Retrograde aortic blood flow as a mechanism of stroke: MR evaluation of the prevalence in a population-based study
Retrograde blood flow from complex atheroma in the descending aorta (DAo) has only recently been described as a potential mechanism of stroke. However, prevalence of this mechanism in the general population and the exact factors influencing stroke risk are unclear.
One hundred twenty-six consecutively recruited inhabitants of Freiburg, Germany, between 20 and 80 years of age prospectively underwent 3-T MRI. Aortic plaque location and thickness were determined by 3D T1 MRI (1 mm3). 4D flow MRI (spatial/temporal resolution 2 mm3/20 ms) and dedicated software were used to determine prevalence and extent of flow reversal and potential embolization from DAo plaques. Flow was correlated with baseline characteristics and echocardiographic and MRI parameters (aortic diameter, wall thickness, and pulse wave velocity).
The maximum length of retrograde blood flow connecting the DAo with the left subclavian artery (LSA) increased from 16.1 ± 8.3 mm in 20–29-year-old to 24.7 ± 11.7 mm in 70–80-year-old subjects, correlated with age (r = 0.37; p < 0.001), and was lower in females (p = 0.003). Age was the only independent predictor of increased flow reversal. Complex DAo plaques ≥ 4-mm thickness were found in eight subjects (6.3%) and were connected with the LSA, left common carotid artery, and brachiocephalic trunk in 8 (100%), 1 (12.5%), and 0 (0%) cases, respectively.
Retrograde blood flow from the DAo was very frequent. However, potential retrograde embolization was rare due to the low incidence of complex DAo plaques. The magnitude of flow reversal and prevalence of complex atheroma increased with age. Thus, older patients with aortic atherosclerosis are especially vulnerable to this stroke mechanism.
• 4D flow MRI allows in vivo visualization and quantification of individual and three-dimensional blood flow patterns within the thoracic aorta including retrograde components.
• This population-based study showed that blood flow reversal from the proximal descending aorta to the brain-supplying great arteries is very frequent and able to reach all brain territories. The extent of such flow reversal increases with age and with the extent of aortic atherosclerosis.
• The combination of blood flow reversal with plaque rupture in the proximal descending aorta constitutes a potential stroke mechanism that should be considered in future trials and in the management of stroke patients in clinical routine.
KeywordsMagnetic resonance imaging Angiography Atherosclerosis Embolism Thoracic aorta
Left common carotid artery
Generalized autocalibrating partial parallel acquisition
Left subclavian artery
Parallel MRI with extended and averaged GRAPPA kernels
Pulse wave velocity
The authors thank Adriana Komancsek for performing MRI examinations and Dr. Konrad Whittaker for proof reading of the manuscript.
Prof. Dr. Andreas Harloff received funding from Deutsche Forschungsgemeinschaft (DFG), Bonn, Germany, grant no. HA5399/3-1.
Compliance with ethical standards
The scientific guarantor of this publication is Prof. Dr. Andreas Harloff.
Conflict of interest
The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.
Statistics and biometry
One of the authors, Prof. Dr. Werner Vach, has significant statistical expertise and performed statistical analysis.
Written informed consent was obtained from all subjects in this study.
Institutional Review Board approval was obtained.
Study subjects or cohorts overlap
Data from this population-based study were analyzed and published. In these three articles, aortic pulse wave velocity, hemodynamics of the right heart, and hemodynamics of the pulmonary arteries were investigated.
Accordingly, there is only minimal overlap with the submitted paper focussing on the extent of retrograde blood flow and potential retrograde embolization from the descending aorta:
Harloff A, Mirzaee H, Lodemann T, Hagenlocher P, Wehrum T, Stuplich J, Hennemuth A, Hennig J, Grundmann S, Vach W. Determination of aortic stiffness using 4D flow cardiovascular magnetic resonance - a population-based study. J Cardiovasc Magn Reson. 2018 Jun 21;20(1):43.
Wehrum T, Lodemann T, Hagenlocher P, Stuplich J, Ngo BTT, Grundmann S, Hennemuth A, Hennig J, Harloff A. Age-related changes of right atrial morphology and inflow pattern assessed using 4D flow cardiovascular magnetic resonance: results of a population-based study. J Cardiovasc Magn Reson. 2018 Jun 14;20(1):38.
Wehrum T, Hagenlocher P, Lodemann T, Vach W, Dragonu I, Hennemuth A, von Zur Mühlen C, Stuplich J, Ngo BT, Harloff A. Age dependence of pulmonary artery blood flow measured by 4D flow cardiovascular magnetic resonance: results of a population-based study. J Cardiovasc Magn Reson. 2016 May 31;18(1):31.
• cross-sectional study/observational
• performed at one institution
- 13.Lang RM, Bierig M, Devereux RB et al (2005) Recommendations for chamber quantification: a report from the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr 18:1440–1463Google Scholar
- 17.Tautz L, Chitiboi T, Hennemuth A (2015) Automatic perfusion analysis using phase-based registration and object-based image analysis. In: Camara O, Mansi T, Pop M, Rhode K, Sermesant M, Young A (eds) Statistical Atlases and Computational Models of the Heart - Imaging and Modelling Challenges. STACOM 2014. Lecture Notes in Computer Science, vol 8896. Springer, ChamGoogle Scholar
- 18.Hennemuth A, Friman O, Schumann C et al (2011) Fast interactive exploration of 4D MRI flow data. Proc. SPIE 7964, Medical Imaging 2011: Visualization, Image-Guided Procedures, and Modeling, 79640E. https://doi.org/10.1117/12.878202
- 21.Harloff A, Schlachetzki F (2018) Rivaroxaban for stroke prevention after embolic stroke of undetermined source. N Engl J Med 379:986–987Google Scholar