Inappropriate ventricular fibrillation annotation and defibrillator discharge despite the same tachycardia cycle length in ventricular tachycardia-1 zone in an Abbott defibrillator - What is the mechanism?

Newer devices incorporate advanced algorithms to have more accurate delivery of implantable cardioverter-defibrillator (ICD) therapy. Newer models of Abbott Implantable cardioverter-defibrillators like Gallant and Entrant have a new ventricular fibrillation (VF) therapy assurance algorithm. This algorithm has a proven role in avoiding under-detection of VF where some of the smaller electrograms are under-sensed. We report a case of ventricular fibrillation therapy assurance (VFTA) algorithm malfunction in a 48-year-old lady having single chamber Entrant Implantable cardioverter-defibrillator, where the patient received inappropriate therapies. The VFTA algorithm eventually had to be turned off.