In 21 rabbit heart preparations, posteroseptal ablation did not eliminate the slow pathway, but slowed ventricular rate by reducing AV nodal bombardment via posteroanterior intra-atrial block.
Does posteroseptal ablation slow ventricular rate during atrial fibrillation by eliminating the slow pathway in rabbit heart preparations?
Posteroseptal ablation slows ventricular rate during AF by reducing AV nodal bombardment via intra-atrial block, not by eliminating the slow pathway.
BACKGROUND: Posteroseptal ablation of the atrioventricular node (AVN) has been proposed as a means to slow the ventricular rate during atrial fibrillation (AF). The suggested mechanism is elimination of the AVN "slow pathway." On the basis of the unpredictable success of the procedure, we hypothesize that, in fact, the slow pathway is preserved. Therefore, the slowing of the ventricular rate results from reduced bombardment of the AVN. METHODS AND RESULTS: In 8 rabbit heart atrial-AVN preparations, cooling of the posterior and/or the anterior AVN approaches revealed nonspecific effects on the slow and fast pathway portions of the AVN conduction curve. In 13 other preparations, simulated AF during posterior cooling (n=6) prolonged the His-His (H-H) intervals but did not reveal specific slow pathway injury. In the remaining 7 preparations, AF was applied before and after posteroseptal surgical cuts. During AF with posterior origin, the cuts resulted in longer mean H-H along with slowing of the AVN bombardment rate. However, there was no change in the minimum observed H-H, suggesting an intact slow pathway. During AF with anterior origin, the mean and the shortest H-H remained unchanged before and after the cuts in all preparations. This was associated with the maintenance of high-rate AVN bombardment. CONCLUSIONS: Posteroseptal ablation does not eliminate the slow pathway. Ventricular rate slowing can be obtained if the ablation procedure results in a posteroanterior intra-atrial block leading to a reduction of the rate of AV nodal bombardment.
Garrigue et al. (Tue,) conducted a other in Atrial Fibrillation (n=21). Posteroseptal ablation (simulated via cooling or surgical cuts) vs. Baseline (before cuts) or anterior origin AF was evaluated on His-His (H-H) intervals and AVN bombardment rate. In 21 rabbit heart preparations, posteroseptal ablation did not eliminate the slow pathway, but slowed ventricular rate by reducing AV nodal bombardment via posteroanterior intra-atrial block.