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Acute Aortic Dissection: Clinician Update
Alan C. Braverman
Circulation 2010;122;184-188
DOI: 10.1161/CIRCULATIONAHA.110.958975
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CLINICIAN UPDATE
Acute Aortic Dissection
Clinician Update
Alan C. Braverman, MD
A
27-year-old previously healthy
woman presented to the emergency room after the sudden onset of
severe chest pain and shortness of
breath during the 37th week of pregnancy. Her examination was remarkable for a blood pressure of 118/
70 mm Hg, heart rate of 100 bpm, and
respiratory rate of 24 breaths per
minute. The cardiovascular examination was notable for a soft systolic
ejection murmur, and the pulmonary
and general examinations were unremarkable. ECG demonstrated sinus
tachycardia, and her chest x-ray was
normal. A D-dimer level was elevated.
She underwent a spiral computed tomography scan to evaluate for pulmonary embolism, which instead demonstrated an acute type A aortic
dissection and a very small patent ductus arteriosus. The patient underwent
emergency cesarean section, which delivered a viable baby, and repair of the
type A dissection. Her aortic valve was
trileaflet. She had no features on examination to suggest Marfan syndrome
or Loeys-Dietz aneurysm syndrome.
Her father had died suddenly at 31
years of age of a “presumed heart
attack,” and her paternal uncle had
undergone ascending aortic aneurysm
resection at 42 years of age. Mutation
analysis in this woman detected a heterozygous mutation in MYH11, confirming familial thoracic aortic aneurysm/dissection (TAA/D).
Acute aortic dissection is the most
common life-threatening disorder affecting the aorta.1 The immediate mortality rate in aortic dissection is as high
as 1% per hour over the first several
hours, making early diagnosis and
treatment critical for survival. Classification schemes for aortic dissection
are based on anatomic involvement of
the aortic dissection (Figure 1).2 In the
DeBakey classification, type I dissections originate in the ascending aorta
and extend to at least the aortic arch;
type II dissections involve the ascending aorta only; and type III dissections
begin in the descending aorta, usually
just distal to the left subclavian artery.
In the Stanford classification, type A
dissections involve the ascending
aorta, and type B dissections are those
that do not involve the ascending aorta.
Ascending dissections require emergency surgical repair, whereas medical
therapy is usually the initial strategy
for acute type B dissections. Ascending aortic dissection is most common
in the 50- to 60-year age range,
whereas descending dissections occur
more commonly in older individuals.
Because acute aortic dissection is
much less common than other conditions associated with chest or back
pain, a high index of suspicion is
important in making this diagnosis.
Many conditions are associated with
aortic dissection (the Table).2 Hypertension is present in ⬇75% of individuals with aortic dissection. Genetically
triggered disorders affecting the aorta
are an important and often underrecognized cause of aortic dissection.
Marfan syndrome, Loeys-Dietz aneurysm syndrome, vascular EhlersDanlos syndrome, bicuspid aortic
valve, Turner syndrome, and familial
TAA/D syndrome are all genetic conditions associated with thoracic aortic
aneurysm and/or dissection. Prior cardiac surgery, especially aortic valve
replacement and aortic manipulation
(including angiography and stenting),
are risk factors for aortic dissection.
Acute hemodynamic stress such as that
From the Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St Louis, Mo.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/122/2/184/DC1.
Correspondence to Alan C. Braverman, MD, FACC, Alumni Endowed Professor of Cardiovascular Diseases, Cardiovascular Division, Department of
Medicine, Washington University School of Medicine, 660 S Euclid Ave, Box 8086, St. Louis, MO 63110. E-mail [email protected]
(Circulation. 2010;122:184-188.)
© 2010 American Heart Association, Inc.
Circulation is available at http://circ.ahajournals.org
DOI: 10.1161/CIRCULATIONAHA.110.958975
184
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Braverman
Acute Aortic Dissection
185
Table. Risk Factors for Aortic
Dissection
Hypertension
Genetically triggered thoracic aortic disease
Marfan syndrome
Bicuspid aortic valve
Loeys-Dietz syndrome
Hereditary TAA/D
Vascular Ehlers-Danlos syndrome
Congenital diseases/syndromes
Coarctation of the aorta
Turner syndrome
Tetralogy of Fallot
Atherosclerosis
Penetrating atherosclerotic ulcer
Trauma, blunt, or iatrogenic
Catheter/stent
Intraaortic balloon pump
Aortic/vascular surgery
Motor vehicle accident
Coronary artery bypass surgery/aortic valve
replacement
Figure 1. Classification schemes of acute aortic dissection. Reprinted with permission
from Braverman et al.2© Elsevier. In press.
