In general, the invention is directed towards techniques for adaptively prioritizing cardiac episode data in a memory of an implanted medical device (IMD). More specifically, the IMD receives new cardiac episode data, assigns each piece of data a priority value, and stores the data in a memory of the IMD. The IMD can further recalculate initial priority values assigned to stored cardiac episode data in response to subsequent cardiac episode data. In this manner, the prioritization scheme used by the IMD is adaptive, i.e., changes as more contextual information regarding the cardiac episode and subsequent cardiac episodes becomes available. Upon exceeding a memory capacity threshold, the IMD identifies the stored cardiac episode data with a lowest priority from the hierarchical priority relationship, and overwrites the identified portion of the stored cardiac episode data with the new cardiac episode data.