What are the signs of pulmonary embolism (PE) in cardiac arrest?

Signs of Pulmonary Embolism in Cardiac Arrest

Pulseless electrical activity (PEA) is the most common presenting rhythm in pulmonary embolism (PE)-related cardiac arrest, occurring in 36-53% of cases, and should strongly prompt consideration of PE as the underlying cause. 1, 2

Key Clinical Indicators of PE in Cardiac Arrest

Pre-arrest Warning Signs

• Prodromal symptoms before arrest:
  • Dyspnea or respiratory distress
  • Chest pain (often pleuritic)
  • Syncope or pre-syncope
  • Hemoptysis (less common)

Risk Factors

• Conventional thromboembolism risk factors:
  • Recent immobilization or major surgery
  • Recent lower limb trauma/surgery
  • Clinical or history of DVT
  • Previous PE
  • Pregnancy or postpartum state
  • Major medical illness

Cardiac Arrest Presentation

• Rhythm characteristics:

  • PEA as the initial rhythm (36-53% of PE-related arrests) 1, 2
  • Shockable rhythms (VF/VT) are uncommon in PE-related arrest
  • Asystole may occur in severe cases

• Hemodynamic findings (if monitored before arrest):

  • Acute right ventricular pressure increase
  • Signs of cardiogenic shock
  • Refractory hypoxemia despite oxygen therapy

Diagnostic Findings During Resuscitation

Point-of-Care Ultrasound (POCUS) Findings

• Right ventricular enlargement/dilation
• D-shaped left ventricle (interventricular septal flattening)
• Right ventricular hypokinesis with apical sparing (McConnell's sign)
• Dilated inferior vena cava without respiratory variation
• Possible visualization of thrombus in main pulmonary arteries

ECG Findings (if obtained before arrest)

• Sinus tachycardia (most common)
• S1Q3T3 pattern (S wave in lead I, Q wave in lead III, T wave inversion in lead III)
• Right bundle branch block
• T-wave inversions in V1-V4
• Right axis deviation

Management Considerations

Immediate Actions

• High-quality CPR following standard ACLS protocols
• Consider early thrombolysis if PE is strongly suspected:
  • Alteplase 50 mg IV bolus (may repeat in 15 minutes if no response) 1, 2
  • Tenecteplase single weight-based dose (alternative) 2

Advanced Options

• Surgical or percutaneous mechanical embolectomy (if available and ROSC achieved)
• ECPR (extracorporeal CPR) consideration for refractory arrest

Pitfalls and Caveats

• PE is often missed as a cause of cardiac arrest, accounting for 5-13% of unexplained arrests 1, 3
• The absence of risk factors does not exclude PE (40% of PE patients have no identifiable risk factors) 1
• Mortality is extremely high (65-90%) in PE-related cardiac arrest 1, 3
• Diagnostic confirmation should not delay treatment in highly suspicious cases
• The risk of bleeding with thrombolysis during CPR should not prevent treatment given the high mortality without intervention 2

Post-ROSC Management

• Initiate anticoagulation (typically 3 hours after thrombolysis)
• Implement standard post-cardiac arrest care
• Consider therapeutic hypothermia if patient remains comatose
• Treat hypoxemia and hypotension aggressively

PE-related cardiac arrest represents a critical clinical scenario with extremely high mortality. Early recognition of warning signs, prompt identification during arrest, and immediate consideration of thrombolysis may offer the best chance for survival in these challenging cases.