U.S. patent application number 15/951982 was filed with the patent office on 2018-08-16 for systems and methods for rate responsive pacing with a leadless cardiac pacemaker.
This patent application is currently assigned to CARDIAC PACEMAKERS, INC.. The applicant listed for this patent is CARDIAC PACEMAKERS, INC.. Invention is credited to Michael J. Kane, Keith R. Maile, Jeffrey E. Stahmann.
Application Number | 20180229043 15/951982 |
Document ID | / |
Family ID | 54545448 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180229043 |
Kind Code |
A1 |
Kane; Michael J. ; et
al. |
August 16, 2018 |
SYSTEMS AND METHODS FOR RATE RESPONSIVE PACING WITH A LEADLESS
CARDIAC PACEMAKER
Abstract
Systems and methods for providing rate responsive pacing therapy
to a heart of a patient. One example method for providing rate
responsive pacing therapy includes sensing cardiac electrical data
with a leadless cardiac pacemaker (LCP) that is implanted within or
proximate the heart. From this location, the LCP may provide pacing
therapy to the heart based at least in part on the sensed cardiac
electrical data. An implantable medical device located remotely
from the heart may sense patient activity, and may wirelessly
communicate patient activity data from the implantable medical
device to the LCP, sometimes using conducted communication. The LCP
may be then determine an adjustment to the provided pacing therapy
(e.g. adjust the pacing rate) based at least in part on the
received patient activity data signal.
Inventors: |
Kane; Michael J.;
(Roseville, MN) ; Stahmann; Jeffrey E.; (Ramsey,
MN) ; Maile; Keith R.; (New Brighton, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CARDIAC PACEMAKERS, INC. |
St. Paul |
MN |
US |
|
|
Assignee: |
CARDIAC PACEMAKERS, INC.
St. Paul
MN
|
Family ID: |
54545448 |
Appl. No.: |
15/951982 |
Filed: |
April 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14736907 |
Jun 11, 2015 |
9962550 |
|
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15951982 |
|
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62011249 |
Jun 12, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/36542 20130101;
A61N 1/3684 20130101; A61N 1/36585 20130101; A61N 1/0563 20130101;
A61N 1/37288 20130101; A61N 1/3756 20130101; A61N 1/36521
20130101 |
International
Class: |
A61N 1/365 20060101
A61N001/365; A61N 1/375 20060101 A61N001/375 |
Claims
1. A method for providing rate responsive pacing therapy to a heart
of a patient, the method comprising: sensing cardiac electrical
data with a leadless cardiac pacemaker (LCP) implanted within and
directly coupled to a wall of the heart of the patient such that
the LCP moves with the wall of the heart of the patient; providing
pacing therapy to the heart of the patient with the LCP based at
least in part on the sensed cardiac electrical data, the pacing
therapy including a pacing rate; sensing patient activity of the
patient using an accelerometer that is housed in a remote device
that is separate from the LCP and not directly coupled to the heart
of the patient, and determining a patient activity data signal
based at least in part upon the patient activity sensed by the
accelerometer; wirelessly communicating the patient activity data
signal from the remote device to the LCP; and the LCP adjusting the
pacing rate of the provided pacing therapy based at least in part
on the received patient activity data signal.
2. The method of claim 1, wherein the remote device is a
subcutaneous implantable device with a housing implanted in a
pocket under the skin of the patient.
3. The method of claim 1, wherein the patient activity data signal
is wirelessly communicated from the remote device to the LCP by
conducted communication.
4. The method of claim 1, wherein the patient activity data signal
is wirelessly communicated from the remote device to the LCP using
one or more of an electrical signal, a radiofrequency signal and an
acoustic signal.
5. The method of claim 1, wherein the remote device comprises an
implantable cardioverter-defibrillator (ICD).
6. The method of claim 1, wherein the LCP adjusts the pacing rate
of the provided pacing therapy based at least in part on both the
received patient activity data signal and a respiration rate of the
patient that is determined at least in part using the remote
device.
7. The method of claim 1, wherein the patient activity data signal
comprises accelerometer data.
8. The method of claim 1, wherein the patient activity data signal
is based, at least in part, on a respiration signal.
9. The method of claim 8, wherein the respiration signal is based,
at least in part, on a measure related to an impedance across at
least a portion of a lung of the patient.
10. The method of claim 8, further comprising determining a measure
related to a respiratory rate of the patient based, at least in
part, on a difference in an amplitude of the patient activity data
signal communicated by the remote device and an amplitude of the
patient activity data signal received at the LCP, and wherein the
LCP adjusts the pacing rate of the provided pacing therapy based at
least in part on the measure related to the respiratory rate of the
patient.
11. The method of claim 1, wherein the LCP adjusts the pacing rate
of the provided pacing therapy based at least in part on a sensed
heart rate of the patient.
12. The method of claim 11, wherein sensed heart rate of the
patient is sensed by one or more exposed electrodes of the LCP.
13. An implantable medical device system for providing adjustable
rate pacing therapy to a heart of a patient, the system comprising:
a leadless cardiac pacemaker (LCP) implantable within and directly
coupled to a wall of the heart of the patient such that the LCP
moves with the wall of the heart of the patient, wherein the LCP is
configured to: sense cardiac electrical data; provide pacing
therapy to the heart of the patient based at least in part on the
sensed cardiac electrical data, the pacing therapy including a
pacing rate; a remote device including an accelerometer, the remote
device is free from a securement configured for transvenous
delivery and securement of the remote device directly to an
internal wall of the heart of the patient, the remote device is
configured to: sensing patient activity of the patient from a
location remote from the heart of the patient using the
accelerometer of the remote device; determining a patient activity
data signal based at least in part upon the patient activity sensed
by the accelerometer; wirelessly communicating the patient activity
data signal from the remote device to the LCP; and wherein the LCP
is configured to adjusting the pacing rate of the provided pacing
therapy based at least in part on the received patient activity
data signal.
14. The system of claim 13, wherein the remote device is a
subcutaneous implantable device implanted in a pocket under the
skin of the patient.
15. The system of claim 13, wherein the patient activity data
signal is wirelessly communicated from the remote device to the LCP
by conducted communication.
16. The system of claim 13, wherein the patient activity data
signal is wirelessly communicated from the remote device to the LCP
using one or more of an electrical signal, a radiofrequency signal
and an acoustic signal.
17. The system of claim 13, wherein the LCP is configured to
adjusting the pacing rate of the provided pacing therapy based at
least in part on both the received patient activity data signal and
a respiration rate of the patient that is determined at least in
part using the remote device.
18. An implantable medical device system for providing adjustable
rate pacing therapy to a heart of a patient, the system comprising:
a leadless cardiac pacemaker (LCP) implantable within and directly
coupled to a wall of the heart of the patient such that the LCP
moves with the wall of the heart of the patient; an implantable
medical device that is free from a housing and a securement that
are configured for transvenous delivery and securement of the
implantable medical device directly to an internal wall of the
heart of the patient, but rather is configured to be implantable at
a location remote from and not directly coupled to the heart of the
patient, wherein the implantable medical device comprises an
accelerometer; wherein the implantable medical device is configured
to generate patient activity data based at least in part on an
output of the accelerometer, and is further configured to
wirelessly communicate the patient activity data to the LCP; and
wherein the LCP is configured to: provide rate responsive pacing
therapy to the heart of the patient; and adjust a rate of the rate
responsive pacing therapy based at least in part on the patient
activity data received from the implantable medical device.
19. The implantable medical device system of claim 18, wherein the
patient activity data is wirelessly communicated from the
implantable medical device to the LCP by conducted
communication.
20. The implantable medical device system of claim 18, wherein the
patient activity data is wirelessly communicated from the
implantable medical device to the LCP using one or more of an
electrical signal, a radiofrequency signal and an acoustic signal.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 14/736,907, filed Jun. 11, 2015, and entitled
SYSTEMS AND METHODS FOR RATE RESPONSIVE PACING WITH A LEADLESS
CARDIAC PACEMAKER, which claims the benefit of U.S. Provisional
Application No. 62/011,249, filed Jun. 12, 2014, both of which are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure generally relates to systems,
devices, and methods for delivering pacing pulses to a heart and,
more specifically to systems, devices, and methods for performing
rate responsive pacing with a Leadless Cardiac Pacemaker (LCP).
BACKGROUND
[0003] Pacing instruments can be used to treat patients suffering
from various heart conditions that may result in a reduced ability
of the heart to deliver sufficient amounts of blood to a patient's
body. These heart conditions may lead to rapid, irregular, and/or
inefficient heart contractions. To help alleviate some of these
conditions, various devices (e.g., pacemakers, defibrillators,
etc.) can be implanted in a patient's body. Such devices may
monitor and provide electrical stimulation to the heart to help the
heart operate in a more normal, efficient and/or safe manner.
