ENALAPRILAT AUGMENTS ARTERIAL AND CARDIOPULMONARY BAROREFLEX CONTROL OF SYMPATHETIC-NERVE ACTIVITY IN PATIENTS WITH HEART-FAILURE

Objectives, This study sought to determine the effects of enalaprilat on reflex control of sympathetic nerve activity. Background, Angiotens in-converting enzyme inhibitors decrease mortality in patients with co ngestive heart failure, Their efficacy appears to be related important ly to antiadrenergic effects, the mechanism for which has not been det ermined, Because baroreflexes tonically inhibit sympathetic outflow, a nd baroreflexes are blunted in heart failure, we hypothesized that the se agents reduce sympathetic activity by augmenting baroreflexes. Meth ods, We assessed baroreflex control of sympathetic nerve activity and heart rate in patients with congestive heart failure and in control su bjects before and after enalaprilat (0.02 mg/kg body weight intravenou sly). Arterial baroreflexes were perturbed by bolus administration of sodium nitroprusside and phenylephrine, Cardiopulmonary baroreflexes w ere perturbed by lower body negative pressure and head-down tilt, Musc le sympathetic nerve activity was recorded by microneurography. Result s, Enalaprilat decreased systolic blood pressure in patients with hear t failure and control subjects, Sympathetic nerve activity increased i n control subjects but decreased in patients with heart failure after enalaprilat despite reductions in central venous pressure in this grou p, Baroreflex control of sympathetic nerve activity was unchanged by e nalaprilat in control subjects, In patients with heart failure, both a rterial and cardiopulmonary baroreflex control of sympathetic nerve ac tivity was enhanced by enalaprilat. Baroreflex control of heart rate w as unchanged by enalaprilat in either group. Conclusions, Enalaprilat augments both arterial and cardio pulmonary baroreflex control of symp athetic activity in heart failure, These augmented inhibitory influenc es are associated with a reduction in sympathetic outflow and may cont ribute to the beneficial effects of angiotensin converting enzyme inhi bitors in heart failure.