Abstract
Recent studies have reported parasympathetic ganglia supplying the regions around the sinoatrial node (SAN) are situated in the pulmonary vein fat pad (PVFP). Otherwise, in coronary artery bypass grafting (CABG) without cardiopulmonary bypass, cardiac surgeons expect effective support technique on heart rate. The purpose of this study was to determine the feasibility of inducing sinus bradycardia by stimulating these parasympathetic nerve fibers to the SAN in humans. Nine patients were anesthetized and median sternotomy was performed. Bipolar electrodes were sewn onto PVFP to stimulate parasympathetic nerve fibers to the SAN. PVFP was electrically stimulated with a 4-9 V pulse of 0.1msec and a frequency of 5, 10, 20, or 50Hz. Sinus bradycardia was induced by selective stimulation of the parasympathetic nerve fibers to the sinoatrial node. The response was frequency-dependent up to 20Hz. Heart rate was significantly reduced from 90.1±12.4 to 71.4±15.7 (beats/min) at 20Hz. This technique could be applied for reducing heart beats in CABG without cardiopulmonary bypass. However, there are problems in maintaining of the effect.
