Na Han1, Chuang Wu1, Laiyang Ma1, Yurong Ma1, Jing Zhang1, and Kai Ai2
1Department of Magnetic Resonance, Lanzhou University Second Hospital, Lanzhou, China, 2Philips Healthcare, Xi'an, China
Synopsis
The
multi-parameter analysis of 4D flow MRI can identify the changes of hemodynamic
parameters in different anatomical location of intracranial arteries. This
study evaluating the hemodynamic changes (volume, velocity, wall shear stress)
in the intracranial arteries of young secondary hypertensive patients among
different anatomical locations (ICA-C3, ICA-C7, proximal MCA, proximal PCA, middle
BA) using 4D flow MRI. The proximal PCA had significantly lower volume,
velocity and wall shear stress than the values determined for other locations. The
wall shear stress at the anatomical location of ICA-C3 was decreased in young secondary
hypertensive patients.
Introduction
Cardiovascular disease is a serious disease
that can cause more than 18 million deaths each year. Hypertension is a
recognized risk factor for cardiovascular disease. Recent epidemiological
studies have shown that the incidence of young people is gradually increasing. 4D
flow MRI can provide a series of hemodynamic parameters: wall shear Stress
(WSS), pressure difference, vortex flow energy, velocity and volume, etc. At
present, the research of 4D flow MRI technology in intracranial vascular
disease mainly focuses on intracranial aneurysms and arteriovenous
malformations (AVM). We used 4D flow MRI to evaluate hemodynamic changes
(volume, velocity, WSS) in the intracranial arteries of young secondary
hypertensive patients among different anatomical locations.Methods
Twenty-three
young secondary hypertensive patients aged 20-45 years and twenty-three
age-matched healthy volunteers were enrolled in this study. 4D flow MRI examinations
were performed for each subject. All subjects were scanned using a 3.0 T MR
scanner (Ingenia CX, Philips Healthcare, the Netherlands) with a 32 channel head
coil. The 4D flow MRI was acquired using a volumetric and a time-resolved PC method.
The scanning parameters were as follows: FOV, 20×20×10cm;
reconstruction resolution, acquired isotropic spatial resolution=1mm3;
velocity encoding, 80cm/s; TR/TE, 5.6/2.9ms; flip angle, 8°;20 phases. The
total scan time of the 4D flow took approximately 12−15 minutes depending on
the heart rate of each subject. The 4D flow datasets were imported into the CVI-42
platform (Version 5.6.6, Circle Cardiovascular Imaging, Canada) for further
analysis. As displayed in Fig.1a and b, we placed nine planes in the intracranial
arteries (ICA-C3-R, ICA-C3-L, ICA-C7-R, ICA-C7-L, proMCA-R, proMCA-L, proPCA-R,
proPCA-L and mid-BA) to evaluate the volume, velocity, WSSmax and WSSmean. Statistical
analysis was performed using SPSS (version 25.0, Chicago, IL) software. Independent
two sample t-tests were used to
detect hemodynamic changes among young secondary hypertensive patients and healthy
adults. The influence of different anatomical locations on hemodynamic
parameters was using multivariate variance analysis. Paired t-tests were used for left/right vessels
in different anatomical locations. P<0.05
was considered statistically significant.Results
There were no differences between the left
and right intracranial arteries for any of the hemodynamic parameters (all p values>0.05). Hemodynamic changes
in different locations of the intracranial arteries are displayed in Fig.2. The
proximal PCA had significantly lower volume, velocity and WSS than the values
determined for other locations (p<0.05).
As displayed in Fig.3, compared with healthy adults, young secondary
hypertensive patients have lower WSSmax and WSSmean at the anatomical location
of ICA-C3 (p<0.05).Discussion
4D
flow MRI is an emerging tool for the evaluation of cardiovascular hemodynamics
with full volumetric coverage. It measures the flow velocity directly in vivo
and has been mostly used in the cardiovascular system in clinical practice[1].
Our results showed no differences in the bilateral intracranial arteries,
indicating that the origin of the blood vessels may not cause the difference in
hemodynamics. Hypertensive vascular disease is
mainly characterized by thickening and poor elasticity of blood vessel walls,
which can lead to atherosclerosis, aneurysm and aortic dissection. The vessel
diameter can increase with hypertensive due to its decreased elasticity[2], which may contribute to the decreased velocity. This
state of hemodynamics led to the formation of atherosclerosis, aneurysm and
aortic dissection. It is now widely accepted that low WSS is an essential factor
in promoting plaque formation[3]. To some extent, our study in line
with this theory. The WSSmax and WSSmean demonstrated a reduction in young
secondary hypertensive patients. The low WSS increased the uptake of oxidized
low-density lipoprotein[4], causing
increasing lipid components to form in plaques. Moreover, the low WSS altered
the vascular endothelium flow patterns at the molecular and cellular levels. All these reactions promote the development of
atherosclerosis[5].Conclusion
As
an initial and exploratory study, this work showed that young secondary
hypertensive patients have lower WSSmax and WSSmean at the anatomical location
of ICA-C3, compared with healthy adults. This may imply that low WSS is more
likely to cause atherosclerosis, aneurysm and aortic dissection. This indicates
that hypertension and anatomical location impacted hemodynamic.Acknowledgements
Health Industry Scientific Research Program Project of Gansu Province (Project Number: GSWSKY-2019-09)References
[1] Holmgren
M, Wåhlin A, Dunås T, et al. Assessment of cerebral blood flow pulsatility and
cerebral arterial compliance with 4d flow mri[J]. Journal of Magnetic Resonance
Imaging, 2020, 51(5): 1516-1525.
[2] Birnefeld J, Wåhlin A, Eklund A, et al. Cerebral arterial
pulsatility is associated with features of small vessel disease in patients
with acute stroke and TIA: a 4D flow MRI study[J]. Journal of Neurology, 2020,
267(3): 721-730.
[3] Wolak A, Gransar H, Thomson L E J, et al. Aortic size
assessment by noncontrast cardiac computed tomography: normal limits by age,
gender, and body surface area[J]. JACC: Cardiovascular Imaging, 2008, 1(2):
200-209.
[4] Miller
K B, Howery A J, Rivera-Rivera L A, et al. Age-related reductions in
cerebrovascular reactivity using 4D flow MRI[J]. Frontiers in aging
neuroscience, 2019, 11: 281.
[5] Zhang G, Wang Z, Zhang S, et al. Age and anatomical location
related hemodynamic changes assessed by 4D flow MRI in the carotid arteries of
healthy adults[J]. European Journal of Radiology, 2020: 109035.