We report a case involving acute stent thrombosis in a patient with a history of splenectomy and thrombocytosis. The patient arrived with persistent chest pain and vomiting. The electrocardiogram (ECG) revealed ST-segment elevation in leads D2, D3, AVF, and V4-V6. Primary percutaneous coronary intervention was carried out using a 4.0×23 mm drug-eluting stent following loading doses of 300 mg acetylsalicylic acid and 600 mg clopidogrel. Adequate anticoagulation was ensured with intravenous heparin, monitored by activated clotting time (ACT). An ACT of 258 was achieved within 10 min. The procedure was completed successfully, and the patient was admitted to the intensive care unit. However, a follow-up ECG showed persistent ST-segment elevation, and the patient developed cardiogenic shock with complete atrioventricular block. The patient was returned to the catheterization laboratory, where angiography confirmed stent thrombosis. Balloon angioplasty was performed, and tirofiban was administered along with temporary pacing support. The patient was discharged 3 days after the initial procedure with preserved left ventricular function. This case underscores that acute stent thrombosis can occur despite appropriate intervention and anticoagulation. In patients with splenectomy and thrombocytosis, adequate platelet inhibition and anticoagulation may still be insufficient, increasing the risk of stent thrombosis.

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