Definition
Superior vena cava syndrome (SVCS) develops from obstruction of venous drainage from the upper body, resulting in increased venous pressure, which leads to dilation of the collateral circulation. The superior vena cava is a large vein located in the upper chest, which collects blood from the head and arms and delivers it back to the right atrium of the heart. Because the superior vena cava, like all veins, has a thin wall (there are no muscles in the walls of a vein as compared to the walls of an artery), and because there is little pressure inside the vein, it can be easily compressed by outside structures. The superior vena cava lies next to the upper lobe of the right lung and within the mediastinum [the space that contains the central structures of the chest: the heart, the trachea, the esophagus and the great vessels (aorta, vena cava)]. Abnormalities within any of these structures can cause the compression.
Pathophysiology
The SVC is part of the low-pressure venous system containing thin walls susceptible to damage by a variety of pathologic mechanisms. These mechanisms can be divided into three categories which are compromised vessel anatomy, impaired venous flow, and diminished vessel wall integrity. These mechanisms often coexist in patients presenting with SVC syndrome. Extrinsic compression and obstruction of the SVC by a mass in the mediastinum is the most common cause of SVC syndrome. This is often associated with malignancy; however, there are a variety of nonmalignant masses as well as dilation of the overlying aorta that can cause compression. A growing proportion of SVC syndromes are now associated with occlusive venous thrombus formation that compromises venous flow back to the heart. The increasing use of indwelling intravascular devices such as catheters and pacemakers and implantable cardioverter-defibrillator (ICD) leads have played a major role in this growth. Resultant venous wall inflammation, fibrosis, and eventual thrombus lead to stenosis of the vessel itself.
Epidemiology
According to studies, there are an estimated 15,000 cases of SVC syndrome each year in the United States, and this number is likely to increase as more semipermanent intravascular catheters are used. The literature reports an incidence of SVC syndrome of 1 in 650 to 1 in 3100 individuals.
Causes of Superior Vena Cava Syndrome
SVCS is more common if you have lung cancer, non-Hodgkin lymphoma, or cancer that spreads to the chest. Cancer can cause SVCS in several ways:
- A tumor in the chest can press on the superior vena cava.
- A tumor can grow into the superior vena cava and block it.
- Cancer can spread to the lymph nodes around the superior vena cava. The lymph nodes can get larger and press on or block the vein.
- Cancer can cause a blood clot in the vein. A pacemaker wire or a catheter in the vein could also cause a clot. A catheter is a flexible tube that lets your health care team give you fluids or take them out.
Causes of SVCS
Superior Vena Cava Syndrome Symptoms
Signs of superior vena cava syndrome usually develop slowly. But they can worsen quickly and turn into a medical emergency, especially in children. It’s essential to contact your healthcare provider if you or your child develops symptoms.
The most common superior vena cava syndrome symptoms include:
- Cough
- Face or neck swelling.
- Feeling of fullness in your upper body.
- Swelling in your arms and hands.
- Shortness of breath (dyspnea).
Other signs sometimes include:
- Blueish skin (cyanosis).
- Chest pain.
- Coughing up blood.
- Faster breathing.
- Hoarse voice or difficulty speaking.
- Horner’s syndrome, symptoms on one side of your face (sagging eyelid, lack of sweat, one smaller pupil).
- Trouble swallowing.
- Visibly swollen veins in your upper body.
Risk factors
Common risk factors in the development of superior vena cava syndrome are:
- Lymph node metastasis
- Non–small cell lung cancer
- Small cell lung cancer
- Lymphoma
- Metastatic lesions (most commonly from breast and testicular cancers)
- Infections
- Thyroid goiter
- Iatrogenic intravascular devices
- Pericardial constriction
- Idiopathic sclerosing mediastinitis
- Aortic aneurysm
Complications of Superior Vena Cava Syndrome
When blood doesn’t return effectively to the heart, your body tries to solve the problem by creating more veins. This is known as developing collateral circulation. They are like an alternate route from the superior vena cava to try to get blood back to the heart.
Even with collateral circulation, you can still experience symptoms, such as:
- Swelling, most worrisome in the brain and larynx (which affects breathing)
- Cough
- Nausea
- Problems swallowing
- Shortness of breath
- Upper arm swelling
If SVCS isn’t treated effectively, then ultimately it can lead to an inability to breathe, which can be fatal. SVCS is most commonly associated with cancers that occur in the chest area, but it has also been associated with syphilis and tuberculosis.
Diagnosis
If a doctor suspects a person has superior vena cava syndrome, they will first do a physical exam. The exam may show enlarged veins in the upper body.
If the physical exam suggests superior vena cava syndrome, a doctor will likely order several additional tests, including:
- A chest X-ray to check for tumors in the lungs or an enlargement in the chest
- A CT scan to show blockages
- Venography, which is an X-ray of the veins after an injection of a special dye that makes the veins visible
- An ultrasound to look for blood clots in the upper extremities
If a tumor is found to be responsible for the blockage, a doctor may order a biopsy to determine what type of tumor is causing the problem. Knowing whether the tumor is cancerous or benign is essential for receiving proper treatment.
Treatment for Superior Vena Cava Syndrome
Treatment of SVCS depends on the cause of the blockage, the seriousness of the symptoms, and the person’s overall health and preferences.
If there’s a blood clot in the SVC that’s linked to an implanted medical device, medicines will be used to dissolve the clot and the device might be taken out.
If there’s no clear cause based on the person’s medical history, tests will be done to look for the cause. For instance, if scans show a tumor in the chest that’s pressing on the SVC and lung cancer is suspected, a sputum test and a biopsy might be done. The results can then help the healthcare provider decide on the best treatment.
Treatment shouldn’t start until the healthcare provider finds the cause of the blockage. The treatments covered here focus on SVC blockage caused by cancer. Since the treatment of the blockage may depend on the type of cancer, the cancer diagnosis should be made before treatment is started. Unless the airway is blocked, the brain is swelling, or other symptoms are causing problems, waiting to start treatment is usually not a problem.
The following treatments can be used for cancer-related SVCS:
Radiation therapy
If the blockage of the SVC is caused by a tumor that doesn’t respond or is slow to respond to chemotherapy (such as non-small cell lung cancer), radiation therapy may be given. It can quickly shrink tumors and ease symptoms.
Chemotherapy
This is the treatment of choice for chemo-sensitive tumors, such as lymphoma or small cell lung cancer. Many times, SVCS doesn’t change the treatment plan. Treating the cancer helps clear up the SVCS.
Thrombolysis (breaking up blood clots)
SVCS may happen when a blood clot (thrombus) forms in a partly blocked vein. People who have blood clots may need thrombolysis. This treatment uses medicine to dissolve or remove the blood clot.
Stent placement
A stent may be used to open up the blocked vein. This can quickly ease SVCS symptoms. A stent is a small metal or plastic tube that’s put into the blocked part of the vein to allow blood to pass through. Some people may also need a blood-thinning medicine (anticoagulant) to help keep more blood clots from forming and blocking the stent.
Medicines to ease symptoms
Sometimes other medicines can be used to ease symptoms while tests are done to look for the cause of SVCS. Steroids can help reduce swelling and inflammation. Water pills (diuretic medicine) can help you pass more urine to get rid of extra fluid in your body.
Prevention
The most important primary prevention measure is to avoid smoking, which increases the risk of malignant causes of SVC syndrome.