Methods and devices providing multiple criteria for use in arrhythmia identification. Based on inputs including defined rules or parameters, one of a more conservative or more aggressive set of arrhythmia identification parameters can be selected. One or the other of the selectable sets of arrhythmia identification parameters may also be adaptive or modifiable during the use of the system, for example, in response to identified nonsustained episodes, the more conservative set of arrhythmia identification parameters can be modified to become still more conservative. Such modification of arrhythmia identification criteria allows reduced time to therapy when indicated, while allowing more deliberate decisions in other circumstances.