Subacute coronary stent thrombosis in a patient developing clopidogrel associated thrombotic thrombocytopenic purpura.

Clopidogrel, in combination with aspirin, is commonly used for the prevention of thrombosis in patients who have received coronary artery stents. As a rare but critical complication, clopidogrel associated thrombotic thrombocytopenic purpura (TTP) has previously been described. A 78 year old man presented with unstable angina and filiform subtotal stenosis of the left anterior descending artery. He was treated with balloon angioplasty and stent implantation. After four days the patient again had angina caused by stent thrombosis, which was treated with balloon angioplasty. During hospital stay the typical course of clopidogrel associated TTP was observed with thrombocytopenia and petechial purpura occurring 14 days after drug initiation and prompt response to therapeutic plasma exchanges. These findings strongly suggest that clopidogrel may have increased platelet activation and aggregation in this immunologically susceptible patient, ultimately leading to a stent thrombosis.