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Clinical features and diagnosis of acute aortic dissection - UpToDate

11/18/17, 10(25 PM

Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Clinical features and diagnosis of acute aortic dissection
Authors: James H Black, III, MD, Warren J Manning, MD
Section Editors: James Hoekstra, MD, Joseph L Mills, Sr, MD, John F Eidt, MD
Deputy Editor: Kathryn A Collins, MD, PhD, FACS

All topics are updated as new evidence becomes available and our peer review process is complete.
Literature review current through: Oct 2017. | This topic last updated: Nov 07, 2017.
INTRODUCTION — Aortic dissection is relatively uncommon, but it often presents acutely as a catastrophic illness with severe chest pain and
acute hemodynamic compromise. Early and accurate diagnosis and treatment are crucial for survival.
Death from aortic dissection can be related to rupture of the dissection into the pericardium precipitating cardiac tamponade, acute dissection
into the aortic valvular annulus leading to severe aortic regurgitation, obstruction of the coronary artery ostia leading to myocardial infarction,
and end-organ failure due to abdominal aortic branch vessel obstruction [1,2]. The International Registry of Acute Aortic Dissection (IRAD) has
provided a contemporary perspective from the worldwide accrual of patients into a prospective database and allowed assessment of treatment
paradigms. Despite the advances detailed in their reports, mortality related to aortic dissection remains high at 25 to 30 percent [3].
The clinical manifestations and diagnosis of acute aortic dissection will be reviewed here. Medical and surgical management are discussed
separately. (See "Management of acute aortic dissection" and "Surgical and endovascular management of type B aortic dissection".)
CLASSIFICATION — Aortic dissection is classified, somewhat arbitrarily, as acute or chronic based upon the duration of symptoms at the time
of presentation. During the first two weeks (acute phase), life-threatening complications due to branch involvement or aortic rupture are more
likely to occur compared with the timeframe past two weeks (chronic phase) [4,5].
Anatomic classification — The two main anatomic classifications used to describe aortic dissection are the DeBakey and Stanford (Daily)
systems (figure 1) [6-9]. The Stanford system is more widely used and classifies dissections that involve the ascending aorta as type A,
regardless of the site of the primary intimal tear, and all other dissections as type B. By comparison, the DeBakey system is based upon the site
of origin, with type 1 originating in the ascending aorta and propagating to at least the aortic arch, type 2 originating in and confined to the
ascending aorta, and type 3 originating in the descending aorta and extending distally or proximally. An alternative classification has been
proposed; the DISSECT system assesses six characteristics of dissection that provide the most important details influencing the choice of
treatment, particularly those that are important when considering an endovascular procedure [10].
Ascending aortic dissections are almost twice as common as descending dissections. The right lateral wall of the ascending aorta is the most
common site [11]. In patients with an ascending aortic dissection, aortic arch involvement occurs in up to 30 percent [12].
Isolated abdominal aortic dissection is sporadically reported and can be due to iatrogenic, spontaneous, or traumatic mechanisms (image 1)
[13]. The infrarenal abdominal aorta is more commonly involved than the suprarenal aorta. In one review of 52 reported cases, the entry site for
spontaneous isolated abdominal aortic dissections (SIAADs) most commonly occurred between the renal arteries and inferior mesenteric artery
[14]. A concomitant abdominal aortic aneurysm was identified in 40 percent of patients and indicated the need for repair. (See "Management of
symptomatic (non-ruptured) and ruptured abdominal aortic aneurysm".)
Variants — There are several variants of aortic dissection including aortic intramural hematoma, intimal tear without hematoma, and penetrating
atherosclerotic ulcer (figure 2) [7,15,16]. These are briefly defined below and discussed in more detail separately. (See "Overview of acute aortic
syndromes".)
● Aortic intramural hematoma – Aortic intramural hematoma, which is characterized by blood in the wall of the aorta in the absence of an
intimal tear (image 2), is another variant of aortic dissection that accounts for 5 to 13 percent of patients with clinical features consistent with
an aortic dissection. The false channel is probably produced by a rupture of the vaso vasorum into the media of the aortic wall and can
occur in the absence of significant atherosclerosis or with concomitant atherosclerotic ulcer. The clinical features and management of this
disorder are discussed separately. (See "Overview of acute aortic syndromes", section on 'Classification'.)
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● Intimal tear without hematoma – Intimal tear without hematoma is an uncommon variant of aortic dissection that is characterized by a
stellate or linear intimal tear associated with exposure of the underlying aortic media or adventitial layers. There is no progression or
separation of the medial layers (image 3) [16]. Blunt aortic injury with focal tear may manifest in this manner. (See "Overview of acute aortic
syndromes", section on 'Intimal tear without hematoma'.)
● Penetrating atherosclerotic ulcer – Penetrating ulceration of an atherosclerotic plaque often complicates an aortic intramural hematoma and
can also lead to aortic dissection or perforation [7]. Noninvasive imaging shows an ulcer-like projection into the hematoma (image 4). (See
"Overview of acute aortic syndromes", section on 'Classification'.)
PATHOPHYSIOLOGY — The primary event in aortic dissection is a tear in the aortic intima (image 5). Degeneration of the aortic media, or
cystic medial necrosis, is felt to be a prerequisite for the development of nontraumatic aortic dissection. Blood passes into the aortic media
through the tear, separating the intima from the surrounding media and/or adventitia and creating a false lumen. It is uncertain whether the
initiating event is a primary rupture of the intima with secondary dissection of the media or hemorrhage within the media and subsequent rupture
of the overlying intima [11]. (See "Overview of acute aortic syndromes".)
