Microembolic Signals In Patients Research Articles

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We undertook TCD examination combined with transesophageal echocardiography (TEE) and measurements of hematological markers for coagulation, fibrinolysis and platelet function to clarify the clinical significance of micro-embolic signals derived from the heart. We examined nine patients with prosthetic valves including two with cardioembolic stroke (CE) and 11 CE patients without prosthetic valves. All the patients were receiving anticoagulation therapy at the time of the study. TCD study demonstrated 3-54/30 min micro-embolic signals in six of the nine patients with prosthetic valves, but no signal in those without valve replacement. TEE study demonstrated cavitation phenomenon in eight of the nine patients with prosthetic valves, but in none of the patients without valve replacement. No other findings of TEE or hematological examination were correlated with the frequncy of micro-embolic signals. These results indicate a close relationship between cavitation phenomenon and micro-embolic signals in patients with prosthetic valve. Ordinary anticoagulation (INR: international normalized ratio 2.0-3.0) does not reduce the frequency of micro-embolic signals in patients with prosthetic heart valve. However, very high intensity anticoagulation (INR>3.5) might decrease the frequency of micro-embolic signals. Further studies are necessary to clarify the clinical significance of microembolic signals.

Detection of microembolic signals in patients with middle cerebral artery stenosis by means of a bigate probe. A pilot study.

Middle cerebral artery (MCA) stenosis is a relatively rare occlusive disease with an annual stroke risk of approximately 7% to 8%. However, the frequent coincidence of cardiac or ipsilateral carotid artery disease may lead to difficulties in identifying the relevant embolizing source in symptomatic patients. We undertook this study to evaluate the prevalence of microembolic signals (MES) as well as the potential and limitations of bigate monitoring in patients with MCA stenosis. Fourteen patients aged 33 to 87 years with angiographically demonstrated symptomatic (acute, n = 2; chronic, n = 8) or asymptomatic (n = 4) MCA stenosis were examined. Six patients (43%) had additional cardiac (n = 3) or carotid artery (n = 3) disease. By means of a bigate probe, simultaneous insonation of prestenotic and poststenotic vessel segments was attempted. In 10 patients (71%), MES detection could be performed sufficiently at target vessel sites. In the remaining patients, either prestenotic (n = 3) or poststenotic (n = 1) monitoring was not satisfactory due to insufficient transtemporal bone window or the great length or extent of MCA stenosis. Poststenotic MES were detectable in 2 acutely symptomatic and 1 asymptomatic patient (prevalence, 21%). In the latter case, the sequential appearance of MES in both prestenotic and poststenotic channels excluded MCA stenosis but strongly favored coexisting carotid artery stenosis as the active embolic source. MES are detectable in patients with MCA stenosis. Bigate monitoring in this setting is feasible and allows identification of the active source among "competing" embolizing conditions.

Clinical relevance of intracranial microembolic signals in patients with left ventricular assist devices. A prospective study.

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. 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. 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. 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.

Effect of time and cerebrovascular symptoms of the prevalence of microembolic signals in patients with cervical carotid stenosis.

High-intensity transient signals (HITS) detect ed by transcranial Doppler ultrasonography correspond to microemboli in intracranial arteries. The aim of this study was to determine the time course of cerebral microembolism in patients with symptomatic internal carotid artery stenosis and to assess its relation to specific symptoms of cerebral ischemia. On the basis of criteria established a priori, 69 middle cerebral arteries were selected from a series of consecutive studies obtained at our neurovascular laboratory. All patients had radiological evidence of cervical internal carotid artery disease and had corresponding symptoms. A TC-2000 instrument equipped with special software for microembolus detection was used. Accepted signals were unidirectional from baseline, had a chirping sound, were 9 dB higher than the surrounding blood, and lasted 25 milliseconds or more. HITS were identified in 20 of 69 (29%) arteries. The median interval between onset of symptoms and time of testing was 4 days for HITS-positive arteries and 12 days for those that were HITS negative (P=.0046). Fourteen of 32 (44%) arteries with transient ischemic attacks and 6 of 37 (16%) arteries with cerebral infarction were HITS positive (P=.012). In patients with symptomatic carotid stenosis, HITS are detected more frequently when patients are tested soon after symptoms of cerebral ischemia. HITS are also more prevalent in the territories of arteries with transient ischemic attacks rather than cerebral infarction. These findings may have diagnostic and therapeutic implications.

