The Sinai Vein Stent Registry aims to establish and maintain a registry of patients who have undergone a vein stent placement procedure at The Mount Sinai Medical Center. The purpose of this study is to monitor and evaluate the long-term outcomes of venous stents placed to treat venous outflow obstruction. Outcome variables that will be assessed are: patency rate, reintervention rate, occurrence of any complications, clinical improvement, and quality of life. Venous outflow obstruction is defined as a stenosis and/or occlusion seen primarily in the ilio-femoral vein and inferior vena cava, and infrequently in the subclavian vein, brachiocephalic vein, or superior vena cava. While vein stent placement procedures are currently being performed in the United States, using stents which are commercially available and FDA-approved for use in arterial interventions, at this time there are no stents that are FDA-approved for use in veins. The placement of stents in veins holds tremendous promise as a treatment for venous outflow obstruction, but review of current literature has showed a paucity of published data on the long-term outcomes of this treatment.

The study is composed of two arms, a retrospective arm and a prospective arm. Any patient over the age of 18 who has undergone or is scheduled to undergo a vein stent placement procedure is eligible for this study. A HIPAA waiver and waiver of informed consent are being requested for the retrospective arm for patients who have undergone a vein stent placement procedure from January 1st 2012 to date of study onset, as it is not possible to contact all patients in the retrospective arm (i.e., lost to follow-up, no longer follows-up with a study physician). This study is only interested in the collection and analysis of data; the clinical care and outcomes of research subjects will not be affected by their participation in this study.

An IDE application has been submitted to the FDA for use of the Wallstent™ (manufactured by Boston Scientific, Inc.) in veins as treatment for venous outflow obstruction. The primary stents being used as treatment for venous outflow obstruction at Mount Sinai is the Wallstent™, mainly due to the fact that only Wallstents™ are available in the appropriate sizes to be used in veins. In rare occasions or exceptional circumstances, a smaller self-expanding nitinol stent may be used. Due to the extremely rare frequency of stents other than Wallstents™ being used and the impracticality (if not impossibility) of obtaining IDEs for all other stents, the investigators believe it is appropriate to exclude usage of these stents from the study data. To confirm, the purpose of this study is to monitor and evaluate long-term outcomes of the venous stents/the vein stent placement procedure, not specifically the Wallstent™ itself.

Inclusion Criteria:

• Patient is 18 years of age or older.
• Patient has undergone or will undergo vein stent placement for proximal venous outflow obstruction in the ilio-femoral vein, inferior vena cava, subclavian vein, brachiocephalic vein, or superior vena cava.

Exclusion Criteria:

• Patient declines participation in the study.
• Confirmed ipsilateral acute DVT of the iliac vein.

Patient has undergone or will undergo vein stent placement for proximal venous outflow obstruction in the ilio-femoral vein, inferior vena cava, subclavian vein, brachiocephalic vein, or superior vena cava.