Electrical Conduction in Canine Pulmonary Veins

Abstract

Background-Paroxysmal atrial fibrillation in patients is often initiated by foci in the pulmonary veins. The mechanism of these initiating arrhythmias is unknown. The aim of this study was to determine electrophysiological characteristics of canine pulmonary veins that may predispose to initiating arrhythmias. Methods and Results-Extracellular recordings were obtained from the luminal side of 9 pulmonary veins in 6Langendorff-perfused dog hearts after the veins were incised from the severed end to the ostium. Pulmonary veins were paced at the distal end, the ostium, and an intermediate site. During basic and premature stimulation, extracellular electrical activity was recorded with a grid electrode that harbored 247 electrode terminals. In 4 hearts, intracellular electrograms were recorded with microelectrodes. Myocyte arrangement immediately beneath the venous walls was determined by histological analysis in 3 hearts. Extracellular mapping revealed slow and complex conduction in all pulmonary veins. Activation delay after premature stimulation could be as long as 96 ms over a distance of 3 mm. Action potential duration was shorter at the distal end of the veins than at the orifice. No evidence for automaticity or triggered activity was found. Histological investigation revealed complex arrangements of myocardial fibers that often showed abrupt changes in fiber direction and short fibers arranged in mixed direction. Conclusions-Zones of activation delay were observed in canine pulmonary veins and correlated with abrupt changes in fascicle orientation. This architecture of muscular sleeves in the pulmonary veins may facilitate reentry and arrhythmias associated with ectopic activity.

2012 HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Patient Selection, Procedural Techniques, Patient Management and Follow-up, Definitions, Endpoints, and Research Trial Design

“…90,91 One important factor could be the shorter action potential duration (APD) of the PVs vs the atrium 84 due to larger delayed-rectifier K + currents and smaller inward Ca 2+ currents in the PV. 89,92,93 In addition, PVs demonstrate conduction abnormalities that promote reentry due to abrupt changes in fiber orientation as well as Na + channel inactivation by reduced resting potentials due to small I K1 .…”

Distinctive Electrophysiological Properties of Pulmonary Veins in Patients With Atrial Fibrillation

“…A recent study conducted in dogs reported conduction patterns in PVs similar to those described here. 11 The activation delay was correlated with complex fiber arrangement and particularly with abrupt changes in their direction. These decremental conduction properties could therefore be related to anisotropic conduction, 12 with the fractionated venous potentials and associated changes in activation sequence and exits probably correlating with the complex arrangement of venous muscular sleeves reported by pathologists in humans.…”

Modulação eletrofisiológica das aurículas e veias pulmonares: interação da estimulação simpática e parassimpática na inducibilidade de fibrilhação aguda auricular num modelo experimental in vivo

“…Em cães, os circuitos de micro-reentrada, o automatismo e a atividade trigger têm sido apontados como mecanismos associados a ocorrência de arritmias auriculares 28,29 . Hayashi e colaboradores usaram estimulação vagal cervical para indução de FA com bursts de pacing auricular em cães anestesiados 30 .…”