Aortic Dissection

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Aortic Dissection

• Matt White
• February 8, 2010
• Morning Report

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Aortic Dissection

• Background
• Epidemiology
• Clinical characteristics
• Diagnostic Modalities
• Treatment

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Aortic Dissection

• Background
• Epidemiology
• Clinical characteristics
• Diagnostic Modalities
• Treatment

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History

• First known case was King George II on October,
  25, 1760
• First successful repair by Dr. Michael DeBakey in
  1955.
• ". . . spontaneous tear of the arterial coats is
  associated with atrocious pain, with symptoms,
  indeed, in the case of the aorta of angina
  pectoris and many instances have been mistaken
  for it"
• William Osler, 1910.

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Mechanism

• Primary event is a tear in the aortic intima.
• Degeneration of aortic media, or cystic medial
  necrosis, is felt to be a prerequisite
  nontraumatic aortic dissection
• Blood passes into the aortic media through the
  tear, separating the intima from the media and
  creating a false lumen.

• 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

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Mechanism (contd)

• Propagation of the dissection can occur both
  distal and proximal to the initial tear,
• Complications of dissection
• ischemia (coronary, cerebral, spinal, or
  visceral)
• aortic regurgitation
• Pericardial effusion/cardiac tamponade

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Nomenclature

• DeBakey classification system
• Type I - Originates in ascending aorta,
  propagates at least to the aortic arch and often
  beyond it distally.
• Type II Originates in and is confined to the
  ascending aorta.
• Type III Originates in descending aorta, rarely
  extends proximally but will extend distally.
• Daily (Stanford) classification system
• Divided into 2 groups A and B depending on
  whether the ascending aorta is involved.
• A Type I and II DeBakey
• B Type III DeBakey

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Percentage 60 10-15 25-30
Type DeBakey I DeBakey II DeBakey III
Stanford A Stanford A Stanford B
Proximal Proximal Distal
Classification of aortic dissection Classification of aortic dissection Classification of aortic dissection Classification of aortic dissection
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Aortic Dissection

• Background
• Epidemiology
• Clinical characteristics
• Diagnostic Modalities
• Treatment

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Incidence

• Ranges from 2-10 per 100,000 person-years
• Evidence of dissection is found in 1-3 of all
  autopsies

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Whos affected?

• International Registry of Acute Aortic Dissection
  (IRAD)
• 65 men
• mean age 63yrs
• Women tend to present older (67 vs. 60yrs)
• Highest incidence in patients 50 to 70 years old.
  
• Male-to-female ratio 21
• Half of dissections in females before age 40
  occur during pregnancy

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Mortality

• When left untreated
• 33 of patients die within the first 24 hours
• 50 die within 48 hours
• 75 die within 2-weeks

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Aortic dissection mimickers

• Myocardial ischemia due to an acute coronary
  syndrome with or without ST segment elevation
• Pericarditis
• Pulmonary embolus
• Aortic regurgitation without dissection
• Aortic aneurysm without dissection
• Musculoskeletal pain
• Mediastinal tumors
• Pleuritis
• Cholecystitis
• Atherosclerotic or cholesterol embolism
• Peptic ulcer disease or perforating ulcer
• Acute pancreatitis

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Aortic Dissection

• Background
• Epidemiology
• Clinical characteristics
• Diagnostic Modalities
• Treatment

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Predisposing factors

• Older patients
• HTN (72 of IRAD patients)
• Younger patients
• Pre-existing aneurysm (13)
• Inflammatory disease (giant cell, takayasu, RA,
  syphilitic aortitis)
• Collagen disorders (Marfans 50 of pts lt40,
  Ehlers-Danlos, Pseudoxanthoma elasticum
• Coarctation (Turners syndrome)
• Family history (up to 19 of pts, of mutations
  identified)
• Bicuspid aortic valve
• Trauma/Iatrogenic
• Crack cocaine, (37 in largely AA, inner-city
  population study)
• mean duration from last cocaine use 12 hours.
  Mechanism may be abrupt, transient hypertension
  due to catecholamine release.

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Clinical Features

• Abrupt onset of severe, sharp or "tearing"
  posterior chest or back pain (70-90)
• Pulse deficit
• weak/absent carotid, brachial, or femoral pulse
  resulting from intimal flap or compression by
  hematoma
• HTN at initial presentation is more common in
  those with a type B dissection (70 vs 36)

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If dissection involves ascending aorta

• Acute aortic insufficiency --gt diastolic
  decrescendo murmur, hypotension, or heart failure
  (1/2 to 2/3 of pts)
• Acute MI due to coronary occlusion (1-2). RCA
  most commonly involved (L main ? sudden death)
  and, in infrequent cases, leads to complete heart
  block.
• Tamponade
• Hemothorax (if extends through adventitia)
• Stroke (if involves carotids)
• Horner syndrome (compression of superior cervical
  sympathetic ganglion) or vocal cord paralysis
  (compression of the left recurrent laryngeal
  nerve)

