Difference in response of vascular resistance to orthostasis in patients with borderline and sustained essential hypertension.

Abstract

Changes in hemodynamic parameters following 50-degree head up tilt were studied in a population of 78 males, including 30 patients with sustained essential hypertension, 30 patients with borderline hypertension, and 18 normotensive controls of the same age. The increase in vascular resistance following tilt was significantly higher in hypertensive subjects. In patients with sustained hypertension, baseline vascular resistance was significantly higher than in normotensive controls, and it was strongly correlated with its change following orthostasis. In patients with borderline hypertension, baseline vascular resistance was similar to that of normotensive controls and did not correlate with its change following orthostasis. The latter result suggests an abnormality in the autonomic nervous control in patients with borderline hypertension, possibly mediated by cardiopulmonary mechanoreceptors in the low pressure system.