Two-dimensional echocardiographic study was performed to detect left atrial thrombi in 33 patients with a prosthetic mitral valve. The subjects were 9 males and 24 females and their ages ranged from ...21 to 61 years (average 43.2 years). Their prosthetic valves consisted of 18 Hancock, three Carpentier-Edwards, four Björk-Shiley, four Starr-Edwards and four St. Jude Medical valves. Two-dimensional echocardiograms were obtained using a Toshiba SSH-11A echograph with an electronic phased-array scanner. The left parasternal, apical, subcostal and right parasternal windows were used to detect left atrial thrombi. In five of the 33 patients, a left atrial thrombus was demonstrated as a mass echo attached to the posterior wall of the left atrium. The clinical and echographic features of five patients with a left atrial thrombus (Group A) were compared to those of 28 patients without it (Group B). The average age at the time of operation was 44.6 +/- 9.7 years in Group A and 43.0 +/- 9.5 years in Group B, showing no difference between the two groups. In 10 of the 33 patients, a left atrial thrombus was confirmed by the initial operation. In only one of these 10 patients, a left atrial thrombus was demonstrated by post-operative two-dimensional echocardiographic examination. The presence or absence of a left atrial thrombus in the pre-operative stage did not clearly relate to the occurrence of a left atrial thrombus in the post-operative stage. The cardio-thoracic ratio was significantly greater (p less than 0.01) in Group A (74.4 +/- 6.3%) than in Group B (58.1 +/- 8.1%). Left atrial dimension by M-mode echocardiograms was significantly greater (p less than 0.05) in Group A (70.6 +/- 11.3 mm) than in Group B (51.6 +/- 7.7 mm). The length of the pseudo-septalized left ventricular posterior wall was longer (p less than 0.05) in Group A (34.0 +/- 11.5 mm) than in Group B (12.8 +/- 9.4 mm). The angle between the perpendicular to the mitral annulus and the upper part of the interventricular septum was significantly greater (p less than 0.01) in Group A (58.6 +/- 18.0 degrees) than in Group B (18.8 +/- 9.6 degrees). The characteristics observed in Group A were thought to be caused mainly by the giant left atrium. Therefore it is concluded that there is a close relationship between left atrial thrombi and the giant left atrium in patients with a mitral prosthetic valve.
