心房肌的复极与阵发性心房颤动发生机制的实验研究

Paroxysmal atrial fibrillation and repolarization differences between canine right and left atrium

目的 对在体犬左、右心房肌的复极时间进行研究 ,探讨阵发性心房颤动 (房颤 )发生与维持的潜在机制。方法 记录基础心律、非程序刺激及早搏刺激 (SR、S1 、S2 )时 1 4只犬左、右心房的单相动作电位 (MAP)和有效不应期 (ERP) ,测量每个动作电位的幅度和动作电位时程 [复极达90 %、80 %、5 0 %时的动作电位时程 (ms,APD90 、APD80 、APD50 ) ]。并在记录过程中同时观察房颤的诱发情况。结果 记录满意MAP信号 1 2例 ,共标测 2 6点 (右房 1 7点 ,左房 9点 ) ,MAP振幅平均(6 98± 1 76 )mV ,左心房APD90 和APD50 小于右心房 [(1 5 7 4± 4 3 5 0 )ms比 (1 70 9± 37 9)ms ,P <0 0 5 ;(88 4± 1 9 1 )ms比 (1 0 0 1± 2 1 2 )ms,P <0 0 5 )。其中左房刺激发作 38阵 ,明显多于右房 2 3阵 (P <0 0 5 )。由左房诱发房颤的早搏的偶联间期明显比在右房诱发的短 (P <0 0 5 )。起源于左房的房颤的早搏参数小于起源于右房的 (P <0 0 5 )。结论 左、右心房间具有MAP的异质性的复极特性 ,是诱发折返、发生和维持房颤的基质。

Objective To explore the potential mechanisms of the occurrence and maintenance of paroxysmal atrial fibrillation (PAF) by investigating repolarization time in canine right and left atrium using monophasic action potential (MAP) technique. Methods MAP amplitude and effective refractory period were recorded from left atrium (LA) and right atrium (RA) in 14 canine during sinus rhythm and atrial pacing at a basic cycle lengths of 300 ms with extrastimulus S 2 application. The amplitude and action potential duration (APD) of each action potential was also measured at 90%, 80% and 50% of repolarization (APD 90 , APD 80and APD 50 , ms). In addition, episode of PAF were recorded. Results Twelve casesof MAP were recorded satisfactorily at 26 detection points, being 17 at RA and 9 at LA. The average MAP amplitude was (6.98±1.76) mV. APD 90and APD 50were significantly shorter in LA compared to the RA [(157.4±43.5) ms vs. (170.9±37.9)ms for APD 90 , P<0.05; (88.4±19.1) ms vs. (100.1±21.16) ms for APD 50 , P<0.05)]. In total, 51 episodes of PAF were induced in 14 canines. Thirty eight episodes of PAF were induced in the LA, which were more than that in the RA (23 episodes of PAF, P<0.05). The mean coupling interval of premature beats of AF initiated from the LA was significantly shorter than that from the RA (P<0.05). The mean premature index of premature beats from the LA was also significantly lower than that from the RA(P<0.05). Conclusions The atrium plays a central role in the initiation of AF by serving as a substrate for generators of fibrillatory activity. Heterogeneity of MAP between LA and RA creates critical gradients or a dispersion of repolarization and subatrate for reentrant arrhythmias and vulnerability to fibrillation.