Idiopathic Ventricular Fibrillation

Sudden cardiac arrest (SCA) and sudden cardiac death (SCD) are disastrous outcomes of various predominant cardiac diseases. The leading cause of SCA and SCD is coronary artery disease. However, SCA/SCD in young patients is mainly caused by congenital disorders of primary arrhythmic or structural origin. SCD is defined as death from an unexpected circulatory arrest, usually because of a cardiac arrhythmia occurring within an hour of the onset of symptoms. The definition of SCA is similar, with the addition that a medical intervention (eg, defibrillation) reverses the event. Idiopathic ventricular fibrillation (IVF) is a rare cause of SCA. Patients with IVF present with a sudden onset of ventricular fibrillation (VF) of unknown origin that is not identified even after extensive diagnostic testing. The exact incidence of IVF is unknown but is declining with the advance of diagnostic testing and the discovery of primary arrhythmia syndromes, such as the Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), long-QT syndrome (LQTS), short-QT syndrome, and early repolarization syndrome (ERS). Although the exact definition of IVF has changed during the years and although new diagnostic tools are available, no specific guidelines have been developed for the definition and diagnosis of IVF, as well as a protocol for exclusion of specific cardiac diseases that cause SCA and SCD. In this review, we discuss the definition of IVF, overlap with other primary arrhythmia syndromes, the diagnosis, and follow-up of patients with IVF.