From the Guidelines
Patients with a long QT interval should avoid QT-prolonging medications and maintain normal potassium and magnesium balance to reduce the risk of adverse events, particularly when the QTc interval is greater than 500 ms. According to the 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1, the risk of adverse events increases in patients with long QT syndrome with prolongation of the QTc >500 ms.
Key considerations in managing long QT interval include:
- Avoiding QT-prolonging medications unless there is no suitable alternative, with careful monitoring of the QTc during therapy 1
- Maintaining normal potassium and magnesium balance, especially when medications or situations that promote depletion are encountered 1
- Reducing fever with antipyretics, as fever can prolong the QT interval in patients with long QT syndrome type 2 1
- Considering beta-blockers, such as nadolol or propranolol, to prevent dangerous arrhythmias, and an implantable cardioverter-defibrillator (ICD) for high-risk patients
It is also important to note that concurrent use of stimulant or non-stimulant attention deficit/hyperactivity medications may be associated with an increased risk of syncope/cardiac arrest in long QT syndrome, particularly in males 1. Episodes of torsades de pointes can be precipitated by exposure to a QT prolonging medication, or hypokalemia induced by diuretics or gastrointestinal illness 1.
From the Research
Definition and Causes of Long QT Interval
- Long QT syndrome (LQTS) is a severe cardiac disorder characterized by an abnormally prolonged QTc interval on an electrocardiogram (ECG) 2.
- The use of certain medications, particularly anti-arrhythmic drugs such as quinidine, sotalol, and amiodarone, can lead to acquired LQTS by prolonging the QT interval through the inhibition of specific ion channels responsible for heart repolarization 2.
- Psychotropic medications have also been associated with prolongation of the QT interval, especially in those with medical illness, and are linked to lethal ventricular arrhythmias, such as Torsades de Pointes (TdP) 3.
Risk Factors and Management
- Prolonged QT interval significantly elevates the risk of a life-threatening arrhythmia called torsade de pointes 2.
- The management of this side effect typically involves reducing the medication dosage or discontinuing it altogether and, in some cases, employing selective beta blockers 2.
- Close monitoring of the QT interval is recommended for patients receiving anti-arrhythmic therapy, and consideration should be given to patient-specific risk factors for LQTS, including age, sex, and electrolyte imbalances 2.
- Life-style modification, beta blockers, and ICD implantation are the most important therapeutic modalities in proper management of patients with LQT 4.
Medications Associated with QT Prolongation
- Antiarrhythmic drugs such as amiodarone, sotalol, dofetilide, procainamide, quinidine, and flecainide have the potential to cause QT prolongation as a side effect 2.
- Among antidepressant medications, citalopram does appear to prolong the QT interval more than other selective serotonin reuptake inhibitors, though the clinical significance of this prolongation remains unclear 3.
- Among atypical antipsychotic agents, ziprasidone-and possibly iloperidone-is associated with the greatest QT prolongation, whereas aripiprazole appears safest from this standpoint 3.