Identifying cardiovascular risk factors that impact cerebrovascular reactivity: An ASL MRI study

BACKGROUND

To maintain cerebral blood flow (CBF), cerebral blood vessels dilate and contract in response to blood supply through cerebrovascular reactivity (CR).

PURPOSE

Cardiovascular (CV) disease is associated with increased stroke risk, but which risk factors specifically impact CR is unknown.

STUDY TYPE

Prospective longitudinal.

SUBJECTS

Fifty-three subjects undergoing carotid endarterectomy or stenting.

FIELD STRENGTH/SEQUENCE

3T, 3D pseudo-continuous arterial spin labeling (PCASL) ASL, and T₁ 3D fast spoiled gradient echo (FSPGR).

ASSESSMENT

We evaluated group differences in CBF changes for multiple cardiovascular risk factors in patients undergoing carotid revascularization surgery.

STATISTICAL TESTS

PRE (baseline), POST (48-hour postop), and 6MO (6 months postop) whole-brain CBF measurements, as 129 CBF maps from 53 subjects were modeled as within-subject analysis of variance (ANOVA). To identify CV risk factors associated with CBF change, the CBF change from PRE to POST, POST to 6MO, and PRE to 6MO were modeled as multiple linear regression with each CV risk factor as an independent variable. Statistical models were performed controlling for age on a voxel-by-voxel basis using SPM8. Significant clusters were reported if familywise error (FWE)-corrected cluster-level was P < 0.05, while the voxel-level significance threshold was set for P < 0.001.

RESULTS

The entire group showed significant (cluster-level P < 0.001) CBF increase from PRE to POST, decrease from POST to 6MO, and no significant difference (all voxels with P > 0.001) from PRE to 6MO. Of multiple CV risk factors evaluated, only elevated systolic blood pressure (SBP, P = 0.001), chronic renal insufficiency (CRI, P = 0.026), and history of prior stroke (CVA, P < 0.001) predicted lower increases in CBF PRE to POST. Over POST to 6MO, obesity predicted lower (P > 0.001) and cholesterol greater CBF decrease (P > 0.001).

DATA CONCLUSION

The CV risk factors of higher SBP, CRI, CVA, BMI, and cholesterol may indicate altered CR, and may warrant different stroke risk mitigation and special consideration for CBF change evaluation.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2020;51:734-747.

Convergence Analysis of Micro-Lesions (CAML): An approach to mapping of diffuse lesions from carotid revascularization

Carotid revascularization (endarterectomy, stenting) prevents stroke; however, procedure-related embolization is common and results in small brain lesions easily identified by diffusion weighted magnetic resonance imaging (DWI). A crucial barrier to understanding the clinical significance of these lesions has been the lack of a statistical approach to identify vulnerable brain areas. The problem is that the lesions are small, numerous, and non-overlapping. Here we address this problem with a new method, the Convergence Analysis of Micro-Lesions (CAML) technique, an extension of the Anatomic Likelihood Analysis (ALE). The method combines manual lesion tracing, constraints based on known lesion patterns, and convergence analysis to represent regions vulnerable to lesions as probabilistic brain atlases. Two studies were conducted over the course of 12 years in an active, vascular surgery clinic. An analysis in an initial group of 126 patients at 1.5 T MRI was cross-validated in a second group of 80 patients at 3T MRI. In CAML, lesions were manually defined and center points identified. Brains were aligned according to side of surgery since this factor powerfully determines lesion distribution. A convergence based analysis, was performed on each of these groups. Results indicated the most consistent region of vulnerability was in motor and premotor cortex regions. Smaller regions common to both groups included the dorsolateral prefrontal cortex and medial parietal regions. Vulnerability of motor cortex is consistent with previous work showing changes in hand dexterity associated with these procedures. The consistency of CAML also demonstrates the feasibility of this new approach to characterize small, diffuse, non-overlapping lesions in patients with multifocal pathologies.

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Convergence Analysis of Micro-Lesions technique finds patterns in diffuse lesions.

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Lesions from carotid revascularization affect consistent brain targets.

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Motor cortex is the most vulnerable brain region to these lesions.

