Effects of cardiac sympathetic nerve stimulation on the left ventricular end-systolic pressure-volume relationship and plasma norepinephrine dynamics in dogs.

Abstract

The effects of cardiac sympathetic nerve (CSN) stimulation on the left ventricular end-systolic pressure-volume relationship (ESPVR) and plasma norepinephrine (NE) concentration in arterial blood were studied in dogs. In 12 anesthetized and open-chest dogs, left ventricular pressure and volume were measured simultaneously with a microtip catheter and a conductance catheter, respectively. The ESPVR values were constructed from pressure-volume loops during a brief occlusion of the inferior vena cava before and after a 40-sec train of electrical CSN stimulation. The slope (Emax) of the ESPVR line was significantly greater after CSN stimulation than before CSN stimulation (p < 0.05) for both right and left CSN stimulation. The increased Emax values after right and left CSN stimulation were not significantly different from each other. In 5 dogs, time courses of Emax, left ventricular systolic pressure, heart rate, and plasma NE concentration after CSN stimulation were studied. Left ventricular systolic pressure and heart rate returned to the baseline more rapidly than Emax and arterial plasma NE concentration. There was a positive, linear correlation between Emax (y) and arterial plasma NE concentration (x), shown as y = 3.3 x 10(-3)x + 3.1 (n = 30, r = 0.86, p < 0.05). These results imply that cardiac contractile enhancement is reflected in arterial plasma NE concentration in conditions in which CSN is activated.