Abstract 14930: A Case of Flecainide Toxicity Causing Wide Complex Tachycardia, Unresponsiveness, Hemodynamic Instability and Pacemaker Under-Sensing

Abstract

Introduction: Flecainide toxicity (FT) is an uncommon yet potentially lethal complication. We report a case of FT precipitated by acute kidney injury (AKI) in a patient with paroxysmal atrial fibrillation (AF) and a permanent pacemaker (PPM), who presented with wide complex tachycardia (WCT) and PPM under-sensing. Case presentation: An above 85-year-old female with paroxysmal AF and a PPM presented with an episode of unresponsiveness. While en route to the ED via ambulance, she had another episode associated with hemodynamic instability precipitated by a WCT. She regained consciousness after 1 biphasic DC shock. An EKG in the ED revealed sinus rhythm with atrial under-sensing and pacing spikes during ventricular refractory period (see picture). Laboratory data were consistent with AKI and normal electrolytes levels. PPM interrogation showed atrial under-sensing. Flecainide was discontinued and following drug washout the EKG changes resolved and the QRS normalized. She was discharged on amiodarone with no recurrence of arrhythmias on follow up. Discussion: Flecainide is Class 1C Antiarrhythmic drug that blocks fast the sodium channels. Prolongation of PR interval and QRS duration, in addition to supraventricular and ventricular arrhythmias, may occur with FT. Left ventricular dysfunction, myocardial scar, and high serum levels are considered risk factors for proarrhythmia. The drug half-life is prolonged in patients with renal disease/AKI. There are limited data on PPM malfunction due to FT, but it may cause increased pacing thresholds and failure to capture. Sodium bicarbonate, lidocaine, and ECMO have been used in treatment. Conclusion: FT can lead to lethal arrhythmias and PPM malfunction. Since flecainide serum levels are not always readily available, its diagnosis can be challenging. Therefore, physicians should be aware of the clinical presentation and EKG changes that accompany FT.