Identification of Patients at Risk for Ischaemic Cerebral Complications After Carotid Endarterectomy with TCD Monitoring

Carotid atherosclerotic plaque instability and cognition determined by ultrasound-measured plaque strain in asymptomatic patients with significant stenosis

OBJECTIVE This article describes the use of ultrasound measurements of physical strain within carotid atherosclerotic plaques as a measure of instability and the potential for vascular cognitive decline, microemboli, and white matter changes. METHODS Asymptomatic patients with significant (> 60%) carotid artery stenosis were studied for dynamic measures of plaque instability, presence of microemboli, white matter changes, and vascular cognitive decline in comparison with normative controls and premorbid state. RESULTS Although classically asymptomatic, these patients showed vascular cognitive decline. The degree of strain instability measured within the atherosclerotic plaque directly predicted vascular cognitive decline in these patients thought previously to be asymptomatic according to classic criteria. Furthermore, 26% of patients showed microemboli, and patients had twice as much white matter hyperintensity as controls. CONCLUSIONS These data show that physical measures of plaque instability are possible through interpretation of ultrasound strain data during pulsation, which may be more clinically relevant than solely measuring degree of stenosis. The data also highlight the importance of understanding that the definition of symptoms should not be limited to motor, speech, and vision function but underscore the role of vascular cognitive decline in the pathophysiology of carotid atherosclerotic disease. Clinical trial registration no.: NCT02476396 (clinicaltrials.gov).

Monitoring cerebral ischemia during carotid endarterectomy and stenting

Current therapy for carotid stenosis mainly includes carotid endarterectomy and endovascular stenting, which may incur procedure-related cerebral ischemia. Several methods have been employed for monitoring cerebral ischemia during surgery, such as awake neurocognitive assessment, electroencephalography, evoked potentials, transcranial Doppler, carotid stump pressure, and near infrared spectroscopy. However, there is no consensus on the gold standard or the method that is superior to others at present. Keeping patient awake for real time neurocognitive assessment is effective and essential; however, not every surgeon adopts it. In patients under general anesthesia, cerebral ischemia monitoring has to rely on non-awake technologies. The advantageous and disadvantageous properties of each monitoring method are reviewed.

Developing and validating risk prediction models in an individual participant data meta-analysis

Background

Risk prediction models estimate the risk of developing future outcomes for individuals based on one or more underlying characteristics (predictors). We review how researchers develop and validate risk prediction models within an individual participant data (IPD) meta-analysis, in order to assess the feasibility and conduct of the approach.

Methods

A qualitative review of the aims, methodology, and reporting in 15 articles that developed a risk prediction model using IPD from multiple studies.

Results

The IPD approach offers many opportunities but methodological challenges exist, including: unavailability of requested IPD, missing patient data and predictors, and between-study heterogeneity in methods of measurement, outcome definitions and predictor effects. Most articles develop their model using IPD from all available studies and perform only an internal validation (on the same set of data). Ten of the 15 articles did not allow for any study differences in baseline risk (intercepts), potentially limiting their model’s applicability and performance in some populations. Only two articles used external validation (on different data), including a novel method which develops the model on all but one of the IPD studies, tests performance in the excluded study, and repeats by rotating the omitted study.

Conclusions

An IPD meta-analysis offers unique opportunities for risk prediction research. Researchers can make more of this by allowing separate model intercept terms for each study (population) to improve generalisability, and by using ‘internal-external cross-validation’ to simultaneously develop and validate their model. Methodological challenges can be reduced by prospectively planned collaborations that share IPD for risk prediction.

