Original article
Adult cardiac
Pathogenesis of Acute Aortic Dissection: A Finite Element Stress Analysis

https://doi.org/10.1016/j.athoracsur.2010.10.042Get rights and content

Background

Type A and type B aortic dissections typically result from intimal tears above the sinotubular junction and distal to the left subclavian artery (LSA) ostium, respectively. We hypothesized that this pathology results from elevated pressure-induced regional wall stress.

Methods

We identified 47 individuals with normal thoracic aortas by electrocardiogram-gated computed tomography angiography. The thoracic aorta was segmented, reconstructed, and triangulated to create a geometric mesh. Finite element analysis using a systolic pressure load of 120 mm Hg was performed to predict regional thoracic aortic wall stress.

Results

There were local maxima of wall stress above the sinotubular junction in the ascending aorta and distal to the ostia of the supraaortic vessels, including the LSA, in the aortic arch. No local maximum of wall stress was found in the descending thoracic aorta. Comparison of the mean peak wall stress above the sinotubular junction (0.43 ± 0.07 MPa), distal to the LSA (0.21 ± 0.07 MPa), and in the descending thoracic aorta (0.06 ± 0.01 MPa) showed a significant effect for wall stress by aortic region (p < 0.001).

Conclusions

In the normal thoracic aorta, there are peaks in wall stress above the sinotubular junction and distal to the LSA ostium. This stress distribution may contribute to the pathogenesis of aortic dissections, given their colocalization. Future investigations to determine the utility of image-derived biomechanical calculations in predicting aortic dissection are warranted, and therapies designed to reduce the pressure load-induced wall stress in the thoracic aorta are rational.

Section snippets

Material and Methods

This study was approved by the Institutional Review Board.

Patient Characteristics

The 47 study patients were a mean age of 56.2 ± 15.6 years, and 24 (51.1%) had hypertension. Maximum aortic diameter of the study population was 3.5 ± 0.6 cm at the aortic root, 3.0 ± 0.5 cm at the STJ, 3.3 ± 0.5 cm in the ascending aorta, 2.5 ± 0.4 in the aortic arch, and 2.4 ± 0.3 in the descending thoracic aorta. The aortic arches were type I in 29 patients and type II in 18. There was no difference between the two groups (Table 1).

Comparison of Wall Stress Throughout the Thoracic Aorta

Comparison of peak wall stress above the STJ (0.43 ± 0.09

Comment

The current research uses FEA to demonstrate increased wall stress in the human thoracic aorta above the STJ and distal to the LSA, where the intimal tears that result in type A and type B aortic dissections typically occur. The wall stress above the STJ was greater than that distal to the LSA, consistent with type A dissections being more common than type B dissections [1, 2, 3, 4]. Older patients were more likely to have a type II arch, as previous studies have shown [15]. However, aortic

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