Cheiro-oral syndrome due to severe stenosis of the middle cerebral artery.
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Cerebral Arterial Diseases↗
Biomedical subjects
D G Nabavi
Publications and source records attributed to D G Nabavi.
Hyperinsulinism and cerebral microangiopathy.
BACKGROUND AND PURPOSE: High insulin levels are a recognized risk factor for atherosclerosis. Microvascular endothelium is more susceptible to metabolic and mitogenic effects of insulin than large-vessel endothelium. Besides their atherogenic effect, high insulin levels impair fibrinolysis by enhancing plasminogen activator inhibitor-1. We undertook this study to evaluate the hypothesis that elevated serum insulin and C-peptide levels are related to cerebral small-vessel disease rather than large-vessel pathology. METHODS: One hundred ninety-four consecutive patients presenting with symptomatic cerebrovascular disease were assigned to three subgroups that were differentiated by clinical presentations, brain imaging studies, and extracranial as well as transcranial vascular ultrasound findings: (1) patients with lacunes (n = 20), (2) patients with subcortical arteriosclerotic encephalopathy (n = 35), and (3) patients with strokes due to large-vessel disease (n = 99). Patients who had suffered a cryptogenic (n = 9) or cardioembolic (n = 16) stroke or who showed characteristics of the microangiopathy and macroangiopathy groups (n = 15) were not further evaluated. Thirty patients without manifestations of cerebrovascular disease were also examined. Fasting blood glucose, insulin, and C-peptide levels were determined in all subjects. RESULTS: There were no significant differences in age or sex among the three groups and control patients. Insulin levels were significantly higher in the lacunar group compared with the subcortical arteriosclerotic encephalopathy group, the macroangiopathy group, and the control patients (median [interquartile range]: 103.8 [198.6], 72.0 [103.2], 66.0 [57.0], and 52.2 [57.0] pmol/L, respectively; all P < .05, Mann-Whitney test). There was a statistically significant difference in insulin concentrations between the microangiopathy group (subcortical arteriosclerotic encephalopathy and lacunes) and the macroangiopathy and control groups (81.0 [110.4], 66.0 [57.0], and 55.2 [57.0] pmol/L, respectively; all P < .05, Mann-Whitney). The same was true for the distribution of C-peptide levels and to a minor extent blood glucose values, but these differences failed to reach statistical significance. CONCLUSIONS: Elevated insulin levels potentially represent a pathogenetic factor in the development of cerebral small-vessel disease, predominantly in patients presenting with lacunes. Whether this is due solely to atherosclerotic changes of the small penetrating arteries or whether changes in hemorheology are operative as well remains to be evaluated.
Aged↗
A novel technique for identification of doppler microembolic signals based on the coincidence method: in vitro and in vivo evaluation.
BACKGROUND AND PURPOSE: The applicability of a novel differentiation technique in embolus detection based on the coincidence principle and using a multigate probe was evaluated in this study. METHODS: According to the coincidence method, high-intensity transients should only be classified as microembolic signals if they appear sequentially in the two sample volumes monitored and within a defined time window calculated from the blood velocity and the spatial distance between the insonation depths. Part A: microbubbles were introduced in a continuous flow bench model of the middle cerebral artery to evaluate the accuracy of the multigate probe in embolus detection. Part B: in the subjects and patients, the minimal and maximum time delays in the appearance of microembolic signals in the two middle cerebral artery sample volumes were calculated as 0.01 second and set at 0.1 second, respectively. The multigate probe was used to monitor (1) 5 normal volunteers in whom 1008 artifact signals were produced,(2) 2 patients undergoing aortic valve replacement surgery, and (3) 12 patients with potential cardiac or carotid embolic sources. RESULTS: In the bench model, 95.5% of microembolic signals produced by microbubbles appeared in the two sample volumes with a time delay between 0.02 and 0.05 second, while in the remaining 4.5% a shorter passage time of 0.01 second was measured. A total of 1968 high-intensity signals were recorded in subjects and patients. All but 20 of these (99%) appeared in both monitoring channels within the above time frame. To summarize, 996 (98.8%) of the 1004 artifact signals and 943 (98.1%) of the 961 microembolic signals were correctly classified. CONCLUSIONS: Application of the coincidence theory to distinguish microembolic signals from artifacts provides a promising new technique with high sensitivity and specificity that could decisively improve the validity of embolus detection.
