The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium

Christoph M. Augustin; Thomas E. Fastl; Aurel Neic; Chiara Bellini; John Whitaker; Ronak Rajani; Mark D. O’Neill; Martin J. Bishop; Gernot Plank; Steven A. Niederer

doi:10.1007/s10237-019-01268-5

The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium

Christoph M. Augustin, Thomas E. Fastl, Aurel Neic, Chiara Bellini, John Whitaker, Ronak Rajani, Mark D. O’Neill, Martin J. Bishop, Gernot Plank, Steven A. Niederer^*

^*Corresponding author for this work

Biomedical Engineering Department

Research output: Contribution to journal › Article › peer-review

27 Citations (Scopus)

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Abstract

The left atrium (LA) has a complex anatomy with heterogeneous wall thickness and curvature. The anatomy plays an important role in determining local wall stress; however, the relative contribution of wall thickness and curvature in determining wall stress in the LA is unknown. We have developed electromechanical finite element (FE) models of the LA using patient-specific anatomical FE meshes with rule-based myofiber directions. The models of the LA were passively inflated to 10mmHg followed by simulation of the contraction phase of the atrial cardiac cycle. The FE models predicted maximum LA volumes of 156.5 mL, 99.3 mL and 83.4 mL and ejection fractions of 36.9%, 32.0% and 25.2%. The median wall thickness in the 3 cases was calculated as 1.32±0.78 mm, 1.21±0.85 mm, and 0.74±0.34 mm. The median curvature was determined as 0.159±0.080 mm ^{- 1}, 0.165±0.079mm-1, and 0.166±0.077mm-1. Following passive inflation, the correlation of wall stress with the inverse of wall thickness and curvature was 0.55–0.62 and 0.20–0.25, respectively. At peak contraction, the correlation of wall stress with the inverse of wall thickness and curvature was 0.38–0.44 and 0.16–0.34, respectively. In the LA, the 1st principal Cauchy stress is more dependent on wall thickness than curvature during passive inflation and both correlations decrease during active contraction. This emphasizes the importance of including the heterogeneous wall thickness in electromechanical FE simulations of the LA. Overall, simulation results and sensitivity analyses show that in complex atrial anatomy it is unlikely that a simple anatomical-based law can be used to estimate local wall stress, demonstrating the importance of FE analyses.

Original language	English
Journal	Biomechanics and Modeling in Mechanobiology
Early online date	4 Dec 2019
DOIs	https://doi.org/10.1007/s10237-019-01268-5
Publication status	E-pub ahead of print - 4 Dec 2019

Keywords

Cardiac mechanics
Finite element simulation
Left atrium
Patient-specific modeling
Wall stress

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The impact of wall_AUGUSTIN_Accepted21November2019_Published4December2019_GOLD VoR (CC BY)Final published version, 4.19 MBLicence: CC BY

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Augustin, C. M., Fastl, T. E., Neic, A., Bellini, C., Whitaker, J., Rajani, R., O’Neill, M. D., Bishop, M. J., Plank, G., & Niederer, S. A. (2019). The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium. Biomechanics and Modeling in Mechanobiology. Advance online publication. https://doi.org/10.1007/s10237-019-01268-5

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title = "The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium",

abstract = "The left atrium (LA) has a complex anatomy with heterogeneous wall thickness and curvature. The anatomy plays an important role in determining local wall stress; however, the relative contribution of wall thickness and curvature in determining wall stress in the LA is unknown. We have developed electromechanical finite element (FE) models of the LA using patient-specific anatomical FE meshes with rule-based myofiber directions. The models of the LA were passively inflated to 10mmHg followed by simulation of the contraction phase of the atrial cardiac cycle. The FE models predicted maximum LA volumes of 156.5 mL, 99.3 mL and 83.4 mL and ejection fractions of 36.9%, 32.0% and 25.2%. The median wall thickness in the 3 cases was calculated as 1.32±0.78 mm, 1.21±0.85 mm, and 0.74±0.34 mm. The median curvature was determined as 0.159±0.080 mm - 1, 0.165±0.079mm-1, and 0.166±0.077mm-1. Following passive inflation, the correlation of wall stress with the inverse of wall thickness and curvature was 0.55–0.62 and 0.20–0.25, respectively. At peak contraction, the correlation of wall stress with the inverse of wall thickness and curvature was 0.38–0.44 and 0.16–0.34, respectively. In the LA, the 1st principal Cauchy stress is more dependent on wall thickness than curvature during passive inflation and both correlations decrease during active contraction. This emphasizes the importance of including the heterogeneous wall thickness in electromechanical FE simulations of the LA. Overall, simulation results and sensitivity analyses show that in complex atrial anatomy it is unlikely that a simple anatomical-based law can be used to estimate local wall stress, demonstrating the importance of FE analyses.",

keywords = "Cardiac mechanics, Finite element simulation, Left atrium, Patient-specific modeling, Wall stress",

author = "Augustin, {Christoph M.} and Fastl, {Thomas E.} and Aurel Neic and Chiara Bellini and John Whitaker and Ronak Rajani and O{\textquoteright}Neill, {Mark D.} and Bishop, {Martin J.} and Gernot Plank and Niederer, {Steven A.}",

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T1 - The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium

AU - Augustin, Christoph M.