[0004] Pacing the heart at a fixed rate is limiting because it does
not allow the heart rate to increase with increased metabolic
demand. If the heart is paced at a constant rate, as for example by
a VVI pacemaker, limitations are imposed upon the patient with
respect to lifestyle and activities. It is to overcome these
limitations and improve the quality of life of such patients that
rate-responsive pacemakers have been developed.
[0005] Rate responsive capable pacemakers often include one or more
sensors to gain insight into the current metabolic demand of the
patient, and adjust the pacing rate accordingly. This can be
accomplished relatively easily in a traditional pacemaker that has
a pacemaker "can" implanted in a pocket under the skin, with leads
extending into the heart. The pacemaker "can" is often sufficiently
large to house a fairly high capacity battery and may have
significant processing power. Also, the pacemaker may have access
to signals and/or sensors that are located both inside the heart
via the leads and outside of the heart via the "can".
[0006] Leadless Cardiac Pacemakers (LCP), which are implanted in or
proximate to the heart, present a unique challenge to rate
responsive pacing. For example, because of constant movement of the
LCP with the heart, accelerometer data obtained from a local
accelerometer within the LCP housing may have significant noise,
which can require significant processing power to isolate movement
that is due to the patient's activity versus movement cause by the
beating of the heart itself. In another example, because of its
location and size, it can be difficult for an LCP to derive a
reliable measure of respiration rate and/or tidal volume of the
patient, which can be an indicator of patient activity. These are
just some of the challenges in providing effective rate responsive
pacing in a LCP. What would be desirable are improved systems and
methods for providing rate responsive pacing using a Leadless
Cardiac Pacemaker (LCP).
SUMMARY
[0007] The present disclosure relates generally to systems and
methods for coordinating treatment of abnormal heart activity using
multiple implanted devices within a patient. It is contemplated
that the multiple implanted devices may include, for example,
pacemakers, defibrillators, diagnostic devices, sensor devices,
and/or any other suitable implantable devices, as desired. More
specifically, the present disclosure relates to systems, devices,
and methods for providing rate responsive pacing with a Leadless
Cardiac Pacemaker (LCP).
[0008] An illustrative method for providing rate responsive pacing
therapy to a heart of a patient using a Leadless Cardiac Pacemaker
(LCP) may include: sensing cardiac electrical data with an LCP
implanted within or proximate the heart of the patient; providing
pacing therapy to the heart of the patient with the LCP based at
least in part on the sensed cardiac electrical data; sensing
patient activity with an implanted medical device from a location
that is spaced from the heart of the patient; wirelessly
communicating a patient activity data signal from the implantable
medical device to the LCP; and having the LCP determine an
adjustment to the provided pacing therapy based at least in part on
the received patient activity data signal, and adjusting the pacing
therapy provided by the LCP. The adjustment may include an
adjustment to the pacing rate so that the pacing rate changes with
the activity level of the patient. In some cases, the patient
activity data signal is based, at least in part, on an output of an
accelerometer in the implantable medical device. It is also
contemplated that respiration information, such as respiration rate
and tidal volume, may be derived from the patient activity data
signal (e.g. a change in amplitude of the patient activity data
signal over time).
[0009] An illustrative implantable medical device system may
include a leadless cardiac pacemaker (LCP) implantable within or
proximate the heart of the patient. The LCP may be configured to
sense cardiac electrical data and provide pacing therapy to the
heart of the patient based at least in part on the sensed cardiac
electrical data. The illustrative implantable medical device system
may also include an implantable medical device implanted in a
location that is spaced from the heart of the patient. The
implantable medical device may be configured to sense patient
activity and wirelessly communicate a patient activity data signal
to the LCP. The LCP may then be configured to determine an
adjustment to the provided pacing therapy based at least in part on
the received patient activity data signal and adjust the pacing
therapy. The adjustment may include an adjustment to the pacing
rate so that the pacing rate changes with the activity level of the
patient.
[0010] In another example, a method for providing rate responsive
pacing therapy to a heart of a patient may include: sensing cardiac
electrical data with a leadless cardiac pacemaker (LCP) implanted
within or proximate the heart of the patient; providing pacing
therapy to the heart of the patient with the LCP based at least in
part on the sensed cardiac electrical data; sensing patient
activity with an implanted medical device from a location that is
spaced from the heart of the patient; wirelessly communicating a
patient activity data signal from the implantable medical device to
the LCP; and the LCP determining an adjustment to the provided
pacing therapy based at least in part on the received patient
activity data signal, and adjusting the pacing therapy provided
with the LCP.
[0011] Alternatively or additionally to the example above, in
another example, the patient activity data signal is based, at
least in part, on an output of an accelerometer of the implantable
medical device.
[0012] Alternatively or additionally to any of the examples above,
in another example, the LCP may determine the adjustment to the
provided pacing therapy based at least in part on both the output
of the accelerometer of the implantable medical device and a
respiration rate of the patient that is determined at least in part
by the implantable medical device.
[0013] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal comprises
accelerometer data.
[0014] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal is based, at
least in part, on a respiration signal.
[0015] Alternatively or additionally to any of the examples above,
in another example, the respiration signal is based, at least in
part, on a measure related to an impedance across at least a
portion of a lung of the patient.
[0016] Alternatively or additionally to any of the examples above,
in another example, the respiration signal is based, at least in
part, on an output of transthoracic impedance sensor of the
implantable medical device.
[0017] Alternatively or additionally to any of the examples above,
in another example, the method may further comprise determining a
measure related to a respiratory rate of the patient based, at
least in part, on a difference in an amplitude of the patient
activity data signal communicated by the implantable medical device
and an amplitude of the patient activity data signal that is
received by the LCP.
[0018] Alternatively or additionally to any of the examples above,
in another example, the method may further comprise determining a
tidal volume parameter based, at least in part, on a difference in
an amplitude of the patient activity data signal communicated by
the implantable medical device and an amplitude of the patient
activity data signal that is received by the LCP.
[0019] Alternatively or additionally to any of the examples above,
in another example, the method may further comprise determining the
measure related to the impedance across at least a portion of a
lung of the patent by: delivering a voltage pulse with the
implantable medical device; measuring an amplitude of a delivered
current of the delivered voltage pulse with the implantable medical
device; communicating the measured amplitude of the delivered
current from the implantable medical device to the LCP; measuring
an amplitude of the delivered voltage pulse with the LCP;
determining at the LCP the measure related to the impedance across
the lungs of the patient based, at least in part, on the measured
amplitude of the delivered voltage pulse and the measured amplitude
of the delivered current communicated by the implantable medical
device to the LCP.
[0020] Alternatively or additionally to any of the examples above,
in another example, the method may further comprise determining a
tidal volume parameter based on a difference in an amplitude of the
patient activity data signal communicated from the implantable
medical device and an amplitude of the patient activity data signal
received by the LCP; determining a minute ventilation parameter
based on a determined respiratory rate and the determined tidal
volume parameter; and the LCP determining the adjustment to the
provided pacing therapy based at least in part on both the received
patient activity data signal and the determined minute
ventilation.
[0021] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal may comprise
one or more of an electrical signal, a radiofrequency signal and an
acoustic signal.
[0022] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal is based, at
least in part, on a sensed heart rate of the patient.
[0023] In another example, a method for providing rate responsive
pacing therapy to a heart of a patient comprises: sensing cardiac
electrical data with a leadless cardiac pacemaker (LCP) implanted
within or proximate the heart of the patient; providing pacing
therapy to the heart of the patient with the LCP based at least in
part on the sensed cardiac electrical data; wirelessly
communicating signals from the LCP to an implantable medical device
implanted remote from the heart of the patient; and with the
implantable medical device, determining one or more physiological
parameters based at least in part on the wirelessly communicated
signals.
[0024] Alternatively or additionally to the example above, in
another example, the method may further comprise sensing patient
activity with the implantable medical device.
[0025] Alternatively or additionally to any of the examples above,
in another example, the method may further comprise communicating a
patient activity data signal from the implantable medical device to
the LCP; and with the LCP, adjusting the provided pacing therapy
based at least in part on the received patient activity data
signal.
[0026] Alternatively or additionally to any of the examples above,
in another example, the method may further comprise with the
implantable medical device, determining a measure related to a
transthoracic impedance based on the received wireless
communication signals from the LCP.
