Turbulence Intensity as an Indicator for Ischemic Stroke in the Carotid Web

Carotid web catheter angiography hemodynamic parameters

BACKGROUND

Carotid web (CaW)-related contrast stagnation on digital subtraction angiography (DSA) may be a marker supporting the pathophysiological theory of stasis and thrombosis/embolization. We aim to assess the correlation between DSA hemodynamic parameters with CT angiography (CTA) structural measurements and clinical characteristics.

METHODS

Cross-sectional analysis of consecutive patients with CaW who underwent CTA+DSA. DSA-derived hemodynamic parameters were calculated based on a region of interest at the carotid bulb (time-density curves; TDC). The correlation between duration of contrast stagnation with CaW structural features and with clinical characteristics was evaluated with a mixed effects model.

RESULTS

Sixty patients of mean±SD age 52.2±10.3 years were included, of whom 38 (63.3%) were women, 51 (85%) were black, and 59 (98.3%) had symptomatic lesions. The median CaW base was 2.46 mm (range 1.95-3.76), length 2.7 mm (range 2.15-3.96), thickness (length/base) 1.05 (IQR 0.81-1.36), caudal angle 31.93° (IQR 22.35-43.58), mean±SD distal angle 66.91±15.84°, pocket area 1.62 mm² (0.96-1.62), and pocket perimeter 6.03±2.6 mm. The TDC consistently showed an initial fast decay from the peak concentration followed by a plateau with a negative exponential pattern. The median stagnation time from peak density to 80% contrast clearance was 2.91 s (range 1.81-4.94). No significant associations were observed between the stagnation time and CaW CTA structural measurements (length/base/thickness, caudal and cranial angles web surface angles, web pocket area/perimeter) or clinical characteristics.

CONCLUSIONS

A negative exponential pattern in the DSA contrast clearance of the CaW pocket was observed. There were no morphological or clinical features clearly associated with the duration of contrast stagnation on DSA. The hemodynamic disruption caused by CaW and its thrombotic risk may not be appropriately measured by contrast stagnation time.

Subjects with carotid webs demonstrate pro-thrombotic hemodynamics compared to subjects with carotid atherosclerosis

Carotid artery webs (CaW) are non-atherosclerotic projections into the vascular lumen and have been linked to up to one-third of cryptogenic strokes in younger patients. Determining how CaW affects local hemodynamics is essential for understanding clot formation and stroke risk. Computational fluid dynamics simulations were used to investigate patient-specific hemodynamics in carotid artery bifurcations with CaW, bifurcations with atherosclerotic lesions having a similar degree of lumen narrowing, and with healthy carotid bifurcations. Simulations were conducted using segmented computed tomography angiography geometries with inlet boundary conditions extracted from 2D phase contrast MRI scans. The study included carotid bifurcations with CaW (n = 13), mild atherosclerosis (n = 7), and healthy bifurcation geometries (n = 6). Hemodynamic parameters associated with vascular dysfunction and clot formation, including shear rate, oscillatory shear index (OSI), low velocity, and flow stasis were calculated and compared between the subject groups. Patients with CaW had significantly larger regions containing low shear rate, high OSI, low velocity, and flow stasis in comparison to subjects with mild atherosclerosis or normal bifurcations. These abnormal hemodynamic metrics in patients with CaW are associated with clot formation and vascular dysfunction and suggest that hemodynamic assessment may be a tool to assess stroke risk in these patients.

The differences between carotid web and carotid web with plaque: based on multimodal ultrasonic and clinical characteristics

OBJECTIVE

This study aimed to examine the clinical and multimodal ultrasonic characteristics differences between carotid web (CW) and CW with plaque as well as the potential risk factors for stroke caused by CW.

METHODS

We retrospectively enrolled patients diagnosed with CW by CTA or high-resolution MRI (HRMRI) and simultaneously underwent contrast enhanced ultrasound (CEUS) and superb microvascular imaging examinations from January 2015 to October 2022. The CW angle was measured using computer-aided software. The variations between CW and CW with plaque were evaluated, and univariable and multivariable logistic regressions were utilized to identify possible risk predictors for stroke caused by CW.

