Superior vena cava (SVC) syndrome results from any condition that leads to obstruction of blood flow through the SVC. Obstruction can be caused by invasion or external compression of the SVC by adjacent pathologic processes involving the right lung, lymph nodes, and other mediastinal structures, or by thrombosis of blood within the SVC. In some cases, both external compression and thrombosis coexist .
In the preantibiotic era, syphilitic thoracic aortic aneurysms, fibrosing mediastinitis, and other complications of untreated infection were frequent causes of the SVC syndrome. In the postantibiotic era, malignancy became the most common cause, accounting for 90 percent of cases. More recently, the incidence of SVC syndrome due to thrombosis has risen, largely because of increased use of intravascular devices such as catheters and pacemaker wires. In the present era, benign causes now account for 20 to 40 percent of cases of SVC syndrome.
This review will focus on the etiology, clinical presentation, diagnosis, and treatment of SVC syndrome, emphasizing management in patients with malignancy. The management of SVC thrombosis in the setting of hemodialysis and other indwelling intravascular catheters in patients who do not have cancer is addressed elsewhere. (See "Thrombosis associated with chronic hemodialysis vascular access: Catheters" and "Central vein stenosis associated with dialysis access" and "Catheter-induced upper extremity venous thrombosis".)
Obstruction of the SVC can be caused by invasion or external compression by adjacent pathologic processes involving the right lung, lymph nodes, or other mediastinal structures, or by thrombosis of blood within the SVC. As the flow of blood within the SVC becomes obstructed, venous collaterals form, establishing alternative pathways for the return of venous blood to the right atrium (figure 1). Collateral veins may arise from the azygos, internal mammary, lateral thoracic, paraspinous, and esophageal venous systems (image 1).
The venous collaterals dilate over several weeks. As a result, upper body venous pressure is markedly elevated initially but decreases over time. However, even when well-developed collateral drainage patterns are present, central venous pressures remain elevated, producing the characteristic signs and symptoms of SVC syndrome.