Prevalence of aortic arch anatomical branching variants in Kenyan population as shown on contrast enhanced chest multidetector computed tomography (MDCT) a cross-sectional study done at the Radiology Department Of Kenyatta National Hospital

Abstract

Introduction The classical or normal anatomical aortic arch (AA) is left-sided and the commonest branching pattern of the AA comprising of three vessels. These are the brachiocephalic trunk (BCT), the left common carotid artery (LCCA), and the left subclavian artery (LSCA) from right to left. The BCT branches into the right subclavian artery (RSCA) and right common carotid (RCCA). This branching pattern occurs in 64.9 – 94.3% of the population as reported in literature and is described as normal, conventional or classical. Anatomical branching variants of the AA include differences in the origins of different branches and the number of branches. The non-classical AA branching variants have been found to be associated with a higher occurrence of congenital cardiovascular malformations amongst these patients. Objective The objective of the study was to determine the aortic arch anatomical branching variants present in our Kenyan population as shown on contrast-enhanced multidetector CT chest. Rationale Knowledge of these branching patterns is important to interventional and diagnostic radiologists, anatomists, vascular, thoracic and neck surgeons. The mentioned specialists should recognize these patterns to avoid fatal outcomes during supra aortic thoracic, head and neck surgeries. Study Setting Kenyatta National Hospital (KNH) department of Radiology Study Design A prospective cross-sectional study Sample Size The number of subjects included in the study was 185 Methodology A total of 185 subjects were recruited into the study. The gender distribution was 99 (53.5%) females and 86(46.5%) males. The study participants were recruited, following ethical approval by KNH-UoN ERC and informed consent from patients who presented themselves for contrast enhanced chest computed tomography for varied indications at the Department of Radiology KNH. Axial chest scans were obtained and the raw data was subjected to volume rendering technique (VRT) and multiplanar reconstruction (MPR) software to define the anatomy of the AA. xiii The type of the branching pattern was recorded in a designed data collection form and stored for data analysis. Pictures of the branching patterns were archived. Data Analysis Data analysis involved calculating the frequency distributions of the AA variations using Statistical Package for Social Sciences (SPSS) version 21 software. Study Duration The study was carried out in 6 months (between May and November 2016) .Results The mean age of the participants was 50.7 years (SD ± 18.4). The mean age of female participants was 49.2 years (SD ± 19.4) and the mean age of male participants was 52 years (SD ± 17.9). The majority of participants 95 patients (51.3%) had classical AA Natsis type I. The remaining 90 participants (48.6%) had non-classical variant AA. Of these 83 participants (44.9%) had 2 branch pattern Natsis type II. Four patients (2.3%) had a four branch pattern AA where LVA originated directly from the AA (Natsis type III). The remaining 3 participants (1.6%) had a variant AA not classified under Natsis. These had AA with 3 branches i.e. BCT (giving off LCCA), LVA and LSCA (i.e. Natsis type II with an additional LVA.) Conclusion Variations in the branching pattern of AA are very common as shown in this study.