Mechanism of Atrial Fibrillation Induced in the Left Atrial Volume-load Model

建立了一种新的心房颤动动物模型，观察了10只杂种犬左心房容量和心房电生理的动态变化。实验犬接受了左开胸左锁骨下动脉至肺动脉分流术。分流术后1周开始左房快速起搏，起搏周期为100 mA，所有动物均表现为左房进行性扩张，并出现严重心力衰竭。10例中有3例在术后早期死亡，1例发生起搏失败。对其余6只动物进行分析。起搏后一周暂停快速起搏，观察到短暂的重复激活。随着时间的推移，重复激活的持续时间延长，所有动物在起搏后4周出现持续性心房颤动(&gt；10分钟)。两个心耳记录到的房颤间期逐渐缩短，且左心耳的间期始终短于右心耳。心外膜标测显示左、右上肺静脉同时向右心房重复激活并伴有递进性传导延迟。容量负荷的左房可引起肺静脉的重复激活和心房心肌的电重构，进一步促进心房颤动的持续。这种与容量负荷左房相关的持续性房颤的临床相关模型将有助于检查房颤的电生理学和非药物治疗的效果。

A new experimental model for atrial fibrillation was established and serial changes in the left atrial volume and atrial electrophysiologies were examined in 10 mongrel canines. The canines underwent a left subclavian artery to pulmonary artery shunt surgery through a left thoracotomy. Left atrial rapid pacing at a cycle length of 100 ma was started 1 week after the shunt surgery.All the animals exhibited progressive dilatation of the left atrium and developed severe heart failure. Three of 10 died in the early postoperative days and 1 developed pacing failure. Remaining 6 animals were subjected to the analysis.A brief period of repetitive activations were observed after a temporal suspension of the rapid pacing one week after the pacing. The duration of repetitive activation prolonged over time and all the animals developed persistent atrial fibrillation (>10 minutes) 4 weeks after the pacing. Atrial fibrillation intervals recorded at both atrial appendages were progressively shortened and the interval in the left atrial appendage was always shorter than at the right appendage. Epicardial mapping of the persistent atrial fibrillation revealed concurrent repetitive activations arising from the right and left superior pulmonary veins that conducted toward the right atrium with progressive conduction delay.A volume load of the LA may provoke repetitive activations in the pulmonary veins and electrical remodeling of the atrial myocardium, and further facilitate the perpetuation of atrial fibrillation. This clinically relevant model of persistent AF associated with a Volume-loaded LA would be useful in examining the electrophysiology of AF and the effects of non-pharmacological therapies.