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Investigation of Aortic Wall Thickness, Stiffness and Flow Reversal in Patients With Cryptogenic Stroke: A 4D Flow
Kelly Jarvis1, Gilles Soulat1, Michael Scott1,2
1Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
Insights
Aortic stiffness and flow reversal are linked to cryptogenic stroke. This study used 4D flow MRI to show that increased aortic stiffness and flow reversal in the descending aorta may contribute to stroke in some patients.
Area of Science:
- Cardiovascular Imaging
- Neurology
- Biomedical Engineering
Background:
- Undetermined stroke etiology affects 1/6 to 1/3 of patients.
- Aortic flow reversal and descending aorta (DAo) plaques are potential retrograde embolic mechanisms.
- Investigating aortic characteristics in cryptogenic stroke is crucial for understanding embolism.
Purpose of the Study:
- To assess relationships between aortic stiffness, wall thickness, and flow reversal in cryptogenic stroke patients.
- To compare these parameters between patients with cryptogenic stroke and healthy controls.
- To elucidate the role of aortic properties in retrograde embolism.
Main Methods:
- Prospective study involving 21 cryptogenic stroke patients with DAo plaques and control groups.
- Utilized 1.5T 4D flow MRI for 3D flow dynamics and pulse wave velocity (PWV) quantification.
- Employed 3D dark blood MRI for aortic wall thickness assessment and flow reversal fraction (FRF) mapping.
Main Results:
- Patients showed statistically higher aortic PWV and FRF compared to younger controls.
- Maximum aortic wall thickness was significantly greater in patients than in both control groups.
- Positive correlations were observed between PWV, age, aortic wall thickness, and FRF across all subjects.
Conclusions:
- 4D flow MRI effectively evaluates aortic PWV and flow reversal.
- Findings support the hypothesis that aortic stiffness contributes to retrograde embolic mechanisms in stroke.
- Aortic stiffness and flow reversal are implicated in the pathophysiology of cryptogenic stroke.
Background:
Stroke etiology is undetermined in approximately one-sixth to one-third of patients. The presence of aortic flow reversal and plaques in the descending aorta (DAo) has been identified as a potential retrograde embolic mechanism.
Purpose:
To assess the relationships between aortic stiffness, wall thickness, and flow reversal in patients with cryptogenic stroke and healthy controls.
Study Type:
Prospective.
Population:
Twenty one patients with cryptogenic stroke and proven DAo plaques (69 ± 9 years, 43% female), 18 age-matched controls (age: 65 ± 8 years, 61% female), and 14 younger controls (36 ± 9 years, 57% female).
Field Strength/Sequence:
1.5T; 4D flow MRI and 3D dark blood T1 -weighted turbo spin echo MRI of the aorta.
Assessment:
Noncontrast aortic 4D flow MRI to measure 3D flow dynamics and 3D dark blood aortic wall MRI to assess wall thickness. 4D flow MRI analysis included automated quantification of aortic stiffness by pulse wave velocity (PWV) and voxelwise mapping of the flow reversal fraction (FRF).
Statistical Tests:
Analysis of variance (ANOVA) or Kruskal-Wallis tests, Student's unpaired t-tests or Wilcoxon rank-sum tests, regression analysis.
Results:
Aortic PWV and FRF were statistically higher in patients (8.9 ± 1.7 m/s, 18.4 ± 7.7%) than younger controls (5.3 ± 0.8 m/s, P < 0.0167; 8.5 ± 2.9%, P < 0.0167), but not age-matched controls (8.2 ± 1.6 m/s, P = 0.22; 15.6 ± 5.8%, P = 0.22). Maximum aortic wall thickness was higher in patients (3.1 ± 0.7 mm) than younger controls (2.2 ± 0.2 mm, P < 0.0167) and age-matched controls (2.7 ± 0.5 mm) (P < 0.0167). For all subjects, positive relationships were found between PWV and age (R2 = 0.71, P < 0.05), aortic wall thickness (R2 = 0.20, P < 0.05), and FRF (R2 = 0.47, P < 0.05). Patients demonstrated relationships between PWV and FRF in the ascending aorta (R2 = 0.32, P < 0.05) and arch (R2 = 0.24, P < 0.05).
Data Conclusion:
This study showed the utility of 4D flow MRI for evaluating aortic PWV and voxelwise flow reversal. Positive relationships between aortic PWV, wall thickness, and flow reversal support the hypothesis that aortic stiffness is involved in this retrograde embolic mechanism.
Level Of Evidence:
2 TECHNICAL EFFICACY STAGE: 1.
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