Relative Strain is a Novel Predictor of Aneurysmal Degeneration of the Thoracic Aorta: an Ex-Vivo Mechanical Study

Abstract Objective Current guidelines for prophylactic replacement of the thoracic aorta, primarily based on size alone, may not be adequate in identifying patients at risk for either progression of disease or aortic catastrophe. We undertook the current study to determine whether mechanical properties of the aorta might be able to predict aneurysmal dilatation of the aorta using a clinical database and benchtop mechanical testing of human aortic tissue. Methods Utilizing over 400 samples from 31 patients, mechanical properties were studied in (a) normal aorta then (b) between normal and diseased aorta using linear mixed effects models. A machine learning technique was used to predict aortic growth rate over time using mechanical properties and baseline clinical characteristics. Results Healthy aortic tissue under in vivo loading conditions, after accounting for aortic segment location, had lower longitudinal elastic modulus compared to circumferential elastic modulus: -166.8 kPa (95% Confidence Interval [CI] -210.8 to -122.7, p Conclusion Increasing relative strain was identified as a novel independent predictor of aneurysmal degeneration. Non-invasive measurement of relative strain may aid in the identification and monitoring of patients at risk for aneurysmal degeneration.