Acute Aortic Dissection: Update on Diagnosis and Application of Endovascular Therapy of Emergency-Juniper Publishers
JUNIPER PUBLISHERS-OPEN ACCESS JOURNAL OF CARDIOLOGY & CARDIOVASCULAR THERAPY
Abstract
Acute aortic syndrome (AAS) describes emergency
aortic diseases. In 80% of patients, the AAS presents itself as an Acute
Dissection of Aorta (ADA). It’s worth pointing out that the traumatic
etiology of this condition has great relevance regarding morbidity and
mortality. This is fact that the Traumatic Thoracic Aortic Dissection
(TTAD), usually occurs from a contuse injury, product of an abrupt
deceleration, especially in men and individuals with overweight or
obesity, which have a history of smoking and heart surgeries. Early
diagnosis of ADA is indispensable, since patients who arrive alive at
the hospital, have high probability of death in a short period of time
if not treated properly, especially those who have been victims of some
traumatic event earlier. In this context, the endovascular approach has
become the treatment of choice for acute surgical emergencies involving
the descending thoracic aorta. Moreover, it should be considered as a
first-line option in the conduct of any emerging conditions that involve
this region of the aorta. It is important to note that the longevity
and durability of this technology throughout the life of young patients
remains to be elucidated.
Introduction
Acute Aortic Syndrome (AAS) is a term used to
describe emergency aortic disorders, with regard to its characteristics
and challenges. Because of this, one can cite: acute aortic dissection
(AAD), intramural hematoma (IH) and penetrating atherosclerotic ulcer
(PAU). The incidence of this syndrome is three cases per 100,000 people
per year. Of all patients who present with a SAA, 80% are AAD, 15% HI
and 5% corresponds to the PAU [1].
Most patients, who arrive alive at the hospital, if
they are not subjected to a systematic approach and conducive situation,
have a high probability of death in a small time interval [2]. As AAS
occurs through an injury to the wall of this artery due to a certain
type of stress or even medial degeneration, it is essential to know the
risk factors that can cause this fragility [3].
The conditions associated with the medial
degeneration include Marfan syndrome, Loeys-Dietz syndrome,
vascularEhlers-Danlos syndrome, inflammatory diseases of the aorta,
Turner syndrome, bicuspid aortic valve, familiar syndrome of thoracic
aortic aneurysm and dissection [4]. The most common condition that
increases the stress of wall is hypertension. Other conditions involved
in the dissection include: history of trauma, weight lifting,
pheochromocytoma, coarctation and cocaine [4].
Meet the clinical signs are essential, once, tied to
imaging tests, they become important allies to diagnose or rule out a
leave according to the technology available in-service [5]. In addition,
in a patient with hemodynamic stability studies, graduating from injury
is essential to direct more productive and effective conduct. The image
examinations for your time, besides being favorable for the diagnosis,
can assist in choosing the best surgical technique. If there are no
unfavorable anatomical changes, the choice of approach will depend on
the patient’s hemodynamic condition, availability of resources and
professional skill in question [5-7].
From this reality, this article has as purpose, do a literature
review on the acute aortic dissection, clarifying the main
and latest methods of diagnostic and therapeutic approach.
In addition, underscores the urgent need, the preparation of
the team on admission of patients affected by this disease, so
that it is possible to decrease the incidence of undiagnosed
cases, optimizing the time between the initial approach and
appropriate conduct [8].
This work was done from an electronic search in the
databases Pub Med, Scopus, Scielo and Embase Search Portal.
We collected data from case reports, cohort studies and literary
reviews, using the key words: acute aortic syndrome, acute
aortic dissection, dissection of aorta, endovascular repair. The
method presented the following guiding question: ‘‘what are
the main results and scientific evidence identified in national
and international bibliographical production of the last 26
years pertaining to diagnostic and therapeutic approach of
acute aortic dissection?’’
In the initial survey, the articles went through the
evaluation of nine researchers (authors), in accordance
with the following inclusion criteria: articles published in
Portuguese, English or Spanish, to submit the combinations
of the keywords selected, with publication date between
1989 and 2015 that were accessible. After the initial selection
of material, were deleted the articles repeated in different
databases and they focus on the aortic pathologies other mixed
in question. Although picked by articles that cover effective
updates in the treatment, the therapeutic failure was not used
as a criterion for deletion, considering the particularity of the
manifestations of each case. The final material featured 46
scientific articles.
The AAD is a potentially fatal condition that requires
rapid assessment and intervention. However, despite the
great advances in imaging methods and non-invasive studies,
the correct diagnosis is not always the rule, therefore the
diagnosis errors often occur [9]. Approximately 30% of cases
are found in post-mortem exams8. Patients with this disease
presents to the Emergency Department with a wide variety of
symptoms, due to the involvement of multiple organ systems
[10]. However, there are occasions when the medical history is
insufficient to know the frame.
