An electrotherapy device includes a power supply and electrodes. The electrodes are coupled to the power supply to deliver a defibrillating shock to a patient. Electronic circuitry is coupled to the electrodes and is operable to detect heart rhythms via the electrodes. Further, control circuitry is coupled to the electronic circuitry and the power supply and configurable to selectively classify patient heart rhythms that generate a shockable condition, the control circuitry operable to arm the power supply for energizing the electrodes responsive to such detectable shockable condition. A method is also provided.