Laterality in Direct and Indirect Inotropic Effects of Sympathetic Stimulation in Isolated Canine Heart.

Abstract

Regulation of heart rate (HR) and cardiac contractility by the sympathetic efferent nervous system is vital for maintaining a stable hemodynamic state under various stresses. The sympathetic regulation of ventricular contractility includes a direct inotropic effect through the innervation on the myocardium and an indirect inotropic effect through changes in HR (forcefrequency mechanism). Although previous studies investigated sympathetic regulation of left ventricular function and HR [1][2][3][4], the load dependency of the indexes of ventricular contractility used in these studies, such as dP/dt (the first derivative of pressure waveform), ejection fraction, and stroke volume, makes it difficult to quantitatively compare the relative contribution of the direct and indirect inotropic effects. On the other hand, left ventricular end-systolic elastance (E es ), which is the slope of the end-systolic pressurevolume relationship, has been shown to be a load-insensitive index of ventricular contractility [5][6][7][8][9]. Although the precise estimation of E es can be achieved in an isolated cross-circulated canine heart preparation, because the heart was denervated during the isolation procedure makes this preparation inappropriate for investigating its autonomic regulation. To overcome this problem, we recently developed a new preparation wherein we isolated the canine heart with functional autonomic nerves [10]. In this preparation, the heart is decentralized, but the sympathetic efferent nerves are preserved for electrical stimulation.The purpose of this study was to evaluate the relative contribution of the direct and indirect inotropic effects on E es in response to right or left sympathetic stimulation by using the isolated cross-circulated canine heart with the functional sympathetic nerves. The results of the investigation indicated that the right sympathetic nerve regulated left ventricular contractility via both the direct inotropic effect and the indirect HR-dependent inotropic effect. In contrast, the left Japanese Journal of Physiology, 51, 365-370, 2001 Key words: left ventricular end-systolic elastance, force-frequency mechanism.Abstract: Although sympathetic nerve stimulation is known to increase ventricular contractility, concomitant increases in heart rate (HR) make it difficult to separate its direct inotropic effect from indirect inotropic effect through a force-frequency mechanism. We stimulated the stellate ganglia in 8 isolated canine hearts with functional sympathetic nerves. NS). In the isolated canine heart, the right sympathetic nerve affected E es by both the direct inotropic effect and the indirect HR-dependent inotropic effect. In contrast, the left sympathetic nerve regulated E es primarily by its direct inotropic effect.

High plasma norepinephrine attenuates the dynamic heart rate response to vagal stimulation

“…The right cardiac sympathetic nerve was exposed through a midline thoracotomy and sectioned, resulting in a decrease in HR of 40 beats/min on average. The right cardiac sympathetic nerve is considered more effective than the left cardiac sympathetic nerve in regulating HR (19,22). Finally, a pair of bipolar stainless steel wire electrodes were attached to the right atrium to record the electrocardiogram for measuring HR.…”

Más allá del sodio: cambios en la dieta y su efecto en hipertensión

“…11 En el corazón, la estimulación simpática se relaciona con hipertrofia e incremento de la contractilidad miocárdica, aumentando el cansancio y los requerimientos de oxígeno. 12 Actualmente, contamos con tres grandes pilares terapéuticos para el control del peso: cambios de estilo de vida (dieta y ejercicio), tratamiento farmacológico y cirugía bariátrica, siendo la combinación de éstos lo indicado para muchos pacientes. Se ha demostrado que la magnitud de la reducción de la PA varía según el método que se utilice para perder peso.…”

Uniformity in dynamic baroreflex regulation of left and right cardiac sympathetic nerve activities

“…The inotropic response may be most accurately assessed by a slope of the end-systolic pressure-volume relationship (E es ), a load-insensitive index of ventricular contractility (25). Electrical stimulation of the right cardiac sympathetic nerve increases E es by a direct inotropic effect through the ventricular innervation and by an indirect inotropic effect through changes in heart rate (HR) (17,20). In contrast, electrical stimulation of the left cardiac sympathetic nerve increases E es mainly through direct inotropic effect.…”