What are Current Preprocedure Imaging Requirements for Carotid Artery Stenting and Carotid Endarterectomy: Have Magnetic Resonance Angiography and Computed Tomographic Angiography Made a Difference?

Intolerance to occlusion during carotid artery stenting with proximal protection: causes, mechanisms, treatment and prevention

Periprocedural cerebral microembolization is the most important complication of carotid artery stenting. Among several variables that play a role to reduce this risk, brain protection (proximal vs. distal) plays a pivot role. Data are accumulating in favor of a better performance of proximal vs. distal especially in symptomatic patients and high-risk carotid plaques. A prerequisite for the technique to be safe and effective is the presence of a valid intracranial collateral circulation to compensate for the target vessel hemisphere avoiding patient intolerance. This complication may occur either soon after the common carotid balloon occlusion or slowly developing during the procedure peaking at the stent post-dilation step. While Willis' circle anatomic variants are the most frequent cause of acute intolerance, a mix of anatomic, hemodynamic and patient cerebral condition play a role for the late developing form. Prevention is the best treatment of intolerance through a pre- and procedural imaging with different techniques (CT angiography, NMR angiography, transcranial Doppler assessment, digital subtraction angiography and back pressure monitoring).

Safe carotid endarterectomy: "one fits all strategy"

Introduction

Carotid artery stenosis of 50% or more in the extracranial internal carotid artery is responsible for 10–15% of all strokes. Interventional treatment options include carotid endarterectomy and carotid artery stenting, where endarterectomy is proven to be superior.

Aim

In this study, we report the carotid endarterectomy results of patients we operated on using the strategy we termed the “one fits all strategy”.

Material and methods

Seventy-six patients undergoing carotid endarterectomy between July 2016 and April 2020 were retrospectively studied. Conventional endarterectomy under general anesthesia with primary closure of the arteriotomy was performed in all patients. We used a near infrared spectroscopy oximeter to measure regional cerebral oxygenation continuously throughout the surgery.

Results

The mean age of the patients was 70.96 8.15 years. There were 52 male and 24 female patients. The mean follow-up time was 20.6 ±13.6 months. Coronary artery disease was detected in 52 (73.6%) patients. Coronary artery bypass operation was indicated in 19 patients in whom a staged approach was performed in 13 and a reverse staged approach in 1. There were two perioperative strokes one of which recovered fully spontaneously and the other partially with physiotherapy. Eight cases were revised due to hematoma formation.

Conclusions

Carotid endarterectomy continues to prove its safety in carotid artery stenosis patients. Continuous cerebral oxygenation monitoring is indispensable for carotid surgery. Despite discrepancies in surgical techniques, we believe that “one fits all strategy: general anesthesia, conventional endarterectomy without patch plasty, never shunter and always NIRS monitorization” may be used safely in patients undergoing carotid endarterectomy.

The management of carotid restenosis: a comprehensive review

Carotid artery stenosis (CS) is a major medical problem affecting approximately 10% of the general population 80 years or older and causes stroke in approximately 10% of all ischemic events. In patients with symptomatic, moderate-to-severe CS, carotid endarterectomy (CEA) and carotid angioplasty and stenting (CAS), has been used to lower the risk of stroke. In primary CS, CEA was found to be superior to best medical therapy (BMT) according to 3 large randomized controlled trials (RCT). Following CEA and CAS, restenosis remains an unsolved problem involving a large number of patients as the current treatment recommendations are not as clear as those for primary stenosis. Several studies have evaluated the risk of restenosis, reporting an incidence ranging from 5% to 22% after CEA and an in-stent restenosis (ISR) rate ranging from 2.7% to 33%. Treatment and optimal management of this disease process, however, is a matter of ongoing debate, and, given the dearth of level 1evidence for the management of these conditions, the relevant guidelines lack clarity. Moreover, the incidence rates of stroke and complications in patients with carotid stenosis are derived from studies that did not use contemporary techniques and materials. Rapidly changing guidelines, updated techniques, and materials, and modern medical treatments make actual incidence rates barely comparable to previous ones. For these reasons, RCTs are critical for determining whether these patients should be treated with more aggressive treatments additional to BMT and identifying those patients indicated for surgical or endovascular treatments. This review summarizes the current evidence and controversies concerning the risks, causes, current treatment options, and prognoses in patients with restenosis after CEA or CAS.