Fifty to 65 percent of aortic intimal tears originate in the ascending aorta within the sinotubular junction and extend to involve remaining portions
of the thoracoabdominal aorta [3]. Approximately 20 to 30 percent of intimal tears will originate in the vicinity of the left subclavian artery and
extend into the descending thoracic and thoracoabdominal aorta [3]. The commonality of these two predominant locales for development of the
aortic tear is hypothesized to be related to shear forces (dP/dT) being highest in these regions [5,17,18].
The dissection can propagate proximally or distally to involve the aortic valve and enter the pericardial space or branch vessels [6]. Such
propagation is responsible for many of the ischemic clinical manifestations, including aortic regurgitation (figure 3), cardiac tamponade, or
ischemia (coronary, cerebral, spinal, or visceral). Patients with involvement of the ascending aorta have imminent risk for aortic rupture. The
intimal tear with type B dissection can spiral into a cleavage plane within the media of the aorta along the posterolateral descending thoracic
aorta, leaving the celiac artery, superior mesenteric artery, and right renal artery, typically originating in the true lumen, with the left renal artery
deriving false lumen flow [5]. Variations in anatomy of the dissection are typical and underscore the critical need for proper axial imaging. In
addition, multiple communications may form between the true lumen and the false lumen.
Immediately following dissection, there is "intrinsic true lumen collapse" to a variable degree, and false lumen dilation, thus increasing the aortic
cross-sectional area [19]. The increase of the false lumen area correlates with blood pressure, the size of the entry tear into the false lumen, the
depth of the dissection plane within the media, and the percentage of aortic circumference involved. Because the outer wall of the false lumen is
thinned, it expands to generate the necessary wall tension to accommodate aortic pressure. The true lumen collapses as a result of the
pressure differential between the true and false lumens and may be exacerbated by the intrinsic recoil of the muscular elements within the
dissection flap [20].
Malperfusion of aortic branch vessels may occur due to the extension of the dissection throughout the thoracoabdominal aorta. Malperfusion of
a vascular bed can occur in one or more branch territories simultaneously. The standard nomenclature of the mechanisms of malperfusion of
aortic branch vessels is termed "dynamic obstruction" (figure 4 and movie 1) and "static obstruction" (figure 5) [21]. Malperfusion syndromes
may occur in 30 to 45 percent of descending dissections and correlate with early mortality [3,22-25].
INCIDENCE AND ASSOCIATED CONDITIONS — The incidence of acute aortic dissection in the general population is estimated to range from
2.6 to 3.5 per 100,000 person-years [26-29]. Seasonal variation in the incidence of aortic dissection has been described, with winter months
associated with higher admission rates for aortic dissection [30,31]. The reasons for this seasonal association are uncertain, but emotional
stressors are known to peak with the end-of-year holidays.
Patients with acute aortic dissection tend to be 60- to 80-year-old men [3,11,32-34]. In a review of 464 patients from the International Registry of
Acute Aortic Dissection (IRAD), 65 percent were men and the mean age was 63 years [3]. Women presenting with aortic dissection were
generally older than men (67 versus 60 years) [15].
There are some important differences between older adult patients and younger patients with dissections involving the ascending aorta. In an
IRAD review, 32 percent of patients were ≥70 years of age and were significantly more likely to have atherosclerosis, prior aortic aneurysm,
iatrogenic dissection, or intramural hematoma [35]. In a review of patients under age 40, only 34 percent had a history of hypertension and only
1 percent had a history of atherosclerosis [36]. Marfan syndrome is present in 8.5 percent of the younger patients (mean age 55 years) and was
not seen in any older adult patient [35].
In a separate review, familial dissections also occurred in significantly younger patients compared with sporadic aortic dissection (54 versus 63
years of age) [37].

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High-risk conditions — High-risk conditions commonly associated with aortic dissection include the following [38-40]:
● Hypertension – The most important predisposing factor of acute aortic dissection is systemic hypertension [3,11,32,41,42]. In the IRAD
review, 72 percent had a history of hypertension [3]. Hypertension was more common in those with a distal (type B) dissection compared
with a type A dissection (70 versus 36 percent) [3,43].
An abrupt, transient, severe increase in blood pressure has been associated with acute aortic dissection through various mechanisms.
Crack cocaine, which may cause transient hypertension due to catecholamine release, accounted for 37 percent of dissections in a report
of an inner city population [44]. The mean duration from last cocaine use to the onset of symptoms was 12 hours. (See "Clinical
manifestations, diagnosis, and management of the cardiovascular complications of cocaine abuse" and "Cocaine: Acute intoxication".)
High-intensity weight lifting or other strenuous resistance training can also cause a transient elevation in blood pressure and has been
reported as an antecedent [45]. Hypertension is also the postulated mechanism when energy drinks [46] or ergotism [47,48] have been
associated with aortic dissection.
● Genetically mediated collagen disorders (eg, Marfan syndrome, Ehlers-Danlos syndrome, annuloaortic ectasia) (image 6) – In an IRAD
review, Marfan syndrome was present in 50 percent of those under age 40, compared with only 2 percent of older patients [36]. Most
patients with Marfan syndrome and aortic dissection have a family history of dissection. There may also be an association between Marfan
syndrome and aortic dissection in the third trimester of pregnancy [49]. (See "Genetics, clinical features, and diagnosis of Marfan syndrome
and related disorders".)
