Clinical Relevance of Intracranial Microembolic Signals in Patients With Left Ventricular Assist Devices

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Abstract
Background and Purpose The use of left ventricular assist devices has become an established method in bridging patients with end-stage cardiac failure to heart transplantation. Since thromboembolism is one of the major complications, we undertook this study to evaluate the clinical significance of Doppler microembolic signals (MES) in patients with left ventricular assist devices. Methods Six patients with left ventricular assist devices were monitored for MES with transcranial Doppler ultrasonography during the first 30 postoperative days. Additionally, repeated (10 per day and patient) and prolonged (3 hours per patient) monitorings were performed to assess the adequacy of the 30-minute recordings. Three observers evaluated 30 randomly assigned monitorings in a blinded fashion to assess the interobserver variability. The relation between MES counts and clinical, radiological, hemostaseological, and pump flow parameters and the predictive value of MES counts regarding the occurrence of embolic events was evaluated. Results Ten ischemic cerebrovascular accidents and 2 peripheral thromboembolic events occurred during the observation period of 177 days (total incidence, 6.8%). MES were found in 143 of 170 monitorings (84.1%). Their counts were significantly higher on days with clinically manifest embolic events as compared with event-free days (18.5 [3-74] versus 4 [0-52], respectively, median and 95% CI; P <.001, Mann-Whitney). The predictive value of MES counts above 7 per 30 minutes was high (75%). Significant differences in the incidence and counts of MES as well as in the incidence of clinically manifest embolic events were noted among the six patients (all P <.01) without equal differences in anticoagulant treatment or pump flow. Interobserver agreement was high ( P =.78 to .89, unpaired Student’s t test). Considerable short- and long-term intrapatient variations of MES counts, without consistent pattern, were noted. Conclusions Serial monitoring for MES is prognostically superior to single monitorings in patients with left ventricular assist devices. In the future, this new application mode may individually guide anticoagulation strategies and even influence the decision regarding early cardiac transplantation versus long-term use of the assist devices.