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 con trol subjects (p < 0.001, p < 0.01, respectively). The reduction of heart rate and cardiac index after propranolol were significantly greater in paients with essen tial hypertension than in control subjects (p<0.01, p<0.05, respectively). In the control state, the baroreflex slope in young patients with essential hyperten sion was significantly less than that of control subjects (p < 0.01). After pro pranolol, the baroreflex slope was significantly increased in control subjects (p < 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, sec ond that increased β-adrenergic activity is not a factor contributing to impaired baroreflex function in young patients with essential hypertension.
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