Holter, Loop Recorder, and Event Counter Capabilities of Implanted Devices

The current generation of cardiac pacemakers and implantable cardioverter defibrillators almost all have some capabilities to store data regarding device activity and patient events for future retrieval. This information may provide valuable information regarding device function and whether this is proving valuable in patient management. Examples include "pace-sense" counters, which can reveal under sensing of patient events, and serial lead impedance measurements, which are able to demonstrate trends not seen on isolated measurements. Holter capabilities become vital in more advanced devices for documenting the utility of, and fine tuning the programming of features such as antitachycardia pacing, rate-responsiveness, and mode-switching. Finally, the ability to store patient events as marker channels and even intracardiac electrograms adds a diagnostic capability not available through external monitoring. This role has now been advanced by the development of a purely diagnostic implantable loop recorder.