What is the maximum number of shocks recommended for ventricular tachycardia (VT) management?

Maximum Number of Shocks for Ventricular Tachycardia

There is no maximum limit on the number of shocks that can be delivered for ventricular tachycardia—continue defibrillation attempts as long as VT/VF persists and resuscitation efforts are ongoing. 1

Critical Distinction: Pulse Status Determines Shock Strategy

Pulseless VT (Cardiac Arrest)

• Treat identically to ventricular fibrillation with repeated unsynchronized high-energy shocks without any maximum limit 2
• Continue high-quality CPR between shocks 2
• Use initial energy of 200J (monophasic) or manufacturer's recommended dose for biphasic (typically 120-200J) 2
• For subsequent shocks, escalate energy if the defibrillator is capable of delivering higher energy doses 1
• Success rate is 85-98% at ≤200J with biphasic waveforms 2

VT With a Pulse (Hemodynamically Unstable)

• Use synchronized cardioversion starting at 100J 1, 2, 3
• If initial shock fails, increase energy in stepwise fashion for subsequent attempts 3
• No maximum number of attempts is specified—continue until rhythm converts or patient becomes pulseless 3
• Allow at least 1 minute between consecutive shocks to avoid myocardial damage 3, 4

VT With a Pulse (Hemodynamically Stable)

• Consider brief trials of antiarrhythmic medications (procainamide, amiodarone, or lidocaine) before cardioversion 1
• Immediate cardioversion generally not needed for rates under 150 bpm 1
• If cardioversion is chosen, use synchronized shocks starting at 100J 3

Energy Escalation Protocol

The 2015 International Consensus recommends escalating shock energy if initial attempts fail and the defibrillator is capable of delivering higher energy 1. This applies to:

• Refractory VF/pulseless VT that persists after initial shocks 1
• Recurrent VF (refibrillation) after initial successful termination 1

The rationale is that escalating energy may prevent refibrillation, though the optimal energy levels remain unknown 1.

Morphology-Specific Considerations

Monomorphic VT

• With pulse: 100J synchronized cardioversion 1, 3
• Pulseless: Treat as VF with unsynchronized high-energy shocks 2

Polymorphic VT

• Always treat as VF with unsynchronized high-energy shocks, even if pulse is present 2, 3
• Never use synchronized cardioversion for polymorphic VT as synchronization is usually not possible 2

Critical Pitfalls to Avoid

• Never use synchronized cardioversion for pulseless VT—this delays treatment of a cardiac arrest rhythm 2
• Never use synchronized cardioversion for VF—the device may not sense a QRS wave and may deliver no shock 2
• Do not delay defibrillation for pulseless rhythms 2
• Ensure adequate sedation for stable patients undergoing cardioversion, but never delay cardioversion in unstable patients 3, 4

Knowledge Gaps

The 2015 International Consensus acknowledges that optimal defibrillation strategies remain poorly studied, including the maximum number of shocks that should be delivered and whether refibrillation requires different energy levels 1. In the absence of definitive evidence, continue defibrillation attempts as long as the shockable rhythm persists and resuscitation is ongoing.