Sympathetic autoregulation in peripheral vascular disease

Background: Lower limb venous pressure increases on dependency, stimulating a local sympathetic axon reflex 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 le g ischaemia and after restoration of leg perfusion following successful rev ascularization. Methods: The study included 30 normal subjects, 30 patients with stable int ermittent claudication and 30 patients with severe ischaemia who had underg one successful infrainguinal revascularization. In all patients the foot sk in blood flow (flux) in the horizontal (HBE) and sitting (SBF) positions wa s measured using laser Doppler fluxmetry, The VAR was calculated as (HBF-SB F)/HBF x 100 per cent. The pressure that elicited the reflex (pVAR) was eva luated in the horizontal position. Results: The median VAR was significantly lower in patients with stable cla udication than in normal subjects or patients following successful revascul arization (29.1 versus 59.5 and 63.9 per cent respectively; P<0.0001). Simi lar results were obtained for the pVAR (22 versus 45 and 40 mmHg respective ly; P<0.001). There was no difference, however, in either the VAR or pVAR b etween normal individuals and patients following a successful bypass. conclusion: Patients with claudication had a significant impairment of orth ostatic sympathetic autoregulation, After successful revascularization, and in spite of the extensive disease in the receiving circulation, this autor egulation returned to normal.