Acute aortic syndromes: Time to talk of many things

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“The time has come,” the Walrus said,
“To talk of many things:
Of shoes—and ships—and sealing-wax—
Of cabbages—and kings—
And why the sea is boiling hot
And whether pigs have wings.”

—Lewis Carroll, The Walrus and the Carpenter (from Through the Looking-Glass and What Alice Found There , 1872).

Lewis Carroll's poem of 1872 is a useful starting point for identifying issues resulting from confusion over the variously described acute aortic syndromes—and, for oysters, the dangers of listening to walruses.

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In cases of aortic dissection (splitting or separation of the layers of the aortic wall), it is important to establish the type (ie, the location and extent) and class (ie, the structure) of the dissection, because these distinctions determine the treatment. 1 Similarly, in cases of painful or leaking degenerative aneurysms, we need to know the location of the aneurysm and whether the presenting pain is from compression of surrounding tissue, particularly of the vertebral bodies, or from leakage.

The location and extent of an aortic dissection can be classified in three ways (see Figure 3 in Smith and Schoenhagen’s excellent review of the use of computed tomography [CT] in acute aortic syndromes in this issue of the Cleveland Clinic Journal of Medicine 2):

  • The DeBakey system (type I, II, or III)
  • The Stanford system (type A or B)
  • Distal or proximal to the left subclavian artery.

Of note, the DeBakey system does not include tears in the arch that extend distally without ascending involvement. The original Stanford system included arch tears with distal extension in type B; hence, type B excluded all patients without ascending involvement.

The importance of the extent of dissection is that most patients with Stanford type A or DeBakey type I or II dissections should undergo immediate surgery, as most of them would die without it. Surgery is also indicated for arch tears (non-DeBakey, original Stanford type B).

Because these classifications are somewhat confusing, the simplest approach is to note whether the dissection extends proximal or distal to the left subclavian artery, because proximal dissections need surgery and distal ones are first managed medically.

The classes of dissection also have bearing on treatment. 1 These are:

  • Class I —classic aortic dissection in the media with two lumens separated by a “flap” or septum
  • Class II —intramural hematoma in the aortic wall from dissection in which the intimal tear cannot be imaged (these are nearly always found duringsurgery or autopsy)
  • Class III —localized confined intimal tears without extensive undermining of the intima or flap formation. These are often seen with Marfan syndrome and can rupture or cause tamponade, as can any type of proximal dissection. The typical appearance is of a bulging bubble in the aortic wall.
  • Class IV —penetrating atherosclerotic ulcers with localized dissections or wall hematomas, often with calcium at the base of a mushroom-shaped area of extraluminal contrast. Of note, the plane of dissection is often between the media and adventitia.
  • Class V —iatrogenic or posttraumatic dissection.

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