Abstract 1364: Not All Refractory Period Abbreviation Promotes Atrial Fibrillation Equally: A Comparison Between Vagal and Atrial Tachycardia Remodeled Substrates
Background: Vagal (VG) and atrial tachycardia remodeled (ATR) AF substrates share many features: reduced effective refractory period (ERP), increased ERP heterogeneity and some common molecular mechanisms (IKACh enhancement by acetylcholine release in VG, constitutive IKACh enhancement in ATR). This study compared VG and ATR substrates at comparable ERP abbreviation.
Methods: In each of 5 VG dogs, bilateral cervical VG stimulation parameters were adjusted (mean±SD: 3.6±1.7 V and 12.2±1.5 Hz; 0.2 ms) to produce the same mean ERP (at 4 RA and 4 LA sites) as a sex and weight matched ATR dog (RA paced 400 bpm × 7 days). Mean duration of burst pacing induced AF (DAF) and local dominant frequencies (DFs, analyzed by FFT at 240 bipolar electrodes, Fig A⇓) were determined.
Results: Mean ERP was 79±13 ms in VG and 78±13 ms in ATR dogs. DAF was greater in VG than ATR dogs (1056±323 vs 289±510 s *P<0.01; both significantly > control, 43±61 s). Despite matched ERPs, there were significant differences in DF distribution (Fig B⇓): DF was faster (mean DF: 11.8±1.1 Hz VG vs 9.7±1.3 Hz ATR*) and DF variability greater (indicated by SD: 1.8±0.6 Hz VG vs 0.8±0.5 Hz ATR*) in VG dogs. AF drivers reflected by maximum DF zones were adjacent to autonomic ganglia (over RA in 4/5) for VG dogs; in ATR dogs driver zones were less clear and showed variable location.
Conclusions: For a comparable atrial ERP, VG AF is faster and more persistent than AF with an ATR substrate. These results are consist with modeling work suggesting that VG-induced hyperpolarization is an important contributor to AF-maintaining rotor stabilization and acceleration, and indicate important differences between these superficially similar AF substrates.