Risk Factors for Pulmonary Embolism Beyond Travel
The most significant risk factors for pulmonary embolism (PE) beyond travel include surgery, immobility, malignancy, pregnancy/postpartum state, older age, thrombophilia, and hormone therapy. 1
Major Risk Factors
Surgical and Medical Conditions
- Major orthopedic lower limb surgery and postoperative intensive care are associated with a high risk of PE 1
- Immobility due to stroke, neurological diseases (brain tumors, acute spinal injury), and prolonged hospitalization significantly increases PE risk 1
- Cardiorespiratory disorders, particularly myocardial infarction, congenital heart disease, congestive heart failure, and irreversible airways disease are major risk factors 1
Malignancy
- Cancer, especially of the uterus, pancreas, breast, and stomach, as well as advanced and metastatic disease, significantly increases PE risk 1
- The association between PE and occult malignancy is significant, with many patients diagnosed with PE later found to have previously undetected cancer 1
Demographic and Physical Factors
- Age is a significant risk factor, with PE risk increasing exponentially with age, particularly over 40 years 1
- Obesity has been confirmed as an independent risk factor for PE 1
Hormonal and Pregnancy-Related Factors
- Estrogen therapy increases PE risk, especially with "third generation" agents 1
- Pregnancy and postpartum state carry increased risk, particularly with pre-eclampsia, cesarean section, and multiple births 1
- While oral contraceptives increase risk 2-4 times compared to controls, the absolute risk remains low with current low-dose formulations 1
Thrombophilia
- Inherited or acquired thrombophilia (antiphospholipid syndrome, deficiencies of antithrombin III, factor V Leiden, protein C, or protein S) is found in 25-50% of patients with PE 1
- These thrombophilic factors typically need to interact with acquired risk factors before thrombosis occurs 1, 2
- Factor V Leiden mutation, present in 5% of the population and 20% of patients with thrombosis, increases PE risk 3-5 fold, but in combination with estrogen therapy, this risk rises to 35-fold 1
Other Risk Factors
Vascular Access and Procedures
- Central venous catheterization can lead to PE, though these are rarely fatal, likely because the iatrogenic clot is too small to cause major pulmonary vascular occlusion 1
- Upper limb spontaneous clots are less common and rarely lead to PE compared to lower limb thrombosis 1
Multiple Risk Factors
- The incidence of PE is particularly high when multiple risk factors are present 1
- Risk factors often interact synergistically rather than additively 1, 2
Clinical Implications
Risk Assessment
- All patients with possible PE should have clinical probability assessed and documented 1
- The presence of risk factors significantly influences the pre-test probability of PE and should guide diagnostic strategies 1
Common Pitfalls
- Not recognizing that PE risk increases exponentially with age 1
- Failing to consider thrombophilia in patients with unexplained thrombotic episodes, especially those occurring at a young age or with recurrence 2
- Overlooking the synergistic effect of multiple risk factors (e.g., oral contraceptives plus Factor V Leiden) 1
- Underestimating the significance of immobility as a risk factor, which extends beyond travel to include hospitalization and neurological conditions 1
Understanding these risk factors is crucial for appropriate risk stratification, which guides both diagnostic approaches and management decisions in patients with suspected PE 1.