In a hemodynamically stable patient with sustained monomorphic ventricular tachycardia and no signs of shock, chest pain, syncope, or acute heart failure, is the first‑line treatment intravenous amiodarone rather than synchronized DC cardioversion?

Hemodynamically Stable Sustained Monomorphic Ventricular Tachycardia: First-Line Treatment

For a hemodynamically stable patient with sustained monomorphic ventricular tachycardia, synchronized DC cardioversion—not amiodarone—is the definitive first-line treatment and should be performed immediately with appropriate sedation. 1

Why Cardioversion is Superior to Amiodarone

Synchronized electrical cardioversion is the most effective acute therapy for stable monomorphic VT and carries Class I evidence from both the European Society of Cardiology and the American College of Cardiology. 1 This recommendation supersedes pharmacologic options because:

• Cardioversion terminates VT immediately, whereas amiodarone's class III antiarrhythmic effect requires 20–30 minutes to become apparent and is poorly effective for acute termination. 1, 2
• In a retrospective case series of 28 patients with sustained monomorphic VT treated with IV amiodarone (150 mg), the termination rate was only 29% (95% CI 13–49%), demonstrating poor efficacy. 2
• The FDA label for IV amiodarone indicates it for "hemodynamically unstable VT," not stable VT, further supporting that it is not the optimal choice for stable patients. 3

Cardioversion Protocol for Stable Monomorphic VT

When you confirm the diagnosis (QRS >140 ms with RBBB or >160 ms with LBBB morphology, AV dissociation, fusion beats) 1:

• Deliver an initial synchronized shock of 100 J for monomorphic VT with rates >150 bpm. 1, 4
• Provide brief sedation before the shock if the patient's hemodynamic status permits. 1
• If the first shock fails, escalate energy sequentially to 200 J, then 300 J, then 360 J. 1
• Never delay cardioversion in favor of additional pharmacologic therapy once you have decided to proceed; waiting offers no benefit and may allow hemodynamic deterioration. 1

When to Use Pharmacologic Therapy Instead

Antiarrhythmic drugs are appropriate only when cardioversion is unavailable, refused, or specifically deferred 1:

First-Line Pharmacologic Agent: Procainamide

• IV procainamide (10 mg/kg at 50–100 mg/min over 10–20 minutes) is the preferred first-line antiarrhythmic for stable monomorphic VT, with Class IIa, Level B evidence from the American Heart Association—superior to amiodarone's Class IIb recommendation. 1, 4, 5
• Procainamide demonstrates the greatest conversion efficacy among all antiarrhythmic drugs for acute termination of stable monomorphic VT. 1, 5
• Monitor blood pressure and ECG continuously during infusion because hypotension is common. 1, 6
• Do not use procainamide in patients with severe heart failure or acute myocardial infarction. 4, 6

When to Choose Amiodarone Over Procainamide

Intravenous amiodarone is preferred over procainamide only when the patient has:

• Heart failure 1, 4
• Suspected myocardial ischemia 1, 4
• Left ventricular ejection fraction ≤40% 1

However, even in these contexts, amiodarone's slow onset (20–30 minutes) makes it less optimal for rapid conversion. 1 It should be reserved for VT that is refractory to cardioversion or recurrent despite other agents. 1, 6

Alternative Agents

• Sotalol may be considered for stable sustained monomorphic VT, including post-MI patients (Class IIa). 1
• Lidocaine provides only moderate efficacy and should be reserved as second-line, though it may be reasonable specifically in the setting of acute myocardial ischemia (1 mg/kg bolus, then 0.5 mg/kg every 8–10 min). 1, 6

Critical Contraindications

Never administer calcium-channel blockers (verapamil, diltiazem) for wide-complex tachycardia in structural heart disease, as they can precipitate ventricular fibrillation and hemodynamic collapse (Class III—harmful). 1, 4, 6 The only exception is confirmed left-ventricular fascicular VT (RBBB morphology with left axis deviation), where verapamil or β-blockers are safe and effective. 1, 4

Management Algorithm

1. Confirm diagnosis with 12-lead ECG (QRS >140 ms, AV dissociation, fusion beats). 1, 4
2. Verify hemodynamic stability: systolic BP ≥90 mmHg, no chest pain, no pulmonary edema, no altered mental status. 1
3. Proceed directly to synchronized cardioversion with 100 J after brief sedation. 1
4. If cardioversion is unavailable or deferred, use IV procainamide (unless contraindicated by heart failure or acute MI). 1, 4
5. If procainamide is contraindicated, use IV amiodarone (150 mg over 10 minutes, then maintenance infusion). 1, 6
6. If VT recurs after cardioversion, administer antiarrhythmic therapy (procainamide or amiodarone) to prevent re-initiation, then evaluate for catheter ablation. 1

Common Pitfalls

• Do not assume amiodarone is first-line simply because it is commonly used; the evidence shows it is poorly effective for acute termination of stable VT. 2, 5
• Do not delay cardioversion to try multiple antiarrhythmic drugs sequentially; cardioversion is more effective and should be performed early. 1
• Re-evaluate hemodynamic status frequently; if the patient decompensates (systolic BP <90 mmHg, pulmonary edema, altered mental status, chest pain), proceed immediately to cardioversion regardless of prior pharmacologic attempts. 6