Considerations on safety and treatment of patients with chronic heart failure at high altitude.

Prognosis and quality of life of chronic heart failure (HF) patients have greatly improved over the last decade. Consequently, many patients are willing to spend leisure time at altitude, usually <3500 m, but their safety in doing so is undefined. HF is a syndrome that often has relevant co-morbidities, such as pulmonary hypertension, COPD, unstable cardiac ischemia, and anemia. HF co-morbidities may per se impede a safe stay at altitude. Exercise at simulated altitude is associated with a reduction in performance, which is greater in HF patients than in normal subjects and greater in patients with most severe HF. In normal subjects, the reduction in performance is ∼2% every 1000 m altitude increase, whereas it is 4% and 10% in HF patients with normal or slightly diminished exercise capacity and in HF patients with markedly diminished exercise capacity. On-field experience with HF patients at altitude is limited to subjects driven to altitude (3454 m) for a few hours. The data showed a reduction in exercise capacity similar to that reported at simulated altitude. "Optimal" HF treatment in patients spending time at altitude is likely different from optimal treatment at sea level, particularly as regards β-blockers. Carvedilol, a β1-β2-α-blocker, reduces the hypoxic ventilatory response through a reduction of the chemoreflex response, and it reduces alveolar-capillary gas diffusion, which is under control by β2-receptors. These actions are not shared by selective β1-blockers such as bisoprolol and nebivolol, which should be preferred for treatment of HF patients willing to spend time at altitude. In conclusion, spending time at altitude (<3500 m) is safe for HF patients, provided that subjects are free of co-morbidities that may directly interfere with the adaptation to altitude. However, HF patients experience a reduction of exercise capacity in proportion to HF severity and altitude. Finally, HF patients should undergo a specific "altitude-tailored treatment" to avoid pharmacological interference with altitude adaptation mechanisms.