Aortic dissection

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Aortic dissection

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Aortic dissection

• Incidence 2000 cases per year in the United
  States
• Mortality Early mortality is as high as 1 per
  cent per hour if untreated
• Mechanisms Aortic dissection is believed to
  begin with the formation of a tear in the aortic
  intima that directly exposes an underlying
  diseased medial layer to the driving force (or
  pulse pressure) of the intraluminal blood.

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Aortic dissection

• CLASSIFICATION.
• There are three major classification systems to
  define the location and extent of aortic
  involvement,
• (1) DeBakey types I, II, and III
• (2) Stanford types A and B
• (3) anatomical categories proximal and distal.

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Aortic dissection

• TYPE SITE OF ORIGIN AND EXTENT OF
  AORTIC
• INVOLVEMENT
• DeBakey
• Type I Originates in the ascending aorta,
  propagates
• at least to the aortic arch and often
  beyond it
• distally
• Type II Originates in and is confined to
  the ascend-
• ing aorta
• Type III Originates in the descending aorta
  and ex-
• tends distally down the aorta or, rarely,
  ret-
• rograde into the aortic arch and ascending
• aorta

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Aortic dissection

• Stanford
• Type A All dissections involving the
  ascending aorta,
• regardless of the site of origin
• Type B All dissections not involving the
  ascending
• aorta
• Descriptive
• Proximal Includes DeBakey types I and II
  or Stanford
• type A
• Distal Includes DeBakey type III or
  Stanford type B

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Aortic dissection
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Aortic dissection

• ETIOLOGY AND PATHOGENESIS.
• Medial degeneration, as evidenced by
  deterioration of the medial collagen and elastin,
  is considered to be the chief predisposing factor
  in most nontraumatic cases of aortic dissection.
• In fact, the Marfan syndrome accounts for 6 to 9
  per cent of all aortic dissections.
• The peak incidence of aortic dissection is in the
  sixth and seventh decades of life, with men
  affected twice as often as women.
• An unexplained relationship exists between
  pregnancy and aortic dissection. About half of
  all aortic dissections in women under 40 years of
  age occur during pregnancy, typically in the
  third trimester and also occasionally in the
  early postpartum period.

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Aortic dissection

• SYMPTOMS
• By far the most common presenting symptom of
  acute aortic dissection is severe pain, found in
  74 to 90 per cent of cases
• whereas the large majority of those presenting
  without pain are found to have chronic
  dissections.
• The pain is typically of sudden onset, and is as
  severe at its inception as it ever becomes,
  contrasting with the pain of myocardial
  infarction, which usually has a crescendo-like
  onset.
• The quality of the pain as described by the
  patient is often morbidly appropriate to the
  actual event, with adjectives such as
  "tearing",ripping",and "stabbing" frequently
  used.
• Another important characteristic of the pain of
  aortic dissection is its tendency to migrate from
  its point of origin to other sites, generally
  following the path of the dissection as it
  extends through the aorta.
• Such migratory pain was noted in 70 per cent of
  our cases.130
• Less common symptoms at presentation, occurring
  with or without associated chest pain, include
  congestive heart failure, syncope,
  cerebrovascular accident, ischemic peripheral
  neuropathy, paraplegia, and cardiac arrest or
  sudden death.

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Aortic dissection

• PHYSICAL FINDINGS
• Hypertension is seen in more than 80 to 90 per
  cent of those with distal aortic dissection but
  is less common in proximal dissection.
• Hypotension, on the other hand, occurs much more
  commonly among those with proximal than distal
  aortic dissection.
• True hypotension usually is the result of cardiac
  tamponade, intrapleural rupture, or
  intraperitoneal rupture.
• pseudohypotension Dissection involving the
  brachiocephalic vessels may result in
  pseudohypotension, an inaccurate measurement of
  blood pressure due to compromise or occlusion of
  the brachial arteries.
• The physical findings most typically associated
  with aortic dissection pulse deficits,
• Aortic regurgitation is an important feature of
  proximal aortic dissection, with the murmur of
  aortic regurgitation detected in anywhere from 16
  to 67 per cent of cases

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• Mechanisms of aortic regurgitation in proximal
  aortic dissection.A, An extensive or
  circumferential tear dilates the aortic root and
  annulus, preventing the aortic valve leaflets
  from coapting. B, With asymmetrical dissection,
  pressure from the false lumen depresses one
  aortic leaflet below the coaptation line of the
  other leaflets. C, The annular support is
  disrupted, resulting in a flail aortic leaflet.
  D, Prolapse of a mobile intimal flap through the
  aortic valve during diastole prevents leaflet
  coaptatio

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Aortic dissection

• PHYSICAL FINDINGS
• Neurological manifestations occur in as many as 6
  to 19 per cent of all aortic dissections but are
  more common with proximal dissection.
• Cerebrovascular accidents may occur in 3 to 6 per
  cent when there is direct involvement of the
  innominate or left common carotid arteries.
• Less frequently, patients may present with
  altered consciousness or even coma.
• When spinal artery perfusion is compromised (more
  common in distal dissection), ischemic spinal
  cord damage may produce paraparesis or paraplegia.

