Systemic Thrombolytic Resistance in Antithrombin III Deficiency Rescued by Catheter-Directed Thrombolysis: A Case...

Hereditary antithrombin III (AT III) deficiency is a rare thrombophilic disorder that may cause resistance to systemic thrombolytic therapy. We report a case of massive iliofemoral deep-vein thrombosis (DVT) with high-risk pulmonary thromboembolism (PTE) refractory to systemic thrombolysis, successfully treated with catheter-directed thrombolysis (CDT).

A previously healthy 33-year-old man presented with dyspnoea and left-leg swelling. Imaging revealed bilateral pulmonary-artery thrombi with acute right-ventricular failure and extensive iliofemoral DVT. Despite systemic alteplase infusion, thrombus resolution was incomplete, and hereditary AT III deficiency (53% activity) was diagnosed. CDT via the right femoral vein was performed using alteplase (0.02 mg/kg/h for 48 h), achieving near-complete thrombus resolution and restoration of venous flow without bleeding complications.

This case highlights systemic thrombolysis failure associated with AT III deficiency and demonstrates that CDT can serve as an effective, low-bleeding-risk rescue therapy for extensive DVT when systemic treatment is inadequate. These findings underscore the importance of early recognition of AT III deficiency and consideration of catheter-based intervention in similar high-risk settings.