RESULTS

Two hundred ninety-nine patients with an average age of 60.85 (± 8.77) years were included. Sex, age, history of smoking, alcohol, hypertension, diabetes mellitus, homocysteine level, and treatment, as well as web length and thickness, luminal stenosis, location wall, number, CW angle, and CEUS enhancement, were quite different among CW and CW with plaque patients (p < 0.05). The logistic regression analysis showed that web length was an independent predictor of luminal stenosis in CW patients. For patients with CW and plaque, plaque and web thickness, as well as plaque enhancement, were associated with stenosis. Furthermore, luminal stenosis and plaque length were risk factors for symptoms.

CONCLUSION

The multimodal ultrasonic and clinical manifestations of CW and CW with plaque are quite different. Web length is an independent risk factor for carotid artery stenosis in CW patients, whereas luminal stenosis and plaque length were risk factors for symptoms in CW with plaque patients.

CRITICAL RELEVANCE STATEMENT

Exploring the similarities and differences between the carotid web and the carotid web with plaque, based on the stereo-geometric spatial position relationship and hemodynamic changes, may provide further insights into the underlying mechanisms of stroke occurrence caused by the carotid web.

KEY POINTS

1. Multimodal ultrasonic and clinical manifestations of carotid web and carotid web with plaque are substantially different. 2. A thin triangular endoluminal defect is identified as a typical feature of the web on superb microvascular imaging, and two kinds of typical ultrasonic features of CW with plaque are also identified. 3. Web length is an independent risk factor for carotid stenosis in carotid web patients, whereas luminal stenosis and plaque length are risk factors for symptoms in patients with CW and plaque.

Use of Carotid Web Angioarchitecture for Stroke Risk Assessment

OBJECTIVE

To examine the usefulness of carotid web (CW), carotid bifurcation and their combined angioarchitectural measurements in assessing stroke risk.

METHODS

Anatomic data on the internal carotid artery (ICA), common carotid artery (CCA), and the CW were gathered as part of a retrospective study from symptomatic (stroke) and asymptomatic (nonstroke) patients with CW. We built a model of stroke risk using principal-component analysis, Firth regression trained with 5-fold cross-validation, and heuristic binary cutoffs based on the Minimal Description Length principle.

RESULTS

The study included 22 patients, with a mean age of 55.9 ± 12.8 years; 72.9% were female. Eleven patients experienced an ischemic stroke. The first 2 principal components distinguished between patients with stroke and patients without stroke. The model showed that ICA-pouch tip angle (P = 0.036), CCA-pouch tip angle (P = 0.036), ICA web-pouch angle (P = 0.036), and CCA web-pouch angle (P = 0.036) are the most important features associated with stroke risk. Conversely, CCA and ICA anatomy (diameter and angle) were not found to be risk factors.

CONCLUSIONS

This pilot study shows that using data from computed tomography angiography, carotid bifurcation, and CW angioarchitecture may be used to assess stroke risk, allowing physicians to tailor care for each patient according to risk stratification.

Impact on hemodynamics in carotid arteries with carotid webs at different locations: A Numerical Study Integrating Thrombus Growth Model

OBJECTIVE

Carotid webs (CWs), lesions in the carotid arteries, are gaining research interest due to the unclear link to ischemic stroke. Similarity to atherosclerosis in lesion location adds the complexity. The main purpose of study is to investigate the hemodynamic effects of CWs at different locations in carotid arteries.

METHODS

Three types of models with CWs were reconstructed from the CTA dataset of 8 healthy carotid arteries (Models A: CWs at the common carotid artery; B: at the origin of internal carotid artery; C: at the carotid sinus). Wall shear stress (WSS)-based parameters, including time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and endothelial cell activation potential (ECAP) were analyzed. A thrombus growth model was also incorporated to assess long-term thrombus formation across different carotid webs locations.