Systematic review of preoperative carotid duplex ultrasound compared with computed tomography carotid angiography for carotid endarterectomy

INTRODUCTION

We reviewed the literature for preoperative computed tomography carotid angiography and/or carotid duplex to determine their respective sensitivity and specificity in assessing the degree of carotid stenosis. We aimed to identify whether one imaging modality can accurately identify critical stenosis in patients presenting with transient ischaemic attack or symptoms of a cerebrovascular accident requiring carotid endarterectomy.

METHODS

Systematic search of MEDLINE, Embase, Cochrane database of systematic reviews, all Evidence-Based Medicine Reviews (Cochrane Database of Systematic Reviews, ACP Journal club, Database of Abstracts of Reviews of Effects, Cochrane Clinical Answers, Cochrane Controlled Trials Register, Cochrane Methodology Register, Health Technology Assessment and NHS Economic Evaluation Database) for primary studies relating to computed tomography carotid angiography (CTA) and/or carotid duplex ultrasound (CDU). Studies included were published between 1990 and 2018 and focused on practice in the UK, Europe and North America.

RESULTS

The sensitivity and specificity of CTA and CDU are comparable. CDU is safe and readily available in the clinical environment hence its use in the initial preoperative assessment of carotid stenosis. CDU is an adequate imaging modality for determining stenosis greater than 70%; sensitivity and specificity are improved when the criteria for determining greater than 70% stenosis are adjusted. Vascular laboratories opting to use duplex as their sole imaging modality should assess the sensitivity and specificity of their own duplex procedure before altering practice to preoperative single imaging for patients.

CONCLUSIONS

The sensitivity and specificity of CTA (90.6% and 93%, respectively) and CDU (92.3% and 89%, respectively) are comparable. Both are dependent on criteria used in vascular laboratories. CDU sensitivity and specificity was improved to 98.7% and 94.1%, respectively, where peak systolic velocity and end diastolic velocity were assessed. Either modality can be used to determine greater than 70% stenosis, although a secondary imaging modality may be required for cases of greater than 50% stenosis.

Carotid Duplex Ultrasonography: Additional Imaging is Rarely Necessary for Appropriate Treatment Planning for Carotid Artery Disease

This study was conducted to determine the utility of multiple imaging studies (CT angiography, magnetic resonance angiography, and/or conventional angiography), in addition to duplex ultrasonography (DU), in evaluating patients with carotid stenosis. A retrospective case series was conducted of patients with carotid stenosis who underwent DU alone or DU plus additional imaging. Concordance between DU and additional imaging and the effect on treatment plan was evaluated. Two hundred patients with carotid stenosis were evaluated. Sixty-four had DU plus additional imaging. Sixty-two of the patients (96.9%) had no change in treatment due to additional imaging. Only 2 of the 64 patients (3.1%) with additional imaging had a change in treatment plan. In conclusion, additional imaging, beyond DU, is rarely necessary for treatment planning in patients with carotid disease.

Neurosonology and noninvasive imaging of the carotid arteries

In this chapter, we review imaging of the extracranial carotid arteries and the indications for noninvasive carotid artery evaluation, measuring the degree of arterial stenosis and plaque morphology. We also analyze the types of noninvasive imaging, including carotid duplex ultrasound, transcranial Doppler, magnetic resonance angiography, and computer tomography angiography. We look at each of these modalities, briefly discussing techniques, benefits, limitations, and sources of error. Furthermore, we discuss the apparent accuracy and the need for multimodality imaging. Finally, an imaging algorithm for the evaluation of the extracranial carotid arteries is proposed, which is in routine use at our hospital.

Plaque morphology (the PLAC Scale) on CT angiography: predicting long-term anatomical success of primary carotid stenting

OBJECT

Carotid angioplasty and stenting has emerged as an alternative to carotid endarterectomy for the treatment of atherosclerotic carotid stenosis. Primary carotid stenting, performed using self-expanding stents alone without deliberate use of embolic protection devices and balloon angioplasty, has been shown to be effective and faster, cheaper, and potentially safer than conventional techniques. However, the long-term morphological results of this technique have not been established. The aim of this study was to determine whether preprocedural carotid plaque imaging at the site of maximal stenosis by using CT angiography (CTA) could predict the long-term morphological outcome of primary carotid stenting.

