The prognostic role of left atrial mechanics but not left ventricular function in functional mitral regurgitation

Abstract Introduction When atrial dilatation or ventricular dysfunction underline the development of functional mitral regurgitation (FMR), FMR has been categorized into ventricular and atrial type. Due to limited evidence of surgical correction, majority of patients with FMR were left untreated. We therefore investigated the clinical outcomes related to different phenotypes of FMR and the prognostic factors. Methods Subjects with severe or moderate to severe FMR, diagnosed by transthoracic echocardiography were eligible for this analysis. Three phenotypes of FMR, including atrial, ischemic and ventricular FMR were then classified. The left atrial (LA) strain and left ventricular (LV) global longitudinal strain (GLS) were measured. The study population were followed for a year. Results A total of 298 subjects (mean age 72.3 ± 14.0 years; 68% male) were enrolled, including 165 subjects of ischemic-type FMR (iFMR), 77 subjects of non-ischemic ventricular-type FMR (vFMR), and 56 subjects of atrial-type FMR (aFMR). The baseline characteristics, including age, gender, demography, and morbidities were similar between three groups, but aFMR group had higher LA reservoir strain and better LV GLS. During a mean follow-up duration of 283 days, there were 50 (17%) cases died within the first year. The Kaplan Meier curve analysis showed similar survival rate between three phenotypes of FMR. Body mass index (BMI), systolic blood pressure, diastolic blood pressure, history of myocardial infarction (MI), RV dysfunction, and a lower LA reservoir strain, but not LV GLS were crudely related to one-year mortality. In the multivariable Cox proportional regression analysis, LA reservoir strain was independently predictive of mortality (Hazard ratio for 1% increase and 95% confidence intervals: 0.943, 0.895-0.994). Conclusions Patients with aFMR also have despaired clinical outcomes as patients with vFMR or iFMR. LA reservoir function but not LV systolic function was predictive of worse clinical outcomes. The results may encourage the transcatheter therapy, approved for ventricular-type FMR, for the treatment of aFMR.Kaplan Meier curve analysisMultivariable CPH regression model