Effect of epivascular cardiac autonomic nerve stimulation on cardiac function

Background: The cardiac plexus contains sympathetic and parasympathetic cardiac nerves. Our goal was to assess the hemodynamic and functional effects of stimulating the cardiac autonomic nervous system (CANS) at the epivascular surfaces of the cardiac plexus. Although CANS therapy to modulate cardiovascular function has drawn widespread interest, research has focused only on stimulating parasympathetic or sympathetic nerves, not both at once. Methods: Using general anesthesia and an open-chest surgical procedure, 12 dogs received epivascular stimulation of the cardiac plexus. A bipolar electrode was placed between the right pulmonary artery (PA) and the ascending aorta, with the stimulation frequency/pulse width held constant (20 Hz/4 ms) and the voltage varied (10-50 V). Left ventricular (LV) pressure-volume loops and hemodynamic data were recorded with and without stimulation. Results: In all dogs, aortic and LV systolic pressures, maximum rate of change of LV pressure, and LV stroke work increased (p < 0.0001), as did cardiac output (2.9 ± 1.0-0.4 ± 1.0 L/min; p = 0.001), end-systolic elastance (1.2 ± 0.4-1.5 ± 0.5 mm Hg/mL; p = 0.0001), preload recruitable stroke work (30.1 ± 11.0-39.3 ± 7.8 mm Hg; p = 0.003), and LV ejection fraction (p = 0.012). Systemic vascular resistance increased slightly (p = 0.04), and pulmonary vascular resistance decreased (p = 0.01). Mean heart rate and pulmonary arterial, central venous, and left atrial pressures remained unchanged (p > 0.1). Conclusions: In contrast to inotropic drugs, epivascular CANS stimulation induced a significant and selective increase in LV contractility with no increase in heart rate.