What is the treatment for ventricular (V) tachycardia with amiodarone?

Amiodarone for Ventricular Tachycardia

Immediate Treatment Decision

For hemodynamically unstable VT, perform immediate synchronized electrical cardioversion first; if VT is refractory to cardioversion or recurs despite electrical therapy, then administer amiodarone. 1, 2

For hemodynamically stable monomorphic VT without severe heart failure or acute MI, use procainamide as first-line; reserve amiodarone for patients with severe heart failure or acute MI. 1

Clinical Algorithm for Amiodarone Use

Hemodynamically Unstable VT

• Synchronized electrical cardioversion is the treatment of choice 1
• If VT is refractory to cardioversion or recurs, proceed to amiodarone 1, 2
• Amiodarone terminates acute VT in only 20-40% of cases, so do not expect rapid termination 1

Hemodynamically Stable VT

• If patient has severe heart failure or acute MI: Amiodarone is the preferred first-line agent 1
• If patient does NOT have severe heart failure or acute MI: Procainamide is preferred over amiodarone 1
• Amiodarone is indicated for frequently recurring VF and hemodynamically unstable VT in patients refractory to other therapy 2

Dosing and Administration

IV Loading Protocol

• Initial loading dose: 150 mg IV over 10 minutes 1, 2
• Maintenance infusion: 1 mg/min for 6 hours, then 0.5 mg/min thereafter 1, 2
• For breakthrough episodes of VF or hemodynamically unstable VT, repeat the 150 mg bolus 2
• Most patients require therapy for 48 to 96 hours, but amiodarone may be safely administered for longer periods if necessary 2

Route of Administration

• Use a central venous catheter whenever possible to avoid peripheral vein phlebitis, which occurs frequently with concentrations >2 mg/mL 3
• Use an in-line filter during administration 3

Mandatory Monitoring Requirements

Continuous Monitoring During IV Administration

• ECG monitoring: Watch for bradycardia (occurs in 4.9% of IV patients), AV block, and QT prolongation 1, 3, 2
• Blood pressure monitoring: Hypotension occurs in 16% of patients receiving IV amiodarone 1, 3
• Monitor for second- or third-degree heart block, which represents an absolute contraindication without pacemaker support 3

Response to Adverse Effects

• If bradycardia develops, reduce the infusion rate or discontinue 3, 2
• If hypotension occurs, slow the infusion and add vasopressor drugs, positive inotropic agents, and volume expansion as needed 2

Contraindications

Amiodarone is contraindicated in patients with: 2

• Known hypersensitivity to any component, including iodine
• Cardiogenic shock
• Marked sinus bradycardia
• Second- or third-degree AV block unless a functioning pacemaker is available

Critical Drug Interactions

Before Starting Amiodarone

• Digoxin: Reduce dose by 50% immediately, as amiodarone doubles digoxin levels 3
• Warfarin: Reduce dose by 30-50% and check INR within 3-5 days, as amiodarone significantly increases INR 3
• Beta-blockers and calcium channel blockers: Reduce doses as amiodarone's rate-control effect develops 3

Ongoing Monitoring

• Monitor INR at least weekly for the first 6 weeks when co-administered with warfarin 3
• Patients must not consume grapefruit or grapefruit juice, as it increases plasma amiodarone levels 3

Common Pitfalls and How to Avoid Them

Pitfall #1: Using Amiodarone First-Line for Stable VT Without Heart Failure

• Avoid: Do not use amiodarone as first-line for stable monomorphic VT in patients without heart failure 1
• Instead: Use procainamide first in these patients 1

Pitfall #2: Expecting Rapid VT Termination

• Reality: Amiodarone terminates VT in only 20-40% of cases acutely 1
• Solution: Use electrical cardioversion if immediate termination is needed 1

Pitfall #3: Administering to Patients with Pre-existing Bradycardia

• Risk: IV amiodarone causes bradycardia in 4.9% of patients, regardless of dose 3
• Caution: Use with extreme caution in patients with heart rate <60 bpm; relatively contraindicated unless patient has a pacemaker or the situation is immediately life-threatening 3

Pitfall #4: Inadequate Hemodynamic Monitoring

• Risk: Significant hemodynamic deterioration can occur, including falls in heart rate and cardiac output 4
• Solution: Maintain continuous monitoring and be prepared to slow or stop the infusion 2

Special Populations

Patients with ICDs and Recurrent VT

• ICD implantation is first-line 1
• Catheter ablation is second-line 1
• Beta-blockers combined with amiodarone is third-line 1

Patients with Heart Failure and Low Ejection Fraction

• Amiodarone is a viable option but has neutral effects on survival in this population 1
• All patients in studies had organic heart disease with depressed left ventricular function 5

Pediatric Patients

• Amiodarone may be reasonable for unstable VT with careful hemodynamic monitoring during slow delivery 6
• 71% of children treated with amiodarone experienced cardiovascular side effects in one trial, with both efficacy and adverse events being dose-related 6
• Safety and efficacy have not been established in pediatric patients per FDA labeling 2

Efficacy Data

• In patients with refractory VT/VF, 69% continued amiodarone treatment without recurrence over 6-52 months of follow-up 7
• An additional 6% had nonfatal recurrence successfully managed by increasing the amiodarone dose or adding another agent 7
• Among high-risk patients with refractory VT, 71% had no recurrence of symptomatic VT or VF while on amiodarone therapy 8