17. Atrial Fibrillation: Pathophysiology and Epidemiology: 17.1 Chronic Left Atrial Overload in the Goat: Electrophysiological Research

In the research for dilatation induced atrial fibrillation (AF), electrophysiological and hemodynamic investigation of the left atrium (LA) was effectuated in a new animal model of chronic LA overload.

In 12 goats, a thoracotomy was performed to implant a vascular graft between the aorta and LA. In a control group, the graft was ligated. Overload was quantified after chronic instrumentation of the LA with ultrasonic crystals, bipolar sensing/pacing electrodes and a LA pressure catheter. Electrophysiological evolution was regularly evaluated in the conscious goats. “Continuing” AF was the ultimate purpose.

After 28.6±13.9days of overload, LA length increased significantly by 43.4±18.0% and LA pressure mounted from 8.6±6.1 to 27.0±10.4mmHg (p<0.05). Three animals presented prolonged AF, 3 sustained AF (>1hour), and 6 “continuing” AF (ongoing after 1week). Compared with the control group, LA overload enhanced significantly the effective refractory period, but did not result in a significant modification in conduction time or initial cycle length.

Chronic LA pressure/volume overload can induce “continuing” AF in a span of weeks. The increased vulnerability to AF cannot be explained by electrophysiological alterations of the LA.