Neurocognitive Changes After Carotid Revascularization According to Perfusion Parameters: A Meta-analysis of Current Literature

BACKGROUND

Although the clinical outcomes continue to be scrutinized, there are a few data summarizing the changes in perfusion parameters in postoperative patients. The objective was to undertake a systematic literature review and perform a meta-analysis to assess the effects of cerebral perfusion changes in cognitive and functional status.

METHODS

A systematic search was conducted in July 2018 identifying articles comparing perfusion parameter changes before and after carotid revascularization in patients with carotid artery stenosis. Combined overall effect sizes were calculated using random-effects models.

RESULTS

The literature search identified 1031 unique articles eligible for analysis. Sixteen studies including 755 patients were identified. The studies were different for many methodological factors, for example, sample size, type of patients, statistical measure, type of test, timing of assessment, and so on. There were no differences in cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO₂), and relative cerebral blood volume (rCBV) between preintervention and postintervention, but there was a significant increase of cerebral blood flow (CBF) (95% confidence interval [CI] standardized mean difference [Std. MD] : -0.83 [-1.27, -0.40]; P = 0.0002; I² = 68%) and relative cerebral blood flow (rCBF) (95% CI Std. MD: -0.72 [-1.61, -0.27]; P < 0.0001; I² = 48%) after operation. In addition, the perfusion of mean transit time (MTT) (95% CI Std. MD: 1.26 [0.62, 1.90]; P = 0.0001; I² = 84%), oxygen extraction fraction (OEF) (95% CI Std. MD: 0.78 [0.24, 1.33]; P = 0.005; I² = 0%), time to peak (TTP) (95% CI Std. MD: 0.46 [0.16, 0.77]; P = 0.003; I² = 47%), and relative mean transit time (rMTT) (95% CI Std. MD: 0.41 [0.33, 0.50]; P < 0.00001; I² = 67%) was higher before than after operation.

CONCLUSIONS

The increase in changes in CBF and rCBF and the decrease in MTT, OEF, TTP, and rMTT after operation may indicate the improvement of cognition in the short term. Intraoperative perfusion parameters could be an important adjuvant monitoring method in neurocognitive changes after carotid revascularization.

False ischaemic penumbras in CT perfusion in patients with carotid artery stenosis and changes following angioplasty and stenting

INTRODUCTION

Carotid artery stenosis influences CT perfusion (CTP) studies, sometimes manifesting as a false ischaemic penumbra (FIP). This study aims to estimate the incidence of FIP in patients with carotid artery stenosis, establish their relationship with the degree of stenosis, and measure quantitative and qualitative changes in CTP after carotid angioplasty and stenting (CAS).

METHODS

Between October 2013 and June 2015, we prospectively selected 26 patients with carotid stenosis who underwent CAS, with CTP being performed 2-10 days before and after CAS.

RESULTS

Sixteen patients had unilateral stenosis (11 in the subgroup displaying < 90% stenosis and 5 in the subgroup with ≥ 90% stenosis) and 10 patients had bilateral stenosis. The incidence of FIP in patients with carotid artery stenosis was 38.5%. Risk of FIP increased in direct relation to degree of stenosis, with a relative risk of 11 in the subgroup with ≥ 90% stenosis with respect to the subgroup displaying < 90% stenosis (95% CI, 1.7-71.3; P=.0005). There were statistically significant changes in the parameters CBF, TTP, MTT, and Tmax CTP, which reverted after angioplasty. No significant changes were found in CBV.

CONCLUSIONS

Carotid artery stenosis involves changes in CTP parameters. Patients with ≥ 90% stenosis carry a high risk of FIP; CTP studies may therefore be misinterpreted in these cases. Changes in CTP parameters are reverted after CAS.

Role of Extracranial Carotid Duplex and Computed Tomography Perfusion Scanning in Evaluating Perfusion Status of Pericarotid Stenting

Carotid stenting is an effective treatment of choice in terms of treating ischemic stroke patients with concomitant carotid stenosis. Though computed tomography perfusion scan has been recognized as a standard tool to monitor/follow up this group of patients, not everyone could endure due to underlying medical illness. In contrast, carotid duplex is a noninvasive assessment tool and could track patient clinical condition in real time. In this study we found that “resistance index” of the carotid ultrasound could detect flow changes before and after the stenting procedure, thus having great capacity to replace the role of computed tomography perfusion exam.

Advances in the management of carotid artery disease: focus on recent evidence and guidelines

Recent landmark randomized trials and society guidelines have significantly revised the management of carotid artery disease. Duplex ultrasonography is the recommended initial diagnostic test for the assessment of extracranial carotid artery stenosis. Carotid artery imaging is reasonable in select patients scheduled for coronary artery bypass graft (CABG) surgery. Carotid revascularization can be achieved safely and effectively with carotid endarterectomy or carotid artery stenting. Because each procedure has a different risk/benefit profile, the optimal approach is to match the particular patient to the intervention that maximizes outcome benefit. Carotid revascularization is recommended in patients scheduled for CABG surgery when the carotid artery stenosis is symptomatic and/or bilateral. Further trials are required to guide the management of asymptomatic unilateral carotid artery stenosis in patients undergoing CABG surgery. Aggressive medical therapy remains the gold standard for intracranial carotid artery disease because landmark trials have shown no outcome improvement with vascular bypass or percutaneous angioplasty and stenting. A large recent trial showed that local anesthesia, as compared with general anesthesia, for carotid endarterectomy has no major clinical outcome advantage. Although carotid artery stenting is associated with a reduced risk of myocardial ischemia, it still has important risks of stroke and hemodynamic instability that significantly affect clinical outcome. The timing and choice of carotid revascularization technique ultimately depends on multiple clinical factors.

