This tracing highlight the potential risks associated with inappropriate therapies delivered in the context of T-wave oversensing. Both shocks and ATP may induce life-threatening ventricular arrhythmias since they can be delivered during the vulnerable period. Shocks are synchronized either on the R-wave or on the T-wave (50%/50%). In this case, the first paced cycle of the ATP sequence corresponds also to the onset-to peak of the T-wave explaining the induction of a real episode of VF. The diagnosis made by the device was initially wrong (false VF) but turned to be finally right after acceleration into a polymorphic ventricular arrhythmia.