[0027] Alternatively or additionally to any of the examples above,
in another example, determining the measure related to the
transthoracic impedance based on the received wireless
communication signals from the LCP may comprise: delivering a
voltage pulse with the LCP; measuring an amplitude of a delivered
current from the delivered voltage pulse with the LCP, wherein the
received wireless communication signals comprise the measured
amplitude of the delivered current; measuring an amplitude of the
delivered voltage pulse with the implantable medical device; and
determining a measure related to the transthoracic impedance with
the implantable medical device based on the measured amplitude of
the delivered voltage pulse and the received measured amplitude of
the delivered current.
[0028] Alternatively or additionally to any of the examples above,
in another example, the one or more physiological parameters may
comprise one or more of respiratory rate, tidal volume and heart
rate.
[0029] Alternatively or additionally to any of the examples above,
in another example, determining one or more physiological
parameters based on the wirelessly communicated signals may
comprise determining a difference in an amplitude of the wirelessly
communicated signals delivered by the LCP and an amplitude of the
wirelessly communicated signals sensed by the implantable medical
device.
[0030] Alternatively or additionally to any of the examples above,
in another example, the wirelessly communicated signals comprise
pacing pulses.
[0031] Alternatively or additionally to any of the examples above,
in another example, the wirelessly communicated signals comprise
sub-threshold electrical pulses.
[0032] Alternatively or additionally to any of the examples above,
in another example, the wirelessly communicated signals comprise
pacing pulses if a rate of delivered pacing pulses by the LCP
exceeds a predetermined threshold, and wherein the wirelessly
communicated signals comprise sub-threshold electrical pulses if
the rate of delivered pacing pulses by the LCP is equal to or less
than a predetermined threshold.
[0033] Alternatively or additionally to any of the examples above,
in another example, the method may further comprise communicating
one or more of the one or more determined physiological parameters
from the implantable medical device to the LCP; and with the LCP,
adjusting the provided pacing therapy based at least in part on the
received determined physiological parameters.
[0034] Alternatively or additionally to any of the examples above,
in another example, the method further comprising sensing a patient
activity level using the implantable medical device; and
communicating one or more parameters from the implantable medical
device to the LCP, the one or more parameters based at least in
part on the one or more determined physiological parameters and the
patient activity level; and with the LCP, adjusting the provided
pacing therapy based at least in part on the received one or more
parameters.
[0035] Alternatively or additionally to any of the examples above,
in another example, the one or more parameters includes a rate
responsive heart rate.
[0036] In another example, an implantable medical device system for
providing adjustable rate pacing therapy to a heart of a patient
comprises: a leadless cardiac pacemaker (LCP) implantable within or
proximate the heart of the patient; and an implantable medical
device, wherein the implantable medical device: comprises an
accelerometer; implantable remote from the heart of the patient;
and is wirelessly communicatively coupled to the LCP; wherein the
implantable medical device is configured to generate patient
activity data based at least in part on an output of the
accelerometer, and is further configured to wirelessly communicate
the patient activity data to the LCP; and wherein the LCP is
configured to: provide rate responsive pacing therapy to the heart
of the patient; and adjust the rate of the rate responsive pacing
therapy based at least in part on the patient activity data
received from the implantable medical device.
[0037] Alternatively or additionally to any of the examples above,
in another example, the implantable medical device is further
configured to: determine when a rate of change in a vertical
component of a three-axis accelerometer rises above a predetermined
threshold; and communicate the patient activity data to the LCP
when the rate of change in the vertical component of the three-axis
accelerometer rises above a predetermined threshold.
[0038] Alternatively or additionally to any of the examples above,
in another example, the patient activity data comprises a heart
rate.
[0039] Alternatively or additionally to any of the examples above,
in another example, the patient activity data comprises data from a
three-axis accelerometer, and wherein the LCP is further configured
to: determine when a rate of change in a vertical component of the
three-axis accelerometer rises above a predetermined threshold; and
adjust the rate of the rate-adjustable pacing therapy based on the
patient activity data received from the implantable medical
device.
[0040] In another example, an implantable medical device system for
providing adjustable rate pacing therapy to a heart of a patient
comprises: a leadless cardiac pacemaker (LCP) implantable within or
proximate the heart of the patient, wherein the LCP is configured
to: sense cardiac electrical data, and provide pacing therapy to
the heart of the patient based at least in part on the sensed
cardiac electrical data; and an implantable medical device
implanted in a location that is spaced from the heart of the
patient, wherein the implantable medical device is configured to:
sense patient activity, and wirelessly communicate a patient
activity data signal to the LCP; and wherein the LCP is configured
to determine an adjustment to the provided pacing therapy based at
least in part on the received patient activity data signal and
adjusts the pacing therapy.
[0041] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal is based, at
least in part, on an output of an accelerometer of the implantable
medical device.
[0042] Alternatively or additionally to any of the examples above,
in another example, the LCP is further configured to determine the
adjustment to the provided pacing therapy based at least in part on
both the output of the accelerometer of the implantable medical
device and a respiration rate of the patient that is determined at
least in part by the implantable medical device.
[0043] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal comprises
accelerometer data.
[0044] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal is based, at
least in part, on a respiration signal.
[0045] Alternatively or additionally to any of the examples above,
in another example, the respiration signal is based, at least in
part, on a measure related to an impedance across at least a
portion of a lung of the patient.
[0046] Alternatively or additionally to any of the examples above,
in another example, the respiration signal is based, at least in
part, on an output of transthoracic impedance sensor of the
implantable medical device.
[0047] Alternatively or additionally to any of the examples above,
in another example, the LCP is further configured to determine a
measure related to a respiratory rate of the patient based, at
least in part, on a difference in an amplitude of the patient
activity data signal communicated by the implantable medical device
and an amplitude of the patient activity data signal that is
received by the LCP.
[0048] Alternatively or additionally to any of the examples above,
in another example, the LCP is further configured to determine a
tidal volume parameter based, at least in part, on a difference in
an amplitude of the patient activity data signal communicated by
the implantable medical device and an amplitude of the patient
activity data signal that is received by the LCP.
[0049] Alternatively or additionally to any of the examples above,
in another example, the LCP is further configured to determine the
measure related to the impedance across at least a portion of a
lung of the patent by: receiving a measured amplitude of a
delivered current from the implantable medical device after the
implantable medical device delivers a voltage pulse and measures
the amplitude of the delivered current of the delivered voltage
pulse; measuring an amplitude of the delivered voltage pulse; and
determining the measure related to the impedance across the lungs
of the patient based, at least in part, on the measured amplitude
of the delivered voltage pulse and the measured amplitude of the
delivered current communicated by the implantable medical.
[0050] Alternatively or additionally to any of the examples above,
in another example, the LCP is further configured to: determine a
tidal volume parameter based on a difference in an amplitude of the
patient activity data signal communicated from the implantable
medical device and an amplitude of the patient activity data signal
received by the LCP; determine a minute ventilation parameter based
on a determined respiratory rate and the determined tidal volume
parameter; and determine the adjustment to the provided pacing
therapy based at least in part on both the received patient
activity data signal and the determined minute ventilation.
[0051] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal comprises one
or more of an electrical signal, a radiofrequency signal and an
acoustic signal.
[0052] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal is based, at
least in part, on a sensed heart rate of the patient.
[0053] Alternatively or additionally to any of the examples above,
in another example, the implantable medical device is further
configured to: determine when a rate of change in a vertical
component of a three-axis accelerometer rises above a predetermined
threshold connected to the implantable medical device; and
communicate the patient activity data to the LCP when the rate of
change in the vertical component of the three-axis accelerometer
rises above a predetermined threshold.
[0054] Alternatively or additionally to any of the examples above,
in another example, the patient activity data signal includes
three-axis accelerometer data, and the LCP is further configured
to: determine when a rate of change in a vertical component of the
three-axis accelerometer data rises above a predetermined
threshold; and adjust the rate of the rate-adjustable pacing
therapy when the rate of change in the vertical component of the
three-axis accelerometer data rises above a predetermined
threshold.
[0055] The above summary is not intended to describe each example
embodiment or every implementation of the present disclosure.
Advantages and attainments, together with a more complete
understanding of the disclosure, will become apparent and
appreciated by referring to the following description and claims
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] The disclosure may be more completely understood in
consideration of the following description of various illustrative
embodiments in connection with the accompanying drawings, in
which:
[0057] FIG. 1 illustrates an exemplary leadless cardiac pacemaker
(LCP) having electrodes, according to one example of the present
disclosure;
[0058] FIG. 2 illustrates a block diagram of an exemplary medical
device that may be used in accordance with various examples of the
present disclosure;
[0059] FIG. 3 illustrates a block diagram of another exemplary
medical device that may be used in accordance with various examples
of the present disclosure;
[0060] FIG. 4 is a schematic diagram of an exemplary medical system
that includes multiple leadless cardiac pacemakers (LCPs) and/or
other devices in communication with one another;
[0061] FIG. 5 is a diagram of an internal area of a chest cavity of
a patient showing multiple illustrative regions where one or more
devices may be implanted to help coordinate delivery of rate
responsive pacing using an LCP, in accordance with one example of
the present disclosure;
[0062] FIG. 6 is a flow diagram of an illustrative method that may
be implemented by a medical device or medical device system, such
as the illustrative medical devices and medical device systems
described with respect to FIGS. 1-3; and
[0063] FIG. 7 is a flow diagram of another illustrative method that
may be implemented by a medical device or medical device system,
such as the illustrative medical devices and medical device systems
described with respect to FIGS. 1-3.
