Superior vena cava syndrome (SVCS) is a group of symptoms that occur when the superior vena cava becomes partially blocked.
The right atrium (chamber) of the heart receives blood from two major veins: the superior (upper) vena cava and the inferior (lower) vena cava.
The superior vena cava is thin-walled, and the blood is under low pressure. If a tumor forms in the chest or nearby lymph nodes become swollen (as from lymphoma), the superior vena cava can be squeezed. Blood flow slows. Complete blockage of the vein can occur. Sometimes, the other veins can become larger and take over for the superior vena cava if it is blocked, but this takes time. Superior vena cava syndrome (SVCS) is the group of symptoms that occur when this vein is partially blocked.
The location of the blocked area and how fast the blockage occurs affect the symptoms.
The symptoms will be more severe if the vein becomes blocked quickly. This is because the other veins do not have time to widen and take over the increased blood flow from the superior vena cava.
The location of the blocked area also affects how severe the symptoms will be: