Patency and reflux in relation to post-thrombotic syndrome: a subanalysis of the Ultrasound-Accelerated Catheter-Directed Thrombolysis Versus Anticoagulation for the Prevention of Post-Thrombotic Syndrome trial

Background: Adjunctive catheter-directed thrombolysis shows variable efficacy in preventing postthrombotic syndrome (PTS), despite restored patency. Objectives: This Ultrasound-Accelerated Catheter-Directed Thrombolysis Versus Anticoagulation for the Prevention of Post-Thrombotic Syndrome (CAVA) trial subanalysis investigated the effect of ultrasound-accelerated catheter-directed thrombolysis (UACDT) on patency, reflux, and their relevance in PTS development. Methods: This multicenter, randomized, single-blind trial enrolled patients (aged 18-85 years) with a first iliofemoral deep vein thrombosis and symptom duration ≤14 days. Patency and reflux were assessed by duplex ultrasound at 12 months (T12) and long-term (LT) follow-up (median, 39.5 months; IQR, 24.0-63.0 months). PTS was diagnosed using the Villalta score. Results: UACDT significantly improved patency in all vein segments at T12 (60.3% UACDT vs 25.9% standard treatment [ST]; P = .002) and LT (45.2% UACDT vs 11.9% ST; P < .001). Popliteal patency, however, was similar between groups (87.9% UACDT vs 83.3% ST; P = .487). Reflux was similar between groups at T12 and LT; only popliteal reflux was significantly reduced in the UACDT group at LT (22.6% UACDT vs 44.8% ST; P = .010). Absent iliac patency at T12 was associated with increased PTS risk in the ST group only (odds ratio [OR], 10.84; 95% CI, 1.93-60.78; P = .007). In the UACDT group, popliteal reflux at T12 was associated with moderate-to-severe PTS at T12 (OR, 4.88; 95% CI, 1.10-21.57; P = .041) and LT (OR, 5.83; 95% CI, 1.44-23.63; P = .009). Combined popliteal reflux and absent iliac patency significantly amplified PTS risk (OR, 10.79; 95% CI, 2.41-48.42; P < .001). Conclusion: UACDT improved patency and reduced popliteal reflux. Iliac patency and popliteal reflux are independently associated with moderate-to-severe PTS and contribute synergistically to its development. However, a proportion of moderate-to-severe PTS cases lacks an evident underlying cause.