An automated external defibrillator (AED) and methods for reducing the delay between termination of cardiopulmonary resuscitation (CPR) and administration of a defibrillating shock, among other disclosed apparatus and methods. In one embodiment, the AED includes an ECG sensor that obtains an ECG signal corresponding to patient heart activity and a prompting device that provides instructions regarding cardiopulmonary resuscitation. The AED also has a control system including a microprocessor programmed to run two rhythm analysis algorithms after instructions to terminate CPR. The two rhythm analysis algorithms analyze segments of the ECG signal for recognizing the presence of a shockable rhythm, with one algorithm having a delayed start relative to the other algorithm. The AED additionally includes a therapy generation circuit for treating the shockable rhythm with a defibrillation pulse in response to the control system determining the presence of a shockable rhythm.