Early Duplex Surveillance Following Deep Venous Stenting for the Treatment of Post- Thrombotic Syndrome can Predict Patients at Greatest Risk for Re-intervention

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Background: Endovascular treatment of post-thrombotic syndrome using nitinol venous stents is associated with symptomatic improvement, but ∼40% require re-intervention. We examined whether ultrasound surveillance was sensitive for re-intervention, and whether it was possible to predict patients at greatest risk of re-intervention. Methods: Stent patency was assessed between 2012–2017 using duplex ultrasonography 24hrs, 2wks, 6wks, 3mths, 6mths, 1yr and yearly post-intervention. Maximum in-stent stenosis was calculated, with re-interventions performed when stent diameter reduction was >50%. Patient demographics were collected to determine which factors were associated with re- intervention. Results: Cumulative patency was 167/194 (86%). 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 surveillance in 70/79 (87%) cases, and this was driven by scan results rather than symptom change. 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, maximum in- stent stenosis between 30-50% at 6wks was associated with a higher risk of re-intervention at 6mths (HR 29.90; p=0.002, 95% CI [3.519–253.989]). Conclusions: Ultrasound surveillance should occur at frequent intervals up to 3wks post deep venous stenting. 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.