Primary Stroke Prevention: Medical Therapy Versus Revascularization

Asymptomatic carotid-artery atherosclerotic vascular disease identifies patients at heightened risk of major adverse cardiovascular events including ischemic stroke. Observational and registry analyses demonstrate that this risk extends beyond that attributable to carotid atherosclerosis itself and includes events manifesting in other vascular territories, such as myocardial infarction. However, randomized trials aimed specifically at treating carotid stenosis have shown benefit in terms of reducing ischemic stroke in appropriately selected patients. Therefore, the approach to primary prevention in patients with stable carotid disease must include a comprehensive strategy to reduce cerebrovascular-specific and overall cardiovascular risk through lifestyle changes and intensive medical therapies.

Longer time interval between carotid cross-clamping and shunting is associated with increased 30-day stroke and death rate

BACKGROUND

The benefit of carotid endarterectomy (CEA) in patients with a significant (>70%) (a)symptomatic stenosis has been proven thoroughly in major trials. It is unknown whether, after cross-clamping the carotid artery, the time interval between determination that a shunt is needed and the actual functioning of the shunt, defined as the need for shunt-to-shunt time (NST), influences 30-day morbidity and mortality rate after CEA.

METHODS

Experienced vascular surgeons performed 851 CEAs with a selective shunting protocol based on perioperative transcranial Doppler measurement and electroencephalographic findings, and data were analyzed retrospectively. The study included 156 shunted patients.

RESULTS

Longer NST was associated with an increase in the 30-day stroke/death rate. A binary logistic regression model was used to determine a 2-tailed P value of .004 and an odds ratio of 1.5/min increase of the NST. There was no influence on stroke-death rate of gender, age, symptomatic or asymptomatic stenosis, the use of a patch or not, or the number of periprocedural microembolic signals.

CONCLUSION

If CEA is performed with a selective shunting protocol, a longer NST increases the 30-day stroke/death rate. These results support a strong recommendation that shunt placement should be as quick as possible.

Mechanisms of gender-related outcome differences after carotid endarterectomy

OBJECTIVE

Large randomized trials have confirmed a difference in outcome after carotid endarterectomy (CEA) between men and women. In this review, we aimed to provide an overview of the gender-specific characteristics causing these perioperative and long-term outcome differences between men and women after CEA.

METHODS

A systematic search strategy with the synonyms of 'gender' and 'carotid endarterectomy' was conducted from PubMed and EMBASE databases. Only 11 relevant studies specifically discussing gender-specific related characteristics and their influence on outcome after CEA could be identified.

RESULTS

Due to the limited number of included studies, pooling of findings was impossible, and results are presented in a descriptive manner. Each included study described only one possible gender-specific factor. Differences in carotid artery diameter, sex hormones, sensitivity for antiplatelet therapy, plaque morphology, occurrence of microembolic signals, and restenosis rate have all been suggested as gender-specific characteristics influencing outcome after CEA.

CONCLUSION

Higher embolic potential in women and relatively stable female plaque morphology are the best-described factors influencing the difference in outcomes between men and women. However, the overall evidence for outcome differences by gender-specific characteristics in the literature is limited.

Asymptomatic spontaneous cerebral emboli predict cognitive and functional decline in dementia

BACKGROUND

Spontaneous cerebral emboli (SCE) are frequent in Alzheimer's disease (AD) and vascular dementia (VaD). We investigated the effect of SCE on the rates of cognitive and functional decline in AD and VaD.

METHODS

One hundred thirty-two patients with dementia (74 AD, National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association [NINCDS/ADRDA] criteria; 58 VaD, National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l'Enseignement en Neurosciences [NINDS/AIREN] criteria) underwent 1-hour transcranial Doppler for detection of SCE (mean [SD] age 75.5 (7.4) years; 46% female). Neuropsychological tests (Mini-Mental State Examination [MMSE], Alzheimer's Disease Assessment Scale-Cognitive subscale [ADAS-Cog], and Neuropsychiatric Inventory [NPI]) and assessment of activities of daily living (Interview for Deterioration in Daily Living Activities in Dementia [IDDD]) were performed initially and 6 months later. SCE positive (SCE+ve, n = 47) and SCE negative (SCE-ve, n = 85) patients were compared using repeated measures analyses of variance (ANOVAs) adjusted for age, gender, and cardiovascular risk factors.

