An exemplary method includes detecting two or more event interval times associated with an arrhythmic condition, averaging event interval times to provide an average event interval time, providing a fraction and calling for delivery of an anti-arrhythmia shock at a delivery time based on the fraction and the average event interval time. In this exemplary method, the events optionally correspond to early coarse ventricular fibrillation events and the delivery time is optionally less than about three seconds from the detecting of a first event of a first event interval time. Other exemplary methods, devices, systems, etc., are also disclosed.