronary artery bypass grafting between June 1974 and August 1989. The hospital mortality was 11.8% (16/135). Fifteen preoperative and operative variables were tested for correlation with hospital or late mortality using univariate tests and multivariate regression. Advanced age (greater than 60 years), New York Heart Association functional class, and wall motion score were independently associated with hospital mortality (p less than 0.05). The cause of mitral valve disease and severity of mitral regurgitation were not related to hospital mortality or long-term survival (p greater than 0.05). The follow-up rate was 96.6% for the hospital survivors (115/119). Mean follow-up was 52.6 +/- 4.1 months. There were 35 late deaths. Survival was 91.9%, 89.9%, 78%, and 49.9% at 1, 2, 5, and 10 postoperative years, respectively. Preoperative New York Heart Association functional class and use of catecholamines during the postoperative intensive care period were independently related to late survival (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)