Anatomical Branching Patterns of the Aortic Arch in Ethiopia: An Imaging-based Study

Haile Tesfamariam1, Peter Etim Ekanem1, Birhane Alem1, Anne Caroline Kendi Nyaga2

1. Department of Anatomy, College of Health Sciences, Mekelle, Ethiopia  

2. Department of Pediatrics and Child Health, College of Health Sciences, Mekelle, Ethiopia  

Correspondence to: Dr. Peter E. Ekanem. Email: etim_akpan@rocketmail.com 

Received: 2 Nov 2020; Revised: 16 Jul 2021; Accepted: 26 Jul 2021; Available online: 3 Sep 2021

Abstract

Background: The aortic arch (AA) is a key anatomical vascular structure through which blood is distributed to the body’s organs. Knowledge of its branching patterns is important for surgical procedures. This study aimed to describe anatomical variations in the branching patterns of human AAs in patients who underwent chest contrast-enhanced computed tomography. Methods: A retrospective study involving 630 chest contrast-enhanced computed tomography scans from July 2018 to July 2019 was carried out at Ayder Comprehensive Specialized Hospital, Mekelle, Ethiopia. These images were reviewed for AA branching patterns and classified accordingly. Data were analyzed using SPSS version 21. Results: Of the 630 patients (364 males and 266 females), AA branching pattern variations were found in 35.2%: type II, 26%; type III, 6.5%; type V, 2.7%; the rest, 64.8%, had a normal (type I) AA branching pattern. The left vertebral artery and the aberrant right subclavian artery were also observed to originate directly from the AA. Conclusions: AA branching pattern variation types II, III, and V were found in our study. These findings could be vital during aortic instrumentation and surgical procedures of the head and neck in Ethiopia and globally.

 

Keywords: Anatomical variants, Aortic arch, Branching patterns, Surgical procedures


Ann Afr Surg. 2021 ; 18(4): 235-240 
DOI: http://dx.doi.org/10.4314/aas.v18i4.9
Conflicts of Interest: None
Funding: None
© 2021 Author. This work is licensed under the Creative Commons Attribution 4.0 International License 

Introduction

The aortic arch (AA) is the curved continuation of the ascending aorta supplying the head, neck, and the upper thoracic region (1). Its normal branching pattern, which occurs in 64.9 to 94.7% of the population, is (from proximal to distal) from the brachiocephalic trunk (BT), to the left common carotid artery (LCC), and finally, to the left subclavian artery (LS) (2-4). Occasionally, this vascular pattern may vary (5). This can be explained by the persistence of AA segments that normally regress, the disappearance of segments that would otherwise remain, or both (5,6). Variations of the AA may cause dyspnea, dysphasia, intermittent claudication, changes in cerebral hemodynamics, misinterpretation of radiological examinations, and complications during neck and thorax surgery (7). This is important both for diagnostic value and before surgery of supra-aortic arteries (8).  AA variant branching patterns are most commonly studied using cadaver dissection and radiology. Comparisons of studies carried out in China, Greece, Turkey, and Kenya revealed an almost similar number of variation types despite using the different study methods (9-13). Prevalence of these variations also differs among populations. A South Australian cadaveric study reported a prevalence of 7.41% (14), whereas the prevalence was 11.67% in China (9) and 20% in Nepal (15). The prevalence is reportedly higher in African populations (up to 49.7%) (6). Despite the varying prevalence of AA branching pattern variations, this has not been studied in Ethiopia. The present study intended to investigate the variations in branching patterns of the AA in Ethiopian populations that may be important for surgical planning and endovascular procedures.

Materials and methods

Study setting and design 

This study was conducted in Ayder Comprehensive and Specialized Hospital (ACSH), Mekelle, Ethiopia. ACSH is Ethiopia’s second-largest referral hospital and serves a wide catchment population of more than 8 million people.

A retrospective study was carried out to determine the variations in AA branching patterns among patients who underwent contrast-enhanced computed tomography (CECT) of the chest for various indications. The data collection period was between July and August 2019.

Inclusion criteria 

All patients who had undergone CECT of the chest from July 1, 2018, to July 30, 2019, and with complete chest CT scans (including the supra-aortic vessels superior to the diaphragm) were included in the study population.

 

Exclusion criteria

Patients who underwent CECT of the chest with incomplete information, had marked motion artifact in the region of interest (difficult to visualize AA vessels), no AA images available for review, and had a prior arch reconstructive surgery were excluded from the study.

 

Sampling procedure

Convenience sampling, aimed at including the maximum number of patients within the limited data collection period available, was utilized. Data were obtained from the hospital’s Picture Archiving and Communication System. All patients who had undergone chest CECT and fit the study criteria were included.

 

AA branching pattern variations and classification 

The classification of AA variation in this study was adapted from the Natsis classification (10), which is also radiology based: type I: BT, LCC, and LS; type II: BT with LCC and LS; type III: BT, LCC, left vertebral artery (LV), and LS; type IV: right subclavian artery (RS) and carotids in common–LS; type V: carotids in common–LS, RS; type VI: carotids and subclavians in common; type VII: RS, right common carotid artery (RCC), LCC, and LS; type VIII: BT, thyroidea ima, LC