Idiopathic ventricular fibrillation

Idiopathic ventricular fibrillation (VF) is an uncommon disease that manifests as syncope or cardiac arrest caused by rapid polymorphic ventricular tachycardia (VT) or VF in the absence of organic heart disease. Because the term “idiopathic” means “absence of identifiable etiology”, idiopathic VF is essentially a diagnosis by exclusion. However, typical clinical and electrophysiological characteristics present in some patients often allows for a straight-forward positive diagnosis. Moreover, it is now clear that many patients with idiopathic VF have, in fact, a genetic channelopathy, presenting in the form of “idiopathic VF with early repolarization” or “congenital short QT syndrome (SQTS)”. This chapter summarizes the history of this disease as we know it since its first description in 1929 to the most recent developments in our understanding of its pathophysiology. Idiopathic VF leads to syncope or cardiac arrest typically during early adulthood and involves a relatively high incidence of arrhythmic storms (with clusters of VF episodes) that fail to respond to conventional antiarrhythmic therapy (including amiodarone) but respond exquisitely to intravenous isoproterenol and oral quinidine. The mode of onset of spontaneous arrhythmias in idiopathic VF, namely, the triggering of rapid polymorphic VT/VF by single ventricular extrasystoles with very short (R-on-T) coupling intervals. The extrasystoles triggering VF have been mapped mainly to the His-Purkinje fibers in the left ventricle and may be ablated. The clinical data linking idiopathic VF to the congenital SQTS and the malignant early repolarization syndrome are presented and the genetic mutations so far described are presented.