Robert Beatty, MD FACEP
Pulmonary embolism (PE) is a serious and potentially life-threatening condition that occurs when a blood clot travels to the lungs, obstructing blood flow. This article aims to discuss the signs, symptoms, diagnosis, and treatment of PE, including the application of the d-dimer, Wells score for risk stratification, and also PERC rules.
Signs and Symptoms
The signs and symptoms of PE can vary widely depending on the size of the blood clot and also the area of the lung affected. Common symptoms include sudden onset shortness of breath, chest pain, cough, and also hemoptysis (coughing up blood). Other symptoms also include rapid or irregular heartbeat, sweating, and fainting.
Diagnosis of Pulmonary Embolism
Diagnosing PE can be challenging because its symptoms can be similar to those of other conditions. To diagnose PE, doctors use various tests, including a chest X-ray, computed tomography (CT) scan, ventilation-perfusion (V/Q) scan, and also ultrasound.
The d-dimer blood test is also a common tool used to diagnose PE. D-dimer is a protein fragment that is released when a blood clot dissolves. If the d-dimer test is negative, PE is unlikely, and no further testing is needed. However, if the d-dimer test is positive, further testing, such as a CT scan or ultrasound, is required to confirm the diagnosis.
Wells Score for Pulmonary Embolism
The Wells score used to assess the pre-test probability of a patient having PE. The Wells score takes into account various factors, such as the presence of clinical symptoms and risk factors, to determine the likelihood of PE. If the Wells score is low, a negative d-dimer test result can effectively rule out PE without further testing. However, if the Wells score is intermediate or high, further testing is required.
Wells Criteria for Pulmonary Embolism
| Risk Factor | Points |
|---|---|
| Active cancer (treatment ongoing, within 6 months, or palliative) | 1 |
| Calf swelling >3 cm compared with the asymptomatic side (measured 10 cm below tibial tuberosity) | 1 |
| Recently bedridden for more than 3 days, or major surgery within 4 weeks | 1 |
| Unilateral lower limb pain | 1 |
| Unilateral lower limb swelling | 1 |
| Hemoptysis | 1 |
| Previous deep vein thrombosis or pulmonary embolism | 1 |
| Heart rate >100 beats/min | 1 |
| Clinical signs of deep vein thrombosis | 3 |
Score Interpretation:
| Score | Probability of PE | Suggested Action |
|---|---|---|
| ≤0 | Low probability | Consider D-dimer or imaging, based on PERC score |
| 1-4 | Moderate probability | Consider D-dimer or imaging, based on physician judgement |
| ≥4 | High probability | Consider imaging |
PERC Rule
The Pulmonary Embolism Rule-out Criteria (PERC) score is another tool used to assess the probability of a patient having PE. The PERC score is a set of eight criteria that can be used to exclude pulmonary embolism without further testing. If all eight criteria are met, PE is unlikely, and no further testing is required.
PERC (Pulmonary Embolism Rule-out Criteria) Score
| Risk Factor | Points |
|---|---|
| Age <50 | 0 |
| Heart rate <100 beats/min | 0 |
| SaO2 >94% on room air | 0 |
| No unilateral leg swelling | 0 |
| No hemoptysis | 0 |
| No prior DVT/PE | 0 |
| No surgery or trauma requiring hospitalization within 4 weeks | 0 |
| No prior PE/DVT and on anticoagulant therapy | 0 |
| No hormone use or active cancer | 0 |
Treatment
The treatment of PE depends on the severity of the condition (clot burden and also patient stability). Treatment options include anticoagulant therapy, thrombolytic therapy, and also surgical intervention.
Anticoagulant therapy is the primary treatment for most cases of PE. This treatment involves using blood thinners, such as heparin and warfarin, to prevent the formation of new blood clots and to dissolve existing clots.
Thrombolytic therapy is also an option and involves using medication to dissolve the blood clot and is typically reserved for severe cases of PE.
Surgical intervention, such as pulmonary embolectomy, may be necessary in rare cases where the blood clot is large and causing significant obstruction to blood flow.
