Multi-threshold sensing of cardiac electrical signals in an implantable medical device

Patent metadata

Field	Value
Publication number	US-10799710-B2
Application number	US-201715790255-A
Country	US
Kind code	B2
Filing date	Oct 23, 2017
Priority date	Oct 23, 2017
Publication date	Oct 13, 2020
Grant date	Oct 13, 2020

Abstract

An implantable medical device system is configured to sense cardiac events in response to a cardiac electrical signal crossing a cardiac event sensing threshold. A control circuit is configured to determine a drop time interval based on a heart rate and control a sensing circuit to hold the cardiac event sensing threshold at a threshold value during the drop time interval.

First claim

The invention claimed is:

1. A system comprising an implantable medical device for sensing cardiac electrical events, the system comprising:
a sensing circuit configured to receive a cardiac electrical signal from a patient's heart and sense a cardiac event attendant to a myocardial depolarization in response to the cardiac electrical signal crossing a cardiac event sensing threshold;
a therapy delivery circuit configured to deliver an electrical stimulation therapy to a patient's heart; and
a control circuit configured to:
determine a drop time interval based on a heart rate;
detect expiration of the drop time interval;
control the sensing circuit to adjust the cardiac event sensing threshold from a first threshold value to a minimum threshold value in response to detection of the expiration of the drop time interval;
determine a need for an electrical stimulation therapy based on at least a rate of cardiac events sensed by the sensing circuit; and
control the therapy delivery circuit to deliver an electrical stimulation pulse in response to determining the need for the electrical stimulation therapy.

2. The system of claim 1 , wherein the control circuit is configured to:
control the therapy delivery circuit to deliver the electrical stimulation pulse at a pacing interval following a preceding electrical stimulation pulse delivered by the therapy delivery circuit; and
determine the drop time interval based on the heart rate by determining a percentage of the pacing interval.

3. The system of claim 2 , wherein the control circuit is further configured to:
set the determined drop time interval following delivery of the electrical stimulation pulse;
set a second pacing interval following delivery of the electrical stimulation pulse;
set a fixed drop time interval different than the determined drop time interval in response to the sensing circuit sensing a cardiac event during the second pacing interval based on the cardiac electrical signal crossing the cardiac event sensing threshold during the second pacing interval;
determine a second threshold value based on a peak amplitude of the cardiac event sensed during the second pacing interval; and
hold the cardiac event sensing threshold at the second threshold value during the fixed drop time interval.

4. The system of claim 1 , wherein the control circuit is configured to determine the drop time interval by:
determining a cardiac event interval between two cardiac events consecutively sensed by the sensing circuit; and
setting the drop time interval to a percentage of the cardiac event interval.

5. The system of claim 1 , wherein the control circuit is configured to:
establish a maximum sensing threshold value based on a programmed sensitivity setting; and
set the first threshold value to a percentage of the maximum sensing threshold value.

6. The system of claim 1 , wherein the control circuit is configured to:
set the cardiac event sensing threshold to a starting threshold value;
hold the cardiac event sensing threshold at the starting threshold value during a delay interval;
adjust the cardiac event sensing threshold from the starting threshold value to the first threshold value upon expiration of the delay interval; and
adjust the cardiac event sensing threshold from the first threshold value to a second threshold value upon expiration of the drop time interval.

7. The system of claim 1 , wherein the control circuit is configured to:
determine a starting threshold value of the cardiac event sensing threshold;
compare the determined drop time interval to a sense delay interval;
in response to the drop time interval being equal to or less than the sense delay interval, holding the cardiac event sensing threshold at the first threshold value equal to the starting threshold value for the sense delay interval; and
control the sensing circuit to adjust the cardiac event sensing threshold from the starting threshold value to a second threshold value upon expiration of the sense delay interval in response to the cardiac electrical signal not crossing the starting threshold value during the sensed delay interval.

8. The system of claim 1 , wherein the control circuit is configured to:
determine a starting threshold value of the cardiac event sensing threshold;
compare the determined drop time interval to a sense delay interval;
in response to the drop time interval being equal to or less than the sense delay interval, holding the cardiac event sensing threshold at the first threshold value equal to the starting threshold value for the drop time interval; and
control the sensing circuit to adjust the cardiac event sensing threshold from the starting threshold value to a second threshold value upon expiration of the drop time interval in response to the cardiac electrical signal not crossing the starting threshold value during the drop time interval.

9. The system of claim 1 , wherein the control circuit is further configured to:
compare the drop time interval determined based on the heart rate to a maximum drop time limit; and
set the drop time interval to a lowest one of the maximum drop time limit and the drop time interval determined based on the heart rate.

10. The system of claim 1 , wherein the control circuit is further configured to:
determine a need for an electrical stimulation therapy by determining one of a need for a first electrical stimulation therapy or a need for a second electrical stimulation therapy, the second electrical stimulation therapy different than the first electrical stimulation therapy; and
determine the drop time interval based on the heart rate by:
determine the drop time interval as one of a first percentage of a first pacing interval of the first electrical stimulation therapy in response to determining the need for the first electrical stimulation therapy exists or a second percentage of a second pacing interval of the second electrical stimulation therapy in response to determining the need for the second electrical stimulation therapy;
compare the determined drop time interval to a first minimum drop time interval in response to determining the need for the first electrical stimulation therapy;
compare the determined drop time interval to a second minimum drop time interval different than the first minimum drop time interval in response to determining the need for the second electrical stimulation therapy;
set the drop time interval to a greater one of the determined drop time interval and the first minimum drop time interval in response to determining the need for the first electrical stimulation therapy; and
set the drop time interval to a greater one of the determined drop time interval and the second minimum drop time interval in response to determining the need for the second electrical stimulation therapy.

11. The system of claim 1 , wherein the implantable medical device is an implantable cardioverter defibrillator and the sensing circuit is configured to receive the cardiac electrical signal via at least one electrode are carried by an extra-cardiovascular lead coupleable to the implantable cardioverter defibrillator.

12. A method comprising:
receiving a cardiac electrical signal from a patient's heart;
sensing a cardiac event attendant to a myocardial depolarization in response to the cardiac electrical signal crossing a cardiac event sensing threshold;
determining a drop time interval based on a heart rate;
detecting expiration of the drop time interval;
adjusting the cardiac event sensing threshold from a first threshold value to a minimum threshold value upon detecting expiration of the drop time interval;
determinin

Assignees

• Medtronic Inc

Inventors

• Cao Jian
• Arne Gerald P
• Ebeling Timothy A
• Grinberg Yanina
• Heinks Michael W
• Solheim Paul R
• Zhang Xusheng

Classifications

• A61N1/3622 Primary

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

• A61B5/361

  Detecting fibrillation · CPC title

• A61B5/352

  Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval · CPC title

• A61N1/39622

  Pacing therapy · CPC title

• A61N1/3987

  characterised by the timing or triggering of the shock · CPC title