METHODS

One hundred eighty-one patients were treated over an 11-year period. Preprocedural CTA was performed in 102 of these. A morphological scale (the Predicting Long-term outcome with Angioplasty of the Carotid artery [PLAC] Scale), with grades from 0 to 4 and A or B, was used to evaluate the circumferential degree of plaque calcification, and the presence or absence of soft plaque. All patients were followed using duplex carotid ultrasound and plain radiographs. Satisfactory morphological outcome was defined as a peak systolic velocity < 120 cm/s and internal carotid artery/common carotid artery ratio < 1.4.

RESULTS

The average follow-up duration was 29.7 months (median 24.5 months, range 0.3–87 months). Univariate logistic regression demonstrated that a low calcification grade (p < 0.001), less thick calcification (p < 0.001), and moderate amounts of soft plaque (p < 0.001) are factors that are highly associated with good long-term outcome. Multivariate analyses confirmed that these factors are independent of each other in predicting outcome.

CONCLUSIONS

The long-term morphological outcome of primary carotid stenting was predicted with considerable accuracy by using a straightforward CTA carotid plaque grading scale.

Balloons in endovascular neurosurgery: history and current applications

The use of balloons in the field of neurosurgery is currently an essential part of our clinical practice. The field has evolved over the last 40 years since Serbinenko used balloons to test the feasibility of occluding cervical vessels for intracranial pathologies. Since that time, indications have expanded to include sacrificing cervical and intracranial vessels with detachable balloons, supporting the coil mass in wide-necked aneurysms (balloon remodeling technique), and performing intracranial and cervical angioplasty for atherosclerotic disease, as well as an adjunct to treat arteriovenous malformations. With the rapid expansion of endovascular technologies, it appears that the indications and uses for balloons will continue to expand. In this article, we review the history of balloons, the initial applications, the types of balloons available, and the current applications available for endovascular neurosurgeons.

Carotid duplex criteria for patients with contralateral occlusion

BACKGROUND

Contralateral occlusion (CLO) occurs in approximately 8% of patients undergoing intervention for carotid artery stenosis. Patients with CLO have increased stroke risk compared with patients without CLO, but standard carotid duplex ultrasonography (CDUS) criteria are not a reliable manner to screen or follow patients with CLO. Because appropriate duplex criteria for these patients are not well understood, this article defines CDUS parameters that accurately predict carotid artery stenosis at our institution.

METHODS

Sixty-five patients with ipsilateral carotid stenosis and CLO were identified from our institutional database. Fifteen of sixty-five patients had arteriography, computed tomography angiography, or magnetic resonance angiography within 6 mo of CDUS. We determined accuracy of our laboratory's criteria for determining stenosis category compared with three-dimensional imaging. Receiver operating characteristic curves were used to determine optimal peak systolic velocity (PSV), end diastolic velocity (EDV), and systolic ratio (SR) cutoff values for diagnosing ≥50% stenosis in this pilot cohort. Finally, the revised criteria were prospectively applied to a validation cohort (n = 8) from the same institution.

RESULTS

Categorization of stenosis by standard PSV, EDV, and SR criteria saw similar accuracy trends in both pilot (46.7, 53.3, and 66.7%) and validation (25, 25, and 62.5%) cohorts. Receiver operating characteristic curve analysis in the pilot cohort identified optimized PSV, EDV, and SR cutoffs (≥250, ≥90, and ≥2.3 cm/s, respectively) for diagnosing ≥50% stenosis. In the pilot cohort, new PSV criteria increased specificity (60%-100%) with minimal decreased sensitivity (90%-80%), whereas new EDV criteria increased specificity (40%-71.4%) and maintained 100% sensitivity. New SR criteria failed to improve sensitivity or specificity above 80%. Similar trends for the new CDUS velocity criteria were observed in the validation cohort.

CONCLUSIONS

Increasingly stringent ultrasound parameters can provide reliable criteria for determining ≥50% carotid stenosis in patients with CLO. Further prospective validation that includes more patients with high-grade ipsilateral stenosis will help identify the role of SR in segregating high-grade versus moderate stenosis in CLO patients.

