Cardiac event sensing and pacing after delivery of an electrical stimulation pulse

Patent metadata

Field	Value
Publication number	US-2016106989-A1
Application number	US-201414519251-A
Country	US
Kind code	A1
Filing date	Oct 21, 2014
Priority date	Oct 21, 2014
Publication date	Apr 21, 2016
Grant date	—

Abstract

A medical device is configured to deliver a shock to a patient's heart via electrodes coupled to the medical device and set an escape interval timer to start running an escape interval after delivering the electrical shock. A sensing module of the medical device is configured to sense a cardiac event in response to a cardiac electrical signal received by the medical device crossing a sensing threshold. The medical device determines if the cardiac event meets reset criteria and allows the escape interval timer to continue running the escape interval if the cardiac event does not meet the reset criteria.

First claim

1 . A method performed by a medical device, comprising:
delivering an electrical shock to a heart of a patient; setting an escape interval timer to start running an escape interval after delivering the electrical shock; sensing a cardiac event in response to a cardiac electrical signal received by the medical device crossing a sensing threshold during the escape interval; determining if the cardiac event meets reset criteria; allowing the escape interval timer to continue running the escape interval if the cardiac event does not meet the reset criteria; and resetting the escape interval timer if the cardiac event meets the reset criteria.

2 . The method of claim 1 , further comprising:
delivering a post-shock pacing pulse in response to the escape interval expiring; restarting the escape interval timer to run a pacing escape interval in response to the post-shock pacing pulse; and automatically adjusting a cardiac event sensing threshold according to a post-pace decay sequence controlled by a first set of sensing control parameters in response to the post-shock pacing pulse.

3 . The method of claim 2 , further comprising starting a post-sense decay sequence in response to sensing a cardiac event during the pacing escape interval, the post-sense decay sequence controlled by a second set of sensing control parameters different than the first set of sensing control parameters so that the post-pace decay sequence is different than the post-sense decay sequence.

4 . The method of claim 3 , further comprising:
setting a post-shock pacing period after delivering the electrical shock; resuming a pre-shock decay sequence for automatically adjusting the cardiac event sensing threshold upon expiration of the post-shock pacing period, the pre-shock decay sequence comprising at least a drop time interval for controlling a decrease of the cardiac event sensing threshold from a starting threshold amplitude to an intermediate sensing threshold amplitude, wherein the post-sense decay sequence comprises a post-sense drop time interval that is less than the pre-shock drop time interval.

5 . The method of claim 4 , further comprising:
setting a post-shock blanking interval during which cardiac event sensing by the medical device is disabled; setting a post-shock signal analysis segment following the blanking interval during which cardiac event sensing by the medical device is enabled but pacing pulse delivery is disabled; and starting the post-shock pacing period upon expiration of the post-shock signal analysis segment, the pacing escape interval started during the post-shock pacing period.

6 . The method of claim 2 , further comprising:
determining a pre-shock cardiac event amplitude; and setting an initial amplitude of the cardiac sensing threshold during the post-pace decay sequence based on the pre-shock cardiac event amplitude.

7 . The method of claim 6 , wherein determining the pre-shock cardiac event amplitude comprises producing a cardiac event template during a known pre-shock cardiac rhythm and determining a maximum peak cardiac event amplitude from the template.

8 . The method of claim 2 , further comprising:
determining a pre-shock R-wave amplitude; determining a pre-shock P-wave amplitude; and selecting an initial amplitude of the cardiac sensing threshold during the post-pace decay sequence based on an analysis of both of the pre-shock R-wave amplitude and the pre-shock P-wave amplitude.

9 . The method of claim 1 , wherein determining if the cardiac event meets the reset criteria comprises:
establishing a reset amplitude; comparing a peak amplitude of the sensed cardiac event to the reset amplitude; and determining that the reset criteria are met if the peak amplitude exceeds the reset amplitude.

10 . The method of claim 9 , wherein establishing the reset amplitude comprises:
determining a pre-shock cardiac event amplitude; and setting the reset amplitude based on the pre-shock cardiac event amplitude.

11 . The method of claim 1 , wherein determining if the cardiac event meets the reset criteria comprises:
establishing a reset interval; determining a cardiac event interval from the sensed cardiac event to a preceding cardiac event; comparing the cardiac event interval to the reset interval; and determining that the reset criteria are met if the cardiac event interval is less than the reset interval.

12 . The method of claim 11 , wherein establishing the reset interval comprises setting the reset interval based on a tachyarrhythmia detection interval.

13 . The method of claim 1 , further comprising:
delivering a post-shock pacing pulse if the escape interval expires; resetting the escape interval timer to a pacing escape interval in response to the post-shock pacing pulse; wherein resetting the escape interval timer in response to the cardiac event meeting the reset criteria comprises setting the escape interval timer to a hysteresis interval that is longer than the pacing escape interval.

14 . The method of claim 1 , further comprising:
sensing a first plurality of cardiac events on a first cardiac electrical signal sensing channel of the medical device; sensing a second plurality of cardiac events on a second cardiac electrical signal sensing channel of the medical device; comparing each of the first plurality of cardiac events and each of the second plurality of cardiac events to the reset criteria; resetting the escape interval timer each time one of the first plurality of cardiac events meets the reset criteria and each time one of the second plurality of cardiac events meets the reset criteria, wherein resetting the escape interval timer comprises resetting the escape interval timer to a hysteresis escape interval; and delivering a post-shock pacing pulse if the hysteresis escape interval expires without at least one of the first plurality of cardiac events and the second plurality of cardiac events meeting the reset criteria during the hysteresis escape interval.

15 . The method of claim 14 , further comprising:
starting a post-sense decay sequence for automatically adjusting a first cardiac event sensing threshold of the first cardiac electrical signal sensing channel in response to every one of the first plurality of cardiac events; and starting the post-sense decay sequence for automatically adjusting a second cardiac event sensing threshold of the second cardiac electrical signal sensing channel in response to every one of the second plurality of cardiac events.

16 . A medical device, comprising:
a therapy delivery module configured to deliver an electrical shock to a patient's heart via electrodes coupled to the medical device; a sensing module configured to receive a cardiac electrical signal, sense a cardiac event in response to the cardiac electrical signal crossing a sensing threshold, and produce a cardiac event sense signal in response to sensing the cardiac event; and a control module coupled to the sensing module and the therapy delivery module and configured to:
set an escape interval timer to start running an escape interval after the therapy delivery module delivers the electrical shock,
in response to receiving a cardiac event sense signal from the sensing module during the escape interval timer, determine if the sensed cardiac event meets reset criteria,
allow the escape interval timer to continue running the escape interval if the cardiac event does not meet the reset criteria, and
reset the escape interval timer in response to the sensed cardiac event meeting the reset criteria.

Assignees

• Medtronic Inc

Inventors

• Stadler Robert W
• Cao Jian

Classifications

• A61N1/37252 Primary

  Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data · CPC title

• A61N1/39622

  Pacing therapy · CPC title

• A61N1/365

  controlled by a physiological parameter, e.g. heart potential {(evoked response A61N1/371)} · CPC title

• A61N1/3622

  comprising two or more electrodes co-operating with different heart regions · CPC title

• A61N1/368

  comprising more than one electrode co-operating with different heart regions {(A61N1/3622, A61N1/3627 take precedence)} · CPC title