Objectives Secondary mitral regurgitation (MR) is negatively related to the prognosis of patients with myocardial infarction (MI). Renin–angiotensin system inhibitors (RASI) may favourably affect left ventricular remodelling and reduce afterload and thereby improve prognosis of secondary MR. The aim of this study was to investigate if use of RASI improves prognosis of patients with MI with secondary MR.

Methods A total of 953 patients with MI were enrolled in this study. Long-term prognosis was compared between patients with MI with no/mild MR (n=657), moderate MR (n=196) and severe MR (n=100). Patients with MI with significant (≥moderate) secondary MR were further divided into those treated with and without RASI. Survival and cardiac-event (all-cause death and congestive heart failure)-free survival were compared.

Results Long-term survival was significantly associated with severity of MR (log-rank, p<0.0001). In patients with significant MR (n=296), RASI was used in 130 patients (44%) and not used in 166 patients (56%). Ejection fraction (47.3±12.2 vs 46.6±13.4%, p=NS) and E/e′ (18.4±8.1 vs 16.5±7.0, p=NS) were similar between the two groups. Kaplan–Meier curves for cardiac-event-free survival demonstrated that use of RASI was associated with better survival (p=0.006) as well as event-free survival (p=0.02). By univariable and multivariable Cox proportional hazard analysis, age (HR 1.046, 95% CI 1.002 to 1.091, p=0.039) and RASI (HR 0.480, 95% CI 0.231 to 0.995), p=0.048) were independent predictors of cardiac events.

Conclusions Secondary MR affects prognosis in patients with MI. Use of RASI may be associated with better long-term prognosis in patients with MI with significant MR.