Prevalence of microbubbles associated with mechanical prosthetic cardiac valves: a prospective transesophageal...

The study aim was to identify the prevalence of microbubbles in different types of mechanical cardiac valve and, if feasible, to associate microbubbles with various clinical conditions, including thrombotic occlusion of the valves.

A total of 153 mechanical prosthetic valves were studied (58 aortic, 95 mitral) in 140 patients, prospectively. All valves were functioning normally. In addition, eight mitral prosthetic valves were selected without microbubbles and with an obstructive valvular thrombosis that had undergone successful thrombolysis (group 1); a further eight patients with unsuccessful thrombolysis (group 2) were studied by transesophageal echocardiography before and after thrombolytic therapy.

Microbubbles were detected in 75% (114/153) of prosthetic valves, 99% (88/89) of bileaflet valves, and 45% (29/64) of monoleaflet valves (p < 0.0001). Only 14% (4/28) of Sorin monoleaflet valves were associated with microbubbles, which is distinctively less than other valves (p < 0.001 for each); 71% and 77% of aortic and mitral prosthetic valves, respectively, were associated with microbubbles (p = NS). Prosthetic valves with an obstructive thrombosis and no microbubbles in group 1 showed new appearance of microbubbles in 88% (7/8) of cases after successful thrombolysis. Absence of microbubbles in group 2 persisted in all eight patients at the second examination.

Microbubbles were detected in a greater proportion of patients than reported previously and were found to be associated more with bileaflet prosthetic heart valves than with monoleaflet valves. Sorin monoleaflet valves were associated with microbubbles dramatically less than all other valves. The new appearance of microbubbles after thrombolytic therapy of mechanical prosthetic heart valves with an obstructive thrombosis may indicate successful thrombolysis.