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Aortic Dissection, Thoracic, Emergency Medicine

Basics

Description

- 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

- Combination of chest, back, and abdominal pain - Neurologic complaints: - Visual changes - Stroke symptoms

- 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

- Atypical presentations - Ischemic lower extremity - Altered mental status - Congestive heart failure

- 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

- 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

  • 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 aortaType B: Distal to ascending aortaDeBakey classification:DeBakey I: Intimal tear in aortic arch or rootDeBakey II: Ascending aortaDeBakey III: Distal to takeoff of left subclavian artery
  • Peak age for occurrence:Proximal dissection: 50-55 yrDistal dissection: 60-70 yr

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

Diagnosis

Signs and Symptoms

History

  • Chest pain:May be absent in as many as 15% of patientsSubsternal if type A dissectionIntrascapular if descending thoracic dissectionLumbar if abdominal aorta involvedStarts abruptlyUsually described as sharpMost severe at onset
  • Back pain:Commonly interscapular or lumbar
  • Combination of chest, back, and abdominal pain
  • Neurologic complaints:Visual changesStroke symptoms
  • Aortic dissection may present with atypical symptoms that can result in a delay of diagnosisAbdominal painChest pressureLeg painSyncopeFeverNausea, vomiting

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 limbsUsually in upper extremities
  • Neurologic/spinal cord deficits
  • Murmur of aortic regurgitation:Occurs in up to 31% of patientsMusical, vibrating quality with variable intensityHeard best along right sternal border
  • ShockIf pericardial rupture or myocardial infarction (MI) from dissection into a coronary artery
  • Atypical presentationsIschemic lower extremityAltered mental statusCongestive 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 ones 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 pneumoniaIn 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 dissectionMay 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 EDPatients may require intubation.Provides information regarding extent of dissection and complications
  • CT:Very useful in defining extent of dissectionMay also be used in diagnosing clinical entities such as pulmonary embolismHas a high sensitivity for the diagnosis of aortic dissection and is the diagnostic modality of choice in many centers
  • MRI:Highly sensitive and specificRequires patient transport out of ED for extended period of timeLack of immediate availability may be a problemStudy of choice in those with renal insufficiency or dye allergy
  • Aortography:High sensitivity and specificityUseful for preoperative planningDifficult 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

Treatment

Pre-Hospital

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 nitroprussideMedications are used to control HTN and cardiac contractility and decrease shearing forces.Esmolol (IV) or labetalol (IV):Contraindications: Bradycardia, COPD, hypotensionNitroprusside (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 dissectionTreatment for type B dissections in those who have failed medical therapy
  • Medical management:Treatment of choice for stable type B dissections

Symptoms of aortic dissection may be similar to those of cardiac ischemia/infarction and pulmonary embolus. Treatment with thrombolytics and anticoagulants may be harmful and potentially fatal if aortic dissection is present.

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.

Follow-Up

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

Followup Recommendations

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

Pearls and Pitfalls

  • 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:HTNMale genderCocaine useAdvanced agePregnancyConnective tissue disorders, such as Marfan syndrome or cystic medial necrosisBicuspid aortic valveTurner syndromeFamily historyPrevious cardiac or valvular surgery

Additional Reading

  • 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.

Codes

ICD9

441.01 Dissection of aorta, thoracic

ICD10

I71.01 Dissection of thoracic aorta

SNOMED

  • 233994002 dissection of thoracic aorta (disorder)
  • 301899003 Proximal aortic dissection
  • 426948001 Aneurysm of descending aorta (disorder)