Mechanisms governing the postural response and baroreceptor abnormalities in chronic congestive heart failure: effects of acute and long-term converting-enzyme inhibition.

We assessed the hemodynamic and hormonal response to tilt and the baroreceptor response in 12 patients in sinus rhythm with severe chronic congestive heart failure. We also assessed the response to acute (n = 12) and chronic (n = 8) converting-enzyme inhibition with captopril. The control tilt was characterized by high cardiac filling pressures, absence of significant peripheral pooling and apparent absence of afferent stimuli for hemodynamic and hormonal response. After acute captopril, the hemodynamic response to tilt was improved, but not normalized. The chronic response was characterized by the absence of a reflex increase of systemic vascular resistance on tilt despite peripheral pooling. Five patients developed orthostatic hypotension, but responded to acute infusion of 0.9% sodium chloride. Efferent sympathetic activity (response to cold pressor) was abnormal during the control study, but indistinguishable from normal subjects by the time of chronic captopril therapy. This paralleled an improved responsiveness of plasma catecholamines during chronic tilt. The Valsalva maneuver remained abnormal. There was a distinct absence of the normally anticipated heart rate increase on tilt, suggesting a parasympathetic abnormality.