Volume of subclinical embolic infarct correlates to long-term cognitive changes after carotid revascularization

OBJECTIVE

Carotid intervention is safe and effective in stroke prevention in appropriately selected patients. Despite minimal neurologic complications, procedure-related subclinical microemboli are common and their cognitive effects are largely unknown. In this prospective longitudinal study, we sought to determine long-term cognitive effects of embolic infarcts.

METHODS

The study recruited 119 patients including 46% symptomatic patients who underwent carotid revascularization. Neuropsychological testing was administered preoperatively and at 1 month, 6 months, and 12 months postoperatively. Rey Auditory Verbal Learning Test (RAVLT) was the primary cognitive measure with parallel forms to avoid practice effect. All patients also received 3T brain magnetic resonance imaging with a diffusion-weighted imaging (DWI) sequence preoperatively and within 48 hours postoperatively to identify procedure-related new embolic lesions. Each DWI lesion was manually traced and input into a neuroimaging program to define volume. Embolic infarct volumes were correlated with cognitive measures. Regression models were used to identify relationships between infarct volumes and cognitive measures.

RESULTS

A total of 587 DWI lesions were identified on 3T magnetic resonance imaging in 81.7% of carotid artery stenting (CAS) and 36.4% of carotid endarterectomy patients with a total volume of 29,327 mm³. Among them, 54 DWI lesions were found in carotid endarterectomy patients and 533 in the CAS patients. Four patients had transient postoperative neurologic symptoms and one had a stroke. CAS was an independent predictor of embolic infarction (odds ratio, 6.6 [2.1-20.4]; P < .01) and infarct volume (P = .004). Diabetes and contralateral carotid severe stenosis or occlusion had a trend of positive association with infarct volume, whereas systolic blood pressure ≥140 mm Hg had a negative association (P = .1, .09, and .1, respectively). There was a trend of improved RAVLT scores overall after carotid revascularization. Significantly higher infarct volumes were observed among those with RAVLT decline. Within the CAS cohort, infarct volume was negatively correlated with short- and long-term RAVLT changes (P < .05).

CONCLUSIONS

Cognitive assessment of procedure-related subclinical microemboli is challenging. Volumes of embolic infarct correlate with long-term cognitive changes, suggesting that microembolization should be considered a surrogate measure for carotid disease management.

Eotaxin Augments Calcification in Vascular Smooth Muscle Cells

Calcification of atherosclerotic plaques in elderly patients represents a potent risk marker of cardiovascular events. Plasma analyses of patients with or without calcified plaques reveal significant differences in chemokines, particularly eotaxin, which escalates with increased calcification. We therefore, hypothesize that eotaxin in circulation augments calcification of vascular smooth muscle cells (VSMCs) possibly via oxidative stress in the vasculature. We observe that eotaxin increases the rate of calcification significantly in VSMCs as evidenced by increased alkaline phosphatase activity, calcium deposition, and osteogenic marker expression. In addition, eotaxin promotes proliferation in VSMCs and triggers oxidative stress in a NADPH oxidase dependent manner. These primary novel observations support our proposition that in the vasculature eotaxin augments mineralization. Our findings suggest that eotaxin may represent a potential therapeutic target for prevention of cardiovascular complications in the elderly. J. Cell. Biochem. 118: 647-654, 2017. © 2016 Wiley Periodicals, Inc.

Microembolization is associated with transient cognitive decline in patients undergoing carotid interventions

OBJECTIVE

Carotid interventions are important in helping to reduce the risk of stroke for patients with high-grade carotid artery stenosis; however, subclinical cerebral microemboli can occur during these procedures. Associations have been found between the incidence of microemboli and postoperative decline in memory. We therefore sought to determine whether this decline persisted long-term and to assess changes in other cognitive domains.

METHODS

Patients were prospectively recruited under an Institutional Review Board-approved protocol at a single academic center. Neuropsychological testing was administered preoperatively and at 1-month and 6-month intervals postoperatively. Cognitive domains that were evaluated included verbal memory, visual memory, psychomotor speed, dexterity, and executive function. Diffusion-weighted magnetic resonance imaging sequencing was performed preoperatively and ≤48 hours postoperatively to identify procedure-related microemboli. Univariate and multivariate regression models were used to identify relationships among microembolization, demographics, and cognition.

