Role of Sympatho-vagal Regulation on Ventricular Arterial Coupling

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Since the heart continues to pump blood throughout the life time, the amount of energy required to support the heart becomes enormous. Although many investigators demonstrated that ventricular coupling with the arterial system is energeticaly efficient, it is not known the role of the autonomic nervous system in the ventricullar arterial coupling. The purpose of this investigation was to elucidate the mcchanism by which the sympathetic system and vagal system affect the ventricular arterial coupling.In the first year, we investigated how the sympathetic system affects ventricular-arterial coupling. In anesthetized, vagotomized dogs, we isolated the carotid sinuses and altered intrasinus pressurc (csp) randomly while measuring end-systolic ventricular elastance (Ees) and effective arterial elastance (Ea). We estimated transfer functions from CSP to Ees and Ea. The transfer function from CSP to Ees was remarkably similar to that from CSP to Ea. This implies that whenever the baroreflex i … More s activated, both Ees and Ea change with a similar time course. Thus, the ratio of Ea/Ees, that is the determinant of efficiency of ventricular ejection, will remain unaltered irrespective of changes in CSP.Since Ea/Ees is set to a point where the efficiency is fairly optimum, this observation indicated that baroreflex adjusts blood pressure while maintaining efficiency of ventricular ejection.In the second year, we investigated how the vagal system affected ventricular arterial coupling. In anesthetized, sympathectomized rabbits, we electrically stimulated the cardiac vagal nerve while measuring Ees and Ea. We then estimated the transfer functions from vagal stimulation to Ees and to Ea. The transfer function from the vagal stimulation to Ees strikingly resembled that from the vagal stimulation to Ea. This implied that the vagal regulation did not alter efficient coupling of the ventricle with the arterial system.We conclude that the autonomic regulation of ventricular arterial coupling takes place so that efficient ventricular ejection is maintained. Less