Aortic Arch Morphometry and its clinical implication –A computed tomography study

Aortic arch is a challenging site for endovascular repair. In the present study morphometric details of aortic arch such as aortic arch angle, aortic arch type and angle of aortic arch curvature were observed with an objective to provide normogram of these parameters for north indian population as the literature is lacking with these values. These parameters were corelated with age and gender also. It is a pilot study of its own kind. Research Article Aortic Arch Morphometry and its clinical implication –A computed tomography study Hema Nagpal1*, PK Sharma2, Jyoti Chopra3 and Rajni Patel4 1Assistant professor, Department of Anatomy, SIMS,Hapur, UP, India 2Professor and Head, Department of Anatomy, ERA Medical College, Lucknow, UP, India 3Professor, Department of Anatomy, King George’s Medical University, Lucknow, UP, India 4Associate professor, dept of anatomy, SIMS, HAPUR, UP, India Received: 19 July, 2018 Accepted: 31 July, 2018 Published: 01 August, 2018 *Corresponding author: Hema Nagpal, Assistant professor, Department of Anatomy, SIMS, Hapur, UP, India, E-mail:


Introduction
Aorta is the main arterial trunk that delivers oxygenated

Materials and Methods
The present study was conducted on 55 patients, including 31 males and2 4females. The patients underwent computed tomographic angiographic scan for various indications, were included in the study. Age of subjects ranged from 3 months to 75 years across 5 age groups. Written informed consent from the patients was obtained. The images of patients with previous history of allergy to contrast agent, renal insuffi ciency,distortion of anatomy of arch of aorta due to any pathology were excluded from this study. A region of interest was drawn on the aorta at the level of the diaphragm. After an appropriate delay to allow passage of the contrast agent into the renal arterial circulation, a series of thin cuts (0.9mm) were obtained throughout the aorta. Morphometry of arch of aorta were studied in axial, multiplanar reconstructions (MPR) images, and in volume rendered images.
The parameters observed were:  I, II and III in which the vertical distance from the origin of the brachiocephalic trunk (BCT) to the top of the arch in parasaggital image was measured,if this distance was less than the diameter of LCA it was termed Type I arch,if the distance was less than double of diameter of LCA but more than its diameter this was labelled as Type II; and if the distance was more than the double of diameter of LCA it was termed Type III arch [2] (Figure 2).
3. Angle of aortic arch curvature-It was the angle formed by aortic arch from coronal plane in axial view ( Figure 3).

Results
Age of subjects ranged from 3 months to 75 years across  where Type II was more common as compared to other types, in all other age groups Type I was the most common type.
Statistically there was no signifi cant difference in type of aortic arch in different age groups and gender (p>0.05) (Table 3, Figure 5).
Angle of aortic arch curvature to the coronal plane was studied in 55 subjects and it was found to range from 30 o to 77.6 o with a mean value of 58.1 o ±8.3 o . Among different age groups, the mean was found to be maximum in age group 61-75yrs (63.0±8.8 o ) and minimum in age group 0-15yrs (52.6±10.4 o ), however, the difference in different age groups was random in nature and did not account for a signifi cant difference statistically (p=0.139). Gender wise, males had a higher mean value as compared to females yet the difference was not signifi cant statistically (p=0.338). As age and gender wise differences were not signifi cant, hence the normative range for entire sample could be proposed as representative of all age and gender groups (Table 4, Figure 6).    In the present study there was a great difference between the minimal and maximal values of aortic arch angle (46.40° and 85.50°), which points towards a signifi cant variability in steepness of aortic arch. These values are comparable with the result of Demertzis et al. who found it between 43° -80° [3]. We also studied the effect of age and gender on aortic arch angle and found that it did not show any signifi cant relation with age but in females it was wider than males but this difference was statistically non-signifi cant.Aortic arch angle represents the steepness of aortic arch, so less the angle, more the steepness, resulting into more diffi culty in interventional maneuvers for supra-aortic artery.
In the present study, we found type I arch to be more frequently presented (n=26, 68.42%) followed by type II (n=11, 28.95%) and only one (n=1,2.63%) aortic arch was categorized as Type III. Whereas Demertzis et al. observed Type I aortic arch in 47%, type II in 36% and type III in 17% patients [3]. Liu also found type I arch in 44.7%, type II arch in 31.4%, type III arch in 23.9% of cases [4]. The prevalence of type I arch was quite high and that of type III arch was quite low in present study. In the present study type 1 was the most common type in all age groups except for age group >60 years, where type II was more common. This fi nding was similar to the fi nding of    Liu [4]. Although aortic arch type did not show any signifi cant corelation with age and gender (p>0.05) as also observed by Demertzis et al. [3].
The aortic arch type gives an additional impression of steepness of the aortic arch [2].The type III arch was correlated to the maximum grade of diffi culty in interventional maneuvers .We found type I to be most common in our study so there should be minimum diffi culty of interventional maneuvers for supra-aortic artery access in our population. So this study provides a basic anatomical information to catheterize aortic arch and its branches for safely performing endovascular surgery.