Isolated Atrial Segment Pacing. An Alternative to His Bundle Pacing After Atrioventricular Junctional Ablation

Objectives: This study was designed to investigate a practical alternative to His bundle pacing after atrioventricular (AV) junctional ablation by pacing a small area of isolated atrial tissue surrounding the AV node. Background: His bundle pacing is preferred after AV junctional ablation in patients with refractory atrial fibrillation. However, it is technically difficult and not clinically useful at the present time. Methods: This study was conducted in an isolated working swine heart model (n = 5), with real-time imaging capabilities. A small area of atrial tissue surrounding the AV node and the His bundle was isolated using sequential radiofrequency ablation lesions. Results: Complete AV block created by segmental atrial isolation was achieved in 5 of 5 experiments. The isolated atrial segment was bordered by the ablation lines, the tricuspid annulus, and the AV node-His bundle. The AV conduction was characterized using a pacing electrode implanted into the isolated atrial segment. Pacing from the atria, the ventricles, and the isolated atrial segment at different rates confirmed complete bidirectional block between the atria and isolated area, whereas antegrade and retrograde AV nodal conduction between the isolated atrial segment and the ventricles remained intact. Pacing from the isolated area produced minimal changes in systolic left ventricular pressure compared with baseline sinus rhythm (mean -2 mm Hg). Conclusions: Isolation of a small area of atrial tissue surrounding the AV node is feasible by transcatheter radiofrequency ablation. This procedure may be a useful alternative to conventional AV junctional ablation because it can create complete AV block, while in effect permitting the equivalent of His bundle pacing after AV junctional ablation.