RESULTS

Models A exhibited helical flow, whereas models B and C showed disturbed flow in the carotid sinus. Recirculation in Models A and B was mainly downstream of CWs, while Models C had both upstream and downstream recirculation. In addition, models A had higher overall TAWSS levels, with the smallest region of TAWSS < 0.4 pa (7.78 ± 8.35%). In contrast, Models C had larger areas with TAWSS < 0.4 pa, RRT > 100, and ECAP > 1.5, accounting for 14.18 ± 5.28%, 1.51 ± 1.17%, and 10.36 ± 4.10%, respectively. Noting that thrombus volume was highest in Models C (7.20 ± 3.95%).

CONCLUSIONS

Numerical simulations indicate that: 1) CWs have less hemodynamic impact when located in the CCA, but may increase flow resistance leading to distal branch ischemia; 2) CWs contribute to thrombus formation, primarily downstream in the common carotid artery and internal carotid artery origin, and both upstream and downstream in the sinus; 3) CWs at the origin of the ICA are more likely to result in disturbed blood flow patterns and thrombus aggregation than the other two locations, which may increase the risk of ischemic stroke in distal cerebral arteries.

Recurrent stroke shortly after mechanical thrombectomy secondary to carotid web: A case report

RATIONALE

Carotid web, a known source of thrombus for embolic stroke, presents a considerable risk of stroke recurrence. While case reports have demonstrated the safety and effectiveness of mechanical thrombectomy in treating carotid web-related stroke, the need for concurrent carotid artery stenting to prevent recurrent stroke immediately after thrombectomy remains unclear. This study aims to underscore the importance of immediate carotid artery stenting in preventing recurrent stroke following mechanical thrombectomy in patients with carotid web-related stroke.

PATIENT CONCERNS

A 43-year-old woman with acute onset of left limb weakness and slurred speech within 3 hours was admitted to the emergency department.

DIAGNOSES

Computed tomographic angiography confirmed the M1 segment occlusion of the right middle cerebral artery.

INTERVENTIONS

The patient received intravenous thrombolysis in the local hospital and mechanical thrombectomy in our stroke center.

OUTCOMES

Three days post-mechanical thrombectomy, there was a sudden exacerbation of her neurological deficit symptoms. A reexamination via computed tomographic angiography revealed a re-occlusion in M1 segment of the right middle cerebral artery, despite the implementation of stringent anticoagulation therapy for carotid web-related stroke.

LESSONS

Stroke patients with carotid web had a high risk of stroke recurrence and it was necessary to conduct carotid artery stenting to prevent stroke recurrence secondary to the carotid web immediately after mechanical thrombectomy.

New asymptomatic thrombosis caused by carotid web during the acute period of cerebral infarction

BACKGROUND

At present, the carotid web (CaW) as an important cause of cryptogenic ischemic stroke has gradually received clinical attention. CaW is associated with a high risk of stroke and patient is more likely to have recurrent stroke if the CaW is untreated. We report a patient who developed CaW related thrombosis during the acute period of cerebral infarction.

CASE PRESENTATION

A 49-year-old male patient with CaW in the left internal carotid artery was diagnosed by computed tomography angiography (CTA) and had two cerebral infarctions in two years. Within 72 h after thrombolysis for an acute cerebral infarction, acute thrombosis was identified between the web and the posterior wall of the carotid artery on carotid ultrasound. Emergent carotid endarterectomy (CEA) was performed to remove abnormal CaW structures and thrombosis to prevent stroke. The patient recovered well and was asymptomatic at 2 months follow-up.

CONCLUSION

Carotid web related thromboembolism is a rare cause of stroke. Carotid ultrasound plays an important role in the diagnosis of asymptomatic thrombosis caused by carotid web. Carotid endarterectomy is effective for stroke prevention in patient with carotid web related thrombosis.

Optimization of 4D Flow MRI Spatial and Temporal Resolution for Examining Complex Hemodynamics in the Carotid Artery Bifurcation

BACKGROUND

Three-dimensional, ECG-gated, time-resolved, three-directional, velocity-encoded phase-contrast MRI (4D flow MRI) has been applied extensively to measure blood velocity in great vessels but has been much less used in diseased carotid arteries. Carotid artery webs (CaW) are non-inflammatory intraluminal shelf-like projections into the internal carotid artery (ICA) bulb that are associated with complex flow and cryptogenic stroke.

