Published Online
on June 23, 2008

A more recent version of this article appeared on August 1, 2008

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Original Article

Atrial Fibrillation Begets Atrial Fibrillation: Autonomic Mechanism for Atrial Electrical Remodeling Induced by Short-term Rapid Atrial Pacing

Zhibing Lu¹, Benjamin J. Scherlag², Jiaxiong Lin³, Guodong Niu², Kar-Ming Fung⁴, Lichao Zhao⁵, Muhammad Ghias², Warren M. Jackman², Ralph Lazzara², Hong Jiang¹ and Sunny S. Po^2,6

¹ Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China;
² Cardiac Arrhythmia Research Institute, Univ. of Oklahoma Health Sciences Center, Oklahoma City, OK;
³ Zhongshan Hospital, Fudan University, Shanghai, China;
⁴ Dept. of Pathology, Oklahoma Health Sciences Center; Veterans Affair Medical Ctr., Oklahoma City, OK;
⁵ Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK

Correspondence: ⁶ E-mail: sunny-po{at}ouhsc.edu

Background—The mechanism(s) for acute changes in electrophysiological properties of the atria during rapid pacing induced atrial fibrillation (AF) is not completely understood. We sought to evaluate the contribution of the intrinsic cardiac autonomic nervous system (ICANS) in acute atrial electrical remodeling and AF induced by six-hour rapid atrial pacing.

Methods and Results—Continuous rapid pacing (1200 bpm, 2x threshold, TH) was performed at the left atrial appendage. Group 1 (N=7): 6-hour pacing immediately followed by ganglionated plexi (GP) ablation; Group 2 (N=7): GP ablation immediately followed by 6-hour pacing; Group 3 (N=4): administration of autonomic blockers, atropine (1 mg/kg) and propranolol (0.6 mg/kg) immediately followed by 6-hour pacing. The effective refractory period (ERP) and window of vulnerability (WOV, in milliseconds), i.e., the difference between the longest and the shortest coupling interval of the premature stimulus which induced AF, were measured at 2x TH and 10x TH at the left atrium, right atrium and pulmonary veins every hour before and after GP ablation or autonomic blockade. In Group 1, ERP was markedly shortened in the first two hours and then stabilized both at 2x TH and 10x TH; however, WOV was progressively widened throughout the 6-hour period. After GP ablation, ERP was significantly longer than before ablation and AF could not be induced (WOV=0) at either 2x TH or 10x TH. In Group 2 and 3, rapid atrial pacing failed to shorten the ERP. AF could not be induced in 6/7 dogs in Group 2 and 4/4 dogs in Group 3 during the 6-hour pacing period.

Conclusion—The ICANS plays a crucial role in the acute stages of atrial electrical remodeling induced by rapid atrial pacing.

Key Words: remodeling • atrial fibrillation • autonomic nerve system

Related Article

Atrial Fibrillation Begets Atrial Fibrillation: Autonomic Mechanism for Atrial Electrical Remodeling Induced by Short-Term Rapid Atrial Pacing

Zhibing Lu, Benjamin J. Scherlag, Jiaxiong Lin, Guodong Niu, Kar-Ming Fung, Lichao Zhao, Muhammad Ghias, Warren M. Jackman, Ralph Lazzara, Hong Jiang, and Sunny S. Po
Circ Arrhythmia Electrophysiol 2008 1: 184-192. [Abstract] [Full Text] [PDF]