Acute Aortic Disease.. - Index of

36 Isselbacher
deficits are most commonly detected in the arms, and since most type B aortic
dissections arise just distal to the subclavian artery, they are less likely to compromise
arterial flow to the arms. Not surprisingly, pulse deficits occur twice as
often among those with type A aortic dissection than type B, at 30% versus 15%,
respectively (5). It goes without saying that in order to detect a blood pressure
differential, one must check blood pressure readings in both arms. However, quite
often in emergency departments blood pressure readings are performed in one
arm only. If one checks the blood pressure in only the arm that has a pulse deficit,
one will obtain a falsely low blood pressure reading; this has often been referred
to as “pseudohypotension,” and it sometimes leads to incorrect diagnosis or
therapy. In order to avoid being misled in this way, and in order to identify pulse
deficits as valuable clinical clues, blood pressure readings should be taken in both
arms in all patients presenting with chest pain syndromes.
In rare cases arterial supply to both arms is compromised, in which case
comparing the blood pressure readings in the two arms will fail to reveal a
difference, and yet both readings will be falsely low. One should suspect bilateral
pseudohypotension if a patient appears to be well perfused despite low blood
pressure readings in both arms. In such a case, one should check bilateral thigh
blood pressure readings to detect evidence of a higher true arterial pressure.
Even when a subclavian artery is completely occluded, in most cases there
is still adequate perfusion to the arm to prevent any overt arm symptoms or signs
at rest. However, occlusion of one of the common iliac arteries will typically
result in a cold and pulseless lower extremity, which is readily evident on physical
examination.
It should also be noted that in some cases pulse deficits can be transient,
as a result of acute decompression of the false lumen by distal reentry into the true
lumen or movement of the intimal flap away from the occluded orifice.
Other Signs
Patients with aortic dissection may present with a fever, often accompanied
by leukocytosis and an elevated erythrocyte sedimentation rate; the etiology of
the fever is uncertain. Rarely, aortic dissection may produce hoarseness, upper
airway obstruction, hemoptysis (due to rupture into the tracheobronchial tree),
hematemesis (due to rupture into the esophagus), a pulsating neck mass, or a
continuous murmur (due to rupture of the aorta into the right atrium, the right
ventricle, or the left atrium).
THE GREAT MASQUERADER
Many more patients present with symptoms of chest, back, or abdominal pain
than have aortic dissection, and there is significant overlap among the symptoms
and signs of aortic dissection and other acute syndromes. Indeed, most patients
with aortic dissection do not present in a “classic fashion,” but rather with only a