Spontaneously appearing microbubbles associated with prosthetic cardiac valves detected by transesophageal echocardiography.

During transesophageal echocardiographic studies in patients with prosthetic cardiac valves, we have noticed the presence of bright, highly mobile echoes (termed microbubbles because of their similarity to saline contrast bubbles) that move rapidly away from the valve. These echoes are distinct from spontaneous echo contrast. The purpose of this study was to determine the frequency with which microbubbles are detected in association with prosthetic valves. No microbubbles were detected in association with bioprosthetic valves. Thus analysis was limited to 198 studies performed in 138 patients with left-sided mechanical valves. Microbubbles were detected in 69 (35%) studies. No differences were 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 valves (14 of 91, 15%; p 0.0001). Microbubbles were more frequently detected 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 valves (20 of 97, 21%), p 0.02. We conclude that bright, highly mobile echoes (microbubbles) distinct from spontaneous echo contrast are frequently detected during transesophageal echocardiography in association with mechanical prosthetic valves. Although the cause and clinical significance of these microbubbles are unknown, it is important to distinguish these echoes from valvular masses such as thrombus or vegetations.