There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Background
Ascending aorta (AAo) wall shear stress (WSS) may drive aorta dilatation in patients
with bicuspid aortic valve (BAV) and β-blockers are first line medical therapy to
slow this process. This study sought to determine if β-blocker therapy reduces AAo
WSS in BAV patients.
Methods
Right-left coronary leaflet fusion BAV patients on β-blockers (BB+) (n = 30, M:F =
23:7, age: 46 ± 14 years) and not on β-blockers (BB-) (n=30, M:F = 23:7, age: 46 ±
13 years) and healthy controls (n=15, age:43±11 years) underwent time-resolved, 3D
phase contrast (4D flow) MRI. Patient groups were matched by systolic blood pressure
(SBP), degree of aortic stenosis (AS), and AAo diameter (3.9 ± 0.7 vs. 3.9 ± 0.6 cm,
p = 0.70). A 3D segmentation of the thoracic aorta was performed (MIMICS, Materlise,
Belgium). Systolic 3D WSS was calculated in the thoracic aorta from 4D flow velocity
acquisition and a sagittal maximum intensity projection (MIP) of WSS was generated.
Systole was defined as five cardiac time frames centered at the time frame with maximum
average aorta velocity. A region of interest was drawn on the MIP from the sinus of
Valsalva to the brachiocephalic artery to define the AAo, and this region was further
subdivided into anterior and posterior segments. Max and mean systolic AAo WSS were
extracted from each segment. Peak systolic AAo velocity was also measured. Quantitative
results were compared with one-way analysis of variance and linear modeling was performed.
Results
Maximum and mean WSS were not reduced in the BB+ group compared BB- patients in either
the anterior AAo (maximum: 1.49±0.47N/m2 vs. 1.38±0.49N/m2, p=0.99, mean: 0.76±0.2N/m2
vs. 0.74±0.18N/m2, p=1.00) or posterior AAo (maximum: 1.45±0.42N/m2 vs. 1.39±0.58N/m2,
p=1.00; mean: 0.65±0.16N/m2 vs. 0.63±0.16N/m2, p=1.00). Both patient groups had higher
maximum and mean WSS relative to the control group (p=0.001 to p=0.04). AAo peak velocity
was elevated in patients compared to controls (p<0.01) but not significantly different
for BB+ vs. BB- groups (p=0.42). Linear models identified significant relationships
between aortic stenosis severity and increased maximum WSS (β=0.186, p=0.007) and
between diameter at the sinus of Valsalva and reduced mean WSS (β=-0.151, p=0.045).
Conclusions
BB therapy does not reduce systolic WSS or peak velocity and does not impact WSS asymmetry
in the AAo of right-left fusion BAV patients. Further longitudinal studies are needed
to clarify the impact of dose and duration of BB therapy on aortopathy.
Funding
NIH NCI 5R25CA132822-04, NIH NHLBI R01HL115828; AHA13SDG14360004, BAV Program at the
Bluhm Cardiovascular Institute.
Figure 1
Linear Modeling Findings. AAo = ascending aorta; ACE = angiotensin converting enzyme;
ARB = angiotensin receptor blocker; WSS = wall shear stress
Figure 2
Systolic wall shear stress (WSS) maximum intensity projections (MIPs) in BAV patients
with no aortic stenosis (AS), moderate AS, and severe AS from the BB+ and BB- group
compared to a representative control subject.
This article is published under license to BioMed Central Ltd. This is an Open Access
article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided
the original work is properly cited. The Creative Commons Public Domain Dedication
waiver (
http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.