Endovascular creation of aortic dissection in a swine model with technical considerations

Creating an experimental model of a type B aortic dissection with a minimally invasive endovascular procedure in swine to help future evaluation of therapies for aortic dissection.

Aortic dissection was created in 14 swine using endovascular procedures only. Under fluoroscopy, a modified 10F outer catheter with a 14 G stiffening inner metallic cannula was forced via the femoral artery into the aortic vessel wall to create an initial dissection. A .035-inch guidewire and a 4F straight catheter were advanced into the dissected space, and the dissection was extended in a retrograde direction using a technique including loop formation of the guidewire, which was placed carefully against the transmural penetration and extended as far as possible in the descending thoracic aorta up to the point where loop formation of the guidewire reached smoothly. An 8F introducer sheath was advanced with a Brockenbrough needle into the dissected space, and a proximal fenestration was created by puncturing the intima. If required, balloon dilatation was performed to enlarge the proximal and distal tears. Aortography and contrast-enhanced cone beam computed tomography (CBCT) were performed in addition to a detailed histologic evaluation of the dissected portion.

Aortic dissection was successfully created in 11 of the 14 swine (78.6%). Among the 11 dissections, nine were located in the thoracoabdominal aorta and two in the abdominal aorta. The initial aortic diameter at the middle portion of the created dissection ranged from 7.4 to 16.8 mm (mean ± standard deviation, 10.9 ± 2.9), while after dissection, it ranged from 7.8 to 19.3 mm (12.9 ± 3.8 mm). The dissected length ranged from 4.4 to 17.7 cm (10.7 ± 4.6 cm). Aortography and CBCT revealed seven dissections (63.6%) with a smooth and patent false lumen. Histologic evaluation revealed that the outer one-third of the media was separated from the inner two-thirds. In the remaining four dissections (36.4%), imaging procedures revealed the formation of a rough and patent false lumen beside the true lumen, and histologic evaluation revealed greater separation of the outer media. Five animals were chronic dissection models. Three (60%) of these survived for more than 14 days without any symptoms. Moreover, completely patent true and false lumens without thrombus formation were observed in these three animals. The aortic diameter at the dissected portion tended to be dilated compared with the initial diameter.

This new technique of creating an experimental aortic dissection model in swine is promising and should contribute to the development of future therapies for aortic dissection.