Sympathetic autoregulation in peripheral vascular disease

Abstract

Background: Lower limb venous pressure increases on dependency, stimulating a local sympathetic axon refex which triggers precapillary and arteriolar vasoconstriction. The resulting decrease in arterial calf inflow, known as the venoarteriolar response (VAR), is impaired in critical leg ischaemia. The aim of the study was to evaluate the VAR in symptomatic non-critical leg ischaemia and after restoration of leg perfusion following successful revascularization. Methods: The study included 30 normal subjects, 30 patients with stable intermittent claudication and 30 patients with severe ischaemia who had undergone successful infrainguinal revascularization. In all patients the foot skin blood flow (flux) in the horizontal (HBF) and sitting (SBF) positions was measured using laser Doppler fluxmetry. The VAR was calculated as (HBF-SBF)/HBF × 100 per cent. The pressure that elicited the reflex (pVAR) was evaluated in the horizontal position. Results: The median VAR was significantly lower in patients with stable claudication than in normal subjects or patients following successful revaseularlzation (29.1 versus 59.5 and 63.9 per cent respectively; P<0.0001). Similar results were obtained for the pVAR (22 versus 45 and 40 mmHg respectively; P<0.001). There was no difference, however, in either the VAR or pVAR between normal individuals and patients following a successful bypass. Conclusion: Patients with claudication had a significant impairment of orthostatic sympathetic autoregulation. After successful revascularization, and in spite of the extensive disease in the receiving circulation, this autoregulation returned to normal.