Peak Skeletal Muscle Perfusion is Maintained in Patients with Chronic Heart Failure when Only a Small Muscle Mass is Exercised

Objectives: The issue to be resolved was whether peripheral leg blood flow in patients with chronic heart failure (CHF) is reduced by low local flow capacity or as a function of the amount of muscle mass activated during exercise.

Methods And Results: In ten CHF patients (ejection fraction 26 (9)%), and 12 healthy controls central and peripheral circulatory responses were assessed during dynamic one- and two-legged knee extensor work. The patients reached a peak perfusion of 234 (16) ml 100 g-1 min-1 in the one-legged mode, which was similar to the controls (244 (11) ml 100 g-1 min-1). At peak two-legged work muscle perfusion was reduced in the patients by 24% (P < 0.05). In contrast the controls maintained their peak muscle perfusion. The mass of the quadriceps femoris muscle and peak leg blood flow correlated closely for both groups at peak one-legged work (r = 0.85, P < 0.001). Peak oxygen uptake in the active limb during one-legged exercise was similar for patients and controls (0.52 (0.06) vs. 0.63 (0.06) l min-1), but it was 38% lower (P < 0.05) in patients than controls during exhaustive two-legged exercise. Arterial systemic oxygen delivery (cardiac output x arterial oxygen content), at peak exercise was highly correlated with peak one- and two-legged workload for both groups, explaining 70% of the difference in peak workload attained (P < 0.001). At peak two-legged exercise non-exercising tissues of the body in the male CHF patients with the largest limb muscle mass, received a blood flow of only 1.2 (0.7) 1 min-1. Mean arterial blood pressure at peak work in both test conditions was significantly lower for the patients than the controls. A higher sympathetic nerve activity in the patients, as evaluated by arterial noradrenaline concentration (NA) and leg NA spillover, contributed to maintain the perfusion pressure.

Conclusions: Patients with moderate CHF can reach a peak skeletal muscle perfusion and a leg oxygen uptake comparable to that of healthy individuals when a sufficiently small muscle mass is activated. Exercise involving a larger muscle mass, for the patients in this study about 4 kg, markedly reduces peak leg blood flow, perfusion and oxygen uptake as well as blood flow to non-exercising organs and tissues.