Is amiodarone (antiarrhythmic medication) appropriate for treating scar-mediated ventricular tachycardia (VT)?

Amiodarone for Scar-Mediated Ventricular Tachycardia

Amiodarone is appropriate for scar-mediated ventricular tachycardia (VT) when other therapies have failed, but should not be considered first-line therapy due to its significant side effect profile and limited impact on mortality.

Role in Management of Scar-Mediated VT

• Amiodarone is indicated for initiation of treatment and prophylaxis of frequently recurring ventricular fibrillation and hemodynamically unstable ventricular tachycardia in patients refractory to other therapy 1
• For patients with scar-related heart disease presenting with VT, catheter ablation has evolved into an important treatment option and should be considered before long-term amiodarone therapy 2
• Amiodarone is generally well tolerated hemodynamically in the setting of acute heart failure with ventricular arrhythmias and is preferred for longer-term administration when necessary 2

Efficacy in Scar-Mediated VT

• Clinical studies have shown that 64-75% of patients with refractory VT or VF can be successfully managed with amiodarone when the dose is adjusted based on clinical response 3, 4
• Amiodarone has been associated with overall neutral effects on survival when administered to patients with low ejection fraction and heart failure 2
• The SCD-HeFT trial showed no survival benefit to patients with heart failure (NYHA functional class II and III) and LVEF ≤35% treated with amiodarone empirically 2

Use with ICDs

• ICDs are highly effective in preventing death due to ventricular tachyarrhythmias, but frequent shocks can lead to reduced quality of life 2
• For recurrent ICD discharges from VT despite antiarrhythmic therapy, catheter ablation may be more effective than increasing amiodarone dosage 2
• Beta-blocker therapy in combination with amiodarone reduces the number of ICD shocks, though side effects may result in drug discontinuation 2

Dosing Considerations

• Loading dose: 800-1600 mg/day orally in divided doses 5
• Maintenance dose: 200-600 mg daily after a loading period (typically after a total of 10 g has been given) 5, 4
• For intravenous administration in acute settings: 150 mg over 10 minutes, followed by 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours 5

Adverse Effects and Monitoring

• Significant toxicity occurs in approximately 50% of patients on high-dose amiodarone therapy 3
• Common side effects include:
  • Thyroid abnormalities (6%) 3
  • Pulmonary toxicity (5-7%) 3, 4
  • Neurologic effects: tremor, ataxia (35-52%) 3, 6
  • Visual disturbances (6%) 3
  • Gastrointestinal symptoms (8%) 3
• Regular monitoring is required for:
  • Thyroid function 1
  • Pulmonary function 1
  • Liver function 2
  • Ophthalmic examination 1

Treatment Algorithm for Scar-Mediated VT

1. First-line therapy: ICD implantation for patients with scar-related VT at high risk of sudden cardiac death 2
2. Second-line therapy: Catheter ablation for recurrent VT episodes 2
3. Third-line therapy: Beta-blockers in combination with amiodarone for patients with recurrent VT despite ICD and/or catheter ablation 2
4. Fourth-line therapy: Amiodarone monotherapy for patients who are not candidates for ICD or catheter ablation 2

Important Caveats

• Amiodarone should not be considered as part of the routine treatment of patients with heart failure, with or without frequent premature ventricular depolarizations or asymptomatic non-sustained VT 2
• Inducible VT during electrophysiologic testing in patients taking amiodarone does not preclude a favorable clinical response 7
• The first sign of antiarrhythmic failure with amiodarone may manifest as sudden cardiac death 6
• Amiodarone-induced hyperthyroidism may result in thyrotoxicosis and/or the possibility of arrhythmia breakthrough or aggravation 1