Baroreflex regulation of regional blood flow in congestive heart failure

In patients with congestive heart failure (CHF), the distibution of the cardiac output is altered. Cardiopulmonary and arterial baroreceptors normally can regulate regional blood flow, but their contribution in heart failure is not known. To examine the role of baroreceptors in the regulation of regional blood flow in CHF, the effect of lower body negative pressure (LBNP) on forearm, renal, and splanchnic blood flow was evaluated in 12 patients with heart failure. Incremental LBNP at -10 and -40 mmHg decreased central venous pressure but had no effect on systolic blood pressure or pulse pressure. Renal blood flow decreased from 505 ± 63 to 468 ± 66 ml/min during LBNP -10 mmHg (P<0.05) and to376 ± 74 ml/min during LBNP -40 mmHg (P<0.01). Splanchnic blood flow decreased from 564 ± 76 to 480 ± 62 ml/min during LBNP -10 mmHg (P<0.01) and to 303 ± 45 ml/min during LBNP -40 mmHg (P<0.01). Forearm blood flow did not decrease during LBNP -10 mmHg or -40 mmHg. To determine whether the absence of limb vasoconstriction during LBNP was confined to abnormalities in the baroreflex arc or was secondary to impaired end-organ responsiveness, six patients with heart failure and six normal subjects received an intrabrachial artery infusion of phenylephrine. Phenylephrine increased forearm vascular resistance comparably in each group. These data demonstrate that baroreceptors can regulate splanchnic and renal but not limb vascular resistance in patients with congestive heart failure and may contribute to the redistribution of blood flow that occurs in this disorder.