Risk Factors for Pulmonary embolism/Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathing in and coughing up blood. Symptoms of a blood clot in the leg may also be present, such as a red, warm, swollen, and painful leg. Signs of a PE include low blood oxygen levels, rapid breathing, rapid heart rate, and sometimes a mild fever. Severe cases can lead to passing out, abnormally low blood pressure, and sudden death.
Causes of pulmonary embolism
Underlying causes
After a first PE, the search for secondary causes is usually brief. Only when a second PE occurs, and especially when this happens while still under anticoagulant therapy, a further search for underlying conditions is undertaken. This will include testing (“thrombophilia screen”) for Factor V Leiden mutation, antiphospholipid antibodies, protein C and S and antithrombin levels, and later prothrombin mutation, MTHFR mutation, Factor VIII concentration and rarer inherited coagulation abnormalities.[rx]
Probability testing
There are additional prediction rules for PE, such as the Geneva rule. More importantly, the use of any rule is associated with a reduction in recurrent thromboembolism.[rx]
The Wells score:
- clinically suspected DVT — 3.0 points
- alternative diagnosis is less likely than PE — 3.0 points
- tachycardia (heart rate > 100) — 1.5 points
- immobilization (≥ 3d)/surgery in previous four weeks — 1.5 points
- history of DVT or PE — 1.5 points
- hemoptysis — 1.0 points
- malignancy (with treatment within six months) or palliative — 1.0 points
Traditional interpretation
- Score >6.0 — High (probability 59% based on pooled data)
- Score 2.0 to 6.0 — Moderate (probability 29% based on pooled data)
- Score <2.0 — Low (probability 15% based on pooled data)
Alternative interpretation
- Score > 4 — PE likely. Consider diagnostic imaging.
- Score 4 or less — PE unlikely. Consider D-dimer to rule out PE.
Recommendations for a diagnostic algorithm were published by the PIOPED investigators; however, these recommendations do not reflect research using 64 slice MDCT.[36] These investigators recommended:
- Low clinical probability. If negative D-dimer, PE is excluded. If positive D-dimer, obtain MDCT and based treatment on results.
- Moderate clinical probability. If negative D-dimer, PE is excluded. However, the authors were not concerned that a negative MDCT with negative D-dimer in this setting has a 5% probability of being false. Presumably, the 5% error rate will fall as 64 slice MDCT is more commonly used. If positive D-dimer, obtain MDCT and based treatment on results.
Risk factors for pulmonary embolism
| Surgery (in the last 3–6 months) | |
| Fracture (hip or leg) | Hip or knee replacement |
| Arthroscopic knee Laparoscopic surgery | surgery (cholecystectomy) |
| Cancer surgery | Major trauma |
| Spinal cord injury | Major general surgery |
| Central venous lines | |
| Genetic diseases | |
| Factor V Leiden gene mutation | Prothrombin G20210A mutation |
| Protein C, S, anti-thrombin III deficiency | Increased factor VIII |
| Hyperhomocysteinemia | Antiphospholipid antibody syndrome |
| Anticardiolipin antibody syndrome | Congenital dysfibrinogenemia |
| Additional diseases | |
| Previous VTE | Congestive heart failure |
| Congestive respiratory failure | Myocardial infarction (in the last 1 month) |
| Malignancy | Nephrotic syndrome |
| Varicose veins | Paralytic stroke |
| Primary myelofibrosis | Polycythemia vera |
| Inflammatory bowel disease | |
| Others | |
| Chemotherapy | Obesity |
| Hormone replacement therapy | Bed rest > 3 days |
| Pregnancy, postpartum | Immobility due to sitting (more than 4 h) |
| Increasing age | Cigarette smoking |
References
