(160) Lacosamide-Induced Lethal Cardiac Arrhythmias: A Rare but Significant Side Effect of Lacosamide

Introduction: Largely unrecognized, lacosamide has the potential to cause arrhythmias. Given its increasing use due to its potential benefit in refractory seizures, it is prudent to be aware of this rare but lethal side effect and need for vigilant ECG, electrolyte, and drug–drug monitoring. This case describes malignant arrhythmia in a patient treated with adjunctive lacosamide for status epilepticus.

Description: 75-year-old man with a history of heart failure with preserved ejection fraction and bladder cancer was admitted for sepsis due to a UTI and obstructive uropathy. Treated with ceftriaxone, he underwent cystoscopy and ureteral stent placement. His hospital course was complicated by multiple brief episodes of upper extremity shaking, confusion, and ocular deviation, leading to the initiation of levetiracetam. EEG revealed non-convulsive status epilepticus, prompting the addition of Depakote and later lacosamide, with no clear benefit. This led to intubation and sedation with propofol, resulting in significant EEG improvement. Subsequently, the patient experienced a cardiac arrest with asystole, from which he was successfully resuscitated. Post-cardiac arrest, he developed wide-complex tachycardia and QRS prolongation. Due to the high suspicion of medication-induced arrhythmia, lacosamide was discontinued. This led to the cessation of malignant arrhythmias, with no further arrhythmias noted on telemetry during the hospital course.

Discussion: Lacosamide is a relatively newer antiepileptic drug that enhances the slow inactivation of voltage-gated sodium channels (VGSC), inhibiting repetitive neuronal activity. VGSCs are also present in cardiac tissue, contributing to normal cardiac rhythm. In a recent systemic analysis in 2021 most commonly reported arrhythmia were new-onset atrial fibrillation (17.6%), complete heart block (17.6%), Mobitz type 1 Atrio-ventricular block (11.8%), sinus pauses (11.8%), pulseless electrical activity (5.9%) and widening QRS complex (5.9%). Although limited literature exists on the causal relationship between lacosamide and arrhythmia, the onset of ventricular tachycardia during lacosamide exposure, its resolution after discontinuation, and the absence of recurrence suggest a causal link.