Repeated Aortopulmonary Shunt Thrombosis in a Neonatal Patient With a Low Antithrombin Level

Abstract

A female infant with unbalanced right ventricular dominant atrioventricular septal defect with double-outlet right ventricle and pulmonary stenosis had recurrent aortopulmonary shunt thrombosis. She was found to have low antithrombin levels and was managed with antithrombin replacement in addition to unfractionated heparin. A subsequent aortopulmonary shunt was successfully placed, and patency was maintained. Her antithrombin levels normalized, and she was continued on low-molecular-weight heparin and aspirin until four months of age when a bidirectional superior cavopulmonary anastomosis was done. A prothrombotic evaluation at the time of the acute thrombosis and repeated at four months of age was negative except for the initially low antithrombin level. A repeat antithrombin level (off supplementation) at the time of the cavopulmonary anastomosis was normal making the diagnosis of congenital antithrombin deficiency unlikely. This case highlights the possibility of neonatal antithrombin deficiency as a cause of aortopulmonary shunt thrombosis and successful management with replacement therapy.

Thrombosis in the Neonatal Intensive Care Unit

“…77 Antithrombin concentrate has been used to optimize heparin therapy and provide a more consistent state of anticoagulation during extracorporeal membrane oxygenation, cardiopulmonary bypass, and aortopulmonary shunt placement, without increasing the risk for excessive bleeding. 83,[107][108][109][110][111] Anticoagulation dosing in neonates is based on lower levels of antithrombin; therefore, if antithrombin concentrate is administered to achieve anticoagulation and the anticoagulant dose is not adjusted, significant bleeding complications may occur.…”

“…27 There are situations Lower levels of antithrombin in neonates with CHD may predispose aortopulmonary shunt thrombosis. 83 Complications of thrombosis in neonates with CHD include pulmonary embolism, stroke, hemorrhage, and cardiac failure. 84,85 Occurrence of thrombosis after pediatric cardiac surgery has been linked to a 3.4-fold increase in mortality.…”