The effects of exercise training on sympathetic neural activation in advanced heart failure: a randomized controlled trial.

Objectives: The goal of this study was to test the hypothesis that exercise training reduces resting sympathetic neural activation in patients with chronic advanced heart failure.

Background: Exercise training in heart failure has been shown to be beneficial, but its mechanisms of benefit remain unknown.

Methods: Sixteen New York Heart Association class II to III heart failure patients, age 35 to 60 years, ejection fraction < or =40% were divided into two groups: 1) exercise-trained (n = 7), and 2) sedentary control (n = 9). A normal control exercise-trained group was also studied (n = 8). The four-month supervised exercise training program consisted of three 60 min exercise sessions per week, at heart rate levels that corresponded up to 10% below the respiratory compensation point. Muscle sympathetic nerve activity (MSNA) was recorded directly from peroneal nerve using the technique of microneurography. Forearm blood flow was measured by venous plethysmography.

Results: Baseline MSNA was greater in heart failure patients compared with normal controls; MSNA was uniformly decreased after exercise training in heart failure patients (60 +/- 3 vs. 38 +/- 3 bursts/100 heart beats), and the mean difference in the change was significantly (p < 0.05) greater than the mean difference in the change in sedentary heart failure or trained normal controls. In fact, resting MSNA in trained heart failure patients was no longer significantly greater than in trained normal controls. In heart failure patients, peak VO(2) and forearm blood flow, but not left ventricular ejection fraction, increased after training.

Conclusions: These findings demonstrate that exercise training in heart failure patients results in dramatic reductions in directly recorded resting sympathetic nerve activity. In fact, MSNA was no longer greater than in trained, healthy controls.