Chronic monitoring of various cardiac intervals provides valuable information about the condition of subject's heart. The monitoring of intervals with an implantable medical device (IMD) provides information about cardiac episodes of arrhythmia, heart rate, heart rate variability, and the like.
Thus, there is a need in the art for an improved IMD including IMDs that only monitor, and IMD that also deliver therapy (e.g., single, dual, and triple chamber devices) that monitors traditional cardiac intervals, newly discovered algorithms that can gather other cardiac information. Specifically, there is a need for apparatus and methods to easily and efficiently measure P-wave duration, ending time, and QRS duration to beneficially provide predictors of improving and failing cardiac status for subjects that have an IMD.