Background: The aims of this study were to assess the ability of several echo measures of dyssynchrony to predict CRT response and to characterize the global effect of CRT. Hypothesis: We hypothesized that after CRT there would be significant reductions in mechanical dyssynchrony in all 3 orthogonal planes of cardiac motion and that those patients with significant dyssynchrony prior to implant would have the best echocardiographic response. Methods: Standard echocardiograms were performed pre-CRT and post-CRT (138 ± 63d) in 70 heart failure patients. Longitudinal dyssynchrony was calculated as the standard deviation (SD) of time to peak systolic displacement and velocity of 12 segments from 3 apical views. Using midventricular short axis views and speckle-tracking methods, the SD of time to peak radial and circumferential strain in 6 segments were calculated. Cardiac resynchronization therapy echo responsewas defined as ≥ 15%decrease in left ventricular end-systolic volume. Results: Cardiac resynchronization therapy significantly improved systolic function in the longitudinal, radial, and circumferential planes. The CRT echo response rate was 57%. Echo responders (CRTR) had significantly (P< .05) more dyssynchrony at baseline as compared to nonresponders (CRTNR). Cardiac resynchronization therapy significantly (P <.05) reduced longitudinal and radial, but not circumferential, dyssynchrony in CRTR. Dyssynchronywas unchangedin CRTNR. Receiver-operatorcharacteristic (ROC) curve analysis indicated significant, but modest sensitivity and specificity for longitudinal and radial intraventricular dyssynchrony and for interventricular dyssynchrony. Combining radial and longitudinal dyssynchrony measures improved positive prediction of CRT response. Conclusions: Cardiac resynchronization therapy improves left ventricular function in 3 orthogonal planes of motion. Longitudinal, radial, and interventricular dyssynchrony modestly predict reverse remodeling.