RESULTS

SCE+ve patients with dementia, both AD and VaD, suffered a more rapid decline in cognitive functioning over 6 months (ADAS-cog, mean increase 7.1 for SCE+ve compared with 3.3 for SCE-ve, p = .006) and activities of daily living (IDDD, mean increase 24.4 for SCE+ve compared with 10.8 for SCE-ve, p = .014).

CONCLUSIONS

Asymptomatic SCE are associated with an accelerated cognitive and functional decline in dementia. SCE may be a potentially treatable cause of disease progression in dementia.

Influence of Antiplatelet Therapy on Cerebral Micro-Emboli after Carotid Endarterectomy using Postoperative Transcranial Doppler Monitoring

AIM

To study the effect of different antiplatelet regimens (APT) on the rate of postoperative TCD registered micro-embolic signals (MES) following carotid endarterectomy (CEA).

DESIGN

Prospective, randomised, double-blinded, pilot study.

METHODS

The study group of 102 CEA patients (76 men, mean age 66.8 years) was randomised to routine Asasantin (Dipyridamole 200mg/Aspirin 25mg) twice daily (group I; n=39), Asasantin plus 75 mg Clopidogrel once daily (group II; n=33), or Asasantin plus Rheomacrodex (Dextran 40) 100g/L iv; 500 ml (group III; n=30). TCD monitoring of the ipsilateral middle cerebral artery for the occurrence of MES was performed intra-operatively and during the second postoperative hour following CEA. Primary endpoints were the rate of postoperative emboli and the occurrence of cerebrovascular complications. Secondary endpoint was any adverse bleeding.

RESULTS

There were no deaths or major strokes. We observed 2 intraoperative TIA's (group II and III) and 1 postoperative minor stroke (group I). In comparison with placebo, Clopidogrel or Rheomacrodex in addition to Asasantin produced no significant reduction in the number of postoperative MES. There was no significant difference between the number of postoperative MES and different antiplatelet regimens. The incidence of bleeding complications was not significantly different between the 3 APT groups.

CONCLUSION

In the present study, we could not show a significant influence of different antiplatelet regimens on TCD detected postoperative embolization following CEA.

Timing of clinically significant microembolism after carotid endarterectomy

PURPOSE

Post-operatively detected transcranial Doppler (TCD) embolic signals (ES) are associated with an increased risk of carotid endarterectomy (CEA) stroke/TIA. The aims here were to quantify this risk and determine the most efficient monitoring protocol.

METHODS

Sequential patients undergoing CEA (enrolled in a randomised, blinded, placebo-controlled trial of peri-operative dextran therapy) had 30-min TCD monitoring in the first post-operative hour. 30-min monitoring was also performed 2-3, 4-6 and 24-36 h post-operatively. First post-operative hour ES counts were correlated with peri-operative ipsilateral carotid stroke/TIA to determine the size of a clinically significant ES load and the magnitude of the associated risk. The exact Cochran-Armitage test for trend in proportions was used to determine when a clinically significant ES load was first detected.

RESULTS

141 patients (mean age 69.3 years, 72% male) were monitored during the first post-operative hour. An ES count >10 per recording was identified as the best overall predictor of ipsilateral stroke/TIA (sensitivity 72%, specificity 89%). 3/119 (2.5%) patients with 0-10 ES had ipsilateral carotid events compared to 8/22 (36.4%) patients with 11-115 ES (OR = 22.1, 95% CI 4.5, 138.4, p < 0.0001). 13/18 (72%) of subjects with >10 ES were identified in the first post-operative hour with no significant increase in the number of new cases over the subsequent 24-36 post-operative h (p = 0.354).

CONCLUSION

Patients with clinically significant post-operative microembolism had an approximately 15 times higher risk of ipsilateral stroke/TIA and most were identified during a 30-min study in the first post-operative hour.