● Preexisting aortic aneurysm – In an IRAD review, 13 percent of patients had a known aortic aneurysm prior to dissection [36]. The
ascending aorta was more often the site of origin of the dissection than the aortic arch or descending aorta. Such a history was more
common in patients under age 40 (19 percent). In a later IRAD review, known aortic aneurysm was present in 20.7 percent of patients
identified to have descending aortic dissection and 12.7 percent of those with ascending aortic dissection [43]. (See "Clinical manifestations
and diagnosis of thoracic aortic aneurysm" and "Clinical features and diagnosis of abdominal aortic aneurysm".)
● Bicuspid aortic valve – In an IRAD review, 9 percent of patients under age 40 with aortic dissection had a bicuspid valve, compared with 1
percent of those over age 40 [36] and 1 percent in the general population. Aortic dissection in patients with a bicuspid valve always involves
the ascending aorta, usually with severe loss of elastic fibers in the media [50]. The predisposition to dissection may reflect a genetic defect
in the aortic wall, as enlargement of the aortic root and/or ascending aorta is frequently associated with bicuspid aortic valves, even those
that function normally, independent of their function [51,52]. (See "Clinical manifestations and diagnosis of bicuspid aortic valve in adults".)
● Aortic instrumentation or surgery – Cardiac surgery or catheterization for coronary or valvular disease can be complicated by aortic
dissection [36,53-55]. Cardiac catheterization, particularly with femoral artery access, with or without coronary intervention was reported to
cause 14 of 723 dissections (2 percent) in a report from IRAD [56]. Ascending aortic dissection is a rare complication of coronary artery
bypass grafting (CABG), occurring with both conventional on-pump CABG and, perhaps more often, with minimally invasive off-pump
CABG [57-60]. In a review from a single institution, ascending aortic dissection occurred in 1 of 2723 patients (0.04 percent) treated with
conventional CABG and 3 of 308 undergoing off-pump CABG (1 percent) [59]. (See "Early noncardiac complications of coronary artery
bypass graft surgery", section on 'Aortic dissection' and "Off-pump and minimally invasive direct coronary artery bypass graft surgery:
Outcomes".)
Although rare, other procedures that manipulate the aorta, including carotid or other great vessel interventions and thoracic or abdominal
aortic repair (open or endovascular), can also be complicated by aortic dissection.
● Aortic coarctation – Aortic dissection can occur in patients with an aortic coarctation when surgery leaves behind abnormal para coarctation
aorta that has intrinsic medial faults, when balloon dilatation of native coarctation mechanically damages the inherently abnormal para
coarctation aorta. (See "Clinical manifestations and diagnosis of coarctation of the aorta".)
● Turner syndrome – Aortic dissection or rupture, often occurring with coarctation, is an increasingly recognized cause of death in women
with Turner syndrome. In a survey of 237 patients, at least 15 (6.3 percent) had aortic dilation: all involved the ascending aorta, 12 had an
associated risk factor such as hypertension or another cardiovascular malformation (eg, coarctation), and two had a dissection [61,62].
(See "Clinical manifestations and diagnosis of Turner syndrome".)
● Inflammatory diseases that cause vasculitis (giant cell arteritis, Takayasu arteritis, rheumatoid arthritis, syphilitic aortitis) [63,64]. (See
"Overview of and approach to the vasculitides in adults" and "Clinical manifestations of giant cell (temporal) arteritis", section on 'Large
vessel GCA'.)

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● Trauma rarely causes a classic dissection but can induce a localized tear in the region of the aortic isthmus (image 7). More commonly,
chest trauma from acute deceleration (as in a motor vehicle accident) results in aortic rupture or transection [65]. (See "Blunt thoracic aortic
injury".)
● Pregnancy and delivery – Pregnancy and delivery are independent risk factors for aortic dissection; however, the presence of other
conditions (eg, bicuspid aortic valve, Marfan syndrome) may compound the risk [49,66-69]. In one review, postpartum aortic dissection
occurred in 2 of 31 Marfan pregnancies [70]. A cohort study of administrative claims data in several states from 2005 through 2013 found a
rate of aortic complications of 5.5 per million patients during pregnancy and the postpartum period. Pregnancy was associated with a
significantly increased risk of aortic dissection or rupture compared with the control period one year later (incidence rate ratio 4.0; 95% CI
2.0-8.2) among women with and without documented connective tissue diseases (eg, Marfan syndrome), although the risk was significantly
greater in those with connective tissue diseases [67]. The authors noted that the findings may reflect prevalent but undiagnosed or
undocumented connective tissue disorders, or they may indicate that the physiologic changes of pregnancy can cause aortic injury even in
otherwise healthy women.
CLINICAL FEATURES — Clinical symptoms and signs related to aortic dissection events are listed below and discussed in detail in the linked
topics.
Although acute aortic dissection can occur at any time of the day, the onset of symptoms more commonly occurs during waking hours. In a
review that included 1827 patients, 25 percent of events occurred between 08:00 and 12:00 (8 am to 12 pm) [71]. A lower incidence was seen in
the late evening/early morning hours (22:00 to 02:00; 11pm to 2am). These may follow established patterns of blood pressure elevation and
reduction throughout the day. Daytime physical activity has also been linked to onset of acute aortic dissection, particularly in younger patients
[72].
