Chart — Cardiac
Defibrillation vs Cardioversion Chart
Defibrillation and synchronized cardioversion both use electrical energy to treat dangerous arrhythmias, but they differ in critical ways. This chart provides a direct comparison to support rapid decision-making in cardiac emergencies.
Educational use only. Electrical therapy requires clinical training, ACLS certification, and institutional protocols. This chart supports learning — always follow provider orders and your facility's emergency procedures. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Side-by-Side Comparison
| Feature | Defibrillation | Synchronized Cardioversion |
|---|---|---|
| Synchronized? | No — asynchronous (fires immediately) | Yes — timed to R wave (QRS) |
| Device Mode | SYNC OFF | SYNC ON |
| Patient Status | Pulseless, unresponsive — cardiac arrest | Usually has pulse; may be conscious |
| Setting | Emergency (cardiac arrest) | Urgent or elective (may require sedation) |
| Indication — Rhythms | VF, pulseless VT | Unstable SVT, atrial fibrillation/flutter with pulse, stable monomorphic VT with pulse |
| Initial Energy (Biphasic) | 120–200 J (manufacturer-specific) | 50–200 J (rhythm-dependent; typically lower than defibrillation) |
| CPR Before Shock? | Yes — begin CPR immediately; minimize interruptions | No (patient has pulse); prepare sedation and airway support |
| Sedation Required? | No — patient is unconscious | Yes — for conscious patients; procedural sedation per order |
| Why Synced or Not? | No organized rhythm to sync to; timing irrelevant | Avoids delivering shock during T wave (vulnerable period) — prevents inducing VF |
| Discharge Timing | Immediate on button press | Brief delay — device waits for R wave before firing; hold button until discharge occurs |
Critical Safety Points
For Both Procedures:
- Announce “Clear” and visually confirm all personnel are away from the patient and bed before delivering shock
- Remove supplemental oxygen from the immediate area — O₂ supports combustion
- Remove transdermal patches (nitroglycerin, nicotine, hormone) from chest before placing pads
- Position pads at least 8 cm from implanted pacemakers or ICDs
- Ensure pads have firm contact and skin is dry
Cardioversion-Specific:
- Always confirm SYNC is ON before each shock — many defibrillators automatically revert to unsynchronized mode after each delivery. Forgetting to re-enable SYNC and shocking an organized rhythm can induce VF
- For atrial fibrillation of unknown or > 48-hour duration: ensure anticoagulation or rule out intracardiac thrombus before elective cardioversion
- Hold the discharge button until the shock fires — the device pauses to synchronize with the next R wave
Defibrillation-Specific:
- Resume CPR immediately after shock — do not pause to check pulse or rhythm; resume CPR for 2 minutes, then reassess
- Keep CPR interruptions to < 10 seconds for rhythm check and shock delivery
- Document time to first shock — every minute of delay without defibrillation reduces survival by approximately 10%
Typical Energy Settings by Rhythm (Biphasic)
| Rhythm | Modality | Initial Energy | Notes |
|---|---|---|---|
| VF / Pulseless VT | Defibrillation | 120–200 J | Use device-specific dose; escalate subsequent shocks |
| Atrial Fibrillation | Cardioversion | 120–200 J | Higher initial energy for Afib due to irregular waveform |
| Atrial Flutter / SVT | Cardioversion | 50–100 J | Often terminates at lower energy; escalate if needed |
| Monomorphic VT (with pulse) | Cardioversion | 100 J | Escalate if no conversion; ensure SYNC is ON |
Always follow your institution's protocol and the specific device manufacturer's recommended energy settings.
Related Resources
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with AHA ACLS Guidelines. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →