Clinical assessment
Four clinical measures were assessed at the baseline evaluation and at the end of each crossover period. A maximum exercise test on a bicycle was performed to measure peak Vo2 and Vo2 at the anaerobic threshold, using the V-slope method (23). Submaximal exercise was measured by the distance walked in 6 min, according to the method of Bittner (24). Quality of life was assessed by the Minnesota Living With Heart Failure Questionnaire score, which ranges from 0 (best) to 105 (worst) (25). Patient functional status was assessed by the NYHA functional classification.
End points
The primary end point was an improvement in exercise capacity, as assessed first by peak Vo2, second by Vo2 at the anaerobic threshold during maximum exercise testing, and third by the distance walked in 6 min. The secondary end points were quality-of-life score and NYHA functional classification.