What Is Superior Vena Cava Syndrome?

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Introduction 

Definition of superior vena cava syndrome (SVCS) 

Superior vena cava (SVC) syndrome represents the collection of symptoms when the SVC, an important blood vessel, becomes partially or completely blocked. This leads to a backlog of blood, and an increased pressure in the veins of the head, chest, neck and arms. Some common symptoms include face swelling, engorged neck and chest veins, cough and breathlessness.1 

Medical importance of SVC syndrome

SVC syndrome is a well-appreciated presentation, though it is not particularly common. The number of cases in the United States each year is around 15,000.1

Recognition is crucial because of the dangers blockage of the SVC can present, and the underlying cause needs a diagnosis to guide treatment. SVC syndrome is considered an oncological (cancer-related) emergency, but can also be caused by non-cancerous conditions.

As you will read further down, the syndrome itself is rarely a life-threatening emergency.

What is the SVC?

The SVC is a large vein draining into the heart, from the top down. It sits just behind and slightly to the right of the chest bone (sternum). Two veins join to form the SVC, the left and right brachiocephalic veins otherwise known as the innominate veins.2 The SVC differs from the inferior vena cava (IVC) which drains from below, up into the heart.

SVC and the circulatory system

Small veins drain blood from the head, neck and arms into vessels that gradually get larger until they reach the SVC. Blood flows into the right side of the heart, then to the blood vessels of the lungs to receive oxygen. From here, blood moves around to the left side of the heart to be pumped out to the body again.

What is the importance of this? If there is not enough blood getting back to the heart from the veins, then there is less to pump back out to the organs. There are also extra channels of veins which drain blood from other parts of the body back to the SVC, which becomes important in SVC syndrome.

Causes of superior vena cava syndrome 

The first diagnosed case of SVC syndrome was in 1757, in a patient with an enlarged aorta due to syphilis.4 Since its first discovery, the trend has shifted toward more cases being associated with cancers.

Cancerous causes - 60-70% of cases3

  1. Lung cancer
  2. Lymphoma 
  3. Metastatic disease (spread from other tumours to the chest or lymph nodes)

Most cases of SVC syndrome are seen in people with lung cancers. Lymphoma is the next most common cause. Many other types of cancer are associated with SVC syndrome but are less common causes.

Non-cancerous causes - 30-40% of cases3

  1. Secondary to implanted medical devices
  2. Benign (non-spreading, non-malignant) tumours 
  3. Infections (e.g., tuberculosis, syphilis) 
  4. Thrombosis (blood clot)  
  5. Other - such as chest radiation therapy, haematoma, bruising, in the chest cavity, enlarged aorta (aortic aneurysm)

In recent years, a higher number of SVC syndrome cases have been associated with medical devices, such as pacemaker wires and central catheters, in keeping with their increased use.1 3 

Why does SVC syndrome cause problems?

The veins in the body are a ‘low pressure’ system and the walls are thin, making them more prone to collapse from external pressure and being damaged by other disease processes.1 5

The most common reason for having SVC syndrome is when a mass within the chest presses on the outside of the SVC.1

Mechanism of SVC obstruction

  • Pressure on the outside of the vessel (most often from cancer pushing on the SVC)
  • Reduced blood flow through the vein (e.g. clots)
  • Damage to the blood vessel wall (damage from cancer invasion or scarring)

Changes in blood flow and pressures

You can imagine the SVC as being one of the two main ‘highways’ for blood moving back to the heart. The other main highway is the previously mentioned IVC. If the highway ‘loses a lane’, or is completely blocked, then you can picture the blood being like ‘traffic’ getting backed up in the vessels.

Once this congestion of blood happens, the symptoms of SVC syndrome begin to develop due to increased pressure in the veins. This usually occurs gradually, anywhere from a few days to a few weeks.1

If blockage occurs quickly, you can imagine the issues for the heart - it now has only one of its ‘main highways’ open to allow blood to reach the lungs and the stronger-pumping left side of the heart. This can cause problems with blood pressure and blood flow to important organs.

Impact on surrounding organs and tissues

Due to the increase in pressure, fluid begins to leak out into the tissues of the areas affected. The head, neck, chest and arms are the main areas involved, and this is the reason why facial, neck, chest and arm swelling can occur.

The pressure changes also affect the veins draining areas that we can’t see externally - such as the brain, airways and throat - which leads to other less common symptoms such as confusion or coma, swallowing difficulty and tightened airways. There needs to be significant and rapid blockage of the SVC to cause these symptoms.3

Signs and symptoms of superior vena cava syndrome

The symptoms of SVC syndrome are variable, and depend on how quickly the blockage of blood flow occurs. SVC syndrome can have no symptoms until the blockage is enough to cause significant increases in venous pressure.

If the blockage occurs quickly, then the symptoms can be more severe. This is because the body needs time to adapt and divert flow through the other vein channels, allowing blood to reach the heart.

If the blockage occurs gradually, the body can adapt to the changes in pressure and the other vein channels can compensate.2

Commonly reported symptoms are:

  • Face swelling
  • Distended neck veins
  • Distended chest veins
  • Shortness of breath
  • Cough

Less common reported symptoms are:

  • Arm swelling
  • Hoarse voice
  • Upper airway tightness/noisy breathing
  • Fainting and headaches
  • Confusion

Diagnosis of superior vena cava syndrome 

Medical history and physical examination

Most cases of SVC are suspected from talking to the patient and examination by a doctor. 

However if obstruction is very gradual or mild, then there may be no obvious signs, or they can be overlooked.6

A combination of symptoms and exam findings are usually enough to suspect SVC syndrome.