Cardiac microembolism: prevalence and clinical outcome

High intensity transient signals (HITS) have been identified ultrasonically in patients with extracranial vascular or cardiac disease and are suggestive of microembolic material. We studied the prevalence of these signals in 60 patients with increased risk for cardioembolic stroke and in a control group of 20 subjects. Patient groups ( n = 20) were characterized by either non-rheumatic atrial fibrillation (AFIB) (I) or a history of prosthetic valve surgery with AFIB (II) or without AFIB (III). Embolic signals were not seen in the control group. In group I, 3 patients (15%) demonstrated HITS, in groups II and III 10 patients (50%). Microembolic signals in patients with prosthetic heart valves (II, III) had a higher signal intensity, indicating different embolic material. There was no correlation of microembolic signals with the anticoagulant treatment or the position of the prosthetic valve. HITS were found in 1 9 (11%) of the patients with a bioprosthetic valve as compared to 19 31 (61%) with a mechanical valve. After 6–12 months, 1 of 12 HITS positive patients had experienced a stroke and 2 had died. None of the 28 patients without HITS had suffered a stroke, 2 had died. Microembolic signals are frequent events in patients with mechanical prosthetic valves. In these patients they do not appear to be a major prognostic factor for an impending cardioembolic stroke.

Variability of Doppler Microembolic Signal Counts in Patients With Prosthetic Cardiac Valves

The purpose of this study was the evaluation of intraobserver, interobserver, and intrasubject variability in the Doppler detection of microembolic signals in patients with mechanical prosthetic valves. Simultaneously, the feasibility of automated embolus detection by means of a neuronal network was investigated. From 25 patients with mechanical prosthetic heart valves, single transcranial Doppler monitoring sessions of 30 minutes' duration were recorded on videotape, randomized, and subsequently analyzed by eight independent trained observers from three centers. Three observers evaluated these tapes on three separate occasions, blinded to their previous results. An additional 48 patients with prosthetic heart valves were repetitively monitored with transcranial Doppler ultrasonography for 30 minutes three times within 1 year to examine the long-term variability in the occurrence of microembolic signals. Finally, in an effort to assess the short-term intrasubject variability, 20 patients were examined for 90 minutes, and the results of the three 30-minute periods were compared. The interobserver, intraobserver, and intrasubject (both short- and long-term) variability was evaluated. No significant differences in microembolic signal counts were found among the different observers, between the human observers and the neuronal network, or among the three separate evaluations of stored data by the same observer. The same was true for repeat examinations of the same patient (P > .05, Student's two-paired t test and Friedman's test). The detection of microembolic signals in patients with prosthetic cardiac valves is a reproducible technique. The reliable performance of the neuronal network argues for a broader use of this device. The intrasubject stability of the microembolic rate over 1 year supports the concept that the underlying emboligenic process is associated with intrinsic mechanical properties of the valve implant and not due to a thromboembolic process in the heart.

Detection of middle cerebral emboli during coronary artery bypass surgery using transcranial Doppler sonography.

HomeStrokeVol. 21, No. 10Detection of middle cerebral emboli during coronary artery bypass surgery using transcranial Doppler sonography. Free AccessAbstractPDF/EPUBAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessAbstractPDF/EPUBDetection of middle cerebral emboli during coronary artery bypass surgery using transcranial Doppler sonography. M J Harrison, W Pugsley, S Newman, C Paschalis, L Klinger, T Treasure and B Aspey M J HarrisonM J Harrison Search for more papers by this author , W PugsleyW Pugsley Search for more papers by this author , S NewmanS Newman Search for more papers by this author , C PaschalisC Paschalis Search for more papers by this author , L KlingerL Klinger Search for more papers by this author , T TreasureT Treasure Search for more papers by this author and B AspeyB Aspey Search for more papers by this author Originally published5 Apr 2018https://doi.org/10.1161/str.21.10.1512aStroke. 1990;21:1512"Detection of middle cerebral emboli during coronary artery bypass surgery using transcranial Doppler sonography.." 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