Symptoms and signs — The symptoms and signs of acute aortic dissection depend upon the extent of the dissection and the affected
cardiovascular structures (table 1). Pain is the most common symptom, occurring in over 90 percent of patients, most commonly in the chest or
back [43]. Although painless dissection has been reported, it is relatively uncommon (6.4 percent in one retrospective review) [73]. Patients with
painless dissection were older (mean age 67 versus 62 years) and more often had ascending aortic dissection (75 versus 61 percent). A prior
history of diabetes, aortic aneurysm, or cardiovascular surgery was more common in patients with painless dissection. Presenting symptoms of
syncope, heart failure, or stroke were seen more often in this group. In another review, up to 10 percent of patients presented with neurologic
symptoms but without chest pain [74].
Hypertension is present in 70 percent of type B dissections but only in 25 to 35 percent of type A dissections. The presence of hypotension
complicating a type B dissection is rare, seen in less than 5 percent of patients, and usually implies rupture of the aorta. By contrast,
hypotension may be present in 25 percent of dissections that involve the ascending aorta, potentially as a result of aortic valve disruption
leading to severe aortic regurgitation and/or extravasation into the pericardial space leading to cardiac tamponade [3]. Malperfusion of
brachiocephalic vessels by the dissection may falsely depress brachial cuff pressures, usually by involving the left subclavian artery origin in the
type B dissection patient.
Acute pain — The most common presenting symptom is pain occurring in over 90 percent of patients, with 85 percent noting the onset to be
abrupt [3,32,43,75,76]. Typically the pain is severe and sharp/knife-like, causing the patient to seek medical attention within minutes to hours of
onset, and categorically unlike any pain experienced before. Pain can occur in isolation or be associated with syncope, a cerebrovascular
accident, acute coronary syndrome, heart failure, or other clinical symptoms or signs.
While the pain is typically described as anterior chest in location in ascending (type A) dissection, for descending (type B) dissection, the pain is
more often experienced in the back [3]. In an International Registry of Acute Aortic Dissection (IRAD) review, chest pain was significantly more
common in patients with type A dissections (83 versus 71 percent in type B dissections) [43], while both back pain (64 versus 47 percent) and
abdominal pain (43 versus 22 percent) were significantly more common with type B dissections [3]. The pain can radiate anywhere in the thorax
or abdomen [3,11]. Unlike the classic description of the character of pain in aortic dissection as ripping or tearing (50 percent), pain is more often
described as sharp (68 percent), and less often as migratory (19 percent) [3,43]. Older adult patients (>70 years) were significantly less likely to
have an abrupt onset of pain compared with younger patients (77 versus 89 percent) [35].
The localization of pain to the abdomen was reported by 21 percent of patients in type A dissection and 43 percent of patients in type B
dissection [3]. In such patients, a high index of suspicion for mesenteric vascular compromise is warranted [6,77-79]. (See "Overview of
intestinal ischemia in adults" and "Acute mesenteric arterial occlusion" and "Renal infarction" and "Ischemic hepatitis, hepatic infarction, and
ischemic cholangiopathy".)
Pulse deficit — The presence of impaired or absent blood flow to peripheral vessels is manifest as a pulse deficit, defined as a weak or

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absent carotid, brachial, or femoral pulse resulting from the intimal flap or compression by hematoma. A considerable variation (>20 mmHg) in
systolic blood pressure may be seen when comparing the blood pressure in the arms. In International Registry of Acute Aortic Dissection (IRAD)
reviews, women are less likely to have a pulse deficit than men [15]. Compared with younger patients, older adult patients (>70 years) were
significantly less likely to have any pulse deficit (24 versus 33 percent) [35].
In those with aortic arch and/or thoracoabdominal aorta involvement, pulse deficits are common and occur in 19 to 30 percent of patients
compared with 9 to 21 percent with a descending aortic dissection [3,43,80,81]. In the IRAD population, the involvement of the brachiocephalic
trunk was noted in 14.5 percent of patients, the left common carotid artery in 6.0 percent, the left subclavian artery in 14.5 percent, and the
femoral arteries in 13.0 to 14.0 percent [3]. Patients presenting with pulse deficits more often had neurologic deficits, coma, and hypotension.
Carotid pulse deficits, not surprisingly, were strongly correlated with fatal stroke, consistent with prior observations [82].
The number of pulse deficits was also clearly associated with increased mortality. Within 24 hours of presentation, 9.4 percent of patients with
no deficits died, 15.8 percent of patients with one or two deficits died, and 35.3 percent of patients with three or more deficits died [80].
With respect to isolated lower extremity pulse deficits, mortality from lower extremity ischemia or its sequelae was uncommon [22]. Nonetheless,
leg ischemia caused by acute dissection is a marker of extensive dissection and may be accompanied by other compromised vascular
territories. The clinical course of the peripheral ischemia can be quite variable, and up to one-third of this group may demonstrate spontaneous
resolution of their pulse deficits [22].
Patients with a pulse deficit have a higher rate of in-hospital complications and mortality compared with those without a pulse deficit [80]. A rapid
bedside pulse examination can provide important information in the diagnosis of acute aortic dissection and those at risk for complications. In a
previous report of patients treated during the 1990s, those with peripheral branch obstruction had a mortality rate of 23 percent compared with
16 percent for those without obstruction [23]. In contrast to the IRAD study findings, the presence of peripheral vascular complications did not
increase mortality [19]. This finding was thought to be due to a more timely diagnosis, prompt initiation of therapy, and the recognition of the
importance and appropriate treatment of peripheral vascular complications.
