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.









TABLE 29-1 Factors Associated with Predisposition to AD






























Degeneration of the aortic wall



Advanced age


Chronic hypertension


Connective tissue disorders



Marfan syndrome


Ehlers-Danlos syndrome


Loeys-Dietz syndrome


Familial AD syndromes


Inflammatory disorders



Giant cell arteritis


Takayasu arteritis


Iatrogenic injury



Catheterization


Intra-aortic balloon pump


Aortic and cardiac surgery


Congenital disorders



Bicuspid aortic valve


Aortic coarctation


Turner syndrome


Noonan syndrome


Pregnancy


Cocaine use


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).









TABLE 29-2 Advantages, Disadvantages, and Performance of Aortic Imaging Modalities for AD









































Modality


Findings


Advantages


Disadvantages


Sensitivity (%)


Specificity (%)


Transthoracic echocardiography


Diagnostic:


Undulating intimal flap in proximal aorta


Suggestive:


Aortic root dilatation


Aortic insufficiency


Pericardial effusion


Easy to obtain


Performed at bedside Noninvasive


Visualization of aorta limited to aortic root


Poor image quality in many patients


70-90 (type A)


30-40 (type B)


80


Transesophageal echocardiography


Diagnostic:


Undulating intimal flap in aorta


Differential flow in true and false lumens


Intramural hematoma


Suggestive:


Aortic root dilatation


Aortic insufficiency


Pericardial effusion


Quick to perform


Performed at bedside Descending aorta can be assessed


Valvular and ventricular functional assessment possible


Specially trained personnel needed to perform test


Aortic arch may be obscured from overlying bronchus


90-100


70-80


CT


Diagnostic:


Intimal flap within aorta


Presence of dual lumens with differential contrast Enhancement


Suggestive:


Aortic root dilatation


Pericardial effusion


Readily available at most centers


Limited visualization of branch vessels


Requires intravenous iodinated contrast


Unable to assess aortic valve and ventricular function


90-100


80-90


Magnetic resonance imaging


Diagnostic:


intimal flap within aorta


Presence of dual lumens


Suggestive:


Aortic root dilatation


Pericardial effusion


Excellent sensitivity and specificity


No need for contrast agents


Assessment of branch vessels


Not uniformly available


Long scanning times


Difficult to monitor patients during exam


95-100


95-100


Aortography


Diagnostic:


Intimal flap within aorta

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Jun 11, 2016 | Posted by in CRITICAL CARE | Comments Off on The Acute Aortic Syndromes

Full access? Get Clinical Tree

Get Clinical Tree app for offline access