What are the steps of synchronized cardioversion for a hemodynamically stable patient with monomorphic ventricular tachycardia?

Synchronized Cardioversion for Hemodynamically Stable Monomorphic Ventricular Tachycardia

For hemodynamically stable monomorphic VT, synchronized electrical cardioversion with 100 J is the most effective first-line treatment and should be performed after brief sedation or anesthesia. 1

Pre-Cardioversion Steps

Confirm the Diagnosis

• Obtain a 12-lead ECG immediately to confirm monomorphic VT and exclude supraventricular tachycardia with aberrancy 1, 2
• Look for diagnostic features: QRS width >0.14 seconds with RBBB pattern or >0.16 seconds with LBBB pattern, AV dissociation, fusion or capture beats, and RS interval >100 ms in any precordial lead 1
• When uncertain whether the rhythm is VT or SVT with aberrancy, always treat as VT to avoid the catastrophic risk of undertreatment 1

Verify Hemodynamic Stability

• Confirm the patient has systolic blood pressure ≥90 mmHg, normal mental status, no chest pain, no pulmonary edema, and no signs of shock 1, 3
• If any signs of instability are present (hypotension, altered mental status, chest pain, acute heart failure, or shock), proceed immediately to cardioversion without delay 1, 3

Prepare Equipment and Monitoring

• Ensure continuous cardiac monitoring, pulse oximetry, and blood pressure monitoring are in place 3
• Have resuscitation equipment immediately available, including a defibrillator, airway management supplies, and emergency medications, as cardioversion may occasionally induce ventricular fibrillation or asystole 3
• Establish secure intravenous access 3

Cardioversion Procedure

Sedation

• Administer brief anesthesia or procedural sedation when the patient's hemodynamic status permits 1
• Common agents include midazolam, propofol, or etomidate, titrated to effect 1

Energy Selection and Delivery

• Set the defibrillator to synchronized mode to ensure the shock is delivered on the R-wave peak, never on the T-wave, which could precipitate ventricular fibrillation 3
• Deliver an initial synchronized shock of 100 J for monomorphic VT with rates >150 bpm 1, 2
• Verify that synchronization markers appear on each QRS complex before delivering the shock 3

If First Shock Fails

• If the initial 100 J shock is unsuccessful, escalate energy sequentially: 200 J, then 300 J, then 360 J 1
• Do not delay with additional pharmacologic therapy; escalate the energy instead 1
• For refractory cases after standard escalation, double sequential synchronized cardioversion may be considered as a rescue technique 4

Post-Cardioversion Management

Immediate Monitoring

• Monitor closely for atrial or ventricular premature complexes immediately after cardioversion, as these may trigger recurrent VT 5, 3
• Watch for transient depression of myocardial function, particularly after repeated shocks or higher energies 3

Prevention of Recurrence

• If VT recurs after successful cardioversion, administer intravenous antiarrhythmic therapy to prevent acute reinitiation 1, 3
• For patients without severe heart failure or acute MI, intravenous procainamide (10 mg/kg at 50-100 mg/min over 10-20 minutes) is the preferred agent 1, 2
• For patients with heart failure, suspected ischemia, or left ventricular ejection fraction ≤40%, intravenous amiodarone is preferred over procainamide 1, 2

Critical Safety Pitfalls

Medications to Avoid

• Never administer calcium-channel blockers (verapamil, diltiazem) for wide-complex tachycardia in structural heart disease, as they can precipitate ventricular fibrillation and hemodynamic collapse 1, 3
• The only exception is confirmed left-ventricular fascicular VT (RBBB morphology with left axis deviation), where verapamil or β-blockers are safe 1, 2

Synchronization Errors

• Always verify proper synchronization before each shock delivery 3
• Failure to synchronize may result in shock-on-T phenomenon and degeneration to ventricular fibrillation 3

Delaying Cardioversion

• Do not delay cardioversion in favor of prolonged pharmacologic trials, as electrical cardioversion is more effective than any medication 1
• Even after amiodarone loading, proceed directly to cardioversion rather than waiting for drug effect, which requires 20-30 minutes and offers no additional benefit 1