Basic/Translational Science -> Whole Animal Electrophysiology and Pharmacology (includes Neurohumoral Modulation) D-PO06 - Poster Session VI (ID 26) Poster

D-PO06-008 - Arrhythmogenic Substrate In The Right Pulmonary Transitional Zone Of Healthy Sheep (ID 637)

 L.A. Gottlieb: Nothing relevant to disclose.


Background: The pulmonary vein transitional zone (PVTZ) is the target for ablation in patients with atrial fibrillation (AF). Failure to permanently isolate the pulmonary veins is not always followed by AF recurrence. Therefore, the role of the PVTZ in AF prevention is not clear.
Objective: To characterize electrophysiological properties in the PVTZ.
Methods: Healthy female sheep (n=14, 2-4 years old) underwent percutaneous transvenous endocardial catheterization following transseptal access to the left atrium. Unipolar electrograms were recorded with a 20 electrode spiral catheter from the proximal and distal right pulmonary vein (RPV). Programmed stimulation with a single premature beat (S1 500ms cycle length) was performed in the proximal and distal RPV. Fractionation time (FT) was defined as the interval between the time of maximum negative slope of first and last deflection in individual electrograms.
Results: Proximal RPV S1-S2 pacing induced atrial arrhythmias (AA) in 10/14 sheep (1-147 premature atrial complexes (PACs)/S2), whereas AA occurred in 2/14 sheep (1-6 PACs/S2) during distal RPV pacing. AA inducibility was 1.4±0.8 and 0.1±0.1 total PACs/S2 decrements in the proximal and distal RPV, respectively (p=0.005). The refractory period was shorter in the proximal than in the distal RPV (187±55 vs 232±55ms, p=0.026). During proximal and distal RPV stimulation, FT was longer in distal RPV than proximal RPV (22.6±2.9 vs 15.7±2.0ms, distal vs proximal, and 26.1±1.8 vs 21.0±2.5ms, respectively; p= 0.015). Also the number of deflections in local electrograms in the distal RPV was higher than in the proximal RPV (p=0.005). Premature S2 stimulation caused increased heterogeneity in activation time compared to S1 stimulation (local range in activation time 11.5±1.2 vs 8.7±0.8ms, S2 vs S1; p=0.051).
Conclusion: The refractory period was shorter in the proximal than distal PV. Programmed stimulation with a single premature beat from the proximal PV but not from the distal PV led to AA. More fractionation existed in distal than in proximal PV. These observations are compatible with a re-entrant mechanism based on myocardial fiber disarray in the PVTZ.