Adjunctive Catheter-Directed Venous Thrombolysis in Iliofemoral Deep Vein Thrombosis; Short-Term Results from the CaVenT Study, a Multicenter Randomized Controlled Trial
Authors: Enden Tone Rønnaug , Slagsvold Carl-Erik , Kløw Nils-Einar , Sandset Per Morten 
Published: October 2019

Abstract
Conventional treatment of acute deep vein thrombosis (DVT) is anticoagulation and compression therapy (Grade 1A recommendations). Following adequate conventional treatment approximately every fourth patient with proximal DVT of the lower limb develop postthrombotic syndrome (PTS). PTS evolves from persistent venous obstruction and/or venous insufficiency caused by inflammatory destruction of the venous valves. Both obstruction and insufficiency of the veins may lead to venous hypertension. Accelerating the removal of venous thrombus by thrombolytic agents is suggested to prevent the development of PTS. Case-series have shown technical and thrombolytic success, however, the ongoing CaVenT Study is the first randomized, controlled trial to evaluate short- and long-term effects of venous catheter-directed thrombolysis (CDT). Our main hypothesis on short-term effects is that CDT in first-time acute DVT increases patency of the affected iliofemoral vein segments after 6 months from <50% on conventional therapy to >80% after adjunctive CDT. From January 2006 to January 2008 103 patients (64 male, mean age 52.1 years) were randomized to receive either adjunctive CDT (n=50) or conventional treatment alone (n=53). After CDT 50–90% lysis (grade II lysis) was achieved in 20 patients, and complete lysis (grade III) in 24 patients. CDT failed in one patient with agenesis of inferior vena cava, and 1 patient was denied CDT because the thrombus did not reach the upper half of the thigh at initiation of the procedure. Non-invasive assessment of the veins performed at 6 months follow-up, included ultrasound with Doppler and air plethysmography. Patients with incompressibility of the femoral vein, no venous flow and/or functional venous obstruction were classified as not having regained iliofemoral venous patency. Patients with duplicate femoral veins with at least one branch with normal compressibility and flow were considered successfully recanalized. Venous insufficiency was defined as reflux lasting >0.5 sec. Patency of the iliofemoral vein segments was found in 32 (64.0%) patients in the CDT group and 19 (35.8%) in the control group, corresponding to a risk difference (RD) of 28.2% (95% CI, 9.7% to 46.7%, p=0.004). Functional venous obstruction was found in 10 (20.0%) patients in the CDT group and in 26 (49.1%) controls, corresponding to a RD of 29.1% (95% CI, 20.0% to 38.0%, p=0.004). There were no significant differences between the groups regarding the other subcategories of patency (absence of iliofemoral flow and incompressibility of femoral vein), other postthrombotic changes of the iliofemoral veins (wall thickening and echoic content of vein lumen), or femoral venous insufficiency. The results indicate that adjunctive CDT increases patency 6 months after iliofemoral DVT, from 36% to 64%. Venous obstruction, but not venous insufficiency was reduced in the CDT group. The clinical relevance of these findings will be assessed when future data from 2 years follow-up are available. Any future documentation of long-term improved functional outcome, i.e., a reduction in PTS, in this patient group will have a significant impact on clinical practice, and may lead to a modification of existing international guidelines.