Bedside Snapshot
Indication
Unstable tachycardia with pulses (hemodynamically compromised)
Contraindications
  • Stable patients (prefer pharmacologic)
  • Digitalis toxicity
Energy Selection
  • Narrow complex: 50-100J
  • Wide complex: 100J
  • AFib: 120-200J (biphasic)
Key Points
  • SYNC mode delivers shock on R-wave
  • Sedation required for conscious patients
  • Have defibrillator ready for VFib
Quick Reference
  • SYNC Mode: Ensures shock delivered during QRS (R-wave peak), not T-wave
  • Procedure Time: 2-5 minutes (excluding sedation time)
  • Success Rate: >90% for AFib/AFL, >95% for SVT
  • Sedation: Etomidate 0.1-0.2mg/kg or midazolam 1-2mg IV preferred
Indications & Contraindications

Indications

  • Unstable tachycardia with pulses: HR >150 with signs of instability
  • Signs of instability: Hypotension, altered mental status, chest pain, acute heart failure
  • Specific rhythms: Unstable AFib with RVR, atrial flutter, SVT, unstable VT with pulse

Absolute Contraindications

  • Stable patient (pharmacologic therapy preferred)
  • Digitalis toxicity (can precipitate VFib)
  • Multifocal atrial tachycardia (MAT) - unlikely to cardiovert

Relative Contraindications

  • Sinus tachycardia (not a shockable rhythm; treat underlying cause)
  • Chronic AFib >48 hours without anticoagulation (thromboembolic risk)
  • Severe electrolyte abnormalities (correct first if stable)
Critical: If patient unstable, cardiovert immediately. Don't delay for labs or anticoagulation.
Equipment & Preparation

Essential Equipment

  • Defibrillator: With SYNC capability (check sync indicator flashing)
  • Monitoring: Continuous ECG, SpO2, BP
  • Pads/Paddles: Anterior-lateral or anterior-posterior placement
  • Sedation: Etomidate 0.1-0.2mg/kg or midazolam 1-2mg + fentanyl 1mcg/kg
  • Airway equipment: BVM, suction, oxygen
  • Crash cart: Immediate access in case of complications

Patient Preparation

  • Consent: Obtain if time permits; implied in emergency
  • IV access: Establish if not already present
  • Oxygen: Apply supplemental O2
  • Remove metal: Jewelry, medication patches (especially nitroglycerin)
  • Dry chest: Pat dry if sweaty for optimal pad contact
Pearl: Announce "charging" and "stand clear" loudly. Ensure no one touching patient or bed during shock.
Energy Selection by Rhythm
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Rhythm Initial Energy Subsequent Shocks Notes
Narrow Complex (SVT) 50-100 J 100, 200, 300, 360 J Start low; usually responds quickly
Atrial Flutter 50-100 J 100, 200, 300, 360 J Often cardioverts at lower energies
Atrial Fibrillation 120-200 J 200, 300, 360 J Requires higher energy than SVT
Wide Complex (VT) 100 J 150, 200, 300, 360 J Treat as VT if uncertain
Biphasic vs Monophasic: Above energies for biphasic. For monophasic, use 200J initial, then 300J, 360J.
Step-by-Step Procedure

Step 1: Assess Patient & Rhythm

Confirm unstable tachycardia with pulses. Identify rhythm (narrow vs wide complex). Assess for signs of instability: hypotension, altered mental status, chest pain, pulmonary edema.

Step 2: Prepare Equipment

Turn on defibrillator, attach monitoring leads or pads. Press SYNC button (confirm sync markers appearing on QRS complexes). Select appropriate starting energy based on rhythm.

Critical: VERIFY SYNC MODE. Machine may default to unsynchronized after each shock; must re-engage SYNC for each subsequent shock.

Step 3: Sedate Patient (if conscious)

Administer procedural sedation (etomidate 0.1-0.2mg/kg or midazolam 1-2mg IV). Wait for adequate sedation before shocking. Maintain airway patency and monitor respiratory status.

Step 4: Charge and Deliver Shock

Announce "charging." Press charge button. Announce "stand clear" and perform visual sweep. Ensure no one touching patient. Press SHOCK button. Hold until shock delivers (may have 0.5-2 second delay while syncing).

Step 5: Assess Response

Check monitor immediately. If successful, patient should convert to sinus rhythm. If unsuccessful, re-engage SYNC mode (critical!), increase energy per protocol, and repeat. Monitor for post-cardioversion hypotension.

Post-Cardioversion: Obtain 12-lead ECG. Monitor for recurrent arrhythmia (common in first 24 hours). Consider antiarrhythmic to maintain sinus rhythm.
Clinical Pearls & Tips
  • Pad placement: Anterior-lateral (standard) or anterior-posterior (higher success for AFib/obesity)
  • SYNC delay: Don't release shock button too quickly; device needs time to detect R-wave
  • Defibrillation backup: If cardioversion converts to VFib, immediately switch to DEFIB mode and shock
  • Amiodarone bridge: Consider loading 150mg over 10min before cardioversion to improve success
  • TEE consideration: For AFib >48hrs, consider TEE to rule out LA thrombus if time permits
Why SYNC Matters: Shock on T-wave can trigger R-on-T phenomenon leading to VFib. Synchronized shock ensures delivery during refractory period (QRS).
Complications & Troubleshooting

Common Complications

  • Conversion to VFib: Immediately defibrillate (unsynchronized 200J)
  • Hypotension post-cardioversion: Treat with fluids, consider vasopressors
  • Skin burns: Ensure good pad contact, adequate conductive gel
  • Thromboembolic events: Risk increased if AFib >48hrs; anticoagulate post-procedure
  • Myocardial stunning: Transient decreased EF; supportive care

Troubleshooting Sync Issues

  • Sync markers not appearing: Improve ECG signal quality, reposition leads/pads, increase gain
  • Shock won't deliver: Ensure sync engaged, adequate QRS amplitude for detection
  • Repeated failures: Try higher energy, different pad position, consider pharmacologic therapy
Red Flag: If patient deteriorates or becomes pulseless during preparation, abandon cardioversion and begin CPR/defibrillation as indicated.
Post-Procedure Care
  • Continuous monitoring: Cardiac monitor for minimum 4-6 hours post-cardioversion
  • 12-lead ECG: Obtain immediately post-procedure and compare to baseline
  • Anticoagulation: Initiate or continue if AFib/AFL, especially if duration >48hrs
  • Antiarrhythmic therapy: Consider to maintain sinus rhythm (amiodarone, sotalol, flecainide)
  • Identify trigger: Electrolyte abnormalities, thyroid dysfunction, cardiac ischemia
Documentation: Record rhythm before/after, energy levels used, number of shocks, sedation given, complications, and disposition.
References
  1. American Heart Association. (2020). 2020 AHA Guidelines for CPR and ECC. Circulation. 142(16_suppl_2).
  2. January CT, et al. (2019). 2019 AHA/ACC/HRS Focused Update on Atrial Fibrillation. Circulation. 140(2):e125-e151.
  3. Link MS, et al. (2015). Adult Advanced Cardiovascular Life Support. Circulation. 132(18 suppl 2):S444-S464.
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