RESULTS

Included were 80 male patients with an average age of 69 years. Forty patients underwent carotid artery stenting and 40 underwent carotid endarterectomy. Comorbidities included diabetes in 45%, coronary artery disease in 50%, and prior neurologic symptoms in 41%. New postoperative microemboli were found in 45 patients (56%). Microembolization was significantly more common in the carotid artery stenting cohort (P < .005). Univariate analysis demonstrated that patients with procedurally related embolization showed decline 1 month postoperatively in verbal memory and Trail Making A measures. Multivariate analysis demonstrated that procedurally related embolization (odds ratio [OR], 2.8; P = .04) and preoperative symptomatic stenosis (OR, 3.2; P = .026) were independent predictors of decline for the Rey Auditory Verbal Learning Test Short Delay measure at 1 month. At 6 months, no significant relationship was found between emboli and decline on Rey Auditory Verbal Learning Test Short Delay, but age (OR, 1.1, P = .005) and chronic obstructive pulmonary disease (OR, 7.1, P = .018) were significantly associated with decline at 6 months after the intervention.

CONCLUSIONS

Microembolization that is associated with carotid artery intervention predicts short-term cognitive decline. However, some of these cognitive deficits persist at 6 months after the intervention, and further investigation is warranted to determine individual patient risk factors that may affect recovery.

Genetic Polymorphisms Influence Cognition in Patients Undergoing Carotid Interventions

While carotid interventions help decrease the risk of stroke, nearly 40% of patients experience cognitive deterioration. Genetic polymorphism in apolipoprotein E (ApoE) and brain-derived neurotrophic factor (BDNF) have been implicated in cognitive impairment; however, it is unclear whether they may influence cognitive changes in patients undergoing carotid intervention. In this study, we seek to assess the role of genetic polymorphisms in carotid intervention-related cognitive change. Polymorphisms related to cognitive function were chosen for this preliminary analysis. Over 2 years, patients undergoing carotid interventions were prospectively recruited. Patients underwent neuropsychological testing 2 weeks prior to and at 1 month following their procedure. Saliva samples were collected for genetic analysis. Logistic regressions were used to identify associations between polymorphisms and cognitive measures. A total of 91 patients were included; all were male with an average age of 70 years. The majority of patients exhibited hypertension (95%) and a history of smoking (81%). Presence of ApoE 4 allele was associated with depression (p= 0.047). After correcting for age and genetic polymorphisms in BDNF and serotonin transporter (5-HTT), ApoE 4 allele was associated with depression (p= 0.044) and showed a trend with baseline cognitive impairment (p= 0.10). Age ≥ 70 years was associated with baseline cognitive impairment after adjusting for the three genetic polymorphisms (p= 0.03). Patients with ApoE 4 and BDNF A polymorphisms performed less well on the visual and verbal memory measures, respectively. Polymorphisms in ApoE and BDNF may provide insight on cognition in patients undergoing carotid interventions; however, the mechanism of this relationship remains unclear.

Brain structural connectivity distinguishes patients at risk for cognitive decline after carotid interventions

While brain connectivity analyses have been demonstrated to identify ill patients for a number of diseases, their ability to predict cognitive impairment after brain injury is not well established. Traditional post brain injury models, such as stroke, are limited for this evaluation because pre-injury brain connectivity patterns are infrequently available. Patients with severe carotid stenosis, in contrast, often undergo non-emergent revascularization surgery, allowing the collection of pre and post-operative imaging, may experience brain insult due to perioperative thrombotic/embolic infarcts or hypoperfusion, and can suffer post-operative cognitive decline. We hypothesized that a distributed function such as memory would be more resilient in patients with brains demonstrating higher degrees of modularity. To test this hypothesis, we analyzed preoperative structural connectivity graphs (using T1 and DWI MRI) for 34 patients that underwent carotid intervention, and evaluated differences in graph metrics using the Brain Connectivity Toolbox. We found that patients with lower binary component number, binary community number and weighted community number prior to surgery were at greater risk for developing cognitive decline. These findings highlight the promise of brain connectivity analyses to predict cognitive decline following brain injury and serve as a clinical decision support tool. Hum Brain Mapp 37:2185-2194, 2016. © 2016 Wiley Periodicals, Inc.

