Thrombotic occlusion of Blalock-Taussig shunt in a patient with unnoticed protein C deficiency.

A 6-month-old girl with a diagnosis of double-outlet right ventricle and pulmonary stenosis had a left modified Blalock-Taussig shunt. Chest computed tomography (CT) performed on postoperative day 11 showed good patency of the shunt. However, on postoperative day 16, oxygen saturation suddenly dropped below 40%, and chest CT showed thrombotic occlusion of the shunt. Urgent thrombectomy was performed successfully. Examination of coagulation factors revealed low levels of both the amount and activity of protein C (27% and 31%, respectively). Diagnosis of heterozygous hereditary protein C deficiency was made, and the patient was placed on warfarin. She is currently in good condition.