Electrophysiologic effects of flecainide acetate on sinus node function, anomalous atrioventricular connections, and...

Area of Science:

• Cardiology
• Electrophysiology
• Pharmacology

Background:

• Flecainide acetate is a Class Ic antiarrhythmic drug.
• Its acute electrophysiologic effects require detailed investigation.

Purpose of the Study:

• To assess the acute electrophysiologic effects of intravenous flecainide acetate.
• To evaluate flecainide's impact on sinus node function, atrioventricular pathways, and pacing thresholds.

Main Methods:

• Electrophysiologic studies were conducted in 71 patients.
• Intravenous flecainide acetate (2 mg/kg) was administered.
• Effects on sinus node recovery time, sinoatrial conduction, accessory pathway refractoriness, AV nodal pathways, and pacing thresholds were measured.

Main Results:

• Flecainide slightly shortened sinus cycle length but had variable effects on sinus node recovery and sinoatrial conduction.
• Significant prolongation of accessory atrioventricular pathway refractoriness occurred, with block in 33-44% of patients.
• Flecainide successfully terminated 86% of orthodromic atrioventricular reentrant tachycardias and 88% of intra-AV nodal reentrant tachycardias.
• Acute and chronic endocardial pacing thresholds increased post-flecainide administration.

Conclusions:

• Intravenous flecainide exerts significant electrophysiologic effects, including modulation of sinus node function and marked prolongation of refractoriness in anomalous AV pathways.
• The drug is effective in terminating orthodromic atrioventricular and intra-AV nodal reentrant tachycardias.
• Flecainide increases pacing thresholds, a factor to consider in patients with implanted devices.