Electrocardiography-documented sudden cardiac death due to ventricular fibrillation in a young cat without echocardiographic evidence of severe structural heart disease

An asymptomatic three-year-old male European Domestic Shorthair cat was referred for an irregular heart auscultation. Apart from localized concentric left ventricular septal hypertrophy, echocardiography was normal. However, ventricular ectopy was observed on electrocardiography (ECG) during echocardiography. The cat died suddenly 55 minutes after the start of the subsequent Holter ECG. Analysis showed sinus rhythm interrupted by 192 single ventricular premature complexes, a ventricular couplet, two incidents of ventricular bigeminy and two runs of ventricular tachycardia (VT). The last run of VT deteriorated into ventricular fibrillation (VF) and ultimately cardiac arrest. Structural heart disease including mild feline hypertrophic cardiomyopathy or myocarditis, primary arrhythmia (channelopathy) or extra-cardiac disease were maintained as differential diagnosis. Unfortunately, a necropsy was declined leaving no definitive diagnosis available. In this case report, it is shown that VF due to ventricular ectopy is a possible cause of SCD even in asymptomatic cats with only mild echocardiographic signs of structural heart disease.