Mechanisms of Occlusion

Understanding the nature of occlusion in SVC syndrome helps define the etiology of obstruction and guides your therapeutic plans. There are four mechanisms by which the SVC can be occluded:

Compression:

SVC syndrome can be compressed by SPCE occupying lesions, either malignant or benign. Long standing and partial obstruction is often produced by sub-sternal thyroid by external compression.

Invasion:

Malignant tumors often invade the SVC and occlude the lumen.

Thrombosis:

Hypercoagulable states (malignancy and polycythemia), intimal damage (various lines) and stasis (external compression) contribute towards the development of SVC thrombosis. Fibrinolytic therapy or anticoagulation are to be considered if this is the cause for SVC obstruction.

Constriction:

Dense scar tissue can encircle the SVC and constrict the vein in patients with mediastinal fibrosis.

Angiography will be required to determine which one of these mechanisms is responsible for SVC obstruction. A proper understanding of this concept will enable you to investigate the etiology and select a therapeutic modality on a rational basis.