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Acute Aortic Disease.. - Index of

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Classification <strong>of</strong> <strong>Aortic</strong> Dissection 11<br />

Figure 5 Differentiation <strong>of</strong> classes one to five <strong>of</strong> aortic dissection. (Class 1) classic aortic<br />

dissection with true and false lumen without communication <strong>of</strong> the two lumina; (Class 2)<br />

intramural hemorrhage or hematoma; (Class 3) ulceration <strong>of</strong> aortic plaque following plaque<br />

rupture; (Class 4) subtle or discrete aortic dissection with bulging <strong>of</strong> the aortic wall;<br />

(Class 5) iatrogenic or traumatic aortic dissection, illustrated by a catheter-induced separation<br />

<strong>of</strong> the intima. Source: From Ref. 55.<br />

noncommunicating dissections are not uncommon (45–51,57). In an autopsy study,<br />

dissecting aneurysms without tears were found in up to 12% <strong>of</strong> 311 autopsies (58).<br />

Others have reported an incidence <strong>of</strong> 4% in 505 cases (59). In a series <strong>of</strong> sudden<br />

deaths, 67% <strong>of</strong> patients with dissections did not have tears (60). The dissection<br />

can spread from diseased segments <strong>of</strong> the aortic wall in an antegrade or retrograde<br />

fashion, involving side branches and causing other complications.<br />

IMH (Class 2)<br />

An IMH is probably the initial lesion in the majority <strong>of</strong> cases <strong>of</strong> cystic medial<br />

degeneration. This leads to localized aortic dissection, in which the intimal tear<br />

seems to be secondary to preceding intramural hemorrhage (45–48). IMH may be<br />

the result <strong>of</strong> ruptured normal-appearing vasa vasorum, which are inadequately<br />

supported by the surrounding aortic media or the result <strong>of</strong> rupture <strong>of</strong> diseased vasa<br />

vasorum. As a dissection, the hematoma can extend longitudinally along the aorta.<br />

The weakened inner wall is subjected to the elongating force <strong>of</strong> the diastolic recoil,<br />

which can result in intimal tears only visible at surgery or autopsy. Differences in<br />

elasticity between the aortic fibrous adventitia and the inner more elastic media<br />

may play an additional role (59). The prevalence <strong>of</strong> IMH in patients with suspected<br />

aortic dissection, as observed by various new imaging techniques, is reported in<br />

the range <strong>of</strong> 10% to 30% (45–50). There are two distinct types <strong>of</strong> IMH: type I<br />

shows a smooth inner aortic lumen, the aortic diameter is usually less than 3.5 cm,<br />

and the wall thickness greater than 0.5 cm. Echo-free spaces are found in only

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