不同部位左心室内膜与外膜起搏对心力衰竭心脏的电生理作用差异

Impacts of endocardial and epicardial left ventricular pacing at different sites on electrophysiology in dog with heart failure

目的 评估左心室不同部位心内膜与外膜起搏对心力衰竭（心衰）犬心脏的电激动同步性以及复极离散度的影响及其差异.方法 12只比格犬,体重（12.5±1.7）kg.使用随机数字法平均分为2组（正常组和心衰组）.利用右心室心尖部快速起搏制作慢性心衰模型.左心室放置64极篮状电极导线进行电生理标测.通过左心室不同部位起搏（心底部心内膜与心外膜,心尖部心内膜与心外膜）记录并测量体表12导联心电图的QT间期、T波峰点与T波下降支最大斜率处切线与等电位线交点（Tp-e）间期,同时测定左心室心内膜整体激动时间以及各篮状电极记录的激动恢复间期及其复极离散度.结果 基础状态下,与正常心脏相比,心衰组QT间期、T波顶点与T波终点之间的时限Tp-e间期以及激动恢复间期均延长（P＜0.05）.心衰组中,与左心室心内膜起搏相比,相同部位的心外膜起搏时的QT和Tp-e间期均显著延长[QT：心底部（270±13）ms对（255±15）ms,（P＜0.01）;心尖部（275±12）ms对（257±11）ms,（P＜0.01）;Tp-e：心底部（50.2±8.3） ms对（42.7±4.5） ms,（P＜0.01）;心尖部,（52.9±10.1）ms对（45.6±9.3）ms,（P＜0.01）].心室激动恢复间期离散度无论在左心室心内膜还是在心外膜,近心底部起搏时较近心尖部起搏时显著减小.[心内膜起搏（4.1±0.5） ms对（5.8±0.7）ms,（P＜0.05）;心外膜起搏（4.7±0.6） ms对（6.2±0.9） ms,（P＜0.05）].在心衰心脏,左心室心外膜起搏时,左心室整体心内膜平均激动时间较心内膜起搏时明显延长（42.9±5.9）ms对（26.1±4.0）ms,（P＜0.001）].结论 左心室心内膜起搏较心外膜起搏有更好的心脏激动电同步性.心衰后,左心室心外膜起搏较心内膜起搏可致更长的复极时间以及更大的复极离散度.本研究结果提示左心室心内膜起搏较心外膜起搏可产生更好的电生理效应,有可能降低心衰心脏再同步治疗时因心外膜起搏促发室性心律失常的发生率.

Objective To evaluate the impacts of endocardial and epicardial left ventricular （LV） pacing at different sites on cardiac electrical synchrony and dispersion of refractoriness in heart failure （HF） dogs.Methods Twelve beagles （12.5 ± 1.7） kg were randomly divided into two groups （normal and HF group）.HF was induced by rapid pacing at right ventricular apex.A 64 multi-electrodes basket catheter was placed in LV for electrophysiological mapping.QT interval and Tp-e interval from12-leads ECG were measured during pacing at different sites （LV endocardium and epicardium at base and apex respectively）.The entire activation time of LV endocardium was used to evaluate cardiac electrical synchrony.The dispersion of refractoriness was respectively calculated by Tp-e interval of ECG and by activation recovery intervals （ARI） measured from 64 unipolar electrodes.Results Compared with normal group,QT interval,Tp-e interval and ARI were significantly prolonged at baseline in HF group（P＜0.05）.Compared with LV endocardial pacing,epicardial pacing induced significant prolongations of QT interval and Tp-e interval in HF group （QT：pacing at the base （270± 13） ms vs.（255± 15） ms,（P＜0.01） ; pacing at the apex （275± 12） ms vs.（257± 11） ms,（P＜0.01） ; Tp-e：pacing at the base （50.2±8.3） ms vs.（42.7±4.5） ms,（P＜0.01） ; pacing at the apex （52.9± 10.1） ms vs.（45.6±9.3）ms,（P＜0.01）.Comapred to pacing at LV base,the dispersion of ARI during pacing at LV apex was increased by 41％ when pacing LV endocardium （4.1 ±0.5）ms vs.（5.8±0.7）ms,（P＜0.05） and 32％ when pacing LV epicardium （4.7±0.6）ms vs.（6.2±0.9） ms,（P＜ 0.05） in failing hearts.In HF group,the entire activation time of LV endocardium was significantly lengthened by 39.5％ during pacing at LV epicardium compared to endocardium （42.9±5.9）ms vs.（26.1±4.0） ms,（P＜0.001）.Conclusion LV endocardial pacing exhibited more benefits to cardiac electrical synchrony than epicardial pacing.LV epicardial pacing caused a longer repolarization time and a greater dispersion of refractoriness compared to endocardial pacing in HF group.The results of this study indicated that LV endocardial pacing other than epicardial pacing can produce better electrophysiological effects,which could reduce the incidence of ventricular arrhythmias triggered by LV epicardial pacing in cardiac resynchronization therapy.