Effect of 6 wk of high-intensity one-legged cycling on functional sympatholysis and ATP signaling in patients with heart failure.

Breathlessness during daily activities is the primary symptom in patients with heart failure (HF). Poor correlation between the hemodynamic parameters of left ventricular performance and perceived symptoms suggests that other factors, such as skeletal muscle function, play a role in determining exercise capacity. We investigated the effect of 6 wk of high-intensity, one-legged cycling (HIC; 8 x 4 at 90% one-legged cycling max) on 1) the ability to override sympathetic vasoconstriction (arterial infusion of tyramine) during onelegged knee-extensor exercise (KEE), 2) vascular function (arterial infusion of ACh, sodium nitroprusside, tyramine, and ATP), and 3) exercise capacity in HF patients with reduced ejection fraction (n = 8) compared with healthy individuals (n = 6). Arterial tyramine infusion lowered leg blood flow and leg vascular conductance at rest and during KEE before the training intervention in both groups (P < 0.05) but not during KEE after the training intervention. There was no but not during KEE after the training intervention. There was no difference between groups. The peak vasodilatory response to ATP was blunted in HF patients (P < 0.05), whereas there was no difference in ACh- and sodium nitroprusside-induced vasodilation between HF patients and healthy individuals. ACh-induced vasodilation increased in HF patients after the training intervention (P < 0.05). HIC improved aerobic capacity in both groups (P < 0.05), whereas only HF patients made improvements in the 6-min walking distance (P < 0.05). These results suggest that exercise hyperemia and functional sympatholysis are not altered in HF patients and that functional sympatholysis is improved with HIC in both HF patients and healthy individuals. Moreover, these results suggest that the peak vasodilatory response to ATP is blunted in HF. [ABSTRACT FROM AUTHOR]