Moderate functional mitral regurgitation: difference between atrial and ventricular mechanism of the regurgitation

Abstract

Abstract Background/Introduction In severe functional mitral regurgitation (MR), further distinction of the mechanism of MR in atrial functional MR (aFMR) and ventricular functional MR (vFMR) has shown prognostic importance. However, no data are available on moderate functional MR, whose characteristics and prognosis are largely unknown. Purpose To assess clinical and echocardiographic characteristics of patients with moderate aFMR and vFMR and their potential difference in outcome. Methods Patients with moderate functional MR were retrospectively included. aFMR was defined as isolated mitral annulus dilatation in combination with preserved left ventricular ejection fraction (LVEF≥50%) without ischemic heart disease or LV dilatation. Patients were classified as vFMR when LVEF was reduced, LV was dilated and/or wall motion abnormalities were present. Mitral valve intervention and all-cause mortality were used as combined endpoint. Results In total 474 patients with moderate functional MR (mean age 67 ±12, 57% male) were evaluated, of which 136 (29%) had aFMR and 338 (71%) had vFMR as underlying mechanism. Among the clinical variables, patients with aFMR had more atrial fibrillation (77% vs. 35%; p<0.001), were less symptomatic (NYHA class ≥ III: 6% vs. 18%; p<0.001) and had better renal function (eGFR 73 ±23 ml/min/1,73m2 vs. 65 ±23 ml/min/1,73m2; p=0.005) as compared to vFMR. In the vFMR group, 49% of patients had ischemic heart disease. Among the echocardiographic variables, as expected in aFMR, LVEF was higher (42 ±14% vs. 55 ±13%; p<0.001), while LV volumes (LV end-diastolic volume index 55 ±13 mL/m2 vs. 82 ±38 mL/m2; p<0.001) and E/E’ ratio were smaller (10 ±4 vs. 15 ±4; p<0.001) as compared to vFMR. However left atrial (LA) volume index was similar between both groups (43 ±14 mL/m2 vs. 41 ±18 mL/m2; p=0.271). For the echocardiographic measures of the right heart, significant difference was observed only for TAPSE which was higher for the aFMR group (22 ±4mm vs. 20 ±5mm; p<0.001). During a median follow-up of 74 months [IQR: 46.8-107.0], 132 (30%) patients died and 30 (6%) underwent mitral valve intervention. Event-free survival analysis for the combined endpoint was significantly better for aFMR patients (Figure 1). Based on significant variables from the univariable Cox regression analysis, multivariable Cox regression analysis showed that the mechanism of functional MR (with aFMR being protective as compared to vFMR), age, male gender, impaired renal function, NYHA class, severe LA dilatation and TAPSE were independently associated with the combined endpoint (Table 1). Conclusion In patients with moderate functional MR, aFMR is independently associated with better event-free survival as compared to vFMR. Therefore, clear identification of the mechanism of MR implies a better risk stratification and may be helpful for the management of patients with moderate MR.