[0064] While the disclosure is amenable to various modifications
and alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit aspects
of the disclosure to the particular illustrative embodiments
described. On the contrary, the intention is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the disclosure.
DESCRIPTION
[0065] The following description should be read with reference to
the drawings in which similar elements in different drawings are
numbered the same. The description and the drawings, which are not
necessarily to scale, depict illustrative embodiments and are not
intended to limit the scope of the disclosure.
[0066] A normal, healthy heart induces contraction by conducting
intrinsically generated electrical signals throughout the heart.
These intrinsic signals cause the muscle cells or tissue of the
heart to contract. This contraction forces blood out of and into
the heart, providing circulation of the blood throughout the rest
of the body. However, many patients suffer from cardiac conditions
that affect this contractility of their hearts. For example, some
hearts may develop diseased tissues that no longer generate or
conduct intrinsic electrical signals. Such patients may need a
medical device to deliver pacing pulses to their heart in order to
cause their heart to contract and pump blood.
[0067] FIGS. 1-3 generally depict implantable medical devices that
may be used for delivering pacing therapy to a heart of a patient.
More specifically, the devices depicts in FIGS. 1-3 may be used
alone or in various combinations to deliver rate responsive pacing
therapy to a heart of a patient. Rate responsive pacing therapy may
include pacing therapy where the rate of delivered pacing pulses
change over time. In some cases, the pacing rate may be based on
the current cardiovascular need of the patient, such as the
activity level of the patient.
[0068] FIG. 1 depicts an exemplary leadless cardiac pacemaker (LCP)
that may be implanted into a patient and may operate to deliver one
or more types of pacing therapy to the heart. In some examples, the
LCP may deliver pacing pulses in accordance with one or more
therapies, such as rate responsive pacing therapy, anti-tachycardia
pacing (ATP) therapy, cardiac resynchronization therapy (CRT),
bradycardia therapy, defibrillation therapy, and/or the like. As
can be seen in FIG. 1, LCP 100 may be a compact device with all
components housed within or on housing 120. In the example shown in
FIG. 1, LCP 100 may include telemetry module 102, pulse generator
module 104, electrical sensing module 106, mechanical sensing
module 108, processing module 110, battery 112, and electrodes
114.
[0069] Telemetry module 102 may be configured to communicate with
devices such as sensors, other medical devices, and/or the like,
that are located externally to LCP 100. Such devices may be located
either external or internal to the patient's body. Irrespective of
their location, external devices (i.e. external to the LCP 100 but
not necessarily external to the patient's body) can communicate
with LCP 100 via telemetry module 102 to accomplish one or more
desired functions. For example, LCP 100 may communicate sensed
electrical signals to an external medical device through telemetry
module 102. In some cases, the external medical device may use the
communicated electrical signals to determine occurrences of
arrhythmias, deliver electrical stimulation therapy, and/or perform
other functions.
[0070] In the example shown, LCP 100 may receive sensed electrical
signals from an external medical device through telemetry module
102. In some cases, the LCP 100 may use the received sensed
electrical signals to determine occurrences of arrhythmias, deliver
electrical stimulation therapy, and/or perform other functions. In
some cases, telemetry module 102 may be configured to use one or
more methods for communicating with external devices. For example,
telemetry module 102 may communicate via radiofrequency (RF)
signals, inductive coupling, optical signals, acoustic signals,
conducted communication signals, and/or any other signals suitable
for communication. Communication techniques between LCP 100 and
external devices will be discussed in further detail with reference
to FIG. 4 below.
[0071] Pulse generator module 104 of LCP 100 may be electrically
connected to electrodes 114. In some examples, LCP 100 may
additionally include electrodes 114'. In such examples, pulse
generator 104 may additionally be electrically connected to
electrodes 114', but this is not required. Pulse generator module
104 may be configured to generate electrical stimulation signals,
such as pacing pulses. For example, pulse generator module 104 may
generate electrical stimulation signals by using energy stored in
battery 112 within LCP 100, and deliver the generated electrical
stimulation signals via electrodes 114 and/or 114'. In some
examples, pulse generator module 104 or LCP 100 may include
switching circuitry to selectively connect one or more of
electrodes 114 and/or 114' to pulse generator module 104 in order
to select via which electrodes 114/114' pulse generator 104
delivers the electrical stimulation therapy. Pulse generator module
104 may generate electrical stimulation signals with particular
features or in particular sequences in order to provide one or
multiple of a number of different stimulation therapies. For
example, pulse generator module 104 may be configured to generate
electrical stimulation signals to provide electrical stimulation
therapy to combat bradycardia arrhythmias, tachyarrhythmia
arrhythmias, fibrillation arrhythmias, and/or cardiac
synchronization arrhythmias. In other examples, pulse generator
module 104 may be configured to generate electrical stimulation
signals to provide electrical stimulation therapies different than
those described herein to treat one or more cardiac conditions.
[0072] In some examples, LCP 100 may include electrical sensing
module 106 and/or mechanical sensing module 108. Electrical Sensing
module 106 may be configured to sense electrical cardiac activity
of the heart. In some cases, electrical sensing module 106 may be
connected to electrodes 114/114', and electrical sensing module 106
may receive cardiac electrical signals conducted through electrodes
114/114'. In some instances, the cardiac electrical signals may
represent local information from the chamber in which LCP 100 is
implanted. For instance, if LCP 100 is implanted within a ventricle
of the heart, cardiac electrical signals sensed by LCP 100 through
electrodes 114/114' may represent ventricular cardiac electrical
signals. In some cases, the cardiac electrical signals may
represent remote information that emanates from outside of the
chamber in which LCP 100 is implanted. These can be considered
far-field signals.
[0073] Mechanical sensing module 108 may include, or be
electrically connected to, various sensors, such as accelerometers,
blood pressure sensors, heart sound sensors, blood-oxygen sensors,
and/or other sensors that measure one or more physiological
parameters of the heart and/or patient. Both electrical sensing
module 106 and mechanical sensing module 108 may be connected to
processing module 110, and may provide signals representative of
the sensed electrical activity or physiological parameters to
processing module 110. Although described with respect to FIG. 1 as
separate sensing modules, in some examples, electrical sensing
module 206 and mechanical sensing module 208 may be combined into a
single module if desired.
[0074] Processing module 110 can be configured to control the
operation of LCP 100. For example, processing module 110 may be
configured to receive electrical signals from electrical sensing
module 106. Based on the received signals, processing module 110
may determine occurrences and types of arrhythmias and/or other
conditions. Based on any determined arrhythmias and/or other
conditions, processing module 110 may control pulse generator
module 104 to generate electrical stimulation in accordance with
one or more therapies to treat the determined arrhythmias and/or
other conditions. In some cases, processing module 110 may receive
information from telemetry module 102, and may use such received
information in determining whether an arrhythmia and/or other
condition is occurring, determine a type of arrhythmia and/or other
condition, and/or to take particular action in response to the
received information. Processing module 110 may additionally
control telemetry module 108 to send information to other
devices.
[0075] In some examples, processing module 110 may include a
pre-programmed chip, such as a very-large-scale integration (VLSI)
chip or an application specific integrated circuit (ASIC). In such
instances, the chip may be pre-programmed with control logic in
order to control the operation of LCP 100. By using a
pre-programmed chip, processing module 110 may use less power than
other programmable circuits while still maintaining desired
functionality, which may increase the battery life of LCP 100. In
some cases, processing module 110 may include a programmable
microprocessor. Such a programmable microprocessor may allow a user
to adjust the control logic of LCP 100 after the LCP is
manufactured, thereby allowing greater programming flexibility of
LCP 100 over a pre-programmed chip. However, such programmable
microprocessor may be less energy efficient than a pre-programmed
chip.
[0076] In some examples, processing module 110 may include a memory
circuit, and processing module 110 may store information on and/or
read information from the memory circuit. In some instances, LCP
100 may include a separate memory circuit (not shown) that is in
communication with processing module 110, such that processing
module 110 may read and/or write information to and/or from the
separate memory circuit.
