Andrew D. Wisneski1,2, Zhongjie Wang1, Yue Xuan1, Julius M. Guccione1, Liang Ge1, Elaine E. Tseng11Department of Surgery, University of California San Francisco (UCSF) and San Francisco Veterans Affairs Medical Center (SFVAMC), San Francisco, CA, USA
2Electronic correspondence: Andrew.email@example.com
Background and aim of the study: Pulmonary autograft dilatation after the Ross operation often necessitates reoperation. To understand autograft remodeling, a biomechanical understanding of human autografts after exposure to systemic pressure is required. An ex-vivo human pulmonary autograft finite element (FE) model was previously developed to predict wall stress after exposure to systemic pressure. However, autograft material properties vary significantly among individuals. The aim of the study was to quantify the range of wall stress changes in a human autograft after the Ross operation prior to remodeling, based on normal variation in human autograft mechanical properties.
Methods: A normal human autograft FE model was loaded to pulmonary and systemic arterial pressures. Stress-strain data of normal human autografts (n = 24) were incorporated into an Ogden hyper-elastic model to describe autograft mechanical behavior. Autograft wall stresses at pulmonary versus systemic pressures were examined. Autograft volume-based stress analysis was performed, based on percentage of autograft element volume exceeding one standard deviation (SD)
above the group mean stress at systemic systole.
Results: Mean first-principle wall stresses (FPS) at systole of systemic versus pulmonary pressures were 129.29 ± 17.47 kPa versus 24.42 ± 3.85kPa (p <0.001) at the annulus, 187.53 ± 20.06 kPa versus 35.98 ± 2.15 kPa at sinuses (p <0.001), and 268.68 ± 23.40 kPa versus 50.15 ± 5.90 kPa (p <0.001) at the sinotubuluar junction (STJ). The percentage of autograft element volume that exceeded one SD above the group mean was 14.3 ± 5.6% for FPS and 12.6 ± 10.1% for second-principle stresses.
Conclusion: Normal human autograft biomechanical responses to systemic pressure based on patient-specific material properties were quantified. Regions of peak stresses were observed in autograft sinuses and STJ regions, which corresponded clinically to locations of autograft dilation. The results provided valuable information on predicting variations in patient-specific ex-vivo FE models when population-based material properties are used in settings where patient-specific properties are unknown.
The Journal of Heart Valve Disease 2018;28:22-31
|Range of Pulmonary Autograft Responses to Systemic Pressure Immediately After the Ross Procedure|
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