SPY technology as an adjunctive measure for lower extremity perfusion

OBJECTIVE

Lack of a reliable outcome measure often leads to excessive or insufficient interventions for critical limb ischemia (CLI). SPY technology (Novadaq Technologies Inc, Bonita Springs, Fla), widely adapted by plastic and general surgeons, uses laser-assisted fluorescence angiography (LAFA) to assess tissue perfusion. We sought to determine the role of SPY as an alternative, perhaps more reliable outcome measure for vascular interventions.

METHODS

All patients undergoing elective or urgent revascularization for claudication and CLI were prospectively recruited from June 2012 to August 2014. LAFA using SPY technology was performed before and after revascularization procedures under a standard Institutional Review Board-approved protocol. Quantitative measures of perfusion at plantar surfaces were analyzed and compared with ankle-brachial index.

RESULTS

A total of 93 patients with claudication or CLI underwent LAFA before and after a revascularization procedure in the study period. The mean preoperative ankle-brachial index increased from 0.60 to 0.84 (P < .001) after a revascularization procedure. Plantar perfusion as measured by LAFA also improved significantly after intervention. Ingress, defined as the rate at which fluorescence intensity increases on the plantar surface during LAFA, increased from 7.1 to 12.4 units/s (P < .001). Peak perfusion, defined as the difference between the baseline and the peak of fluorescence intensity, increased from 97.1 and 143.9 units (P < .001). Egress, defined as the rate at which intensity diminishes after reaching peak perfusion, increased from 1.0 to 1.9 units/s (P = .035). Procedure-related digital embolization was also observed in several patients despite lack of an angiographic finding.

CONCLUSIONS

This is the largest prospective study evaluating SPY technology in peripheral vascular interventions. Our study shows that SPY is a valuable tool in visualizing real-time procedural outcomes and providing additionally useful information on regional tissue perfusion. Further investigation is warranted to standardize outpatient use and to determine threshold values that predict wound healing.

Utilization of Intravascular Ultrasound during Carotid Artery Stenting

For patients at high risk for surgery, carotid artery stenting (CAS) is a viable alternative to help reduce risk of stroke for patients with high-grade carotid artery stenosis; however, a higher incidence of perioperative stroke has been observed in patients undergoing stenting compared to those undergoing open surgery. Intravascular ultrasound (IVUS) is commonly used during coronary artery procedures to help evaluate lesions and to guide stent placement. Multiple groups have sought to determine whether IVUS could also be used during CAS. While IVUS has been shown to be both feasible and safe during CAS, there is limited evidence that demonstrates direct improvement in procedural outcomes. Further studies focusing on clinical outcomes should be conducted in order to justify routine use of this technology during CAS.

Abstract 301: Resistin is an Independent Indicator of Inflammation in Patients Undergoing Carotid Interventions

Objective: Resistin has been associated with increased risk for cardiovascular complications. However, the underlying mechanisms are not yet fully elucidated. This study aimed to investigate whether resistin modulated plasma cytokines, chemokines, and growth factors in patients undergoing carotid revascularization procedures.

Methods: Patients undergoing carotid artery stenting (CAS) and carotid endarterectomy (CEA) at a single institution were recruited to participate. Blood plasma collection was performed within 48 hours following intervention using an established protocol, and demographics were recorded. Samples were stored at -80 °C and analyzed with a Luminex magnetic beads-based assay. Patients were divided into tertiles based on plasma resistin concentration (mean pg/mL): low (2237.6, n=30), medium (4252.3, n=31), and high (7467.5, n=30). Levels of cytokines were compared using ANOVA.

Results: 91 male patients with a mean age of 69 years were included (50 CAS, 41 CEA). Most patients had a history of smoking (84%). Medical comorbidities included hypertension (93%), diabetes (45%), CAD (49%), and obesity (44%). The distribution of comorbidities was similar within each tertile. The levels of resistin were not significantly different in CAS vs CEA patients. There was also no significant difference in various growth factors (VEGF-A, M-CSF, and GM-CSF), neurotrophic factors (BDNF and β-NGF), or adhesion molecules (ICAM-1 and VCAM-1). However, significantly higher levels of the pro-inflammatory cytokines/chemokines were observed in the high resistin tertile compared to the low tertile: TNF-α (p < 0.001), IL-6 (p < 0.05), IL-12p40 (p < 0.01), IL-12p70 (p < 0.05), MIP-1α (p < 0.05), MIP-1β (p < 0.05), and MCP-3 (p < 0.01). Similarly, significantly higher levels of the aforementioned pro-inflammatory cytokines (except MCP-3) were observed in the high compared to the medium tertile.

