SPONTANEOUSLY APPEARING MICROBUBBLES ASSOCIATED WITH PROSTHETIC CARDIAC VALVES DETECTED BY TRANSESOPHAGEAL ECHOCARDIOGRAPHY

During transesophageal echocardiographic studies in patients with pros thetic cardiac valves, we have noticed the presence of bright, highly mobile echoes (termed microbubbles because of their similarity to sali ne contrast bubbles) that move rapidly away from the valve. These echo es are distinct from spontaneous echo contrast. The purpose of this st udy was to determine the frequency with which microbubbles are detecte d in association with prosthetic valves. No microbubbles were detected in association with bioprosthetic valves. Thus analysis was limited t o 198 studies performed in 138 patients with left-sided mechanical val ves. Microbubbles were detected in 69 (35%) studies. No differences we re found between studies with and without microbubbles with regard to patient characteristics or the indication for the study. Among the 173 individual valves studied, microbubbles were more frequently detected in association with mitral valves (34 of 82, 41%) versus aortic valve s (14 of 91, 15%; p 0.0001). Microbubbles were more frequently detecte d with disc-type mitral valves (30 of 42, 17%) in comparison to Starr- Edwards mitral valves (4 of 39, 10%; p 0.0001). Microbubbles were more often detected with abnormal valves (28 of 76, 37%) than normal valve s (20 of 97, 21%), p 0.02. We conclude that bright, highly mobile echo es (microbubbles) distinct from spontaneous echo contrast are frequent ly detected during transesophageal echocardiography in association wit h mechanical prosthetic valves. Although the cause and clinical signif icance of these microbubbles are unknown, it is important to distingui sh these echoes from valvular masses such as thrombus or vegetations.