Effects of pulmonary vein region isolation on inducibility of atrial fibrillation in an acute pig model

Abstract

We studied the effects of en bloc exclusion of the pulmonary veins and left atrial posterior wall on the inducibility of sustained atrial fibrillation in 9 acute pigs. The LA was exposed via a left thoracotomy. Quadripolar electrodes plaques were attached to the RA and the LA posterior wall. Stimulation studies were performed before and after PV region isolation using burst pacing (2sec, 60 Hz). PV region isolation was carried out using endocardial cryoablation with modified CryoCath probes introduced via the LAA. PV region isolation was monitored using pacing and recording of RA and LA electrodes. Before isolation of the pulmonary vein region, LA pacing induced sustained AF. The shortest cycle length varied from 87 to 135 ms with fractionated LA electrograms consistent with LA origin. RA pacing induced non-sustained atrial flutter in three animals with a cycle length that varied from 92 ms to 137 ms. After exclusion, no spontaneous electrical activity was recorded in the excluded PV region in 6 animals. In 3 pigs, there were intermittent narrow potentials at a slow rate. Pacing did not induce atrial fibrillation in the isolated segment but short lived fragmented electrograms of 1 to several beats with short time intervals (see fig). In the non-excluded segment, short lived atrial flutter was induced by right atrial burst pacing in all animals.