Conclusions: Patients with higher resistin levels exhibit higher levels of inflammatory profiles post-intervention independent of procedure type or comorbidities, implicating that resistin-induced inflammation may be a mechanism for resistin-related vascular complications.

A prospective evaluation of using IVUS during percutaneous superficial femoral artery interventions

BACKGROUND

The outcomes of endovascular interventions of the superficial femoral artery (SFA) are variable. Completion angiography is typically performed to confirm satisfactory outcomes after SFA angioplasty and/or stenting. However, two-dimensional angiography may not accurately reflect the extent of residual stenosis. We sought to determine whether intravascular ultrasound (IVUS) can help with residual disease assessment and procedure outcome.

METHODS

Patients with anticipated SFA disease were prospectively recruited to the study. Patients with primary SFA disease on diagnostic angiography were included. After SFA endovascular intervention with angioplasty and/or stenting, a completion angiogram was performed to confirm satisfactory results before IVUS evaluation. IVUS-detected maximal residual stenosis, maximal residual lesion volume, and number of nonconsecutive posttreatment SFA segments with >50% residual stenosis were evaluated. Periprocedural ankle-brachial indexes (ABIs), Short Form 36 (SF-36) surveys, and Walking Impairment Questionnaires were also collected.

RESULTS

Fifty-nine patients were prospectively enrolled. Thirty-three received angioplasty only, and 26 received angioplasty and stenting. All patients were men, mean age was 67 years, and major comorbidities included coronary artery disease (53%), active smoking (56%), hypertension (88%), and diabetes (68%). The angioplasty-only cohort had more nonconsecutive areas of >50% residual stenosis (P = 0.004), greater residual stenosis (P = 0.03), and smaller minimal lumen diameters after treatment (P = 0.01) than the angioplasty and stenting cohort. However, there was no significant difference in ABI between the 2 groups and no difference in ABI improvement after intervention. Sixty-four percent of all patients demonstrated a >0.2 increase in postintervention ABI. Improvement in ABI at 1 month after procedure significantly correlated with postintervention SF-36 survey physical scores (r = 0.435, P = 0.007).

CONCLUSIONS

IVUS evaluation provides more-accurate intraprocedural insight on the extent of residual stenosis after SFA interventions. Future studies are warranted to determine whether IVUS-guided postangioplasty and/or stenting can impact long-term interventional outcome.

Abstract 129: Predicting Patients Who Will Have Cognitive Decline After Carotid Endarterectomy or Stenting Using Structural Connectivity Graph Analysis

Objectives: Many CEA and CAS patients experience postoperative neurocognitive decline. We sought to apply structural connectivity metrics to identify patients at increased risk for postoperative decline based solely on preoperative imaging.

Methods: Under an IRB approved protocol 28 patients underwent presurgical T1 structural and 30 direction diffusion tensor imaging (DTI) MRI and neuropsychological tests before and 1 month after surgery. Patients with decline showed decreased performance on the Rey-AVLT on 1 month follow up. The T1 images were processed using FreeSurfer 5.3, with resulting segmentations reviewed and edited as needed under neuroradiologist supervision. Whole brain tractography was performed using Diffusion Toolkit and visually inspected. Connectivity matrices were then generated, and graph metrics were computed using the Brain Connectivity Toolbox.

Results: Controlling for age, classifiers using the graph analysis metrics “weighted optimal community structure” & “binary component sizes” were able to identify patients that would experience cognitive decline with 81% sensitivity 83% and specificity (p<.05, false discovery rate .05). These two measures were computed at 10 proportion edge thresholds from .1 to 1 at intervals of .1 in weighted and binary networks respectively.

Conclusions: Applying preoperative structural connectivity analysis in CEA and CAS patients may identify patients at increased risk for postoperative cognitive decline, and in so doing may help risk stratify patients and guide them to preventive interventions.

Abstract 125: Inflammatory Markers Influence Microembolization in Patients Undergoing Carotid Interventions

INTRODUCTION: Despite the use of embolic protection and improvement in surgical technique for carotid interventions, perioperative cerebral microembolization is still relatively common. Susceptibility to microembolization is largely uncontrolled and the effects remain poorly understood. We hypothesized that inflammation may play a role in this process and sought to identify plasma markers predicting embolization in patients undergoing carotid interventions.

