Alterations in Electrophysiology and Tissue Structure of the Left Atrial Posterior Wall in a Canine Model of Atrial Fibrillation Caused by Chronic Atrial Dilatation

Min Tang, Shu Zhang, Qi Sun, Congxin Huang
2007 Circulation Journal  
Methods Animals Adult mongrel dogs weighing 30-35 kg were used for the study: 8 control and 9 CDLA dogs. All studies were performed in accordance with the guidelines specified by the institutional animal care and use committee, and the Public Health Service Policy on Use of Laboratory Animals in Wuhan University. Surgical Procedure for the CDLA Model The model has been previously described. 13,14 Preoperative, transthoracic echocardiography (TTE) was performed, the dogs were anesthetized with
more » ... anesthetized with isoflurane and the procedure was monitored with fluoroscopy and TTE. The carotid artery and jugular vein were isolated by a cutdown procedure and under fluoroscopic guidance, a Swan-Ganz catheter was placed in the pulmonary artery via the femoral vein for measurement of pulmonary wedge pressure (PWP). A biopsy forceps catheter (Cordis 502-302L) was placed in the left ventricle (LV) by means of an introducer (Daig Fast-Cath 406181, 30 cm) inserted into the carotid artery in order to cut or damage the mitral valve chordae and thus produce MR. PWP and regurgitant ratio measurements Background Chronic left atrial dilatation (CDLA) is associated with an increased incidence of atrial fibrillation (AF). The electrophysiological functions of the left atrial posterior wall (LAPW) are not well understood. Methods and Results Eight control dogs and 8 with CDLA (developed 6 months after partial mitral valve avulsion) were studied. An electrophysiological study was performed using the noncontact mapping system. The conduction velocity was significantly decreased in the LAPW in the CDLA group. During atrial extrastimulation, a sharp curvature in the activation wavefront became apparent in the LAPW of 6 CDLA dogs, with unidirectional block in 1 dog. The effective refractory periods increased homogeneously throughout the atrium in the CDLA group. AF was much more easily inducible in the CDLA dogs than in the controls. After the onset of AF, the LAPW exhibited the earliest disorganized activity as compared with other sites in the left atrial. In the CDLA dogs, the most extensive interstitial fibrosis was observed in the LAPW. Conclusions Alterations in the electrophysiologic properties and tissue structure of the LAPW were observed in the CDLA dogs. This study supports the idea that the LAPW may play a role in the mechanism of AF induced by CDLA. (Circ J 2007; 71: 1636 -1642
doi:10.1253/circj.71.1636 pmid:17895564 fatcat:mqdclfprjnc47gd4d7jwg2fsli