The GORE® VIABAHN® FORTEGRA Venous Stent IVC Study

Preoperative Inclusion Criteria: * Patient is at least 18 years of age. * Patient is willing and able to comply with all follow-up evaluations as well as any required medication or compression regimen. * Patient is able to provide informed consent. * One of the following: Clinical severity class of CEAP 'C' classification ≥3 or rVCSS pain score ≥2. * Intention to treat the target areas with only the GORE® VIAFORT Vascular Stent. * Estimated life expectancy ≥1 year. * Patient is ambulatory (use of assistive walking device such as a cane or walker is acceptable). * Patient has adequate inflow to the target lesion(s), per investigator/sub-investigator discretion, involving at least a patent femoral or deep femoral vein. Preoperative Exclusion Criteria: * Patient is a pregnant or breastfeeding woman, a woman planning to become pregnant through the 12-month visit, or a woman who is unwilling to practice an acceptable method of preventing pregnancy through the 12-month visit. * Patient has clinically significant (e.g., symptoms of chest pain, hemoptysis, dyspnea, hypoxia, etc.) pulmonary embolism (confirmed via Computed Tomography Angiography) at the time of enrollment. * Patient has a known uncorrectable bleeding diathesis or active coagulopathy meeting the following definitions: uncorrected INR\>2 (not as a result of warfarin or DOAC therapy), OR platelet count \<50,000 or \>1,000,000 cells/mm3, OR white blood cell count \<3,000 or \>12,500 cells/mm3. * Patient has impaired renal function (eGFR \<30 mL/min/1.73m2) or is currently on dialysis. * Patient has uncorrected hemoglobin of \<9 g/dL. * Patient has known history of antiphospholipid syndrome (APS) or patients with hypercoagulable states that are unwilling to take anticoagulant medications on a long-term basis. * Patient has known homozygous inherited coagulation defect or Protein C/S deficiency. * Patient has a planned surgical intervention (other than pre-stenting procedures such as thrombolysis or thrombectomy) within 30 days prior to or within 30 days after the planned study procedure. * Patient is currently participating in another investigational drug or device study that has not completed the primary endpoint or that clinically interferes with the endpoints of this treatment, in the opinion of the investigator/sub-investigator. Observational studies are permitted. * Patient has had a previous major (i.e., above the ankle) amputation of the target lower limb. * Patient has known sensitivity to device materials or contraindication to antiplatelets, thrombolytics, anticoagulants (including patients with known prior instances of Heparin Induced Thrombocytopenia type 2 (HIT-2)), or iodinated contrast. * Patient has had prior stenting or grafts in the target vessels. * Patient has a known or suspected active systemic infection at the time of the index procedure. Patients with a chronic infection (e.g., HIV, hepatitis C) that is well controlled under their current treatment regimen may be eligible. * Patient has known history of intravenous drug abuse within one year of treatment. * Patient has significant peripheral arterial disease (chronic Rutherford Type 2 or greater, acute Rutherford Type IIa or greater). * Patient has a BMI \>40. * Patient is actively undergoing or plans to begin cancer treatment. Intraoperative Inclusion Criteria: * Presence of non-malignant obstruction of the inferior vena cava defined as occlusion or at least 50% reduction in target vessel lumen as measured by procedural IVUS and venogram, with or without non-malignant obstruction of the common femoral vein, external iliac vein, and/or common iliac vein. * Patient can accommodate an appropriately sized GORE® VIAFORT Vascular Stent as per reference vessel diameter (see IFU), as determined by intraoperative IVUS post pre-dilation. * Patient must have appropriate access vessels to accommodate the delivery sheath for the selected device size. * Patient has adequate landing zones free from significant disease requiring treatment within the native vessels beyond the proximal and distal margins of the lesion. * Patient has adequate inflow to the target lesion(s), per investigator/sub-investigator discretion, involving at least a patent femoral or deep femoral vein. * Lesion can be traversed with a guidewire. * Disease involves the inferior vena cava and may include iliofemoral segments with intent to stent all affected iliofemoral and caval segments. * Patient does not have significant (i.e., \>20% residual thrombosis) acute thrombus within the target stent area at the time of investigational device placement. Patients with acute thrombus within the target stent area must have thrombus successfully treated prior to investigational device placement. Successful thrombus treatment is defined as reestablishment of antegrade flow with ≤20% residual thrombosis as confirmed by IVUS and venogram, AND freedom from bleeding, vascular injury, or hemodynamically significant pulmonary embolism. After successful thrombus treatment, investigational device placement can occur within the same procedure. * Patient does not have an inferior vena cava filter present within the target stent area at the time of investigational device placement. Patients with an inferior vena cava filter present within the target stent area must have the filter successfully removed prior to investigational device placement. Successful removal is defined as removal of the main body of the filter and intra-luminal fragments such that there is minimal risk to luminal integrity per investigator/sub-investigator discretion AND freedom from bleeding, vascular injury, or hemodynamically significant pulmonary embolism. After successful filter removal, investigational device placement can occur within the same procedure.