In-stent Massive Thrombi Formation During Primary Percutaneous Coronary Intervention in a Patient with Acute Myocardial Infarction Complicated with Essential Thrombocythemia.

A 61-year-old man with essential thrombocythemia (ET) presented with acute myocardial infarction (AMI) and underwent primary percutaneous coronary intervention. After stent deployment from the left main (LM) to the left anterior descending artery, intravascular ultrasound revealed thrombi formation in the whole stent. Two days later, optical frequency domain imaging confirmed stent malapposition and thrombi remaining in only the LM. The stent malapposition and ET might have contributed to this phenomenon. He underwent an additional stent expansion and aggressive anti-thrombotic regimen. AMI complicated with ET carries increased risks of in-stent thrombi formation and requires careful revascularization and aggressive pharmacotherapy.