Chronic left atrial volume and pressure overload in the goat: a new model of sustained atrial fibrillation

Purpose: The relationship between left atrium (LA) dilatation and atrial fibrillation (AF) has been extensively proved. The aim of this study was to develop an animal model of sustained AF, induced by controlled chronic left atrial overload. Methods: In 12 goats, a left thoracotomy was performed to implant a 8ram vascular graft (gore-tex ®) between the thoracic aorta and the LA. Intra operative atrial overload was monitored by volume and invasive pressure measurements. The LA was chronically instrumented with ukrasonic crystals and bipolar sensing/pacing electrodes. LA dilatation and electrophysiology were regularly evaluated in the conscious goats and compared with a control group with a non-functional shunt. Sustained AF (1 week) was the ultimate purpose. Anew invasive LA pressure was measured ahead of sacrifice. Results: Operatively there was manifest LA overload with calculated volume augmentation of 59.34-42.2% (from 42.3 to 67.4 mm 3, p<0.05) and mean pressure elevation from 9.24-6.9 mmHg to 18.04-8.5 mmHg (p<0.05). One animal was lost during follow up. At sacrifice (324-9.7 days), shunt patency was confirmed in 9 animals. In those, mean LA pressure was 204-7.8 mmHg (ns) and LA dilatation 104.0 mm 3 (p<0.05). AF duration increased significantly from 4.74-4.9 sec (day 0) to 1134-82.3 hours (p<0.05) after 16.14-6.9 days of open shunt. SIX animals presented sustained AF. In the control group, AF duration changed not