26 - Anatomical Variations in the Branching of the Aortic Arch: A Cadaveric Study

Poster Board Number: 26
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Abstract Body : Background: The aortic arch (AA) traditionally has three major vessel branches, the brachiocephalic trunk (BCT), the left common carotid artery (LCCA) and the left subclavian artery (LSA). However, several variations have been reported including a common trunk for the BCT-LCCA (bovine arch), direct branching of the left vertebral artery, and an aberrant right subclavian artery. Further subtype classification (I, II and III) can be performed for three-vessel arches based on the distance from the apex of the AA and origin of BCT. Assessing the prevalence and comparing types of AA variations with detailed mapping of vessel orientation would add to the literature and solidify practical knowledge for surgery applications, radiologic directed interventions, and prosthetic development.
Methods: Traditional dissection of forty-eight formalin-embalmed cadavers thoracic cavities exposed the thoracic aorta, including the ascending aorta and arch. On examination, the aortic arch vessel patterns were recorded as either traditional three-vessel branching or specific anatomic branching variation (e.g., bovine). Three-vessel arches were further sub-classified as type I, II, or III. To understand orientation, each arch was measured from photos using Image-J software for vessel diameter, angle of branching, and distance between branches. Physical measurements with tape for torsion were also performed.
Results: The prevalence of both traditional and variation arch patterns was calculated. Furthermore, a heatmap was produced to highlight features more common to each branching pattern, utilizing the data from the vessel location and angle off of the aorta. 60% of the AAs examined in the study showed a traditional three-vessel branching pattern, consistent with the lower range of this pattern seen in the current literature. The prevalence of three-vessel arch subclassifications was type I in (69%), type II in (17%) and type III in (14%). The most common variation identified was the bovine arch which represented 36% of cases, this result was reflective of its known prevalence. Four AAs had a direct branch of the left vertebral artery just proximal to the LSA, with three also having a bovine trunk. A single arch with an aberrant right subclavian artery was also identified.
Conclusion: The percentage of traditional and bovine arch variations of the aorta observed helps to further confirm their accepted range, consistent with previous findings. However, given the small number of type II, type III, direct vertebral artery and aberrant subclavian artery AA variations, it would be helpful to expand the dataset with a larger sample size to further elucidate the branching characteristics of these variations. While the variations discussed in this study have been seen before, information regarding the orientation and characteristics of the major vessels for each classification is lacking. The heatmap produced elucidates more specific common features of aortic vessel variations that may be encountered by practicing clinicians.
Significance: A detailed understanding of aortic arch variations is essential for surgeons operating in the region and for the future development of prosthetics for aortic arch repair. Further classifying each type and variation of the AA with greater detail about vessel orientation will provide surgeons with a greater knowledge of varying anatomy.