Methods and devices for accurately classifying cardiac activity

An implantable medical device (IMD) comprising a plurality of electrodes coupled to operational circuitry configured to perform cardiac signal analysis, the IMD including a canister having the operational circuitry and at least one electrode associated therewith, the operational circuitry being configured to:

• detect a cardiac cycle by comparison of a cardiac signal from the plurality of electrodes to a threshold, thereby declaring a detected event having a signal waveform;
• compare the signal waveform to a template having a plurality of fiducial points in a correlation analysis to yield a correlation score by:
• selecting a first fiducial point in the signal waveform corresponding to a first fiducial point in the template and using the first fiducial points to align the signal waveform and the template to perform a first comparison yielding a first comparison score;
• selecting a second fiducial point in the signal waveform corresponding to a second fiducial point in the template and using the second fiducial points to align the signal waveform and the template to perform a second comparison yielding a second comparison score;
• and
• selecting whichever of the first and second comparison scores is greater to generate the correlation score;
• and
• determine, using the correlation score, whether the detected cardiac event is indicative of an arrhythmic condition.

An implantable medical device (IMD) comprising a plurality of electrodes coupled to operational circuitry configured to perform cardiac signal analysis, the IMD including a canister having the operational circuitry and at least one electrode associated therewith, the operational circuitry being configured to:

• detect at least first, second and third detected events by comparison of a cardiac signal from the plurality of electrodes to a threshold defined by a detection profile and declaring a detected event having a signal waveform when the threshold is crossed, wherein the first detected event occurs later in time than the second detected event, and the second detected event occurs later in time than the third detected event;
• compare the first detected event to the second detected event to yield a first comparison score;
• compare the first detected event to the third detected event to yield a second comparison score;
• and
• analyze at least the first and second comparison scores to determine if one of the first, second and third detected events is likely due to overdetection.

An implantable medical device (IMD) comprising a plurality of electrodes coupled to operational circuitry configured to perform cardiac signal analysis, the IMD including a canister having the operational circuitry and at least one electrode associated therewith, the operational circuitry being configured to:

• detect a plurality of detected events by comparison of a cardiac signal from the plurality of electrodes to a threshold defined by a detection profile and declaring a detected event having a signal waveform when the threshold is crossed;
• calculate one or more correlation scores for the plurality of detected events;
• use the correlation scores in a first analysis to determine whether overdetection is occurring;
• and
• use the correlation scores in a second analysis to determine whether an arrhythmia is occurring.