High altitude induced deep venous thrombosis : A study of 28 cases

Background: It is well recognized that a hypercoagulable state exists when a person is exposed to high altitude environment. This may manifest as early thromboembolic episodes, which result in acute pulmonary embolism. On further exposure to high-altitude environment, the ongoing thrombogenesis has been implicated in the causation of subacute mountain sickness. Only anecdotal reports of deep vein thrombosis (DVT) of leg veins at high altitude exist in literature and only two studies of this disease entity have been reported in literature. Aim: To report the high incidence of deep venous thrombosis of leg veins at high altitude, as compared to lowlands and define the disease entity High Altitude Induced Deep Venous Thrombosis (HADVT). Setting and Design: Twenty-eight cases of deep venous thrombosis of leg veins occurring in Indian soldiers presenting to a high altitude hospital at 11,800 feet, staying in HA for a prolonged period of time (>5 months), were studied. The incidence of patients presenting to this hospital was compared with the incidence of deep venous thrombosis in a hospital situated in the lowland. Results: The annual incidence of deep vein thrombosis in lowlanders exposed to high altitude was much higher (0.7/1000) than in soldiers staying in lowland (0.028/1000). The relative risk of deep vein thrombosis was much higher among soldiers at high altitude as compared to soldiers in the plains. Long-term stay of lowlanders at high altitude was associated with a 24.5 (95% Confidence limits 8.59 to 69.84) times risk of deep venous thrombosis of the calf veins as compared to those staying in low altitude. Conclusion: In view of the greatly increased risk of getting deep venous thrombosis in leg veins at high altitude, we wish to define this definite disease entity as High Altitude Induced Deep Venous Thrombosis (HADVT).