DESCRIPTION

• Aortic dissection begins when there is an intimal tear.
• Blood then dissects through the media under aortic systolic pressure.
• It is thought that hypertension is a major factor in the dissection process.
• Dissections can start proximally at the root and dissect distally to involve any or all branches of the aorta, such as the carotid and subclavian arteries.
• The dissection process can also proceed proximally to involve the aortic root, the coronary ostia, and the pericardium.
• Dissection that progresses proximally may lead to occlusion of the coronary ostia, aortic valve incompetence, or cardiac tamponade.
• Classification related to portion of aorta involved:
  • Stanford classification:
    • Type A: Ascending aorta
    • Type B: Distal to ascending aorta
  • DeBakey classification:
    • DeBakey I: Intimal tear in aortic arch or root
    • DeBakey II: Ascending aorta
    • DeBakey III: Distal to takeoff of left subclavian artery
• Peak age for occurrence:
  • Proximal dissection: 50–55 yr
  • Distal dissection: 60–70 yr

Pregnancy Considerations

Risk of dissection increases in the presence of pregnancy:

• In women < 40 yr of age, 50% of dissections occur during pregnancy.

ETIOLOGY

Any process that affects the mechanical properties of the aortic wall can lead to dissection:

• Hypertension (72% of patients in the Registry of Acute Aortic Dissection)
• Congenital heart disease (bicuspid aortic valve, coarctation)
• Aortic wall connective tissue abnormalities (cystic medial necrosis)
• Connective tissue disease (Marfan disease, Ehlers–Danlos syndrome)
• Pregnancy
• Infectious/inflammatory conditions that can cause vasculitis (lupus, syphilis, endocarditis, giant cell arteritis, rheumatoid arthritis, Takayasu arteritis)
• Previous cardiac surgery including CABG, aortic valve repair
• Tobacco use

[Outline]

• DESCRIPTION
• ETIOLOGY

SIGNS AND SYMPTOMS

History

• Chest pain:
  • May be absent in as many as 15% of patients
  • Substernal if type A dissection
  • Intrascapular if descending thoracic dissection
  • Lumbar if abdominal aorta involved
  • Starts abruptly
  • Usually described as sharp
  • Most severe at onset
• Back pain:
  • Commonly interscapular or lumbar
• Combination of chest, back, and abdominal pain
• Neurologic complaints:
  • Visual changes
  • Stroke symptoms
• Aortic dissection may present with atypical symptoms that can result in a delay of diagnosis
  • Abdominal pain
  • Chest pressure
  • Leg pain
  • Syncope
  • Fever
  • Nausea, vomiting

Geriatric Considerations

Elderly are less likely to undergo surgery and have a higher mortality rate

• Elderly are less likely to describe their pain as abrupt in onset, have a pulse deficit, or have aortic insufficiency

Physical Exam

• HTN:
  • 35–40% may be normotensive.
• Pulse deficits:
  • Discrepancies in BP between limbs
  • Usually in upper extremities
• Neurologic/spinal cord deficits
• Murmur of aortic regurgitation:
  • Occurs in up to 31% of patients
  • Musical, vibrating quality with variable intensity
  • Heard best along right sternal border
• Shock
  • If pericardial rupture or myocardial infarction (MI) from dissection into a coronary artery
• Atypical presentations
  • Ischemic lower extremity
  • Altered mental status
  • Congestive heart failure

ESSENTIAL WORKUP

ECG:

• Useful in ruling in or out ST-elevation MI or ischemia
• Dissection may involve coronary ostia and cause MI:
  • Inferior MI (right coronary artery lesion) is more common than left coronary artery territory.
• Useful for evaluating the presence of left ventricular hypertrophy
• A normal ECG in the presence of severe, acute-onset chest/back pain should heighten one's suspicion of an aortic dissection.

DIAGNOSIS TESTS & INTERPRETATION

Lab

• Leukocytosis
• Hematuria
• Elevated BUN and creatinine
• Elevated amylase secondary to bowel ischemia
• Elevated cardiac enzymes due to myocardial ischemia
• D-dimer < 500 ng/mL makes the diagnosis of dissection unlikely

Imaging

• CXR:
  • Useful in excluding other etiologies such as pneumothorax and pneumonia
  • In dissection, there may be a widened mediastinum or abnormal aortic contour.
  • An enlarged heart secondary to pericardial fluid (blood) may be present.
  • May be completely normal in as many as 12–18% of cases
• Echo—transthoracic or transesophageal:
  • Transthoracic:
    • Not very helpful in the diagnosis of aortic dissection
    • May be used to evaluate for complications of a known dissection such as tamponade, valvular incompetence, or MI (from ostial occlusion)
  • Transesophageal:
    • May be performed in the ED
    • Patients may require intubation.
    • Provides information regarding extent of dissection and complications
• CT:
  • Very useful in defining extent of dissection
  • May also be used in diagnosing clinical entities such as pulmonary embolism
  • Has a high sensitivity for the diagnosis of aortic dissection and is the diagnostic modality of choice in many centers
• MRI:
  • Highly sensitive and specific
  • Requires patient transport out of ED for extended period of time
  • Lack of immediate availability may be a problem
  • Study of choice in those with renal insufficiency or dye allergy
• Aortography:
  • High sensitivity and specificity
  • Useful for preoperative planning
  • Difficult to obtain in many centers
• Cardiac catheterization:
  • Due of overlap of symptomatology with cardiac ischemia, some patients may have diagnosis made by cardiac catheterization when an intimal flap is visualized.