The patient may complain of chest pain, pain in
interescapular region, dyspnea and dysphagia [3]. The physical
examination may show signs suggest chest trauma, such as the
seatbelt sign, heart murmur, hematemesis, palpable depression
or deformity of the sternum. As well: stridor, crepitation in
chest wall, grinding noise on the precordium (Hamman signal),
hematoma subclavian and femoral pulses decreased [3].
If the patient is hemodynamically unstable must be
forwarded immediately to the operating room [11]. Stable
patients can be investigated more precisely through Imaging
tests.
The evolution of technology has resulted in highly sensitive
diagnostic tools and specific, however, the widespread use of
these diagnostic methods, results in an increase in the number
of false positives. Such limitations should be considered in
clinical decisions, and it is important that additional tests in
patients hemodynamically stable [12].
The international registry of aortic dissection (IRAD)
lists the computed angiotomography (ATC) as the first most
common diagnostic test on suspicion of aortic dissection
(about 61%), followed by Transthoracic echocardiography
and Transesophageal (ETT and ETE) (around 33%),
magnetic resonance imaging (MRI) (around 2%), in addition
to angiography corresponding to 4%. This reflects their
availability and accessibility of these modalities [13] (Figure
1).
The chest x-ray in supine antero-posterior position can
be useful, since in an initial assessment, despite having
low sensitivity, shows signs that direct the diagnosis or the
need for other tests [5]. These evidences are: widening of
the mediastinum (>8cm); abnormal aortic contour; deletion
of aortic button; orotracheal tube and trachea deviation
to the right; source left bronchus depression; diversion of
nasogastric tube to the right; extrapleural apical leakage; a
density; fracture of the first and second ribs; obliteration of the
space between the pulmonary artery and aorta; elevation and
deflection to the right of the right main bronchus; hemothorax.
The helical computed tomography (CT) of chest no cuts must be
indicated after the fine interpretation of trauma mechanisms
[3]. Is the most common initial examination because it is less
invasive and allows quick diagnosis in emergency situations
[14]. Is an excellent method for diagnosis to triage patients
with suspected aortic injury, showing a sensitivity ranging from 93% to 100% and specificity of 87% to 100% [3,15,16]
(Figure 2).
The minimally invasive transesophageal echocardiography,
is widely available, secure, and can be accomplished quickly
and easily on the edge of the bed or in the operating room before
the operation. These advantages make this ideal for use in most
patients with aortic dissections, including those relatively
unstable. The examination can be carried out immediately
after the patient to come to the Emergency Department. Their
sensitivity ranges from 95% to 98% and specificity of 63% to
96% [17,18]. The most important discovery in the diagnosis
of aortic dissection, which can be seen in this survey, is the
presence of a border rippling intimal within the lumen of the
aorta, which differentiates a false lumen light real [19].
The arteriography was used for many years as the mode
of choice to demonstrate the aortic dissection. Is an effective
procedure to demonstrate the direct signals of dissection, the
flap of the intimate and blood flow in the true and false lumens
[19]. Erbel et al. [17] reported 88% sensitivity and specificity of
94% for this examination in the diagnosis of aortic dissection.
However, for being an invasive method, became a secondary
diagnosis mode.
Magnetic resonance imaging (MRI) is a non-invasive
research, providing an excellent analysis of the valvar
pathologies, and aortic coronary involvement. Although it is the
most accurate, sensitive and specific between the four modes
of diagnosis [16], your use is limited in emergency situations,
in patients hemodynamically unstable, as well as in patients
with Implantable devices. That way, she will eventually
cede space to the computed angiotomography methods and
echocardiography in emergency cases [20]. Has sensitivity around 95% and specificity of 100% [21]. The advantage of
MRI over CT is your ability to provide functional information
such as valve failure and left ventricular dysfunction [19]
(Figure 3).
The use of quantitative tests of D-Dimer serum, have
been proposed as a strategy toward off aortic dissection [22].
Proponents of this approach suggest that the blood in the false
light activates the coagulation cascade by generating fibrin
degradation products. These are detected by modern D-Dimer
assays with high sensitivity. Unfortunately, the work has
demonstrated high false negative rate. In one study, D-Dimer
presented false negatives in 9 of 113 confirmed cases of aortic
dissection [23].
The proposed explanation for D-Dimer tests false
negatives, is the occurrence of an anatomical variation of aortic
dissection, whose thrombosed lumen, does not communicate
with the circulating blood, isolating the clot detection by serum
tests. In addition, there is no evidence that D-Dimer can be
incorporated into a strategy of risk stratification, which would
allow the sensitive clinical enough to exclude aortic dissection,
without significantly increasing the number of patients
who receive advanced imaging tests. Given the experience
of D-Dimer testing to rule out pulmonary embolism-which
increased the number of advanced studies of image without
increasing the number of diagnoses of pulmonary embolism
[24]. A comprehensive approach to answer for false negatives
and false positives should be validated before this exam to be
used routinely in the diagnosis of aortic dissection.