Management of carotid disease in patients undergoing coronary artery bypass surgery: is it time to change our approach?

PURPOSE OF REVIEW

The management of concurrent severe carotid and coronary disease is a subject of ongoing debate in the absence of randomized clinical trials. Amidst the growing controversy, the clinician has to carefully tailor the best strategy for a given patient based on neurologic and cardiac symptoms. This review aims to compile current evidence in this area to help plan strategies for the optimal management of coexisting severe carotid and coronary disease.

RECENT FINDINGS

Carotid revascularization with carotid endarterectomy (CEA) or stenting (CAS) is frequently performed in conjunction with coronary artery bypass surgery (CABG) in the United States for asymptomatic carotid disease. The risk of perioperative stroke with unilateral asymptomatic 70-99% carotid stenosis is likely small based on several observational data. Moreover, the risk associated with both staged and combined CEA-CABG procedures in the asymptomatic population may outweigh any benefit. Carotid artery stenting is an alternative option in patients with severe coronary disease who are considered 'high risk' for CEA. Neurologically symptomatic patients require carotid revascularization prior to or in conjunction with CABG surgery. Ultimately, the choice of carotid revascularization or conservative management will depend on clinical characteristics, anatomy, and local expertise.

SUMMARY

Severe carotid disease in the CABG population is often unilateral and asymptomatic. Based on the available data, conservative carotid therapy in the low-risk asymptomatic individuals is likely the best treatment option. Carotid revascularization may be justified in symptomatic or high-risk patients such as those with contralateral carotid occlusion or bilateral severe stenosis.

Comparison between acetazolamide challenge and 10% carbon dioxide challenge perfusion CT in rat C6 glioma

RATIONALE AND OBJECTIVES

The aim of this study was to investigate the effect of perfusion computed tomography (PCT) with acetazolamide (ACZ) challenge and compare it to 10% carbon dioxide (CO(2)) challenge in rat C6 glioma.

MATERIALS AND METHODS

PCT was performed on 32 rats, including 20 with orthotopically implanted C6 gliomas and 12 serving as controls. Ten rats with gliomas and six normal rats underwent PCT with ACZ challenge. The other 10 rats with gliomas and six normal rats underwent PCT with 10% CO(2) challenge. The raw data were processed using Philips computed tomographic brain perfusion software. Perfusion parameters before and after the challenge were recorded. Percentage changes due to ACZ administration and 10% CO(2) challenge were calculated. Pearson's correlation coefficients were used to investigate relationships between percentage changes in perfusion parameters and vascular endothelial growth factor and microvessel density.

RESULTS

In C6 gliomas, percentage change in cerebral blood flow was significantly different between ACZ (72.73%) and 10% CO(2) (28.47%) challenge (P < .01). Percentage change in cerebral blood volume was 37.85% with ACZ and 24.69% with 10% CO(2) challenge (P = .02). In controls, percentage change in cerebral blood flow was significantly different between ACZ (117.42%) and 10% CO(2) (65.86%) challenge (P < .01). For percentage change in cerebral blood volume, there was no significant difference between ACZ (107.51%) and 10% CO(2) (92.95%) challenge. Significant correlations were observed among percentage changes in vascular endothelial growth factor, microvessel density, and cerebral blood volume (P < .01). Percentage change in cerebral blood flow correlated well with vascular endothelial growth factor.

CONCLUSIONS

The results of this study indicate that PCT with ACZ challenge is a more reliable technique compared to 10% CO(2) challenge for the quantitative evaluation of microcirculation in gliomas.

Effect of stenting on cerebral CT perfusion in symptomatic and asymptomatic patients with carotid artery stenosis

BACKGROUND AND PURPOSE

The introduction of CAS has led to increased treatment of both symptomatic and asymptomatic patients with internal carotid stenosis. This study was performed to compare the effect of stent placement on cerebral perfusion in symptomatic and asymptomatic patients using CT perfusion.

MATERIALS AND METHODS

We included 45 patients with carotid artery stenosis of ≥70% who underwent arterial stent placement. Thirty-one patients were treated because of symptoms; 14 asymptomatic patients were treated before coronary artery bypass grafting. Patients underwent CTP before and after stent placement. We calculated MTT, CBV, and CBF, and derived relative numbers that compared treated with untreated hemispheres: ratios of CBV and CBF and difference in MTT. We compared the effect of carotid stent placement on cerebral perfusion in symptomatic and asymptomatic patients.

RESULTS

All perfusion parameters changed significantly after treatment in symptomatic patients: rCBF increased from 0.81 to 0.93 (P < .001), rCBV decreased from 1.02 to 0.95 (P < .05), and dMTT decreased from 1.29 to 0.14 (P < .001). In asymptomatic patients only, rCBF changed significantly with an increase from 0.92 to 1.03 (P < .05). When we compared symptomatic and asymptomatic patients before treatment, rCBF in symptomatic patients was significantly lower. The decrease of rCBV after treatment in symptomatic patients resulted in a significantly lower value than in asymptomatic patients.

CONCLUSIONS

Carotid artery stent placement improves blood flow in the affected hemisphere in symptomatic and asymptomatic patients. CBF before treatment is more strongly impaired in patients with symptomatic carotid stenosis. Compensatory hyperemia on the symptomatic side before treatment (rCBV > 1) turns into hypoxemia after treatment, suggesting impaired autoregulation in these patients.