Pulmonary Embolism (PE)

This article was contributed by Dr Mohd Al-Baqlish B. Mohd Firdaus. Consultant Cardiologist & Internal Medicine, at Pantai Hospital Melaka. To know more about where and when to see Dr Mohd Al-Baqlish at his clinic, click here.

Critical Cardiopulmonary Emergency

Pulmonary embolism (PE) is a potentially life-threatening medical condition that occurs when a blood clot, or sometimes other material such as fat or air, becomes lodged in the arteries of the lungs, blocking the normal flow of blood. This obstruction can cause significant damage to the lung tissue, strain the heart, and, in severe cases, result in sudden death. Early recognition and intervention are crucial to improve outcomes for those affected by PE. In this article, we will explore the causes, risk factors, clinical presentation, diagnostic approaches, treatment modalities, and preventive strategies related to pulmonary embolism.

What is Pulmonary Embolism?

Pulmonary embolism is an acute blockage of one or more pulmonary arteries by material that has travelled from elsewhere in the body, most commonly a thrombus (blood clot) originating in the deep veins of the legs or pelvis. This process is part of a broader condition known as venous thromboembolism (VTE), which encompasses both deep vein thrombosis (DVT) and pulmonary embolism. The classic scenario involves a clot forming in the deep veins, breaking free, traveling through the right side of the heart, and finally lodging in the lung arteries. In some cases, the resulting blockage can even lead to pulmonary infarction, where lung tissue dies due to lack of blood supply.

Depending on the size and location of the embolus, as well as the overall health of the patient, PE can range from being asymptomatic or mild to causing massive, fatal cardiovascular collapse. For some individuals, the presence of recurrent pulmonary embolism can increase risks of long-term complications and warrant close medical follow-up.

Causes and Risk Factors

The most common cause of pulmonary embolism is the migration of a blood clot from the deep veins of the lower extremities or pelvis. However, other materials such as fat (from bone fractures), air (from medical procedures), tumour cells, or amniotic fluid (in pregnancy) can also rarely cause PE.

Several factors increase the risk of developing blood clots and, subsequently, pulmonary embolism. These include:

• Prolonged Immobility: Extended bed rest, long-haul flights, or car rides can lead to blood pooling in the legs and contribute to clot formation.
• Surgery or Trauma: Especially orthopaedics surgery of the legs, hips, or pelvis, and major injuries that damage veins and blood vessels.
• Medical Conditions: Cancer, heart failure, stroke, and certain genetic blood clotting disorders (thrombophilia).
• Lifestyle Factors: Smoking, obesity, pregnancy, and the use of estrogen-containing medications, such as birth control pills or hormone replacement therapy, increase the risk.
• Age: The risk increases with age, particularly over 60.
• History of Prior Clots: Individuals who have had DVT or pulmonary embolism before are at higher risk of recurrence.

Symptoms and Clinical Presentation

The symptoms of pulmonary embolism can vary widely, depending on the size of the embolus and the degree of blockage in the pulmonary arteries. Some people experience mild or subtle symptoms, while others may collapse suddenly. Common pulmonary embolism symptoms include:

• Sudden Shortness of Breath: This is the most frequent symptom, often occurring without warning.
• Chest Pain: Typically sharp and worsens with deep breaths (pleuritic pain), but can also be vague and persistent.
• Cough: Sometimes accompanied by bloody or blood-streaked sputum (haemoptysis).
• Rapid Heart Rate (tachycardia) and palpitations.
• Light headedness or Fainting (syncope), especially in massive PE.
• Signs of Deep Vein Thrombosis: Swelling, redness, or pain in the leg, usually the calf.

In severe cases, pulmonary embolism can lead to shock, low blood pressure, cardiac arrest, and sudden death. Silent or subclinical PEs may go unnoticed, but still carry risks for long-term complications.

Diagnosis

The diagnosis of pulmonary embolism is challenging due to the non-specific nature of its symptoms, which overlap with many other cardiopulmonary conditions. A thorough clinical assessment is essential, often guided by risk stratification tools such as the Wells score or the revised Geneva score.

