Timing is Everything: Importance of Early Duplex Surveillance in Predicting Risk of Re-intervention Following Deep Venous Stenting for the Treatment of Postthrombotic Syndrome

Introduction - Endovascular treatment of post-thrombotic syndrome using nitinol venous stents is associated with symptomatic improvement, but ∼40% will require re-intervention. Our approach to maintain stent patency has been through close surveillance to intervene before stent occlusion. There is, however, limited data on the efficacy, interval and duration of ultrasound surveillance following deep venous reconstruction. The aim of this study was to examine whether ultrasound surveillance was sensitive for re-intervention, and to investigate whether it was possible to predict which patients had the greatest risk of re-intervention. Methods - Consecutive patients in whom a venous stent was inserted for symptomatic occlusive post-thrombotic disease between 2012 and 2017 were included for analysis. Stent patency was assessed using duplex ultrasonography 24hrs, 2wks, 6wks, 3mths, 6mths,1yr and yearly post intervention. The maximum in-stent stenosis was calculated, with re-interventions performed when there was a stent diameter reduction of >50%. Patient demographics were collected to determine which factors were associated with re-intervention. Results - Of 194 patients treated in our venous programme during the study period, cumulative patency was 86% (median follow-up 2.4yrs; range 34-295wks). However, 79 (41%) patients required re-intervention to maintain patency, of which 40/79 (51%) occurred within 3wks of their procedure. Stenting across the inguinal ligament was associated with a higher risk of early re-intervention (HR 1.817; P=0.048, 95% CI [1.005, 3.285]). Re-interventions immediately followed ultrasound surveillance in 70/79 (87%) cases, and this was driven by scan results rather than symptom change. From this group, 13/79 (17%) required only a single re-intervention, while 16/79 (20%) required more than 3 re-interventions (median number of re-interventions 2; range 1-6). At 6wks, maximum in-stent stenosis <30% was a strong predictor of being low risk for re-intervention at 6mths (HR 0.038; P=0.003, 95% CI [0.004, 0.322]). Conversely, patients with a maximum in-stent stenosis between 30-50% at 6wks were at high risk of requiring re-intervention at 6mths (HR 29.90; p=0.002, 95% CI [3.519, 253.989]). Furthermore, the anatomical location of the maximum in-stent stenosis was not a contributing factor for re-intervention. Conclusion - Ultrasound surveillance is an important component of deep venous stenting, and should occur at frequent intervals up to 3wks post procedure. Ultrasound surveillance at 6wks could be used to differentiate between patients that require further surveillance before 6mths. These may include patients with maximum in-stent stenosis between 30-50% at 6wks and patients with stents crossing the inguinal ligament.