Chapter 262. Diseases of the Aorta

1. What is the normal size of the aorta, common femoral artery, iliac artery, and popliteal artery?

2. What do the American College of Cardiology and American Heart Association Guidelines recommend for abdominal aortic aneurysm screening?

3. What is the preferred classification system for aortic dissection?

4. When should large vessel vasculitis be suspected?

5. What are the causes of blue toe syndrome and what is the diagnostic modality of choice?

Acute and chronic aortic syndromes have been the subject of intense investigation by physicians for centuries. These examinations have yielded a wealth of knowledge about the pathology, pathobiology, and pathophysiology of diseases of the aorta. More recent technological advancements have significantly improved our understanding of aortic syndromes at the molecular level, and have also helped in their accurate and timely initial diagnosis and long-term management. In addition, large clinical databases have elucidated the epidemiology and furthered the understanding of the natural history of many different aortic syndromes. However, despite the current armamentarium of knowledge and technology at the physician's disposal, the accurate diagnosis of acute aortic syndromes is not always apparent, sometimes with disastrous consequences. This chapter will focus on the presentation, diagnosis, and management of the various forms of acute and chronic aortic diseases, including aortic dissection and its variants, abdominal and thoracic aneurysms, multiple atheromatous embolization, giant cell and Takayasu arteritis, and blue toe syndrome (Figures 262-1 and 262-2).

Pathophysiology

Acute aortic disorders include acute aortic dissection and its variants of intramural hematoma and penetrating atherosclerotic ulcer. All of these represent disruptions of one or more of the three layers of the aorta: the innermost intimal layer; the middle layer, or media; and the outermost adventitial layer. The intima is a very thin, endothelial-lined layer in its luminal portion, and it is prone to traumatic insults. The media is thick walled and contains multiple layers of elastic laminae (elastin, fibrin, collagen) and smooth muscle cells. The adventitia is primarily composed of collagen that helps to anchor the aorta to it surroundings, and also contains the vasa vasorum that functions to deliver blood to the outer aortic wall and to the media. The common pathway in all three acute aortic syndromes is a preceding weakening of the layers of the aorta that may lead to a tear in the intima, as in the case of dissection; rupture of the vasa vasorum, which leads to aortic infarction but with intact intima, as in the case of intramural hematoma; and atherosclerotic ulcer, which penetrates into the adventitia with surrounding hematoma. The weakening of the aortic layers occurs via various mechanisms including atherosclerosis, inflammation, cystic medial necrosis (deposition of mucoid material), disruption of the ...