Ventricular Fibrillation Following Electrical Cardioversion

Figure

Shock delivery during the vulnerable phase due to T-wave oversensing by the external defibrillator. Left half of the image: the inappropriate shock during low-amplitude sinus rhythm due to incorrect synchronization (arrow). Right half of the image: the ventricular fibrillation induced as a result.

An individual in their 60s underwent electrical cardioversion for persistent atrial fibrillation. After three failed attempts at synchronized cardioversion, treatment-refractory ventricular fibrillation developed during the fourth synchronized shock. During resuscitation, the patient was placed on extracorporeal circulation (ECMELLA—a combination of extracorporeal membrane oxygenation and a microaxial left ventricular assist device). After transfer to our intensive care unit, ventricular fibrillation was successfully terminated by defibrillation following propranolol administration. Subsequently, after rapid weaning and a 17-day intensive care stay, the patient was transferred to a rehabilitation facility. Ventricular fibrillation was induced by a shock delivered during the repolarization phase due to T-wave oversensing (misinterpretation of the T wave as an R wave) by the defibrillator. Moreover, electrotherapy was inappropriate, given that sinus rhythm had been restored in the meantime (Figure). Signal quality of the surface ECG was markedly reduced due to obesity. This case highlights that, prior to planned cardioversion, the current rhythm needs to be checked, as atrial fibrillation can terminate spontaneously, in which case cardioversion would no longer be indicated. T-wave oversensing can, in very rare cases, also occur when external defibrillators are used; therefore, correct synchronization should be verified. Since low voltage promotes T-wave oversensing, optimization of the ECG signal should be pursued.

Dr. med. Hatti Seidl, Dr. med. Marcel Haug, Deutsches Herzzentrum der Charité, [e-mail]

Dr. med. Jens Nee, Medizinische Klinik mit Schwerpunkt Nephrologie und Internistische Intensivmedizin, Charité – Universitätsmedizin Berlin

Conflict of interest statement: The authors state that no conflict of interest exists.

Translated from the original German by Christine Rye.

Cite this as: Seidl H, Nee J, Haug M: Ventricular fibrillation following electrical cardioversion. Dtsch Arztebl Int 2026; 123: 326b. DOI: 10.3238/arztebl.m2025.0235