• left atrial mass;
  • left atrial myxoma;
  • left atrial appendage thrombus;
  • cardiac magnetic resonance imaging;
  • neovascularization;
  • coronary arteriography

The preoperative differentiation of a thrombus from a myxoma is important but not always easy. Clinical and echocardiographic characteristics of myxoma and thrombi are not diverse enough to always reliably distinguish the two. We report the case of a patient who was found to have a left atrial appendage thrombus that was misdiagnosed as a myxoma on the basis of its imaging characteristics on cardiac magnetic resonance in addition to the detection of dense neovascularization on coronary angiography. This case highlights the unusual features of an organized thrombus that can mimic many of the distinguishing characteristics of a myxoma. (Echocardiography 2010;27:E98-E101)