MUSCULAR BLOOD-FLOW RESPONSE TO SUBMAXIMAL LEG EXERCISE IN NORMAL SUBJECTS AND IN PATIENTS WITH HEART-FAILURE

Blood flow to working skeletal muscle is usually reduced during exerci se in patients with congestive heart failure. An intrinsic impairment of skeletal muscle vasodilatory capacity has been suspected as a mecha nism of this muscle underperfusion during maximal exercise, but its ro le during submaximal exercise remains unclear Therefore, we studied by transcutaneous Doppler ultrasonography the arterial blood flow in the common femoral artery at rest and during a submaximal bicycle exercis e in 12 normal subjects and in 30 patients with heart failure. Leg blo od flow was lower in patients than in control subjects at rest [0.29 /- 0.14 (SD) vs. 0.45 +/- 0.14 l/min, P < 0.01], at absolute powers an d at the same relative power (2.17 +/- 1.06 vs. 4.39 +/- 1.4 l/min, P < 0.001). Because mean arterial pressure was maintained, leg vascular resistance was higher in patients than in control subjects at rest (40 7 +/- 187 vs. 247 +/- 71 mmHg . l(-1). min, P < 0.01) and at the same relative power (73 +/- 49 vs. 31 +/- 13 mmHg . l(-1). min, P < 0.01) b ut not at absolute powers. Although the magnitude of increase in leg b lood flow corrected for power was similar in both groups (31 +/- 10 vs . 34 +/- 10 ml . min(-1). W-1), the magnitude of decrease of leg vascu lar resistance corrected for power was higher in patients than in cont rol subjects (5.9 +/- 3.3 vs. 1.9 +/- 0.94 mmHg . l(-1). min . W-1, P < 0.001). These results suggest that the ability of skeletal muscle va scular resistance to decrease is not impaired and that intrinsic vascu lar abnormalities do not limit vasodilator response to submaximal exer cise in patients with heart failure.