Implantable cardiac stimulator with automatic electrogram profiling

A method for monitoring a patient's heart, comprising:

• amplifying a cardiac signal;
• comparing said amplified signal to an adjustable reference signal;
• adjusting said reference signal to one of a plurality of magnitudes in response to said step of comparing said signal;
• and
• storing representations of the frequency of occurrences of each of said magnitudes of said reference signal in a memory device.

An implantable medical device for electrically stimulating a human heart and monitoring said heart, including:

• a plurality of electrodes;
• a sense circuit coupled to said electrodes to condition electrical signals from said electrodes, said sense circuit including a comparator for comparing said electrical signals to one of a plurality of threshold targets;
• a pulse generator adapted to generate pacing pulses;
• a processor having means for setting said threshold target and means for computing a histogram of the relative number of cardiac cycles associated with particular settings of said threshold targets occurring over a predetermined period of time;
• and
• a memory device for storing said histogram.