The initial treatment has as main objective to reduce the
shear stress in the wall of the aorta, through the control of
blood pressure. The first line of treatment are beta blockers
intravenously (labetalol or propranolol). Those with
contraindication for this drug class (asthma) [25], is preferable
to the use of intravenous calcium channel blocker (verapamil
or diltiazem). Because of this, it is necessary to get a systolic
blood pressure that oscillates between 100 and 120mmHg, as well as a range of heart rate between 60 and 80bpm. Besides,
we recommend the use of an opioid analgesic (morphine), to
reduce sympathetic discharge produced by catecholamines.
These are generated by pain, due to the hypertension and
tachycardia [26].
It is worth mentioning that the initial conduct in stable
patients depends on the degree of the injury established after
CT 5.6. There are four ranks: tipo I-intimate layer, without
blood extravasation; type II - intramural hematoma; type III
- pseudoaneurysm; type IV - break free/periaortic hematoma.
In milder cases (type I), opts for the use of beta blockers
for fast action and short half-life, decreasing blood pressure
and keeping your heart rate below 100bpm, if they are
contraindicating, a calcium channel blocker or associated with
intravenous nitroglycerine if there is the effect objectified. In
addition, it is necessary to perform Imaging exams serials to
accompany the evolution of the injury. In more severe lesions
(types II, III and IV), as well as volume replacement and blood
pressure control, surgical repair is required for open or
endovascular technique [5,6].
Regarding surgical techniques, we can cite the open
technique based on a left thoracotomy in cases of injury of
the descending aorta or sternotomy in patients with injury
of the ascending aorta for primary repair of the aorta or the
replacement of the affected segment by a graft or graft [7]. In
the descending aorta lesions, should be made the establishment
of diversion of blood flow through centrifugal pumps and
cannulation of the left atrium and left common femoral
artery, as well as systemic heparinization. This technique is
preferable in patients with unfavorable anatomy [7]. It’s worth
pointing out that many patients do not survive the initial event,
consequently does not undergo a repair attempt.
Endovascular thoracic aortic repair (TEVAR) refers to the
minimally invasive approach, which involves placing a stent
graft in thoracic aorta or ring, possessing ample indications.
The technique involves inserting modular grafts through
the dissection of iliac or femoral arteries to thoracic aorta
excluding vessel damage [7] (Figure 4 & 5).
In the case of femoral arteries, after dissection of the
right femoral puncture of femoral artery left there for the
introduction of catheter, where there is the diameter of the
aorta and if intralaminar defects are excluded, when inserted
into the stent. Is recommended in victims with favorable
anatomy, and has a more comfortable postoperative period
and brief [7].
A series of studies, has suggested various subgroups of highrisk
patients without complications, which can benefit from
early TEVAR. The specific predictors of early or late adverse
events have been identified in multiple studies, and include: an
aortic diameter of 4.0cm home, with a false light patent [27-
29], an initial diameter of 22mm light on proximal descending
aorta [30], refractory/recurrent pain or hypertension [31] or
intramural hematoma with a penetrating atherosclerotic ulcer
development in the proximal descending aorta [27,29].
About the disasters involving the descending thoracic
aorta, the management have been particularly difficult for
surgeons. The open surgical correction in these cases is
the gold standard. However, is associated with significant
mortality and morbidity. This makes this procedure, one of the
most risky and difficult to be carried out by vascular surgeons
[32].
The widespread application of endovascular repair,
for the treatment of acute surgical emergencies involving
the descending portion of the aorta, resulted in a dramatic
decrease of both the operative mortality as post procedure
morbidity [33]. The open repair for traumatic rupture of the
aorta, is associated with an operative mortality of up to 28%
and 16% rate of paraplegia [33]. While a systematic review
of literature on endovascular therapy, reveals an overall rate
of 9% and a mortality rate of 3% of the paraplegia analyze
7768 patients undergoing the procedure in effect of traumatic
dissection of aorta [34].
Recently published guidelines for the Society for
Vascular Surgery, with practical guidelines that suggest that
endovascular procedure must be standard therapy for the
treatment of traumatic rupture of the thoracic aorta [32]. Thus,
the endovascular approach has become the treatment of choicefor acute surgical emergencies, involving the descending
thoracic aorta. Moreover, it should be considered as a first-line
option in the conduct of any emerging conditions that involve
this region of the aorta [35].
Endovascular repair brings advantages and limitations.
Among the advantages described, include: avoid the
thoracotomy, decrease the incidence of complications less
painful, faster recovery, shorter stay in intensive care
and in hospital, an alternative for high-risk patients, less
postoperative complications, useful in emergency situations
and speed and agility of treatment [36].
