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.