Radiofrequency Catheter Ablation of the Atria Reduces Inducibility and Duration of Atrial Fibrillation in Dogs

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Abstract
Background The purpose of this study was to prevent induction of sustained atrial fibrillation (AF) by radiofrequency catheter ablation (RFCA) of the atria in an open-chest canine model. Methods and Results In dogs randomized to acute studies, RFCA of the atria was performed after reproducible induction of sustained AF (lasting >30 minutes) with burst stimulation or premature atrial pacing and perpetuation by low level cervical vagal stimulation or IV infusion of methacholine. Additionally, in four dogs, the long-term effectiveness of RFCA was assessed 7 to 21 days after ablation. Continuous discrete transmural lesions were produced with radiofrequency energy pulses (20 to 40 W for 60 seconds) delivered to five atrial epicardial sites and endovascularly to the coronary sinus wall. RFCA electrically isolated regions of the atria that became dissociated from the nonisolated parts. Atrial RFCA markedly attenuated vagally induced shortening of effective refractory period (ERP) at both isolated and nonisolated test sites located in the left and right atria (P<.001, n=5). RFCA rendered noninducible sustained AF maintained by cervical vagal stimulation. The dose-response curve relating the dose of methacholine required to maintain AF was shifted down and to the right. AF was only inducible with high doses of methacholine. Atrial RFCA reduced the maximal sinus rate and prolonged the corrected sinus-node recovery time (P<.001, n=6). However, RFCA did not affect atrial contractile function, AV-nodal ERP, or AV-nodal or His-Purkinje conduction times. In dogs in the chronic group, normal sinus rhythm and normal AV conduction were preserved and AF was only inducible with a high dose of methacholine. No atrial perforations resulted. Conclusions RFCA in open-chest dogs produces partial vagal denervation and reduces the inducibility of AF.