Sinus node dysfunction and sudden cardiac death following treatment with encainide

Area of Science:

• Cardiology
• Electrophysiology
• Pharmacology

Background:

• Encainide is a class Ic antiarrhythmic medication.
• It is generally considered to have minimal impact on sinus node function.
• This study investigates an unusual adverse effect of encainide.

Observation:

• A patient experienced cardiac arrest after one week of encainide treatment for ventricular extrasystoles.
• Programmed ventricular stimulation did not induce ventricular tachyarrhythmias.
• Pre-treatment sinus node function was normal.

Findings:

• Electrophysiological studies revealed significant impairment of sinus node function after encainide therapy.
• The patient's sinus node dysfunction was severe and potentially life-threatening.
• No arrhythmias occurred during a 6-month follow-up after discontinuing encainide.

Implications:

• Encainide can cause severe sinus node dysfunction, a critical and potentially fatal adverse effect.
• Clinicians should be vigilant for sinus node impairment in patients receiving encainide.
• This finding challenges the established understanding of encainide's effects on cardiac electrophysiology.