Thymic artery: uncommon origin from proximal aortic arch or distal ascending aorta

Internal thoracic and inferior thyroid arteries mainly supply the thymus. However, very few studies have been reported on the arterial variations of the thymus. The first author, a cardiac surgeon, happened upon a thymic artery arising from either proximal aortic arch or distal ascending aorta in a few cases during routine cardiac surgery in infants and neonates. Hence a study on the prevalence of the variant thymic artery during open heart surgery was contemplated, as knowledge of its presence could avoid its injury during surgical and diagnostic procedures of the region. The prevalence of the variant thymic artery was observed during 100 consecutive cardiac surgeries in infants and neonates. In addition to two branches from internal thoracic and inferior thyroid arteries, a thymic artery originating from the distal ascending aorta or proximal arch was found in 15 (15%) out of 100 patients who underwent open heart surgery for the correction of congenital heart defects. The artery took origin from the anterior surface of aorta, a little to the left. These were small arteries, single in origin, which started at right angles from the aorta and pierced the pericardium at its reflection, from visceral to parietal, to reach the posterior surface of the thymus where they divided into two branches, one for each lobe. Since this variant artery was present in 15% cases, being aware of its presence can help prevent troublesome bleeding during surgical thymectomy, and more importantly, during surgical and diagnostic interventions in the mediastinum.