METHODS: Patients scheduled for carotid interventions at an academic center were prospectively recruited to the study. MRI with diffusion-weighted imaging (DWI) was performed prior to and within 48 hours following the procedure and used to identify new cerebral microemboli. Blood samples were collected at the time of intervention prior to carotid interrogation (Pre) and at 24 hours following intervention (Post). Plasma was isolated and analyzed by a 27-plex Luminex assay. The assay was performed in triplicate and Significance Analysis of Microarrays (SAM) identified significant inflammatory markers. Mann-Whitney U tests were performed to further evaluate these findings.

RESULTS: 71 male patients were included with an average age of 70 years; 38 underwent CAS and 33 underwent CEA. 59% of the cohort exhibited postoperative DWI lesions. Post plasma samples were collected for all patients, and Pre samples were collected for a cohort of 19 patients. We observed significantly lower levels of several cytokines in patients with procedure-related DWI lesions, particularly platelet-derived growth factor (PDGF) (150.8 vs 389.6pg/ml, p<.001). Patients with more complex plaques were also observed to have lower levels of PDGF. For the cohort with both Pre and Post samples, there was a significantly greater decrease in PDGF for patients with DWI lesions compared to those who did not. (U=382, Z=-2.6, p=.008).

CONCLUSIONS: Lower plasma levels of cytokines were observed in patients with procedure-related DWI lesions, suggesting that patients who illicit an inappropriate immune response may be more susceptible to procedure-related microembolization. Impaired PDGF response may indicate poor repair mechanism to injury. Further investigation is warranted.

Contralateral microemboli following carotid artery stenting in patients with a contralateral internal carotid artery occlusion

Subclinical microembolization identified on diffusion-weighted magnetic resonance imaging is recognized as an important outcome measure for carotid revascularization procedures. It is generally believed that arch manipulation is the primary reason for developing microemboli in the contralateral hemisphere during carotid artery stenting. However, we identified three patients who developed postprocedure microemboli of the contralateral hemisphere despite a known chronic contralateral internal carotid artery occlusion. Our cases highlight that ipsilateral microemboli may be an underappreciated but an important source of contralateral lesions through patent intracranial collateral pathways.

Abstract 507: Genetic Correlates of Cognitive Change in Patients Undergoing Carotid Interventions

OBJECTIVES

Carotid interventions have been shown to decrease stroke risk and improve cerebral perfusion. However, nearly 40% of patients who undergo carotid revascularization procedures experience cognitive deterioration. We have demonstrated that subclinical microembolization is associated with memory decline, but whether genetic factors plays a role in post-procedural cognitive change is unclear. We herein seek to assess genetic determinants as potential risk factors for these procedures.

METHODS

Over one year period, patients undergoing carotid interventions at a single academic institution were recruited to participate. Patients underwent neuropsychological testing two weeks prior to and at one month following their procedure and MRI prior to and within 48 hours following their procedure. Saliva samples were collected for genetic testing and demographics were recorded. Logistic regressions were used to search for associations.

RESULTS

34 patients were included (18 CAS, 16 CEA); all were male with a mean age of 68. The majority of patients exhibit hypertension (94%) and have a history of smoking (76%). Other co-morbidities included diabetes (47%), obesity (35%), and CAD (44%). Consistent with previous findings, CAS was associated with higher incidence of microemboli (p=.0005) and with susceptibility to memory decline (p=.0085). Negative univariate associations were found for 5-HTT (serotonin transporter) short alleles with memory decline (p=.016) and brain-derived neurotrophic factor (BDNF) polymorphism with incidence of microemboli (p=.018). After adjusting for apolipoprotein E (ApoE) risk alleles, incidence of microemboli trended with memory decline (p=.099).

CONCLUSIONS

Despite a small number of patients, our study showed that genetic polymorphisms such as 5-HTT, BDNF, and ApoE may provide additional insight on post-operative changes in cognition. Further investigation of these polymorphisms is warranted to understand and potentially prevent cognitive deterioration following carotid revascularization procedures.

Prospective neurocognitive evaluation of patients undergoing carotid interventions

OBJECTIVE

Distal cerebral embolization is a known complication of carotid interventions. We prospectively investigated whether subclinical microembolization seen on postoperative magnetic resonance imaging (MRI) leads to cognitive deficits in patients undergoing carotid revascularization procedures.

