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Deep Venous Thrombosis: Overview and Risk Factors

Deep venous thrombosis (DVT) leads to approximately 600,000 hospitalizations per year in the United States. Although it most often occurs in the lower extremities, DVT can also develop in the upper extremities, especially in patients with indwelling central venous catheters. DVT most commonly affects the iliac, popliteal, and femoral veins.

Pulmonary embolus (PE), due to embolization of a DVT, is one of the leading preventable causes of morbidity and mortality in hospitals. Symptoms of a PE include dyspnea, chest pain, and hemoptysis.

While DVT is often asymptomatic in the absence of PE, signs and symptoms may include swelling, tenderness, increased warmth and erythema in the affected area of the limb, and a palpable venous cord. Cyanosis of the limb may occur, which indicates deoxygenated hemoglobin trapped in nonfunctioning veins. Rarely, a patient may exhibit a positive Homan’s sign (pain along the calf with dorsiflexion of the foot). Mechanisms involved in DVT formation are collectively known as Virchow’s triad: venous stasis, hypercoagulability, and intimal injury (damage to the vessel wall).

Risk Factors

Prior DVT or PE. A history of previous episodes is the strongest indicator of risk.

Age. Risk increases with age, due in part to the greater likelihood of comorbid illness as one gets older.

Surgery. Major procedures (eg, orthopedic, thoracic, abdominal, and genitourinary) pose the greatest risk and therefore require prophylaxis.

Trauma.  Examples include fracture of the spine, pelvis, femur, or tibia.

Thrombophlebitis.

Coagulopathies. Deficiencies of proteins C and S as well as antithrombin III are well–documented risk factors. Presence of the lupus anticoagulant and activated protein C resistance (also known as factor V Leiden) also poses risk.

Neoplasm. Malignancy may induce a hypercoagulable state.

Prolonged immobilization. Venous stasis occurs in postoperative convalescence, nonambulatory patients, and extended air travel.

Obesity.

Elevated cholesterol. Elevated cholesterol increases risk of microemboli and possible thrombosis, especially when atherosclerosis is present.

Elevated fibrinogen levels.

Pregnancy. Fibrinolysis may be impaired during pregnancy and the postpartum period.

Oral contraceptives and hormone replacement therapy. These hormones may also disrupt fibrinolysis. Patients with the combined factors of age greater than 35 years, use of oral contraceptives, and smoking are at great risk for DVT.  

 

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Deep Venous Thrombosis: Diagnosis >>