What is the approach to managing a prolonged QT (QT interval) interval?

From the Guidelines

The approach to managing a prolonged QT interval should prioritize avoiding QT-prolonging medications, maintaining normal potassium and magnesium balance, and careful monitoring of the QTc interval, as recommended by the 2017 AHA/ACC/HRS guideline 1. When managing a prolonged QT interval, several key considerations must be taken into account to minimize the risk of adverse events such as Torsades de Pointes.

• Avoiding the use of QT-prolonging medications is crucial, unless there is no suitable alternative, and even then, careful monitoring of the QTc interval is necessary 1.
• Maintaining normal potassium and magnesium balance is essential, as hypokalemia and hypomagnesemia can precipitate episodes of Torsades de Pointes 1.
• The concurrent use of stimulant or non-stimulant attention deficit/hyperactivity medications should be avoided, particularly in males, due to the increased risk of syncope/cardiac arrest in long QT syndrome patients 1.
• Fever should be reduced with antipyretics, as it can prolong the QT interval in patients with long QT syndrome type 2 1.
• In cases where QT-prolonging medications are necessary, the risk of Torsades de Pointes can be mitigated by correcting electrolyte abnormalities, avoiding other QT-prolonging drugs, and monitoring the QTc interval closely 1.
• Intravenous magnesium can be effective in suppressing episodes of Torsades de Pointes, even when serum magnesium is normal, and temporary pacing may be necessary in recurrent cases 1. It is also important to note that the risk of adverse events increases in patients with long QT syndrome with QTc prolongation >500 ms, and therefore, treatment should be discontinued if QTc exceeds 500 ms or increases by more than 60 ms from baseline 1.

From the FDA Drug Label

Theoretically, therefore, mexiletine may be useful in the treatment of ventricular arrhythmias associated with a prolonged QT interval

• Management approach: Mexiletine may be considered for the treatment of ventricular arrhythmias associated with a prolonged QT interval.
• Key consideration: The drug does not prolong ventricular depolarization (QRS duration) or repolarization (QT intervals) as measured by electrocardiography, making it a potential option for managing prolonged QT interval. 2

From the Research

Approach to Managing Prolonged QT Interval

The approach to managing a prolonged QT interval involves several key steps:

• Withdrawal of any offending drugs or correction of the underlying cause of the QT prolongation 3, 4, 5
• Accurate and timely recognition of torsades de pointes, as traditional antiarrhythmic drug treatment may worsen the problem rather than improve it 3
• Use of beta blockers to prevent problems in congenitally at-risk patients 3, 5
• Consideration of an implantable cardioverter defibrillator in some patients with recurrent episodes 3
• Short-term treatment aimed at preventing recurrences of torsades, including intravenous magnesium and potassium administration, temporary cardiac pacing, and correction of electrolyte imbalance 5
• Long-term treatment aimed at reducing the QT-interval duration and preventing torsades and sudden death, including use of oral beta-adrenergic blockers, implantation of permanent pacemaker/cardioverter-defibrillator, and left thoracic sympathectomy 5

Risk Factors for QTc Prolongation

Several risk factors for QTc prolongation have been identified, including:

• Demographic factors, such as age and sex 6
• Comorbidities, such as heart disease and diabetes 6
• Electrolyte imbalances, such as hypokalemia and hypomagnesemia 3, 4, 6
• QTc-prolonging medication, such as antiarrhythmic drugs and certain antibiotics 3, 4, 6
• Other factors, such as drug overdose and hypokalemia 7

Emergency Department Approach

In the emergency department, providers should be aware of:

• Commonly used medications that can prolong the QT interval, such as antipsychotics and antiemetics 7
• Patient history that may contribute to QTc prolongation, such as drug overdose or hypokalemia 7
• The need for thorough investigation and management of QTc prolongation, including withdrawal of offending drugs and correction of underlying causes 7