PURPOSE

Optimize 4D flow MRI for measuring the velocity field of complex flow in the carotid artery bifurcation model that contains a CaW.

METHODS

A 3D printed phantom model created from computed tomography angiography (CTA) of a subject with CaW was placed in a pulsatile flow loop within the MRI scanner. 4D Flow MRI images of the phantom were acquired with five different spatial resolutions (0.50-2.00  mm3) and four different temporal resolutions (23-96 ms) and compared to a computational fluid dynamics (CFD) solution of the flow field as a reference. We examined four planes perpendicular to the vessel centerline, one in the common carotid artery (CCA) and three in the internal carotid artery (ICA) where complex flow was expected. At these four planes pixel-by-pixel velocity values, flow, and time average wall shear stress (TAWSS) were compared between 4D flow MRI and CFD.

HYPOTHESIS

An optimized 4D flow MRI protocol will provide a good correlation with CFD velocity and TAWSS values in areas of complex flow within a clinically feasible scan time (~ 10 min).

RESULTS

Spatial resolution affected the velocity values, time average flow, and TAWSS measurements. Qualitatively, a spatial resolution of 0.50  mm3 resulted in higher noise, while a lower spatial resolution of 1.50-2.00  mm3 did not adequately resolve the velocity profile. Isotropic spatial resolutions of 0.50-1.00  mm3 showed no significant difference in total flow compared to CFD. Pixel-by-pixel velocity correlation coefficients between 4D flow MRI and CFD were > 0.75 for 0.50-1.00  mm3 but were < 0.5 for 1.50 and 2.00  mm3. Regional TAWSS values determined from 4D flow MRI were generally lower than CFD and decreased at lower spatial resolutions (larger pixel sizes). TAWSS differences between 4D flow and CFD were not statistically significant at spatial resolutions of 0.50-1.00  mm3 but were different at 1.50 and 2.00 mm3. Differences in temporal resolution only affected the flow values when temporal resolution was > 48.4 ms; temporal resolution did not affect TAWSS values.

CONCLUSION

A spatial resolution of 0.74-1.00  mm3 and a temporal resolution of 23-48 ms (1-2 k-space segments) provides a 4D flow MRI protocol capable of imaging velocity and TAWSS in regions of complex flow within the carotid bifurcation at a clinically acceptable scan time.

Hemodynamic evaluation of endarterectomy and stenting treatments for carotid web

BACKGROUND AND PURPOSE

A carotid web is a thin, shelf-like luminal protrusion in the internal carotid artery that might cause carotid stenosis and stroke by inducing disturbed flow patterns, thrombosis, and abnormal biomechanical stimulus to the endothelial cells. This study simulated and evaluated how the two main treatments (endarterectomy and stenting) influence hemodynamic environments in the carotid artery and distal carotid siphon arteries, aiming to provide more references for the selection of clinical treatment.

MATERIALS AND METHODS

The carotid web, endarterectomy, and stenting models were reconstructed based on CT images. The blood flow simulations were conducted, and critical parameters related to thrombosis formation and artery remodeling, including swirling strength, wall shear stress (WSS), vortex Q-criterion, and oscillating shear index (OSI), were analyzed.

RESULTS

In the model of the carotid web, obvious recirculation formed distal to the web, accompanied by lower velocity, lower WSS, higher relative resident time (RRT), and higher Q value. While in both two treatment models, the velocity increased and the Q value and RRT decreased at the carotid bifurcation. In addition, both treatments provide more kinetic energy to the distal carotid siphon artery, especially the stenting model.

CONCLUSION

The carotid web can significantly influence the flow environments in the carotid artery. Both endarterectomy and stenting treatments could significantly diminish the side effects of the web and are feasible choices for web patients in terms of hemodynamics. Besides, the treatments for the carotid web would also influence the flow patterns at the distal carotid siphon, especially for the stenting treatment. But more innovational designs are needed to make the minimally invasive stenting treatment more beneficial.