[0077] Battery 112 may provide a power source to LCP 100 for its
operations. In some examples, battery 112 may be a non-rechargeable
lithium-based battery, or other non-rechargeable battery. Because
LCP 100 is an implantable device, access to LCP 100 may be limited.
Accordingly, it is desirable to have sufficient battery capacity to
deliver therapy over a period of treatment such as days, weeks,
months, or years. In some instances, battery 112 may a rechargeable
lithium-based battery, or other rechargeable battery, in order to
facilitate increasing the useable lifespan of LCP 100.
[0078] As depicted in FIG. 1, LCP 100 may include electrodes 114,
which can be secured relative to housing 120 but exposed to the
tissue and/or blood surrounding LCP 100. In some cases, electrodes
114 may be generally disposed on either end of LCP 100 and may be
in electrical communication with one or more of modules 102, 104,
106, 108, and 110. Electrodes 114 may be supported by the housing
120. In some examples, electrodes 114 may be connected to housing
120 only through short connecting wires such that electrodes 114
are not directly secured relative to housing 120.
[0079] In some examples, LCP 100 may additionally include one or
more electrodes 114'. Electrodes 114' may be positioned on the
sides of LCP 100 and may increase the number of electrodes by which
LCP 100 may sense cardiac electrical activity, deliver electrical
stimulation and/or communicate with an external medical device.
Electrodes 114 and/or 114' can be made up of one or more
biocompatible conductive materials such as various metals or alloys
that are known to be safe for implantation within a human body. In
some instances, electrodes 114 and/or 114' connected to LCP 100 may
have an insulative portion that electrically isolates the
electrodes 114 from adjacent electrodes, housing 120, and/or other
materials.
[0080] To implant LCP 100 inside a patient's body, an operator
(e.g., a physician, clinician, etc.), may fix LCP 100 to the
cardiac tissue of the patient's heart. To facilitate fixation, LCP
100 may include one or more anchors 116. Anchor 116 may include any
one of a number of fixation or anchoring mechanisms. For example,
anchor 116 may include one or more pins, staples, threads, screws,
helix, tines, and/or the like. In some examples, although not
shown, anchor 116 may include threads on its external surface that
may run along at least a partial length of anchor 116. The threads
may provide friction between the cardiac tissue and the anchor to
help fix the anchor 116 within the cardiac tissue. In other
examples, anchor 116 may include other structures such as barbs,
spikes, or the like to facilitate engagement with the surrounding
cardiac tissue.
[0081] FIG. 2 illustrates a block diagram of an exemplary medical
device, MD 200, that may be used in accordance with various
examples of the present disclosure. In some cases, MD 200 may be
implanted into a patient, and may operate to sense one or more
signals representative of a physiological condition of the patient.
In some cases, MD 200 may be implanted in a location that is spaced
from the heart of the patient. A device such as depicted in FIG. 2
may be used in conjunction with a device similar to that depicted
in FIG. 1 to deliver rate responsive pacing to a heart of a
patient. As can be seen in FIG. 2, MD 200 may be a compact device
with all components housed within MD 200 or directly on housing
220. As illustrated in FIG. 2, MD 200 may include telemetry module
202, electrical sensing module 206, mechanical sensing module 208,
processing module 210, battery 212, and electrodes 214/214'.
[0082] In some examples, MD 200 may be similar to LCP 100 as
described with respect to FIG. 1. For example, telemetry module
202, electrical sensing module 206, mechanical sensing module 208,
processing module 210, battery 212, and electrodes 214/214' may be
similar to telemetry module 102, electrical sensing module 106,
mechanical sensing module 108, processing module 110, battery 112,
and electrodes 114/114', as described with respect to FIG. 1. In
some cases, MD 200 may not include a pulse generator module.
Accordingly, in some examples, MD 200 may be the same as LCP 100
with some hardware differences. Alternatively, MD 200 may include
all of the components of LCP 100 (and in some cases, a duplicate
device), except that one or more of the components may be disabled
and/or not used, such as a pulse generator module. In some cases,
using the same hardware may reduce the cost of the overall system
by reducing the number of SKU's that need to be developed, tested,
and then maintained and inventoried.
[0083] In some instances, MD 200 may include substantially
different hardware than LCP 100. For example, MD 200 may be
substantially different in size, shape and/or configuration from
LCP 100. For instance, MD 200 may not require as severe of size
constrained as LCP 100 due to typical implant locations for MD 200.
In such examples, MD 200 may include, for example, a larger battery
and/or more powerful processing unit than LCP 100.
[0084] FIG. 3 illustrates a block diagram of another exemplary
medical device that may be used in accordance with various examples
of the present disclosure. FIG. 3 depicts a medical device (MD)
300, which may be used in conjunction with a device similar to LCP
100 in order to help deliver rate responsive pacing. In the example
shown, MD 300 may include telemetry module 308, pulse generator
module 304, sensing module 302, processing module 306 and battery
310. Each of these modules may be similar to modules 102, 104,
106/108, 110 and 112 of LCP 100. In some examples, MD 300 may
include a larger volume within housing 320 than LCP 100. In such
examples, MD 300 may include a larger battery 310 and/or a
processing module 306 capable of handling more complex operations
than processing module 110 of LCP 100.
[0085] While MD 300 may be another leadless device such as shown in
FIG. 1, in some instances MD 300 may includes leads such as leads
312. Leads 312 may include electrical wires that conduct electrical
signals between electrodes 314 and one or more modules located
within housing 320. Leads 312 may be connected to and extend away
from housing 320 of MD 300. In some examples, leads 312 are
implanted on or within a heart of a patient. Leads 312 may contain
one or more electrodes 314 positioned at various locations on leads
312 and distances from housing 320. Some leads 312 may only include
a single electrode 314 while other leads 312 may include multiple
electrodes 314. Generally, electrodes 314 are positioned on leads
312 such that when leads 312 are implanted within the patient, one
or more of the electrodes 314 are positioned to perform a desired
function. In some cases, the one or more of the electrodes 314 may
be in contact with the patient's cardiac tissue. In some cases,
electrodes 314 may conduct intrinsically generated electrical
signals to leads 312, e.g. signals representative of intrinsic
cardiac electrical activity. Leads 312 may, in turn, conduct the
received electrical signals to one or more of the modules 302, 304,
306, and 308 of MD 300. In some cases, MD 300 may generate
electrical stimulation signals, and leads 312 may conduct the
generated electrical stimulation signals to electrodes 314.
Electrodes 314 may conduct the electrical signals to the cardiac
tissue of the patient.
[0086] While not required, in some examples MD 300 may be an
implantable medical device. In such examples, housing 320 of MD 300
may be implanted in a transthoracic region of the patient. Housing
320 may generally include any of a number of known materials that
are safe for implantation in a human body and may, when implanted,
hermetically seal the various components of MD 300 from fluids and
tissues of the patient's body.
[0087] In some cases, MD 300 may be an implantable cardiac
pacemaker (ICP). In this example, MD 300 may have one or more
leads, for example leads 312, which are implanted on or within the
patient's heart. The one or more leads 312 may include one or more
electrodes 314 that are in contact with cardiac tissue and/or blood
of the patient's heart. MD 300 may be configured to sense
intrinsically generated cardiac electrical signals and determine,
for example, one or more cardiac arrhythmias based on analysis of
the sensed signals. MD 300 may be configured to deliver CRT, ATP
therapy, bradycardia therapy, and/or other therapy types via leads
312 implanted within the heart. In some examples, MD 300 may
additionally be configured provide defibrillation therapy.
[0088] In some instances, MD 300 may be an implantable
cardioverter-defibrillator (ICD). In such examples, MD 300 may
include one or more leads implanted within a patient's heart. MD
300 may also be configured to sense cardiac electrical signals,
determine occurrences of tachyarrhythmias based on the sensed
signals, and may be configured to deliver defibrillation therapy in
response to determining an occurrence of a tachyarrhythmia. In
other examples, MD 300 may be a subcutaneous implantable
cardioverter-defibrillator (S-ICD). In examples where MD 300 is an
S-ICD, one of leads 312 may be a subcutaneously implanted lead. In
at least some examples where MD 300 is an S-ICD, MD 300 may include
only a single lead which is implanted subcutaneously, but this is
not required. In other cases, MD 300 may be a transvenous pacemaker
and/or transveneous ICD.
[0089] In some examples, MD 300 may not be an implantable medical
device. Rather, MD 300 may be a device external to the patient's
body, and may include skin-electrodes that are placed on a
patient's body. In such examples, MD 300 may be able to sense
surface electrical signals (e.g. cardiac electrical signals that
are generated by the heart or electrical signals generated by a
device implanted within a patient's body and conducted through the
body to the skin). In such examples, MD 300 may be configured to
deliver various types of electrical stimulation therapy, including
for example defibrillation therapy.
