Associations Between Carotid Plaque Characteristics and Improvement of Cerebral Blood Perfusion in Patients With Moderate to Severe Carotid Stenosis Undergoing Carotid Endarterectomy

Application of high-resolution MRI in evaluating statin efficacy on symptomatic intracranial atherosclerosis

OBJECTIVES

To investigate the efficacy of statins on symptomatic intracranial atherosclerotic plaques using high-resolution 3.0 T MR vessel wall imaging (HR-MRI).

METHODS

Patients with symptomatic intracranial atherosclerotic plaques (cerebral ischemic events within the last three months) confirmed by HR-MRI from July 2017 to August 2022 were retrospectively included in this study. The enrolled patients started statin therapy at baseline. All the patients underwent the follow-up HR-MRI examination after statin therapy for at least 3 months. A paired sample t-test and Wilcoxon rank sum test were used to evaluate the changes in plaque characteristics after statin therapy. Multivariate linear regression was further used to investigate the clinical factors associated with statin efficacy.

RESULTS

A total of 48 patients (37 males; overall mean age = 60.2 ± 11.7 years) were included in this study. The follow-up time was 7.0 (5.6-12.0) months. In patients treated with statins for > 6 months (n = 31), plaque length, wall thickness, plaque burden, luminal stenosis and plaque enhancement were significantly reduced. Similar results were found in patients with good lipid control (n = 21). Younger age, lower BMI and hypertension were associated with decreased plaque burden. Lower BMI, hypertension and longer duration of statin therapy were associated with decreased plaque enhancement. Younger age and hypertension were associated with decreased luminal stenosis (all p < 0.05).

CONCLUSION

HR-MRI can effectively evaluate plaques changes after statin therapy. Statins can reduce plaque burden and stabilize plaques. The effect of statin may have a relationship with age, BMI, hypertension, and duration of statin therapy.

CLINICAL RELEVANCE STATEMENT

High-resolution MRI can be applied to evaluate the efficacy of statins on symptomatic intracranial atherosclerotic plaques. Long-term statin use and well-controlled blood lipid levels can help reduce plaque burden and stabilize plaques.

KEY POINTS

High-resolution MRI provides great help evaluating the changes of plaque characteristics after statin therapy. Efficacy of statins is associated with duration of use, controlled lipid levels, and clinical factors. High-resolution MRI can serve as an effective method for following-up symptomatic intracranial atherosclerosis.

Investigating the Association of Carotid Atherosclerotic Plaque MRI Features and Silent Stroke After Carotid Endarterectomy

BACKGROUND

The predictive value of carotid plaque characteristics for silent stroke (SS) after carotid endarterectomy (CEA) is unclear.

OBJECTIVE

To investigate the associations between carotid plaque characteristics and postoperative SS in patients undergoing CEA.

STUDY TYPE

Prospective.

POPULATION

One hundred fifty-three patients (mean age: 65.4 ± 7.9 years; 126 males) with unilateral moderate-to-severe carotid stenosis (evaluated by CT angiography) referred for CEA.

FIELD STRENGTH/SEQUENCE

3 T, brain-MRI:T2-PROPELLER, T1-/T2-FLAIR, diffusion weighted imaging (DWI) and T2*, carotid-MRI:black-blood T1-/T2W, 3D TOF, Simultaneous Non-contrast Angiography intraplaque hemorrhage.

ASSESSMENT

Patients underwent carotid-MRI within 1-week before CEA, and brain-MRI within 48-hours pre-/post-CEA. The presence and size (volume, maximum-area-percentage) of carotid lipid-rich necrotic core (LRNC), intraplaque hemorrhage (Type-I/Type-II IPH) and calcification were evaluated on carotid-MR images. Postoperative SS was assessed from pre-/post-CEA brain DWI. Patients were divided into moderate-carotid-stenosis (50%-69%) and severe-carotid-stenosis (70%-99%) groups and the associations between carotid plaque characteristics and SS were analyzed.

STATISTICAL TESTS

Independent t test, Mann-Whitney U-test, chi-square test and logistic regressions (OR: odds ratio, CI: confidence interval). P value <0.05 was considered statistically significant.

RESULTS

SS was found in 8 (16.3%) of the 49 patients with moderate-carotid-stenosis and 21 (20.2%) of the 104 patients with severe-carotid-stenosis. In patients with severe-carotid-stenosis, those with SS had significantly higher IPH (66.7% vs. 39.8%) and Type-I IPH (66.7% vs. 38.6%) than those without. The presence of IPH (OR 3.030, 95% CI 1.106-8.305) and Type-I IPH (OR 3.187, 95% CI 1.162-8.745) was significantly associated with SS. After adjustment, the associations of SS with presence of IPH (OR 3.294, 95% CI 1.122-9.669) and Type-I IPH (OR 3.633, 95% CI 1.216-10.859) remained significant. Moreover, the volume of Type-II IPH (OR 1.014, 95% CI 1.001-1.028), and maximum-area-percentage of Type-II IPH (OR 1.070, 95% CI 1.002-1.142) and LRNC (OR 1.030, 95% CI 1.000-1.061) were significantly associated with SS after adjustment. No significant (P range: 0.203-0.980) associations were found between carotid plaque characteristics and SS in patients with moderate-carotid-stenosis.

