心房肌复极的电整复性与阵发性心房颤动发生机制的实验研究

目的 研究在体犬左、右心房肌的电整复性即动作电位时程整复性(APDR),观察其与阵发性心房颤动(房颤)发生的潜在机制.方法 使用单相动作电位技术记录14只犬左、右心房复极达90%的动作电位时程(APD_(90)),并通过S_1S_2程序刺激,观察APDR变化,即每一个舒张间期与刺激后发生心房肌复极APD_(90)的关系,并观察房颤的诱发情况.结果 APD_(90)左心房为(157.4±43.5)ms明显小于右心房(170.9±37.9)ms,P<0.05.心房肌在S_1S_2递减程序刺激下,左心房与右心房具有不同斜率的APDR曲线,左心房的APDR曲线斜率1.3±0.4大于右心房0.9±0.3,P<0.05.进行心房快速起搏S_1S_2刺激时,14只犬中共诱发出18阵房颤,其中左心房刺激发作12阵,明显多于右心房6阵(P<0.05).结论 左、右心房间具有单相动作电位时程的异质性及APDR不均一的复极特性,是诱发折返、发生和维持房颤的基质之一.

Restitution of atrial repolarization and atrial fibrillation in canine atrium

Objective Electrical restitution was believed to be a determinant responsible for the stability of heart rhythm. Although numerous studies focused on the role of action potential duration restitution (APDR) in the initiation and maintenance of ventricular fibrillation (VF), the relationship between atrial APDR and atrial fibrillation (AF) has not been fully understood. This study aims to investigate the characteristics of APDR of left atrium (LA) and right atrium (RA) in canines and the relevance to induction of AF. Methods Monophasic action potential (MAP) was recorded from LA and RA in 14 canines using the MAP recording-pacing combination catheter. APDR, plotted as action potential duration (APD) on the preceding diastolic interval (DI), was assessed by use of programmed stimulation with a single extrastimulus (S_1S_2) at LA and RA. Episodes of AF were recorded and analyzed. Results APD_(90) was significantly shorter in the LA than that in the RA [( 157.4 ± 43.5 ) ms vs. ( 170. 9 ± 37. 9)ms, P < 0. 05]. The mean slope of the APDR curve by S_1S_2 in the LA was significantly greater than that in the RA ( 1.3 ±0. 4 vs. 0. 9 ± 0. 3, P < 0. 05 ). The incidence of induced AF was significantly higher in the LA than in the RA (11/18 vs. 7/18, P < 0. 05). Conclusions The APDR and MAP characteristics are not uniform between atriums, which may be one of the important mechanisms responsible for the initiation of AF. Heterogeneity of APDR between LA and RA might create critical gradients or a dispersion of repolarization and subatrate for re-entrant arrhythmias and vulnerability to AF.