Management of Irregular Tachycardia

Introduction to Amiodarone Therapy

The European Society of Cardiology recommends amiodarone as an effective option for controlling heart rate in unstable irregular tachycardia without the need for cardioversion to sinus rhythm, and it should be continued by infusion to maintain its therapeutic effect 1
Amiodarone has both sympatholytic and calcium antagonist properties, allowing it to depress AV conduction and effectively control ventricular rate in patients with tachyarrhythmias, including atrial fibrillation 1
Amiodarone is particularly useful in situations where other conventional therapies have failed, and in patients with tachyarrhythmias and heart failure, where other antiarrhythmic agents may be contraindicated or less effective 1, 2

The American Heart Association supports the use of amiodarone with a dosing regimen of 150 mg IV over 10 minutes, followed by a maintenance infusion of 0.5 to 1 mg/min IV (Class IIa, Level of Evidence C) 3, 4
The recommended dosing for amiodarone is as follows:
Oral loading involves 800 mg daily in divided doses for 1 week, followed by 600 mg daily in divided doses for 1 week, and then 400 mg daily in divided doses for 4-6 weeks, with a total loading dose of approximately 10 g 5
The European Society of Cardiology recommends a long-term dose of 200 mg daily for indefinite duration in patients with persistent atrial fibrillation requiring rhythm control 3

Amiodarone can be administered safely in patients with Wolff-Parkinson-White syndrome and associated ventricular preexcitation, unlike beta-blockers, digitalis, and calcium channel blockers which are contraindicated in such cases 1
Continuous monitoring of ECG and vital signs is necessary during IV administration of amiodarone, as well as vigilance for potential hypotension, bradyarrhythmias, or AV blocks 6
Patients receiving amiodarone should be monitored in the hospital for 24-48 hours after cardioversion to evaluate the effects of decreased heart rate and allow for rapid intervention in case of torsades de pointes 2
Regular monitoring should include thyroid studies, liver transaminase levels, and directed physical examination every 6 months, with chest radiograph and pulmonary function tests as needed, and ophthalmologic examination if visual symptoms develop 5

Unlike digoxin, which may take up to 6 hours to reach its maximum effect, IV amiodarone begins to act more quickly, although it still requires approximately 60 minutes to initiate its therapeutic effect 1
The American College of Cardiology recommends the infusion of amiodarone after successful electrical cardioversion of tachyarrhythmias to prevent immediate and subacute recurrences, especially in patients with refractory or hemodynamically unstable tachyarrhythmias 7
Amiodarone is particularly effective for subacute recurrences (1 day to 2 weeks), with a median time to recurrence of 487 days compared to 74 days for sotalol 1
Amiodarone has been shown to be superior to other antiarrhythmics in maintaining sinus rhythm after cardioversion, with 62% of patients remaining in sinus rhythm at 1 year compared to 23% with class I agents 7
In the CTAF study, amiodarone maintained sinus rhythm more successfully than propafenone or sotalol (69% vs 39%) during a 16-month follow-up 7

Amiodarone is associated with several side effects, including hypotension, bradycardia and heart block, pulmonary toxicity (0.3% annual rate), thyroid dysfunction, QT interval prolongation, corneal deposits and optic neuropathy, skin discoloration, and warfarin interaction, which requires dose reduction 8, 9, 3, 5
The American Heart Association recommends reducing warfarin dose by one-third to one-half and closely monitoring prothrombin time when co-administering amiodarone with warfarin 5
Amiodarone may serve as an adjunct to reduce shock frequency in patients with implantable cardioverter-defibrillators (ICDs), as noted by medical societies 9
In minimally symptomatic atrial fibrillation patients on anticoagulation, long-term amiodarone therapy may not be justified due to potential toxicity, as noted by the American Academy of Family Physicians 5