What is the initial workup for aortic dissection?

Initial Workup for Aortic Dissection

The initial workup for suspected aortic dissection requires urgent definitive imaging with CT angiography, MRI, or transesophageal echocardiography based on institutional capabilities and immediate availability, along with simultaneous initiation of anti-impulse therapy targeting heart rate ≤60 bpm and systolic blood pressure <120 mmHg. 1, 2

Risk Assessment and Clinical Evaluation

High-Risk Features

• Sudden onset of severe, sharp, tearing/ripping chest or back pain
• Mediastinal or aortic widening on chest radiograph
• Pulse or blood pressure differentials (>20 mmHg between arms)
• History of hypertension
• Presence of aortic regurgitation, pericardial effusion, or shock 1, 2

Aortic Dissection Detection (ADD) Risk Score

• Use ADD score to stratify probability:
  • Score ≥1 indicates high probability requiring immediate advanced imaging 2
  • Components include high-risk conditions, pain features, and examination findings

Diagnostic Algorithm

Initial Testing

1. Electrocardiogram (ECG)

   • Obtain in all patients with suspected aortic dissection
   • Rule out myocardial infarction (if ST-elevation present, treat as primary cardiac event unless high risk for dissection) 1

2. Chest X-ray

   • Perform in intermediate and low-risk patients
   • Look for mediastinal widening, abnormal aortic contour, or pleural effusion
   • Important: A negative chest X-ray should NOT delay definitive aortic imaging in high-risk patients 1, 2

3. Laboratory Tests

   • D-dimer (levels <500 ng/mL make AAD unlikely)
   • Complete blood count, basic metabolic panel, coagulation profile
   • Blood type and screen (in preparation for possible surgery)
   • Note: Do not delay imaging while awaiting results if high clinical suspicion 1, 2

Definitive Imaging

• Select one based on availability and patient stability:

  1. CT Angiography

     • Sensitivity >95%, Specificity >95%
     • First choice for most patients
     • Extend imaging from thoracic inlet to pelvis for complete assessment 2, 3

  2. MRI

     • Sensitivity and specificity approaching 100%
     • Best for stable patients with contrast allergy or renal dysfunction
     • Limited by longer acquisition time and emergency availability 2

  3. Transesophageal Echocardiography (TEE)

     • Sensitivity 99%, Specificity 89%
     • Suitable for unstable patients who cannot undergo CT
     • Can be performed at bedside 1, 2

  4. Transthoracic Echocardiography (TTE)

     • Limited sensitivity (59-80%)
     • May be used as initial screening but not sufficient to rule out dissection 2

• If initial imaging is negative but clinical suspicion remains high, obtain a second imaging study 1

Immediate Management

Anti-Impulse Therapy

1. First-Line: IV Beta-Blockers

   • Target heart rate ≤60 bpm
   • Options:
     • Labetalol (preferred due to alpha and beta-blocking properties)
     • Esmolol (for patients with potential beta-blocker intolerance)
     • Metoprolol or atenolol as alternatives 1, 2, 4

2. If Beta-Blockers Contraindicated:

   • Non-dihydropyridine calcium channel blockers for rate control 1

3. Blood Pressure Control:

   • Target SBP <120 mmHg after adequate heart rate control
   • Add vasodilators (ACE inhibitors, nitrates, or dihydropyridine CCBs) if needed
   • Caution: Never initiate vasodilators before rate control (risk of reflex tachycardia) 1, 2

4. Pain Management:

   • IV morphine sulfate, titrated to effect 2

Monitoring and Supportive Care

• Establish invasive arterial line monitoring
• Continuous ECG monitoring
• Measure blood pressure in both arms
• Admit to intensive care unit 1, 2

Surgical Consultation and Disposition

• Urgent surgical consultation for all patients diagnosed with thoracic aortic dissection regardless of type 1
• Type A dissection (involving ascending aorta): Emergent surgical repair
• Type B dissection (descending aorta only): Initial medical management unless complications develop (malperfusion, progression, enlarging aneurysm, uncontrollable pain/BP) 1, 2

Common Pitfalls to Avoid

• Delaying definitive imaging in high-risk patients
• Initiating vasodilators before heart rate control
• Failing to obtain non-contrast images (essential for detecting intramural hematoma)
• Not considering branch vessel involvement
• Administering thrombolytics or anticoagulants
• Aggressive fluid administration that could increase aortic wall stress 1, 2