Variations in branching pattern, shape, size and relative distances of arteries arising from arch of aorta.

Hundred aortic arches were studied in adult cadavers (aged 40-70 years) for variations in the origin of branches at arch of aorta in situ and for observing the lumenal diameters and relative distances between the adjacent branches. Usually described three branches arising at arch of aorta were observed in 77.0% specimens. Two branches arising from arch of aorta, having different branching pattern were observed in 12.0%:--(i) BC trunk; left brachiocephalic which divided into right common carotid and right subclavian (ii) common origin of BC and LCC; LSC. (iii) common origin of BC and LCC; common origin of LSC and left vertebral. While, four branches were observed in 11.0% showing separate openings:--(i) BC; LCC; LV; LSC (ii) BC; thyroid ima; LCC; LSC (iii) BC, mediastinal; LCC; LSC. At the lumenal surface of the arch of aorta the lumenal openings showed a similar pattern corresponding to the arterial branches on the external surface. These openings were oval in shape in 90.0% with the mean maximum anteroposterior diameters being greater than the mean maximum side-to-side diameters (p < 0.001), while they were elliptical in 10.0%. The BC artery showed largest size followed by LSC and then LCC in most of the branching patterns (p< 0.001). The mean transverse distances between adjacent lumenal openings of these branches were significantly greater than the mean vertical distances (p < 0.001). Approximation of LCC to BC trunk was seen in 10.0% specimens. These observations may be important while invading the arch of aorta and its branches by instruments, as all areas are now susceptible to surgical attack.