Clinical case: Chronic thoracic aneurysm

History and physical exam

A 47-year-old white Australian man presented to the emergency department with chest tightness and shortness of breath. He stated he did not have symptoms of fever, cough, or night sweats. Initially, his medical history seemed unremarkable. However, at the age of 18, he had been the driver in a single automobile accident in which his car had hit a pole at high speed and the patient had sustained bilateral pneumothoraces, liver lacerations, and splenic rupture requiring splenectomy. He had been using a seatbelt. At that time there was no indication of an injury of the arch of the aorta (Figure 1).

The patient had not been admitted to a hospital since that accident and was otherwise noted to be healthy. The patient did not have risk factors for cardiac disease or pulmonary embolism and did not have any family history of aneurysma or cardiac disease.

On examination, his temperature was 36.5∘C, heart rate 76 bpm, blood pressure 139/64 mmHg, and saturation 98% on air. Chest and abdominal examination were unremarkable.

Imaging

A chest X-ray (CXR) showed clear lung fields with a cardiothoracic ratio within the normal range (Figure 2). There was however a smooth enlargement of the left hilum on CXR, thought to be due to an enlarged main pulmonary artery.

Subsequent computed tomography (CT) imaging of the chest revealed however a 5.4 cm saccular thoracic aneurysm of the aortic arch near to the origin of the left subclavian artery (Figure 3). The presence of peripheral calcifications (Figure 3A, B) in the aneurysm suggested that it was long-standing and therefore an unlikely cause of the patient’s acute symptoms, which remained unknown. There was no indication of perianeurysmal fluid accumulation and no evidence of rupture of the aneurysm.

CT angiogram of the thoracic aorta confirmed the findings and suggested that the proximal margin of the aneurysm lay adjacent to the posterior wall of the left subclavian artery and was 19mm downstream from the posterior wall of the left common carotid artery. The region of the aorta that contained the aorta is known as the isthmus of the aorta.

Diagnosis and management

The patient’s past history of trauma was believed to be the most likely cause of his aneurysm. Despite being slightly hypertensive at presentation, there were no subsequent concerns about the patient’s blood pressure. He was relatively young and had no history of systemic inflammatory disease. Examination was not consistent with Marfan syndrome and his history was not consistent with a chronic infectious state such as syphilis, and his inflammatory markers were normal. Furthermore, the patient had no documented history suggestive of atherosclerosis. Lastly, the aneurysm’s saccular shape and position were typical of those found in chronic traumatic thoracic aortic aneurysms.

Six weeks after his initial examination, the patient underwent elective thoracic endovascular aneurysm repair (TEVAR) with debranching of the left aortic arch by right carotid to left carotid to left subclavian bypass - the surgeons placed a stent in the arch of the aorta. That stent practically sealed the aortic wall at the distal arch and blocked the opening of left carotid and left subclavian arteries. To alleviate that problem, the surgeons installed a bypass graft that connected the right carotid to the left carotid and left subclavian arteries superior to the arch of the aorta. Thus left carotid and left subclavian receive blood from the right carotid artery and not directly from aorta.

Evolution

At twelve weeks after the procedure, the patient returned to his job as an emergency department nurse and at nine months postoperative his health remains well.

Causes, signs, and symptoms 

The arch of the aorta arises from the left ventricle and passes to the left and typically gives rise to three major vessels, the brachiocephalic trunk and then the left common carotid and left subclavian arteries (Figure 1+x). Aneurysms of the isthmus of the aorta (see objective 5), as in the case described here, are typically found in individuals above 60 years old. The ligamentum arteriosum (Figure 1) is associated with the arch of the aorta. It is the remnant of the ductus arteriosus and passes from the pulmonary trunk to the isthmus of the aorta arch.

Rapid deceleration and the application of shearing forces may result in thoracic aortic injuries, typically at the isthmus. The vulnerability of this anatomical area is believed to be related to the tethering of the descending aorta by the ligamentum arteriosum; however there may be additional reasons for the sensitivity of this region.

Patients who have chronic traumatic aortic aneurysms may present with nonspecific signs including haemoptysis, thoracic pain, hoarseness, and back pain.

Management

There are few guidelines available that are specifically concerned with the management of chronic thoracic aneurysms. In the majority of cases, management should be similar to that of thoracic aneurysms of other causes, in which surgical intervention is considered based upon patient symptoms and documented radiological enlargement. In the case described here, a decision was made for surgical intervention due to the patient’s relatively young age and anxiety about his diagnosis. The minimally invasive TEVAR technique involves inserting a catheter through the femoral artery and the implantation of a stent graft within the aneurysm under imaging guidance.