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.
Diagnosis of VTE7
Recommendation 1
Validated clinical prediction rules should be used to estimate pretest probability of VTE, both DVT and PE, and as the basis of interpretation of subsequent tests.Recommendation 2
In appropriately selected patients with low pretest probability of DVT or PE, obtaining a high-sensitivity D-dimer assay is a reasonable option. If negative, it indicates a low likelihood of VTE.Recommendation 3
Ultrasound is recommended for patients with intermediate-to-high pretest probability of DVT in the lower extremities.Recommendation 4
Patients with intermediate or high pretest probability of PE require diagnostic imaging studies.Management of VTE8
Recommendation 1
Low-molecular-weight heparin (LMWH) rather than unfractionated heparin should be used whenever possible for the initial inpatient treatment of DVT. Either unfractionated heparin or LMWH is appropriate for the initial treatment of PE.Recommendation 2
Outpatient treatment of DVT, and possibly PE, with LMWH is safe and cost-effective for carefully selected patients. It should be considered if the required support services are in place.Recommendation 3
Compression stockings should be used routinely to prevent post-thrombotic syndrome, beginning within 1 month of diagnosis of proximal DVT and continuing for a minimum of 1 year after diagnosis.Recommendation 4
There is insufficient evidence to make specific recommendations for types of anticoagulation management of VTE in pregnant women.Recommendation 5
Anticoagulation should be maintained for 3 to 6 months for VTE secondary to transient risk factors and for more than 12 months for recurrent VTE. Although the appropriate duration of anticoagulation for idiopathic or recurrent VTE is not known definitely, evidence exists of substantial benefit from extended-duration therapy.Recommendation 6
LMWH is safe and efficacious for the long-term treatment of VTE in selected patients (and may be preferable for patients with cancer).References
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.