Partition of Blood Flow to the Cutaneous and Muscular Beds of the Forearm at Rest and during Leg Exercise in Normal Subjects and in Patients with Heart Failure

The purpose of this study was to determine the relative effects of various levels of exercise on blood flow to skin and muscle of the resting extremity of normal subjects and the manner in which this distribution is modified by congestive heart failure. Blood flow to the skin and muscle of the forearm was determined plethysmographically with the aid of epinephrine iontophoresis at rest and during supine leg exercise in 12 normal subjects and in 9 patients with failure. In normal resting subjects, forearm blood flow averaged 6.30 ml/min/100 ml, 52% partitioned to muscle and 48% to skin. In the patients, forearm blood flow averaged 2.94 ml/min/100 ml, with 48% to muscle and 52% to skin. In normal subjects performing mild exercise, forearm muscle flow was not significantly changed, but during moderate and strenuous activity it was significantly reduced. Cutaneous blood flow, however, declined early at all levels of exertion. In the normal subjects, cutaneous hyperemia occurred late during moderate exercise but with strenuous exercise, was delayed until after exercise had been discontinued. In contrast, in the patients, forearm muscle blood flow decreased strikingly during leg exercise, cutaneous flow fell and remained depressed during the entire period of exercise, and no postexercise hyperemia occurred. Thus, in congestive heart failure, both the cutaneous and muscle beds of the forearm are abnormally constricted at rest, there is excessive vasoconstriction in both beds during leg exercise, and postexercise cutaneous vasodilation is abolished.