[Possible errors in diagnosis of left atrial thrombosis in transesophageal echocardiography]

The detection of thrombi in the left atrium and left atrial appendage by transesophageal echocardiography has significant diagnostic and therapeutic value. However, it requires high method accuracy in routine evaluation. In order to record the percentage of false positive findings, a reevaluation was performed by two experienced examiners using the video recordings of 51 patients, in whom a thrombus has been diagnosed during the routine evaluation. From 1988 to 1994, these thrombi were diagnosed in 726 patients in whom we looked for a source of possible cardiac embolism. In the reevaluation of the 43 cases with sufficient video recordings, in 26 (60%) the diagnosis was classified as false-positive and in 5 patients (12%) as questionable. Thrombus diagnosis was confirmed in only 12 (28%) cases. The incidence of false-positive findings decreased over the course of years with 8.3% (1988-1990), 2.9% (1991-1992) and 0.4% (1993-1994), p = 0.0001. The agreement in the reevaluation between the two examiners was high (interobserver variability 7%), whereby completely divergent evaluations did not occur. Typical diagnostic pitfalls included a prominent trabecular structure in the left atrial appendage (n = 10), the membranous structure between the left atrial appendage and the upper left pulmonary vein (n = 7), transition of the lower left atrium/left atrial appendage (n = 3) and branches within the apex of the left atrial appendage (n = 2). When searching for thrombi in the left atrium and left atrial appendage, there is a high risk of false-positive findings, especially for the unexperienced investigator. Attention must be paid to the typical causes of diagnostic pitfalls in the case of complex and variable anatomy.