Nature of dual atrioventricular node pathways and the tachycardia circuit as defined by radiofrequency ablation technique

Objectives. A comprehensive electrophysiologic study followed by selective radiofrequency ablation from three sites was performed in patients with atrioventricular (AV) node reentrant tachycardia to better delineate the nature of the tachycardia circuit. Background. We postulated that the retrograde fast pathway is the anterior superficial group of transitional cells and the slow pathway is the compact node with its posterior input of transitional cells. Twenty-three consecutive patients were studied. In nine, the atria could be dissociated from the tachycardia by delivery of an atrial extrastimulus during tachycardia. Methods. Radiofrequency ablation was performed with three approaches. The anterior approach was designed to interrupt the anterior superficial atrial input to the compact node, the posterior approach to Interrupt the posterior atrial input to the compact node and the inferior approach to destroy the compact node itself. Results. Selective ablation of the retrograde fast pathway was achieved in seven patients, six with the anterior and one with the inferior approach. Anterograde fast pathway conduction was not affected, whereas retrograde fast pathway conduction was either abolished or markedly depressed. None had induction of echoes or tachycardia after ablation. Selective ablation of the slow pathway was successful in 13 patients, 1 with anterior, 3 with posterior and 9 with inferior approaches. In these 13 patients, boili anterograde and retrograde fast pathway conduction were not affected, the dual pathway physiology was abolished and the tachycardia was not inducible after ablation. Ablation of both the retrograde fast pathway and the slow pathway occurred with the inferior approach in three patients. Conclusions. We conclude that the retrograde fast pathway is likely to be the anterior superficial group of transitional cells, whereas the slow pathway is the compact node and its posterior input of transitional cells. A barrier seems to exist between the atrium and the tachycardia circuit. In a broad view of the AV node structure, the tachycardia circuit is confined tu the node.