Correct the left ventricular dyssynchrony, correct the rocking

The presence of left ventricular (LV) dyssynchrony in heart failure patients has been largely associated with improved outcome and LV reverse remodelling after cardiac resynchronization therapy (CRT).1,2 However, definition of LV dyssynchrony remains controversial. While current guidelines include QRS duration (>120 ms) and morphology [left bundle branch block (LBBB) vs. non-LBBB] as marker of LV dyssynchrony,3 it has been demonstrated that these electrocardiographic parameters do not accurately reflect the amount of LV mechanical dyssynchrony.4,5 Left bundle branch block morphology and QRS ≥140 ms have been associated with high likelihood of response to CRT.6 However, still 30% of patients do not show response. Imaging techniques have provided numerous parameters to characterize LV dyssynchrony. Nevertheless, the only non-randomized study evaluating the accuracy of echocardiographic parameters to predict response to CRT, the Predictors of Response to Cardiac Resynchronization Therapy (PROSPECT) trial,7 showed modest performance of a dozen of echocardiographic parameters of LV dyssynchrony. Advances in three-dimensional (3D) imaging techniques and strain analysis have permitted characterization of …