DIFFERENTIAL DIAGNOSIS

• MI/ischemia
• Unstable angina
• Pneumothorax
• Esophageal rupture
• Pulmonary embolism
• Pericarditis
• Pneumonia
• Musculoskeletal pain

[Outline]

• SIGNS AND SYMPTOMS
• ESSENTIAL WORKUP
• DIAGNOSIS TESTS & INTERPRETATION
• DIFFERENTIAL DIAGNOSIS

PRE-HOSPITAL

• Monitor
• IV access
• Oxygen

INITIAL STABILIZATION/THERAPY

• 2 large-bore IV lines
• Continuous cardiac monitoring
• Pulse oximetry
• Oxygen
• Type and cross

ED TREATMENT/PROCEDURES

• BP reduction to reduce shearing forces on aortic wall and slow down the dissection process
• Medications: IV β-blockade and nitroprusside
  • Medications are used to control HTN and cardiac contractility and decrease shearing forces.
  • Esmolol (IV) or labetalol (IV):
    • Contraindications: Bradycardia, COPD, hypotension
  • Nitroprusside (commonly used in conjunction with IV β-blocker)
  • Caution when using the above together: To prevent an initial increase in shear forces, β-blocker therapy should be started prior to the addition of nitroprusside therapy
• Emergent surgery:
  • Treatment of choice for type A dissection
  • Treatment for type B dissections in those who have failed medical therapy
• Medical management:
  • Treatment of choice for stable type B dissections

ALERT

MEDICATION

• Esmolol: 500 µg/kg IV bolus, then 25–50 µg/kg/min drip
• Labetalol: 10–20 mg IV over 2 min q10–15min. Then 2–4 mg/min IV drip. Total dose not to exceed 300 mg.
• Nitroprusside: 0.5 µk/kg/min IV and titrate upward to desired effect. Dose should be based on IBW.

[Outline]

• PRE-HOSPITAL
• INITIAL STABILIZATION/THERAPY
• ED TREATMENT/PROCEDURES
• MEDICATION

DISPOSITION

Admission Criteria

• All patients with acute aortic dissection should be admitted to the intensive care unit.
• Emergency cardiothoracic surgery consultation should be obtained, especially in cases of type A dissection.

Discharge Criteria

None

FOLLOW-UP RECOMMENDATIONS

Close follow-up with cardiology and/or cardiothoracic surgery is of paramount importance.

[Outline]

• DISPOSITION
• FOLLOW-UP RECOMMENDATIONS

• Untreated, nearly 75% of patients with ascending aortic dissection can be expected to die within 2 wk, with a mortality of 1–3%/hr in the 1st 48 hr.
• Majority of patients present with pain (90%) of severe intensity (90%) that occurred suddenly (84%).
• Although some recent literature has suggested a role for D-dimer testing, there is insufficient evidence to support its use as the sole screening test for aortic dissection.
• Should consider the diagnosis in patients with chest pain in whom conventional therapy (nitrates, β-blockers) are ineffective, and in those who have chest pain in addition to another complaint (extremity weakness, back pain, paresthesias, abdominal pain).
• Identification of risk factors is critical. These include:
  • HTN
  • Male gender
  • Cocaine use
  • Advanced age
  • Pregnancy
  • Connective tissue disorders, such as Marfan syndrome or cystic medial necrosis
  • Bicuspid aortic valve
  • Turner syndrome
  • Family history
  • Previous cardiac or valvular surgery

ICD9

441.01 Dissection of aorta, thoracic

ICD10

I71.01 Dissection of thoracic aorta

[Outline]

• ICD9
• ICD10

• Harris KM, Strauss CE, Eagle KA, et al. Correlates of delayed recognition and treatment of acute type A aortic dissection: The International Registry of Acute Aortic Dissection (IRAD). Circulation. 2011;124:1911–1918.
• Khan IA, Nair CK. Clinical, diagnostic, and management perspectives of aortic dissection. Chest. 2002;122(1):311–328.
• Klompas M. Does this patient have an acute thoracic aortic dissection? JAMA. 2002;287:2262–2272.
• Sutherland A, Escano J, Coon TP. D-dimer as the sole screening test for acute aortic dissection: a review of the literature. Ann Emerg Med. 2008;52(4):339–343.
• Suzuki T, Distante A, Zizza A, et al. Diagnosis of acute aortic dissection by D-dimer: The International Registry of Acute Aortic Dissection Substudy on Biomarkers (IRAD-Bio) experience. Circulation. 2009;119:2702–2707.

Jeffrey I. Schneider

Jonathan S. Olshaker