Determination of the optimal atrioventricular and interventricular delays in cardiac resynchronization therapy

Objective In order to provide ihe maximum benefit of cardiac resynchronization therapy (CRT), we tried to use an echocardiography method to optimize the airioventricular and interventricular delay. Methods The study included 6 patients who underwent implanta-tion of biventricular pacemakers for drug-resistant heart failure. Two-dimensional echocardiography and tissue Doppler imaging were carried out before and after the pacemaker implantation. The optimal AV delay was defined as the AV delay resulting in maximum time-velocity integral (TV1) of transmitral filling flow, the longest left ventricular filling time (LVFT) and the minimum mitral regurgitation (MR). The optimal VV delay was defined as the VV delay producing the maximum LV synchrony and the largest aortic TV1. Results CRT was successfully performed in all patients. After pacemaker implantation, an acute improvement in left ventricular ejection fraction (LVEF) was observed from 26.5% to 35%. Meanwhile, the QRS duration decreased from 170ms to 15()ms. The optimal AV delay was programmed at 130. 120, 120, 120, 150 and 110ms respectively with heart rate corrected, LVFT significantly lengthened and TV I of MR decreased (non-optimal vs optimal AV delay: LVFT: 469ms vs 523ms; TV1 of MR: 16.43cm vs 13.06cm, P0.()5) and froml.31cm/s to 2.5()cm/s (P<().()5) respectively. The septal-to-lateral delay in peak velocity improved from 56.4ms to 13.3ms after CRT (P<0.01). Conclusions Optimization of AV and VV delays may further enhance the efficacy of CRT. However, there was interindividual variability of optimal values, warranting individual patient examination.