Hr. Muller et al., SIMULTANEOUS BILATERAL TRANSCRANIAL DOPPLER SONOGRAPHY FOR THE DETECTION OF MIDDLE CEREBRAL-ARTERY MICROEMBOLI FROM MECHANICAL PROSTHETIC HEART-VALVES, Cerebrovascular diseases, 4(6), 1994, pp. 393-397
Simultaneous bilateral transcranial Doppler emboli monitoring was carr
ied out in 20 patients having mechanical heart valve prostheses (aorti
c, n = 7, and/or mitral, n = 13) for up to 23 (mean 8 +/- 7) years. Du
ring a 10-min monitoring period emboli in the middle cerebral artery w
ere detected unilaterally in 2, and bilaterally in 7 cases. In another
20 individuals emboli monitoring was done on the day preceding the im
plantation of a mechanical heart valve prosthesis and within 3 weeks p
ostoperatively. No emboli were detected preoperatively. After implanta
tion of an aortic (n = 15) or mitral (n = 5) valve prosthesis emboli s
ignals were detected unilaterally in 4, and bilaterally in 5 cases. Th
eir number was 1-5/10 min in 7, and 24 and 64/10 min, respectively, in
2 cases. In 2 patients having a Saint Jude aortic and mitral and a St
arr-Edwards mitral prosthesis, respectively, the emboli signals ceased
completely or were dramatically reduced after substitution of the art
ificial valves. No source of embolism could be identified intraoperati
vely. It is concluded that the technique of bilateral simultaneous Dop
pler sonography is practicable and increases the sensitivity of emboli
monitoring. Emboli signals, whose nature and prognostic significance
could not yet be clarified, are much more frequent in patients having
a mechanical heart valve prosthesis than anticipated from clinical evi
dence. With the criteria chosen and limiting the search to both middle
cerebral arteries, they can be detected in about half of these patien
ts.