Loperamide, a μ-opioid receptor agonist, can cause cardiotoxicity by inhibiting the potassium ion channel and slowing cardiomyocyte repolarization. This, in turn, can lead to frequent early afterdepolarizations, the most common mechanism of drug-induced long QT syndrome and torsades de pointes. Apical hypertrophic cardiomyopathy (AHCM) is a nonobstructive hypertrophic cardiomyopathy rarely associated with malignant arrhythmias. We present a case of loperamide-induced malignant ventricular arrhythmia revealing underlying AHCM in a 25-year-old woman with a history of sudden cardiac arrest (SCA) and opioid use. It is important to evaluate for structural heart disease in all patients presenting with SCA, regardless of presumed etiology such as drug-induced cardiotoxicity, to prevent missed opportunities for adequate treatment. Furthermore, the diagnosis of AHCM in SCA warrants further genetic evaluation for variances with a predilection for malignant arrhythmias.
Keywords: apical hypertrophic cardiomyopathy; loperamide; structural heart disease; sudden cardiac arrest; ventricular tachycardia.