Among the limitations found: institutional and political
constraints, limited availability and accessibility, unavailable
commercially in some countries, the appropriate requirement
of vascular anatomy, limited number of qualified operators,
lack of appropriate follow-up and palliative care in most cases
[36].
However, endovascular correction is not without risks.
This procedure is associated with a small but measurable rates
of stroke (2% of cases), spinal cord ischemia (0.9% of cases),
reported in the trials and meta-analysis that investigated this
type of therapy [37-40].
In addition, endovascular procedures are associated with
higher rates of complications related to the device. They are
expensive and require an extended image tracking. In addition,
the longevity and durability of this technology throughout the
life of young patients remains to be elucidated [38]. In the first
month, post-operative angiography should be performed by a
CT scan, followed by study of image in six months, and then
annually. TEVAR in patients with non-optimal anatomy for the
procedure, requires more rigorous follow-up. The realization
of the computed tomography without contrast allows the
measurement of the diameter of the bag and is enough in most
cases to document effective aneurysm exclusion [41].
Magnetic resonance angiography is an alternative, although
it is of limited applicability in patients with significant renal
dysfunction [41]. A secondary is relatively common aortic
intervention after the endovascular repair [42,43].
According to the American Heart Association guidelines on
the management of thoracic aortic diseases, we have that the
acute aortic dissection can be categorized in a patient of high,
medium and low risk according to clinical presentation [44]. In
cases of high risk or intermediate probability, one must quickly
make the injury screening with imaging to visualize the aorta.
Obtaining a negative result, opts for another investigation. The
cardiac ultrasound is offered by AHA as secondary technique
more common [20].
It’s worth pointing out that a CT must be part of the presurgical
routine, as well as being performed by a trained and
highly experienced cardiologist or cardiac anesthesiologist.This procedure is required in all patients with suspected acute
aortic dissection type A [10].
The work performed by Tiwari et al. [42] discusses several
puncture techniques that were proposed in the establishment
of the cardiopulmonary bypass (CPB) for the surgery of acute
type aortic dissection. Despite the concern with the fragility
of the vases, and distal embolization during ascending aortic
cannulation of a dissected aorta, there were promising
results, with a lower mortality rate and lower incidence of
poor perfusion. However, it was observed a higher rate of
stroke. A total of seven studies evaluated the use of direct
aortic cannulation for the establishment of the extracorporeal
circulation (EC). They have shown and stroke mortality rates
from 0% to 15% and 3.8% and 21%, respectively. The direct
cannulation of the true light is an emerging method for quick
and easy establishment of EC [45].
Although the femoral artery puncture is the default option
in many centers, there is a higher rate of mortality of stroke
and other complications, including cerebral embolization bad
organ perfusion retrograde perfusion of the false light. In
this work, five of the 14 studies analyzed, reported benefits
of axillary artery cannulation (or subclavian). In a total
of 1829 patients evaluated in these studies, 1068 patients
demonstrated a significantly lower rate of complications with
the axillary artery cannulation in comparison with the femoral
artery [45].
Some large studies have shown that the femoral artery
cannulation have high rates of stroke and mortality ranging
from 6.5% to 40%, and 3% to 17%, respectively. Mean while,
and mortality rates of stroke ranged from 3% to 8.6% and
1.75% and 4%, respectively, in the axillary artery cannulation
procedure [44]. This new strategy emerges as a more efficient
method for the EC, providing unilateral continuous blood
flow without interruption. Although need more time for your
accomplishment, the axillary artery with lateral graft, proved
to be safe and straightforward, with less local and systemic
complications, lower mortality and reduction of neurological
complications [45].
It is important to note that in the case of hemodynamic
stability, and the patient in question is subject to a traumatic
brain injury or multiple severe injuries in other systems
coexisting, but there is no indication of impending rupture
of the aorta, aortic, pneumothorax massive thrombus or
pseudoaneurysm, thoracic aortic repair chosen must be
conservative (pharmacological control of arterial pressure) to
stabilization of other injuries or comorbidities by decreasing
the amount of anesthetic held, as well as the surgical risk [5,6].
Most of the patients are victims of a ruptured aorta after an
accident, die immediately. However, the small portion survivor,
has about 24h for that light to rupture. As the clinical findings are nonspecific and poor, shows need for greater professional
skill, regarding the efficient diagnosis, rapid and appropriate
treatment to approach this serious pathology.
It is important to point out that when we are facing a
situation of hemodynamic stability and the first-rate research
results are conflicting, it is necessary to refer the patient to a
high level of investigative rigor before surgical intervention.
An alternative to conventional surgical treatment is the use
of endoprothesis, reserved for patients properly selected.
In addition, it is essential the image exams serials, as well as
medical follow-up according to age, co-morbidities and patient
kidney function.
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