Patient-specific finite element analysis of carotid artery stenting: a focus on vessel modeling

Finite element analysis is nowadays a well-assessed technique to investigate the impact of stenting on vessel wall and, given the rapid progression of both medical imaging techniques and computational methods, the challenge of using the simulation of carotid artery stenting as procedure planning tool to support the clinical practice can be approached. Within this context, the present study investigates the impact of carotid stent apposition on carotid artery anatomy by means of patient-specific finite element analysis. In particular, we focus on the influence of the vessel constitutive model on the prediction of carotid artery wall tensional state of lumen gain and of vessel straightening. For this purpose, we consider, for a given stent design and CA anatomy, two constitutive models for the CA wall, that is, a hyperelastic isotropic versus a fiber-reinforced hyperelastic anisotropic model. Despite both models producing similar patterns with respect to stress distribution, the anisotropic model predicts a higher vessel straightening and a more evident discontinuity of the lumen area near the stent ends as observed in the clinical practice. Although still affected by several simplifications, the present study can be considered as further step toward a realistic simulation of carotid artery stenting.

[Traumatic dissection of carotid arteries caused by high energy motorcycle accident]

Injuries of internal carotid arteries caused by high energy trauma are rare but often combined with poor outcome. Blunt trauma to the head and neck as well as the use of newer motorcycle helmets together with crash circumstances should promptly lead to a differentiated polytrauma management with expansion of radiologic diagnostics. This could lead to a reduction of overlooked dissections and an increase in promptly and correctly treated injuries.

Lumen morphology in mild-to-moderate internal carotid artery stenosis correlates with neurological symptoms

BACKGROUND

Several prospective studies have shown that carotid endarterectomy can reduce the risk for subsequent ischemic stroke in patients with 70-99% stenosis of the internal carotid artery (ICA). However, its benefits are still controversial in less than 70% stenosis of the ICA. There is increasing evidence that carotid lumen irregularities may correlate with neurological symptoms. Recent development of computed tomography angiography (CTA) can provide adequate information on the carotid plaque morphology. In this study, therefore, we aimed to clarify whether carotid lumen morphology estimated by CTA correlates with neurological symptoms in patients with 30-69% ICA stenosis.

METHODS

This study included 67 carotid stenotic lesions with 30-69% ICA stenosis in 52 consecutive patients. These 67 lesions were examined by CTA from the viewpoints of the degree of stenosis, the prevalence of ulceration, and lumen morphology. Multivariate analysis was performed to detect significant predictors for the occurrence of ipsilateral ischemic events.

RESULTS

Multivariate analysis showed that the irregular shape of the carotid lumen was the most powerful variable to predict symptomatic lesion in 30-69% ICA stenosis.

CONCLUSIONS

These findings suggest that the morphology of carotid plaque may be associated with the occurrence of ipsilateral ischemic events in 30-69% ICA stenosis.

Update on surgical management for asymptomatic carotid stenosis

The management of asymptomatic carotid stenosis has been a topic of considerable debate. In this article, we aim to critically review the recent literature as it pertains to surgical management of asymptomatic carotid stenosis. We will explore the most recent trials looking at advancements in best medical therapy, as well as trials that compare traditional carotid endarterectomy to carotid stenting. In addition, we will review the current literature on surgical technique and perioperative risk management. Overall, our current recommendation is for surgical management of asymptomatic carotid disease for stenoses ≥ 80% in patients who are of reasonable perioperative risk.

Imaging of stroke and transient ischaemic attack

Non-fatal stroke has significant social and financial implications, and the use of appropriate imaging is essential for early diagnosis and treatment to prevent permanent disability. This article discusses the pivotal role radiological imaging plays in the management of stroke and transient ischaemic attack.

Advanced imaging applications for endovascular procedures

Advanced imaging techniques, particularly in CT and MRI, have become state-of-the-art to support the performance of interventional neuroradiologic procedures. Multidetector CT scanners with submillimeter detectors and real-time workstations have allowed the use of a noninvasive study, CT angiography, as a first-line diagnostic study at many institutions to detect and evaluate the morphology of aneurysms. Follow-up for postsubarachnoid spasm now includes transcranial Doppler, CT angiography, and sometimes perfusion to guide therapy. While both intracranial and extracranial stenosis have long been well evaluated by MR and CT angiography, information about the intimal wall and plaque morphology is now possible. In the setting of acute ischemia, CT with perfusion or MR with diffusion and perfusion has increased the ability to separate territory at risk from infarcted tissue, and can help to guide more appropriate intervention. This article addresses current state-of the-art imaging applications as well as a few techniques on the horizon that show great promise in helping to characterize those lesions amenable to endovascular therapy.

