Pacemaker shift induced by ryanodine to ectopic atrial pacemaker located close to the atrium-pulmonary vein junction

Abstract

Effects of ryanodine on the activation sequence of rabbit atrial preparations including the sinoatrial node and the surrounding atrial muscle were investigated by extracellular-potential mapping. Under control conditions, the leading pacemaker was located in the sinoatrial node, and the excitation was propagated preferentially to the crista terminalis. Conduction toward the interatrial septum was blocked, and the atrial muscle in the septum was activated by the excitation propagating around the top or bottom of the block line. After treatment with 2 micro M ryanodine, the pacemaker site was transiently shifted toward the septum (to the opposite side of the block line), where the interatrial septum is apposed to the right pulmonary veins. These results suggest that a potential ectopic pacemaker site may exist at the atrium-pulmonary vein junction, which could be unmasked by a modulation of intracellular Ca(2+) handling.