This record contains partial raw data related to the article "Prognostic Impact of Extra–Mitral Valve Cardiac Involvement in Patients With Primary Mitral Regurgitation" OBJECTIVES The aim of this study was to evaluate the prognostic impact of the presence of extra–mitral valve cardiac involvement (including known risk factors but also severe left atrial [LA] dilatation and right ventricular [RV] dysfunction) in a large multicenter study of patients with primary mitral regurgitation (MR). BACKGROUND In patients with severe primary MR, the indication for surgery is currently based on the presence of symptoms, left ventricular dilatation and dysfunction, atrial fibrillation, and pulmonary hypertension. METHODS Patients with severe primary MR undergoing surgery were included and categorized according to the extent (highest) of cardiac involvement: group 0, no cardiac involvement; group 1, left ventricular involvement; group 2, LA involvement; group 3, pulmonary vasculature or tricuspid valve involvement; or group 4, RV involvement. The outcome was all-cause mortality. RESULTS A total of 1,106 patients were included (mean age 63 12 years, 68% male). In total, 377 patients (34%) were classified in group 0, 239 (22%) in group 1, 213 (19%) in group 2, 180 (16%) in group 3, and 97 (9%) in group 4. Kaplan-Meier curve analysis revealed significantly worse survival (log-rank chi-square ¼ 43.4; P < 0.001) with higher group. On multivariable analysis, age, male sex, chronic obstructive pulmonary disease, kidney function, and group of cardiac involvement were independently associated with all-cause mortality. For each increase in group, a 17% higher risk for all-cause mortality was observed (95% CI: 1.051-1.313; P ¼ 0.005) during a median follow-up time of 88 months. CONCLUSIONS In patients with severe primary MR, a novel classification system based on extra–mitral valve cardiac involvement may help refine risk stratification and timing of surgery, particularly including severe LA dilatation and RV dysfunction in the assessment.