Optimal timing of TEVAR in Uncomplicated Type B Aortic Dissection: Implications from clinical outcomes, and biomechanical and histological analysis of acute versus chronic aortic dissection flaps Open Access

Lou, Xiaoying (Spring 2020)

Permanent URL: https://etd.library.emory.edu/concern/etds/0v838176w?locale=en



Optimal medical therapy(OMT) is considered the standard-of-care in the management of uncomplicated-type-B-aortic-dissection(TBAD) with operative intervention indicated if complications arise in the chronic-phase. However, growing evidence suggests that thoracic endovascular aortic repair(TEVAR) more effectively remodels the dissected aorta in the acute-phase. This thesis examined the impact of TEVAR on short-and long-term survival in uncomplicated TBAD patients(Aim 1). Additionally, we characterized changes in biomechanics and microstructure between acute-vs-chronic dissection flaps that may underlie aortic-remodeling(Aim 2).


Aim 1:A review of our institutional database from 2000-2016 identified 398 patients diagnosed with TBAD. At index hospitalization, complicated patients underwent TEVAR(aTEVAR,n=80) and uncomplicated patients received OMT(n=318). Uncomplicated patients were divided into subgroups based upon final treatment received:1)TEVAR(cTEVAR);2)open aortic replacement(OPEN);and 3)OMT. Kaplan-Meier analyses assessed long-term mortality.

Aim 2:Dissection flaps were obtained from patients presenting for open aortic replacement to treat acute type A(ACUTE) or chronic type B(CHRONIC) aortic dissection(n=10 each). Tissues were subjected to biaxial testing circumferentially and longitudinally with stiffness quantified by the tangent modulus(TM) in the low and high linear-regions of the biaxial response curves. Qualitative histological analyses of elastin and collagen organization were also conducted.


Among uncomplicated TBAD patients, 146(45.9%) failed OMT and underwent open(n=59) or endovascular(n=87) repair in the chronic phase. There was a trend towards improved long-term survival in complicated TBAD patients(complicated 84.1% vs uncomplicated 58.9%,p=0.17). Intervention-free survival at 5 and 10 years for all uncomplicated patients was 49.4% and 30.9%.

On biaxial testing, while stiffness between ACUTE and CHRONIC was similar circumferentially(chronic vs acute ratio:TMlow1.36,p=0.656, and TMhigh0.42,p=0.067), in the longitudinal direction, CHRONIC was over 3-fold stiffer than ACUTE(chronic vs acute ratio:TMlow3.45,p=0.011 and TMhigh3.76,p=0.016). Histology corroborated these findings, demonstrating increased fibrosis and loss of collagen fiber organization in CHRONIC.


Despite being the highest-risk subgroup of TBAD patients, complicated TBAD patients receiving TEVAR in the acute-phase had improved survival compared to uncomplicated patients receiving any intervention in the chronic-phase. The loss of anisotropy, increased fibrosis and stiffness as a dissection flap transitions from the acute-to chronic-phase may explain the worse aortic-remodeling outcomes after TEVAR in chronic TBAD. TEVAR at index hospitalization may serve as optimal therapy for uncomplicated TBAD.

Table of Contents

Introduction p3-5

Background p6-8

Methods p9-17

Results p18-21

Discussion/Conclusions p22-28

References p29-33

Tables/Figures p34-49

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