High-altitude pulmonary hypertension

Abstract

High-altitude pulmonary hypertension (HAPH) is a specific disease affecting populations that live at high elevations. The prevalence of HAPH among those residing at high altitudes needs to be further defined. Whereas reduction in nitric oxide production may be one mechanism for the development of HAPH, the roles of endothelin-1 and prostaglandin I 2 pathways in the pathogenesis of HAPH deserve further study.Although some studies have suggested that genetic factors contribute to the pathogenesis of HAPH, data published to date are insufficient for the identification of a significant number of gene polymorphims in HAPH.The clinical presentation of HAPH is nonspecific. Exertional dyspnoea is the most common symptom and signs related to right heart failure are common in late stages of HAPH. Echocardiography is the most useful screening tool and right heart catheterisation is the gold standard for the diagnosis of HAPH. The ideal management for HAPH is migration to lower altitudes. Phosphodiesterase 5 is an attractive drug target for the treatment of HAPH.In addition, acetazolamide is a promising therapeutic agent for high-altitude pulmonary hypertension. To date, no evidence has confirmed whether endothelin-receptor antagonists have efficacy in the treatment of high-altitude pulmonary hypertension.KEYWORDS: High-altitude pulmonary hypertension, hypoxia-inducible factor-1, nitric oxide, phosphodiesterase inhibitors, pulmonary vasoconstriction, right heart catheterisation H igh-altitude pulmonary hypertension (HAPH) due to chronic exposure to high altitude is a designated subset of pulmonary hypertension (PH) according to the third clinical classification of PH, which was approved during a conference in 2003 in Venice, Italy [1].It is estimated that more than 140 million people live 2,500 m above sea level, and the number of temporary visitors to mountains is close to 40 million [2,3]. Due to the substantial population exposed to the effects of high altitude, HAPH has become a public health problem in mountainous regions throughout the world. There are three specific locations where high-altitude studies have recently been performed: 1) the Himalayas of Asia; 2) the Andes of South America; and 3) the Rocky Mountains of North America. The present review will focus on the epidemiology, pathophysiology, pathogenesis, clinical characteristics and treatment of HAPH. DEFINITIONHAPH is a clinical syndrome seen in adults and children residing in high-altitude regions. As chronic mountain syndrome (CMS) is characterised by severe hypoxaemia, excessive polycythaemia and marked PH [4], HAPH is regarded as an important subset of CMS. However, the definition and diagnostic criteria of HAPH remain somewhat vague. According to the 2003 conference on PH, HAPH is classified in the third group of PH (table 1) [1]. Thus, right heart catheterisation is required to establish the diagnosis of HAPH (PH is defined by a mean pulmonary artery pressure (P pa) of .25 mmHg at rest or .30 mmHg with exercise) [5]. EPIDEMIOLOGYAlthough HAP...

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“…In addition, other chapters will emphasise some important aspects of pulmonary vascular medicine, including pulmonary hypertension complicating hereditary haemorrhagic telangiectasia [22,23], pulmonary hypertension in high-altitude residents [24], pulmonary hypertension in children [25], chronic thromboembolic pulmonary hypertension [26], and novel therapeutic strategies such as inhaled prostaglandins [27] and soluble guanylate cyclase stimulation, an emerging option in pulmonary hypertension therapy [28]. …”