The aortic isthmus is the point where the aortic arch joins the thoracic descending aorta, adjacent to the ductus arteriosus and the arterial ligament area. The aorta is the thickest arterial vessel in the body and is the mainstay of the body circulation. The aorta emanates from the left ventricle and travels anteriorly and superiorly to the right via the right side of the pulmonary artery to the height of the second right sternocostal joint where the ascending aorta is located. Here the aorta turns posteriorly to the left in an arch shape and reaches the left side of the lower edge of the fourth thoracic vertebral body, and this segment is the aortic arch. It then turns to travel inferiorly and descends along the anterior aspect of the spine to the height of the twelfth thoracic vertebral body and enters the abdominal cavity through the aortic fissure of the diaphragm; this segment is the descending aorta. Where above the diaphragm to the fourth thoracic vertebra is the thoracic aorta, and below the diaphragm to the fourth lumbar vertebra is the abdominal aorta. Therefore, the specific location of the aortic isthmus is the connection between the aortic arch and the thoracic aorta on the left side of the lower edge of the fourth thoracic vertebral body, which is the narrowing part of the aorta and is the best location for aortic disease.