Sinoatrial node pacemaker cell pool dynamics upon synchronization with vagus nerve rhythm

Aim: To reveal the dynamics of sinoatrial node pacemaker cell pools upon synchronization with vagus nerve rhythm through the model of vagal-cardiac synchronization. Materials and methods: Observations were carried out on 10 narcotized cats. The animals were tracheostomized and pump-ventilated, and the pericardium accessed via an open-chest transsternal incision. A device (KELSY scanner manufactured by Elsys, St. Petersburg, Russia) accompanied by a microscope and a video-camera, to visualize the luminescence of excitation processes in the sinoatrial node in a high-frequency electromagnetic field (1024 Hz) was placed in the sinoatrial area of a working heart. Luminescent focus in the sinoatrial node was registered as a peripherally cut end of the vagus nerve was stimulated with bursts of electrical impulses (5 impulses, 2 ms, 20 Hz) from an electrostimulator. Results: Luminescence localized at the entrance of the cranial vena cava was visualized in a high-frequency electrical field in narcotized cats. The luminescent focal area was not homogenous and looked like a number of luminescent pools. Upon vagal-cardiac synchronization caused by the stimulation of a peripherally cut end of the vagus nerve with bursts of electrical impulses, the focus was wide and solid. Conclusion: Here, pacemaker cell dynamics were studied in the feline heart. When vagal- cardiac synchronization was activated, synchronization of the heart with vagus nerve rhythm was accompanied by an increase in the early depolarization area in the sinoatrial area of the feline heart. The mechanisms underlying heart rate synchronization are not clearly defined. Rhythm is achieved through actions of the SA node and the vagus nerve. Our data confirm the vagal- cardiac synchronization model.