PEAK SKELETAL-MUSCLE PERFUSION IS MAINTAINED IN PATIENTS WITH CHRONICHEART-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 lo cal flow capacity or as a function of the amount of muscle mass activa ted during exercise, Methods and results: In ten CHF patients (ejectio n fraction 26 (9)%), and 12 healthy controls central and peripheral ci rculatory responses were assessed during dynamic one- and two-legged k nee extensor work. The patients reached a peak perfusion of 234 (16) m l 100 g(-1) min(-1) in the one-legged mode, which was similar to the c ontrols (244 (11) ml 100 g(-1) min(-1)). At peak two-legged work muscl e 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 f or both groups at peak one-legged work (r = 0.85, P < 0.001). Peak oxy gen uptake in the active limb during one-legged exercise was similar f or patients and controls (0.52 (0.06) vs. 0.63 (0.06) 1 min(-1)), but it was 38% lower (P < 0.05) in patients than controls during exhaustiv e two-legged exercise. Arterial systemic oxygen delivery (cardiac outp ut x arterial oxygen content), at peak exercise was highly correlated with peak oneand two-legged workload for both groups, explaining 70% o f the difference in peak workload attained (P < 0.001). At peak two-le gged exercise non-exercising tissues of the body in the male CHF patie nts 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 cont rols, A higher sympathetic nerve activity in the patients, as evaluate d by arterial noradrenaline concentration (NA) and leg NA spillover, c ontributed to maintain the perfusion pressure, Conclusions: Patients w ith moderate CHF can reach a peak skeletal muscle perfusion and a leg oxygen uptake comparable to that of healthy individuals when a suffici ently small muscle mass is activated. Exercise involving a larger musc le mass, for the patients in this study about 4 kg, markedly reduces p eak leg blood flow, perfusion and oxygen uptake as well as blood flow to non-exercising organs and tissues.