Cocaine use
Inflammatory/infectious diseases
Giant cell arteritis
encountered with cocaine use, pheochromocytoma, and heavy weightlifting has been associated with aortic
dissection. Aortic dissection may complicate aortitis, most commonly giant
cell arteritis.
Acute aortic dissection complicating
pregnancy is uncommon. It usually
occurs during labor and delivery or in
the early postpartum period. Although
hormonal changes in the aortic wall
have been theorized as potentially
playing a role, an underlying genetic
disorder associated with abnormalities
of the aortic wall such as that present
in familial TAA/D, Marfan syndrome,
Loeys-Dietz aneurysm syndrome, vascular Ehlers-Danlos syndrome, bicuspid aortic valve, Turner syndrome, or
other genetic disorder is the most
likely underlying cause for aortic dissection complicating pregnancy.
Cystic medial degeneration is the
pathology underlying many thoracic
aortic aneurysms and dissections. Abnormalities in the transforming growth
factor-␤ pathway and abnormalities in
smooth muscle cell contractile element
function may underlie certain aortic
dissections.3 Patients with thoracic
aortic aneurysms from any cause are at
risk for aortic dissection, with absolute
size (especially ⬎5 to 6 cm), age, body
surface area, sex, rate of growth, and
specific genetic disorder all modulating risk of dissection.
Clinical Manifestations
The symptoms of aortic dissection
may be highly variable and may mimic
much more common conditions. Thus,
a high index of suspicion must be
maintained, especially when risk factors for dissection are present or signs
and symptoms suggest this possibility.
The vast majority of patients with
acute dissection have sudden, severe
chest, back, or abdominal pain, which
may be maximal at its onset. The pain
may be migratory or may radiate from
chest or back to the abdomen or to the
lower extremities. However, in some
instances, the pain resolves and symptoms may be referable to other com-
Takayasu arteritis
Behȩt disease
Aortitis
Syphilis
Pregnancy
Reprinted with permission from Braverman et
al.2 © Elsevier. In press.
plications such as heart failure from
acute aortic regurgitation, neurological
deficits, syncope, or vascular
insufficiency.
Although most patients with type B
dissections are hypertensive, many patients with type A dissections are normotensive or hypotensive on presentation.1 Hypotension complicating acute
aortic dissection is usually related to
cardiac tamponade, aortic rupture, or
heart failure associated with severe
aortic regurgitation. Sudden chest or
back pain accompanied by pulse deficits, aortic regurgitation, or neurological manifestations should alert the clinician to the diagnosis of acute aortic
dissection. However, pulse deficits
were present in only 19% of type A
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July 13, 2010
dissection and 9% of type B dissection.1 The murmur of aortic regurgitation was present in 44% of type A
dissections and 12% of type B dissections in the International Registry of
Acute Aortic Dissection series.1 There
are several mechanisms for acute aortic regurgitation in type A dissection,
with aortic leaflet prolapse or distortion of leaflet alignment by the dissection flap being most common.
Neurological complications of dissection are more common in type A
dissections and include stroke, spinal
cord ischemia, ischemic neuropathy,
and hypoxic encephalopathy. Syncope
occurs in 9% of acute dissection and
may be caused by cardiac tamponade,
aortic rupture, cerebral vessel obstruction, or activation of cerebral baroreceptors. A particularly dangerous complication of dissection is acute
myocardial infarction or coronary ischemia related to the dissection flap
obstructing coronary flow because it
may mask the diagnosis of dissection
or lead to inadvertent use of antiplatelet and anticoagulant therapy
and delay recognition and treatment
of the dissection.
