ABSTRACT
The methods for atrioventricular (AV) optimization in patients receiving cardiac resynchronization therapy (CRT) are almost universally used for programming the optimal interventricular (V-V) delay.1-6 Conventional M-mode echocardiography for the measurement of left ventricular (LV) dyssynchrony using septal-to-posterior wall motion delay may be unreliable and poorly reproducible.7 Determination of the extent of residual LV dyssynchrony after V-V programming requires more sophisticated echocardiographic techniques such as tissue Doppler techniques (peak velocity time difference, delayed longitudinal contraction score, etc.), three-dimensional (3D) echocardiography, and automatic endocardial border detection.8-12
Contemporary biventricular devices permit programming of the V-V interval usually in steps from +80 ms (LV first) to −80 ms (right ventricle (RV) first) to optimize LV hemodynamics. This design was the result of cogent pathophysiologic considerations that simultaneous activation of the two ventricles for CRT was illogical.13
