Improved exercise performance and skeletal muscle strength after simulated altitude exposure: A novel approach for patients with chronic heart failure

Background: Adaptation to altitude leads to beneficial physiologic changes that improve oxygen delivery and utilization by the periphery. Athletes have used simulated altitude enclosures as part of their training regimen to improve exercise performance. We hypothesized that changes due to acclimatization would also be beneficial for patients with heart failure (HF). We report the results of a pilot study of altitude exposure in patients with chronic HF. Methods and Results: Subjects with chronic stable HF, left ventricular ejection fraction (LVEF) ≤35%, on optimal medical therapy were enrolled and underwent simulated altitude exposure for 10 sessions, each 3-4 hours, over a period of 22 days. Starting altitude was 1,500 m and was increased by 300 m with each subsequent session to a maximum altitude of 2,700 m. Peak oxygen consumption, 6-minute walk distance (6MW), skeletal muscle strength, quality of life scores, LVEF, and hematologic parameters were measured at baseline and 48 hours and 4 weeks after the final session. Twelve subjects (median age 52.5 y, ejection fraction 31.7%) successfully completed the protocol without any adverse effects. Peak oxygen consumption significantly improved after altitude sessions from 13.5 ± 1.8 to 14.2 ± 1.9 mL kg ^-1 min ^-1 (P =.036) and remained elevated after 4 weeks. There were significant improvements in exercise time, 6MW, skeletal muscle strength, and quality of life scores and a trend toward improvement in LVEF after completion of altitude sessions, which were sustained after 1 month. Conclusions: Simulated altitude exposure up to 2,700 m is safe and well tolerated in patients with chronic stable HF and may have beneficial effects on exercise performance, muscular strength, and quality of life.