Does amiodarone (antiarrhythmic medication) prolong the QT (quantitative electrocardiogram) interval?

From the Guidelines

Yes, amiodarone does prolong the QT interval, as evidenced by the 2018 European Heart Rhythm Association (EHRA) consensus document on the management of supraventricular arrhythmias 1. This antiarrhythmic medication, commonly used to treat various cardiac arrhythmias including ventricular tachycardia and atrial fibrillation, has QT prolongation as one of its known effects.

Key Points to Consider

• Amiodarone typically causes a dose-dependent QT prolongation, with more significant effects seen at higher doses.
• The standard oral dosing ranges from 100-400 mg daily for maintenance therapy after a loading dose period, and clinicians should monitor the QT interval regularly during treatment.
• This QT prolongation occurs because amiodarone blocks potassium channels in cardiac cells, extending the repolarization phase of the cardiac action potential.
• While this effect is part of how amiodarone works to control arrhythmias, excessive QT prolongation can potentially lead to torsades de pointes, a dangerous ventricular arrhythmia.
• Caution is particularly warranted when combining amiodarone with other QT-prolonging medications, in patients with existing QT prolongation, electrolyte abnormalities (especially hypokalemia or hypomagnesemia), or underlying structural heart disease.

Monitoring and Precautions

• The QT interval should be monitored closely, especially when initiating or adjusting amiodarone therapy.
• Serum electrolytes, particularly potassium and magnesium, should be maintained within normal ranges to minimize the risk of QT prolongation.
• Patients with a history of heart disease, especially those with left ventricular hypertrophy or heart failure, should be closely monitored for signs of proarrhythmia.
• The use of amiodarone in patients with atrial fibrillation should be carefully considered, weighing the benefits of rhythm control against the potential risks of QT prolongation and proarrhythmia, as noted in the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1.

From the FDA Drug Label

Proarrhythmia, primarily torsade de pointes (TdP), has been associated with prolongation by amiodarone HCl injection of the QTc interval to 500 ms or greater. Although QTc prolongation occurred frequently in patients receiving amiodarone HCl injection, torsade de pointes or new-onset VF occurred infrequently (less than 2%) Patients should be monitored for QTc prolongation during infusion with amiodarone HCl injection.

Yes, amiodarone can prolong the QT interval, as evidenced by the association with torsade de pointes (TdP) and the recommendation for patients to be monitored for QTc prolongation during infusion with amiodarone HCl injection 2.

From the Research

Amiodarone and QT Interval Prolongation

• Amiodarone is known to cause prolongation of the QT interval, as it prolongs the action potential duration in the heart 3, 4, 5.
• Studies have shown that amiodarone therapy can lead to a significant prolongation of the QT interval, which may be a marker for its therapeutic antiarrhythmic effect 3.
• The prolongation of the QT interval by amiodarone can be a concern, as it may increase the risk of torsades de pointes and other arrhythmias, particularly in patients with underlying electrolyte imbalances or other risk factors 4, 6.
• The QT interval prolongation caused by amiodarone can be dose-dependent, with higher doses leading to greater prolongation 7.
• Accurate monitoring of the QT interval is important during amiodarone therapy, particularly in patients with preexisting bundle branch block or other conditions that may affect the QT interval 5.

Clinical Implications

• Amiodarone-induced QT interval prolongation can be a significant concern in clinical practice, particularly in patients with underlying heart conditions or other risk factors for arrhythmias 4, 6.
• Clinicians should be aware of the potential for amiodarone to prolong the QT interval and take steps to monitor patients accordingly, including regular electrocardiograms and monitoring for signs of arrhythmias 3, 5.
• The use of amiodarone in patients with short QT syndrome may be beneficial in prolonging the QT interval and reducing the risk of arrhythmias, but further study is needed to confirm this 7.