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It is not surprising that risk of acute DVT increases with the number of risk factors that a person has. First of all, risk of DVT increases 1.9 times for each 10-year increase in age (Table 1). Other risk factors are surgery, trauma, malignancy, previous DVT, immobilization, primary (genetic)hypercoagulable states, oral contraceptives and hormone therapy, and other variable factors.
Table 1. Risk Factors for Acute Deep Venous Thrombosis
Risk Factor |
Risk or Percent of Patients |
Age |
1.9 risk increment for each 10-year increase from 20 to 80 years |
Surgery |
|
Hip/knee |
48–61% |
Neurosurgery |
24% |
General |
19% |
Trauma |
58% |
Femoral catheter placement |
12% |
Malignancy
(lung cancer, gastrointestinal tumors) |
15% |
Previous thromboembolism |
2-9% |
Primary (genetic) hypercoagulable states |
|
Antithrombin, protein C/S deficiency |
10xrisk |
Factor V Leiden |
4x80 risk, depending on type |
Prothrombin 20210A |
4x risk |
Increased factor VIII |
6x risk |
Hyperhomocysteinemia
(high blood levels of homocysteine) |
2.5-4x risk |
Family history |
2.9x risk |
Oral contraceptive use |
2.9x risk |
Estrogen replacement |
2-4x risk |
Immobilization |
|
Bed rest of 3 days |
Start of increased incidence |
Confinement of 1, 2, and 4 weeks |
15%, 77%, 94% increase in incidence |
Prolonged air or other confined travel |
Unclear |
Pregnancy and postpartum |
0.075% of pregnancies; 2.3-6.1% per 1000 deliveries; 12% of trauma patients |
Antiphospholipid antibodies |
2-6x risk |
Inflammatory bowel disease |
Occurs in 1.2-7.1% of patients |
Obesity, varicose veins, heart attack,
congestive heart failure |
All variable |
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Modified from Gloviczki P, Yao, JST, eds: Handbook of Venous Disorders, 2nd ed. London: Arnold, 2001, p. 38. |
Figure 1
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Risk of recurrent thrombosis is greatest within the first 3 weeks after anticoagulant therapy, probably because of the difficulty in attaining constant levels of adequate anticoagulation (Figure 1).
Figure 1. Cumulative incidence of recurrent thrombotic events during the first 3 weeks of therapy. (Awaiting permission from Caps MT, Meissner MH, Tullis MJ, et al. Venous thrombus stability during acute phase of therapy. Vascular Medicine 1999;4:9–14.)
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