Segmental Variations in the Peel Characteristics of the Porcine Thoracic Aorta
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Annals of Biomedical Engineering (Ó 2020) https://doi.org/10.1007/s10439-020-02489-x
Original Article
Segmental Variations in the Peel Characteristics of the Porcine Thoracic Aorta MANOJ MYNENI, AKSHAY RAO, MINGLIANG JIANG, MICHAEL R. MORENO, K. R. RAJAGOPAL, and CHANDLER C. BENJAMIN Department of Mechanical Engineering, Texas A&M University, 100 Mechanical Engineering Office Building, College Station, TX 77843-3123, USA (Received 21 November 2019; accepted 3 March 2020) Associate Editor Estefanı´ a Pen˜a oversaw the review of this article.
Abstract—Aortic dissection occurs predominantly in the thoracic aorta and the mechanisms for the initiation and propagation of the tear in aortic dissection are not well understood. We study the tearing characteristics of the porcine thoracic aorta using a peeling test and we estimate the peeling energy per unit area in the ascending and the descending segments. The stretch and the peel force per unit width undergone by the peeled halves of a rectangular specimen are measured. We find that there can be significant variation in the stretch within the specimen and the stretch between the markers in the specimen varies with the dynamics of peeling. We found that in our experiment the stretch achieved in the peeled halves was such that it was in the range of the stretch at which the stress–stretch curve for the uniaxial experiment starts deviating from linearity. Higher peeling energy per unit area is required in the ascending aorta compared to the descending aorta. Longitudinal specimens required higher peeling energy per unit area when compared to the circumferential specimens. Keywords—Porcine aorta, Peeling energy, Segmental variation, Local stretch.
INTRODUCTION Aortic dissection is an acute life threatening cardiovascular disease causing significant mortality and morbidity. Formation of a tear in the aortic wall and the propagation of the tear axially and circumferentially along the wall are the characteristics of aortic dissection. Propagation of the tear typically occurs in
Address correspondence to Chandler C. Benjamin, Department of Mechanical Engineering, Texas A&M University, 100 Mechanical Engineering Office Building, College Station, TX 77843-3123, USA. Electronic mail: [email protected]
the medial layer.5 It is estimated that 40% of the aortic dissection patients die immediately, and if left untreated, 1–2% die per hour thereafter.20 Predicting the occurrence of aortic dissection and controlling the rate of propagation of the tear play an important role in treating aortic dissection. Altered hemodynamics (typically hypertension) with a concomitant weakening of the aortic media due to aging and disease are the factors commonly associated with aortic dissection.12 Canine and porcine models were previously used to examine the hemodynamic and structural factors influencing the tear propagation in aortic dissection19,28 due to the similarities with humans in terms of aortic diameter and microstructure. Knowledge of the mechanical properties of the thoracic aorta in healt
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