Cross-sectional echocardiographic diagnosis of large left atrial tumor and extracardiac tumor compressing the left atrium. Limitation of M mode echocardiography in distinguishing the two lesions.

A case of a left atrial fibrosarcoma arising from the posterior left atrial wall and two cases of an extracardiac tumor compressing the left atrium were studied with M mode and cross-sectional echocardiography. In all three cases, M mode echocardiography revealed a mass of echoes just behind the aorta and did not distinguish a left atrial from an extracardiac tumor. By contrast, cross-sectional echocardiography allowed direct visualization of the location, size and movement of the tumor in all three cases and contributed to distinguishing the two lesions. This study indicates that cross-sectional echocardiography is more accurate than M mode echocardiography in the differential diagnosis of a large left atrial tumor and extracardiac tumor compressing the left atrium.