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Essentials of Diagnosis
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- Ascending aortic diameter > 4 cm on imaging study.
- Descending aortic diameter > 3.5 cm on imaging study.
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General Considerations
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In the ascending aorta, aneurysms tend to take on three common patterns, as indicated in Figure 37–1. These include the supracoronary aortic aneurysm, annuloaortic ectasia (marfanoid), and tubular diffuse enlargement.
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The most common pattern is that of supracoronary dilatation of the ascending aorta. In this pattern of disease, the short segment of aorta between the aortic annulus and the coronary arteries remains normal in size. Sinuses are “preserved,” meaning that the aorta indents normally, forming a “waist,” near the level of the coronary arteries. For this type of aneurysm, a supracoronary tube graft suffices.
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In the second type, annuloaortic ectasia, the aortic annulus itself becomes dilated, giving a shape to the aorta like an Erlenmeyer chemistry flask. In this type of disease, the segment of aorta between the annulus and the coronary arteries is diseased, dilated, and thinned. Sinuses are “effaced,” meaning that the normal indentation, or waist, is lost. When surgery is required, the entire aortic root must be replaced.
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In the third type of ascending aortic disease, the configuration is midway between the previous two patterns, that is, there is some dilatation of the annulus and root and some effacement of the sinuses, but these elements are not dramatic. The overall appearance is that of a large tube, rather than a flask. For such aortas, either supracoronary tube grafting or aortic root replacement may be appropriate.
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The Crawford classification (Figure 37–2) is used to categorize the appearance of an aneurysm in the descending aorta and thoracoabdominal aorta. This classification is based on the longitudinal location and extent of aortic involvement, has implications for surgical strategy, and affects the risk of perioperative complications.
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Type I aneurysms involve most of the thoracic aorta and the upper abdominal aorta. Type II aneurysms, the most extensive and most dangerous to repair, involve the entire descending and abdominal aortas. Type III aneurysms involve the lower thoracic and abdominal aortas. Type IV aneurysms are predominantly abdominal but involve thoracoabdominal exposure because of the proximity of the upper border to the diaphragm.
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The genetics of Marfan disease, a well-known cause of aneurysms of the thoracic aorta, have been well delineated, with over 600 mutations identified at one locus on ...