Sympathetic nerve activity restrains reflex vasodilatation in heart failure

Blunted reflex muscle vasodilatory response during exercise in heart failure (HF) patients may be secondary to augmented vasoconstriction. We tested the hypothesis that the exaggerated sympathetic nerve activity restrains the reflex muscle vasodilatation during exercise in HF patients.

We studied the reflex vasodilatory response (plethysmography) during 3 min static handgrip exercise at 30% maximal voluntary contraction in 10 advanced HF patients (45 +/- 3 year, NYHA Functional Class III/IV) and 10 age-matched normal controls (NC, 40 +/- 3 year, P = 0.23) during intra-arterial infusion of: (1) saline control; and (2) alpha-adrenergic blocker (phentolamine).

Baseline forearm vascular conductance (FVC) was lower in HF patients than in NC (2.07 +/- 0.2 vs. 4.26 +/- 0.6 units, respectively; P = 0.002). FVC responses during exercise increased significantly in NC, but not in HF patients (delta changes: 1.05 +/- 0.4 vs. 0.05 +/- 0.2 units, respectively). Phentolamine significantly increased resting FVC in HF patients (from 2.07 +/- 0.2 to 5.74 +/- 0.7 units, P = 0.00004) and restored reflex vasodilatory responses during exercise (delta changes: from 0.05 +/- 0.2 to 1.82 +/- 0.9 units) eliminating the difference in FVC between both groups.

The blunted reflex muscle vasodilatory response during exercise in advanced HF patients is, at least in part, due to the increase in sympathetic nerve activity.