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3067 Biomechanical analysis of acute versus chronic aortic dissection flaps
- Xiaoying Lou, Wei Sun, Fatiesa Sulejmani, Minliang Liu, Edward Chen, Bradley Leshnower
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- Journal:
- Journal of Clinical and Translational Science / Volume 3 / Issue s1 / March 2019
- Published online by Cambridge University Press:
- 26 March 2019, p. 102
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- Article
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OBJECTIVES/SPECIFIC AIMS: Thoracic endovascular aortic repair (TEVAR) is more effective in remodeling the dissected aorta in acute versus chronic type B aortic dissection (TBAD). It has been hypothesized that this is due to differences in dissection flap biomechanical and structural properties but has not been confirmed in explanted human aortic tissue. We aimed to characterize and compare differences in tissue biomechanics and microstructure between acute and chronic dissection flaps that may underlie these findings. METHODS/STUDY POPULATION: Dissection flaps were obtained at time of operative repair for patients presenting for open aortic replacement to treat acute type A (ACUTE, n=7) or chronic type B (CHRONIC, n=7) aortic dissection. Given that the current treatment modality for acute complicated TBAD is TEVAR, it was not feasible to acquire acute TBAD flaps for analysis. Tissues were cryopreserved and subjected to biaxial tensile testing in the circumferential and longitudinal directions. Stiffness was quantified by the tangent modulus (TM) in the low and high linear regions of the compiled equibiaxial response curves for each cohort. Extensibility was defined as the intersection of the fitted line from the high linear region with the x-axis, and the degree of anisotropy (DA) was defined as the mean absolute percentage error of the strains in both directions. Flap architecture and collagen fiber organization were also compared between groups using two-photon microscopy. RESULTS/ANTICIPATED RESULTS: Average age of dissection flaps were 3.4±3.4 days in ACUTE and 1,868.7±1,354.0 days in CHRONIC (p=0.011). There were no differences in age, co-morbidities, maximum aortic diameter, and aortic wall thickness. ACUTE exhibited an anisotropic stress-strain response with increased extensibility longitudinally than circumferentially (0.18 vs. 0.09, p=0.022, DA=0.67) while CHRONIC demonstrated an isotropic response with similar extensibility in either direction (0.11 vs. 0.12, p=0.606, DA=0.26). CHRONIC and ACUTE had comparable stiffness in the circumferential direction (TMlow 439.92 vs. 541.08, p=0.729, and TMhigh 1585.19 kPa vs. 1869.35 kPa, p=0.817). In the longitudinal direction, CHRONIC was significantly stiffer than ACUTE (TMhigh 8347.61 kPa vs. 1201.34 kPa, p=0.049) (FIGURE). Microscopy corroborated these findings with greater collagen fiber organization circumferentially than longitudinally in ACUTE and increasing fibrosis, collagen predominance, and straightening of collagen fibers in CHRONIC. DISCUSSION/SIGNIFICANCE OF IMPACT: Compared to ACUTE, CHRONIC exhibited loss of anisotropy with increased tissue stiffness in the longitudinal direction. Increased dissection flap fibrosis and decreased compliance may explain the worse outcomes for aortic remodeling after TEVAR in chronic TBAD. This study offers biomechanical support for early TEVAR in the acute phase of uncomplicated TBAD.
Chapter 73 - Thoracic aortic disease
- from Section 18 - Cardiothoracic Surgery
- Edited by Michael F. Lubin, Emory University, Atlanta, Thomas F. Dodson, Emory University, Atlanta, Neil H. Winawer, Emory University, Atlanta
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- Book:
- Medical Management of the Surgical Patient
- Published online:
- 05 September 2013
- Print publication:
- 15 August 2013, pp 582-584
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Summary
The management of thoracic aortic disease is based upon the aortic pathology and anatomy. The thoracic aorta is evaluated in four separate segments: the aortic root, ascending aorta, transverse arch, and descending aorta. In addition to the aortic disease, factors that affect the timing and extent of surgical replacement of the thoracic aorta include the presence of aortic valve pathology, concomitant cardiac disease, and the patient's age and comorbidities. This chapter will review the most common indications for treatment of diseases of the thoracic aorta and the perioperative care of patients undergoing aortic surgery.
The most common indications for surgery on the thoracic aorta, in descending order, are aneurysmal disease, acute aortic syndromes, trauma, and infection. The incidence of thoracic aortic aneurysms is estimated to be 5.9 cases per 100,000 person-years, and replacement of the ascending aorta accounts for the majority of thoracic aorta procedures. The most common causes of thoracic aortic aneurysms (TAAs) are cystic medial necrosis; atherosclerosis; heritable connective tissue disorders (e.g., Marfan syndrome); familial, bicuspid aortic valve disease; and chronic aortic dissection. The presence or absence of symptoms is the most important factor in the management of patients with thoracic aortic aneurysms. Patients with symptomatic TAAs typically experience chest or back pain, depending upon the location of the aneurysm. The sudden onset of pain is considered an ominous warning sign of imminent rupture or dissection, and surgery is indicated for all patients with symptomatic TAAs.