1. Introduction

    The mortality rate associated with thoracic aneurysms is well established. Patients with aortic dissections have only a 3-month survival time if they do not undergo surgical repair because the incidence of rupture is high. The refinement of synthetic grafts, surgical and perfusion techniques, and intraoperative management has contributed to improved surgical outcomes. Today the early mortality rate is thought to be less than 10%, demonstrating that elective surgical intervention is an acceptable means of treating thoracic aortic aneurysms.

2. Classification

    Aneurysms of the thoracic aorta may be classified with respect to type, shape, and location. Typically, aneurysms involving all three layers of the arterial wall, tunica adventitia, tunica media, and tunica intima are considered to be true aneurysms. In comparison, aneurysms that solely involve the adventitia are termed false aneurysms. The shape of the lesion can also serve as a means of characterizing aneurysms. Fusiform aneurysms have a spindle shape and result in dilation of the aorta. Saccular aneurysms are spherical dilations and are generally limited to only one segment of the vessel wall. Aortic dissection is the result of a spontaneous tear within the intima that permits the flow of blood through a false passage along the longitudinal axis of the aorta. Aneurysms can also be classified according to their location within the aortic arch. In addition, thoracoabdominal aneurysms can be classified into four types on the basis of their location.

3. Etiology

    Atherosclerosis is the most common cause of aneurysmal pathology. Atherosclerotic lesions occur most often in the descending and distal thoracic aorta and are most often classified as fusiform. Less common causes include the histologic contributions of cystic medial necrosis observed in patients with Marfan’s syndrome, infective and inflammatory processes within the vessel wall, and Takayasu’s arteritis. A genetic predisposition is thought to contribute to the development of aortic aneurysms.

4. Diagnosis

    The symptomatology of thoracic aneurysms is often related to the site of the lesion and its compression on adjacent structures. Pain, stridor, and cough may result from compression of thoracic structures. Symptoms related to aortic insufficiency may be observed in aneurysms of the ascending aorta. An upper mediastinal mass may be an incidental finding on conventional chest radiography in an asymptomatic patient. Further investigation with noninvasive methods (e.g., CT and MRI) can show the configuration and location of the aneurysm. Invasive aortography, although associated with a higher risk of complications, provides the most information because it allows evaluation of the coronary vessels and branches of the aortic arch.

5. Treatment

    Early detection and surgical intervention have made significant contributions to long-term survival. The surgical approach and mode of resection vary according to the location of the lesion within the thoracic aorta. Resection of the ascending aorta and graft replacement necessitate the use of CPB. The aortic valve may also require replacement. Surgical resection of lesions in the transverse arch compromises cerebral perfusion, although various bypass techniques combined with profound hypothermia and circulatory arrest have been used. Aneurysms of the descending aorta may be resected by application of an aortic cross-clamp. However, perfusion to distal organs can be compromised during this procedure. Endovascular thoracic aortic repair is also an option.