An implantable anti-arrhythmia device such as a defibrillator or anti-tachycardia pacemaker with an associated patient activator. In response to the patient activation signal, the implanted device notifies the activator whether an atrial rhythm requiring treatment is present and whether a therapy is available for delivery in response to the patient's request. After the patient is notified that a therapy is pending, the implanted device charges its output capacitors and thereafter determines whether opportunities for prompt synchronization are present with a desired frequency, over a preceding series of depolarizations. If both conditions are met, the likelihood that a defibrillation or cardioversion pulse can be delivered quickly following a patient initiated retrigger signal is high, and the device notifies the patient's activator that it will await receipt of a patient retrigger signal, as a prerequisite for a delivery of the cardioversion or defibrillation pulse. The patient retrigger signal may take the form of a second downlink from the activator to the implanted device, or may take the form of a defined patient action, detected by the implanted device. For example, the implanted device may be provided with an impedance sensor of the sort typically employed in rate responsive implantable pacemakers to measure respiration rate and minute volume. This sensor may be used to detect the action of the patient holding his or her breath, in preparation to receiving the shock. In this embodiment, the patient's own action of bracing to receive the shock may be used as the mechanism for triggering delivery of the shock. An alternative patient trigger might be accomplished by providing the implanted device with a piezoelectric crystal, located on an interior surface of the pacemaker housing, of the sort typically employed to sense physical activity in the rate responsive cardiac pacemakers. This sensor may be employed in the context of the present invention to detect the patient tapping on an implanted device, as a signal to trigger delivery of therapy.