A cautionary tale: the risks of flecainide treatment for myotonic dystrophy

Area of Science:

• Cardiology
• Neurology
• Pharmacology

Background:

• Myotonic dystrophy (MD) frequently involves cardiac abnormalities, with arrhythmias causing a significant portion of mortality.
• Sodium channel blockers, including flecainide, are used to manage muscle symptoms in MD by targeting abnormal sodium channel activity.
• Flecainide's mechanism involves blocking mutant sodium channels, improving muscle relaxation in myotonia.

Purpose of the Study:

• To report a case of flecainide-induced ventricular tachycardia (VT) in a patient with myotonic dystrophy (MD).
• To highlight the proarrhythmic potential of flecainide, even when used for therapeutic benefits in MD patients.
• To emphasize the need for thorough cardiac evaluation in MD patients considering Class 1 antiarrhythmic agents.

Main Methods:

• Case report of a 41-year-old woman with MD.
• Observation of adverse cardiac event (VT) during flecainide therapy.
• Discontinuation of flecainide and subsequent electrophysiological assessment.

Main Results:

• The patient developed ventricular tachycardia (VT) while receiving flecainide for muscle strength.
• VT was no longer inducible after flecainide was discontinued.
• This suggests flecainide acted as a proarrhythmic agent in this specific patient context.

Conclusions:

• Flecainide, while effective for myotonia, carries a risk of proarrhythmia, particularly VT, in susceptible individuals like those with MD.
• Comprehensive cardiac assessment and risk stratification are essential for MD patients.
• Consideration of electrophysiological studies for high-risk MD patients is recommended before initiating Class 1 antiarrhythmic drugs.