Modification of cardiovascular responses by propranolol.

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Abstract
Propranolol, a potent beta adrenergic receptor blocker, 0.066 to 0.103 mg/kg, was administered to 8 subjects during right heart catherterization. In 6 there was an increase in pulmonary arterial pressure and total pulmonary resistance. With hypoxia, exercise, or isoprenaline, total pulmonary resistance was greater than before propranolol. Heart rate and cardiac output were decreased after propranolol with variable changes in systemic arterial pressure and stroke volume. A square-wave response to the Valsalva maneuver was noted after propranolol. In 2 subjects mild infundibular pulmonary obstruction was abolished. After propranolol the pulmonary vascular bed functions on a different pressure-flow curve as a result of unopposed pulmonary arterial vasoconstriction.