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Aortic dissection

• LABORATORY FINDINGS
• Chest roentgenography The most common
  abnormality seen on chest roentgenogram in aortic
  dissection is a widening of the aortic
  silhouette, appearing in 81 to 90 per cent of
  cases and sometimes with a localized bulge
  overlying the site of origin.
• Less often, nonspecific widening of the superior
  mediastinum is seen.
• If calcification of the aortic knob is present,
  separation of the intimal calcification from the
  outer aortic soft tissue border by more than 1.0
  cm the "calcium sign" is suggestive, although
  not diagnostic, of aortic dissection

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Aortic dissection

• Diagnostic Techniques
• AORTOGRAPHY
• The diagnosis of aortic dissection is based on
• direct angiographic signs, including
  visualization of two lumens or an intimal flap
  (considered diagnostic),
• or indirect signs (considered suggestive), such
  as deformity of the aortic lumen, thickening of
  the aortic walls, branch vessel abnormalities,
  and aortic regurgitation.
• However, the recent introduction of alternative
  diagnostic modalities has indicated that
  aortography is not as sensitive as previously
  thought.

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Aortic dissection

• COMPUTED TOMOGRAPHY.
• In contrast-enhanced CT scanning, aortic
  dissection is diagnosed by the presence of two
  distinct aortic lumens, either visibly separated
  by an intimal flap or distinguished by a
  differential rate of contrast opacification.
• Recent advances, such as ultrafast CT scanning
  with an electron beam, which provides superior
  image resolution,
• Hlical CT scanning, which permits a
  three-dimensional display of the aorta and its
  branches, will likely improve the accuracy of CT
  in diagnosing aortic dissection as well as in
  better defining anatomical features.
• CT scanning has the advantage that, unlike
  aortography, it is noninvasive. However, it does
  require the use of an intravenous contrast agent.
  
• Moreover, an intimal flap is identified in only
  two-thirds of cases, and the site of intimal tear
  is rarely identified.

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Aortic dissection

• MAGNETIC RESONANCE IMAGING.
• The use of MRI has particular appeal for
  diagnosing aortic dissection in that it is
  entirely noninvasive and does not require the use
  of intravenous contrast material or ionizing
  radiation.
• MRI produces high-quality images in the
  transverse, sagittal, and coronal planes, as well
  as in a left anterior oblique view that displays
  the entire thoracic aorta in one plane
• MRI had a sensitivity of 88 per cent for
  identifying the site of intimal tear, 98 per cent
  for the presence of thrombus, and 100 per cent
  for the presence of a pericardial effusion.
• Furthermore, the use of the cine-MRI technique in
  a subset of these patients showed an 85 per cent
  sensitivity for detecting aortic regurgitation.

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Aortic dissection

• ECHOCARDIOGRAPHY.
• Nninvasive and quick to perform, and the full
  examination can be completed at the bedside.
• The echocardiographic finding considered
  diagnostic of an aortic dissection is the
  presence of an undulating intimal flap within the
  aortic lumen separating true and false channels.
• Transthoracic Echocardiography.
• This technique has a sensitivity of 59 to 85 per
  cent and specificity of 63 to 96 per cent for the
  diagnosis of aortic dissection.
• Its sensitivity is as high as 78 to 100 per cent
  for dissections involving the ascending aorta but
  drops to only 31 to 55 per cent for dissections
  of the descending aorta.
• Furthermore, image quality is often adversely
  affected by obesity, emphysema, mechanical
  ventilation, or small intercostal spaces.

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Aortic dissection

• Transesophageal Echocardiography.
• Which provides better anatomical detail.
• The procedure is relatively noninvasive and
  requires no intravenous contrast or ionizing
  radiation.
• Relative contraindications include known
  esophageal disease (strictures, tumors, and
  varices), and the required esophageal intubation
  may not be tolerated in up to 3 per cent of
  patients.
• The incidence of important side effects (such as
  hypertension, bradycardia, bronchospasm, or,
  rarely, esophageal perforation) is much less than
  1 per cent.

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Management

• BLOOD PRESSURE REDUCTION
• Initial therapeutic goals include the elimination
  of pain and the reduction of systolic blood
  pressure to 100 to 120 mm Hg (mean 60 to 75 mm
  Hg),
• Or to the lowest level commensurate with adequate
  vital organ (cardiac, cerebral, renal) perfusion.

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Aortic dissection

• MANAGEMENT OF CARDIAC TAMPONADE.
• Pricardiocentesis is commonly performed in this
  setting in an effort to stabilize patients while
  they await definitive surgical repair.
• However, in a retrospective series we found that
  pericardiocentesis may be harmful rather than
  beneficial in this setting, as it may precipitate
  hemodynamic collapse and death rather than
  stabilize the patient as intended.
• Therefore, when a patient with acute aortic
  dissection complicated by cardiac tamponade is
  relatively stable, the risks of
  pericardiocentesis likely outweigh the benefits
  and every effort should be made to proceed as
  urgently as possible to the operating room for
  direct surgical repair of the aorta with
  intraoperative drainage of the hemopericardium.
• However, when patients present with
  electromechanical dissociation or marked
  hypotension, an attempt to resuscitate the
  patient with pericardiocentesis is warranted.
• A prudent strategy in such cases might be to
  aspirate only enough pericardial fluid to raise
  blood pressure to the lowest acceptable level.

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Aortic dissection

• Definitive Therapy
• SURGICAL MANAGEMENT
• 1.Treatment of choice for acute proximal
  dissection
• 2.Treatment of acute distal dissection
  complicated by the following
• a. Progression with vital organ
  compromise
• b. Rupture or impending rupture (e.g.,
  saccular aneurysm formation)
• c. Aortic regurgitation (rare)
• d. Retrograde extension into the ascending
  aorta
• e. Dissection in the Marfan syndrome

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Aortic dissection

• DEFINITIVE MEDICAL MANAGEMENT
• 1. Treatment of choice for uncomplicated distal
  dissection
• 2.Treatment for stable, isolated arch
  dissection
• 3.Treatment of choice for stable chronic
  dissection (uncomplicated dissection presenting 2
  weeks or later after onset)

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Thank You