Novelty: This is one of the first Indian studies addressing this research question and using a randomized controlled design (only one other study done so far). Data from multiple centers will increase external validity and use of point of care compression ultrasound (PoCUS) to ascertain residual venous thrombosis will enhance feasibility. 

Objectives: Primary objective is to determine efficacy of a flexible duration of extended anticoagulation based on repeat ultrasound for residual vein thrombosis compared to fixed duration of extended anticoagulation in reducing recurrent thrombotic events among patients with symptomatic deep vein thrombosis who have completed 3 months of anticoagulation. Secondary objective is to determine diagnostic accuracy of point of care compression ultrasound (PoCUS) compared to formal venous study for detection of residual venous thrombosis. 

Methods: This will be a randomized, parallel arm, multicenter study at 3 major hospitals treating venous thromboembolism. Consecutive patients diagnosed with first episode of VTE will be randomized to either a fixed duration anticoagulation or an ultrasound-guided duration based on detection of residual venous thrombosis. Both groups will be followed up for 30 months for primary objective of recurrent VTE. Secondary outcomes will be adverse events and duration of anticoagulation. 

Expected outcome: Results will enable making data driven, evidence-based changes to existing recommendation that is largely based on observational studies. Further it will establish diagnostic value of Point of care Ultrasound Scan (PoCUS) to rapidly detect residual venous occlusion among patients on anticoagulation for VTE.