Right Ventricular Electromechanical Dyssynchrony and Its Relation to Right Ventricular Remodeling, Dysfunction, and Exercise Capacity in Ebstein Anomaly

Background Abnormal atrioventricular and intraventricular electrical conduction and dysfunction of the functional right ventricle (fRV) are common in Ebstein anomaly (EA). However, fRV mechanical dyssynchrony and its relation to fRV function are poorly characterized. We evaluated fRV mechanical dyssynchrony in EA patients in relation to fRV remodeling, dysfunction and exercise intolerance. Methods We retrospectively analyzed data from non-operated EA patients and age-matched controls who underwent echocardiography, cardiovascular magnetic resonance imaging (CMR) and cardiopulmonary exercise testing to quantify RV remodeling, dysfunction and exercise capacity. The relation of these to fRV dyssynchrony was retrospectively investigated. RV mechanical dyssynchrony was defined by early fRV septal activation (right-sided septal flash), RV lateral wall pre-stretch/late contraction, post-systolic shortening, and intra-RV delay using 2-dimensional strain echocardiography. The standard deviation of time to peak shortening among the fRV segments was calculated as a parameter of mechanical dispersion. Results Thirty-five EA patients (10 of whom were <18 years of age) and 35 age-matched controls were studied. EA patients had worse RV function and increased intra-RV dyssynchrony versus controls. 19/35 (54%) of EA patients had early septal activation with simultaneous stretch and consequent late activation and post-systolic shortening of RV lateral segments. Intra-fRV mechanical delay correlated with fRV end diastolic volume index (fRVEDVI) (r=0.43, P <0.05) and fRV end systolic volume index (fRVESVI) (r=0.63, P <0.001). fRV ejection fraction (fRVEF) was lower in EA with versus without right-sided septal flash (44.9±11.0 vs 54.2±8.2, P=0.012). fRV mechanical dispersion correlated with percent of predicted peak VO2 (r=-0.35, P <0.05). Conclusions In EA, fRV mechanical dyssynchrony is associated with fRV remodeling, dysfunction and impaired exercise capacity. Mechanical dyssynchrony as a therapeutic target in selected EA patients warrants further study.