UCSF

Background

Guidelines for sinus of Valsalva (SOV)-thoracic aortic aneurysms in Marfan syndrome recommend size-based criteria for elective surgical repair. Biomechanics may provide a better prediction of dissection risk than diameter. Our aim was to determine magnitudes of wall stress in the aortic root of Marfan patients using finite element analyses.

Methods

Forty-six Marfan patients underwent patient-specific 3-dimensional SOV-thoracic aortic aneurysm geometry reconstruction using imaging data. Finite element analyses were performed to determine wall stress distributions at SOV, sinotubular junction (STJ), and ascending aorta (AscAo) at systole.

Results

Peak circumferential stresses were 432.8 ± 111 kPa, 408.1 ± 88.3 kPa, and 321.9 ± 83.8 kPa at the SOV, STJ, and AscAo, respectively, with significant differences between SOV and AscAo (P < 3.08E-07), and STJ and AscAo (P < 2.26E-06). Peak longitudinal wall stresses were 352 ± 73.9 kPa, 277.5 ± 89.5 kPa, and 200.6 ± 81 kPa at SOV, STJ, and AscAo, respectively, with significant differences between SOV and STJ (P < 6.01E-06), SOV and AscAo (P < 9.79E-13), and STJ and AscAo (P < 3.34E-07). Diameter was not correlated to wall stresses. Comparison of wall stresses in aneurysm <5 cm vs ≥5 cm and <4.5 cm vs ≥4.5 cm showed no significant differences in wall stresses in the circumferential or longitudinal direction.

Conclusions

Peak wall stresses in Marfan SOV- thoracic aortic aneurysm were greatest in SOV than STJ than AscAo. Diameter was poorly correlated to peak stresses such that current guidelines with 5 cm cutoff had significant overlap in peak stresses in patients with <5 cm vs ≥5 cm. Use of patient-specific Marfan aneurysm models may identify patients with high wall stresses and small aneurysms who could benefit from earlier surgical repair to prevent aortic dissection.