Contemporary Reviews in Cardiovascular Medicine Medical Therapy of Thoracic Aortic Aneurysms

An aneurysm is defined as a localized dilatation of a vessel of 50% of the normal diameter and includes all layers of the given vessel.1 Aortic aneurysms are divided into thoracic aortic aneurysms (TAAs), thoracoabdominal aortic aneurysms (a thoracic aneurysm extending into the abdomen), and abdominal aortic aneurysms (AAAs). Abdominal aortic aneurysms are reportedly more common than TAAs. Demographic studies have suggested that among people 65 years of age, the prevalence of AAA is 2.5%.2 Occurring at a rate of 4.5 to 5.9 per 100 000 person-years, TAAs are less common.3 Aortic aneurysms (TAA and AAA together) remain the 13th leading cause of mortality in Western countries4 and are probably responsible for 15 000 to 30 000 deaths per year in the United States.5 TAAs are classified into 4 general anatomic categories: ascending aortic aneurysms (60%), aortic arch aneurysms (10%), descending aortic aneurysms (40%), and thoracoabdominal aneurysms (10%). It is important to understand the development, pathogenesis, and clinical course of aortic aneurysms and to develop strategies that reduce its occurrence, progression, and mortality. This review summarizes our present understanding of the available medical therapies for aortic aneurysms and attempts to determine whether medical therapy for TAA is currently a viable option. We focus on TAAs whenever possible; however, it should be mentioned that the available literature for TAA is limited, and most of the preclinical data are obtained from AAA animal models. Therefore, we use AAA data with the caveat that it is unclear that extrapolating from AAA data leads to correct conclusions regarding TAA. There is significant heterogeneity in the aorta and aortic aneurysms in terms of their epidemiology, structure, mechanics, and biochemical systems.6 Although animal models of TAAs have been described7,8 and studied intensively, it is unclear how relevant they are to the basic and clinical pathology in humans because they involve either a genetic defect that has not been described in humans or the surgical creation of thoracic aneurysms, respectively.