Author:
Jeffrey I.Schneider
Jonathan S.Olshaker
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 Prophylaxis |
Risk of dissection increases in the presence of pregnancy:- In women <40 yr of age, 50% of dissections occur during pregnancy
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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
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
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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
- 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
Diagnostic Tests & Interpretation
Lab
- Leukocytosis
- Hematuria
- Elevated BUN and creatinine
- Elevated amylase secondary to bowel ischemia
- Elevated cardiac enzymes due to myocardial ischemia
- Negative d-dimer levels are best used for ruling out dissection in patients with a low likelihood of the disease
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
Prehospital
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):
- 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 |
| 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 mcg/kg IV bolus, then 25-50 mcg/kg/min drip
- Labetalol: 10-20 mg IV over 2 min q10-15 min. Then 2-4 mg/min IV drip. Total dose not to exceed 300 mg
- Nitroprusside: 0.5 mcg/kg/min IV and titrate upward to desired effect. Dose should be based on IBW.
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
Follow-up Recommendations
Close follow-up with cardiology and /or cardiothoracic surgery is of paramount importance
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)