What is the best approach to diagnose and initially manage an aortic dissection?

Diagnosing Aortic Dissection: A Comprehensive Approach

CT angiography is the preferred first-line imaging modality for diagnosing aortic dissection due to its high sensitivity (>95%), wide availability, and ability to rapidly assess the entire aorta. 1, 2

Initial Clinical Assessment

Key Physical Examination Findings

• Blood pressure measurement in both arms (differential >20 mmHg is highly suggestive of dissection) 2
• Systematic pulse examination to detect deficits or asymmetry (present in up to 20% of proximal dissections) 2
• Cardiac auscultation for diastolic murmur of aortic regurgitation (present in ~50% of patients) 2
• Focused neurological examination for altered consciousness or focal deficits 2

High-Risk Features (ADD Risk Score)

• High-risk pain characteristics: sudden, severe, tearing/ripping chest or back pain
• High-risk examination features: pulse deficits, BP differential between limbs, focal neurological deficits
• High-risk conditions: Marfan syndrome, family history of aortic disease, known aortic valve disease

Diagnostic Imaging Algorithm

1. First-Line Imaging

• CT Angiography (CTA)
  • Sensitivity: >95%, Specificity: >95% 1
  • Advantages: Widely available, rapid acquisition, excellent visualization of entire aorta
  • Key diagnostic finding: Visualization of an intimal flap separating true and false lumens 1
  • Secondary findings: Internal displacement of intimal calcifications, delayed enhancement of false lumen, aortic widening 1

2. Alternative First-Line Options (if CTA unavailable or contraindicated)

• Transesophageal Echocardiography (TEE)

  • Sensitivity: 99%, Specificity: 89% 1
  • Advantages: Can be performed bedside in unstable patients, no radiation or contrast
  • Limitations: "Blind spot" in distal ascending aorta and anterior arch, operator-dependent 1

• MRI

  • Sensitivity and specificity approaching 100% 1
  • Advantages: No radiation, excellent tissue characterization
  • Limitations: Limited availability in emergency settings, longer acquisition time, contraindicated with certain implants

3. Bedside Assessment in Unstable Patients

• Transthoracic Echocardiography (TTE)
  • Sensitivity: 59-80% for ascending aorta, only 70% for descending aorta 1, 2
  • Use when patient too unstable for transport
  • Can rapidly identify complications (tamponade, severe AR)

Diagnostic Pitfalls to Avoid

1. Relying solely on TTE in stable patients

   • Limited sensitivity, especially for descending aorta 1
   • Should be followed by definitive imaging

2. Misinterpreting artifacts on imaging

   • Reverberation artifacts within ascending aorta on TEE 1
   • Venous streaks and aortic motion artifacts on CT 1
   • Mural thrombi in aneurysms can be mistaken for dissection 1

3. Missing limited dissections

   • Small circumscript dissections in the "blind spot" of TEE 1
   • Non-communicating dissections may be subtle 3, 4
   • Consider cardiac-gated CT for suspected aortic root dissections 3

4. Failing to recognize atypical presentations

   • Less than 50% present with classic triad (sudden chest pain, pulse deficits, widened mediastinum) 2
   • Consider in patients with unexplained syncope, stroke, or limb ischemia

Initial Management While Awaiting Definitive Diagnosis

1. Hemodynamic Stabilization

   • Establish IV access (preferably two lines) 2
   • Begin continuous ECG and blood pressure monitoring 2

2. Blood Pressure Control

   • First-line: IV beta-blockers (esmolol, propranolol, metoprolol, labetalol) 2
   • Target: Heart rate <60 bpm, systolic BP 100-120 mmHg 2
   • Add sodium nitroprusside if beta-blockers alone insufficient 2

3. Pain Management

   • Morphine sulfate IV (titrate to pain relief) 2

4. Important Cautions

   • Withhold antithrombotic therapy 2
   • Avoid vasodilators without prior beta-blockade 2
   • Pericardiocentesis may be harmful in cardiac tamponade due to dissection 1

Special Considerations

• In hemodynamically unstable patients, TEE can be performed as the sole diagnostic procedure in the ICU or operating theater 1
• Transfer patients with high probability of aortic dissection directly to centers with 24/7 aortic imaging and cardiac surgery capability 2
• Consider serial imaging if initial tests are negative but clinical suspicion remains high 4

Remember that missed diagnoses of aortic dissection are associated with high mortality, so maintain a low threshold for advanced imaging when clinical suspicion exists.