Technical NoteThe effect of tear depth on the propagation of aortic dissections in isolated porcine thoracic aorta
Introduction
Dissection is an often fatal condition because it leads to aortic rupture. Dissections are initiated by a tearing of the intima and a portion of the subjacent media. Due to the laminated structure of the aortic media, the tear then spreads parallel to the true lumen, both circumferentially and longitudinally, creating a false lumen. Tearing, propagation and secondary tear formation have previously been distinguished because of the differences in forces required for each of the stages (Carson and Roach, 1990; van Baardwijk and Roach, 1987). While treatment varies depending on the location of the dissection, both medical and surgical approaches are aimed at preventing propagation and new tears through the lowering of systolic pressure and pulse pressure, and through attempts at surgically reinforcing the damaged aortic wall (Fann and Millar, 1995).
Although it has been reported from necropsy studies that fatal dissection almost exclusively involves the outer half of the aortic media (Roberts, 1981), the likelihood of propagation or rupture has yet to be quantified. In vitro studies have implicated tear depth as an important factor in propagation (Mitsui et al., 1994; van Baardwijk and Roach, 1987). This study was aimed at determining the relationship between the depth of tear and propagation pressure of a bleb using an in vitro porcine model.
Section snippets
Methods
Twenty porcine thoracic aortas, removed just distal to the arch, were obtained from a local abattoir in accordance with Canadian regulations. All were cut to approximately 17–19 cm in length to fit the pressurization apparatus, ensuring that the vessels would not become tortuous. Specimens of this size always had a minimum of four pairs of intercostal arteries. Excess connective tissue and fat were removed from the exterior of each vessel and any branches were tied off. The aortas were then
Results
A total of 16 specimens propagated, 1 ruptured, and 3 neither propagated nor ruptured. Blebs with tear depths between 0.44 and 0.89 were observed to propagate between pressures of 26.3 and 60.0 kPa. The artery that ruptured tore at the dissected wall, directly across from the location of the intimal tear at 46.7 kPa; this aorta is included in the data for dissections that did propagate. Its tear depth was 0.56±0.03. A summary of the maximum pressures reached for arteries that did not propagate or
Discussion
The dependence of propagation pressure on tear depth was expected since the thickness of the outer wall should determine the stress distribution in a dissection. An interesting result was the relationship between , . van Baardwijk and Roach (1983)showed that the number of medial elastin layers decreases linearly along the thoracic aorta in sheep, therefore L and d are not necessarily related. The total number of elastin layers in the intact wall at the propagating edges of these aortas ranged
Acknowledgements
We would like to thank Joy Dunmore-Buyze and Dr Ian MacDonald for collecting tissue specimens. This research was funded by the Medical Research Council of Canada.
References (13)
- et al.
The strength of the aortic media and its role in the propagation of aortic dissection
Journal of Biomechanics
(1990) - et al.
Aortic dissection
Annals of Vascular Surgery
(1995) - et al.
Pulsatile diameter and elastic modulus of the aortic arch in essential hypertensiona noninvasive study
Journal of American College of Cardiology
(1989) Aortic dissectionAnatomy, consequences, and causes
American Heart Journal
(1981)- et al.
Factors in the propagation of aortic dissections in canine thoracic aortas
Journal of Biomechanics
(1987) - et al.
Cited by (59)
In situ visualization of aortic dissection propagation in notched rabbit aorta using synchrotron X-ray tomography
2023, Acta BiomaterialiaCitation Excerpt :The values of critical pressures found in this study are coherent with literature [13,38–40]. The negative correlation between the notch depth and critical pressure observed in this study is also in agreement with the literature [14,41]. Peelukhana et al.[41] used a pulse duplication device to study the effect of different geometric parameters on aortic dissection propagation in porcine aortas with a single-entry tear, demonstrating that a deeper notch is more likely to propagate than a shallow notch for the same pressure.
Anatomy, Pathology, and Classification of Aortic Dissection
2021, Techniques in Vascular and Interventional RadiologyEffect of diabetes mellitus on the dissection properties of the rabbit descending thoracic aortas
2020, Journal of BiomechanicsBiomechanics of aortic wall failure with a focus on dissection and aneurysm: A review
2019, Acta BiomaterialiaRegional distribution of delamination strength in ascending thoracic aortic aneurysms
2019, Journal of the Mechanical Behavior of Biomedical MaterialsCitation Excerpt :The former involves an intimal-medial tear that occurs when hemodynamic stresses overcome the capacity of inner layers to withstand tensile stress, and the latter involves the catastrophic delamination of wall layers occurring when the bonding forces holding the layers together are overcome. Despite widespread consensus that propagation of aortic dissection is a biomechanical phenomenon and a number of relevant biomechanical studies on non-aneurysmal descending thoracic aortic tissue from animals (Prokop et al., 1970; van Baardwijk and Roach, 1987; Tam et al., 1998) and on human abdominal aortic tissue (Sommer et al., 2008; Tong et al., 2014), remarkably few studies on the more relevant ATAA tissue have been published (Pasta et al., 2012; Shahmansouri et al., 2016). Furthermore, it is unclear whether the delamination properties of ATAAs are region-specific or common in all aortic quadrants.
A combined experimental-numerical lamellar-scale approach of tensile rupture in arterial medial tissue using X-ray tomography
2019, Journal of the Mechanical Behavior of Biomedical Materials