Pulmonary Embolism

1. Immobility: Bedridden patients, long-distance travellers (flights >4 hours), and sedentary office workers.
2. Post-Surgery/Medical: Particularly after orthopaedic surgeries (Hip/Knee replacement) or cancer surgeries.
3. Physiological Factors: Obesity, Advanced age (>60 years), Smoking, Pregnancy, or Postpartum period.
4. Medications: Use of oral contraceptives or Hormone Replacement Therapy (HRT).
5. Autoimmune & Systemic Diseases: Chronic inflammation such as Systemic Lupus Erythematosus (SLE) and Anti-phospholipid Syndrome.
6. Medical History: Heart disease, Interstitial Lung Disease (ILD), COVID-19, or a prior history of PE.
7. Genetic Blood Disorders: Coagulation factor abnormalities (e.g., Factor V Leiden mutation), deficiency in anticoagulants (Protein C, Protein S), or Anti-phospholipid antibodies.
8. Venous Structural Abnormalities: Recurrent phlebitis inducing deep vein thrombosis (DVT). During pregnancy, the foetus compresses veins, obstructing lower limb blood flow and increasing clot risk.

How Pulmonary Embolism Affects the Body

When a clot blocks the pulmonary artery, it deals a multiple blow to the body:

• Gas Exchange Failure: Blood cannot flow through the blocked alveoli, preventing inhaled oxygen from entering the bloodstream, causing oxygen levels to plummet.
• Heart Strain: To push blood past the blockage, the right ventricle must withstand immense pressure. This can lead to right ventricular dilation or acute failure.
• Tissue Death: Damaged lung tissue may die due to lack of blood flow (infarction), causing severe chest pain.

Common symptoms and signs include:

• Sudden shortness of breath.
• Chest pain, often pleuritic and worse with deep breathing or coughing.
• Coughing up blood-streaked sputum.
• Fast heart rate.
• Low blood pressure, dizziness, cold sweats, or fainting in severe cases.

About 70% of pulmonary emboli originate from deep vein thrombosis in the legs. Seek urgent medical attention if you notice one-sided leg swelling, tenderness, warmth, or redness.

Doctors use a combination of imaging, blood tests and clinical assessment to diagnose PE.

Gold Standard Diagnosis:

• Computer Tomography Pulmonary Angiography (CTPA):

Uses intravenous contrast dye and high-resolution CT scanning to visualize the pulmonary arteries directly. It identifies “filling defects” (clots) effectively but involves high radiation risk.

Alternatives and Adjuncts:

• V/Q Scan (Ventilation/Perfusion Scan): Suitable for patients who are allergic to contrast dye or cannot be exposed to high radiation (i.e. pregnant) as well as poor renal function. Small dose of harmless radioactive gas was inhaled to mark areas of the lung with good air perfusion that showed up in a scanner. Another type of radioactive tracker is injected through the blood vessels which also shows up in the scanner.  It compares the balance between lung “airflow” and “blood flow.” If there is a mismatch, pulmonary embolism is suspected.
• Doppler Ultrasound (Lower Limbs): Use of ultrasound to locate the source of the clot commonly found in the lower limb’s deep veins. 
• Echocardiogram: Used of ultrasound to assess the severity of pulmonary embolism based on cardiac findings particularly in those with unstable cases which warrant urgent intervention.
• Blood Tests:
  • D-Dimer: Used for preliminary exclusion. A negative result usually indicates no blood clot is present.
  • Secondary Cause Screening: Testing for Protein C, Protein S, and Anti-phospholipid antibodies to rule out congenital coagulation disorders or autoimmune diseases.

Invasive Investigation:

• Catheter Pulmonary Angiography:

When major pulmonary arteries are suspected to be involved, doctors may opt for this invasive method. It serves both diagnostic and therapeutic purposes. A catheter is inserted through a large vein in the thigh and advanced near the heart. Contrast is injected for real-time X-ray imaging, allowing for immediate intervention if a clot is found.

Blood Thinning Therapy (Anticoagulation)

Treatment duration depends on the cause of the clot and the risk of recurrence, ranging from 3 months to lifelong.