Examination can reveal:6

  • More visible veins in the neck and chest wall
  • Face and arm swelling
  • Mental changes (confusion)
  • Facial plethora - redness of the skin in the face
  • Cyanosis - blue-ish skin colour from low oxygen
  • Papilloedema - seen at the back of the eye when pressure in the skull increases
  • Drowsiness or coma in severe cases

The symptoms experienced and signs seen are often worsened when the patient lies flat or bends forward.3 6  

The Pemberton sign is an exam test where the face becomes red from raising the arms overhead for approximately a minute and is associated with SVC syndrome.1 7 However, not having this exam finding won’t exclude SVC syndrome.

Imaging tests8

Diagnosis of SVC syndrome is made with both the patient evaluation and imaging tests.

  • Chest X-ray - can reveal masses in the lung or central chest area, lack of detail is a limitation of this test
  • Ultrasound - may see clots in the veins before the SVC, but won’t see the SVC
  • Computed Tomography (CT) scan - use special contrast to visualise the veins, considered a very useful test
  • Magnetic Resonance Imaging (MRI)
  • Venogram - special test with dye being injected into the vein and pictures taken by x-ray

Biopsy and other diagnostic procedures

If there is a mass seen, diagnosing the underlying cause requires a special sample of tissue, usually from a biopsy. This then goes to a lab to be looked at under a microscope.

This can be done with needles through the skin, and often a lymph node or lung nodule that isn’t too deep can be biopsied. Sometimes, a bone marrow biopsy is used if lymphoma is suspected.

Treatment options1 9

In general treatment is categorised into improving blood flow, treating the underlying cause and symptom relief. 

Improving blood flow through the blockage

  • Placing a stent to open the blocked SVC - especially in emergencies
  • Balloon angioplasty to widen narrowed SVC - inflating a balloon device in the SVC to open it up
  • Surgery to bypass the SVC

Treating the underlying cause

  • Cancer treatment (chemotherapy, radiation therapy, surgery)
  • Anticoagulants - also known as blood thinners - if blood clots are diagnosed

Symptom relief and supportive care

  • Head elevation to reduce pressure
  • Steroids to reduce swelling (e.g. lymphoma)
  • Diuretics - medicine to offload fluid from the body
  • Oxygen therapy if needing breathing support

Complications and prognosis 

Major complications of SVC obstruction can occur if it is unrecognised, untreated, and obstruction is severe.

These include:6

  • Upper airway swelling - which can lead to an inability to breathe
  • Brain swelling - also known as cerebral oedema
  • Pulmonary embolism - if clots move into the vessels of the lungs
  • Reduced heart function and low blood pressure

It is not common for SVC syndrome itself to be life-threatening or cause death.

Prognosis:1,3

If SVC syndrome is from a cancerous cause, then the average life-expectancy is around six months. If beyond this, it is usually less than two years.

If it is non-cancerous and treatment is successful, there is an unchanged life-expectancy in these patients.

When someone presents to hospital acutely, if there are signs of airway or brain swelling, there is a risk of sudden death unless treatment is started quickly.

Summary

SVC syndrome is a collection of symptoms, and not a diagnosis or condition itself. SVC syndrome occurs due to increased vein pressures in the head, neck, chest and arms, because of a partial or complete blockage of the SVC.

Lung cancers are the most common reason for having SVC syndrome. There is an increasing trend for medically inserted devices causing SVC syndrome due to scarring and narrowing of the SVC, and clots.

Treatment is based around improving blood flow and managing the underlying cause.

References:

  1. Seligson MT, Surowiec SM. Superior vena cava syndrome. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Oct 10]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK441981/
  2. White HJ, Soos MP. Anatomy, thorax, superior vena cava. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Oct 10]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK545255/
  3. Azizi AH, Shafi I, Shah N, Rosenfield K, Schainfeld R, Sista A, et al. Superior vena cava syndrome. JACC: Cardiovascular Interventions [Internet]. 2020 Dec [cited 2023 Oct 10];13(24):2896–910. Available from: https://www.jacc.org/doi/10.1016/j.jcin.2020.08.038 
  4. Haider MS, Master MF, Atluri S, Nfonoyim J. Superior vena cava syndrome due to thrombosis: a case report. Cureus [Internet]. [cited 2023 Oct 12];14(5):e24811. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9172051/
  5. Superior vena cava syndrome (Svcs): practice essentials, pathophysiology, etiology. 2023 Jun 14 [cited 2023 Oct 12]; Available from: https://emedicine.medscape.com/article/460865-overview?form=fpf#a5 
  6. Superior vena cava syndrome (Svcs) clinical presentation: history, physical examination, complications [Internet]. [cited 2023 Oct 12]. Available from: https://emedicine.medscape.com/article/460865-clinical?form=fpf#showall
  7. De Filippis EA, Sabet A, Sun MRM, Garber JR. Pemberton’s sign: explained nearly 70 years later. The Journal of Clinical Endocrinology & Metabolism [Internet]. 2014 Jun 1 [cited 2023 Oct 13];99(6):1949–54. Available from: https://academic.oup.com/jcem/article/99/6/1949/2537507 
  8. Superior vena cava syndrome (Svcs) workup: imaging studies, procedures [Internet]. [cited 2023 Oct 13]. Available from: https://emedicine.medscape.com/article/460865-workup#showall 
  9. Patriarcheas V, Grammoustianou M, Ptohis N, Thanou I, Kostis M, Gkiozos I, et al. Malignant superior vena cava syndrome: state of the art. Cureus [Internet]. [cited 2023 Oct 13];14(1):e20924. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8727327/ 

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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