Val E. Pochay

Clinical correlates of high-intensity transient signals detected on transcranial Doppler sonography in patients with cerebrovascular disease.

Background and Purpose High-intensity transient signals detected by transcranial Doppler sonography have been associated with particulate cerebral emboli. Their clinical correlates are poorly understood. This study was undertaken to assess their relation to cerebral ischemia and to determine whether the severity of cerebral arterial stenosis has an impact on their occurrence. Methods We studied 96 arteries in 75 consecutive patients with extracranial or intracranial arterial lesions or potential cardiac sources of cerebral embolism. Sixty patients had histories of cerebral or retinal transient ischemic attacks or infarcts, and 15 were asymptomatic. The diagnosis of ischemia was based on the clinical presentation and was supported by extensive laboratory testing. A transcranial Doppler sonography unit equipped with special software for emboli detection was used. Signals were selected based on criteria established a priori. Results Signals were detected in the territories of 28.3% of symptomatic and 11.6% of asymptomatic arteries. The difference was significant (P=.045). When patients with suspected cardiac embolic sources were excluded, the difference between symptomatic (27.9%) and asymptomatic (2.9%) arteries remained significant (P=.003), and signals were more frequent distal to arteries with more than 50% area stenosis (23.5%) than arteries with stenoses equal to or less than 50% (3.7%) (P=.028). In patients with only extracranial internal carotid artery stenoses, the difference between these degrees of stenosis remained significant (P=.043). Conclusions We conclude that high-intensity transient signals are significantly more common in the territories of symptomatic arteries and distal to lesions causing more than 50% stenosis. These findings may have diagnostic and therapeutic applications.

Cerebral Microembolism and Early Recurrent Cerebral or Retinal Ischemic Events

BACKGROUND AND PURPOSE We investigated whether cerebral microembolism as detected by transcranial Doppler ultrasonography (TCD) identifies patients at an increased risk for early, recurrent cerebral or retinal ischemic events. METHODS Records of consecutive patients examined during a 40-month period in the Neurovascular Laboratory were reviewed for the presence of cerebral microembolism. Of the original 302 patients, 229 with 310 arteries met inclusionary criteria. Follow-up information was obtained from the laboratorys database as well as the hospital records. Microembolus detection studies were performed on TC-2000 or TC-2020 instruments equipped with special software, and criteria established a priori were used for microembolus selection. TCD testing was performed a median interval of 9 days after the initial symptoms of cerebral ischemia. Severity of arterial stenosis was determined by cerebral angiography or noninvasive methods. RESULTS Microembolic signals were detected more frequently in symptomatic (40/140; 28.6%) than asymptomatic (21/170; 12.4%) arteries (P < .001). Ten recurrent ischemic events occurred during a median follow-up of 8 days after TCD examination, all in the territories of symptomatic arteries. Nine events occurred in the territories of microembolic signal positive arteries (9/61; 14.8%) and one in the territory of a microembolic signal-negative artery (1/249; 0.4%) (P < .00). No association was detected in the subgroup with known cardiac lesions. Microembolic signals were more frequent in arteries with lesions causing 70% or more stenosis or occlusion (26/99; 26.3%) than in those with a degree of stenosis less than 70% (17/126; 13.5%) (P = .016). CONCLUSIONS In this retrospective study, microembolic signals were more common in the territories of symptomatic arteries and particularly those with severely stenotic lesions. During a short follow-up, recurrent ischemic events were more common along the territories of arteries with TCD-detected microembolism and previous symptoms of cerebral or retinal ischemia.

Cerebral microembolism and ischemic changes associated with carotid endarterectomy

PURPOSE The purpose of this study is to characterize microembolic signals (MS) that occur during the various phases of carotid endarterectomy (CEA) and to consider their relationship to postoperative changes on magnetic resonance imaging (MRI). METHODS This was a retrospective study of 76 patients who underwent 78 carotid endarterectomies at a referral center. Perioperative transcranial Doppler monitoring and MRI were performed before and after CEA. The types of MS that occurred during phases of surgery were analyzed and compared with MRI changes. RESULTS We observed a clinical stroke in one patient (1.3%) and ipsilateral small areas of silent ischemic change on seven postoperative MRI studies (9.0%). In 95% of CEAs, MS were detected. Only those MS observed in the recovery room that occurred at a rate of more than five per 15 minutes were associated with postoperative MRI ischemic changes (p < 0.0001). CONCLUSIONS Ischemic changes on MRI after CEA are related to postoperative MS.

Intraoperative cerebral high-intensity transient signals and postoperative cognitive function: a systematic review

BACKGROUND Much attention in the literature has focused on the relationship between perioperative microemboli during cardiac and vascular surgery and postoperative cognitive decline. Transcranial Doppler ultrasonography (TCD) has been used to measure high-intensity transient signals (HITS), which represent microemboli during cardiac, vascular, and orthopedic surgery. The purpose of this study was to systematically examine the literature with respect to HITS and postoperative cognitive function. METHODS Systematic PubMed searches identified articles related to the use of TCD and cognitive function in the surgical setting. RESULTS The literature remains largely undecided on the role of HITS and cognitive impairment after surgery, with most studies being underpowered to show a relationship. Although the cognitive effects of HITS may be difficult to detect, subclinical microemboli present potential harm, which may be modifiable. CONCLUSIONS TCD represents a tool for intraoperative cerebral monitoring to reduce the number of HITS during surgery.

Atherosclerosis is associated with delirium after coronary artery bypass graft surgery.

