Resolution of severe dilated cardiomyopathy with significant arrhythmia burden using hydroquinidine, in addition to guideline-directed medical therapy, in a patient with a pathogenic

Background: Dilated cardiomyopathy has a diverse aetiology. Around 20% of cases have an underlying genetic cause. A subset of patients with dilated cardiomyopathy is prone to arrhythmia ('arrhythmogenic' cardiomyopathy). (Likely) Pathogenic variants of Case summary: A 17-year-old male presents with new-onset severe left ventricular systolic dysfunction with atrial flutter and significant ventricular ectopy. Despite medical therapy, his management was challenging. A LifeVest was fitted to allow outpatient optimization of his medications whilst bridging to a decision about implantable cardioverter defibrillator implantation. Specialist genetic testing revealed a pathogenic variant in Discussion: This atypical presentation of a cardiomyopathy was driven, at least in part, by the patient's extensive arrhythmia. Previous research has shown variable, short-term effects of sodium channel antagonists in familial p.R814W variants. Contrastingly, in our patient, sustained and long-term improvement was observed with the use of hydroquinidine. Close multidisciplinary team working and early genetic testing facilitated personalized care in our patient's case, resulting in a favourable outcome.