different cardiac event however in general it would be improper to place the marker before the beginning of a cross chamber blanking period after generating the one or more synthetic event markers as shown in fig4 the exemplary embodiment continues to block 220 as shown in fig2 block 220 entails calculating an average interval based on a set of one or more intervals including one or more of the new intervals resulting from division of the abnormal interval in some embodiments implantable device 100 includes a wireless transceiver which permits use of an external programmer to interrogate and program device 100 via bi directional radio communications at a minimum this allows adjustment of one or more of the parameters governing one or more portions of the new methods for example one could adjust the number of intervals used in computing the average interval and or the size threshold for the abnormal interval these and other parameters can then be set and changed based on observations of a specific patient or group of patients in other embodiments the inventor contemplates replacing or supplementing an existing software module or algorithm with one in accord with the present invention in furtherance of the art the inventor devised new methods for processing heart electrical signals some of which ensure accurate interval measurements without unduly delaying therapy decisions or consuming significant battery power one exemplary method identifies or detects an abnormal interval measurement from a set of interval measurements and either disqualifies the abnormal interval from use in making therapy decisions or divides the abnormal interval into two or more other intervals ultimately this and other methods embodying teachings of the present invention can be incorporated into implantable medical devices for example defibrillators pacemakers or cardioverter defibrillators to identify and treat abnormal rhythmic.