Cardiac Resynchronization Therapy And AV/VV Delay Optimization For Patients With Heart Failure

BACKGROUND Cardiac resynchronization therapy(CRT),by pacing right and left ventricles,can improve symptoms and quality of life,reverse left ventricle remoding,reduce mortality and admission rate for heart failure patients with cardiac dyssynchrony.In order to enlarge the response rate,identifying potential responders of CRT and directing the pacing site during implantation were important.In addition, to optimize the pacing parameters become available with the development of new devices that enables programming of AV and VV delays.OBJECTIVE In addition to analysis therapeutic efficacy of CRT implantation,we aimed to optimize the pacing parameters and to determine whether echo-guided optimizing of AV/VV delays would enhance the effect of CRT on cardiac function and synchronicity.METHODS The study included 11 patients with chronic heart failure due to dilated cardiomyopathy.They were studied with conventional and tissue Doppler imaging days before implantation.After being proved to be with cardiac dyssynchrony, patients were implanted with CRT.Then,cardiac function and synchronicity were reevaluated in order to optimize the AV and VV delays.First,AV delay was optimized according to the left ventricular filling time(LVFT) and Doppler flow.The optimal VV delay was defined as the interval with maximum aortic velocity time interval (VTI_AO),smallest interventricular delay(IVD) and septum-to-lateral delay in time to peak velocities(△Ts).RESULTS All 11 patients were proved to be with cardiac dyssynchrony.The baseline mean left ventricular ejection fraction(LVEF) was26.82%%,IVD was 58.73ms and△Ts was 80.55ms.All patients were successfully implanted with CRT. Compared with baseline,CRT significantly increase LVEF(32.82%vs 26.82%, P＜0.001) and LVFT(391.73ms vs 344.55ms,P=0.04) and significantly reduced both IVD and△Ts(IVD:48.64 vs 58.73ms,P＜0.01;△Ts:65.37ms vs 80.55ms,P=0.009). Echo-guided optimal AV delay were 123.64ms(80～180ms).Preactivation of the left ventricle was optimal for the remaining 11 patients with VV delay of 10.36ms (4～20ms).Compared with nonoptimal CRT,individually optimized CRT further increased cardiac function and improved cardiac synchronicity,with LVEF increased to 40.09%(P=0.023),LVFT to 445.27ms(P=0.019),VTI_AO to25.23cm(P=0.007), IVD decreased to 32.55ms(P=0.016) and△Ts to 44.91ms(P=0.04).In contrast,there was no significant change in QRS duration(155.45ms vs 157.27ms,P=0.167).CONCLUSIONS CRT with routine pacing parameters contributes to improvements of cardiac function and synchronicity.However,the AV/VV delays' optimization may further enhance the efficacy of CRT.