Methods and apparatus for storing data records associated with a medical monitoring event in a data structure. Upon detection of a possible occurrence of a physiological event by one group of monitoring elements, an implanted device records data received from another group of monitoring elements. The implanted device obtains and stores the data in the data record in a first data structure that is age-based. Before an oldest data record is lost, the oldest data record may be stored in a second data structure that is priority index-based. The priority index may be determined by a severity level and may be further determined by associated factors. The implanted device may organize, off-load, report, and/or display a plurality of data records based on an associated priority index. Additionally, the implanted device may select a subset or composite of physiologic channels from the available physiologic channels based on a selection criterion.