From the Guidelines
Empiric use of amiodarone after cardiac surgery should be approached with caution due to its potential downsides, including significant adverse effects and numerous drug interactions, and a more targeted approach based on individual risk assessment for post-operative arrhythmias is generally preferred. Amiodarone can cause significant adverse effects including bradycardia, QT prolongation, hypotension, and pulmonary toxicity, as noted in studies such as 1. Even short-term use may lead to thyroid dysfunction, liver enzyme abnormalities, and corneal microdeposits. The drug has an extremely long half-life (up to 100 days), meaning adverse effects can persist long after discontinuation. Amiodarone also has numerous drug interactions due to its inhibition of cytochrome P450 enzymes, potentially affecting anticoagulants, statins, and other cardiac medications commonly used post-surgery.
When considering the use of amiodarone, it is essential to weigh the benefits against the risks, particularly in patients who may not need the medication. The 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation suggests that preoperative administration of amiodarone reduces the incidence of AF in patients undergoing cardiac surgery and is reasonable as prophylactic therapy for patients at high risk for postoperative AF, as stated in 1. However, this guideline also emphasizes the importance of individualized treatment approaches.
Some key points to consider when using amiodarone include:
- Typical loading doses are 5-7 mg/kg IV over the first 24-48 hours, followed by oral maintenance of 200-400 mg daily.
- Close monitoring of ECG, thyroid, liver, and pulmonary function is necessary.
- The choice of antiarrhythmic drug should be guided by patient characteristics, as noted in 1.
- There are limited data on guiding treatment for the rhythm control of AF following cardiac surgery in patients who do not require urgent cardioversion.
Overall, while amiodarone can be an effective medication for preventing and treating post-operative atrial fibrillation, its use should be carefully considered and monitored due to its potential downsides, and a more targeted approach based on individual risk assessment is generally preferred, as supported by studies such as 1 and 1.
From the FDA Drug Label
In patients with life-threatening arrhythmias, the potential risk of hepatic injury should be weighed against the potential benefit of amiodarone HCl injection therapy, but patients receiving amiodarone HCl injection should be monitored carefully for evidence of progressive hepatic injury Proarrhythmia, primarily torsade de pointes (TdP), has been associated with prolongation by amiodarone HCl injection of the QTc interval to 500 ms or greater. There have been reports of QTc prolongation, with or without TdP, in patients taking amiodarone when fluoroquinolones, macrolide antibiotics, or azoles were administered concomitantly Early-onset Pulmonary Toxicity There have been postmarketing reports of acute-onset (days to weeks) pulmonary injury in patients treated with intravenous amiodarone. Two percent (2%) of patients were reported to have adult respiratory distress syndrome (ARDS) during clinical studies involving 48 hours of therapy. Postoperatively, occurrences of ARDS have been reported in patients receiving oral amiodarone therapy who have undergone either cardiac or noncardiac surgery. The potential downsides to the empiric use of Amiodarone after cardiac surgery include:
- Hepatic injury: risk of progressive hepatic injury
- Proarrhythmia: risk of worsening existing arrhythmias or precipitating a new arrhythmia, including torsade de pointes (TdP)
- Pulmonary toxicity: risk of early-onset pulmonary injury, adult respiratory distress syndrome (ARDS), and pulmonary fibrosis
- Thyroid dysfunction: risk of arrhythmia breakthrough or exacerbation in patients with thyroid dysfunction
- Optic neuropathy and/or neuritis: risk of visual impairment or permanent blindness 2
From the Research
Potential Downsides to Empiric Use of Amiodarone
The empiric use of Amiodarone after cardiac surgery may have several potential downsides, including:
- Adverse events such as nausea, bradycardia, and increased intensive care monitoring and support 3
- No significant difference in adverse events after operation compared to beta-blocker groups, but subgroup analysis revealed that amiodarone significantly improved postoperative atrial fibrillation as compared with propranolol 4
- Bradycardia necessitating dose reduction or drug withdrawal occurred in patients treated with amiodarone, although at a lower rate than those treated with sotalol or metoprolol 5
- Serious adverse events were uncommon and similar in each group, but the use of amiodarone did not result in a reduction in the length of hospital stay 6
Comparison with Beta-Blockers
Studies have compared the efficacy of amiodarone with beta-blockers in preventing postoperative atrial fibrillation, with results including:
- Amiodarone was found to be superior to propranolol in preventing postoperative atrial fibrillation, but not superior to beta-blockers in general 4, 6
- The incidence of postoperative atrial fibrillation was lower in patients treated with amiodarone compared to those treated with propranolol, but not significantly different from those treated with beta-blockers in general 4, 6
- Amiodarone may be more effective than beta-blockers in certain subgroups, such as patients undergoing coronary artery bypass grafting 6
Intravenous Regimens
Intravenous amiodarone regimens have been studied as a potential prophylactic treatment for atrial fibrillation after open heart surgery, with results including:
- Intravenous amiodarone may provide safe and effective prophylaxis against atrial fibrillation in many patients undergoing coronary bypass surgery 7
- Early intravenous amiodarone, followed by oral amiodarone, appears to be superior to propranolol in the prevention of postoperative atrial fibrillation 6