The Incremental Value of Regional Dyssynchrony in Determining Functional Mitral Regurgitation Beyond Left Ventricular Geometry after Narrow QRS Anterior Myocardial Infarction: A Real Time Three-Dimensional Echocardiography Study

Background: Determinants of functional mitral regurgitation (FMR) severity after acute anterior myocardial infarction (MI) remained unclear. Our aim was to: (1) test whether LV dyssynchrony upon real time three-dimensional echocardiography (RT-3DE) is independently associated with FMR severity; and (2) to investigate the role of regional systolic dyssynchrony index (SDI) in identifying FMR severity. Methods: RT-3DE was successfully performed on 64 consecutive patients following acute anterior MI with a narrow QRS complex (<130 ms) and another 30 healthy volunteers. MR severity was assessed using vena contracta method. SDI was derived from the dispersion of the time to minimum regional volume for all 16 LV segments. Multiple linear regression analysis was used to identify the independent relationship between FMR and SDI with and without multivariate adjustment. Results: The mean LV ejection fraction was 49.6% +/- 11.9% in the MI group. All regional (except apical) and global SDIs were associated with regional LV remodeling and were significantly correlated with FMR even after multivariate adjustment, with midwall SDI being most strongly associated with MR severity (R-2 = 0.55, P < 0.001). Regional midwall SDI superimposed on LV global geometry and mitral leaflet deformation substantially expanded the area under curve in identifying FMR (AUC increased from 0.69 to 0.93, c-statistics: P = 0.041). Conclusions: While both global and regional dyssynchrony following anterior MI were independently related to FMR severity, regional midwall dyssynchrony further added incremental value in predicting FMR severity beyond traditional parameters. This finding provides a new insight into the understanding of FMR after anterior MI and may further potentiate specific therapeutic approaches. (Echocardiography 2011;28:665-675)