What is Superior Vena Cava Syndrome?
Superior vena cava (SVC) syndrome refers to changes in your body, such as particular signs and symptoms, which occur due to a blockage of blood flow in a large vein called the superior vena cava. This vein carries blood from your head, neck, upper limbs, and upper body back to the heart. This blockage often happens due to blood clotting or cancer growth in the vein’s wall. Recently, the SVC syndrome tends to appear mainly due to cancer, although its incidence due to non-cancerous causes is also increasing.
What happens when the SVC is blocked? It leads to a condition known as venous congestion, where there’s an abnormal buildup of blood due to the blockage. This increases the pressure in veins in the upper part of the body. The commonly seen signs and symptoms of SVC syndrome include swelling in the face or neck, swelling in the upper extremities, shortness of breath, a frequent cough, as well as visible enlarged veins in the chest.
What Causes Superior Vena Cava Syndrome?
The occurrence of SVC syndrome, a condition that involves blockage of the Superior vena cava (a large vein carrying blood from the body to the heart), has significantly dropped over the last century. That said, much of the SVC syndrome that happens nowadays is due to cancers in the space between the lungs (mediastinal malignancies). The main type of cancer that causes it is small-cell bronchogenic carcinoma, a kind of lung cancer.
The second most common type of cancer behind SVC syndrome is non-Hodgkin’s lymphoma, that is a cancer involving cells of the immune system, followed by cancers that have spread from other parts of the body (metastatic tumors).
It’s also notable that around 40% of SVC syndrome cases currently are due to non-cancerous (benign) or nonmalignant causes. One increasing reason for SVC syndrome is thrombus formation or SVC stenosis (narrowing of the superior vena cava), which can happen because of pacemaker wires and temporary blood vessel catheters. These catheters are tubes inserted into the body to deliver or remove fluids, often necessary for dialysis, long-term antibiotics, or chemotherapy treatments.
Risk Factors and Frequency for Superior Vena Cava Syndrome
Every year in the United States, there are around 15,000 cases of SVC syndrome. This is becoming more frequent because of the increased use of long-term intravascular catheters. The reported occurrence of SVC syndrome can vary from 1 case in every 650 patients to 1 in every 3,100 patients.
Signs and Symptoms of Superior Vena Cava Syndrome
Superior Vena Cava (SVC) syndrome is typically diagnosed based on a patient’s recounted experiences and observed physical symptoms. These symptoms tend to develop gradually over several days or weeks due to blood being rerouted to the lower body, through alternate blood vessels, when the superior vena cava is blocked. This redirected blood flow results in an increase in pressure in the veins in the upper body. Doctors often perform careful physical exams to exclude the possibility that the problems originate from a heart-related issue.
The typical symptoms of SVC syndrome are: swelling of the face and neck, visible bulging neck veins, cough, shortness of breath, discomfort when lying flat, swelling in the upper extremities, visible bulging veins on the chest, and redness in the eyes. Less frequent symptoms can include difficulties in swallowing, fluid build-up in the lungs (pleural effusion), fullness in the face (head plethora), headaches, nausea, feeling faint, fainting, changes in vision, mental changes, swelling in the upper body, blueness in the face or upper body, and in severe cases, leading to a state of unconsciousness or even coma. In very serious cases, SVC syndrome can lead to brain swelling and problems in the upper respiratory tract due to swelling in the voice box and throat.
- Swelling of the face and neck
- Visible bulging neck veins
- Cough
- Shortness of breath
- Discomfort when lying flat
- Swelling in the upper extremities
- Visible bulging veins on the chest
- Redness in the eyes
- Difficulties swallowing (less frequent)
- Fluid build-up in lungs (less frequent)
- Fullness feeling around the head (less frequent)
- Headaches (less frequent)
- Nausea (less frequent)
- Feeling faint (less frequent)
- Fainting (less frequent)
- Vision changes (less frequent)
- Mental changes (less frequent)
- Swelling in upper body (less frequent)
- Blueness in the face or upper body (less frequent)
- In severe cases, unconsciousness or coma (less frequent)
Testing for Superior Vena Cava Syndrome
If your doctor suspects you have Superior Vena Cava (SVC) syndrome – a blockage in the big vein carrying blood to the heart- they will likely order various imaging tests for your upper body. These tests can provide a visual aid in identifying the source and severity of the problem.
One such test is an ultrasound of the jugular, subclavian, and innominate veins. Ultrasound uses sound waves to create a picture of the body’s internal structures and can help the doctor spot a clot in the vein (also known as a thrombus).
Other types of imaging tests include Radiographic imaging and Magnetic Resonance Imaging (MRI). These can offer more detailed information about the location and cause of the Superior Vena Cava obstruction.
A CT (Computed Tomography) scan, which uses a combination of X-rays and computer technology to produce cross-sectional images of the body, has been found to be fairly accurate for diagnosing SVC syndrome. It has a sensitivity rate of 96%, meaning it accurately identifies 96% of cases. Likewise, its specificity rate is 92%, implying that it can correctly rule out SVC syndrome in 92% of cases it is not present.
The gold standard for diagnosing SVC syndrome, however, is venography. Venography is a type of X-ray that takes pictures of blood flow (in this case, within your veins). This method is particularly useful in severe cases and often used alongside an endovascular intervention- a minimally invasive procedure used to treat issues inside the blood vessels.
Treatment Options for Superior Vena Cava Syndrome
After a healthcare professional has diagnosed a patient with “Superior vena cava (SVC) syndrome,” a condition that occurs when the largest vein in the chest is compressed or blocked, they usually start with supportive treatments. One simple technique is to elevate the patient’s head to reduce the pressure on the veins. What happens next depends on what caused the SVC syndrome in the first place.
For patients whose blockage is due to a blood clot associated with a device inserted into their blood vessels — like a pacemaker or an IV — the doctor might suggest removing the device. They could also recommend drugs that help prevent clotting, known as anticoagulants, and a procedure to directly dissolve the clot.
A team of different specialists will plan the treatment for patients who developed SVC syndrome because of a tumor. The kind of tumor and how far it has advanced will guide whether they need chemotherapy or radiation therapy, which are both used to destroy cancer cells.
In the past, an open surgical operation was often used to bypass the obstruction in the SVC. The surgeon would use a part of the saphenous vein (a vein from your leg), the femoral vein (a vein in your groin), or man-made grafts like PTFE or Dacron. But now, surgery is only done when the blockage can’t be removed through a less invasive procedure or when other attempts have been unsuccessful.
Currently, healthcare professionals are more likely to recommend ‘endovascular therapy’ – a procedure that involves inserting a very narrow tube into your veins — as the first approach for treating SVC syndrome. This method can provide immediate relief and is less invasive. If the blockage is due to a clot that is either recent or still not very big, it can be managed with catheter-based thrombolysis (dissolving the clot within the blood vessel) or thrombectomy (a surgical removal of the clot) before the procedure to widen the vessels (‘venoplasty’) and insert a tube to prop it open (‘stent placement’).
What else can Superior Vena Cava Syndrome be?
When a doctor is trying to figure out if a patient has superior vena cava syndrome, they consider several other conditions that might cause similar symptoms. These include:
- Cardiac tamponade (a dangerous build-up of fluid around the heart)
- Mediastinitis (inflammation of the area between the lungs)
- Thoracic aortic aneurysm (a swelling in the large blood vessel that carries blood from the heart to the rest of the body)
- Tuberculosis (a bacterial infection that mainly affects the lungs)
