Abstract 11896: Spontaneous Heparin-Induced Thrombocytopenia Presenting as Acute Stent Thromboses Following an Acute St-Segment Elevation Myocardial Infarction

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Introduction: Spontaneous heparin-induced thrombocytopenia (HIT) is a rare clinical variant that develops without prior exposure to heparin. We present a 40-year-old man who was diagnosed with spontaneous HIT after an acute ST-segment elevation myocardial infarction complicated by multiple acute stent thromboses and left ventricular (LV) thrombus. Case: A 40-year-old previously healthy man with no known history of heparin exposure presented to our emergency department with an acute ST-segment elevation myocardial infarction. Emergent coronary angiography revealed a severely thrombotic 100% occlusion of his distal left anterior descending artery for which thrombectomy and percutaneous coronary intervention (PCI) were performed with placement of a drug eluting stent. Prior to angiography, the patient received 4000 units of unfractionated heparin and an additional 2000 units intra-arterially during the case. Labs prior to PCI revealed thrombocytopenia and HIT enzyme-linked immunoassay testing was sent. He underwent repeat angiography two additional times during his course for recurrent chest pain which both revealed acute stent thrombosis. HIT testing eventually returned positive for the presence of platelet factor 4 antibodies. A subsequent serotonin release assay returned positive, confirming the diagnosis of HIT. A transthoracic echocardiogram during his hospitalization also revealed an LV thrombus. Discussion: Heparin-induced thrombocytopenia (HIT) is traditionally diagnosed after thrombocytopenia develops 5 to 10 days after exposure to heparin. However, there have been rare reports of a spontaneous form of HIT that can occur without prior exposure to heparin. This case highlights a rare presentation of spontaneous HIT. Although infrequent, cardiologists should be aware of atypical presentations of HIT, since almost all patients will receive heparin prior to or during coronary angiography and coronary interventions. Spontaneous HIT should be considered in all patients who present with unexplained thrombocytopenia with arterial and/or venous thrombi. Failure to recognize this clinical entity could lead to potentially life-threatening thrombotic complications from further administration of heparin.