DATA CONCLUSIONS

In patients with unilateral severe-carotid-stenosis, carotid vulnerable plaque MR features, particularly presence and size of IPH, might be effective predictors for SS after CEA.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 2.

The Relation of the Iron Metabolism Index to the Vulnerability Index of Carotid Plaque with Different Degrees of Stenosis

OBJECTIVE

To investigate the differences in serum iron index and iron metabolizing protein expression in plaques in patients with different degrees of carotid artery stenosis and the relationship with plaque traits.

METHODS

A total of 100 patients eligible for carotid endarterectomy (CEA) from August 2021 to February 2022 were included. Patients completed a computed tomography (CTA) scan for patient grouping and a magnetic resonance imaging (MRI) for precise quantification of carotid plaque traits within 1 week prior to surgery. Clinical indicators associated with the progression of carotid stenosis to occlusion were analyzed using ordered logistic regression. Twenty carotid plaques were analyzed immunohistochemically to investigate the relationship between plaque traits and the iron metabolism indexes.

RESULTS

No significant correlation between high serum ferritin (SF), unsaturated iron binding capacity (UIBC) and progression of carotid stenosis (OR 1.100, 95% CI 0.004-0.165, p = 0.039; OR 1.050, 95% CI 0.005-0.094, p = 0.031). SF and serum transferrin receptor (sTfR) were correlated with normalized wall index (NWI) (R = 0.470, p = 0.036; R = 0.449, p = 0.046), and the results of multiple linear regression suggested that SF and sTfR remained associated with NWI (R = 0.630, R2 = 0.397, Adjusted R2 = 0.326, p = 0.014). In plaques, H-type ferritin (H-FT) was correlated with NWI and lipid-rich necrotic core (LRNC) volume (R = 0.502, p = 0.028; R = 0.468, p = 0.043). Transferrin receptor 1 (TfR1) was correlated with LRNC volume and intraplaque hemorrhage (IPH) volume (R = 0.538, p = 0.017; R = 0.707, p = 0.001).

CONCLUSIONS

There were statistical differences in the expression of iron metabolism proteins in carotid plaques with different degrees of stenosis. Serum iron metabolism index (SF and sTfR) and expression of iron metabolizing proteins (H-FT and TfR1) in plaques were positively correlated with carotid plaque vulnerability index (NWI, LRNC volume).

MRI Detection of Carotid Intraplaque Hemorrhage and Postintervention Cognition

BACKGROUND AND PURPOSE

Cognitive improvement has been reported after carotid revascularization and attributed to treating stenosis and correcting hypoperfusion. This study investigated the effect of carotid intraplaque hemorrhage on postintervention cognition.

MATERIALS AND METHODS

In this institutional review board-approved single-center study, consecutive patients scheduled for carotid surgery were recruited for preoperative carotid MR imaging (MPRAGE) and pre- and postintervention cognitive testing using the Repeatable Battery for the Assessment of Neuropsychological Status. Pre- and postintervention scores were compared using t tests and multivariable linear regression.

RESULTS

Twenty-three participants were included, with endarterectomy performed in 20 (87%) and angioplasty/stent placement, in 3 (13%). Overall, statistically significant improvements occurred in the pre- versus postintervention mean Total Scale score (92.1 [SD, 15.5] versus 96.1 [SD, 15.8], P = .04), immediate memory index (89.4 [SD, 18.2] versus 97.7 [SD, 14.9], P < .001), and verbal index (96.1 [SD, 14.1] versus 103.0 [SD, 12.0], P = .002). Intraplaque hemorrhage (+) participants (n = 11) had no significant improvement in any category, and the attention index significantly decreased (99.4 [SD, 18.0] versus 93.5 [SD, 19.4], P = .045). Intraplaque hemorrhage (-) participants (n = 12) significantly improved in the Total Scale score (86.4 [SD, 11.8] versus 95.5 [SD, 12.4], P = .004), immediate memory index (82.3 [SD, 14.6] versus 96.2 [SD, 14.1], P = .002), delayed memory index (94.3 [SD, 14.9] versus 102.4 [SD, 8.0], P = .03), and verbal index (94.3 [SD, 13.2] versus 101.5 [SD, 107.4], P = .009). Postintervention minus preintervention scores for intraplaque hemorrhage (+) versus (-) groups showed statistically significant differences in the Total Scale score (-0.4 [SD, 6.8] versus 8.0 [SD, 8.5], P = .02), attention index (-5.9 [SD, 8.5] versus 4.3 [SD, 11.9], P = .03), and immediate memory index (4.2 [SD, 6.7] versus 12.2 [SD, 10.2], P = .04).