Adult↗
Clinical relevance of intracranial microembolic signals in patients with left ventricular assist devices. A prospective study.
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.
Adult↗
Detection of microembolic signals in patients with middle cerebral artery stenosis by means of a bigate probe. A pilot study.
BACKGROUND AND PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
Adult↗
HIV-associated stroke: report of two unusual cases.
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Acquired Immunodeficiency Syndrome↗
Quantitative assessment of cerebral hemodynamics using CT: stability, accuracy, and precision studies in dogs.
PURPOSE: The limited clinical availability of currently used methods to measure regional cerebral blood volume (CBV) and cerebral blood flow (CBF) represents an important restriction. We undertook this study to evaluate a new dynamic CT method to measure CBV and CBF in normal and ischemic tissue. METHOD: A total of 21 dynamic CT studies were performed in seven male beagles. The contrast enhancement curves of the carotid arteries and of various brain regions were deconvolved to obtain CBV and CBF. The stability of the deconvolution method employed was assessed by comparing three data sets obtained by analyses of one, two, and four regions of interest (ROIs), all covering the entire brain area. The accuracy of CT-derived CBF was analyzed for normal (n = 5 studies) and ischemic (n = 7 studies) brain tissue using fluorescent microspheres. Repetitive CT studies were performed to evaluate the precision of the CT measurements. RESULTS: The stability of the deconvolution method was high with variabilities of 2.3% (CBV), 5.9% (CBF), and 8.9% (mean transit time), respectively. The correlation between the CT and the microsphere measurements was good for both normal and ischemia studies (r > 0.78, slope > 0.9). The variability of the CT CBF (30.6%) was higher than that of the CT CBV (12.3%) measurements. CONCLUSION: Our novel dynamic CT method is stable with respect to the sizes of ROIs used, allowing for accurate measurements of CBV and CBF in both normal and ischemic tissue. Further studies are necessary to evaluate the variability of this method under controlled physiologic conditions.
Animals↗
Microembolic load in asymptomatic patients with cardiac aneurysm, severe ventricular dysfunction, and atrial fibrillation. Clinical and hemorheological correlates.
Transcranial Doppler sonography has become a widely used method for detecting cerebral circulating microemboli (ME) arising from the carotid arteries or the heart. Yet, studies on subgroups of patients with distinct cardiac sources of embolism are still limited. The same holds true for investigation on the relationship between microembolization and hemorheological parameters. A total of 142 patients suffering from left ventricular aneurysm (LVA, n = 52), severe left ventricular dysfunction (LVD, n = 43), or chronic atrial fibrillation (AF, n = 47) were enrolled in this study. All patients had been neurologically asymptomatic for at least 1 month. Further relevant embolic disorders of the carotid arteries and the heart had been excluded. Unilateral monitoring for ME over the middle cerebral artery was performed for 30 min. Blood was drawn after each monitoring for determination of plasmatic coagulation parameters, as well as plasma viscosity, and platelet reactivity. The overall prevalence of ME was 31%, with a slightly higher prevalence in patients with LVA (37%) compared to patients suffering from AF (30%) or LVD (26%). With single-factor analysis, a trend towards higher ME prevalences was found with (a) a history of remote embolic events, (b) ineffective anticoagulation, (c) increased platelet aggregation, or (d) increased plasma viscosity (all p > 0.1). The combination of ineffective anticoagulation in conjunction with increased platelet aggregation, however, was significantly associated with higher ME rates even after adjustment for other factors by logistic regression analysis. Our results demonstrate a low ongoing microembolic activity in asymptomatic patients suffering from LVA, LVD and AF. An activated plasmatic coagulation system together with increased platelet aggregation contributes to ME generation.
Adult↗