[0090] In some cases, leads 312 may contain one or more sensors,
such as accelerometers, blood pressure sensors, heart sound
sensors, blood-oxygen sensors, and/or other sensors which are
configured to measure one or more physiological parameters of the
heart and/or patient. In such examples, electrical and/or
mechanical sensing module(s) 306, 308 may be in electrical
communication with leads 312 and may receive signals generated from
such sensors.
[0091] FIG. 4 illustrates an example of a medical device system and
a communication pathway via which multiple medical devices may
communicate. In the example shown, medical device system 400 may
include LCPs 402 and 404, external medical device 406, and other
sensors/devices 410. External device 406 may be any of the devices
described previously with respect to FIGS. 2 and 3. Other
sensors/devices 410 may also be any of the devices described
previously with respect to 2 and 3. In other examples, other
sensors/devices 410 may include a sensor, such as an accelerometer,
respiration sensor or blood pressure sensor, or the like. In still
other examples, other sensors/devices 410 may include an external
programmer device that may be used to program one or more devices
of system 400.
[0092] Various devices of system 400 may communicate via
communication pathway 408. For example, LCPs 402, 404, external
device 406 may sense intrinsic cardiac electrical signals and may
communicate such signals to one or more other devices 402/404, 406,
and 410 of system 400 via communication pathway 408. In one
example, one or more of devices 402/404 may receive such signals
and, based on the received signals, determine an occurrence of an
arrhythmia or other heart function abnormality. In some cases,
device or devices 402/404 may communicate such determinations to
one or more other devices 406 and 410 of system 400. Additionally,
one or more of devices 402/404, 406, and 410 of system 400 may take
action based on the communicated determinations, such as by
delivering appropriate electrical stimulation. This description is
just one of many reasons for communication between the various
devices of system 400. It is contemplated that communication
pathway 408 may communicate using RF signals, inductive coupling,
optical signals, acoustic signals, or any other signals suitable
for communication.
[0093] In some cases, communication pathway 408 communicates using
conducted communication. Accordingly, devices of system 400 may
have components that allow for conducted communication. For
instance, the devices of system 400 may send conducted
communication signals (e.g. pulses) into the patient's body via one
or more electrodes of a transmitting device, and may receive the
conducted communication signals (e.g. pulses) via one or more
electrodes of a receiving device. The patient's body may conduct
the conducted communication signals (e.g. pulses) from the one or
more electrodes of the transmitting device to the one or more
electrodes of the receiving device in the system 400. In such
examples, the delivered conducted communication signals (e.g.
pulses) may differ from pacing or other therapy signals. For
example, the devices of system 400 may deliver electrical
communication pulses at an amplitude/pulse width that is
sub-threshold to the heart. In some cases, the amplitude/pulse
width of the delivered electrical communication pulses may be above
the capture threshold of the heart, but may be delivered during a
refractory period of the heart and/or may be incorporated in or
modulated onto a pacing pulse, if desired.
[0094] In some cases, delivered electrical communication pulses may
be modulated in any suitable manner to encode communicated
information. In some cases, the communication pulses may be pulse
width modulated. Alternatively, or in addition, the time between
pulses may be modulated to encode desired communicated information.
In some cases, conducted communication pulses may be voltage
pulses, current pulses, biphasic voltage pulses, biphasic current
pulses, or any other suitable electrical pulse as desired.
[0095] FIG. 5 illustrates example locations of implantation for one
or more medical devices of a medical device system, such as those
described with respect to FIGS. 1-3. FIG. 5 depicts an LCP 502,
which may be similar to LCP 100, implanted within heart 508 of
patient 500. Regions 504A-B depict example regions where one or
more medical devices may be implanted to coordinate with LCP 502 to
deliver rate responsive pacing therapy to heart 508. Regions 504A-B
highlight regions in the upper pectoral regions of patient 500 near
the clavicles. Region 506 illustrates another region where one or
more medical devices may be implanted to coordinate with LCP 502 to
deliver rate responsive pacing therapy to heart 508. Region 506
depicts an area in the chest region of patient 500 above the lung.
In some examples, region 506 may include intercostal spaces between
ribs of patient 500. One feature of both regions 504A-B and 506 is
that each location may include at least a portion of a lung between
the one or more medical devices and the LCP 502. Accordingly,
communication signals sent between a medical device in regions
504A-B and/or 506 and LCP 502 may pass through at least a portion
of lungs 510, as indicated by communication lines 512.
[0096] Regions 504A-B and 506 are illustrative of only a few
regions where one or more medical devices may be implanted to
coordinate with LCP 502 to deliver rate responsive pacing therapy
to heart 508. In other examples, medical device systems may include
medical devices implanted in other regions of patient 500,
sometimes where there is at least a portion of a lung between the
implanted device or devices and LCP 502. As will be discussed
later, when there is a portion of a lung between LCP 502 and
another implanted device, the two devices may cooperate to
determine a transthoracic impedance parameter over time, from which
a respiration rate and/or tidal volume may be derived. The
respiration rate and/or tidal volume may be indicative of a
patient's activity level.
[0097] In order to deliver rate responsive pacing, a medical system
may include a plurality of devices to help determine one or more
parameters, as further described below. Although the examples
described below only include one LCP and one other medical device,
other medical device systems may have additional and/or different
medical devices. In the examples described below, the medical
device system includes an LCP, such as LCP 100, and another medical
device, generally referred to as the other medical device (MD). The
MD may represent any suitable medical device, including those
described above with respect to FIGS. 1-3.
[0098] One example medical device system may include LCP 100
implanted within a patient's heart and another MD implanted within
a patient's upper pectoral region such that a portion of the
patient's lung is disposed between LCP 100 and the MD. The medical
device system may be configured to determine a heart rate
parameter. For example, LCP 100 may be configured to sense cardiac
electrical activity. In some cases, LCP 100 may be configured to
process the sensed cardiac electrical information using a peak
detector and/or a QRS detector. For example, LCP 100 may count the
number of peaks and/or QRS complexes that LCP 100 detects within a
given period of time to determine a current heart rate. That is, if
LCP 100 detects twenty-five peaks and/or QRS complexes within a
fifteen second time period, LCP 100 may determine the heart rate to
be one-hundred beats per minute (bpm). In some cases, LCP 100 may
update the heart rate parameter every five, ten, or twenty-five
second, or any other suitable time period as desired. In some
instances, LCP 100 may update the heart rate parameter on a
beat-by-beat basis. In some cases, and although not required, LCP
100 may communicate the heart rate parameter to the other MD. When
so provided, the heart rate parameter may be communicated on a
periodic basis, for example every one, five, ten, or twenty-five
seconds, or any other appropriate time period.
[0099] In some examples, the other MD may include an accelerometer,
for example as described with respect to FIGS. 1-3. In such
examples, the MD may determine an activity level parameter based on
signals from the accelerometer. In some cases, LCP 100 itself may
not include an accelerometer, or may turn off any attached
accelerometer, as LCP 100 may receive accelerometer data from the
other MD. This may extend the battery life of LCP 100, as LCP 100
may not need to provide power to the connected accelerometer. The
MD may additionally communicate the sensed/determined activity
level parameter to LCP 100 via a patient activity data signal. In
some cases, the MD may communicate the sensed/determined activity
level parameter to LCP 100 on a periodic basis, such as every one,
five, ten, or twenty-five seconds, or any other suitable time
period as desired. In some examples, the MD may employ a duty cycle
for determining a patient activity level. For example, the MD may
measure the activity level of the patient for a period of ten
seconds and then not measure the activity level of the patient for
a period of five seconds, resulting in a duty cycle of two-thirds.
In other examples, the duty cycle may be any other suitable value
such as one-quarter, one-half, three-quarters. In such examples,
the MD may conserve energy over the life of the device as compared
to devices that continuously measure the patient activity
level.
[0100] In some examples, LCP 100 and the other MD may coordinate to
determine a transthoracic impedance parameter. In some cases, LCP
100 may determine the transthoracic impedance parameter, and in
other examples, the other MD may determine the transthoracic
impedance parameter. In some examples where LCP 100 determines the
transthoracic impedance parameter, MD may deliver a voltage pulse
to the patient. In some cases, MD may also measure an amplitude of
the current generated during the delivered voltage pulse. MD may
communicate the measured amplitude of the delivered current to the
LCP 100. LCP 100, in turn, may measure the amplitude of the
received voltage pulse. LCP 100 may generally measure a reduced
voltage level relative to the voltage pulse applied by the MD, as
there will be some voltage drop across the impedance of patient.
