From the Guidelines
Amiodarone should not be discontinued solely based on a prolonged QT interval, but rather on a case-by-case basis considering the patient's overall risk factors and clinical presentation. A QT interval of 500 ms is prolonged but not necessarily at the critical threshold for intervention (typically >500-550 ms) [ 1 ]. For patients on amiodarone, some QT prolongation is expected as part of the drug's mechanism of action, and the risk of Torsades de Pointes is lower with amiodarone than with other QT-prolonging medications [ 2 ]. However, it is essential to evaluate for other risk factors that could increase arrhythmia risk, such as:
- Electrolyte abnormalities (particularly hypokalemia or hypomagnesemia)
- Concomitant QT-prolonging medications
- Bradycardia
- Structural heart disease Consider correcting any electrolyte imbalances, reviewing the patient's medication list for potential interactions, and monitoring the QT interval regularly [ 1 ]. If the QT interval continues to increase significantly beyond 500 ms or the patient develops symptoms like syncope, palpitations, or dizziness, dose reduction or discontinuation may be necessary. Amiodarone has a very long half-life (up to 100 days), so effects on QT interval will persist for weeks to months after stopping the medication. According to the 2016 ESC guidelines, amiodarone is an effective multichannel blocker, but it can cause extracardiac side-effects, especially on long-term therapy, and torsades de pointes pro-arrhythmia can occur [ 2 ]. The 2006 ACC/AHA/ESC guidelines recommend removing the offending agent in patients with drug-induced LQTS, but amiodarone is considered a less frequent cause of QT prolongation [ 1 ].
From the Research
Amiodarone and Prolonged QT Interval
- Amiodarone can prolong the QT interval, which increases the risk of torsades de pointes (TdP) 3, 4, 5, 6, 7.
- The risk of TdP is higher in patients with a history of QT interval prolongation, hypokalemia, female sex, drug-drug interactions, advancing age, genetic predisposition, hypomagnesemia, heart failure, bradycardia, and corrected QT (QTc) interval prolongation 3.
- When the QTc interval is 470-500 ms for males, or 480-500 ms for females, or the QTc interval increases 60 ms or more from pretreatment values, dose reduction or discontinuation of the offending drug should be considered where possible, and electrolytes corrected as needed 3.
- If the QTc interval is ≥500 ms, the offending drug should be discontinued, and continuous EKG telemetry monitoring should be performed, or the 12-lead EKG should be repeated every 2-4 hours, until the QT interval has normalized 3.
Discontinuation of Amiodarone
- Amiodarone should be discontinued in patients with a prolonged QT interval, especially if they have a history of TdP or other risk factors for TdP 3, 4, 5, 6, 7.
- Discontinuation of amiodarone may be necessary to prevent further prolongation of the QT interval and reduce the risk of TdP 3.
- Alternative treatments, such as beta-blockers, may be considered for patients with atrial fibrillation or other arrhythmias, especially in those with a prolonged QT interval 7.
Monitoring and Management
- Close monitoring of the QT interval and electrolytes is necessary in patients taking amiodarone, especially in those with a history of QT interval prolongation or TdP 3, 4, 5, 6, 7.
- Patients at risk for QT interval prolongation should be educated to seek medical attention immediately if they experience symptoms such as palpitations, lightheadedness, dizziness, or syncope 3.