Table 2.

Comparison of venous thromboembolism characteristics between high-altitude and low-altitude regions.

	Deep vein thrombosis at high altitude	Deep vein thrombosis at low altitude
Epidemiology	Studies have shown that among individuals residing continuously at high altitude (> 15,000 feet) for 3-4 months, the incidence of deep vein thrombosis (with or without pulmonary embolism) reaches 2469 per 100,000 person-years [7]	The incidence of deep vein thrombosis ranges from 53 to 162 cases per 100,000 population [31, 32]
Risk factors	High altitude promotes thrombosis via hypoxia, dehydration, stasis, and inherited or acquired prothrombotic factors	Major surgery, severe trauma, prolonged bed rest, limb immobilization, malignancy
Clinical presentation	Limb pain, swelling, and localized redness, warmth, and tenderness may occur, with symptoms potentially overlapping with high-altitude–related joint discomfort	Sudden limb swelling and pain, pitting edema and warmth, calf or thigh tenderness, positive Homans' sign, superficial vein dilation, phlegmasia cerulea dolens, absent peripheral pulse
Lab findings	Elevated hemoglobin and hematocrit due to chronic hypoxia, increased blood viscosity, elevated D-dimer (may reflect both thrombosis and hypoxic baseline), decreased arterial oxygen partial pressure (PaO2), normal or mildly elevated platelets and fibrinogen	D-dimer elevated in acute thrombotic events, hemoglobin and hematocrit usually normal, blood viscosity normal, PaO2 typically normal, platelets, and fibrinogen may be elevated in inflammatory or malignant conditions
Treatment	Anticoagulation is primary; descent to lower altitude recommended. Thrombolysis used cautiously due to bleeding risk	Standard anticoagulation; thrombolysis/intervention as indicated. Altitude not a treatment concern
Prognosis	Higher risk of recurrence, PE, and complications if hypoxia persists	Generally good with treatment; complications such as post-thrombotic syndrome or PE in severe cases