Patent ID: 8594775

Claim:
A method comprising: retrieving electrogram (EGM) data for N cardiac cycles from a memory of an implantable medical device, wherein N is an integer greater than 1; categorizing each of the N cardiac cycles into one of a plurality of categories based on a morphology of the N cardiac cycles; performing comparisons between pairs of the N cardiac cycles, each of the comparisons between two cardiac cycles including: detecting a mismatch between the two cardiac cycles when the two cardiac cycles are in different categories; and detecting a match between the two cardiac cycles when the two cardiac cycles are in the same category; and classifying the rhythm of the N cardiac cycles based on a number of detected matches and detected mismatches, wherein categorizing each of the N cardiac cycles comprises categorizing a single cardiac cycle of the N cardiac cycles based on at least one of a positive peak value of the single cardiac cycle, a negative peak value of the single cardiac cycle, and an order in which the positive peak value and the negative peak value occur in the single cardiac cycle, and further comprising: categorizing the single cardiac cycle as a dominantly positive cycle when the positive peak value is greater than the absolute value of the negative peak value by a first threshold amount; and categorizing the single cardiac cycle as a dominantly negative cycle when the absolute value of the negative peak value is greater than the positive peak value by a second threshold amount.