What clinical assessments are useful for pre-hospital providers to diagnose dissecting Abdominal Aortic Aneurysm (AAA) or Thoracic Aortic Aneurysm (TAA)?

Clinical Assessment of Dissecting AAA or TAA in the Pre-Hospital Setting

Use the Aortic Dissection Detection (ADD) score as your primary clinical assessment tool in the pre-hospital setting, as it is highly recommended by the European Society of Cardiology for identifying high-risk patients (ADD score ≥1 has 91% sensitivity). 1

Primary Clinical Assessment Tool: ADD Score

The ADD score is the cornerstone of pre-hospital assessment and should be calculated immediately for any patient with suspected aortic pathology 1:

• Patients with ADD score ≥1 are considered high-risk and should be treated as having aortic dissection until proven otherwise 1
• Patients with ADD score of 0 have low probability of aortic dissection 1
• The score evaluates three categories of clinical features, with 1 point awarded for presence of characteristics in any category 1

Key Clinical Presentations to Assess

Pain Characteristics

• Chest pain is the most common presentation, but aortic dissection must be considered in patients with abdominal pain, back pain, or any combination of these 1
• The pain pattern and location help differentiate between thoracic (chest/back) and abdominal involvement 1

Cardiovascular Signs

• Unexplained hypotension is a critical red flag requiring immediate suspicion of dissection 1
• Pulse deficits or blood pressure differentials between extremities suggest dissection with branch vessel involvement 2
• Age >70 years combined with systolic blood pressure <137 mmHg significantly increases likelihood of acute aortic pathology (likelihood ratio 2.6) 2

Neurological Manifestations

• Syncope is an important presenting symptom that should trigger consideration of aortic dissection 1
• Focal neurological deficits may indicate cerebral or spinal cord malperfusion 1

Additional High-Risk Features

• Presence of diaphoresis increases likelihood of acute AAA (likelihood ratio 2.5) 2
• Known history of AAA substantially increases risk (likelihood ratio 2.9) 2

Physical Examination Findings

Abdominal Assessment for AAA

• Palpable pulsatile abdominal mass has only 47% sensitivity but high specificity when present 3
• Physical examination is more reliable in thin patients (abdominal girth <100 cm) where it can detect most aneurysms 4
• Absence of palpable mass does NOT rule out AAA, particularly in obese patients 3, 4

Cardiovascular Examination

• Assess for bilateral femoral pulses - diminished or absent pulses suggest iliac artery involvement 2
• Check for blood pressure differentials between arms (>20 mmHg difference suggests dissection)
• Evaluate for signs of hemodynamic instability including tachycardia and hypotension 1

Adjunctive Pre-Hospital Tools

ECG Assessment

• Perform 12-lead ECG on all patients with chest pain to rule out myocardial infarction 1
• ECG is usually normal in aortic dissection, which helps differentiate from acute coronary syndrome 1
• Presence of ECG signs of ischemia does NOT exclude dissection and may indicate coronary artery involvement 1

Point-of-Care Ultrasound (FoCUS)

• FoCUS echocardiography may be considered to support diagnosis of aortic dissection if available and provider is trained 1
• For suspected AAA, point-of-care ultrasound has 97.8% sensitivity and 97% specificity for detecting aneurysm presence 3
• FoCUS is particularly helpful when ECG shows signs of myocardial ischemia to differentiate dissection from ACS 1

Critical Pitfalls to Avoid

Diagnostic Errors

• Only 20% of aortic dissections are suspected at initial presentation - maintain high index of suspicion 1
• Classic symptoms have poor sensitivity - absence of typical findings does not rule out dissection 3
• Do not rely on abdominal pain alone to predict visceral involvement - CT findings are more predictive 5

Management Errors

• NEVER administer antithrombotic therapy (aspirin, P2Y12 inhibitors, anticoagulants) if aortic dissection is suspected - this is mandatory 1
• Do not delay transfer while attempting extensive pre-hospital workup 1
• Avoid giving anticoagulation or thrombolytics which could be catastrophic in unrecognized dissection 1

Pre-Hospital Management Priorities

While assessment is ongoing, initiate appropriate management:

• Pain control is essential 1
• Blood pressure control targeting heart rate <60 bpm and systolic BP 100-120 mmHg (if no neurological complications) 1
• Start beta-blockers BEFORE other antihypertensives to prevent reflex tachycardia 1
• Activate receiving facility early if ADD score ≥1, requesting center with 24/7 aortic imaging and cardiac surgery 1

Risk Stratification for Transport Destination

High-risk patients (ADD score ≥1) require transfer to centers with 24/7 aortic imaging capability and cardiac surgery - this is mandatory 1. Consider pre-activating the surgical team and radiology during transport so the patient can proceed directly to imaging and then operating room if needed 1.