CONCLUSIONS

Cognitive improvement was observed after carotid intervention, and this was attributable to intraplaque hemorrhage (-) plaque. MR imaging detection of intraplaque hemorrhage status may be an important determinant of cognitive change after intervention.

Slice-based and time-specific hemodynamic measurements discriminate carotid artery vulnerable atherosclerotic plaques

BACKGROUND AND OBJECTIVE

Hemodynamic patterns play key roles in progression of carotid vulnerable plaques. However, most of previous studies utilized maximum or averaged value of hemodynamic measurements which is not an ideal representative of hemodynamic patterns. This study aimed to investigate the association of slice-based and time-specific hemodynamic measurements with carotid vulnerable plaque using magnetic resonance (MR) vessel wall imaging and histology.

METHODS

Thirty-two patients (mean age: 63.9±8.1 years; 25 males) with carotid atherosclerotic stenosis (≥50% stenosis) referred to carotid endarterectomy were recruited and underwent MR vessel wall imaging. Carotid plaque burden was evaluated on MR images and vulnerable plaque features including calcification, lipid-rich necrotic core, and intra-plaque hemorrhage (IPH) were identified by histology. The slice-based and time-specific hemodynamic measurements were extracted from computational fluid dynamics simulation of 3D carotid arterial model. Correlation coefficients between hemodynamic measurements and carotid plaque features were calculated and the logistic regressions with generalized estimating equation (GEE) were conducted. The value in discriminating carotid vulnerable plaque features was determined by receiver-operating-characteristic analysis.

RESULTS

Of 102 MR-histology matched slices from 32 patients, time-averaged wall shear stress (TAWSS) (r=0.263, p=0.008), oscillatory shear index (OSI) (r=-0.374, p<0.001), and peakWSS (r=0.232, p=0.019) were significantly associated with carotid IPH. The logistic regression with GEE revealed that peakWSS (OR, 1.206; 95% CI, 1.026-1.418; p, 0.023) and TAWSS (OR, 0.364, 95% CI, 0.138-0.959; p, 0.041) were significantly associated with presence of IPH after adjusting for age and BMI. In discriminating carotid IPH, the AUC of TAWSS, OSI, combined TAWSS with maximum wall thickness (MWT) and combined OSI with MWT was 0.656, 0.722, 0.761, and 0.764, respectively.

CONCLUSIONS

Slice-based and time-specific hemodynamic characteristics could effectively discriminate carotid IPH. Combination of hemodynamic measurements with carotid plaque burden might be a stronger indicator for carotid vulnerable plaque features than each measurement alone.

Associations Between Carotid Plaque Characteristics and Perioperative Cerebral Blood Flow Determined by Arterial Spin Labeling Imaging in Patients With Moderate-to-Severe Stenosis Undergoing Carotid Endarterectomy

Purpose

To examine the associations between carotid plaque characteristics and perioperative cerebral blood flow (CBF) by arterial spin labeling (ASL) imaging.

Materials and Methods

Patients with unilateral moderate-to-severe carotid stenosis referred for carotid endarterectomy (CEA) were recruited and underwent carotid vessel wall and brain ASL magnetic resonance imaging. The following imaging features were measured: relative CBF (rCBF = CBF_{index−hemisphere}/CBF_{contralateral−hemisphere}) in the middle cerebral artery territory; plaque burden and the presence of lipid-rich necrotic core; intraplaque hemorrhage (IPH); calcification; ulcer and fibrous-cap rupture; and the volume and maximum plaque components' area percentages. The associations between plaque characteristics and perioperative CBF were analyzed.

Results

Sixty-one patients (mean age, 66.6 ± 7.8 years; 55 males) were included. Univariate linear regression showed that rCBF_pre−CEA was associated with stenosis [β, −0.462; 95% confidence interval (CI), from −0.797 to −0.126; p = 0.008], calcification (β, 0.103; 95% CI, 0.005–0.201; p = 0.040), maximum IPH area percentage (β, −0.127; 95% CI, from −0.223 to −0.030; p = 0.012), and ulcer (β, 0.069; 95% CI, 0.025–0.113; p = 0.005); rCBF_post−CEA was associated with the IPH volume (β, −0.060; 95% CI, from −0.107 to −0.014; p = 0.013). After adjusting for the confounding factors, the associations of calcification with rCBF_pre−CEA (β, 0.099; 95% CI, from 0.004 to −0.194; p = 0.042) and IPH volume with rCBF_post−CEA (β, −0.060; 95% CI, from −0.109 to −0.011; p = 0.020) remained statistically significant, while those of rCBF_pre−CEA with maximum IPH area percentage (β, −0.089; 95% CI, from −0.188 to 0.011; p = 0.080) and ulcer (β, 0.050; 95% CI, from −0.012 to 0.112; p = 0.100) did not remain statistically significant.

Conclusion

The compositional characteristics of carotid atherosclerotic plaques, particularly IPH, were associated with perioperative CBF in patients with unilateral moderate-to-severe carotid stenosis undergoing CEA. Our findings indicated that the patients with larger carotid IPH could expect smaller improvement in CBF following CEA.