Once LCP 100 has measured the amplitude of the received voltage
pulse, and received the measured current amplitude from the MD, LCP
100 may determine a transthoracic impedance parameter using, for
example, Ohm's Law. This is just one example, in another example,
MD may determine a transthoracic impedance parameter using the
measured amplitude of the received voltage pulse, without receiving
a measured current amplitude from the MD.
[0101] When LCP 100 and the MD are separated by at least a portion
of the patient's lung, the transthoracic impedance may change over
time due to inhalation and exhalation of air from the patient's
lungs. Accordingly, and in some cases, LCP 100 and the MD may
cooperate to determine a transthoracic impedance parameter over
time, and the medical device system may obtain information about
the patient's respiration (e.g. breathing rate, tidal volume,
etc.). In some examples, LCP 100 and the MD may coordinate to
determine a transthoracic impedance parameter five times, three
times, or one time a second. In other examples, LCP 100 and the MD
may coordinate to determine a transthoracic impedance parameter
once every two, five, or ten seconds, or any other suitable period
of time.
[0102] In some examples, the MD may be configured to deliver a
voltage pulse with a predetermined voltage amplitude. In such
examples, MD may be programmed with the predetermined amplitude so
that LCP 100 may be able determine a voltage drop from the MD to
the LCP 100. For instance, the amplitude of the voltage pulse may
be equal to the battery voltage of the battery connected to the MD.
In other examples, MD may be configured to deliver a voltage pulse
with a variable amplitude. In such examples, MD may be additionally
configured to communicate the amplitude of the delivered voltage
pulse to LCP 100. For example, the MD may be configured to
periodically determine a lowest amplitude voltage pulse that LCP
100 may detect and deliver a voltage pulse at the determined
amplitude level (or at a slightly increased amplitude level due to
a safety margin) in order to conserve power of the MD. In still
other examples, the voltage pulse may be part of the a patient
activity data signal or some other signal communicated between the
LCP 100 and the MD. By using existing communication pulses, the
power required to determine the transthoracic impedance parameter
may be reduced. However, even in such examples, the MD may still
send a separate communication indicating a measured value of the
current generated by the patient activity data signal, when
desired.
[0103] In some instances, the MD may determine a transthoracic
impedance parameter. In such examples, LCP 100 may generate a
voltage pulse, measure an amplitude of a current generated by the
delivered voltage pulse, and communicate the measured amplitude of
the delivered current to the MD. The MD, in turn, may measure an
amplitude of the received voltage pulse and, in combination with
the received current amplitude, may determine a transthoracic
impedance parameter. As in the above examples when LCP 100
determines the transthoracic impedance parameter, LCP 100 and the
MD may cooperate to determine the transthoracic impedance parameter
on a periodic basis. Additionally, in examples where the MD is not
programmed with the amplitude of the delivered voltage pulse by LCP
100, LCP 100 may communicate such information to the MD.
[0104] In some examples, the voltage pulse used to determine a
transthoracic impedance parameter may be a sub-threshold pulse,
which is a voltage pulse that does not capture the heart. In some
cases, the voltage pulse may be a communication pulse delivered by
the telemetry module of LCP 100 or telemetry module 202 of the
other MD. In still other examples, instead of sending a separate
voltage pulse for determining the transthoracic impedance
parameter, the voltage pulse may be a pacing pulse that is
delivered by LCP 100 to stimulate contraction of the heart. Using
the pacing pulse as the voltage pulse may save LCP 100 energy over
the life of the device. However, in examples where LCP 100 is not
periodically delivering pacing pulses, LCP 100 may be configured to
send voltage pulses at least once every predetermined time period,
such as once every one, three, five, or ten seconds, or any other
suitable time period.
[0105] Based on the transthoracic impedance over time, the medical
device system may determine other various parameters. For example,
since the medical device system may know how the transthoracic
impedance changes over time, the system may determine a tidal
volume parameter and/or a respiration rate parameter. From the
tidal volume parameter and the respiration rate parameter, the
system may determine a minute ventilation parameter.
[0106] In some cases, LCP 100 may determine the transthoracic
impedance parameter, as well as a tidal volume parameter, a
respiration rate parameter, and/or a minute ventilation
parameter.
[0107] In other cases, MD may determine the transthoracic impedance
parameter, as well as a tidal volume parameter, a respiration rate
parameter, and/or a minute ventilation parameter. In yet other
example, LCP 100 and/or the MD may communicate one or more values
necessary to determine a tidal volume parameter, a respiration rate
parameter, and/or a minute ventilation parameter to the other
device. Accordingly, in some examples, LCP 100 may determine the
transthoracic impedance parameter, but the MD may determine a tidal
volume parameter, a respiration rate parameter, and/or a minute
ventilation parameter. In other instances, it may be the other way
around.
[0108] More generally, LCP 100 and the MD may cooperate to identify
an attenuation of an electrically conducted signal sent between the
devices. For example, the MD may send a conducted signal to LCP
100. The MD may also communicate an amplitude of the conducted
signal to LCP 100. LCP 100 may measure an amplitude of the received
conducted signal, and determine an attenuation parameter. The
attenuation parameter include information regarding the patient's
respiration, which may be related to the patient's current activity
level. For example, the LCP 100 may use the attenuation parameter
to determine a measure related to tidal volume, respiration rate,
and/or minute ventilation. Likewise, the LCP 100 may send a
conducted signal to MD. The LDP 100 may also communicate an
amplitude of the conducted signal to the MD. The MD may measure an
amplitude of the received conducted signal, and determine an
attenuation parameter. The MD may use the attenuation parameter to
determine a measure related to tidal volume, respiration rate,
and/or minute ventilation. In either case, LCP 100 and the MD may
cooperate to determine such an attenuation parameter over time,
such as on a periodic basis. As with the transthoracic impedance
parameter, the attenuation parameter may change as a function of
inhalation and exhalation of air from the patient's lung, which may
be related to the patient's current activity level.
[0109] As the inhalation and exhalation of air from the lungs may
cause attenuation of different types of signals, in some examples
the delivered signal may not be an electrically conducted signal.
For instance, in some examples, the signal may instead be a
radiofrequency signal. In other examples, the signal may be an
acoustic signal. Additionally, it is contemplated that the
communication signals between LCP 100 and the MD may be any
suitable type of signal, such as radiofrequency or acoustic
signals. For instance, the patient activity data signal sent from
the MD to the LCP 100 may be communicated by radiofrequency or
acoustic signals. When so provided, LCP 100 and/or MD may be able
to conserve energy by using the communicated patient activity data
signal to determine an attenuation parameter and, in some cases, a
tidal volume parameter, a respiration rate parameter, and/or a
minute ventilation parameter.
[0110] As discussed above, LCP 100 and the MD may cooperate to
determine a patient activity level, and to use the patient activity
level to deliver rate responsive pacing therapy to the heart of the
patient. In one example, LCP 100 may be configured to deliver
pacing pulses to the heart of the patient and adjust the rate at
which pacing pulses are delivered. LCP 100 may have a base pacing
rate at which LCP 100 delivers pacing pulses. LCP 100 may compare
the patient activity level to one or more thresholds to determine
whether LCP 100 should deliver pacing pulses at a rate different
than the base rate. Each region between thresholds may have an
associated delivery rate. Accordingly, LCP 100 may determine that
the patient activity level is above one of the thresholds but below
another one of the thresholds. From this, LCP 100 may determine a
delivery rate and adjusts the pacing rate of delivered pacing
pulses to match the determined delivery rate. In other examples,
LCP 100 may use the patient activity level as a value in a formula
or lookup table to determine an appropriate pacing rate. In such
examples, LCP 100 may periodically, or in some cases continuously,
update the formula with the patient activity level to determine a
pacing rate and adjust the pacing rate of delivered pacing pulses
accordingly.
[0111] In some cases, LCP 100 may adjust the pacing rate of
delivered pacing pulses based on a minute ventilation parameter,
whether determined by LCP 100 or communicated to the LCP 100 from
the MD. For example, LCP 100 may use one or more thresholds for
determining a pacing rate, as described above with respect to the
patient activity level. In other examples, LCP 100 may use a minute
ventilation parameter as a value in a formula for determining a
delivery rate. In such examples, LCP 100 may determine a delivery
rate using the formula as described above with respect to the
patient activity level, and may adjust the rate of delivered pacing
pulses based on the determined delivery rate.
