Abstract 17702: Mechanism of Differential Effectiveness Between Pharmacological Strategies to Reveal Dormant Conduction after Successful Pulmonary Vein Isolation: Isoproterenol, Adenosine or the Combination?
Introduction: Atrial fibrillation (AF) recurs in ∼30–40 % of patients after a single pulmonary vein (PV) isolation (PVI) procedure. Temporary block that recovers over time (”dormant conduction”) between PV and left atrium (LA) often explains AF recurrence. Adenosine (Ado) or isoproterenol (Iso) are sometimes used clinically to reveal dormant conduction and guide additional ablation.
Purpose: This study assessed differential efficacy of Ado and/or Iso to reveal dormant conduction.
Methods: In 25 patients with AF undergoing PVI, dormant conduction in 100 PV was sequentially assessed in response to iv Ado, followed by Iso infusion, and finally Ado during Iso infusion. PV and LA action potentials were recorded in 10 dogs, before and after 1 mM, 1 µM Iso, or 1 µM Iso+1 mM Ado. In coronary-perfused LA-PV preparations from 33 dogs, PVs were isolated by radiofrequency ablation. After PVI, resting membrane potential (RMP) from PV cells was recorded before and after 1 mM Ado (n=15), or 1 µM Iso (n=8), or 1 µM Iso+1 mM Ado (n=10).
Results: Clinical PVI was successful in all 100 PV, with dormant conduction in 31. Sensitivity for DC was: Iso 10 %; Ado 87 % (p < 0.001 vs Iso); Iso+Ado 100% (p=0.13 vs Ado). In PV cells, but not in LA cells, Iso significantly depolarized RMP (by a mean of −4.8±3.1 mV, *p<0.05) and Ado repolarized the RMP (fig A). In vitro, dormant conduction in PVs was revealed with Ado (53%) and Ado+Iso (60%), but not with Iso alone (p<0.05). Radiofrequency lesions produced PVI by depolarizing RMP, causing inexcitability. After ablation, both Ado and Iso hyperpolarized RMP, but Ado-induced changes were greater, with no significant differences when Iso was added to Ado (fig B)
Conclusions: Ado is superior to Iso in revealing dormant PV clinically and experimentally, due to greater Ado-induced hyperpolarization. No significant additional benefit of injecting Ado during Iso infusion was noted.
- © 2010 by American Heart Association, Inc.