Heart murmur — Aortic dissection that propagates proximal to the initial tear can involve the aortic valve (figure 3) [6]. A new diastolic
murmur in association with severe acute chest pain is a sign of acute aortic regurgitation. Characteristically, it is a diastolic decrescendo murmur
associated with a wide pulse pressure, hypotension, and/or heart failure. Acute aortic valve regurgitation occurs in one-half to two-thirds of
ascending dissections [3,83]. The murmur of aortic regurgitation related to aortic dissection is most commonly heard along the right sternal
border, as compared with the left sternal border for aortic regurgitation due to primary aortic valve disease. The duration of the diastolic murmur
may be quite short due to rapid ventricular filling and early equilibration of aortic and left ventricular diastolic pressures. (See "Auscultation of
cardiac murmurs in adults" and "Acute aortic regurgitation in adults".)
In one IRAD review, patients older than 70 years were significantly less likely to have a murmur of aortic regurgitation compared with younger
patients (29 versus 47 percent) [35].
Focal neurologic deficit — Focal neurologic deficits are due to propagation of the dissection proximally or distal to the initial tear involving
branch arteries, or due to mass effects as the expanding aorta compresses surrounding structures [15].
● Stroke or altered consciousness can be from direct extension of the dissection into the carotid arteries or diminished carotid blood flow.
Alterations of consciousness are more common in women than in men.
● Horner syndrome is from compression of the superior cervical sympathetic ganglion.
● Hoarseness is from vocal cord paralysis due to compression of the left recurrent laryngeal nerve.
● Acute paraplegia is from spinal cord ischemia. Spinal cord ischemia from the interruption of intercostal vessels is clearly more common with
type B aortic dissections than with type A dissections, and it may occur in 2 to 3 percent of all patients [3,84].
Hypotension — Syncope, hypotension, and/or shock at initial presentation are more common in patients with ascending aortic dissection,
whereas hypertension is more common in patients with descending aortic dissection [82]. Hypotension/shock may be related to rupture of the
aorta, or propagation of the dissection via the following mechanisms:
● Cardiac tamponade from rupture can lead to sudden death. Tamponade occurs more often in women than in men [15]. (See "Cardiac
tamponade".)
● Acute aortic valve regurgitation (figure 3). (See 'Heart murmur' above.)

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● Acute myocardial ischemia or myocardial infarction (MI) due to coronary occlusion. The right coronary artery is most commonly involved
and, in infrequent cases, leads to complete heart block. (See 'Electrocardiogram' below.)
● Hemothorax or hemoperitoneum, and possibly exsanguination if the dissection extends through the adventitia in the thoracic or abdominal
aorta.
Syncope — Syncope occurs in 5 to 10 percent of patients and often indicates the development of cardiac tamponade or involvement of
the brachiocephalic vessels [82]. Overall, patients in the IRAD study presenting with syncope were more likely to have a type A dissection than a
type B dissection (19 versus 3 percent), and more likely to have cardiac tamponade (28 versus 8 percent). Similarly, they were more likely to
have a stroke (18 versus 4 percent) and more likely to die in the hospital (34 versus 23 percent). Although patients presenting with syncope had
a higher rate of severe complications (tamponade, stroke, death), almost one-half of syncope patients had none of the aforementioned
complications to explain their loss of consciousness [82].
Electrocardiogram — Electrocardiography (ECG) is often obtained in the initial evaluation of patients with chest pain. Aortic dissection that
does not involve coronary ostia can usually be distinguished from acute coronary syndrome by the nature and location of the chest pain and the
absence of ECG changes characteristic of ischemia. (See "Evaluation of the adult with chest pain in the emergency department", section on
'Electrocardiogram'.)
However, the ECG is less helpful when dissection leads to coronary ischemia. Data from IRAD further suggest that involvement of a coronary
artery in an aortic dissection may not manifest changes in the electrocardiogram [85]. In a review of 464 patients, the ECG was normal in 31
percent, showed nonspecific ST and T wave changes in 42 percent (commonly, left ventricular hypertrophy and strain patterns associated with
hypertension), showed ischemic changes in 15 percent, and, among patients with an ascending aortic dissection, showed evidence of an acute
myocardial infarction in 5 percent [3].
Chest radiograph — Plain chest films are also commonly obtained to help rapidly differentiate the various causes of chest pain (eg,
pneumothorax). (See "Evaluation of the adult with chest pain in the emergency department", section on 'Chest radiograph'.)
The most common abnormality seen in aortic dissection is widening of the aortic silhouette, appearing in 60 to 90 percent of cases [3,86]. The
IRAD review of 464 patients found that mediastinal widening was present in 63 percent with type A dissections, while 11 percent of patients had
no abnormality on chest radiography [3]. The comparable values in patients with type B dissections were 56 and 16 percent.
Radiographic evidence of a pleural effusion was found in 19 percent of dissections; this finding is more common in women than in men (26
versus 15 percent) [15]. Other findings, which are less specific for dissection but have been described, include widening of the aortic contour,
displaced calcification, aortic kinking, and opacification of the aorticopulmonary window [86]. Hemothorax may be seen if the dissection extends
through the adventitia, with hemorrhage into the pleural space, which can lead to exsanguination.
However, because of the limited sensitivity of the chest radiograph, especially in type B dissections, additional imaging studies are obtained in
almost all patients (98 percent in data from IRAD) [3,81,86]. (See 'Cardiovascular imaging' below.)
