Central venous catheter-related thrombosis presenting as SVC syndrome in a hemophiliac with inhibitors

Abstract number: P0138

Carcao M., Connolly B. L., Chait P., Stain A. M., Acebes M., Massicotte P., Blanchette V. S.

Hospital for Sick Children, Canada

Immune tolerance therapy (ITT) in hemophilia A entails the frequent infusions of FVIII often necessitating the need for a central venous catheter (CVC). The combination of a CVC together with frequent infusions of FVIII and possibly periodic infusions of potentially prothrombotic bypassing agents might be highly thrombogenic. Despite this there are few reports of symptomatic thrombosis in such patients. We report a 10.5-year-old boy with severe hemophilia A (intron-22 inversion) and a high titre inhibitor (max. titre 128 BU to human and 192 BU to porcine FVIII) who had been on 2.5 years of ITT with daily rFVIII (100 U kg^-1) and FEIBA (75 U kg^-1) twice a week for bleeding prophylaxis. The boy had a right-sided tunneled CVC (Port-a-cath). He presented with SVC syndrome and with port dysfunction. He was tachypneic and had reduced oxygen saturation (88–92% on room air). Chest X-ray, venography and lineogram revealed a large right sided pleural effusion and a large occlusive thrombus in the SVC with all upper venous system drainage occurring through the azygos and collateral veins. The etiology of the effusion was attributed to increased hydrostatic pressure in the azygos vein leading to poor drainage of lymph fluid through the cisterna chyli. At presentation no inhibitor was detectable by the bethesda assay. We attempted to salvage the port and relieve the SVC obstruction. Despite initial success with local thrombolytic therapy using rTPA the thrombus persisted. Mechanical thrombolysis and angioplasty resulted in the successful removal/dislodgment of the thrombus and resolution of the SVC syndrome and pleural effusion. A 7-day infusion of unfractionated heparin was used to prevent thrombus reformation/propagation. Workup did not reveal any underlying genetic prothrombotic risk factors. The occurrence of such a profoundly symptomatic thrombus in a boy with severe hemophilia A with inhibitors is unusual. A combination of risk factors, including the ongoing infusion of high doses of FVIII in the context of a disappearance of inhibitors together with the infusion of clotting factors known to be potentially thrombogenic, may place hemophiliacs on ITT at risk for this occurrence.