Inverted left atrial appendage mimicking a left atrial mass during mitral valve repair.

This case report describes the appearance of a new homogenous mass seen in the left atrium on intraoperative transesophageal echocardiography after mitral valve repair. This "mass" was the inverted left atrial appendage. Echocardiographers need to recognize normal variants, such as an inverted left atrial appendage, to avoid misdiagnosis.