Comparison of outcomes with different approaches to antithrombotic therapy after venous stenting

Abstract Purpose: Venous obstruction can occur as a result of deep vein thrombosis (DVT), anatomic abnormalities like May-Thurner syndrome, or extrinsic compression. Anticoagulation is the primary treatment for acute DVT, but venous stenting is used in select cases to relieve obstruction and reduce the risk of post-thrombotic syndrome. Optimal antithrombotic strategies following venous stenting remain unclear. While anticoagulants reduce recurrent DVT risk, and antiplatelets are used in arterial stents, objective data for venous stents is lacking, with current practice based on expert consensus (2018 International Delphi Consensus). This retrospective study evaluated in-stent thrombosis and occlusion rates across various antithrombotic regimens after venous stenting. Methods: We conducted a retrospective chart review of patients aged > 18 who underwent venous stenting at UT Southwestern Medical Center (including the academic and safety-net hospitals) between January 1st, 2011 to December 31st, 2021. Exclusion criteria included age <18, stenting of arterio-venous dialysis grafts, or < 2 years of follow up. Patients were categorized into five post-stent antithrombotic treatment groups: antiplatelet (AP) alone, anticoagulant (AC) alone, concomitant AP and AC, sequential AC and AP, or no antithrombotic. Time from stenting to in-stent thrombosis, stent occlusion, or last follow-up was recorded. Major bleeding events were defined as fatal, symptomatic bleeding in a critical area or organ, causing a fall in hemoglobin level of ≥ 2 g/dL, or leading to transfusion of ≥2 units of blood. Cox regression estimated hazard rates with 95% confidence intervals (CIs), adjusting for non-compliance, stent coverage status, and persistent hypercoagulability (e.g., positive serologic testing, malignancy, inflammatory conditions, or unprovoked venous thromboembolism (VTE)). Results: Among 160 included patients, the median age was 49 (IQR 38–60), with 61% (n = 96) females and 39% (n = 62) males. Prior VTE was documented in 85% (n = 135), and a hypercoagulable state was present in 17% (n = 27). Among stents, 9% were covered, 79% were uncovered, and 12% had unknown coverage status. Following venous stent placement, 24% (n = 38) of patients were treated with AC therapy alone, 14% (n = 22) with AP therapy alone, 55% (n = 88) with concomitant AP and AC therapy, 6.3% (n = 10) received no antithrombotic therapy, and 1.3% (n = 2) received sequential therapy. There was no statistically significant difference in event-free survival (EFS) between groups. Univariate Cox regression analysis demonstrated no significant difference in hazard ratios between groups (p = 0.20). Compared to AC alone, HR was 0.53 (95% CI, 0.21–1.38) for AP alone, 1.17 (95% CI, 0.64–2.14) for concomitant therapy, and 0.52 (95% CI, 0.15 – 1.80) for no antithrombotic therapy. Major bleeding events occurred in 17 patients (10.6%) across the study population. There were no bleeding events in the AP alone group (0/22), no antithrombotic group (0/10), or sequential therapy group (0/2), 3 events (7.9%) occurred in the AC alone group, and 12 events (13.6%) occurred in the concomitant AP and AC group. A global comparison of bleeding rates across all five groups using a chi-square test showed a chi-square statistic of 9.44 with 4 degrees of freedom, corresponding to a p-value of 0.051. While not statistically significant, this result indicates a potential trend toward differing bleeding risk among treatment strategies. Conclusions: No randomized controlled trials currently guide antithrombotic management after venous stenting. The 2018 International Delphi consensus generally favored anticoagulation for 6–12 months post-stenting, with discontinuation thereafter for a first VTE but continuation in recurrent VTE. No consensus exists for antiplatelet use. In this retrospective study examining various antithrombotic regimens following venous stenting, we found no statistically significant difference in EFS between treatment strategies. However, the rate of stent occlusion or in-stent thrombosis was numerically higher in the group receiving concomitant therapy, as was the bleeding rate. The study's limited sample size may have reduced the power to detect significant differences, nevertheless, these findings underscore the need for prospective randomized to clarify this issue.