Orthostatic hypotension due to autonomic dysfunction--different therapeutic effects of propranolol.

In two patients with orthostatic hypotension, due to autonomic dysfunction, hemodynamic changes induced by the assumption of erect position have been evaluated before and during chronic propranolol treatment. Under control conditions, the change in posture induced in Patient 1 a fall in systolic and diastolic blood pressure by 51.4 and 30.7%, respectively. Cardiac output was reduced by 26.8% and systemic vascular resistance by 23.3%. During propranolol treatment, systolic pressure decreased only by 28% and diastolic pressure by 7.7%. The decline in systemic vascular resistance on standing was abolished, while the reduction in cardiac output remained unmodified. In Patient 2, symptoms of orthostatic hypotension were related to marked decrease in systolic blood pressure, the diastolic pressure remaining unchanged. Moreover, systemic vascular resistance increased and, thus, orthostatic hypotension was exclusively dependent upon the severe fall in cardiac output on standing. As a consequence, propranolol failed to control orthostatic hypotension in this patient. These data suggest that when orthostatic hypotension is secondary to failure in peripheral vasoconstriction, propranolol may act beneficially. When it is secondary to a fall in cardiac output, beta-blockade is ineffective.