Methods and devices for accelerating the identification of arrhythmias in implantable medical devices. Following identification of a potential arrhythmia onset condition, such as by identifying a plurality of closely coupled detected events, a retrospective pattern recognition analysis is performed to seek out a possible onset comprising a Torsades de Pointes. Although the methods and devices are designed to target Torsades de Pointes, wider application to other arrhythmia onset conditions is contemplated as well.