Vascular complications involving
branch vessels may lead to malperfusion, which may lead to mesenteric or
limb ischemia. Renal ischemia or renovascular hypertension may be a result of the dissection process. Leftsided pleural effusions are common
with acute dissection and are usually
sympathetic effusions, whereas acute
hemothorax signals acute aortic rupture or leaking dissection.
Laboratory Features
The chest x-ray may be the first clue to
the diagnosis of aortic dissection, with
abnormal aortic contour or widening
of the aortic silhouette being present in
⬎80% of acute dissection.1 However,
12% to 15% of patients with acute
aortic dissection will have a normal
chest x-ray. Thus, it is important to
remember that a normal chest x-ray
cannot exclude the presence of aortic
dissection. The ECG changes in aortic
dissection are usually nonspecific, but
1% to 2% of patients have acute ST
elevation.
Tremendous interest exists in the
development of biomarkers that can
reliably diagnose or exclude acute aortic dissection. Release of smooth muscle proteins, soluble elastin fragments,
myosin heavy chain, and creatine
kinase-BB isoform has been reported
after aortic dissection, but none are
currently available for clinical use.4 As
is the case in pulmonary embolism,
D-dimer levels are elevated in acute
aortic dissection.4 Additionally, in patients presenting within the first 24
hours of symptom onset, a D-dimer
level ⬍500 ng/mL had a negative likelihood ratio of 0.07 and a negative
predictive value of 95%.4 However,
the patency of the true lumen affects
D-dimer levels in acute dissection.
Dissection variants such as intramural
hematoma and penetrating atherosclerotic ulcer may not have elevated
D-dimer levels. More studies are required to determine the accuracy of
D-dimer assays in acute aortic syndromes and how to best use D-dimer
testing in aortic dissection.
Diagnostic Techniques
Multidetector computed tomography,
transesophageal echocardiogram, and
magnetic resonance imaging are
highly accurate in the diagnosis of
aortic dissection (Figure 2).2 In addition to making the diagnosis of aortic
dissection or its variants (intramural
hematoma and penetrating atherosclerotic ulcer), the imaging must confirm
whether the ascending aorta is involved. Other useful information includes anatomic features and complications of the dissection, including
entry and reentry sites, extent of dissection, branch vessel involvement,
aortic regurgitation, pericardial effusion or hemopericardium, and any
signs of rupture. The selection of a
specific imaging modality is influenced by individual patient characteristics and variables and institutional
capabilities and expertise.5 Contrast
computed tomography is the most
commonly used modality in diagnos-
ing aortic dissection and is readily
available in most emergency rooms.
Because magnetic resonance imaging
takes longer for image acquisition and
leaves the patient relatively unmonitored, it is usually not the procedure of
first choice. Transesophageal echocardiogram has an advantage in being
portable and able to be performed at
the bedside for the unstable patient
(Movies I and II in the online-only
Data Supplement). Although aortic
dissection may be diagnosed by transthoracic echocardiogram, the sensitivity and specificity are much lower than
with the other diagnostic modalities;
thus, this technique is not the first
choice for diagnosing dissection.
Management
Immediate management of aortic dissection includes stabilizing the patient
with prompt attention to blood pressure reduction. ␤-Blockers are the first
drugs of choice because of their mechanism of lowering the rate of rise of
ventricular force (dP/dt) and stress on
the aorta. Intravenous agents are chosen for rapid onset. In many instances,
multiple blood pressure agents are required. In patients in whom refractory
hypertension exists, renovascular hypertension related to the dissection flap
must be considered. All patients with
acute aortic dissection should undergo
multidisciplinary evaluation that includes cardiothoracic and/or vascular
surgical consultation. Emergency surgery is recommended for acute type A
dissection; initial medical management
is recommended for uncomplicated
type B dissection. In the International
Registry of Acute Aortic Dissection,
the mortality rate of patients undergoing surgery for type A dissection was
26% and for those treated medically
was 58%.1 Patients with low-risk features have a significantly lower mortality rate than those with malperfusion, shock, or cardiac tamponade.
Uncomplicated type B dissection has
an in-hospital mortality rate of ⬇10%.
Most series of acute type B dissection
have reported a mortality rate between
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Braverman
Figure 2. Contrast computed tomography scan demonstrating acute type A aortic
dissection with enlargement of the ascending aorta and intimal flap (arrow) in the
ascending and descending aorta. Both the true lumen (TL) and false lumen are
opacified with contrast in this example. Reprinted with permission from Braverman
et al.2© Elsevier. In press.
