Method and apparatus for identifying oversensing using far-field intracardiac electrograms and marker channels

A method of detecting the occurrence of intrinsic depolarizations of a heart chamber comprising:

• obtaining a far-field electrogram (FF EGM) signal comprising a stream of digital sample points;
• generating a derivative signal from the FF EGM;
• identifying patterns in the derivative signal that indicate a peak in the FF EGM signal;
• removing identified patterns in the derivative signal having magnitudes that do not meet minimum slope criteria from further analysis;
• identifying possible intrinsic depolarizations as occurring near polarity change points in the remaining identified patterns of the derivative signal;
• removing possible intrinsic depolarizations having corresponding FF EGM amplitude values below an amplitude threshold criterion from further consideration as possible intrinsic depolarizations;
• removing possible intrinsic depolarizations that occur within a blanking period immediately after a preceding intrinsic depolarization from further consideration as possible intrinsic depolarizations;
• and
• marking the remaining possible intrinsic depolarizations as sensed events from the FF EGM signal.

A method of identifying oversensing of cardiac R-waves by an implantable medical device (IMD), comprising:

• detecting intrinsic R-waves from a near-field electrogram (NF EGM) signal and defining such detected R-waves as VS-NF events;
• detecting intrinsic R-waves from a far-field electrogram (FF EGM) signal and defining such detected R-waves as VS-FF events;
• comparing the VS-FF events to the VS-NF events to determine which VS-NF events have a corresponding VS-FF event, and defining such VS-NF events as mapped VS-NF events;
• comparing the VS-FF events to the VS-NF events to determine which VS-NF events do not have a corresponding VS-FF event and defining such VS-NF events an unmapped VS-NF events;
• determining whether unmapped VS-NF events exceed mapped VS-NF events by a predetermined amount to indicate the presence of oversensing;
• and
• classifying the type of oversensing as being one of lead failure/fracture/connection, T-wave oversensing, R-wave double counting, and other type of oversensing after the presence of oversensing is indicated, the lead failure type of oversensing being indicated by the presence of more than a predetermined number of unmapped VS-NF events between a predetermined number of mapped VS-NF events, the T-wave type of oversensing being indicated by the presence of alternating morphologies, the R-wave double-counting type of oversensing being indicated by the presence of a short-long interval pattern, and the other type of oversensing being indicated when none of lead failure, T-wave oversensing, and R-wave double counting are indicated.