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sive. Although a small percentage of the normal population will exhibit a blood pressure differential between the

upper extremities, a blood pressure differential �20 mmHg

in this clinical context should be considered highly s uspicious. That said, the absence of a blood pressure differential does not exclude aortic dissection.

The cardiac examination should focus on any abnormal

heart sounds. Consider pericardia! tamponade in patients

with distant heart tones and associated hypotension, jugular venous distention, and tachycardia. The presence of a

diastolic murmur suggests secondary aortic regurgitation.

Perform a focused neurologic examination, looking for

signs of hemiplegia or paraplegia.

Some of the more rare clinical findings associated with

aortic dissection include Horner's syndrome, superior

vena cava syndrome, acute arterial occlusion with limb

ischemia, lower cranial nerve palsies, and bilateral testicular tenderness. It is important to realize that many of the

classic physical examination findings are frequently absent,

and therefore the history of present illness is often more

significant than the physical exam. Always maintain a high

index of suspicion for aortic dissection in the patient pre ­

senting with an acute coronary syndrome associated with

neurologic or vascular signs and symptoms.

DIAGNOSTIC STUDIES

...... Laboratory

There are no laboratory studies that can reliably rule out

the diagnosis of acute aortic dissection. A screening

d-dimer assay has been shown to be highly sensitive

(94-99%), but it should not be used in isolation to rule out

acute dissection. Other laboratory studies (complete blood

count, basic metabolic profile, troponin I, etc.) are often

used to exclude or confirm an alternative diagnosis or

complication of aortic dissection.

...,.. Electrocardiogram

The electrocardiogram (ECG) has no primary role in the

diagnosis of acute aortic dissection. It is often normal

( 31 o/o) or may show nonspecific abnormalities such as left

ventricular hypertrophy (26%). As proximal aortic dissections can frequently involve the coronary arteries (right >

left), the ECG can be useful for detecting secondary cardiac

ischemia.