Basics
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
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 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
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 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 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
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 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
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:
- 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
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)