Contrast-enhanced MR angiography is not more accurate than unenhanced 2D time-of-flight MR angiography for determining > or = 70% internal carotid artery stenosis

BACKGROUND AND PURPOSE

Internal carotid artery (ICA) atheromatous disease is an important cause of ischemic stroke, and endarterectomy or stent placement is typically indicated for symptomatic patients with > or = 70% stenosis. Our purpose was to compare contrast-enhanced MR angiography (CE-MRA) with unenhanced 2D time-of-flight MR angiography (2D TOF MRA) in detecting hemodynamically significant ICA stenosis, by using CT angiography (CTA) as the reference standard.

MATERIALS AND METHODS

This was an institutional review board-approved retrospective study. We identified 177 consecutive patients (354 ICAs) who received correlative CE-MRA, 2D TOF MRA, and CTA. Two neuroradiologists blinded to the CTA data graded the degree of ICA stenosis according to a 5-point scale. Additionally, luminal signal-intensity characteristics including 1) signal intensity drop-out, 2) distal-vessel narrowing, and 3) distal-vessel signal-intensity reduction were recorded. MRA results were correlated with those of CTA, and receiver-operating-characteristic (ROC) curves were constructed.

RESULTS

On CTA, there were 55 ICAs with and 299 without > or = 70% stenosis. CE-MRA was 84% sensitive and 96% specific for detecting > or = 70% stenosis; 2D TOF MRA was 80% sensitive and 95% specific. The area under the ROC curve was 0.97 for CE-MRA and 0.95 for 2D TOF MRA (P = .51, not significant). For both MRA studies, each of the luminal signal-intensity characteristics had high specificity (> 98%) but poor-to-mild sensitivity (35%-66%) in detecting > or = 70% stenosis.

CONCLUSIONS

Although it is established that CE-MRA more accurately delineates neurovascular anatomy than does unenhanced 2D TOF MRA, the administration of gadolinium did not offer a significant advantage in distinguishing surgically treatable ICA stenosis. This conclusion may be important in patients with contraindications to gadolinium.

Subtraction computed tomographic angiography of calcified arteries: preliminary phantom and clinical studies

RATIONALE AND OBJECTIVES

The technique of subtraction computed tomographic angiography (sCTA) has been proposed for the evaluation of atherosclerotic disease to address limitations in CTA in highly calcified arteries. However, sCTA has not gained acceptance in clinical practice, in part, due to image artifacts caused by patient motion that occur between the acquisition of the two component images. The purpose of this study was to evaluate the effectiveness of computational image co-registration to obtain sCTA.

MATERIALS AND METHODS

The study was conducted using a semi-automated implementation of the mutual information (MI) registration algorithm. The results of sCTA were evaluated quantitatively in a phantom representing a calcified artery. Technical success of sCTA was evaluated in 14 calcified arterial segments in two patients. An observer study was carried out to determine interobserver agreement in the interpretation of sCTA. Qualitative observations were made between sCTA and CTA.

RESULTS

Computation time for performing the co-registration for each 2-cm calcification is less than 1 second. The necessary user interaction required minimal expertise. Measurements of the degree of stenosis in the calcified artery phantom agreed to within 8 +/- 4% of gold-standard measurements. Technical success was demonstrated in all calcifications. Strong interobserver agreement was obtained for the detection of hemodynamically significant stenoses (kappa = 0.86). Several apparent pitfalls in the interpretation of CTA in calcified arteries were noted that could potentially be obviated by sCTA.

CONCLUSIONS

The study supports the use of a straight-forward implementation of the MI algorithm and provides preliminary evidence validating the use of sCTA in the setting of atherosclerotic disease of the lower extremities.

Imaging for neuro-ophthalmic and orbital disease - a review

A literature review was performed by content experts in neuro-ophthalmology and neuroradiology using a systematic English-language Medline search (1994-2008) limited to articles with relevance to neuro-ophthalmic and orbital imaging. The information covered in this review includes: (i) the basic mechanics, indications and contraindications for cranial and orbital computed tomography and magnetic resonance (MR) imaging; (ii) the utility and indications for intravenous contrast, (iii) the use of specific MR sequences; (iv) the techniques and ophthalmic indications for computed tomography/MR angiography and venography; and (v) the techniques and indications for functional MR imaging, positron emission tomography scanning and single photon emission computed tomography. Throughout the review accurate and timely communication with the neuroradiologist regarding the clinical findings and suspected location of lesions is emphasized so as to optimize the ordering and interpretation of imaging studies for the ophthalmologist.