Effect of Propranolol on Baroreflex Control of Heart Rate in Young Patients with Essential Hypertension

The effect of propranolol on baroreflex control of heart rate was studied in 12 young patients with essential hypertension and was compared with that of 12 age-matched normotensive subjects. Resting heart rate and cardiac index in patients with essential hypertension were significantly higher than those of control subjects (p less than 0.001, p less than 0.01, respectively). The reduction of heart rate and cardiac index after propranolol were significantly greater in patients with essential hypertension than in control subjects (p less than 0.01, p less than 0.05, respectively). In the control state, the baroreflex slope in young patients with essential hypertension was significantly less than that of control subjects (p less than 0.01). After propranolol, the baroreflex slope was significantly increased in control subjects (p less than 0.01), but remained unchanged in patients with essential hypertension. These results suggest, first that the antihypertensive action of propranolol must be due to a mechanism other than the augmented baroreflex function and, second that increased beta-adrenergic activity is not a factor contributing to impaired baroreflex function in young patients with essential hypertension.