Defibrillation vs Cardioversion vs Pacing: When Electricity Is the Answer
Three electrical therapies, three indications — synchronized or not, energy settings, and the safety steps that get tested.
December 13, 2026 · 7 min read
Students mix these up constantly. Each has one clear indication.
Defibrillation — unsynchronized
For pulseless VF and pulseless VT only. Biphasic energy per manufacturer, commonly 120–200 J. Shock, then immediately resume compressions for two minutes without a pulse check.
Synchronized cardioversion
For unstable patients with a pulse and a tachycardia: SVT, atrial fibrillation with instability, or VT with a pulse. The monitor times the shock to the R wave to avoid inducing VF. Sedate when time permits. Typical starting energy is 50–100 J for narrow regular rhythms and 100 J or more for wide.
Transcutaneous pacing
For symptomatic bradycardia and high-degree AV block unresponsive to atropine. Set rate 60–80, increase milliamps until capture, then confirm a matching pulse.
Safety every time
- Clear the patient verbally and visually
- Remove supplemental oxygen from the chest
- Dry the chest, remove medication patches
- Pads at least one inch from an implanted device
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