When is defibrillation indicated in an adult patient with potential underlying heart disease who is unresponsive, not breathing, and has no pulse?

Defibrillation Indication in Cardiac Arrest

Defibrillation is indicated immediately upon identification of ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) in an unresponsive adult patient with no pulse—this is the single most critical intervention that determines survival. 1

Primary Indication: VF/Pulseless VT

Defibrillation must be delivered without delay when the cardiac monitor shows VF or pulseless VT. 1 These are the only two rhythms for which defibrillation is indicated as a primary intervention. 1

• VF is the most common primary rhythm in sudden cardiac arrest, particularly in adults with underlying heart disease 1
• Pulseless VT is treated identically to VF with immediate unsynchronized defibrillation 1
• Over 80% of successful defibrillations occur within the first three shocks 1

Critical Timing Considerations

In the perioperative setting, defibrillation should occur within 3 minutes of arrest onset for VF/pVT. 1 The victim's survival probability decreases progressively with each minute of delay between arrest and defibrillation. 1

• Early defibrillation with concurrent high-quality CPR is the cornerstone of survival for VF/pVT 1
• For witnessed arrests with immediate collapse (such as commotio cordis), immediate defibrillation once a monitor/defibrillator is available is recommended, as modern biphasic defibrillators have >90% first-shock efficacy 2
• Delays to defibrillation are significantly associated with decreased likelihood of cardioversion to sinus rhythm 3

Non-Shockable Rhythms: When Defibrillation is NOT Indicated

If VF/VT can be positively excluded, defibrillation is not indicated as a primary intervention. 1 The non-shockable rhythms include:

• Asystole (flat line with no electrical activity) 1
• Pulseless electrical activity/electromechanical dissociation (organized electrical activity without mechanical cardiac output) 1

These rhythms have a much worse prognosis (approximately 10-15% of the survival rate compared to VF/VT) and require a different treatment pathway focused on CPR, epinephrine, and identifying reversible causes. 1

Practical Algorithm for Decision-Making

1. Confirm cardiac arrest: Unresponsive patient with no pulse and no normal breathing 1
2. Attach monitor/defibrillator immediately to assess rhythm 1
3. Rhythm assessment:
   • If VF or pulseless VT → Defibrillate immediately 1
   • If asystole or PEA → Do NOT defibrillate; continue CPR and give epinephrine 1

Common Pitfalls to Avoid

Do not delay defibrillation to establish advanced airway or IV access when VF/pVT is present. 1 The first defibrillating shock must be given without any delay. 1

Avoid monitoring through ECG leads initially, as this significantly delays time to first shock (54 seconds vs 28 seconds with paddles). 4 Use hands-free adhesive pads or defibrillator paddles for initial rhythm assessment. 4

Do not perform pulse checks between shocks if VF/VT persists on the monitor. 1 Pulse checks are only indicated if the waveform changes to one compatible with cardiac output. 1

Recognize that a "straight line" immediately after shock may represent transient electrical stunning rather than true asystole. 1 The monitor screen often shows an isoelectric line for several seconds after defibrillation due to myocardial stunning, and coordinated rhythm or return of VF/VT may supervene subsequently. 1

Refractory VF/pVT Considerations

For patients remaining in VF/pVT after ≥3 consecutive standard defibrillation attempts (refractory VF), consider double sequential external defibrillation (DSED) or vector change defibrillation as rescue strategies, though this requires availability of two defibrillators. 5 This represents approximately 20% of VF/pulseless VT cases. 5