Nontraumatic thoracic aortic dissection

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Not to be confused with traumatic aortic transection

Background

  • Most commonly seen in men 60-80 yrs old
  • Intimal tear with blood leaking into media
  • Mortality increases 1% per hour of symptoms when untreated
  • Diagnosis delayed > 24hr in 50% of cases
  • Bimodal age distribution
    • Young with risk factors
    • Elderly males with chronic hypertension
    • Atherosclerotic risk factors (smoking, hypertension, HLD, DM)

Classification (Stanford)

  • Type A - Involves any portion of ascending aorta
    • Requires surgery
  • Type B - Isolated to descending aorta
    • Primarily medical management with surgery consultation
Classification of aortic dissection
AoDissect DeBakey1.png AoDissect DeBakey2.png AoDissect DeBakey3.png
Percentage 60% 10–15% 25–30%
Type DeBakey I DeBakey II DeBakey III
Stanford A (Proximal) Stanford B (Distal)

Clinical Features

General

  • Symptoms
    • Tearing/ripping pain (10.8x increased disease probability)
    • Migrating pain (7.6x)
    • Sudden chest pain (2.6x)
    • History of hypertension (1.5x)
  • Signs
    • Focal neurologic deficit (33x)
    • Diastolic heart murmur (acute aortic regurg) (4.9x)
    • Pulse deficit (2.7x)
    • Hypertension at time of presentation (49% of all cases[1])
  • Studies
    • Enlarged aorta or widened mediastinum (3.4x)
    • LVH on admission ECG (3.2x)

Specific

  • Ascending Aorta
    • Acute aortic regurgitation, leading to a diastolic decrescendo murmur, hypotension, or heart failure, in 50%-66%
    • MI/Ischemia on ECG, usually inferior
    • Cardiac Tamponade
    • Hemothorax - if adventitia disruption
    • Horners, partial - sympathetic ganglion
    • Voice hoarseness - recurrent laryngeal n. compression
    • CVA/Syncope - if carotid extension
    • Neurological deficits
    • SBP>20mmhg difference between arms
    • Hypertension at time of presentation (35.7% of all cases[1])
  • Descending Aorta
    • Chest pain, back pain, abdominal pain
      • Chest Pain - Abrupt, severe (90% of patients) radiating to back
    • Hypertension at time of presentation (70.1% of all cases[1])
    • Hemiplegia, neuropathy (15%)
    • Renal failure
    • Distal Pulse deficits/ limb ischemia
    • Mesenteric ischemia

Differential Diagnosis

Chest pain

Critical

Emergent

Nonemergent

Hypertension

Evaluation

Acute Aortic Dissection (AAD) Risk Score

A score 1 should be awarded for each of the 3 categories that contain at least one of the listed features

Predisposing conditions Pain features Physical findings
  • Marfan syndrome
  • Connective tissue disease
  • Family history of aortic disease
  • Recent aortic manipulation
  • Known thoracic aortic aneurysm

Chest, back, or abdominal pain described as:

  • Abrupt in onset/severe in intensity

AND

  • Ripping/tearing/sharp or stabbing quality
  • Evidence of perfusion deficit
    • Pulse deficit
    • Systolic BP differential
    • Focal neuological deficit (in conjunction with pain)
  • Murmur of aortic insufficiency (new or not known to be old and in conjunction with pain)
  • Hypotensionof shock state
Score Category Prevalence
0 Low 6%
1 Intermediate 27%
>1 High 39%

No Risk Factor Screening

  • CXR
    • Abnormal in 90%
    • Mediastinal widening (seen in 56-63%)
    • Left sided pleural effusion (seen in 19%)
    • Widening of aortic contour (seen in 48%), displaced calcification (6mm), aortic kinking, double density sign
CXR showing widened mediastinum and porminent aortic knob

Low AAD risk Rule-Out[2]

  • D-dimer
    • May use for ADD score = 0 (post test probability <0.3%)
    • Sn 0.97 and Sp 0.56 (NPV 0.96)[3]
    • ACEP considers D-dimer as Level C[4]

High Risk/Definitive

  • CT aortogram chest
    • Study of choice
    • Similar sensitivity/specificity to TEE and MRA
CT chest with contrast of thoracic aortic dissection.

