ARTERIAL BAROREFLEX REGULATION OF BLOOD-PRESSURE IN PATIENTS WITH CONGESTIVE-HEART-FAILURE

Objectives. This study was designed to determine whether arterial baroreflex control of blood pressure is altered in patients with congestive heart failure. Background. Arterial baroreceptor reflexes normally contribute to cardiovascular homeostasis by preserving blood pressure during changes in volume and posture. Methods. Arterial baroreceptor reflex function was studied in 18 patients with congestive heart failure and 18 age matched healthy subjects. The arterial baroreceptor-blood pressure reflex was assessed by measuring the blood pressure response to perturbations in carotid sinus pressure. Carotid baroreceptors were stimulated by applying negative pressure to a custom neck chamber (-10, -20 and -30 mm Hg) and were unloaded by applying neck positive pressure (+10, +20 and +30 mm Hg). Results. Peak carotid baroreceptor-blood pressure reflex sensitivity was lower in patients with heart failure than in normal subjects (0.19 +/- 0.02 vs. 0.30 +/- 0.03 mm Hg/mm Hg, p < 0.05). During neck positive pressure, blood pressure increased less in the heart failure group than in the normal group. During neck suction, however, the decrease in blood pressure was similar in the two groups. Conclusions. Patients with heart failure are less able than normal subjects to increase blood pressure during arterial baroreceptor unloading, but they can reduce blood pressure appropriately during baroreceptor stimulation. These observations suggest that the resting blood pressure position on the arterial baroreceptor stimulus response curve, the operational point, is closer to the baroreceptor threshold in patients with heart failure than in normal subjects. As a result, reduced inhibitory signals from arterial baroreceptors most likely contribute to a heightened state of sympathetic activity and vasoconstriction in patients with congestive heart failure.