兔R-on-T室性早搏的时程特征与致心律失常易损窗的关系

目的观察动作电位时程异质性如何影响致心律失常易损窗,以及了解R-on-T室性早搏的时程特征与单向传导阻滞及折返激动易损窗的关系。方法采用冠状动脉灌注兔左室楔形组织块标本,同步记录内、外膜侧心肌细胞动作电位和跨壁心电图。内、外膜侧动作电位时程(APD)的差值(△APD)反映了心室壁跨壁异质性。对标本施加基础刺激(S1),刺激周长分别为2000,1000,500ms。每10次S1后施加S2。S1S2间期以1ms的步长递增,诱发单相传导阻滞和室性心律失常,并分别测量致单向传导阻滞及折返激动易损窗。结果引起单向传导阻滞的易损窗大于产生折返激动的易损窗,当进一步加大复极离散性时才可能引发折返激动。S1刺激诱发室性心动过速时,其R-on-T早搏的时程明显较单纯引起一次心室激动增宽(70.0±15msvs56.1±11ms,P<0.001)。结论单向传导阻滞及折返激动的易损窗与S1刺激所引起心室复极异质性增大有关。R-on-T室性早搏只有在更大的复极梯度状态下,才可能诱发折返激动和室性心动过速、心室颤动。

The relationship between time interval of R-on-T ventricular premature beat and vulnerable window of arrhythmogenesis in rabbit model

Objective To observe how the action potential duration(APD) heterogenieity(△APD) affects the vulnerable window(VW) of arrhythmogenesis and the relationship between time interval of R-on-T ventricular premature beat and the VW of nuidirectional conduction block or reentrant excitation.Methods Floating microelectrodes were used to record transmembrane action potential simultaneously from epicardial and endocardial sites in isolated arterially perfused rabbit left ventricular wedge preparation.A transmural ECG was recorded concurrently.After giving 10 times S1 with the basic cycle lengtn(BCL) 2 000,1 000,and 500ms,the S2 was fired at an increment of S1S2 interval 1ms to test the VW.Results The results showed that the longer the BCL,the larger the △APD.The initiation of unidirectional conduction block by S2 was earlier than that of reentry,which means that VW was larger for inducing unidirectional conduction block than that for inducing reentry.Comparing the time interval of R-on-T ventricular premature beat between induced and no-induced ventricular tachycardia,the data showed the later one was significantly wider than the previous one(70.0±15 ms vs 56.1±11 ms,P<0.001).Conclusions The VW of unidirectional conduction block or reentrant excitation is related to the ventricular repolarization heterogenieity induced by S1.The time interval of R-on-T ventricular premature beat in ECG reflects the ventricular repolarizing greadent caused by S2.And a great refractory barrier is needed for reentrant excitation.