Superior Vena Cava Syndrome
Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD
Introduction
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. If this vein is compressed by outside structures, or if a thrombus
or clot develops within it, then return blood flow to the heart is impeded. When
blood flow to the heart is restricted, the increased pressure in the veins of
the face and arms causes edema (fluid buildup) in these areas. This condition is
referred to as superior vena cava syndrome.
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.
What causes superior vena cava syndrome?
The most common cause of superior vena cava syndrome is cancer. Primary
or metastatic cancer in the upper lobe of the right lung can compress
the superior vena cava.
Lymphoma or other tumors located in the mediastinum can also cause compression
of the superior vena cava.
Less often, the superior vena cava can become blocked with a blood clot from
within. As more invasive medical procedures are being performed on patients, this
cause of superior vena cava syndrome is being seen more frequently. Blood clot
(thrombus) formation that causes superior vena cava syndrome is a
complication of pacemaker wires,
dialysis, and other intravenous
catheters that are threaded into the superior vena cava.
Historically, and in other parts of the world, infection (syphilis and
tuberculosis) is another cause of superior vena cava syndrome. Sarcoidosis (a
disease that results in masses of inflamed tissue) may also cause this syndrome.
Next: What are the symptoms of superior vena cava syndrome? »
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