TABLE 29-1 Factors Associated with Predisposition to AD | ||||||||||||||||||||||
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TABLE 29-2 Advantages, Disadvantages, and Performance of Aortic Imaging Modalities for AD | ||||||||||||||||||||||||||||||||
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The Acute Aortic Syndromes
The Acute Aortic Syndromes
Piotr Sobieszczyk
I. OVERVIEW. The acute aortic syndromes are rare yet morbid entities with variable clinical presentation. Mortality due to these disorders increases rapidly with delayed treatment, requiring a high index of suspicion to allow early recognition and management.
II. AORTIC DISSECTION
A. Background.
1. Epidemiology of aortic dissection (AD).
a. Most common acute aortic syndrome.
b. Estimated US annual incidence of 3.5/100,000 may be an underestimate as many patients die before diagnosis is made.
c. Incidence increases with age.
2. Stanford classification system.
a. Type A involves the ascending or proximal aorta.
b. Type B involves the aorta distal to the origin of the left subclavian artery.
B. Pathophysiology.
1. Tear in the aortic intima exposes underlying media to blood flow at systemic pressure. The intimal tear propagates, forming a second or “false” lumen.
2. Etiology of AD is variable (Table 29-1). Processes that weaken the medial layers of the aorta, such as hypertension or intrinsic connective tissue disorders, may eventually result in intramural hemorrhage, AD, or rupture. Iatrogenic causes include previous aortic surgery or catheterization.
C. Prognosis.
1. Without intervention, the risk of death approaches 1%/hour in the first 24 hours after AD. For untreated cases, mortality rates are approximately 50% at 1 week and upward of 90% beyond 3 months.
2. Type A: 30-day mortality with medical management approaches 50% but 20% with surgical repair.
3. Type B: 30-day mortality rate 10% with medical therapy.
D. Diagnosis.
1. Clinical presentation is variable and depends on the aortic segment involved. No pathognomonic physical findings secure the diagnosis. Clinical index of suspicion must be high.
a. Common symptoms: chest pain (73%), back pain (53%), syncope (10%).
b. Common signs: hypertension (77% type B cases, 36% type A cases).
c. Less common signs: murmur of aortic insufficiency (31%); hypotension and shock; pericardial tamponade; myocardial ischemia (3%); congestive heart failure (4% to 7%); malperfusion syndromes (e.g., limb ischemia, neurologic impairment or paraplegia, mesenteric ischemia, or renal insufficiency).
2. Diagnostic testing.
a. No reliable blood test at this time for rapid detection of AD. Elevated D-dimer may be helpful in intermediate-risk patients.
b. Chest radiography has limited diagnostic utility.
c. Electrocardiogram is nonspecific (normal in 31% of cases). Ischemic changes may be seen if type A dissection involves the coronary arteries.
d. Noninvasive imaging of the aorta establishes the diagnosis. Three available modalities provide similar diagnostic accuracy (Table 29-2). Invasive angiography is rarely required.
i. Contrast-enhanced computed tomography (CT).
ii. Transesophageal echocardiogram (TEE).
iii. Magnetic resonance angiography (MRA).
