不同部位起搏对正常心肌复极影响

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。

Effect of different site pacing on normal ventricular repolarization

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.