25% and 50% for those requiring
emergency surgery.
Surgical management of type A dissection involves excision of the intimal
tear when possible, obliteration of entry into the false lumen proximally and
distally, and interposition graft replacement of the ascending aorta. The
aortic valve may need to be replaced,
depending on the underlying pathology of the valve and aortic root. Complicated type B dissections may require repair of conditions such as
aortic rupture, visceral, or branch vessel ischemia. Endovascular grafts have
the potential to treat many complications of type B dissections with relatively low short-term morbidity and
mortality rates. Trials are underway to
prospectively evaluate endovascular
graft therapy in acute complicated type
B dissection.
Long-Term Management
Short- and long-term survival in acute
type A dissection has ranged between
52% and 94% at 1 year and 45% and
88% at 5 years.6 The 10-year actuarial
survival rate of patients with acute
dissection who survive initial hospitalization is reported as 30% to 60% in
various studies. One recent study reported a 10-year survival of 55% and
20-year survival of 30% after type A
dissection.7 ␤-Blocker– based therapy
is the foundation of long-term medical
management. Drugs such as angiotensin receptor blockers, by antagonizing
transforming growth factor-␤, may be
beneficial in certain genetically triggered disorders, but prospective data
after aortic dissection are lacking.
Lifelong imaging of the entire aorta at
regular intervals is important to survey
for aneurysmal enlargement or other
complications. Lifestyle modifications, including limitations on physical
activity and certain types of employment, are important tenets of
management.
Although most patients with dissection have underlying hypertension,
only a tiny fraction of all hypertensive individuals ever have a dissection. It is imperative that one consider
an underlying genetic disorder in the
individual with acute aortic dissection
and that a comprehensive family history be obtained. Some patients will
have syndromic features such as those
characteristic of Marfan syndrome or
Loeys-Dietz syndrome. The presence
of dural ectasia in the lumbosacral
spine on the computed tomography or
magnetic resonance imaging will often provide a clue to such genetically
Acute Aortic Dissection
187
triggered disorders. Bicuspid aortic
valve is associated with ascending
thoracic aortic aneurysm and risk of
aortic dissection and may be familial
in ⬇10% of cases.8
As detailed in the case presentation
above, familial thoracic aortic aneurysm syndromes are an everexpanding cause of aortic dissection.
Comprehensive family studies have
recognized that ⬇20% of individuals
with a thoracic aortic aneurysm or
dissection will have another firstdegree relative with thoracic aortic disease.9 Screening first-degree relatives
of the patient with acute aortic dissection for thoracic aortic disease is important. This involves a clinical history, physical examination, and
imaging for appropriate candidates.
In most patients with familial
TAA/D, the disorder is autosomal
dominant with decreased penetrance
and variable expression. 3 Several
genes have been identified in families
with thoracic aortic disease, including
FBN1, TGFBR1 and 2, ACTA2, and
MYH11. ACTA2 mutations have been
identified in ⬇14% of TAA/D and
have been associated with livedo reticularis, patent ductus arteriosus, and
bicuspid aortic valve.3 If a specific
gene mutation is determined in a family, all first-degree relatives may be
screened for the same mutation. Recognition of individuals at risk for thoracic aortic disease allows prophylactic surgery and lessens risk of aortic
dissection.
One year has passed since the acute
dissection in the patient presented
above. Imaging studies have demonstrated no change in the residual aortic
dissection. She has been maintained on
␤-blocker and angiotensin receptor
blocker therapy. It is likely that her late
father’s death was related to an acute
aortic dissection instead of a “myocardial infarction.” The patient’s 5 children have undergone evaluation; two,
including the one born during the acute
aortic dissection, harbor the same mutation in MYH11. It is important to
consider genetically triggered disorders in patients with aortic dissection
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and to evaluate their first-degree relatives for thoracic aortic disease.
Disclosures
Dr Braverman is a member of the Professional Advisory Board of the National
Marfan Foundation. Dr Braverman has
served as an expert witness in cases of
aortic dissection with a “modest”
relationship.
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