Abstract 2694: Ionic Mechanism by Which Adenosine Reveals “Dormant” Conduction in Pulmonary Veins
Adenosine (Ado) acutely reconnects “dormant” pulmonary veins (PVs) after RF ablation and is widely used in PV isolation procedures to identify PVs at risk of eventual reconnection.
Purpose. To determine the ionic mechanism of Ado-induced PV reconnection.
Methods. PV and left atrial (LA) action potentials (APs) were recorded with standard microelectrodes (6 dogs), inward rectifier K+ current and INa (5 dogs each) with patch clamp, before and after Ado (1 mM). PVs were isolated with RF in coronary-perfused LA-PV preparations from 11 other dogs, and APs recorded before and after Ado.
Results. Ado abbreviated APD in both PV and LA. Ado hyperpolarized resting membrane potential (RMP, by −2.6±0.3 mV,*P<0.05) and increased dV/dtmax (by 34±10%*) in PV only. Changes in dV/dtmax were not due to direct Ado effects on INa, but correlated with RMP hyperpolarization (r=0.80*). Ado induced larger K+ current (IKado) in PV vs. LA (Fig. A⇓). RF isolated PVs by depolarizing RMP to inexcitability (Fig. B⇓). Ado restored conduction in 5 dormant PVs, but not in 6 non-dormant (ND) PVs. Dormant PVs had significantly more negative RMPs (−57±6, vs −46±5 mV in ND; p<0.001) before Ado, so that after Ado their RMP (−66±6, vs −56±6 mV for ND; p<0.001) sufficed to restore excitability. Ado effects on RMP and conduction were reversible upon washout.
Conclusions. Ado selectively hyperpolarizes RMP in PVs by inducing larger PV (vs. LA) IKado, thus increasing PV dV/dtmax by removing voltage-dependent INa inactivation. Dormant PVs have less severe RF-induced depolarization than ND PVs, allowing Ado to restore excitability by hyperpolarizing them to levels at which significant INa recovery can occur and restore conduction.