Idiopathic Ventricular Fibrillation and Otherwise Normal Electrocardiograms

Background: Idiopathic ventricular fibrillation (IVF) in patients with normal baseline electrocardiograms (ECGs) is a rare disease. Little information is available on the clinical features and long-term follow-up of out-of-hospital cardiac arrest (OHCA) survivors presenting with "true" IVF and 12-lead ECGs that remain normal over time. Objective: To define the clinical and ECG characteristics, as well as long-term clinical outcomes of a large cohort of survivors of OHCA due to "true" IVF. Methods: OHCA survivors with VF as the presenting rhythm, normal baseline and follow-up ECGs with no signs of cardiac channelopathy including early repolarization or atrioventricular (AV) conduction abnormalities, and without structural heart disease were included in a registry. Results: A total of 245 OHCA survivors with IVF (median age: 38 years; males 59%) were recruited from 25 centres. All had normal baseline and follow-up ECGs, and no evidence of structural heart disease. An implantable cardioverter-defibrillator (ICD) was implanted in 226 patients (92%), while 18 patients (8%) were treated with drug therapy only. Over a median follow-up of 63 months (interquartile range: 25-110 months), 12 patients died (5%); in 4 of them (1.6%) the lethal event was of cardiac origin. Patients treated with antiarrhythmic drugs (AADs) only had a higher rate of cardiovascular death compared to patients who received an ICD (16% vs. 0.4%, p=0.001). The ECG and echocardiogram of all patients remained unchanged over time. Fifty-two patients (21%) experienced an arrhythmic recurrence. Age ≤ 16 years at the time of the first ventricular arrhythmia was the only predictor of arrhythmic recurrence on multivariable analysis (HR 0.41, 95% CI 0.18-0.92, p=0.03).   Discussion: OHCA survivors of "true" IVF with normal baseline and follow-up ECGs frequently have arrhythmic recurrences, but a good prognosis when treated with an ICD. Children are a category of IVF patients at higher risk of arrhythmic recurrences. Funding: The study was supported by a grant of the Swiss Heart Foundation. Declaration of Interest: G.C. has received a research grant from the Swiss National Foundation. P.L. has received speaker fees and research grants from Boston Scientific, Abbott and Medtronic Research support from UCLH Biomedicine NIHR. F.L. is consultant and has received research support from Medtronic Plc, Abbott, Boston Scientific and Microport. S.B. has received speaker’s bureau from Medtronic and Microport. C.P. has received research grant from Biotronik and Biosense Webster. P.B. is consultant for Biotronik. A.A. is consultant to Abbott, Biosense Webster, Daiichi-Sankyo, Boston Scientific, Medtronic, Microport-CRM; and has received speaker fee from Daiichi-Sankyo, Boston Scientific, Medtronic, Microport-CRM Ethics Approval Statement: Data were collected in accordance with regulations set by the local Institutional Ethics Committee and/or Institutional Review Board.