Superior Vena Cava Syndrome

Superior vena cava syndrome (SVCS) is a collection of symptoms resulting from the obstruction of the superior vena cava (SVC), a short, wide vessel responsible for transporting blood into the heart. This condition is frequently associated with malignant tumours within the mediastinum, particularly lung cancer and non-Hodgkin's lymphoma, which compress or invade the SVC.

Non-malignant causes are also on the rise, often due to the increased use of intravascular devices like central venous catheters, pacemakers, and defibrillator leads, leading to thrombosis. Other non-malignant causes include benign mediastinal tumours, aortic aneurysms, infections, and fibrosing mediastinitis.

Signs and Symptoms

SVCS typically presents with an array of symptoms, the most common being shortness of breath followed by swelling of the face and arms. Additional symptoms include:

• Difficulty breathing
• Headache
• Facial swelling
• Venous distention in the neck and upper chest
• Migraines
• Significant decrease in lung capacity
• Facial swelling after bending or lying down
• Upper limb oedema
• Lightheadedness
• Cough
• Oedema of the neck, known as the collar of Stokes
• Pemberton's sign

These symptoms tend to develop gradually as the underlying malignancy grows in size or invasiveness.

Cause

Over 80% of SVCS cases are due to malignant tumours compressing the SVC. Lung cancer, particularly small cell carcinoma, accounts for 75-80% of these cases, while non-Hodgkin lymphoma accounts for 10-15%. Other rare malignant causes include Hodgkin's lymphoma, metastatic cancers, leukaemia, leiomyosarcoma of the mediastinal vessels, and plasmocytoma. Non-malignant causes can include syphilis and tuberculosis. The condition can result from direct invasion or compression by a pathological process or from a deep vein thrombosis in the SVC itself.

Diagnosis

Diagnosis of SVCS primarily involves imaging techniques like chest X-rays (CXR) and CT scans, along with procedures such as transbronchial needle aspiration at bronchoscopy and mediastinoscopy. CXRs can reveal mediastinal widening and may identify the underlying cause of SVCS. However, in 16% of cases, the chest X-ray appears normal. Contrast-enhanced CT scans of the neck, chest, lower abdomen, and pelvis can also show the underlying cause and the extent of the disease.

Treatment

Treatment options for SVCS include both pharmacological and surgical interventions. Glucocorticoids such as prednisone or methylprednisolone are used to reduce the inflammatory response and oedema surrounding the tumour, particularly if the tumour is steroid-responsive, such as in cases of lymphoma. Diuretics like furosemide can help reduce venous return to the heart, alleviating increased pressure.

In acute settings, endovascular stenting performed by an interventional radiologist can provide symptom relief within 12-24 hours with minimal risks.

Respiratory assistance, if needed, should be given with extreme care to avoid further compressing the already compromised SVC, which could reduce venous return and subsequently decrease cardiac output and cerebral and coronary blood flow. Spontaneous respiration should be maintained during endotracheal intubation until sedation allows for the proper placement of an ET tube, and reduced airway pressures should be employed whenever possible.

Prognosis

Radiation therapy usually relieves symptoms within one month of treatment. However, despite treatment, the prognosis remains poor, with 99% of patients succumbing to the underlying malignancy within two and a half years. This high mortality rate is linked to the cancerous causes of SVCS, which account for 90% of cases. The average age of onset is 54 years.

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Self-assessment MCQs (single best answer)

What is the main cause of Superior Vena Cava Syndrome (SVCS)?

Which type of cancer is most commonly associated with SVCS?

What is a common non-malignant cause of SVCS?

Which imaging technique is primarily used to diagnose SVCS?

What symptom is most commonly associated with SVCS?

Which pharmacological treatment is used to reduce oedema in SVCS?

What is the average age of onset for SVCS?

What percentage of SVCS cases are due to malignant tumours?

Which syndrome involves the oedema of the neck?

What is the prognosis for patients with SVCS caused by cancer?