Ablation of atrial fibrillation in the rapid pacing canine model using a multi-electrode loop catheter

OBJECTIVES This investigation details our experience using a loop catheter to ablate atrial fibrillation (AF) in dogs. BACKGROUND Atrial fibrillation is the most common arrhythmia and has significant morbidity. Maintenance of normal sinus rhythm (NSR) after conversion in many patients is still a challenge. METHODS A multi-electrode loop catheter was used to create linear atrial lesions to ablate AF in a rapid atrial pacing model in 29 dogs. Rhythm status was assessed over a six-month recovery period, after which tissue analysis was performed. RESULTS Acute conversion to NSR or atrial tachycardia (AT) was achieved in 90% of cases. Six of 26 conversions occurred after only left atrial (LA) lesions, and two after just right atrial lesions. Sixteen (62%) of 26 lesions that resulted in AF conversion were in the LA, and 11 of these 16 conversions occurred during a lesion connecting the mitral ring to the pulmonary veins. Acute conversion rate was similar with ring and coil electrodes, but AT was more frequent with coil electrodes (63% vs. 31%). At six months 80% of dogs were in NSR, 14% were in AT, and 7% remained in AF. There was an average reduction in P-wave amplitude of 64 ± 26% after power application. Tissue analysis revealed transmural contiguous lesions when final outcome was NSR, and nontransmural/noncontiguous lesions where AF persisted. CONCLUSIONS Multi-electrode loop catheters can create contiguous transmural lesions in either atrium to safely and effectively ablate AF and provide a stable long-term rhythm outcome in this dog model. The left atrium appears to be the dominant chamber that sustains AF. Atrial tachycardia is a frequent acute outcome with coil electrodes.