A 42-year-old male suffered from ST elevation myocardial infarction and underwent successful percutaneous coronary intervention (PCI) of the left anterior descending coronary artery (LAD) with drug-eluting stent using intravenous glycoprotein IIB/IIIa inhibitor (Clotinab®, Isu Abxis). Five hours after PCI, the patient developed cold sweating and went into a stupor. Urgent 2D-echocardiography showed a large amount of pericardial effusion and akinesia in the LAD territory. A repeat emergent angiography (CAG) was done to ascertain whether acute stent thrombosis or coronary perforation had occurred after PCI. The CAG showed, however, no leakage of dye or thrombus in any coronary arteries with a patent stent in the middle LAD. Approximately 200 cm3 of bloody pericardial effusion was drained, and his blood pressure returned to normal immediately after pericardiocentesis. Seven days later, he again developed sudden hypotension, bradycardia, and loss of consciousness. The ECG showed ST elevation in V1-V6 and 2D-echocardiography showed scanty pericardial effusion. Emergent CAG showed total occlusion of the LAD due to subacute stent thrombosis. He was successfully treated with balloon angioplasty and was discharged with dual anti-platelet therapy. A follow-up CAG after 9 months showed good flow without residual stenosis across the stented segment.