What is the pathogenesis of superior vena cava syndrome (SVCS)?

Updated: Mar 26, 2018
  • Author: Todd A Nickloes, DO, FACOS; Chief Editor: Vincent Lopez Rowe, MD  more...
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An obstructed SVC initiates collateral venous return to the heart from the upper half of the body through four principal pathways. The first and most important pathway is the azygous venous system, which includes the azygos vein, the hemiazygos vein, and the connecting intercostal veins. The second pathway is the internal mammary venous system plus tributaries and secondary communications to the superior and inferior epigastric veins. The long thoracic venous system, with its connections to the femoral veins and vertebral veins, provides the third and fourth collateral routes, respectively.

Despite these collateral pathways, venous pressure is almost always elevated in the upper compartment if obstruction of the SVC is present. Venous pressure as high as 200-500 cm H2O has been recorded in patients with severe SVCS.

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