Physical capacity increase in patients with heart failure is associated with improvement in muscle sympathetic nerve activity

Background: Exercise training improves physical capacity in patients with heart failure with reduced ejection fraction (HFrEF), but the mechanisms involved in this response is not fully understood. The aim of this study was to determine if physical capacity increase in patients HFrEF is associated with muscle sympathetic nerve activity (MSNA) reduction and muscle blood flow (MBF) increase. Methods: The study included 124 patients from a 17-year database, divided according to exercise training status: 1) exercise-trained (ET, n = 83) and 2) untrained (UNT, n = 41). MSNA and MBF were obtained using microneurography and venous occlusion plethysmography, respectively. Physical capacity was evaluated by cardiopulmonary exercise test. Moderate aerobic exercise was performed 3 times/wk. for 4 months. Results: Exercise training increased peak oxygen consumption (VO2, 16.1 +/- 0.4 vs 18.9 +/- 0.5 mL.kg(-1).min(-1), P < 0.001), LVEF (28 +/- 1 vs 30 +/- 1%, P = 0.027), MBF (1.57 +/- 0.06 vs 2.05 +/- 0.09 mL.min(-1).100 ml(-1), P < 0.001) and muscle vascular conductance (MVC, 1.82 +/- 0.07 vs 2.45 +/- 0.11 units, P < 0.001). Exercise training significantly decreased MSNA (45 +/- 1 vs 32 +/- 1 bursts/min, P < 0.001). The logistic regression analyses showed that MSNA [(OR) 0.921, 95% CI 0.883-0.962, P < 0.001] was independently associated with peak VO2. Conclusions: The increase in physical capacity provoked by aerobic exercise in patients with HFrEF is associated with the improvement in MSNA.