Usefulness of Left Atrial Reservoir Size and Left Ventricular Untwisting Rate for Predicting Outcome in Primary Mitral Regurgitation

The present study proposed to evaluate whether analysis of cardiac mechanics through speckle-tracking imaging is useful for risk stratification in asymptomatic patients with chronic primary mitral regurgitation (MR). We prospectively enrolled 67 patients (mean age 57 ± 18 years) and followed them over time. MR was mild in 20 patients (30%), moderate in 24 (36%), and severe in 23 (34%). After a mean time of 24.8 ± 17 months, 34 patients (51%) remained asymptomatic, whereas 33 (49%) developed events (19 underwent mitral valve surgery, 9 required hospitalization for acute heart failure, and 5 patients died). Compared to asymptomatic patients, those with events at baseline showed more severe MR, larger and spherical ventricles, diastolic dysfunction, and greater systolic pulmonary arterial pressure. Moreover, patients with events had decreased left atrial (LA) reservoir (p <0.001) and left ventricular (LV) untwisting rate (p <0.001). On univariate Cox regression analysis, effective regurgitant orifice area (p <0.001), vena contracta (p <0.001), systolic pulmonary arterial pressure (p = 0.003), LV end-systolic diameter (p <0.001), E/E' ratio (p = 0.004), LA volume (p = 0.001), LA reservoir (p <0.001), and LV untwisting rate (p <0.001) were associated with an increased risk of events. On multivariate analysis, only LA reservoir (p = 0.013) and LV untwisting rate were independent predictors (p = 0.017) of outcome. Moreover, LA reservoir evaluation significantly improved (p = 0.013) risk stratification compared to recommended parameters. In conclusion, impaired cardiac mechanics is more closely associated than severity of MR with the occurrence of events in asymptomatic chronic primary MR.