1. Low Molecular Weight Heparin (LMWH / Enoxaparin):
   It is a fast-acting blood thinner given as a small injection just under the skin. It is commonly used to treat or prevent blood clots during hospital stay.
2. Novel Oral Anticoagulants (NOACs):
   (e.g.., Apixaban, Rivaroxaban, Edoxaban, Dabigatran)
   Unlike older blood thinners, these newer medications don’t require regular blood tests or any changes to your diet. They are highly effective and have a proven safety record compared to traditional treatments.
3. Warfarin:
   While older blood thinners require frequent blood draws and a steady intake of Vitamin K-rich foods, they remain the best choice for certain conditions. Specifically, they provide superior protection against blood clots for people with Antiphospholipid Syndrome or those with severely impaired kidney function.

Advanced Interventional Therapy:

• Systematic thrombolysis: For patients who do not respond to standard blood thinners—and where specialized clot-removal procedures are unavailable—systemic ‘clot-busting’ medication (thrombolysis) may be utilized after carefully evaluating bleeding risks. 
• Catheter based- Thrombectomy/ Thrombolysis: For severe clots causing unstable blood pressure, doctors can use a catheter-based treatment. This involves threading a tiny tube directly to the clot to break it up with ‘clot-busting’ medication or to remove it physically.
• Surgical Thrombectomy: In rare or critical situations where a clot is too large to be treated with medicine alone, a surgical embolectomy may be performed. A surgeon makes an incision to access the lung arteries and manually removes the blockage. This is a major, but life-saving procedure used to quickly restore blood flow and relieve the strain on your heart when other treatments aren’t an option.

Alternative Therapy:

Inferior Vena Cava (IVC) Filter:  An IVC filter is a tiny, umbrella-shaped device placed in your main vein to catch blood clots before they reach the lungs. It is typically used when blood thinners are unsafe (due to high bleeding risk / impending surgery) or when medication isn’t enough (recurrent clot still). 

Short-term concerns (Immediate to 3 months) (4,16,17)

• Death: A large clot can block blood flow to the heart, causing it to stop (cardiac arrest). Without prompt medical treatment, this condition can be fatal. In fact, nearly 30% of people with an untreated PE do not survive.
• Strain on the heart: The lungs usually have low blood pressure. A clot creates a “bottleneck,” forcing the heart to work much harder to pump blood through. Over time, this constant stress can weaken the heart muscle causing heart failure.
• Lung tissue damages: Lung tissue needs blood supply to stay alive. If a clot cuts off that supply, it can causes permanent scarring or tissue death. This may result in sharp chest pain and coughing up blood.
• Blood clot recurrence: Recurrence of clot is highest within first 3 months of initial event. Use of blood thinners helps to prevent this from happening again. 
• Bleeding risk: Commonest side effect of blood thinning agents is bleeding. This often happen within the digestive system causing stomach pain or bloody stool. While this sounds scary, bleeding itself is treatable and far less dangerous than the blood clot within the lung circulation. 

Long-term concerns ( 3 months to years)

• CTEPH (Chronic Thromboembolic Pulmonary Hypertension): If the clot does not dissolve completely, it causes scarring within the vessels. This permanently narrows the blood vessels therefore increases blood pressure within the lungs. This leads to long-term shortness of breath and eventual heart failure. Confirmation of this disease is mainly by ECHO assessment after 3 months as well as invasive right heart catheterisation in ambiguous cases. 
• Post PE syndrome: Despite adequately treated PE, some patients may experience shortness of breath, fainting, fatigue, chest pain and reduced exercise tolerance due to residual blood clot partially affecting blood supply to the lung. This is diagnosed by functional testing such as cardiopulmonary exercise testing (CPET) or stress ECHO. 

• Physical Prevention: Wear medical-grade15 – 30mmHg compression stockings to promote venous return. For high-risk patients or those with inability to tolerate compression stockings, a device called intermittent pneumatic compression (IPC) can be used as alternative to promote venous return. 
• Hydration: Drink plenty of water to reduce blood viscosity and avoid excessive caffeinated drinks and alcohol which depletes fluid within the body.
• Regular Movement: Post-operative patients should get out of bed early as per doctor’s orders. Sedentary workers should stand and move for 5-10 minutes every 30 to 60 minutes.
• Ankle Exercises: While sitting, perform “Ankle Pumps” (pulling toes up and down) to squeeze calf muscles in 15 – 20 beats per minute for 5 minutes to aid blood flow. 
• Prophylactic Anticoagulation: Use of LMWH or NOAC to prevent thromboembolic events in high-risk individuals (e.g. prior to long-haul flights, hospitalized patients, history of PE, cancer, or COVID-19 patients).