Mapping of the catecholaminergic automatic activity from its foci within the pulmonary veins to the left atria in rat

Abstract

Paroxysmal atrial fibrillation (pAF) is triggered by ectopic foci of electrical activities located in pulmonary vein (PV) myocardial sleeves. Previously, we showed in rat that norepinephrine (NE) superfusion induced a catecholaminergic automatic activity (CAA) occurring in repetitive bursts of action potential (AP) in isolated PV strips but not in left atria (LA). This study was realised to characterize the calcium activity induced during the CAA as well as its propagation through PV and LA. Ectopic foci induced by NE were located in both proximal and distal parts of PV. Depending on the preparation, one isolated or several ectopic foci were identified, within the same or in two different PV of the preparation. This could explain the complex aspect of some bursts composed of electrical activities from these different foci. CAA triggered by these foci spread to the LA or remained confined to the PV where it originated. In this case, microelectrode recordings showed that CAA induced DAD-like electrotonic membrane potential oscillations in the LA, far from the PV foci. However, these electrical waves were not associated with calcium oscillations. Moreover, during bursting activity, re-entrant circuits sometimes occured in PV. Ectopic foci triggered by NE in rat PV present similarities with those observed during pAF in human. The conduction of CAA from PV to atria is variable, yet always causing electric oscillations of membrane potential which could be arrhythmogenic.