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Chang et al. Vessel Plus 2020;4:20 I http://dx.doi.org/10.20517/2574-1209.2020.10 Page 3 of 5

because these grafts are too long for the ascending aorta to obtain a sufficient landing zone. Thus, it is
important to have specially designed stent-grafts and accurate imaging study before the procedure.

To date, there still remains some controversy surrounding patient selection for TEVAR. Conventionally,
[10]
aortic valve insufficiency is a contraindication for TEVAR , however, more than one-third of ATAAD
[11]
patients, especially in the severe subgroup, were found to have this. In 2014, Rylski et al. introduced the
concept of endovascular treatment of ascending aortic pathologies with valve-carrying conduits associated
[11]
with an uncovered portion for free diastolic coronary blood flow . Using an endovascular valve-carrying
conduit not only resolves the problem of aortic regurgitation, but also effectively results in sufficient
[12]
[3]
anchorage of the device . Alternatively, Nienaber et al. proposed a combined TAVR (transcatheter aortic
valve replacement)-TEVAR technology, in an attempt to treat variants of aortic dissection including those
with compromised aortic valve function.
[3]
[2]
Fatal complications such as aortic rupture , ventricular perforation and cardiac tamponade , or other
early morbidities such as supraventricular tachycardia and cardiovascular ischemia have been reported
in the current literature. This also raises the concern of cerebrovascular accidents that may occur as the
vascular surgeon passes the guide wire and deploys the stent-graft in a calcified ascending aorta and arch
of ATAAD patients with advanced age and multiple morbidities. In addition, unidentified acute coronary
involvement (ACI) in ATAAD would be fatal and it is worth noting that up to 30% of patients with ACI
[13]
disclosed no clinical manifestations of coronary malperfusion preoperatively .

Once stent implantation is successfully achieved, the second issue is its delayed impact on aortic stiffness.
A healthy aorta has a cushioning function, limiting arterial pulsatility and protects the microvasculature
[14]
from potentially harmful fluctuations in pressure and blood flow . With a complex structure close to
the left ventricle (LV), any deviation from the natural physiologic character of the ascending aorta (such
as increased aorta stiffness) would give rise to complications. Available stent-grafts made of artificial
compounds, such as expanded polytetrafluoroethylene and woven polyester, and metal wire, are poorly
compliant and foreign to the human body. Current Dacron polyester fabric grafts exhibit four times
[5,6]
reduced compliance compared to native arteries . Hence, it is reasonable to assume that wire-containing
[5]
stent-grafts are less compliant . An immobilized segment is created after placement of the stent-graft in
the ascending aorta, alternating in diameter and area during every heartbeat, and more aortic stiffness
develops consequently. Without enough elasticity, the Windkessel effect vanishes leading to more resistance
to LV and rebound force on the aortic valve. It is well established that large-artery stiffness (LAS) impairs
the aortic cushioning function and independently predicts cardiovascular risk. LAS also contributes to
isolated systolic hypertension, excessive penetration of pulsatile energy into the microvasculature of target
organs that operate at low vascular resistance, and abnormal ventricular-arterial interactions that promote
[14]
left ventricular remodeling, dysfunction, and failure . In a 4-year follow-up retrospective study using
patient-specific fluid-structure interaction analysis and image-based measurements of cardiac remodeling
[15]
from echocardiography and computed tomography angiography, van Bakel et al. demonstrated that
[15]
TEVAR-induced acute aortic stiffening caused a 26% increase in LV stroke work and cardiac remodeling .
Moreover, alternated left ventricular hemodynamics may raise concerns of impaired function of the LV
induced by ventricular remodeling and impairment of the aortic valve. It has been found that aortic stiffness
is associated with LV remodeling and reduced LV systolic and diastolic function by magnetic resonance
[16]
imaging measurement in a large multi-ethnic population . Therefore, it is crucial to explore an ideal
stent-graft so as to alleviate the harmful long-term effects and potential pathogenicity to these susceptible
[5]
patients. In addition, a thorough examination of cardiac morphology and function should be performed
in the long-term follow up including echocardiographic parameters of (1) key structural alterations, such as
the left atrial volume index or left ventricular mass index and (2) key functional alterations, such as an E/e’
[17]
ratio of early mitral inflow velocity and an E/A denoting ratio of E wave to A wave .