Diagnostic Steps Include:

• Clinical Evaluation: Detailed history, physical examination, and assessment of risk factors.
• Laboratory Tests: D-dimer blood test can help rule out PE in low-risk patients. D-dimer is a byproduct of clot breakdown and is elevated in most patients with acute PE, but it is not specific.
• Imaging Studies:
• CT Pulmonary Angiography (CTPA): The gold standard for diagnosis. It visualises the pulmonary arteries and detects clots directly.
• Ventilation-Perfusion (V/Q) Scan: Used when CTPA is contraindicated (e.g., in kidney failure or pregnancy). It assesses the air and blood flow in the lungs to identify mismatches suggestive of PE.
• Ultrasound of the Legs: Can help detect DVT, supporting a pulmonary embolism diagnosis.
• Echocardiography: Can show right heart strain in severe cases.
• Chest X-ray: Often normal but can reveal alternative diagnoses.

Treatment and Management

The primary goals in managing pulmonary embolism are to prevent further clot formation, dissolve the existing clot, restore normal pulmonary blood flow, and reduce the risk of recurrence. The urgency and type of treatment depend on the severity of the PE and the patient's underlying health.

Main Treatments Include:

• Anticoagulation: Blood thinners such as heparin, low-molecular-weight heparin, warfarin, or direct oral anticoagulants (DOACs) are the cornerstone of treatment. They prevent new clots from forming and allow the body to dissolve existing ones.
• Thrombolytic Therapy: In life-threatening or massive PE with cardiac instability (shock or hypotension), clot-dissolving medications (thrombolytics) may be administered. These drugs carry a higher risk of bleeding.
• Surgical or Catheter-Based Intervention: Rarely, in cases where medications are ineffective or contraindicated, procedures such as surgical embolectomy or catheter-directed thrombolysis may be performed to remove or dissolve the clot.
• Inferior Vena Cava (IVC) Filter: A filter may be placed in the large vein (vena cava) carrying blood from the lower body to the heart, especially if there is a contraindication to anticoagulation. It helps prevent clots from reaching the lungs.
• Supportive Care: Oxygen therapy, fluids, and medications to support blood pressure may be necessary, especially in unstable patients.

Duration of Treatment

The length of anticoagulation therapy depends on the underlying cause, presence of risk factors, and whether the PE was a first episode or a recurrence. Typically, treatment lasts 3–6 months, but may be extended indefinitely in cases of ongoing risk.

Complications and Prognosis

Timely treatment of PE significantly improves survival rates, but the condition still carries a risk of serious complications, including:

• Chronic Thromboembolic Pulmonary Hypertension (CTEPH): Persistent high blood pressure in the lungs due to unresolved clots, leading to progressive right heart failure.
• Recurrent Venous Thromboembolism: Increased risk of future clots.
• Post-PE Syndrome: Long-term shortness of breath, reduced exercise capacity, and reduced quality of life.
• Death: Especially if diagnosis and treatment are delayed.

The overall prognosis depends on the size of the embolus, promptness of treatment, and underlying health conditions. With appropriate therapy, most patients recover fully, but ongoing follow-up is important.

Prevention

Prevention of pulmonary embolism involves identifying and mitigating risk factors, particularly in high-risk settings such as hospitalisation, surgery, or immobility. Strategies include:

• Early Mobilisation: Encouraging movement as soon as possible after surgery or during illness.
• Mechanical Prophylaxis: Use of compression stockings or pneumatic devices to improve venous blood flow in the legs.
• Pharmacological Prophylaxis: Low-dose anticoagulants in high-risk individuals, as determined by a healthcare provider.
• Lifestyle Modification: Quitting smoking, maintaining a healthy weight, regular exercise, and minimising extended periods of inactivity.

Conclusion

Pulmonary embolism is a critical and sometimes silent threat that requires vigilance from both patients and healthcare providers. Its presentation can be subtle or dramatic, making a high index of suspicion essential, especially in those with risk factors. Advances in diagnostic imaging and newer anticoagulant medications have improved the speed and safety of PE management. Prevention remains the best strategy, emphasising the importance of mobility, risk assessment, and appropriate use of blood thinners in at-risk populations.

Education about the signs and risks of pulmonary embolism, combined with timely medical intervention, can save lives and reduce the burden of this serious cardiovascular emergency.

If you or someone you know is experiencing symptoms like sudden shortness of breath, chest pain, or unexplained leg swelling, don’t wait—consult a cardiologist immediately. Early diagnosis and treatment are key.