Importance of evaluating conduction block in radiofrequency ablation for atrial fibrillation

Atrial fibrillation (AF) is the most frequently diagnosed cardiac arrhythmia. Anti-arrhythmic drugs may be used to suppress ectopic foci and interrupt reentry circuits, but are often insufficient to treat recurrent AF and have a number of adverse effects. Alternative therapies, such as catheter and surgical ablation, have been explored. This investigation examines the importance of assessing exit block when performing surgical ablation during beating-heart treatment of AF.

This was an evaluation of pooled data from multicenter prospective results obtained in AF patients who received ablation with a new, irrigated, vacuum-integrated device that creates linear lesions during beating-heart/open-chest or minimally invasive, port-access procedures. Electrocardiogram or Holter data were collected intra-operatively and at 1, 3, 6, and 12 months. Outcomes were also evaluated for patients who were or 'were not' tested for exit block following the ablation procedure.

A total of 93 patients were treated (61 open-chest surgeries, 32 port-access procedures). There were no device-related complications and no operative mortality. At 341 days' average follow-up, 71/86 (83%) patients were free from AF, 66/86 (77%) were in sinus rhythm, and 60/86 (70%) were free from AF and off Class I and III anti-arrhythmic drugs (AADs). At 12 months, 23/23 (100%) patients with exit block confirmed were AF free compared with 13/21 (62%) patients with exit block not tested (p≤0.01, Fisher's exact test); 20/23 (87%) were in sinus rhythm compared with 12/21 (57%) patients with exit block not tested (p≤0.05, Fisher's exact test); and 20/23 (87%) were AF free without Class I and III AADs compared with 10/21 (48%) patients with exit block not tested (p≤0.01, Fisher's exact test). Both open-chest and port-access procedures yielded decreases in left-atrial size from baseline to 6 months' follow-up. Patients undergoing port-access procedures also observed an increase in left-ventricular ejection fraction, which was also significant at 6 months.

Patients in whom exit block was confirmed following an ablation procedure were more likely to have successful clinical outcomes. Since testing for exit block must be performed on a beating heart, total epicardial beating-heart ablation may provide an important treatment for AF, providing intra-operative feedback indicative of long-term outcomes.