Arrhythmogenic activity of cardiac muscle in pulmonary veins of the dog: implication for the genesis of atrial fibrillation

Abstract

Objective: Pulmonary veins are important foci of ectopic beats to initiate paroxysmal atrial fibrillation. The purpose of this study were to investigate the electrophysiological characteristics of excitable cells in canine pulmonary veins obtained from healthy and chronic rapid atrial pacing dogs and their responses to cardioactive agents. Methods: Transmembrane action potentials (APs) were recorded from multiple sites of pulmonary veins isolated from 17 healthy dogs and 14 dogs with chronic (6-8 weeks) rapid atrial pacing (780 bpm). Results: In normal superfusate, several types of electrical activities were identified, including silent electrical activity, fast response APs driven by electrical stimulation, and spontaneous fast or slow response APs (with or without early afterdepolarizations). The incidences of AP with an early afterdepolarization (93% versus 41%) was greater in chronic pacing dogs. The spontaneous activities were depressed by beta-adrenoceptor blocker, calcium channel blocker, adenosine and acetylcholine. High frequency (.8 Hz) irregular rhythms occurred spontaneously or were induced by cardioactive agents or electrical stimuli. The incidence of spontaneously occurring tachyarrhythmias was much higher in preparations from chronic pacing dogs (93%) than from control (12%). The tachyarrhythmias were suppressed by sodium channel blocker, potassium channel blocker or magnesium. Conclusions: Pulmonary veins have arrhythmogenic ability through spontaneous activities or high-frequency irregular rhythms. The higher incidence of spontaneously occurring high-frequency irregular rhythms in chronic rapid atrial pacing dogs may account for the increased risk of atrial fibrillation in these dogs.

Electrical Conduction in Canine Pulmonary Veins

“…Application of norepinephrine accelerated the rate of spontaneously active pulmonary vein preparations. Chen et al 16 recorded spontaneously occurring action potentials at the distal end of the myocardial sleeves of pulmonary veins of the dog heart. Spontaneously occurring activity was seen in none of our preparations.…”

“…This is not in contradiction to the study by Cheung 15 because automaticity was absent in his study when the pulmonary vein was electrically coupled to the atrium, as was the case in our preparations. In the study by Chen et al, 16 pulmonary veins were harvested from dog hearts after 6 to 8 weeks of rapid atrial pacing, and preparations were superfused. Differences in the preparations and techniques may well account for the differences in automaticity.…”

Electrophysiology and Arrhythmogenic Activity of Single Cardiomyocytes From Canine Superior Vena Cava

“…3 Our previous studies in multiple cells or single cells have shown that pulmonary veins (PVs) contain cardiomyocytes with or without spontaneous activities, which may underlie the high arrhythmogenic activities of PVs. 10,11 Although clinical electrophysiological study has found that the SVC and PVs may have different electrophysiological characteristics, 12 knowledge about the mechanisms underlying the arrhythmogenic activity of the SVC was limited. Because experiments utilizing intact tissue are complicated by the multiplicity of cell types and complex arrangement of cardiac cells within the tissue matrix, isolation of single SVC cardiomyocytes is important in evaluating the arrhythmogenic activity of SVC.…”

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

“…No entanto, no modelo do cão submetido a pacing rápido crónico, a estimulação simpática induziu atividade repetitiva das VP e contribuiu para iniciar FA 35 . Também a estimulação combinada do simpático e parassimpático pode influenciar as propriedades eletrofisiológicas e aumentar a propensão para FA em cães 16,35 . Os efeitos eletrofisiológicos da atividade autonó-mica reflexa nas aurículas e VP podem assim ter um papel importante na fisiopatologia da FA.…”