5.8 days

MEDICAL: Peripheral Vascular Disorders with CC 110

9.1 days

SURGICAL: Major Cardiovascular Procedures with CC

^K thoracic aortic aneurysm is an abnormal widening of the aorta between the aortic valve and the diaphragm. An aneurysm is defined as dilation of the aorta that is more than 150% of its normal diameter for a given segment. A diameter of greater than 3.5 cm is generally considered dilated for the thoracic aorta, whereas greater than 4.5 cm would be considered aneurysmal.

Thoracic aneurysms account for approximately 25% of all aneurysms, and approximately 25% of people with thoracic aneurisms also have abdominal aneurysms. Although aneurysms may be located on the ascending, transverse (aortic arch), or descending part of the aorta or may involve the entire thoracic aorta, they commonly develop between the origin of the left subcla-vian artery and the diaphragm.

Aneurysm formation is caused by a weakening of the medial layer of the aorta, which stretches outward, causing an outpouching of the aortic wall. Thoracic aortic aneurysms take four forms: fusiform, saccular, dissecting, and false aneurysms (Table 1). Dissection of the aorta can occur with or without an aneurysm but is most often associated with the presence of a preexisting aneurysm. Thoracic aortic aneurysms may lead to serious or fatal complications if they are left untreated. For example, a thoracic dissecting aneurysm may rupture into the pericardium, thus resulting in cardiac tamponade, hemorrhagic shock, and cardiac arrest.

888 Thoracic Aortic Aneurysm

• TABLE 1 Forms of Thoracic Aortic Aneurysm
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