Superior vena cava syndrome (SVC obstruction): symptoms, causes and treatment

The superior vena cava, often shortened to SVC, is a large vein in the middle of the chest, behind the breastbone. Macmillan explains that it carries blood from the head, neck, arms and upper chest straight to the heart. Its walls are thin and can easily become squashed or compressed. When blood flow along the vein is blocked, pressure rises in the head, neck and arms, producing the symptoms of the syndrome.

The condition is called superior vena cava obstruction (SVCO) or superior vena cava syndrome. In most people it is a complication of cancer in the chest rather than a disease in its own right, so treatment is directed at both the blockage and the underlying cause.

Macmillan says most cases of SVCO are caused by lung cancer. The cancer may press directly on the SVC, or it may spread to nearby lymph nodes, which become swollen and press on the vein. Other cancers affecting lymph nodes in the chest can do the same, including lymphomas and testicular, breast, bowel or oesophageal cancers.

A blood clot forming in the vein can also block it, which Macmillan says can happen if you have had a central line put into the vein, for example to give chemotherapy. Because SVC syndrome is sometimes the first sign of an undiagnosed cancer, doctors look for the cause as part of the same assessment.

Macmillan explains that symptoms are caused by blood flow to the heart being blocked, which increases pressure in the head, neck and arms. They can develop quickly over a few days or more gradually over a few weeks.

• Breathlessness, because of swelling around the windpipe.

• Headaches or a feeling of fullness in the head that get worse when you lean forward or bend over.

• Facial swelling, with changes to your natural skin colour and appearance.

• Changes in eyesight.

• A swollen neck, and swollen arms and hands.

• Visible swollen veins on the chest.

• Feeling dizzy.

Macmillan says that if you have any of these symptoms it is important to contact your cancer doctor or nurse straight away, because SVCO needs to be treated quickly. If you have not been diagnosed with cancer, the NHS lists swelling of the face or neck among the less common symptoms of lung cancer and advises seeing a GP for any symptoms of lung cancer.

The NHS advises calling 999 or going to A&E if you are struggling to breathe, such as choking, gasping and unable to speak, or have pain in your chest or upper back. Do not drive yourself; ask someone to drive you or call 999 for an ambulance.

Macmillan says the most common tests to diagnose SVCO are a chest X-ray or a CT scan, and you might also have an MRI scan or an ultrasound. In someone not already known to have cancer, further tests such as a biopsy are then used to identify the underlying cause, because that determines treatment. The NHS explains that for suspected lung cancer the main tests are a CT scan and a bronchoscopy, with further scans, a biopsy, blood tests and genetic testing if cancer is found.

Macmillan says the symptoms of SVCO can be distressing but can usually be quickly controlled. You may be given oxygen to improve breathing, and drugs such as painkillers, water tablets (diuretics) and sedatives. Your doctor may give high doses of a steroid, dexamethasone, to reduce pressure and swelling around the blood vessel, and usually advises bed rest with the head of the bed raised.

Macmillan says having SVCO can be very worrying, but treatments will improve the symptoms, and your cancer team will give you support. The longer-term outlook depends largely on the underlying cancer and how well it responds to treatment, which your specialist team can explain in your situation.

Let your team know how you are feeling. Macmillan encourages talking to family and friends and offers a support line and online community for people affected by cancer.

SVCO is dealt with as an emergency through the NHS cancer team or emergency department, with oncology, radiology and sometimes cardiothoracic input. Cancer treatment on the NHS is free at the point of use.

Private cancer centres may offer stenting or radiotherapy, but because the situation is urgent and depends on rapid imaging and specialist coordination, most people are treated through their existing NHS cancer team. Ask your team who to contact out of hours.