不同部位起搏对正常心肌复极影响

Effect of different site pacing on normal ventricular repolarization

目的观察正常心脏不同部位起搏时心室肌复极的变化。方法按文献方法制备带冠状动脉分支的犬左心室楔形心肌块模型,记录心内膜下心肌、中层心肌和心外膜下心肌的跨膜动作电位,同时记录心肌块的整体电活动(容积心电图)。分析不同部位起搏时T波峰末(Tp-e)间期。临床上10例接受射频消融术后的患者,经冠状静脉窦将1根标测电极送至左心室表面静脉分支,另1根电极送达右室心尖部,分别起搏左心室心外膜、右心室心内膜及上述两部位同时起搏,记录心电图并测量Tp-e间期。结果反映心肌跨室壁复极离散的心电图指标Tp-e间期在心外膜刺激(Epi)时最大:(86.56±16.34)ms,其次为内外膜同时刺激(Bi):(76.68±14.89)ms,最小为心内膜刺激(Endo):(55.21±13.86)ms(两两比较,均P<0.01)。而在人体,体表心电图上Tp-e间期在左室心外膜起搏(LV-Epi)(106.48±18.37)ms、双心室起搏(BiV)(99.58±22.53)ms明显较右心室心内膜起搏(RV-Endo)(95.48±13.65)ms延长(P<0.05)。结论左室心外膜参与起搏后会增大心室肌的跨室壁复极差异,可能在心脏再同步化治疗心衰中具有致心律失常性。

Objective To investigate the changes of ventricular repolarization when pacing at different sites of normal heart. Methods According to literature in previous publications,The tissue was cannulated via a native branch of left descending coro-nary artery and perfused with Tyrodes’solution,Transmembrane action potentials from sub-epicardial,mid-myocardial,and sub-endocardial sites were simultaneously recorded by using floating glass microelectrodes. A transmural ECG calculated by subtract-ing the transmural activities from sub-epicardium through the sub-endocardium was recorded concurrently. Twave peak to end in-terval （Tp-e）,which representing myocardial repolarization transmural dispersion was measured and compared between different pacing strategies. In clinic,ten patients without structural heart diseases were examined after they were successfully performed RF-CA for SVT. Two electrodes were located at right ventricular apex endocardium（RV-Endo） and left ventricular epicardium（LV-Epi） retrograde through coronary sinus respectively. 12-lead ECG was recorded synchronously during programmed stimuli at different sites. Results The Tp-e interval was（86.56±16.34）ms （Epi）,（76.68±14.89）ms （Bi）,and（55.21±13.86）ms （Endo）respectively （all P〈0.01）,indicating that simultaneous pacing from Bi and Epi increased the transmural dispersion of myocardial repolarization. In clinic,Tp-e interval when pacing at LV-Epi （106.48±18.37）ms and BiV （99.58±22.53）ms were much longer than that when pac-ing at RV-Endo （95.48±13.65）ms （P〈0.05）. Conclusion LV-Epi pacing might result in enlargement of transmural dispersion of myocardial repolarization shown as the changes of Tp-e intervals,which may be proarrhythmic in cardiac resynchronization therapy in congestive heart failure patients.