AU - Fastl, Thomas E.

AU - Neic, Aurel

AU - Bellini, Chiara

AU - Whitaker, John

AU - Rajani, Ronak

AU - O’Neill, Mark D.

AU - Bishop, Martin J.

AU - Plank, Gernot

AU - Niederer, Steven A.

PY - 2019/12/4

Y1 - 2019/12/4

N2 - The left atrium (LA) has a complex anatomy with heterogeneous wall thickness and curvature. The anatomy plays an important role in determining local wall stress; however, the relative contribution of wall thickness and curvature in determining wall stress in the LA is unknown. We have developed electromechanical finite element (FE) models of the LA using patient-specific anatomical FE meshes with rule-based myofiber directions. The models of the LA were passively inflated to 10mmHg followed by simulation of the contraction phase of the atrial cardiac cycle. The FE models predicted maximum LA volumes of 156.5 mL, 99.3 mL and 83.4 mL and ejection fractions of 36.9%, 32.0% and 25.2%. The median wall thickness in the 3 cases was calculated as 1.32±0.78 mm, 1.21±0.85 mm, and 0.74±0.34 mm. The median curvature was determined as 0.159±0.080 mm - 1, 0.165±0.079mm-1, and 0.166±0.077mm-1. Following passive inflation, the correlation of wall stress with the inverse of wall thickness and curvature was 0.55–0.62 and 0.20–0.25, respectively. At peak contraction, the correlation of wall stress with the inverse of wall thickness and curvature was 0.38–0.44 and 0.16–0.34, respectively. In the LA, the 1st principal Cauchy stress is more dependent on wall thickness than curvature during passive inflation and both correlations decrease during active contraction. This emphasizes the importance of including the heterogeneous wall thickness in electromechanical FE simulations of the LA. Overall, simulation results and sensitivity analyses show that in complex atrial anatomy it is unlikely that a simple anatomical-based law can be used to estimate local wall stress, demonstrating the importance of FE analyses.

AB - The left atrium (LA) has a complex anatomy with heterogeneous wall thickness and curvature. The anatomy plays an important role in determining local wall stress; however, the relative contribution of wall thickness and curvature in determining wall stress in the LA is unknown. We have developed electromechanical finite element (FE) models of the LA using patient-specific anatomical FE meshes with rule-based myofiber directions. The models of the LA were passively inflated to 10mmHg followed by simulation of the contraction phase of the atrial cardiac cycle. The FE models predicted maximum LA volumes of 156.5 mL, 99.3 mL and 83.4 mL and ejection fractions of 36.9%, 32.0% and 25.2%. The median wall thickness in the 3 cases was calculated as 1.32±0.78 mm, 1.21±0.85 mm, and 0.74±0.34 mm. The median curvature was determined as 0.159±0.080 mm - 1, 0.165±0.079mm-1, and 0.166±0.077mm-1. Following passive inflation, the correlation of wall stress with the inverse of wall thickness and curvature was 0.55–0.62 and 0.20–0.25, respectively. At peak contraction, the correlation of wall stress with the inverse of wall thickness and curvature was 0.38–0.44 and 0.16–0.34, respectively. In the LA, the 1st principal Cauchy stress is more dependent on wall thickness than curvature during passive inflation and both correlations decrease during active contraction. This emphasizes the importance of including the heterogeneous wall thickness in electromechanical FE simulations of the LA. Overall, simulation results and sensitivity analyses show that in complex atrial anatomy it is unlikely that a simple anatomical-based law can be used to estimate local wall stress, demonstrating the importance of FE analyses.

KW - Cardiac mechanics

KW - Finite element simulation

KW - Left atrium

KW - Patient-specific modeling

KW - Wall stress

U2 - 10.1007/s10237-019-01268-5

DO - 10.1007/s10237-019-01268-5

M3 - Article

AN - SCOPUS:85076099100

SN - 1617-7959

JO - Biomechanics and Modeling in Mechanobiology

JF - Biomechanics and Modeling in Mechanobiology

ER -

The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium

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