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. 2018 Aug;156(2):492-500.
doi: 10.1016/j.jtcvs.2018.03.004. Epub 2018 Mar 8.

Wall stress on ascending thoracic aortic aneurysms with bicuspid compared with tricuspid aortic valve

Yue Xuan  1 , Zhongjie Wang  1 , Raymond Liu  1 , Henrik Haraldsson  2 , Michael D Hope  2 , David A Saloner  2 , Julius M Guccione  1 , Liang Ge  1 , Elaine Tseng  3
Affiliations

Wall stress on ascending thoracic aortic aneurysms with bicuspid compared with tricuspid aortic valve

Yue Xuan et al. J Thorac Cardiovasc Surg. 2018 Aug.

Abstract

Objective: Guidelines for repair of bicuspid aortic valve-associated ascending thoracic aortic aneurysms have been changing, most recently to the same criteria as tricuspid aortic valve-ascending thoracic aortic aneurysms. Rupture/dissection occurs when wall stress exceeds wall strength. Recent studies suggest similar strength of bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms; thus, comparative wall stress may better predict dissection in bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms. Our aim was to determine whether bicuspid aortic valve-ascending thoracic aortic aneurysms had higher wall stresses than their tricuspid aortic valve counterparts.

Methods: Patients with bicuspid aortic valve- and tricuspid aortic valve-ascending thoracic aortic aneurysms (bicuspid aortic valve = 17, tricuspid aortic valve = 19) greater than 4.5 cm underwent electrocardiogram-gated computed tomography angiography. Patient-specific 3-dimensional geometry was reconstructed and loaded to systemic pressure after accounting for prestress geometry. Finite element analyses were performed using the LS-DYNA solver (LSTC Inc, Livermore, Calif) with user-defined fiber-embedded material model to determine ascending thoracic aortic aneurysm wall stress.

Results: Bicuspid aortic valve-ascending thoracic aortic aneurysms 99th-percentile longitudinal stresses were 280 kPa versus 242 kPa (P = .028) for tricuspid aortic valve-ascending thoracic aortic aneurysms in systole. These stresses did not correlate to diameter for bicuspid aortic valve-ascending thoracic aortic aneurysms (r = -0.004) but had better correlation to tricuspid aortic valve-ascending thoracic aortic aneurysms diameter (r = 0.677). Longitudinal stresses on sinotubular junction were significantly higher in bicuspid aortic valve-ascending thoracic aortic aneurysms than in tricuspid aortic valve-ascending thoracic aortic aneurysms (405 vs 329 kPa, P = .023). Bicuspid aortic valve-ascending thoracic aortic aneurysm 99th-percentile circumferential stresses were 548 kPa versus 462 kPa (P = .033) for tricuspid aortic valve-ascending thoracic aortic aneurysms, which also did not correlate to bicuspid aortic valve-ascending thoracic aortic aneurysm diameter (r = 0.007).

Conclusions: Circumferential and longitudinal stresses were greater in bicuspid aortic valve- than tricuspid aortic valve-ascending thoracic aortic aneurysms and were more pronounced in the sinotubular junction. Peak wall stress did not correlate with bicuspid aortic valve-ascending thoracic aortic aneurysm diameter, suggesting diameter alone in this population may be a poor predictor of dissection risk. Our results highlight the need for patient-specific aneurysm wall stress analysis for accurate dissection risk prediction.

Keywords: aneurysm; bicuspid aortic valve; wall stress.

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Conflict of interest statement

The authors have no conflicts of interest.

Figures

Figure 1
Figure 1
a. Representative mesh for FE simulation of aTAA. 1b. Sketch of fiber angle dispersion with respect to circumferential direction.
Figure 2
Figure 2
a. Typical wall stress distribution on BAV (a-d) and TAV-aTAA (f-i) along longitudinal direction. 2b. Typical wall stress distribution on BAV (a-d) and TAV-aTAA (f-i) along circumferential direction.
Figure 3
Figure 3
a. Relationship between 99-percentile circumferential stress and aTAA maximum diameter for BAV (circles) and TAV (squares). 3b. Relationship between 99-percentile longitudinal stress and aTAA maximum diameter. Correlation between stress and diameter with r is shown as dashed line for BAV and dotted line for TAV.
Figure 4.
Figure 4.
Peak wall stress and median values in a) ascending aorta and b) STJ of BAV vs. TAV-aTAA at systolic pressure with median values in BAV- (solid line) vs. TAV-aTAA (dashed line) in systole.
See this image and copyright information in PMC

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