Role of Parasympathetic Inhibition in the Hyperkinetic Type of Borderline Hypertension

Abstract

Eleven patients with borderline hypertension and high cardiac output were compared to 16 paid healthy volunteers. Cardiac output, heart rate, and intraarterial blood pressure were determined at rest, after administration of 0.2 mg/kg of propranolol i.v., and after administration of an additional 0.04 mg/kg of atropine. In four additional patients, response to infusion of isoproterenol before and after administration of 0.2 mg/kg of propranolol i.v. was evaluated. Resting heart rate and cardiac output in patients with borderline hypertension were elevated. After propranolol infusion, the values decreased more in the patients with borderline hypertension, but remained significantly elevated. After atropine administration, the difference in cardiac output and heart rate between the two groups disappeared. Consequently, patients with borderline hypertension and hyperkinetic circulation simultaneously exhibit an increase of sympathetic and a decrease of parasympathetic tone. HemodynamicsIT IS NOW well documented that many young patients with borderline hypertension have an increased resting cardiac output.1-6 Heart rate in patients with borderline hypertension also tends to be elevated,4-6 but the reports on that topic are not unanimous.2'3 Recently, a condition of concurrent elevation of heart rate and cardiac output but normal, labile or established high blood pressure has been described under the name of hyperdynamic beta-adrenergic circulatory state.7The mechanism by which the heart rate and blood pressure are elevated in borderhne

Arterial hemodynamics in human hypertension.

“…Adding handgrip exercise to beta blockade further increased resistance but did not increase wave reflections. One explanation for this finding is that handgrip exercise produces a localized increase in resistance (26) (27) found that elevated resting cardiac outputs and heart rates in a group of patients with borderline hypertension were partially normalized after propranolol infusion but were only completely normalized when atropine was added to the beta blockade. More recently, Levenson et al.…”

Isolated Systolic Hypertension in Young People Is Not Spurious and Should Be Treated

“…instead, numerous studies in young adults with borderline hypertension have demonstrated that cardiac output and heart rate are elevated and that isH is the predominant Bp phenotype. [34][35][36][37][38] the elevated cardiac output is believed to be neurogenic, involving both the sympathetic 36,39 and parasympathetic nervous systems. 35 indeed, the weight of evidence suggests marked sympathetic nervous system activation in the early stages of essential hypertension, especially in younger subjects.…”

Sympathetic Activation in the Pathogenesis of Hypertension and Progression of Organ Damage

“…More than 25 years ago, for example, Julius and coworkers 5 showed that the elevated resting heart rate values of borderline-hypertensive subjects were reduced by the intravenous administration of a ␤-blocking drug (propranolol) to a more marked degree than the lower heart rate of normotensive controls, suggesting that in the early hypertensive stage, cardiac sympathetic drive is enhanced. They further showed that after the subsequent intravenous injection of a muscarinic receptor antagonist (atropine), the increase in heart rate was less in borderlinehypertensive than in normotensive individuals, supporting the concept that at the cardiac level, an enhanced sympathetic drive combines with a reduced parasympathetic one to make the abnormality of neural cardiac control of borderline hypertensives a composite one.…”