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

Abstract

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. We retrospectively analyzed data from nonoperated EA patients and age-matched controls who underwent echocardiography, cardiovascular magnetic resonance imaging, and cardiopulmonary exercise testing to quantify right ventricular (RV) remodeling, dysfunction, and exercise capacity. The relation of these to fRV dyssynchrony was retrospectively investigated. Right ventricular mechanical dyssynchrony was defined by early fRV septal activation (right-sided septal flash), RV lateral wall prestretch/late contraction, postsystolic shortening, and intra-RV delay using two-dimensional strain echocardiography. The SD of time to peak shortening among the fRV segments was calculated as a parameter of mechanical dispersion. Thirty-five EA patients (10 of whom were <18years of age) and 35 age-matched controls were studied. Ebstein anomaly patients had worse RV function and increased intra-RV dyssynchrony versus controls. Nineteen of 35 (54%) EA patients had early septal activation with simultaneous stretch and consequent late activation and postsystolic shortening of RV lateral segments. Intra-fRV mechanical delay correlated with fRV end-diastolic volume index (r=0.43, P<.05) and fRV end-systolic volume index (r=0.63, P<.001). The fRV ejection fraction was lower in EA with versus without right-sided septal flash (44.9±11.0 vs 54.2±8.2, P=.012). The fRV mechanical dispersion correlated with the percentage of predicted peak VO2 (r=-0.35, P<.05). 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.