Synchronized Cardioversion Energy for Ventricular Tachycardia
For monomorphic ventricular tachycardia with a pulse, start with 100 joules using synchronized cardioversion with either biphasic or monophasic waveforms. 1, 2
Critical Distinction: Pulse Status Determines Approach
The presence or absence of a pulse fundamentally changes your management strategy:
- Pulseless VT: Treat identically to ventricular fibrillation with unsynchronized high-energy shocks (≥200J), not synchronized cardioversion 1
- VT with pulse: Use synchronized cardioversion starting at 100J 1, 2
This distinction is crucial because pulseless VT represents cardiac arrest requiring immediate defibrillation, whereas stable VT with a pulse allows time for proper synchronization to avoid inducing ventricular fibrillation. 1
Morphology-Based Energy Selection
Monomorphic VT (regular, uniform QRS complexes):
- Initial energy: 100J synchronized 1, 2
- This applies to both biphasic and monophasic waveforms 1
- Case reports confirm successful cardioversion at 100J on first attempt 3
Polymorphic VT (irregular QRS morphology):
- Never use synchronized cardioversion even if pulse is present 1
- Treat as ventricular fibrillation with unsynchronized high-energy shocks 1
- Synchronization is typically impossible due to irregular rhythm 1
Energy Escalation Protocol
If initial 100J shock fails:
- Increase energy in stepwise fashion for subsequent attempts 1
- The American Heart Association recommends having equipment immediately available, as patients may deteriorate to pulseless VT or VF at any moment 1
- Allow at least 1 minute between consecutive shocks to avoid myocardial damage 2, 4
Technical Considerations for Synchronization
Synchronization requirements:
- Shock must be delivered synchronized to the peak of the QRS complex 5
- Never deliver shock on the T wave under any circumstances 5
- At very rapid rates (<300ms R-R interval), even properly synchronized shocks may fall within the preceding T wave, creating risk 5
- Ideally synchronize to an R wave preceded by a long R-R interval when using low energies 5
Common pitfalls to avoid:
- Never use synchronized cardioversion for pulseless VT—this delays treatment of cardiac arrest 1
- Never use synchronized cardioversion for VF, as the device may not sense a QRS wave and deliver no shock 1
- Never use synchronized cardioversion for polymorphic VT, as synchronization is usually not possible 1
Sedation and Patient Preparation
- Perform cardioversion with adequate sedation or anesthesia in hemodynamically stable patients 2
- Short-acting anesthetic agents are preferred for rapid recovery 2
- Hemodynamically unstable patients require immediate cardioversion without delay for sedation 1
- Ensure fasting, postabsorptive state for elective procedures 5