Efficient generation of sensing signals in an implantable medical device such as a pacemaker or ICD

A system for displaying cardiac signals, comprising:

• an implantable cardiac stimulation device having:
• means for receiving a cardiac signal;
• filtering means for filtering the cardiac signal with a first filter to produce a first signal and for filtering the cardiac signal with a second filter to produce a second signal, wherein the second filter is selected to highlight a characteristic feature of heart activity;
• control means for controlling the delivery of therapeutic electrical stimulation to the heart based, at least in part, on the second signal;
• and
• transmitting means for transmitting the first signal;
• and
• an external programmer having:
• receiving means, telemetrically coupled to the transmitting means, for receiving the first signal;
• processing means for processing the first signal and generating an emulated version of the second signal;
• and
• displaying means for displaying at least one of the received first signal or the emulated version of the second signal.