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Transcranial high-intensity Doppler signals in patients with mechanical heart valve prostheses: their relationship with abnormal intracavitary echoes.

BACKGROUND AND AIMS OF THE STUDY
In preceding studies, we reported that abnormal Doppler signals of high intensity (HITS) were frequently found in the cerebral arteries of patients with prosthetic mechanical heart valves. These signals should be attributed either to air microbubbles, possibly due to cavitations or to solid emboli elements. On the other hand, the presence of abnormal intracardiac echoes has been reported in patients with mechanical valves. These echoes should be also attributed to air microbubbles or to formed elements. Although in vitro experiments are in favor of the first explanation, the discussion of their origin remains open.


METHODS
Among patients subjected to a transesophageal echocardiography (TEE), we selected subjects with mechanical prosthetic heart valves, according to the following criteria: (i) normally functioning valves; (ii) bright echoes suggesting microbubbles, inside the prosthetic valve and/or upstream from it (left ventricular outflow tract or left atrium); (iii) no morphological lesions that could generate solid microemboli at the prosthetic level; (iv) normal carotid arteries, as investigated by color echo-Doppler.


RESULTS
Twenty patients were selected: 11 men and nine women of age range 40-64 years. They were implanted with mechanical heart valves (24 Saint-Jude Medical, three Björk-Shiley and one CarboMedics) in the mitral position (10), aortic position (two), or mitral and aortic position (eight) for periods ranging from 10 days to 17 years. There was no major left ventricular dysfunction (mean end-diastolic diameter 51.8 mm; mean ejection fraction 59%). The mean diameter of the left atrium was 46.1 mm. All but three patients were in sinus rhythm; seven had presented with a transient ischemic attack or amaurosis within the six months preceding the investigation. Immediately after TEE, Doppler signals were recorded on the middle cerebral arteries (MCA) during 10 minutes on each side, and the abnormal Doppler signals were counted. Seventeen subjects (85%) exhibited HITS repetition rate from 0.2 to 5.5 per min.


CONCLUSION
The percentage of patients with HITS in a non-selected group with mechanical heart valves was about 50%, as observed in previous studies. It appears that in a selected group of patients the percentage with HITS is consistently higher. Therefore, HITS and abnormal intracardiac echoes could have a common origin.