Partial In-Stent Thrombosis After Iliac Vein Stenting in Non-Thrombotic Vein Lesions

Iliac vein stenting is a safe and efficacious procedure for the correction of iliac vein stenosis. One of its known major complications is complete iliac vein stent thrombosis. However, we have noticed in our practice that a number of patients developed only early partial in-stent (<60%) thrombosis, within the first 30 days. In order to try to learn more about these lesions, we reviewed the data for possible causes of these lesions.From September 2012 to August 2018, we obtained 3518 iliac vein venograms using intravascular ultrasound (IVUS) for patients with venous insufficiency who failed to respond to conservative therapy. Patients were followed up with transcutaneous duplex ultrasound (DUS) every 3 months for the first year and every 6 - 12 months thereafter. Patients were prescribed clopidogrel for 3 months or were told to continue their pre-existing anticoagulants.There were 2234 women and 1284 men who received an iliac vein stent. The mean age was 65.7 ±14 years. Mean follow-up for this cohort was 17 months. Of 74 patients developed a full thrombosis, 38 developed a partial venous thrombosis and 3406 developed no thrombosis. When comparing those who developed a partial thrombus versus those who developed no thrombus/full thrombus, overall age, laterality, CEAP, gender, and whether the patient received clopidogrel prior to the procedure and after the procedure were not found to be statistically significant factors. However, patients with an ASA score of 2 or 3,were found to be at a higher risk of developing a partial thrombus(P = 0.0223) compared to those who had an ASA score of 1 or 4. CEAP Scores and ASA class breakdown can be seen in Table 1 and Table 2, respectively. Of the 38 partial venous thrombosis that developed,18 completely resolved within the first 3 months after the procedure and 20 remained chronic past 3 months after the procedure. Patients with partial venous thrombosis were asymptomatic upon clinical presentation, and none developed post thrombotic syndrome (PTS) or pulmonary embolism (PE). Male gender was associated with partial thrombus resolution(P = 0.0036) CONCLUSIONS: Patients with ASA scores of 2 or 3, seemed to be at a higher risk of developing a partial thrombus when compared to patients with ASA score of 1 or 4. Male gender was associated with partial thrombus resolution. All other factors appear to not be statistically significant in impacting the development of a partial thrombus. This has been the first attempt to look at this new clinical entity.