Can you defibrillate a heart in cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia?

Defibrillation in Cardiac Arrest

Yes, defibrillation is specifically indicated for a heart in cardiac arrest due to ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), not for a completely stopped heart (asystole). 1

Understanding Shockable vs. Non-Shockable Rhythms

Defibrillation works by delivering an electrical shock to terminate chaotic electrical activity in the heart (VF/pVT) and allow normal electrical conduction to resume. It's important to understand which cardiac arrest rhythms are appropriate for defibrillation:

Shockable Rhythms (Defibrillation Indicated):

• Ventricular fibrillation (VF)
• Pulseless ventricular tachycardia (pVT)

Non-Shockable Rhythms (Defibrillation NOT Indicated):

• Asystole (flatline)
• Pulseless electrical activity (PEA)

Timing of Defibrillation

Early defibrillation is critical for survival in VF/pVT cardiac arrest:

• For witnessed cardiac arrest with VF/pVT, defibrillation should be performed as soon as possible 1
• Survival rates decline 7-10% with every minute defibrillation is delayed 1
• When defibrillation occurs within the first minute of collapse, survival rates as high as 90% have been reported 1, 2
• Delayed defibrillation (>2 minutes) is associated with significantly lower survival rates (22.2% vs. 39.3% when not delayed) 3

Proper Defibrillation Protocol for VF/pVT

1. Recognition: Identify cardiac arrest and determine if rhythm is VF/pVT
2. Immediate Action: Apply defibrillator pads in anterolateral or anteroposterior position 4
3. Energy Settings:
   • For biphasic defibrillators (recommended): Follow manufacturer recommendations (typically 120-200J)
   • For monophasic defibrillators: 360J 1
4. Shock Sequence:
   • Deliver first shock
   • Immediately resume high-quality CPR after shock delivery
   • Minimize pre-shock and peri-shock pauses to maximize chest compression fraction 4
   • Continue CPR for 2 minutes before reassessing rhythm

Common Pitfalls to Avoid

1. Misidentifying rhythms: Always confirm "asystole" in at least two ECG leads, as fine VF can sometimes appear as asystole in a single lead 1

2. Excessive interruptions in CPR: Charge the defibrillator during chest compressions and resume compressions immediately after shock delivery 4

3. Delayed defibrillation: For witnessed VF/pVT arrest, defibrillate as soon as possible rather than performing CPR first 5, 6

4. Failing to consider vector change: If initial defibrillation attempts are unsuccessful, consider changing pad placement 4

5. Overlooking refractory VF: For shock-resistant VF/pVT, consider antiarrhythmic medications (amiodarone or lidocaine) and possibly dual sequential defibrillation after 3 or more unsuccessful shocks 1, 4

Special Considerations

For shock-refractory VF/pVT (persisting after ≥1 shocks):

• Antiarrhythmic drugs may facilitate successful defibrillation
• Either amiodarone or lidocaine may be considered 1
• Continue high-quality CPR and consider reversible causes (Hs and Ts)

Remember that the primary goal in cardiac arrest is to maintain high-quality CPR with minimal interruptions while providing early defibrillation for shockable rhythms. This approach maximizes the chance of survival with good neurological outcomes.