CONGRESS ABSTRACT

INTRODUCTION: Flecainide is a class Ic antiarrhythmic drug, approved for the control of supraventricular and ventricular arrhythmias in the absence of structural heart disease. lacosamide is an antiepileptic drug approved as monotherapy for the treatment of partial seizures with or without secondary generalization. Both drugs act by blocking fast voltage-gated sodium channels expressed in various tissues. The cardiac isoform Naᵥ1.5 (SCN5A) is strongly blocked by flecainide. Some experimental studies have demonstrated an inhibitory effect of lacosamide on NaV1.5 (SCN5A). Dose-dependent inhibition of cardiac sodium channels produces a marked slowing of conduction velocity in fibers dependent on fast depolarization channels. This could be one of the mechanisms hypothesized to underlie the potential proarrhythmic risk and PR and QRS widening on the ECG associated with flecainide and lacosamide. Concomitant use of the two drugs could lead to a potential additive effect on cardiac sodium channel inhibition and, consequently, be associated with an increased risk of arrhythmic events.CASE REPORT: An 82-year-old female with a history of paroxysmal atrial fibrillation and epileptic seizures undergoing treatment with flecainide and lacosamide, presented to the emergency department due to palpitations. The admission ECG showed wide QRS tachycardia (206 ms) with left bundle branch block morphology at a heart rate of 110 bpm. After administration of 100 mg metoprolol IV and suspension of flecainide, atrial fibrillation emerged with a mean ventricular response of 130 bpm, conducted with incomplete left bundle branch block (QRS 110 ms). After washout from flecainide and reduction of lacosamide, the ECG showed resolution of QRS widening, with disappearance of left bundle branch block morphology. Even after spontaneous restoration of sinus rhythm, normalized intraventricular conduction with narrow QRS persisted. The patient was discharged home with rhythm control therapy with amiodarone and and with optimized antiepileptic therapy with reduced dosing of lacosamide.CONCLUSIONS: It has been widely documented that the independent use of lacosamide and flecainide may be associated with cardiac arrhythmias. In contrast, there is little information on the combined administration of them.The definition of therapeutic indications requires careful.The initial assessment and periodic monitoring should be part of the multidisciplinary clinical management of these patients.