System and method for sensing and detection in an extra-cardiovascular implantable cardioverter defibrillator

A method performed by an extra-cardiovascular implantable cardioverter defibrillator (ICD), comprising:

• sensing a first plurality of R-waves by a first sensing channel of a sensing circuit of the extra-cardiovascular ICD in response to crossings of a first R-wave sensing threshold by a first cardiac electrical signal, the first cardiac electrical signal received by the first sensing channel via a first extra-cardiovascular sensing electrode vector coupled to the extra-cardiovascular ICD;
• storing a time segment of a second cardiac electrical signal in response to each one of the first plurality of R-waves sensed by the first sensing channel, the second cardiac electrical signal received via a second extra-cardiovascular sensing electrode vector by a second sensing channel of the extra-cardiovascular ICD;
• determining by a control circuit of the extra-cardiovascular ICD a first plurality of intervals between successive ones of the first plurality of R-waves sensed by the first sensing channel;
• in response to at least a first predetermined number of the first plurality of intervals being less than a tachyarrhythmia detection interval, analyzing at least a portion of the time segment of the second cardiac electrical signal corresponding to a most recent one of the R-waves sensed by the first sensing channel to confirm the most recent one of the R-waves;
• updating an unconfirmed beat count in response to the most recent one of the R-waves not being confirmed based on the analyzing of at least the portion of the corresponding time segment;
• in response to a second predetermined number of the first plurality of intervals being less than the tachyarrhythmia detection interval, comparing the unconfirmed beat count to a rejection threshold;
• and
• withholding detection of a tachyarrhythmia episode in response to the unconfirmed beat count being equal to or greater than the rejection threshold.

A non-transitory, computer-readable storage medium comprising a set of instructions which, when executed by a processor of an extra-cardiovascular implantable cardioverter defibrillator (ICD), cause the extra-cardiovascular ICD to:

• sense a plurality of R-waves by a first sensing channel of a sensing circuit of the extra-cardiovascular ICD in response to crossings of an R-wave sensing threshold by a first cardiac electrical signal, the first cardiac electrical signal received by the first sensing channel via a first extra-cardiovascular sensing electrode vector coupled to the extra-cardiovascular ICD;
• storing a time segment of a second cardiac electrical signal in response to each one of the plurality of R-waves sensed by the first sensing channel, the second cardiac electrical signal received via a second extra-cardiovascular sensing electrode vector by a second sensing channel of the extra-cardiovascular ICD;
• determining by a control circuit of the extra-cardiovascular ICD a plurality of intervals between successive ones of the plurality of R-waves sensed by the first sensing channel;
• in response to at least a first predetermined number of the plurality of intervals being less than a tachyarrhythmia detection interval, analyzing at least a portion of the time segment of the second cardiac electrical signal corresponding to a most recent one of the R-waves sensed by the first sensing channel to confirm the most recent one of the R-waves;
• updating an unconfirmed beat count in response to the most recent one of the R-waves not being confirmed based on the analyzing of at least the portion of the corresponding time segment;
• in response to a second predetermined number of the first plurality of intervals being less than the tachyarrhythmia detection interval, comparing the unconfirmed beat count to a rejection threshold;
• and
• withholding detection of a tachyarrhythmia episode in response to the unconfirmed beat count being equal to or greater than the rejection threshold.