Time-Restricted Salutary Effects of Blood Flow Restoration on Venous Thrombosis and Vein Wall Injury in Mouse and Human Subjects.

Background: Up to 50% of patients with proximal deep venous thrombosis (DVT) will develop the post-thrombotic syndrome (PTS) characterized by limb swelling and discomfort, hyperpigmentation, skin ulcers, and impaired quality-of-life. While catheter-based interventions enabling restoration of blood flow (RBF) have demonstrated little benefit on PTS, the impact on the acuity of the thrombus and mechanisms underlying this finding remain obscure. Here in experimental and clinical studies, we examined whether RBF has a restricted time window for improving DVT resolution. Methods: First, experimental stasis DVT was generated in C57/BL6 mice (N=291) by inferior vena cava ligation. To promote RBF, mice underwent mechanical de-ligation with or without intravenous recombinant tissue plasminogen activator (rtPA), administered two days after de-ligation. RBF was assessed over time by ultrasonography and intravital microscopy. Resected thrombosed IVC specimens underwent thrombus and vein wall histological and gene expression assays. Next, in a clinical study, we conducted a post-hoc analysis of the ATTRACT pharmacomechanical catheter-directed thrombolysis (PCDT) trial (NCT00790335) to assess the effects of PCDT on VEINES quality-of-life (VEINES-QoL) and Villalta scores for specific symptom-onset-to-randomization (SOR) timeframes. Results: Mice that developed RBF by day 4, but not later, exhibited reduced day 8 thrombus burden parameters and reduced day 8 vein wall fibrosis and inflammation, compared to controls. In mice without RBF, rtPA administered at day 4, but not later, reduced day 8 thrombus burden and vein wall fibrosis. Notably, in mice already exhibiting RBF by day 4, rtPA administration did not further reduce thrombus burden or vein wall fibrosis. In the ATTRACT trial, patients receiving PCDT in an intermediate SOR timeframe of 4-8 days demonstrated maximal benefits in VEINES-QoL and Villalta scores (between group difference=8.41 and 1.68 respectively, p<0.001 vs. patients not receiving PCDT). PCDT did not improve PTS scores for patients having an SOR time of <4 days or >8 days. Conclusions: Taken together, these data illustrate that within a restricted therapeutic window, RBF improves DVT resolution, and PCDT may improve clinical outcomes. Further studies are warranted to examine the value of time-restricted RBF strategies to reduce PTS in DVT patients.