Patients and Methods:
Patient 1 was a 66-year-old woman with TAV who presented with a 5.1 cm
ascending aortic (AAo) aneurysm extending into a 4.3 cm transverse arch
with moderate AI on echocardiography. She underwent AAo and proximal
transverse arch replacement using a 24 mm Dacron graft and placement of
a 21 mm HAART ring. Patient 2 was a 62-year-old woman with TAV who
presented with an AAo aneurysm and mild-to-moderate AI on
echocardiography. Preoperative cardiac MR demonstrated an aortic root
diameter of 3.6 cm, an AAo diameter of 5.2 cm, and a proximal transverse
arch diameter of 4.4 cm. The patient underwent AAo and transverse arch
replacement with a 26 mm Dacron graft and placement of a 21 mm HAART
ring. All patients provided informed consent and the study was approved
by the Institutional Review Board of Northwestern University.
To understand the impact of aortic replacement and HAART ring
implantation on aortic hemodynamics, 4D flow MRI was performed pre- and
post-operatively in patient 1, and post-operatively in patient 2.
Post-operative scans were acquired on post-op day 4 and day 2 for
patients 1 and 2, respectively. Aortic hemodynamics were visualized
using time-resolved 3D pathlines to illustrate blood flow over the
cardiac cycle (EnSight, Ansys, USA). 3D velocity streamlines tangent to
the time-resolved velocity vector field were used to demonstrate
instantaneous hemodynamics in the aorta. All traces were color-coded
according to velocity. Peak velocity, forward and retrograde flow, and
regurgitant fraction were calculated within planes placed orthogonal to
the aortic midline at the levels of the aortic root 1 cm above the AV,
in the proximal AAo 1 cm above the sinotubular junction, in the mid AAo
at the level of the pulmonary artery, in the AAo just proximal to the
brachiocephalic trunk, between the brachiocephalic trunk and the left
common carotid artery, between the left common carotid and left
subclavian arteries, in the proximal descending aorta (DAo), in the mid
DAo at the level of the aortic root, and in the distal DAo. 3D systolic
wall shear stress (WSS) magnitude at the surface of the aorta, which has
been implicated in aortic wall remodeling, was calculated at peak
systole and maximal intensity plots were generated for the AAo and
arch4. Peak viscous energy loss (VEL) over the cardiac
cycle, a marker of abnormal flow and ventricular loading, was calculated
and normalized to segmented aortic volume5. VEL and
WSS in HAART patients were compared to an 80-year-old woman with TAV who
underwent AAo and proximal transverse arch replacement without HAART
ring placement as a control.