Laboratory studies — Serum markers for acute aortic dissection are emerging as a diagnostic option, particularly in screening patients in the
setting of differentiating chest pain where the cost of widespread cardiovascular imaging would be prohibitive.
D-dimer — D-dimer is a degradation product of cross-linked fibrin and reflects activation of the extrinsic pathway of the coagulation cascade
by tissue factor exposed in the aortic media by the intimal tear. As such, D-dimer has emerged as a potential serum marker for acute dissection
[87]. However, as a nonspecific indicator of intravascular coagulation, D-dimer can be elevated in many conditions (table 2). D-dimer appears to
be a useful screening tool to identify patients who do not have acute aortic dissection. A widely-used cutoff is 500 ng/mL; a level below this
value is highly predictive for excluding dissection [87].
The systematic review identified seven studies that used assays for plasma D-dimer to screen patients for acute aortic dissection and included a
control group [88]. For D-dimer <500 ng/mL, the pooled estimate of the sensitivity was 97 percent, specificity was 56 percent, and negative
predictive value was 96 percent. This study and others have concluded that patients with a D-dimer <500 ng/mL are not likely to benefit from
further aortic imaging [87,89-97]. However, caution should be exercised in the application of D-dimer levels as some authors have reported up to
18 percent of patients with confirmed aortic dissection may have levels <400 ng/mL [89]. While D-dimer testing carries a sensitivity of 90 to 95
percent, a meta-analysis suggests that its very low specificity, a lack of standardized testing protocols, and the variability of levels from the time
since onset of symptoms should limit its usage to patients at low risk for having aortic dissection but in whom there remains a clinical diagnostic
uncertainty [98].
Other experimental tests — Other experimental tests include measurements of soluble elastin fragments, smooth muscle myosin heavy

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chain, high-sensitivity C-reactive protein, fibrinogen, and fibrillin fragments [99-102].
A rapid 30-minute immunoassay for the serum concentration of smooth muscle myosin heavy chain has been evaluated in patients suspected of
having an aortic dissection [100,101]. The sensitivity and specificity of this assay in the first three hours were similar and possibly superior to
those of transthoracic echocardiogram, conventional computed tomography (CT), and aortography but were lower than those of
transesophageal echocardiogram, helical CT, or magnetic resonance imaging. The utility of this test needs further evaluation.
DIAGNOSIS — The diagnosis of aortic dissection may be suspected clinically based upon the presence of high-risk clinical features (discussed
above), but confirmation of the diagnosis requires cardiovascular imaging that demonstrates the dissection flap separating a false lumen from
the true lumen (image 5 and image 8). (See 'Cardiovascular imaging' below and "Management of acute aortic dissection".)
It is important to rapidly distinguish acute ascending thoracic aortic dissection, which is a cardiac surgical emergency, from descending thoracic
aortic dissection, which is managed medically in hemodynamically stable patients who do not have end-organ complications. In general, imaging
studies should not be performed until the patient can be initially stabilized. (See "Management of acute aortic dissection" and "Surgical and
endovascular management of type B aortic dissection".)
High-risk clinical features — Many studies have sought to identify which of the clinical features presented above are most reliable for
predicting aortic dissection to avoid a missed or delayed diagnosis [58,103-106]. An analysis of 250 patients with acute chest and/or back pain
(128 with a dissection) found that 96 percent of acute aortic dissections could be identified based upon three clinical features [107]:
● Abrupt onset of thoracic or abdominal pain with a sharp, tearing, and/or ripping character
● A variation in pulse (absence of a proximal extremity or carotid pulse) and/or blood pressure (>20 mmHg difference between the right and
left arm)
● Mediastinal and/or aortic widening on chest radiograph
The probability of a dissection related to the presence or absence of these three were:
● Isolated pulse or blood pressure differential, or any combination of the three: ≥83 percent
● Presence of mediastinal widening: 39 percent
● Pain alone: 31 percent
● All three absent: 7 percent
Ascending versus descending aortic involvement — Management of aortic dissection depends on the level or aortic involvement and
etiology (table 3). Aortic dissection involving the ascending aorta is a surgical emergency. Dissection limited to the descending thoracic and/or
abdominal aorta is managed medically, unless there is evidence for malperfusion. (See "Management of acute aortic dissection", section on
'Type and etiology of dissection'.)
Certain clinical features suggest involvement of the ascending versus descending aorta (table 1).
● Ascending aorta: Pain located in the chest more so than the back or abdomen [3]. Other clinical features include acute aortic valve
regurgitation, acute coronary syndrome, cardiac tamponade, hemothorax, focal neurologic deficits related to cerebrovascular ischemia, and
upper extremity pulse deficit [6,32]. As most type A dissections include a distal extent to the abdomen, descending aortic manifestations
may be included too.
● Descending aorta: Pain is located in the posterior chest/upper back and may radiate to the abdomen [3]. Other clinical features include
evidence of malperfusion syndromes such as abdominal pain from visceral ischemia, renal insufficiency, lower extremity ischemia, and focal
neurologic deficits related to spinal ischemia [6,81,108].
Cardiovascular imaging — Our recommendations for cardiovascular imaging are generally in agreement with multidisciplinary consensus
guidelines [38,39]. Multiple imaging modalities can be used to demonstrate the dissection, including magnetic resonance (MR) angiography,
computed tomographic (CT) angiography, and multiplane transesophageal echocardiography (TEE) [109]. Each has its advantages and
disadvantages, and one may be more appropriate for selected patient populations as an initial study.
