Shift to the Mechanics: Distensibility as a Predictor for Ascending Thoracic Aortic Aneurysm Failure
Presented During:
Thursday, April 25, 2024: 5:38PM - 7:00PM
Sheraton Times Square
Posted Room Name:
Central Park
Abstract No:
P0303
Submission Type:
Abstract Submission
Authors:
Nele Famaey (1), Klaas Vander Linden (1), Amber Hendrickx (2), Emma Vanderveken (2), Lucas Van Hoof (2), Steven Dymarkowski (3), Filip Rega (2), Peter Verbrugghe (2), Bart Meuris (2)
Institutions:
(1) Division of Biomechanics, KU Leuven, Leuven, Vlaams-Brabant, Belgium, (2) Cardiac Surgery, KU Leuven, Belgium, Leuven, Vlaams-Brabant, Belgium, (3) Department of Imaging & Pathology, UZ Leuven. Belgium, Leuven, Vlaams-Brabant, Belgium
Submitting Author:
Nele Famaey
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Division of Biomechanics, KU Leuven
Division of Biomechanics, KU Leuven
Co-Author(s):
Klaas Vander Linden
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Division of Biomechanics, KU Leuven
Division of Biomechanics, KU Leuven
Amber Hendrickx
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Cardiac Surgery, KU Leuven, Belgium
Cardiac Surgery, KU Leuven, Belgium
Emma Vanderveken
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Cardiac Surgery, KU Leuven, Belgium
Cardiac Surgery, KU Leuven, Belgium
Lucas Van Hoof
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Cardiac Surgery, KU Leuven, Belgium
Cardiac Surgery, KU Leuven, Belgium
Steven Dymarkowski
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Department of Imaging & Pathology, UZ Leuven. Belgium
Department of Imaging & Pathology, UZ Leuven. Belgium
Filip Rega
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Cardiac Surgery, KU Leuven, Belgium
Cardiac Surgery, KU Leuven, Belgium
Peter Verbrugghe
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Cardiac Surgery, KU Leuven, Belgium
Cardiac Surgery, KU Leuven, Belgium
Bart Meuris
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Cardiac Surgery, KU Leuven, Belgium
Cardiac Surgery, KU Leuven, Belgium
Presenting Author:
Nele Famaey
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KU Leuven
KU Leuven
Abstract:
Objective:
Rupture and dissection are feared complications of ascending thoracic aortic aneurysms (ATAA). ATAA failure is a mechanical phenomenon, occurring when the stress in the wall exceeds the strength of the material. Unfortunately, there are no direct biomarkers to evaluate wall stress and strength, such that other predictors are needed to estimate the risk of failure. Currently, the largest aortic diameter is used as predictor, but since this criterion lacks accuracy, groups are advising a 'shift to the left' in terms of threshold value for surgery. Though this would reduce the number of ATAA failures, it will further increase the number of false positives.
Methods:
To identify better predictors, we performed a retrospective personalized failure risk analysis, including clinical, geometrical, histological and mechanical data of 33 patients. Uniaxial tensile tests until failure were performed to determine the wall strength. Material parameters were fitted against ex vivo planar biaxial data and in vivo pressure-diameter relationships at diastole and systole. Using the resulting material properties and in vivo data, the maximal in vivo stress at 110% systole was calculated, assuming a thin-walled axisymmetric geometry. The retrospective failure risk (RFR), defined as the ratio between the maximal stress and maximal strength in each direction (i.e. the circumferential and axial direction of the aneurysm), was correlated with prospective parameters to find the best failure risk predictor. A.o., the maximum diameter at systole (D_sys) and the volumetric distensibility coefficient (DC_V) were considered as predictors. This distensibility coefficient reflects the aneurysm's compliance and is calculated as the normalized aneurysm volume change between diastole and systole as measured on an ECG gated CT-scan, divided by the pulse pressure.
Results:
The results show that the volumetric distensibility coefficient (DC_V) outperforms other predictors, including maximum aneurysm diameter (D_sys), in terms of correlation to the retrospective failure risk of the aneurysm (RFR) in each direction. Indeed as shown in the figure, the Spearman correlation coefficient for the D_sys vs RFR correlation was ρ = 0,29 with a corresponding p-value of 0,35 in the axial direction, as compared to ρ = -0,80 and p < 0,01 for the DC_V vs RFR correlation. Also in the circumferential direction, D_sys vs RFR shows a ρ = 0,44 with a p-value of 0,07, whereas DC_V vs RFR shows ρ = -0,59 with p < 0,05.
Conclusion:
In contrast to the maximum aortic diameter, the volumetric distensibility coefficient significantly correlates to the retrospective personalized failure risk of 33 patients in our clinical study. This distensibility coefficient is easily calculated in a clinical setting provided an ECG gated CT-scan and BP measurement. Rather than shifting to the left in the diameter criterion, we propose further consideration of this mechanics-based predictor of ATAA failure risk.
Rupture and dissection are feared complications of ascending thoracic aortic aneurysms (ATAA). ATAA failure is a mechanical phenomenon, occurring when the stress in the wall exceeds the strength of the material. Unfortunately, there are no direct biomarkers to evaluate wall stress and strength, such that other predictors are needed to estimate the risk of failure. Currently, the largest aortic diameter is used as predictor, but since this criterion lacks accuracy, groups are advising a 'shift to the left' in terms of threshold value for surgery. Though this would reduce the number of ATAA failures, it will further increase the number of false positives.
Methods:
To identify better predictors, we performed a retrospective personalized failure risk analysis, including clinical, geometrical, histological and mechanical data of 33 patients. Uniaxial tensile tests until failure were performed to determine the wall strength. Material parameters were fitted against ex vivo planar biaxial data and in vivo pressure-diameter relationships at diastole and systole. Using the resulting material properties and in vivo data, the maximal in vivo stress at 110% systole was calculated, assuming a thin-walled axisymmetric geometry. The retrospective failure risk (RFR), defined as the ratio between the maximal stress and maximal strength in each direction (i.e. the circumferential and axial direction of the aneurysm), was correlated with prospective parameters to find the best failure risk predictor. A.o., the maximum diameter at systole (D_sys) and the volumetric distensibility coefficient (DC_V) were considered as predictors. This distensibility coefficient reflects the aneurysm's compliance and is calculated as the normalized aneurysm volume change between diastole and systole as measured on an ECG gated CT-scan, divided by the pulse pressure.
Results:
The results show that the volumetric distensibility coefficient (DC_V) outperforms other predictors, including maximum aneurysm diameter (D_sys), in terms of correlation to the retrospective failure risk of the aneurysm (RFR) in each direction. Indeed as shown in the figure, the Spearman correlation coefficient for the D_sys vs RFR correlation was ρ = 0,29 with a corresponding p-value of 0,35 in the axial direction, as compared to ρ = -0,80 and p < 0,01 for the DC_V vs RFR correlation. Also in the circumferential direction, D_sys vs RFR shows a ρ = 0,44 with a p-value of 0,07, whereas DC_V vs RFR shows ρ = -0,59 with p < 0,05.
Conclusion:
In contrast to the maximum aortic diameter, the volumetric distensibility coefficient significantly correlates to the retrospective personalized failure risk of 33 patients in our clinical study. This distensibility coefficient is easily calculated in a clinical setting provided an ECG gated CT-scan and BP measurement. Rather than shifting to the left in the diameter criterion, we propose further consideration of this mechanics-based predictor of ATAA failure risk.
Aortic Symposium:
Ascending Aorta
Image or Table
