Influence of Sympathetic Nerve Stimulation on Right Ventricular Outflow-Tract Pressures in Anesthetized Dogs

Stellate ganglion stimulation in the anesthetized, open-chest dog consistently resulted in the generation of pressure differences which averaged 20 mm Hg across the infundibular region of the right ventricle. Before stimulation, peak systolic pressures in the sinus and conus were closely matched. Peak sinus pressure showed an average increase of 184 and 162% during stimulation of the left and right stellate ganglia, respectively. Simultaneously, peak conus pressure showed average increases of 88 and 61% during left and right stellate ganglion stimulation, respectively. In addition, the maximal rate of intrasinus pressure development (dP/dt) was usually elevated above conus dP/dt, and this change contributed to the generation of early systolic pressure differences. Cervical vagosympathetic nerve stimulation following atropine administration also resulted in the generation of infundibular pressure differences, but the latter were less marked than those elicited during stellate ganglion stimulation. Elevations in main pulmonary arterial resistance abolished the induced pressure differences by allowing peak conus pressure to rise to the same extent as peak intrasinus pressure. Simultaneous electromagnetic flow recordings of pulmonary arterial blood flow during stellate ganglion stimulation revealed two- to five-fold increases in maximum flow acceleration with relatively little change in stroke volume. Infundibular pressure gradients which developed in early systole were associated with maximum flow changes in the pulmonary artery.