Other Findings

  • ECG
    • Ischemia (esp inferior) - 15%
    • Nonspec ST-T changes - 40%
  • Bedside US
    • Can help in ruling in patients when AOFT is >4cm
    • Rule out pericardial effusion and tamponade
    • TEE has a sensitivity of 98% and 95% specific[5]

Management

Lower wall tension by lowering BP (La Place T = P × r)

Control heart rate before blood pressure (Goal to keep HR 60-80 and SBP 100-120)
  • Important considerations
    • Right radial arterial line or right arm blood pressure will be the most accurate
    • Beta blockers are good first-line options, since they reduce heart rate and aortic wall tension
    • However, avoid beta blockers in aortic regurgitation murmurs or on bedside echo
    • Do not start nitroprusside until tachycardia resolves to avoid reflexive tachycardia
  1. Heart rate control (beta-blockers are first line)
    • Esmolol
      • Advantage of short half life, easily titratable
      • Bolus 0.1-0.5mg/kg over 1min; infuse 0.025-0.2mg/kg/min
      • Esmolol Drip Sheet
    • Labetalol - has both α and beta effects
      • Push dose - 10-20mg with repeat doses of 20-40mg q10min up to 300mg
      • Drip - Load 15-20mg IV, followed by 5mg/hr
    • Metoprolol
      • 5mg IV x 3; infuse at 2-5mg/hr
    • Diltiazem - Use if contraindications to beta-blockers
      • Loading 0.25mg/kg over 2–5 min, followed by a drip of 5mg/h
  2. Blood pressure control (vasodialators)
    • Only use if beta-blocker is ineffective
    • Do not use without a beta-blocker (must suppress reflex tachycardia - shear forces from increased HR)
    • Nicardipine/Clevidipine - consider following regimen for nicardipine:
      • 5mg/hr start, then titrate up by 2.5mg/hr every 10 min until goal
      • Once at goal, drop to 3mg/hr and re-titrate from there
      • May initially bolus 2mg IV[6]
    • Nitroprusside 0.3-0.5mcg/kg/min - Risk of cerebral blood vessel vasodilation and CN/Thiocynate toxicity
    • Fenoldopam
    • Enalapril
  3. Analgesia

Disposition

  • Admission to OR or ICU

Complications

  • AV Regurgitation/Insufficiency
    • CHF with diastolic murmur
  • Rupture
    • Pericardium: tamponade
    • Mediastinum: hemothorax
  • Vascular obstruction
    • Coronary: ACS
    • Carotid: CVA
    • Lumbar: Paraplegia

See Also

External Links

References

  1. 1.0 1.1 1.2 Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA. 2000; 283(7):897-903.
  2. Asha SE et al. "A systematic review and meta-analysis of D-dimer as a rule out test for suspected acute aortic dissection." Annals of EM. 66;4;368-377Ocotber 2015.
  3. Shimony A, et al. Meta-analysis of usefulness of d-dimer to diagnose acute aortic dissection. Am J Cardiol. 2011; 107(8):1227-1234.
  4. Diercks DB, et al. Clinical policy: Critical issues in the evaluation and management of adult patients with suspected acute nontraumatic thoracic aortic dissection. Ann Emerg Med. 2015; 65(1):32-42e12.
  5. Shiga T, Wajima Z, Apfel CC, Inoue T, Ohe Y. Diagnostic accuracy of transesophageal echocardiography, helical computed tomography, and magnetic resonance imaging for suspected thoracic aortic dissection: systematic review and meta-analysis. Arch Intern Med. 2006 Jul 10;166(13):1350-6.
  6. Curran MP et al. Intravenous Nicardipine. Drugs 2006; 66(13): 1755-1782. http://emcrit.org/wp-content/uploads/2014/07/bolus-dose-nicardipine.pdf