Reduction or elimination of pace polarization effects
The present disclosure relates to cardiac evoked response detection and, more particularly, reducing polarization effects in order to detect an evoked response following delivery of a stimulation pulse. An implantable medical device (IMD) is configured to deliver a ventricular pacing pulse. A signal is sensed in response to the ventricular pacing stimulus. A window is placed over the sensed signal to obtain a set of data from the signal after a paced event. The set of data extracted from the sensed signal comprises a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude. Responsive to processing the extracted data, the window is delayed to avoid polarization effects. A determination is then made as to whether the ventricular pacing stimulus is capturing the paced ventricle in response to determining whether the maximum time is greater than the minimum time.
1. An apparatus for reducing polarization effects after delivering pacing stimuli to ventricle, comprising:
delivering means for delivering pacing stimuli to a ventricle;
sensing means for sensing a signal in response to the ventricular pacing stimulus;
processing means for setting a window to obtain a set of data from the signal after a paced event, the set of data comprising a maximum amplitude, a maximum time associated with the maximum amplitude, a minimum amplitude, and a minimum time associated with the minimum amplitude;
processing means for delaying the window to avoid polarization effects;
obtaining the maximum time and the maximum amplitude within the delayed window of the signal; and
processing means for determining whether the ventricular pacing stimulus is capturing the paced ventricle in response to determining whether the maximum time is greater than the minimum time.
2. The apparatus of claim 1 wherein setting the window involves an equation such that:
window= a+b *( R−R ) where a and b are constants, a value of “ a ” ranging from 0-70 milliseconds (ms) and a value of “ b ” ranging from 0.1-0.5.
3. The apparatus of claim 1 wherein the delayed window begins about 30-100 ms after the paced event.
4. The apparatus of claim 1 wherein elimination of polarization effects occurs without using a digital filter on the sensed signal.
5. The apparatus of claim 4 wherein a same electrode is used to deliver pacing stimuli and sense the signal.
6. The apparatus of claim 3 further comprising:
tracking a set of R-R intervals;
determining a median of the set of R-R intervals; and
setting the window responsive to the determining the median of the set of R-R intervals.
7. The apparatus of claim 3 wherein the window is configured for fast ventricular rates, a beginning of the window being set at 100 ms after the delivery of the pacing stimuli.
8. The apparatus of claim 1 further comprising:
switching sensing the signal to from one electrode to a neighboring electrode.
9. An apparatus for reducing polarization effects after delivering pacing stimuli to ventricle, comprising:
delivering means for delivering pacing stimuli to a ventricle;
sensing means for sensing a signal in response to the ventricular pacing stimulus;
processing means for setting a non-delayed window to obtain a set of data from the signal after a paced event, the set of data comprising a minimum amplitude, and a minimum time associated with the minimum amplitude;
processing means for setting a delayed window to avoid polarization effects to obtain another set of data comprising a maximum amplitude, and a maximum time associated with the maximum amplitude, the maximum time and the maximum amplitude located within the delayed window of the signal; and
processing means for determining whether the ventricular pacing stimulus is capturing the paced ventricle in response to determining whether the maximum time is greater than the minimum time.
10. The apparatus of claim 9 wherein setting the delayed window involves an equation such that:
delayed window= a+b *( R−R ) where a and b are constants, a value of “ a ” ranging from 0-70 milliseconds (ms) and a value of “ b ” ranging from 0.1-0.5.
11. The apparatus of claim 9 wherein the delayed window begins about 30-100 ms after the paced event.
12. The apparatus of claim 9 wherein elimination of polarization effects occurs without using a digital filter on the sensed signal.
13. The apparatus of claim 12 wherein a same electrode is used to deliver pacing stimuli and sense the signal.
14. The apparatus of claim 11 further comprising:
tracking a set of R-R intervals;
determining a median of the set of R-R intervals; and
setting the window responsive to the determining the median of the set of R-R intervals.