Patterns of Neurogenic Involvement in Borderline and Essential Hypertension

Abstract

This chapter Hemodynamics and indices of neurogenic tone are compared in 145 patients with borderline hypertension, 21 patients with essential hypertension, and 86 normal subjects. Some patients with borderline hypertension have an elevation of cardiac output that is fully neurogenic—cardiac output becomes normal after beta-adrenergic and parasympathetic cardiac blockade with intravenous propranolol and atropine. Sequential administration of propranolol and atropine in these patients reveals sympathetic cardiac stimulation and less vagal inhibition that points toward an altered integration of autonomic cardiac control. Analysis by renin status provides further insight. Based on the hemodynamic responses to propranolol and alpha-adrenergic blockade with phentolamine, borderline hypertensives with high plasma renin show evidence of increased adrenergic drive to the heart and resistance vessels. In these patients, the hypertension is entirely neurogenic, because a combined cardiac and vascular autonomic blockade elicits normotension. In borderline hypertensives with low plasma renin activity, there is no evidence of increased sympathetic tone. In mild established essential hypertension renin, categorization allows a similar differentiation. Essential hypertensives with high plasma renin activity have a faster heart rate, which is related to excess beta-adrenergic drive. Plasma norepinephrine concentration in these patients is elevated. Patients with low-renin essential hypertension does not show abnormality.