Acute coronary syndrome of the left main coronary artery caused by a huge floating thrombus in the ascending aorta: a case report of intravascular ultrasound effectiveness

BACKGROUND: Left main coronary artery (LMCA)–acute coronary syndrome (ACS) is a rare complication of a floating thrombus in the ascending aorta. However, diagnosing the aetiology of LMCA–ACS during an emergency situation is challenging. We present a rare case of LMCA–ACS caused by a large thrombus in the ascending aorta, confirmed by intravascular ultrasound (IVUS). CASE SUMMARY: A 90-year-old woman presented to the emergency department complaining of chest pain and syncope. On admission, her electrocardiogram showed normal sinus rhythm and a complete right bundle branch block with significant ST depression in the V3–V6 leads; hence, ACS was suspected. The first emergency angiogram of the left coronary artery showed filling defect in the proximal ascending aorta. IVUS revealed a large thrombus in the ascending aorta. The thrombus extended from the ascending aorta to the proximal left anterior descending coronary artery. IVUS confirmed that there was no dissection of the coronary artery or the proximal ascending aorta. Based on the IVUS findings, this case was diagnosed as ACS of the LMCA caused by a floating thrombus in the ascending aorta. DISCUSSION: This rare case of LMCA–ACS caused by a thrombus in the ascending aorta was confirmed by IVUS, which can be a useful imaging tool for diagnosing morphological abnormalities during emergencies.