The Rho/Rho-kinase Systems Are Involved in Rapid Pacing-induced Changes of Atrial Refractory Period in a Canine Model

Introduction: The Rho/Rho-kinase pathway has been related to various physiological responses of the cardiovascular system. Previous reports have suggested a significant effect of Rho signals on the electrophysiological characteristics of the heart. We hypothesized that the Rho/Rho-kinase system would contribute to the rapid pacing-related change of atrial effective refractory period (AERP). Methods and Results: In 17 dogs, AERP was measured at the right atrial appendage (RAA) and posterior left atrium ( LA) before, during, and after 6-hours rapid atrial pacing at 500 bpm. Saline control (n = 5), verapamil (n = 5), or fasudil (n = 7) were infused throughout the protocol. The shortening of AERP after rapid pacing was abrogated by the administration of verapamil, as reported in previous studies. Furthermore, fasudil (Rho/Rho-kinase inhibitor) influenced the change of AERP in a manner similar to the infusion of verapamil throughout the experiments. Conclusions: Since the AERP was attenuated by fasudil, rapid pacing-related atrial electrophysiological changes might involve the Rho/Rho-kinase pathway.