Aortic Dissection for the Nurse Practitioner Licensing Exam
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Overview of Aortic Dissection
- Definition: Aortic dissection occurs when a tear forms in the inner layer (intima) of the aorta, allowing blood to flow between the layers of the aortic wall, creating a false lumen.
- Types:
- Stanford Type A: Involves the ascending aorta, may extend into the descending aorta.
- Stanford Type B: Involves only the descending aorta, distal to the left subclavian artery.
- Pathogenesis: Blood enters the intimal tear, separating the layers of the aortic wall, which can compromise blood flow to organs and increase the risk of rupture.
- Risk Factors:
- Hypertension (most common)
- Connective tissue disorders (e.g., Marfan syndrome, Ehlers-Danlos syndrome)
- Atherosclerosis
- Bicuspid aortic valve
- Cocaine use
- Trauma or previous cardiac surgery
- Pregnancy (rare, but important risk factor)
Clinical Presentation
- Sudden onset of severe chest or back pain: Described as "tearing" or "ripping"; pain location varies (anterior chest pain for Type A, back pain for Type B).
- Hypertension: Common in Type B dissections; hypotension in Type A suggests rupture or tamponade.
- Pulse deficits: May show differences in blood pressure or pulse between limbs.
- Aortic regurgitation: New murmur, particularly in Type A dissection.
- Neurological deficits: Stroke, syncope, or paraplegia from impaired blood flow.
Diagnosis
- Imaging:
- CT angiography: Gold standard for diagnosing and determining the extent of dissection.
- Transesophageal echocardiography (TEE): Preferred for unstable patients or bedside evaluation.
- MRI: Useful for non-emergent, detailed evaluation, but less practical in acute cases.
- Chest X-ray: May show widened mediastinum, though not diagnostic.
- ECG: Often normal but may show ischemic changes if coronary arteries are involved.
Management
- Initial stabilization:
- Aggressive blood pressure control: IV beta-blockers (e.g., labetalol, esmolol) to reduce shear stress on the aortic wall.
- Pain management: Morphine is commonly used.
- Surgical intervention:
- Type A dissections: Emergency surgery required to prevent fatal complications like rupture or tamponade.
- Type B dissections: Typically managed with blood pressure control unless there are complications (e.g., organ malperfusion or rupture), in which case surgery or endovascular repair (TEVAR) may be necessary.
Postoperative and Long-Term Care
- Lifelong blood pressure control: Critical to prevent further dissection or recurrence.
- Surveillance imaging: Regular follow-up with CT or MRI to monitor for progression or complications.
- Genetic counseling: Important for patients with connective tissue disorders like Marfan syndrome.
Essential Points
- Type A dissections require immediate surgical intervention to prevent life-threatening complications.
- Type B dissections are usually managed medically, but complications may require surgical intervention.
- Hypertension control is critical for both acute management and long-term prevention of further dissection.
- CT angiography and TEE are key diagnostic tools, with CT preferred for stable patients and TEE for unstable patients.
- Lifelong surveillance is essential, especially for patients with genetic predispositions like Marfan syndrome.