Effects of a new angiotensin-converting enzyme inhibitor, alacepril, on changes in neurohormonal factors and arterial baroreflex sensitivity in patients with congestive heart failure

Abstract

Objective: Patients with heart failure have abnormal neurohormonal regulation during orthostatic stress, and abnormal arterial baroreflex function. This study investigated the effects of alacepril, a new angiotensin-converting enzyme inhibitor with sulfhydryls, on changes in neurohormonal factors during tilt and on the arterial baroreflex control of heart rate.

Methods: Plasma concentrations of noradrenaline, adrenaline, renin activity, angiotensin II, and atrial natriuretic peptide were measured at supine rest and after 30 degrees head-up tilt with measurements of central venous pressure and cardiac dimensions in seven patients with congestive heart failure (65 years, ejection fraction = 34%). Arterial baroreflex control of heart rate was assessed by phenylephrine bolus. The arterial baroreflex test was re-examined 3 h after oral alacepril (37.5 mg). The tilt and arterial baroreflex tests were repeated 12 weeks after alacepril treatment (50 mg x day(-1)).

Results: Heart rate, blood pressure, and neurohormonal factors did not differ before and after chronic alacepril, except for a trend toward an increase in renin activity (2.0 vs 4.9 ng x ml(-1) x h(-1)). Head-up tilt decreased central venous pressure (-2.5 mmHg) with a decrease in cardiac dimensions in the pre-alacepril phase. These changes were accompanied by increases in noradrenaline, adrenaline, and angiotensin II and a decrease in atrial natriuretic peptide. After chronic alacepril, the increase in noradrenaline during head-up tilt tended to be smaller (84 vs 30 pg x ml(-1)), with similar changes in central venous pressure (-3.4 mmHg) and cardiac dimensions. Both acute (3.6 vs 4.8 ms mmHg(-1)) and chronic (3.6 vs 6.7 ms mmHg(-1)) alacepril treatment was associated with a trend towards an increase in the arterial baroreflex control of heart rate.

Conclusion: These results suggest that treatment with alacepril may cause a reduction of sympathetic activation during orthostatic stress and may enhance arterial baroreflex function in patients with mild to moderate heart failure.