Although a thrombus may form in any part of the venous circulation, the majority of thrombi form in the lower extremities.1-3 The formation of such thrombi is known as venous thromboembolism (VTE). Once a thrombus is formed, it may lyse spontaneously, obstruct venous circulation, or embolize.1-3 When the venous circulation in lower extremities is obstructed by a thrombus, the condition is known as deep vein thrombosis (DVT). A thrombus that leaves the peripheral veins and lodges in the pulmonary artery or 1 of its branches is known as a pulmonary embolism (PE).1-3
Three primary components (Virchow?s triad) play a role in the development of a thrombus: venous stasis, vascular injury, and hypercoagulability.1-3 Venous stasis results from damage to venous valves, vessel obstruction, prolonged periods of immobility, or increased blood viscosity. Vascular injury may result from major orthopedic surgery, trauma, or indwelling venous catheters. Hypercoagulable states include malignancy, activated protein C resistance, or deficiency of protein C, protein S, or antithrombin.
A long-term complication of DVT is postthrombotic syndrome. This condition is caused by damage to venous valves by a thrombus. It may produce lower-extremity swelling, pain, tenderness, skin discoloration, and ulceration.
Symptoms of PE may include dyspnea, tachypnea, chest pain, tachycardia, palpitations, hemoptysis, cough, and diaphoresis. Severe cases will present with cardiovascular collapse characterized by cyanosis, shock, and oliguria. Symptoms of DVT may include unilateral leg swelling, pain, tenderness, erythema, and warmth. All these symptoms are considered to be nonspecific for PE and DVT.
Radiographic contrast studies are the most accurate and reliable method for the diagnosis of VTE. Ultrasonography may be preferred for the initial diagnosis of VTE because it is a noninvasive test. PE may be diagnosed by using either a ventilation- perfusion (V/Q) scan or spiral computed tomography. Chest x-rays also may assist in the diagnosis of PE. Chest x-rays may be normal or may show a wedge-shaped consolidation in the middle and lower lobes, which may be suggestive of a pulmonary infarction. Electrocardiograms may be abnormal in 85% of patients with acute PE. Some of the most frequent abnormalities may include sinus tachycardia, new-onset atrial fibrillation, and ST segment changes.
There are several risk factors for the development of VTE (Table 14).
A prediction rubric known as the Wells prediction rules can be used to predict the probability of DVT and PE. The result may help determine which diagnostic tests may be needed, based on clinical presentation (Tables 2 and 3).5,6
Recently, the American College of Physicians and the American Academy of Family Physicians published detailed recommendations for the diagnosis and management of VTE.7,8 The following are selected excerpts from the recommendations described in these guidelines.
1. Barreiro TJ. In: Domino, FJ, ed. The 5-Minute Clinical Consult. Philadelphia, Pa: Lippincott Williams & Wilkins; 2007.
2. Ferri FF. Ferri?s Clinical Advisor. 9th ed. Philadelphia, Pa: Mosby; 2007.
3. Haines ST, Zeolla M, Witt DM. In: Dipiro JT, ed. Pharmacotherapy. 6th ed. New York, NY: McGraw-Hill; 2005.
4. Geerts WH, Pineo GF, Heit JA, et al. Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest. 2004;126(3 suppl):338S-400S.
5. Wells PS, Anderson DR, Bormanis J, et al. Value of assessment of pretest probability of deep-vein thrombosis in clinical management. Lancet. 2002;350:1795-1798.
6. Chagnon I, Bounameaux H, Aujesky D, et al. Comparison of two clinical prediction rules and implicit assessment among patients with suspected pulmonary embolism. Am J Med. 2002;113:269-275.
7. Qaseem A, Snow V, Barry P, et al. Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Fam Med. 2007;5:57-62.
8. Snow V, Qaseem A, Barry P, et al. Management of venous thromboembolism: a clinical practice guideline from the American College of Physicians and the American Academy of Family Physicians. Ann Intern Med. 2007;146:204-210.