Antithrombin deficiency--a cause of unexplained thrombosis in vascular surgery.

Antithrombin deficiencies may be the reason for seemingly unexplained thrombosis and graft failure. We treated seven patients who developed clotting difficulties as a result of antithrombin II and/or III deficiencies. In four, arterial thrombosis occurred after arterial reconstruction--three with occluded femoral grafts and one with runoff and digital vessel thrombosis that developed during profundoplasty. Two patients has spontaneous thrombosis of the arterial system of the vessels of the lower leg, and one developed ileofemoral phlebitis. Three patients had abnormally low levels of both antithrombin II and III, whereas two had low levels of antithrombin II only and two had low levels of antithrombin III. Of the four patients in whom this disorder occurred during vascular reconstruction, three experienced graft occlusion that resulted in below-knee amputation in two. There were no common predisposing factors. Antithrombin deficiency should be suspected when there is an unusual propensity to develop thrombus, when heparin cannot prolong coagulation time, and when measurements show reduced levels of antithrombin. Fresh frozen plasma should be given initially and long-term Coumadin therapy started. Early recognition and treatment is necessary to avoid limb loss or death.