High-altitude pulmonary hypertension: a pathophysiological entity to different diseases.

Pulmonary hypertension is a hallmark of high-altitude pulmonary oedema (HAPE) and of congestive right heart failure in subacute mountain sickness (SMS) and chronic mountain sickness (CMS) in the Himalayas and in the end-stage of CMS (Monge's disease) in the Andes. There are studies to suggest that transmission of excessively elevated pulmonary artery pressure and/or flow to the pulmonary capillaries leading to alveolar haemorrhage is the pathophysiological mechanism of HAPE. In the Himalayas, HAPE was successfully prevented by extending the acclimatisation period from a few days to 5 weeks, however, this did not prevent the occurrence of congestive right heart failure after several weeks of stay at 6,000 m. This leads to the concept that rapid remodelling of the small precapillary arteries prevents HAPE but not the development of right heart failure in SMS and CMS. Unresponsiveness of pulmonary hypertension to oxygen at high altitude and its complete resolution only after weeks of stay at low altitude suggest that structural rather than functional changes are its pathophysiological mechanism. Since pulmonary hypertension at high altitude is the driving force leading to high-altitude pulmonary oedema and "high-altitude right heart failure" in newcomers and residents of high altitude, the authors propose to adjust current terminology accordingly.