CT is the most common initial choice due to its widespread availability, particularly in the emergency department setting. More than one study is
often needed to obtain all the necessary information to fully guide treatment. In one International Registry of Acute Aortic Dissection (IRAD)
review, patients had an average of 1.83 studies per patient [3]. The initial study was CT in 61 percent, TEE in 33 percent, aortography in 4
percent, and MR in 2 percent. The availability of some studies may be limited, and accuracy depends upon the performance and interpretation
of the test by skilled individuals, and as such, the studies chosen may differ from institution to institution.
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Clinical features and diagnosis of acute aortic dissection - UpToDate

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The imaging diagnosis of aortic dissection is based on the presence of an intimal flap separating a false lumen from a true lumen, and
associated complications [6,110-113]:
● The intimal flap (image 5 and image 9 and image 10)
● True and false lumen (image 11A-B)
● Involvement of the ascending aorta (image 12)
● The extent of dissection and the sites of entry and reentry
● Thrombus in the false lumen
● Branch vessel involvement
● Coronary artery involvement
● Aortic valve regurgitation
● Pericardial effusion
Hemodynamically unstable — For hemodynamically unstable patients or those with clinical features suggestive of ascending aortic
involvement, we suggest transesophageal echocardiography (TEE) as an initial study in patients with suspected aortic dissection, wherever
available. TEE is a portable procedure that yields a diagnosis within minutes and is easily performed in the emergency department [114]. The
sensitivity of TEE has been reported to be as high as 98 percent, and the specificity ranges from 63 to 96 percent [115,116]. The ascending
aorta is typically assessed at approximately 130 degree orientation while the arch and descending thoracic aorta are assessed at 0 degrees.
Biplane imaging may be useful.
The advantages of TEE include generally wide availability, ease of use, and bedside capability. In addition, TEE can detect entry tear sites, false
lumen flow/thrombus, involvement of the arch or coronary arteries, degrees of aortic valvular regurgitation, and pericardial effusions. The
addition of color flow Doppler patterns may decrease false positives by recognizing differential flow velocities in the true and false lumens that
may assist in the diagnosis of malperfusion syndromes.
A disadvantage of TEE is that it requires esophageal intubation, which usually requires procedural sedation, which may have untoward effects in
hemodynamically unstable patients. TEE requires the availability of experienced operators (both physicians and technicians) to ensure accurate
results. As such, it is often not attainable on a "stat" basis in many centers. The theoretical technical limitation of TEE is the anatomic "blind
spot" in the distal ascending aorta and proximal arch secondary to the air-filled trachea and left main stem bronchus, and inability to document
dissection extension beyond the diaphragm that may be causing malperfusion of abdominal aorta branches. Despite these shortcomings, TEE
can be particularly useful in delineating acute dissection and relevant surgical pathology in the ascending aorta, and therefore, it is chiefly
applied in this territory. Moreover, in the unstable patient with a suspected acute dissection in the ascending aorta, TEE may be performed in the
operating room to expedite diagnosis and definitive therapy. In the IRAD study, TEE was employed second most frequently (after CT) in the
diagnosis and workup of an acute aortic dissection [116].
The following findings may be seen on TEE in patients with aortic dissection [54,113,114]:
● Intimal dissection flaps can be identified with high spatial resolution (image 10 and movie 2). The use of M-mode echocardiography may
improve diagnostic accuracy by demonstrating a lack of relation between movement of the intimal flap and the aortic wall [117].
● The true and false lumens can be identified. They may not be distinguishable without color Doppler imaging or identification of the proximal
border of the dissection. However, in some cases, the false lumen can be seen to surround the true lumen (movie 3 and movie 4). Color
Doppler permits clear identification of flow within and between the true and false lumens (image 10 and movie 5). The presence of flow
does not absolutely distinguish the true lumen from the false lumen. The true lumen has an endothelial lining and is contiguous with the
aortic valve.
● Thrombosis in the false lumen, pericardial effusion, concomitant aortic regurgitation, and the proximal coronary arteries can be readily seen.
● The 135 degree long axis view from TEE can define the severity and mechanism of aortic regurgitation that complicates acute type A
dissection [83]. Patients with an intrinsically normal valve who have aortic regurgitation due to a correctable aortic lesion (incomplete leaflet
closure, leaflet prolapse, or dissection flap prolapse) can undergo aortic valve repair (movie 6). By contrast, abnormalities that cannot be
repaired (eg, Marfan syndrome, bicuspid valve, aortitis) will require valve replacement. (See "Management of acute aortic dissection".)
A less favorable alternative to TEE is transthoracic echocardiography (TTE), which can quickly identify ascending aortic dissection, particularly
coexistent aortic valve disruption/regurgitation and hemopericardium (movie 7 and movie 8) [53,114,118]. The primary disadvantage with TTE is
its inability to adequately visualize the mid- and distal ascending, transverse arch, and descending aorta, or the presence of other complications
in a substantial number of patients. Furthermore, the sensitivity and specificity of TTE are inferior to CT angiography, MR angiography, and TEE.
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Clinical features and diagnosis of acute aortic dissection - UpToDate

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Hemodynamically stable — For hemodynamically stable patients without clinical features suggesting ascending aortic involvement, we
obtain CT angiography as an initial study in patients with suspected aortic dissection, particularly in the emergency department setting where
other studies are less available. The majority of patients with suspected acute aortic dissection should be evaluated with both chest and
abdominal dynamic contrast-enhanced fine-cut CT scanning. In comparison with other modalities, CT scanning is the least operator dependent,
provides useful anatomic correlates for surgical and endovascular therapy, and collects information for follow-up analysis and measurement.
