Optimization of atrioventricular delay by surface electrocardiography during dual chamber pacing

Background Nominal atrioventricular （AV） interval in dual chamber pacemaker （DDD） is not the best AV delay in the majority of patients with atrioventricular block. To find a simple method for optimizing AV delay adjustment, we assessed surface electrocardiography （ECG） for optimizing AV delay during dual chamber pacing. Methods DDD pacemakers were implanted in 46 patients with complete, or almost complete, AV block. Optimal AV delay was achieved by programming an additional delay of 100 ms, to the width of intrinsic P wave or to the interval between pacing spike to the end of P wave on surface ECG. Leit ventricular （LV） end diastolic and end systolic volumes, ejection fraction and diastolic parameters were measured by Doppler echocardiography during both nominal and optimal AV delay pacing.Results Compared to nominal AV delay setting, LV end diastolic volume increased [to （53.2±11.3） ml from （50.2 ± 10.2） ml, P〈0.05], end systolic volume decreased [to （26.1 ± 9.0） ml from （27.9 ± 8.2） ml, P〈0.05] during adjusted AV delay pacing, resulting in an increase in LV ejection fraction [to （68.2±5.3）% from （64.5±4.3）%, P〈0.05]. LV diastolic filling and isovolumic relaxation time were not significantly changed.Conclusion Optimization of AV delay by surface ECG is a simple method to improve LV systolic function during dual chamber pacing.

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

Objective In order to provide the maximum benefit of cardiac resynchronization therapy(CRT),we tried to use an echocardiography method to optimize the atrioventricular and interventricular delay.Methods The study included 6 patients who underwent implantation 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 timevelocity integral(TVI)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 TVI.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 150ms.The optimal AV delay was programmed at 130,120,120,120,150 and 110ms respectively with heart rate corrected,LVFT significantly lengthened and TVI of MR decreased(non-optimal vs optimal AV delay:LVFT:469ms vs 523ms;TVI of MR:16.43cm vs 13.06cm,P<0.05).The optimal VV delay was programmed at 4,4,4,8,12 and 8ms with LV preactivation respectively.Programming the optimal VV delay increased the aortic TVI from 17.33cm up to 21.42cm(P<0.05).In the septal and lateral wall,peak systolic velocities improved from2.70cm/s to 3.02cm/s(P>0.05)and froml.31cm/s to 2.50cm/s(P<0.05)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.

Optimized cardiac resynchronization therapy in patients with congestive heart failure

Heart failure was a major and increasing public health problem, with an almost ＂epidemic＂ increase in the number of patients. Despite recent advances in pharmacotherapy, the prognosis remains poor. Cardiac resynchronization therapy （CRT）, by pacing right and left ventricles, has been proved to improve symptoms and reduce mortality for heart failure patients with cardiac dyssynchrony, However, 20% to 30% of patients did not respond to CRT. The good cardiac synchronicity before CRT and the remaining atrioventficular, inter- and intra-ventricular dyssynchrony after CRT may explain the non-response. New echocardiographic techniques, and in particular tissue Doppler imaging （TDI） analysis, has been proved to be a helpful tool in evaluating cardiac dyssynchrony, as well as in assessing the degree of cardiac resynchronization after biventricular device implantation. So, in this study, we optimized the pacing parameters to determine whether echo-guided optimizing of AV/VV delays would enhance the effect of CRT on cardiac function and synchronicity.