Anticoagulation Options for Pulmonary Embolism
The following table provides a comparison of the most commonly used anticoagulants for the treatment of PE:
| Anticoagulant | Mechanism of Action | Duration of Activity | Common Side Effects | Contraindications |
|---|---|---|---|---|
| Unfractionated Heparin | Binds to antithrombin III to enhance its anticoagulant activity | Short-acting (hours) | Bleeding, heparin-induced thrombocytopenia | Active bleeding, severe thrombocytopenia, heparin-induced thrombocytopenia |
| Warfarin | Inhibits vitamin K-dependent clotting factors | Long-acting (days to weeks) | Bleeding, skin necrosis, drug interactions | Pregnancy, active bleeding, severe liver disease |
| Direct Oral Anticoagulants (DOACs) | Directly inhibit clotting factors | Intermediate-acting (hours to days) | Bleeding, gastrointestinal side effects | Severe liver disease, pregnancy, history of intracranial bleeding |
| Apixaban | Inhibits factor Xa | Intermediate-acting (hours to days) | Bleeding, gastrointestinal side effects | Severe liver disease, pregnancy, history of intracranial bleeding |
| Rivaroxaban | Inhibits factor Xa | Intermediate-acting (hours to days) | Bleeding, gastrointestinal side effects | Severe liver disease, pregnancy, history of intracranial bleeding |
| Edoxaban | Inhibits factor Xa | Intermediate-acting (hours to days) | Bleeding, gastrointestinal side effects | Severe liver disease, pregnancy, history of intracranial bleeding |
| Fondaparinux | Binds to antithrombin III to enhance its anticoagulant activity | Long-acting (days) | Bleeding | Severe renal impairment, active bleeding |
Choosing the Correct Anticoagulant
The choice of anticoagulant therapy depends on various factors, including the patient’s age, medical history, and also kidney function. Direct oral anticoagulants (DOACs) are becoming more commonly used as they have similar efficacy to traditional anticoagulants but with fewer drug interactions and no need for regular blood monitoring. However, patients with renal impairment may require dose adjustments or alternative anticoagulants.
Pulmonary Embolism Severity Index (PESI) Score
The Pulmonary Embolism Severity Index (PESI) score is a tool used to predict the severity of PE and to also guide treatment setting decisions. The PESI score takes into account various factors, such as age, comorbidities, and vital signs, to assess the patient’s risk of mortality and the need for hospitalization.
| Variable | Score |
|---|---|
| Age (years) | 1 point per year of age |
| Male gender | yes: +10 |
| History of cancer | yes: +30 |
| Chronic heart failure | yes: +10 |
| Chronic lung disease | yes: +10 |
| Pulse (beats/min) | ≥110: +20 |
| Systolic blood pressure (mmHg) | <100: +20 |
| Respiratory rate (breaths/min) | ≥30: +20 |
| Temperature (°C) | <36°C/96.8°F: +20 |
| Arterial oxygen saturation (%) | <90%: +20 |
| Altered Mental Status | disorientation, lethargy, stupor, or coma: +60 |
The PESI score has been validated in multiple studies and has also been shown to be a reliable predictor of 30-day mortality, with higher scores indicating a greater risk of mortality. Patients with low PESI scores (very low to low risk) can typically be managed on an outpatient basis, while those with higher scores require hospitalization.
Using the PESI score, patients can be classified into the following risk categories:
| Very Low Risk | PESI score of 1-65 low risk of early mortality | Outpatient management or short-stay observation unit |
| Low Risk | PESI score of 66-85 low risk of early mortality | Outpatient management short-stay observation unit |
| Intermediate Risk | PESI score of 86-105 Intermediate risk of early mortality | May require hospitalization and more aggressive treatment |
| High Risk | PESI score of 106-125 high risk of early mortality | Hospitalization and aggressive treatment, such as thrombolytic therapy |
| Very High Risk | PESI score > 125 very high risk of early mortality | Immediate hospitalization and aggressive treatment |
Conclusion
PE is a serious condition that requires prompt diagnosis and also treatment to prevent serious complications. The d-dimer test, Wells score, and PERC rules are useful tools in diagnosing PE. Anticoagulant therapy is the primary treatment for most cases of PE, and the choice of anticoagulant also depends on various factors, including the patient’s age, medical history, and kidney function. The PESI score is also a useful tool for predicting the severity of PE and guiding treatment decisions.
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