Most importantly, three-dimensional CT scan reconstructions can aid treatment planning, and axial imaging affords the best opportunity to detect
topographic relationships of the true and false lumens and potential aortic branch compromise.
CT scanning has a reported sensitivity of 83 to 95 percent and specificity of 87 to 100 percent for the diagnosis of acute aortic dissection
[114,119,120]. The chief limitation of imaging is the ascending aorta, where the sensitivity may drop to <80 percent, as contrast enhancement
can be dependent on timing of the injection. As an example, a CT scan to evaluate for initially suspected pulmonary embolus as a source of
chest pain may or may not time correctly for assessment of the ascending aorta. The accuracy of CT may be substantially improved with spiral
(helical) CT and perhaps with multidetector (multislice) CT [121-124]. Spiral CT may be more accurate than MR or TEE for the detection of aortic
arch vessel involvement [121]. A potential limitation is a spiral CT artifact that can simulate an aortic dissection flap in patients if performed
without echocardiogram (ECG) gating [125-127]. Thus, ECG-gated scanning is recommended when available. Advantages of CT include ready
availability at most hospitals, even on an emergency basis, and identification of intraluminal thrombus and pericardial effusion. Two
disadvantages of standard CT are that the intimal flap is seen in less than 75 percent of cases and that the site of entry is rarely identified [128].
In addition, potentially nephrotoxic iodinated contrast is required, and there is no capability to assess for aortic insufficiency. If the CT is
equivocal, or further delineation of the dissection is needed, MR angiography or TEE is indicated.
The diagnosis of aortic dissection by CT scanning requires the identification of two distinct lumens; the intimal flap may or may not be
demonstrated. In most cases, the true lumen may be localized by its continuity with an undissected proximal or distal segment of the aorta. The
presence of intraluminal thrombus is a good marker of the false lumen, but in patients with a concomitant degenerative aneurysm, thrombus
may be present in the true lumen. In the majority of cases, the false lumen is larger than the true lumen [120]. A compressed true lumen is the
key radiographic finding, which should substantially raise the index of suspicion for renal/visceral/lower extremity malperfusion syndrome.
Curving of the dissection flap into the true lumen is seen in 63 percent of acute type B dissections but only 25 percent of chronic dissections
[120]. Indeed, it may be appropriate, if open surgical intervention is chosen as the revascularization procedure, to proceed directly to surgery
after CT alone in circumstances where the clinical and/or laboratory signs dictate the need for urgent revascularization, as in evidence of bowel
ischemia or vascular rupture.
For hemodynamically stable patients, MR angiography is an alternative to CT angiography, depending on availability [127,129]. Although less
commonly used, MR angiography is highly accurate for diagnosing aortic dissection. Gadolinium-enhanced MR angiography has an overall
sensitivity and specificity to diagnose aortic dissection of 95 to 100 percent [130]. In a prospective trial of 110 patients, MR angiography had 85
percent sensitivity for identifying the site of entry [114]. MR angiography can also detect differential flow between the true and false lumens.
Additional suggestive findings include widening of the aorta with a thickened wall and thrombosis of the false lumen. The chief advantage of MR
angiography is avoiding excess radiation exposure, and it can be afforded in the long-term serial studies required in the standard surveillance of
type B dissection patients. MR is safe in adequately monitored patients with aortic dissection, and MR contrast agents have a more favorable
safety profile than iodinated contrast agents. Noncontrast MR angiography is another option. Other advantages of MR include the ability to
assess branch vessels, although it may be less sensitive than spiral CT [121], and to assess for aortic insufficiency. The main disadvantages of
MR imaging are inconvenience (patients are required to remain motionless with relatively limited access for more than 30 minutes) and limited
applicability (MR imaging cannot be performed in patients with claustrophobia, pacemakers, or certain types of aneurysm clips or metallic
ocular/auricular implants). MR is also not readily available on an emergency basis at many institutions, and there are concerns about patient
monitoring and relative patient inaccessibility during prolonged scanning. Gadolinium administration for contrast-enhanced MR imaging in
patients with moderate-to-severe kidney disease (particularly dialysis patients) should be avoided. The accuracy of noncontrast MR angiography
for aortic dissection has been less well defined. (See "Nephrogenic systemic fibrosis/nephrogenic fibrosing dermopathy in advanced renal
failure".)
Role of aortography — Formerly the gold standard for the diagnosis of aortic dissection, aortography has largely yielded to CT angiography
in the initial diagnosis of aortic dissection. In the endovascular management of dissection, it is used mainly as a component of an interventional
treatment strategy. However, for patients in whom the suspicion for ascending aortic dissection is very strong but noninvasive imaging is
unavailable or inconclusive, digital subtraction aortography should be performed. Aortography involves the injection of iodinated contrast media
into the aortic lumen, permitting identification of the site of dissection, the relationship between the dissection and the major branches of the
aorta, and the communication site between the true and false lumen (image 13) [113].
Findings on aortography considered supportive of a diagnosis of aortic dissection include distortion of the normal contrast column, flow reversal
or stasis into a false channel, failure of major branches to fill, and aortic valvular regurgitation. Most contemporary diagnostic algorithms have
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