Simultaneous Bilateral Transcranial Doppler Sonography for the Detection of Middle Cerebral Artery Microemboli from Mechanical Prosthetic Heart Valves

Abstract

Simultaneous bilateral transcranial Doppler emboli monitoring was carried out in 20 patients having mechanical heart valve prostheses (aortic, n = 7, and/or mitral, n = 13) for up to 23 (mean 8 ± 7) years. During a 10-min monitoring period emboli in the middle cerebral artery were detected unilaterally in 2, and bilaterally in 7 cases. In another 20 individuals emboli monitoring was done on the day preceding the implantation of a mechanical heart valve prosthesis and within 3 weeks postoperatively. No emboli were detected preoperatively. After implantation of an aortic (n = 15) or mitral (n = 5) valve prosthesis emboli signals were detected unilaterally in 4, and bilaterally in 5 cases. Their 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 Starr-Edwards mitral prosthesis, respectively, the emboli signals ceased completely or were dramatically reduced after substitution of the artificial valves. No source of embolism could be identified intraoperatively. It is concluded that the technique of bilateral simultaneous Doppler 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 evidence. With the criteria chosen and limiting the search to both middle cerebral arteries, they can be detected in about half of these patients.