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Diagnosis

• 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 some combination of the
  following
• 1. Abrupt onset of thoracic or abdominal pain
  with a sharp, tearing and/or ripping character
• 2. Mediastinal and/or aortic widening on chest
  radiograph
• 3. A variation in pulse (absence of a proximal
  extremity or carotid pulse) and/or blood pressure
  (gt20 mmHg difference between the right and left
  arm)
• The incidence of dissection related to the
  presence or absence of these three
• All three absent 7
• Pain alone 31
• Presence of chest radiographic abnormalities 39
  
• Variation in pulse or blood pressure
  differential 83
• Any two out of three variables 83

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Aortic Dissection

• Background
• Epidemiology
• Clinical characteristics
• Diagnostic Modalities
• Treatment

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EKG Findings

• normal (31)
• nonspecific ST--T wave changes (30-42)
• (commonly, LVH and strain patterns associated
  with HTN)
• ischemic changes (15)
• acute MI (5)
• gt98 do not show ST elevation
• Based on 464 IRAD patients

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Labs

• D-dimer ?
• 14-center international study of 220 patients (87
  with AD, 133 controls)
• Entry criteria suspicion of AD within first
  24hrs high enough to obtain imaging
• D-dimer levels 3213 1465 and 3574 1430 for
  type A and B respectively
• Sensitivity 96.6, Specificity 46.6
• -LR 0.07, NPV gt94
• Possibility that D-dimer could be used to help
  rule-out aortic dissection

Suzuki et. al. Diagnosis of Acute Aortic
Dissection by D-Dimer. Circulation 2009 119,
2702-2707
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Imaging

• CXR
• mediastinal widening in 80-90 with type A
  dissections, while 11 patients had no
  abnormality
• Usually multiple modalities required
• 2000 IRAD review
• most patients had multiple imaging studies
  performed (mean 1.83 per patient)
• initial study CT 61, echo in 33, aortography in
  4, MRI in 2

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Imaging

• CT scan
• Fast, easily accessible
• Sensitivity low (80), no LV fxn info, unable to
  assess AI
• TTE
• Able to assess LV fxn, AI
• Low sensitivity (60-85)
• TEE
• Excellent sensitivity (99), AI, wall motion,
  bedside exam, identifies site of tear
• Need operator
• MRI
• Excellent imaging
• Not readily available, bad for critically ill
  patients

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Imaging
Summary of specialized imaging techniques Summary of specialized imaging techniques Summary of specialized imaging techniques Summary of specialized imaging techniques Summary of specialized imaging techniques
Angiography CT MRI TEE
Sensitivity Poor Average Excellent Excellent
Specificity Good Good Excellent Good
Site of tear Good Poor Excellent Good
Aortic Regurgitation Excellent Useless Excellent Excellent
Pericardial effusion Useless Poor Excellent Good
Coronaries Excellent Useless Good Average
Modified from Cigarroa JE et al. Modified from Cigarroa JE et al. Modified from Cigarroa JE et al. Modified from Cigarroa JE et al. Modified from Cigarroa JE et al.
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Aortic Dissection

• Background
• Epidemiology
• Clinical characteristics
• Diagnostic Modalities
• Treatment

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Medical management

• Untreated aortic dissection or intramural
  hematoma
• 25 die within 24hrs
• 50 by 48hrs
• Basic management
• Type A dissection ? surgery
• Type B dissection ? medical management
• Surgery -- prevents medial extension reaching the
  pericardium and producing fatal tamponade or
  worsening other complications

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Pre-OR management

• Virtually all non-shocked patients require
  medical management prior to surgery
• Aim of medical management
• reduce the absolute pressure on the damaged
  aortic media
• Reduce the rate of rise of that pressure (dP/dT).

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Medical management

• Blood pressure control
• Blood pressure control
• Blood pressure control
• Pain control

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Main goals of medical management

• Systolic BP lt 100 mmHg.
• Pain free.
• Adequate renal perfusion (urine output gt 30
  ml/hr).
• No evidence of cerebral hypoperfusion.
• Minimized shear stress (ß-blocked to lt 55/min).

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Antihypertensive choice

• Labetalol for beta blockade
• Nitroprusside if HR controlled but SBP still
  gt100mmHg

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Antihypertensive choice

• Start with ß-blockers
• use of a vasodilator in isolation will actually
  increase aortic shear stress by widening the
  pulse pressure and the dP/dT of left ventricular
  ejection.

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Which arm to measure?

• Blood pressure should be measured in the arm with
  the highest reading.

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References

• Davies, Crispin Bashir, Yaver Shively.
  Cardiovascular Emergencies. London, GBR BMJ
  Publishing Group, 2001. p151-172
• Manning, Warren. Clinical manifestations and
  diagnosis of aortic dissection. UptoDate
• Suzuki et. al. Diagnosis of Acute Aortic
  Dissection by D-Dimer. Circulation 2009 119,
  2702-2707