Abstract
There are several genetic and acquired risk factors for venous thromboembolism. Exposure
to high altitude (HA), either during air travel, ascension of mountains, or while
engaging in sports activities, has been observed to result in a hypercoagulable state,
thus predisposing to thromboembolic events. Although several previous studies have
suggested that conditions present at HAs contribute to establish a prothrombotic milieu,
published reports are contradictory and the exact underlying mechanism remains poorly
understood. Results from HA studies also show that environmental conditions at HA
such as hypoxia, dehydration, hemoconcentration, low temperature, use of constrictive
clothing as well as enforced stasis due to severe weather, would support the occurrence
of thrombotic disorders. The three leading factors of Virchow triad, that is, venous
stasis, hypercoagulability, and vessel-wall injury, all appear to be present at HA.
In synthesis, the large list of environmental variables suggests that a single cause
of HA-induced thromboembolic disorders (TED) may not exist, so that this peculiar
phenomenon should be seen as a complex or multifactorial trait. Further investigation
is needed to understand the risk of TED at HA as well as the possible underlying mechanisms.
Keywords
venous thrombosis - pulmonary embolism - high altitude - air travel - thrombosis -
hypercoagulation
