What is Pulmonary Embolism?
Pulmonary Embolism (PE) is a potentially life-threatening condition where one or more arteries in the lungs become blocked by a blood clot. Most commonly, these clots originate in the deep veins of the legs (DVT) and travel to the lungs — a condition referred to as venous thromboembolism (VTE).
Mnemonic: SAM Has RED Pants – Risk Factors of PE
To help remember the major risk factors of Pulmonary Embolism, use the mnemonic:
SAM has RED Pants
| Letter | Meaning | Description |
|---|---|---|
| S | Stroke or recent MI | Immobilization or vascular damage |
| A | Atrial fibrillation | Irregular heart rhythm promotes clotting |
| M | Myocardial Infarction | Leads to endothelial injury and stasis |
| R | Recent surgery | Especially orthopedic, abdominal surgeries |
| E | Estrogen therapy | OCPs, HRT—pro-thrombotic effect |
| D | Disseminated malignancy | Cancers release procoagulant substances |
| P | Pregnancy/Postpartum | Increased clotting tendency & venous stasis |
This powerful memory tool helps clinicians, students, and even patients understand who is most at risk.
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Causes & Pathophysiology of Pulmonary Embolism
PE occurs when a blood clot (thrombus) forms and travels to the lungs. The most common source is deep vein thrombosis (DVT) in the legs. Less frequently, it can also be caused by:
- Fat emboli (e.g., long bone fracture)
- Air embolism (e.g., central line insertion)
- Amniotic fluid embolism (in pregnancy)
- Tumor embolism
When a clot blocks a pulmonary artery, oxygen exchange is impaired, causing:
- Hypoxia
- Pulmonary hypertension
- Right ventricular strain or failure
Common Risk Factors Explained
Stroke or Recent MI
After a stroke or heart attack, immobility and endothelial damage increase the chances of clot formation.
Atrial Fibrillation
Irregular atrial contractions lead to blood pooling in the heart, which encourages clot formation, especially in the left atrial appendage.
Myocardial Infarction
An MI can damage endothelial lining, trigger inflammation, and reduce blood flow, all of which are pro-thrombotic.
Recent Surgery
Post-operative patients, especially after:
- Hip/knee replacement
- Abdominal or pelvic surgery
…are at very high risk due to prolonged immobilization and vascular injury.
Estrogen Therapy
Oral contraceptives and hormone replacement therapy (HRT) increase clotting factors, especially when combined with smoking or obesity.
Disseminated Malignancy
Cancers like pancreatic, lung, or brain tumors can secrete procoagulants or compress vessels, promoting thrombosis.
Pregnancy & Postpartum
Due to:
- Hormonal changes
- Venous stasis from uterine compression
- Hypercoagulable state in pregnancy
Signs and Symptoms of Pulmonary Embolism
| Symptom | Clinical Feature |
|---|---|
| Sudden shortness of breath | Most common symptom |
| Pleuritic chest pain | Worsens with breathing or coughing |
| Tachypnea (rapid breathing) | Due to hypoxia |
| Cough (possibly with blood) | May suggest infarction or hemorrhage |
| Tachycardia | Compensatory mechanism for hypoxia |
| Syncope or collapse | Seen in massive PE |
| Leg swelling/pain (DVT sign) | Especially unilateral, often in calf region |
Diagnosis and Investigations
Blood Tests:
- D-Dimer: Elevated in presence of clot; useful for ruling out PE in low-risk patients.
Imaging:
- CT Pulmonary Angiography (CTPA): Gold standard imaging.
- Ventilation-Perfusion (V/Q) Scan: Alternative for patients who can't have contrast.
Others:
- ECG: May show S1Q3T3 pattern (classic but rare).
- Echocardiogram: RV dilation or dysfunction.
- Lower limb Doppler ultrasound: To identify DVT source.
Pulmonary Embolism in Pregnancy and Postpartum
PE is the leading cause of maternal mortality in developed countries. Risk increases due to:
- Venous stasis from uterine compression
- Increased clotting factors
- Decreased fibrinolysis
Diagnosis: V/Q scan preferred over CTPA due to fetal safety.
Treatment:
- Low Molecular Weight Heparin (LMWH) is safe during pregnancy.
- Warfarin is contraindicated.
Treatment Options
| Severity | First-line Treatment |
|---|---|
| Mild/Moderate | LMWH or DOACs (e.g., apixaban, rivaroxaban) |
| Massive PE | Thrombolysis (alteplase) |
| Surgical PE | Embolectomy or catheter-directed thrombolysis |
| Recurrent PE | IVC filter if anticoagulation contraindicated |
Prevention & Lifestyle Strategies
Preventive Measures
- Early ambulation post-surgery
- Graduated compression stockings
- LMWH prophylaxis in high-risk patients
- Avoid long immobility (e.g., during flights)
- Maintain optimal hydration
Lifestyle Tips
- Stop smoking
- Control weight
- Avoid estrogen-based medications if high risk
- Regular exercise
- Periodic screening in cancer or post-op patients
FAQs on Pulmonary Embolism
Can you die suddenly from a pulmonary embolism?
Yes. Massive PE can cause sudden death due to complete obstruction of blood flow to the lungs.
How quickly should PE be treated?
Immediately. Delay in treatment increases the risk of shock, hypoxia, and death.
Is pulmonary embolism the same as a heart attack?
No. PE is a clot in the lungs, while heart attack (MI) is a blockage in heart arteries.
Can you recover fully from PE?
Yes, with prompt treatment, many patients make a full recovery. However, some develop chronic thromboembolic pulmonary hypertension (CTEPH).
