Acute myocardial infarction caused by a floating thrombus in the ascending aorta: A role of CD34-positive endothelial cells.

A 49-year-old woman was transferred to our hospital with acute-onset chest pain. Her electrocardiogram showed complete atrioventricular block and bradycardia with ST-segment elevation in the inferior leads, and she presented with cardiogenic shock. She was diagnosed with inferior acute myocardial infarction (AMI), and subsequent emergency cardiac catheterization was performed. Selective coronary angiography showed neither stenosis nor obstruction in any of the coronary arteries. Left ventriculography showed a large floating object located on the ascending aortic wall above the ostium of the right coronary artery (RCA). Chest enhanced computed tomography confirmed the floating object in the ascending aorta. These findings suggested that the floating object was associated with the RCA occlusion. To remove the floating object, emergency surgery was performed. The floating object was a large thrombus derived from the localized atheromatous plaque in the ascending aorta. Specialized immunostaining for surface antigen CD34 revealed that regenerated endothelial cells were present on the erosion, along the stalk, and on the floating thrombus. These findings indicate that the CD34-positive endothelial precursor cells strayed into the surface and/or inside of the thrombus, and consequently the floating thrombus supported by these regenerated endothelial cells occluded the RCA, causing AMI. <Learning objective: A free floating thrombus formed in the ascending aorta can cause obstruction of the coronary artery ostium, leading to AMI. This unusual cause of AMI mostly occurs in females, and shows high mortality rates. Although the risk factors are known to be current smoking, oral hormone therapy, and hypercoagulable state such as pregnancy, the underlying mechanism of thrombus formation is still unclear. This report describes a possible role of CD-34 positive regenerated endothelial cells in thrombus formation.>.