METHODS

Patients undergoing carotid interventions and eligible for MRI scanning were recruited. Among 247 patients who received preoperative and postoperative MRI evaluations, 51 also completed neuropsychologic testing before and at 1 month after their procedure. Cognitive evaluation included the Rey Auditory Verbal Learning Test (RAVLT) for memory evaluation and the Mini-Mental State Examination (MMSE) for general cognitive impairment screening.

RESULTS

The 51 patients (all men), comprising 16 with carotid artery stenting (CAS) and 35 with carotid endarterectomy (CEA), were a mean age of 71 years (range, 54-89 years). Among them, 27 patients (53%) were symptomatic preoperatively, including 11 who had prior stroke and 16 who had prior preoperative transient ischemic attack symptoms. Most patients had significant medical comorbidities, including hypertension (96%), diabetes (31.3%), coronary artery disease (47%), and chronic obstructive pulmonary disease (15.7%). Two patients (4%) had prior ipsilateral CEA and eight had contralateral carotid occlusion (15.7%). Memory decline evident on RAVLT was identified in eight CAS patients and 13 CEA patients. Eleven patients had evidence of procedure-related microemboli. Although there was no significant difference in baseline cognitive function or memory change between the CEA and CAS cohorts, the CAS cohort had a significantly higher incidence of microembolic lesions. Multivariate regression analysis showed that procedure-related microembolization was associated with memory decline (P = .016) as evident by change in RAVLT. A history of neurologic symptoms was significantly associated with poor baseline cognitive function (MMSE; P = .03) and overall cognitive deterioration (change in MMSE; P = .026), as determined by Wilcoxon rank sum test and linear regression analysis, respectively.

CONCLUSIONS

Although CEA and CAS are effective in stroke prevention, with minimal neurologic complication, neurocognitive effects remain uncertain. Procedure-associated microembolization and pre-existing neurologic symptoms are associated with poor baseline cognitive function and memory decline after the procedures. Further comprehensive cognitive evaluation to determine the benefit of carotid interventions is warranted.

Abstract 125: Intravascular Ultrasound: A Clinically Useful Tool for Carotid Plaque Characterization

OBJECTIVE: Virtual Histology Intravascular Ultrasound (VH™ IVUS) is valuable for estimating minimal lumen diameter (MLD) and plaque characterization. The clinical use of IVUS in the carotid arteries is not well characterized. To evaluate carotid plaque morphology, we performed VH™ IVUS in patients with known carotid artery stenosis.

METHODS: From July 2010, patients were prospectively enrolled in an IRB approved study to undergo IVUS prior to an elective carotid stenting procedure. Hospital records were reviewed for co-morbidities, carotid/arch anatomy, preoperative carotid duplex velocity measurements, and incidence of postoperative microemboli. Comparison of pre- and postoperative diffusion-weighted MR images was used to identify microemboli. IVUS-derived MLD and vessel wall plaque characteristics were collected. Spearman correlation was performed between MLD and duplex estimated stenosis, and between plaque characteristics and frequency of postoperative microemboli.

RESULTS: 14 patients were enrolled during the study period with carotid artery stenosis (average ICA/CCA ratio 5.5, 64.3% asymptomatic). Major co-morbidities included hyperlipidemia (79%), diabetes (71%), and angina (43%). 57% of patients had type 1 arches, and 50% of patients had heavily calcified irregular carotid plaques. MLD correlated with preoperative duplex ICA/CCA ratio (R2=-0.56,p=0.05), and carotid plaque area correlated with peak systolic and diastolic velocities (R2=-0.55,p=0.05). Although microembolic frequency did not correlate with preoperative patient characteristics, it correlated with IVUS-derived plaque necrotic core area (R2=0.53,p=0.05).

CONCLUSION: We demonstrate that periprocedural carotid IVUS is clinically feasible and useful. Preoperative duplex measurements correlated with IVUS MLD confirming the fidelity of the technique. Moreover carotid IVUS demonstrates that patients with necrotic plaque cores have a higher frequency of postoperative microemboli. These findings suggest that carotid IVUS may be helpful to identify patients who are at higher risk of microemboli during carotid artery stenting.