Heparin induced thrombocytopenia in a patient with factor V Leiden following cardiac surgery.

We report a patient who died as a result of heparin induced thrombocytopenia (HIT) and arterial thromboses following cardiac surgery. The onset was three days after exposure to low molecular weight heparin on the eighth postoperative day. The patient was heterozygous for the factor V Leiden mutation. We have reviewed 15 patients previously diagnosed as HIT on clinical and laboratory criteria and found an incidence of 6.7% (1/15) activated protein C resistance. This second patient had a pulmonary embolus and HIT after only three days exposure to low molecular weight heparin. We postulate that factor V Leiden hastens the onset and magnifies the severity of HIT.