The immediate rise in leg blood flow during calf exercise is dependent on functional venous valves

Abstract

The importance of the muscle pump in exercise hyperemia is incompletely understood. We have recently shown that a large hydrostatic column induced by head up tilt (HUT) increases the effect of the leg muscle pump on muscle perfusion in healthy subjects. In this study we investigated the effect of a larger hydrostatic column on muscle perfusion in patients with insufficient venous valves.The transient and steady state rise in leg arterial blood flow (ultrasound Doppler) was investigated in 10 patients with venous insufficiency, both supine and 30º HUT.Within ~15 s of the start of exercise, the rise in femoral flow was not significantly different between supine (0.21 L/min) and HUT (0.24 L/min). After 80 s of exercise, femoral flow was stable at 0.20 L/min and 0.22 L/min above rest in supine and HUT respectively (not significantly different).These results indicate that there is no significant muscle pump effect on the immediate rise in muscle perfusion in patients with venous insufficiency.This is in contrast to the findings in healthy subjects, where the transient rise in femoral flow was considerably larger in the tilted than in the supine position. The reduced immediate rise in blood flow observed in the present study indicates that the larger transient rise in femoral flow in healthy subjects was indeed dependent on functional venous valves, and thus caused by a leg muscle pump effect.Research support: University of Oslo.