Ischemic mitral regurgitation is a serious and increasingly common clinical disorder, but at present, little is known of the associated prognostic implications, especially in specific therapeutic subgroups. Over a 6.5-year period beginning January 1, 1981, postinfarction mitral regurgitation was demonstrated ventriculographically in 2,343 (19%) of 11,748 patients having significant coronary artery disease defined at cardiac catheterization. Moderate or severe regurgitation was observed in 381 (3%), and among these patients, four treatment groups were defined: Group I (medical, n = 165), Group II (reperfusion, n = 63), Group III (coronary artery bypass only, n = 94), and Group IV (valve replacement or repair in addition to coronary bypass, n = 59). Multivariable regression analysis of survival data in the overall population and in specific treatment groups was performed with the Cox proportional hazards model. Defined and undefined selection biases precluded formal quantitative survival comparisons among some treatment groups; however, unadjusted and adjusted survival analysis for each group revealed several interesting concepts. First, increasing severity of mitral regurgitation had a progressively negative impact on survival prognosis regardless of treatment. Congestive heart failure, the number of associated disorders, acute presentation requiring cardiac care unit admission, diminished ejection fraction, increasing coronary obstruction, and advanced age all worsened prognosis (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)