Objectives: To investigate whether atherosclerosis of the ascending aorta, internal carotid arteries, and coronary arteries is predictive of postoperative delirium in subjects undergoing coronary artery bypass graft (CABG) surgery.

Effect of Time and Cerebrovascular Symptoms on the Prevalence of Microembolic Signals in Patients With Cervical Carotid Stenosis

BACKGROUND AND PURPOSE 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. METHODS 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. RESULTS 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). CONCLUSIONS 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.

Cerebral Microembolism in Patients With Retinal Ischemia

BACKGROUND AND PURPOSE We investigated the frequency of cerebral microembolism detected by transcranial Doppler ultrasonography in patients with clinical evidence of retinal ischemia, including transient monocular blindness, central and branch retinal artery infarction, and ischemic oculopathy, and assessed its correlation with carotid artery stenosis. METHODS Records of 331 consecutive patients examined during a 47-month period at the Neurovascular Laboratory were reviewed. Of the original 453 intracranial arteries, 186 middle cerebral arteries (MCAs) satisfied qualifying criteria that excluded patients with cardiac embolic sources. Forty-five MCAs ipsilateral to the symptomatic eye constituted the study group. The control group consisted of 141 asymptomatic MCAs. Microembolus detection studies were performed on transcranial Doppler instruments equipped with special software, and the degree of carotid artery stenosis was measured by cerebral or MR angiography or by color duplex studies. RESULTS Microembolism was detected in 40.0% of study MCAs and 9.2% of controls (P < 0.001). In the study group, microembolic signals were detected in 61.9% of MCAs tested within a week of symptom onset and 20.8% of those tested afterward (P < 0.001). Severe (> or = 70%) carotid stenosis or occlusion was more frequent in the study group (P < 0.001). Microembolic signals were detected in 25.3% and 11.2%, respectively, of MCAs distal to carotid arteries with 70% to 100% and 0% to 69% stenosis (P = 0.013). CONCLUSIONS In patients without cardiac embolic sources, cerebral microembolism is frequently present on the side of retinal ischemia, particularly during the week after onset of symptoms. It is often associated with severe stenosis or occlusion of the ipsilateral carotid artery.

Cerebral Microembolism During Carotid Endarterectomy

BACKGROUND This study was designed to assess the intraoperative risk of cerebral microembolism, as detected by transcranial Doppler ultrasonography, during carotid endarterectomy. PATIENTS AND METHODS Thirty-six patients (37 procedures) with symptomatic (n = 35) or asymptomatic (n = 2) internal carotid artery origin stenosis(> 50%) were monitored continuously during carotid endarterectomy. Special instrumentation was used to detect high-intensity transient signals (HITS) in the middle cerebral artery on the carotid endarterectomy side. All HITS satisfied a priori established criteria. RESULTS The incidence of carotid endarterectomies with formed-element HITS increased at clamp release (23/37, P < 0.001) and shunt opening (7/11, P = 0.014), and during wound closure (13/22, P< 0.005) and shunting (5/11, P = 0.046). HITS with air microbubble characteristics were detected at clamp release (22/37, P < 0.001) and shunt opening (5/11, P = 0.025). CONCLUSIONS HITS do not occur randomly during carotid endarterectomy. Shunting, unclamping, and wound closure are high-risk periods.

Microemboli are not associated with delirium after coronary artery bypass graft surgery

Delirium is an acute change in cognition which occurs frequently after coronary artery bypass graft (CABG) surgery. Cerebral microemboli, from plaque, air, or thrombus, have been hypothesized to contribute to delirium and cognitive decline after CABG. The purpose of this study was to determine if there was an association between cerebral microemboli and delirium after cardiac surgery. Non-delirious patients (n=68) were prospectively enrolled and underwent intraoperative monitoring of the middle cerebral arteries with transcranial Doppler (TCD). TCD signals were saved and analyzed postoperatively for microemboli manually, according to established criteria. Postoperatively, patients were assessed for delirium with a standardized battery. Thirty-three patients (48.5%) developed delirium after surgery. Microemboli counts (mean ± SD) were not significantly different in those with and without delirium (303 ± 449 vs. 299 ± 350; p=0.97). While intraoperative microemboli were not associated with delirium after CABG, further investigation into the source and composition of microemboli can further elucidate the long-term clinical impact of microemboli.

Composition of particles associated with embolic signals on transcranial doppler untrasonography

The composition of particulate emboli associated with detectable signals on transcranial Doppler (TCD) ultrasonography has previously been studied in vitro. The purpose of this investigation was to study the composition of particles associated with similar signals in patients undergoing carotid endarterectomy. We studied carotid endarterectomy specimens from four consecutive patients with internal carotid artery origin, symptomatic, severe, stenosis, and preoperative TCD showing signals that were unidirectional from the baseline, occurred throughout the cardiac cycle, lasted 25-100 ms, had intensities exceeding that of surrounding blood by at least 12 dB, and were associated with a characteristic chirping sound. In all patients, signals with the preceding characteristics were detected in the sup-raclinoid internal carotid artery distal to the symptomatic, cervical stenosis. In Cases 1, 3, and 4, no signals were detected in the contralateral, asymptomatic supraclinoid internal carotid artery, and signals resolved after surgery. Examination of the endarterectomy specimens showed intraluminal thrombi composed of fibrin and platelets in all cases. Our findings suggest that TCD signals with the preceding characteristics may correspond to platelet and fibrin particles originating at stenotic lesions of the cervical internal carotid artery.