Electrophysiologic Effects of Selective Right versus Left Atrial Linear Lesions in a Canine Model of Chronic Atrial Fibrillation

Mapping of Atrial Fibrillation. Introduction: Long linear lesions have been shown to eliminate atrial fibrillation in animal models, but little is known about the electrophysiologic response in one atrium to lesions in the contralateral atrium. Methods and Results: Twelve dogs with chronic atrial fibrillation were randomized to either right atrial ablation (n = 4), left atrial ablation first (n = 4), or a sham procedure (n = 4). Simultaneous biatrial endocardial mapping was performed before and after three linear lesions were applied at specific points in either atrium, using an expandable ablation catheter. Atrial fibrillation was reinducible after single atrial ablation in each dog and no longer inducible after biatrial ablation in five dogs. At baseline, the mean atrial fibrillation cycle length was longer on the trabeculated (117 ± 15 msec) compared with the smooth right (101 ± 16 msec) or left atrium (88 ± 10 msec; P < 0.01). Single right and left atrial ablation caused a significant cycle length increase in the ablated atrium. Left atrial ablation increased the cycle length on both the trabeculated (121 ± 18 msec vs 137 ± 11 msec; P < 0.05) and smooth right atrium (108 ± 12 msec vs 124 ± 9 msec; P < 0.05). Right atrial ablation, however, had no significant effect on left atrial fibrillation cycle length (82 ± 8 msec vs 86 ± 7 msec). Conclusion: Left atrial linear lesions affect right atrial endocardial activation, whereas right atrial lesions do not affect left atrial activation in a canine model of atrial fibrillation. These findings suggest that the left atrium is the driver during chronic atrial fibrillation in this animal model and may explain the limited success of right atrial ablation alone in human atrial fibrillation.