Pulmonary embolism risk factors

Resident Survival Guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] The APEX Trial Investigators; Associate Editor(s)-in-Chief: Rim Halaby, M.D. [2]

Overview[edit | edit source]

The most common sources of pulmonary embolism (PE) are proximal leg deep venous thromboses (DVTs) or pelvic vein thromboses; therefore, any risk factor for DVT also increases the risk of PE. Approximately 15% of patients with a DVT will develop a PE. In these chapters on venous thromboembolism (VTE), the word risk factors refers to those epidemiologic and genetic variables that expose someone to a higher risk of developing venous thrombosis. The word triggers refer to those factors in the patients immediate history or environment that may have lead to the occurrence of the venous thrombosis. The risk factors for VTE are a constellation of predisposing conditions which stem from the three principles of Virchow's triad: stasis of the blood flow, damage to the vascular endothelial cells, and hypercoagulability. Approximately 5 to 8% of the U.S. population has one of several genetic risk factors, also known as inherited thrombophilias in which a genetic defect can be identified that increases the risk for thrombosis.^[1][2] The risk factors for VTE can be classified as temporary, modifiable and non-modifiable. It is suggested that venous thrombosis also shares risk factors with arterial thrombosis, such as obesity, hypertension, smoking, and diabetes mellitus.^[3]

Risk Factors[edit | edit source]

Shown below is a list of predisposing factors for VTE.^[4][5] The risk factors are classified as moderate or weak depending on how strongly they predispose for a VTE.

The risk factors of VTE can be further classified into modifiable, non-modifiable and temporary.

Modifiable Risk Factors[edit | edit source]

Modifiable risk factors are reversible based upon lifestyle/behavior modification.

• Obesity: Obesity is defined as a body-mass index (BMI) above 30 kg/m2.^{[6] [7] [8]}

• Smoking:^[6] Smoking significantly increases the risk of DVT, particularly among women who are taking oral contraceptive pills as well as among obese people.

• Use of oral contraceptives^[9]

• Hyperhomocysteinemia:^[10] Hyperhomocysteinemia can be reduced with vitamin B supplementation.

Non-Modifiable Risk Factors[edit | edit source]

• Advanced age
• Heart failure
• Thrombophilia or hypercoagulable state
  • Factor V Leiden
  • Prothrombin G20210A mutation
  • Protein C deficiency
  • Protein S deficiency
  • Antithrombin deficiency
  • Activated protein C resistance
  • Antithrombin III deficiency
  • Factor VIII mutation
  • Antiphospholipid syndrome
  • Heparin induced thrombocytopenia
  • Nephrotic syndrome
  • Paroxysmal nocturnal hemoglobinuria
• Polycythemia vera

Temporary Risk Factors[edit | edit source]

• Pregnancy and the peri-partum period
• Active cancer
• Central venous catheter

Other Possible Risk Factors[edit | edit source]

Other possible factors associated with VTE include:

• Nutrition low in fish, fruits, and vegetables^[11]
• Psychological stress^[12]
• Cardiovascular risk factors such as diabetes and hypercholesterolemia^[13]
• Acute medical illness
• Drug abuse (intravenous drugs)^[14]
• Sickle cell disease^[15]
• Inflammatory bowel disease^[16]
• Antipsychotic drugs^[17]
• Thrombocytosis^[18]
• Varicose veins^[19][20]

Risk Factors from the Nurse's Health Study[edit | edit source]

The Nurse's Health Study (NHS) investigated the risk factors for PE among 112,822 female subjects. The factors that are associated with increased PE in women are obesity, smoking, and hypertension. According to this study the relative risk (RR) and confidence interval (CI) for the occurrence of idiopathic VTE for each of the following factors are:^[21]

• Obesity: RR 2.9 (95% CI, 1.5-5.4)
• Smoking:
  • 25 – 34 cigarettes per day: RR 1.9 (95% CI, 0.9-3.7)
  • More than 35 cigarettes per day: RR 3.3 (95% CI, 1.7-6.5)
• Hypertension: RR 1.9 (95% CI, 1.2-2.8)
• Hypercholesterolemia: 1.1 (95% CI, 0.62-1.8)
• Diabetes: RR 0.7 (95% CI, 0.3-1.9)

In addition, surgery, trauma, cancer and immobilization are associated with provoked PE.

Risk Factors from the Physician's Health Study[edit | edit source]

The following factors have been associated with elevated risk of VTE among subjects in the Physicians Health Study. The relative risk for the occurrence of VTE among patients who have these factors compared to those who don't is provided below.

• Anticardiolipin antibody level above the 95th percentile (RR: 5.3; 95% CI, 1.55 to 18.3; P = 0.01)^[22]
• Factor V Leiden (RR: 2.7; 95% CI, 1.3 to 5.6; P = 0.008)^[23]

References[edit | edit source]

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