What is the clinical evidence from this study?

Study design: Case Report. Population: Paroxysmal atrial fibrillation (n=1). Intervention: Flecainide.

What question did this study set out to answer?

Investigate the effects of flecainide on QRS complex morphology in atrial flutter cases.

May 9, 2026Open Access

Class IC Atrial Flutter Presenting as a Wide Complex Tachycardia: Lessons from a Case Report

Key Result

Flecainide monotherapy without atrioventricular nodal blockade precipitated atrial flutter with 1:1 conduction, presenting as a wide QRS complex tachycardia mimicking ventricular tachycardia.

Key Points

Investigate the effects of flecainide on QRS complex morphology in atrial flutter cases.
A case report of a patient with paroxysmal atrial fibrillation on oral flecainide monotherapy.
Initial misinterpretation of wide QRS complex tachycardia as ventricular tachycardia.
Analysis of clinical context and ECG findings for proper management.
Wide QRS complex tachycardia was identified, initially treated as ventricular tachycardia.
Progressive QRS widening was noted due to flecainide’s use-dependence mechanism.
Highlights the need for careful clinical and ECG evaluation in arrhythmia management.

Study Design

Type

Case Report (n=1)

Multicenter

Structured PICO

Population

1 patient (62-year-old man) with hypertension, history of cavotricuspid isthmus (CTI) ablation for atrial flutter, and paroxysmal atrial fibrillation.

Intervention

Flecainide monotherapy (without atrioventricular nodal blockade)

Outcome

Wide QRS complex tachycardia (Class IC-induced atrial flutter with 1:1 conduction and aberrancy)

Flecainide monotherapy for atrial fibrillation without AV nodal blockade can cause 1:1 conducted atrial flutter with use-dependent QRS widening, mimicking ventricular tachycardia.

Abstract

Flecainide is an established antiarrhythmic agent for atrial fibrillation (AF), but monotherapy without atrioventricular nodal blockade can precipitate atrial flutter (AFL) with 1:1 conduction. This may result in a wide QRS complex tachycardia due to use-dependent conduction delay, mimicking ventricular tachycardia (VT). We present a case of a wide QRS complex tachycardia in a patient with paroxysmal AF on oral flecainide monotherapy, initially interpreted as VT and managed with intravenous amiodarone. Class IC antiarrhythmic agents may cause progressive QRS widening because of the use-dependence phenomenon. This case underscores the importance of integrating clinical context with ECG analysis and acute and long-term management approaches in symptomatic paroxysmal atrial fibrillation.

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