Pulmonary embolism risk factors
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Associate Editors-in-Chief: Ujjwal Rastogi, MBBS [2]
Synonyms and keywords: PE
Risk Factors
The most common sources of embolism are proximal leg deep venous thrombosis (DVTs) or pelvic vein thromboses. Any risk factor for DVT also increases the risk that the venous clot will dislodge and migrate to the lung circulation, which happens in up to 15% of all DVTs. The conditions are generally regarded as a continuum termed venous thromboembolism (VTE).
The development of thrombosis is classically due to a group of causes named Virchow's triad (alterations in blood flow, factors in the vessel wall and factors affecting the properties of the blood). Often, more than one risk factor is present.
- Alterations in blood flow: immobilization (after surgery, injury or long-distance air travel), pregnancy (also procoagulant), obesity (also procoagulant)
- Factors in the vessel wall: of limited direct relevance in VTE
- Factors affecting the properties of the blood (procoagulant state):
- Estrogen-containing hormonal contraception
- Genetic thrombophilia (factor V Leiden, prothrombin mutation G20210A, protein C deficiency, protein S deficiency, antithrombin deficiency, hyperhomocysteinemia and plasminogen/fibrinolysis disorders).
- Acquired thrombophilia (antiphospholipid syndrome, nephrotic syndrome, paroxysmal nocturnal hemoglobinuria)
Risk Factors Identified in the PIOPED Study Independent risk factors identified in prospective investigation of pulmonary embolism diagnosis (PIOPED) include:
- Immobilization.
- Surgery within the last 3 months, and stroke were also risk factors, but may also relate to immobility.
- History of venous thromboembolism.
- Cancer: found in up to 17% of patients with an idiopathic deep vein thrombosis (DVT).
Risk Factors from the Nurses' Health Study
- Obesity: RR 2.9
- Smoking: 25 – 34 cigarettes / d (RR 1.9), > 35 cig / d (RR 3.3)
- Hypertension: RR 1.9
- Oral contraceptives: RR ~ 2 – 3
- Hormone replacement therapy: RR ~ 2
Risk Factors from the Physician's Health Study
- Factor V Leiden: RR 2.7, found in 40% of patients with idiopathic DVT.
- Use of oral contraceptives by a person with the Factor V mutation increases the risk of venous thromboembolism 35 fold.
- Hyperhomocysteinemia increases the risk of a DVT by a factor of 3.
- Hyperhomocysteinemia with Factor V increases the risk of a DVT by 10 fold.
- Lupus anticoagulant was found in 8.5% of patients with idiopathic DVT.