Re-entry Hypothesis Testing Within Pulmonary Vein-atrium As A Mechanism For Sustaining Atrial Fibrillation In Dogs

Background The mechanisms of rapid repetitive discharges from the PV initiatingand sustaining atrial fibirillation (Af) remain incompletely understood. Pulmonaryvein myocardial sleeves (antrum) appear to provide a favorable substrate for re-entryformation.Objectives We investigated the hypothesis that re-entry within pulmonary vein (PV)-atrium may serve as a maintaining mechanism for sustained Af.Methods The electrophysiologic properties of canine atrium were investigated usingmultipolar catheter mapping (normal canines, n=4, group A; AF canines, n=5, groupB). The programmed stimulation was performed in the distal PV, PV- left atrium (LA)junction and LA, respectively. Activation maps of PVs were analyzed from episodesof spontaneous onset of Af and initiation of induced Af by a single extrastimulus. Theeffective refractory period (ERP) of each part was compared and statisticallyanalyzed among three parts in each group and between two groups. Antrum wereablated with Atri cure isolator clamp. The inducing rate of Af and pulmonary veintachycardia (PVT), and the mapping rate of double potential and fragmentedelectrocardiogram were compared and statistically analyzed pro and post isolation ofantrum, p＜0.05 was considered significant differences.Results From the distal PV to antrum, there were significant differences ofERP in the two groups (group A, 94±12ms vs. 105±15ms; group B, 91±11msvs. 102±15ms, p＜0.05), but there were no differences between the antrumand LA in the two groups (group A, 105±15ms vs 102±17ms; group B, 102±15msvs 108±14ms, p＞0.05). Compared to group A, there was a shortening of ERP ofdistal PV and antrum in group B(91±11ms vs 94±12ms; 102±15ms vs 105± 15ms, p＜0.05). From the left atrium to distal PV, there was a graded transition ofelectrophysiologic properties, progressive shorting of Af cycle length during sustainedAf(71.8±3.6ms in PV, 72.4±3.1ms in PV-LA and 83.6±2.7ms in LA). Theinducing rate of Af, PVT, double potential and fractional electrogram on antrum wasa significant difference pro and post intervention of antrum in the group B (p＜0.05).Conclusions Pulmonary veins provide a favorable substrate for re-entry formation.The PV antrum may be crucial to promote re-entry formation and thus antrumintervention might play an important role for a curing way for atrial fibrillation.