[0112] In still other examples, LCP 100 may use both the patient
activity level and a minute ventilation parameter in determining a
pacing rate. For instance, LCP 100 may compare the patient activity
level to a first set of one or more thresholds to determine a first
pacing rate. LCP 100 may additionally compare the minute
ventilation parameter to a second set of one or more thresholds to
determine a second pacing rate. LCP 100 may then determine a
composite pacing rate, such as by averaging the pacing rates or by
using another relationship or formula that may weight the
determined first pacing rate and second pacing rate differently.
LCP 100 may then adjust the pacing rate of delivered pacing pulses
to the determined composite pacing rate. In some instances, LCP 100
may use both the patient activity level and a minute ventilation
parameter as inputs into a pacing rate function. The pacing rate
function may output a pacing rate using a formula or other
relationship that includes a measure related to the patient
activity level and a minute ventilation parameter as inputs. Other
inputs may also be provided, if desired. LCP 100 may adjust the
pacing rate of delivered pacing pulses to the determined pacing
rate. These are just a few examples of how LCP 100 may determine a
pacing rate for delivering pacing pulses to the heart in a rate
responsive manner.
[0113] In some cases, LCP 100 may not determine a pacing rate.
Rather, the MD may determine a pacing rate and communicate the
determined pacing rate to the LCP 100. As described previously, the
MD may in some cases have a larger battery than LCP 100, and thus
having the MD determine the pacing rate may extend the battery life
of the LCP 100. In such examples, the MD may determine a pacing
rate using any of the methods described above with respect to LCP
100, or using in other suitable method. The MD may then communicate
the determined pacing rate to the LCP 100, and the LCP 100 may
adjust the pacing rate of delivered pacing pulses to the heart
based on the received pacing rate.
[0114] In some examples, the MD may only communicate the delivery
rate periodically instead of continuously. For example, LCP 100 may
have a base pacing rate of delivery of pacing pulses. The MD may be
programmed with this base pacing rate. Accordingly, the MD may only
communicate a pacing rate to LCP 100 when MD determines a pacing
rate that is different from the base pacing rate, sometimes by a
predetermined amount. For example, the MD may only communicate a
new pacing rate to the LCP 100 if the determined pacing rate
differs from the base pacing rate by five or more beats per minute
(bpm). In some instances, the MD may then repeatedly communicate an
updated pacing rate to the LCP 100 until the determine pacing rate
falls back down within the five beats per minute (bpm) threshold
difference level. In some cases, the MD may only communicate an
updated pacing rate to the LCP 100 when the new determined pacing
rate differs from the current pacing rate by five or more beats per
minute (bpm). For instance, the MD may determine a new pacing rate,
and if the new pacing rate is five beats per minute (bpm) different
than the current pacing rate of the LCP 100 (which may be the base
pacing rate or some other pacing rate), then the MD may communicate
the new pacing rate to the LCP 100. The MD may then communicate an
updated pacing rate to the LCP 100 when the MD determines a new
pacing rate that is different than the last communicated pacing
rate by five beats per minute (bpm), such when the new pacing rate
rises by five beats per minute (bpm) or falls by five beats per
minute (bpm) relative to the previously communicated pacing rate.
Of course, the use of five beats per minute (bpm) as a threshold is
only exemplary, and in other examples, the MD may use thresholds of
two, three, or ten beats per minute, or any other suitable
threshold. In examples where LCP 100 has a base pacing rate of
delivery, instead of communicating a new pacing rate, the MD may
communicate a change in pacing rate from the base pacing rate. For
example, if the base pacing rate is 60 bpm, and the determined
pacing rate is 70 bpm, the MD may communicate a value of 10 bpm.
The LCP may then add the communicate value (10 bpm) to the base
pacing rate (60 bpm) to arrive at the determined pacing rate (70
bpm).
[0115] In still other examples, the MD may not send a pacing rate.
Rather, the MD may control the pacing rate of LCP 100 by
communicating a determined patient activity level, sometimes on a
periodic or other basis. For example, the MD may communicate an
activity level to LCP 100, such as when the patient activity level
rises above or falls below one or more activity level thresholds.
Once LCP 100 receives a patient activity level from the MD, LCP 100
may use the patient activity level to determine an appropriate
pacing rate, and adjust the pacing rate of delivered pacing pulses
to the newly determine pacing rate. In other examples, the MD may
only send an updated patient activity level when the MD determines
that the patient activity level changes by at least a first
threshold amount. For example, the MD may only send an updated
patient activity level when the patient activity level changes by
more than five percent. However, the MD may use other thresholds
such as two, three, seven, or ten percent, or any other appropriate
percent. After the MD determines that the patient activity level
changed by a threshold amount, the MD may then communicate the new
patient activity level to LCP 100. After determining a change in
the patient activity level by at least the first threshold amount,
the MD may not send another communication of the patient activity
level to LCP 100 until determining that the new patient activity
level has changed by a second threshold amount. This second
threshold amount may be the same or different than the first
threshold amount. In this manner, the MD may control the pacing
rate without sending a specific pacing rate to LCP 100.
[0116] In some examples, an accelerometer of an MD may be used, at
least in part, to determine a patient activity level. Although not
necessary, the accelerometer may be a three-axis accelerometer.
When so provided, LCP 100 and the MD may cooperate to treat
orthostatic hypotension. For example, the MD may monitor at least a
vertical component of the three-axis accelerometer. More
specifically, in some examples, the MD may compare a rate of change
in the vertical component of the three-axis accelerometer to a
threshold. If the rate of change is greater than a threshold, the
MD may communicate a signal to LCP 100. In some examples, the
signal may set a pacing rate that is higher than the current pacing
rate. In other examples, the signal may itself communicate the rate
of change in the vertical component of the three-axis
accelerometer. In such examples, LCP 100 may determine an increased
pacing rate based on the received signal from the MD. In these
examples, the determined pacing rate may only last for a
predetermined period of time. In other examples, the MD may send an
additional communication with a reduced pacing rate or a reduced
rate of change of the vertical component of the three-axis
accelerometer to cause a reduced pacing rate.
[0117] In some instances, LCP 100 may incorporate additional
parameters to the ones described above in delivering rate
responsive pacing. For example, LCP 100 may have an active
accelerometer. When so provided, LCP 100 may determine one or more
heart sound parameters using the accelerometer. In some cases, LCP
100 may have additional sensors which allow LCP 100 to determine
other parameters such as blood flow, blood pressure, oxygen content
of the blood, temperature, and others. It is contemplated that such
parameters may be used in determining an appropriate pacing rate
for rate responsive pacing therapy.
[0118] FIG. 6 is a flow diagram of an illustrative method that may
be implemented by an implantable medical device, such as one that
includes LCP 100 and at least another medical device, for example
any of the devices described with respect to FIGS. 1-3, whether
including one or more leads or being leadless. Although the method
of FIG. 6 will be described with respect to LCP 100 and an MD, the
illustrative method of FIG. 6 may be performed by any suitable
medical device or medical device system, as desired.
[0119] In some instances, a first implantable medical device, for
instance LCP 100, may be implanted within or proximate a heart of a
patient, and may sense cardiac electrical data, as shown at 602.
LCP 100 may provide pacing therapy to the heart of the patient
based at least in part on the sensed cardiac electrical data, as
shown at 604. A second medical device (MD), for example any of the
devices described with respect to FIGS. 1-3, may be implanted at a
location that is spaced from the heart of the patient and may sense
patient activity, as shown at 606. The MD may wirelessly
communicate a patient activity data signal to the LCP 100, as shown
at 608. LCP 100 may determine an adjustment to the provided pacing
therapy based at least in part on the received patient activity
data signal, and adjust the pacing therapy provided by the LCP 100,
as shown at 610. In some cases, the LCP 100 may adjust the pacing
rate based on the received patient activity data signal, to thereby
provide rate responsive pacing by the LCP 100. In some cases, the
patient activity data signal may represent a level of activity of
the patient, such as derived from an accelerometer, respiration
monitor or sensor and/or any other suitable sensor of the second
medical device (MD). In some cases, the patient activity data
signal may represent a desired pacing rate as determined by the
MD.
[0120] FIG. 7 is a flow diagram of another illustrative method that
may be implemented by an implantable medical device, such as one
that includes LCP 100 and at least another medical device, for
example any of the devices described with respect to FIGS. 1-3,
whether including one or more leads or being leadless. Although the
method of FIG. 7 will be described with respect to LCP 100 and MD,
the illustrative method of FIG. 7 may be performed by any suitable
medical device or medical device system.
[0121] In some examples, a first implantable medical device, for
instance LCP 100, may be implanted within or proximate a heart of a
patient and may be configured to sense cardiac electrical data, as
shown at 702. LCP 100 may provide pacing therapy to the heart of
the patient based at least in part on the sensed cardiac electrical
data, as shown at 704. LCP 100 may wirelessly communicate signals
to another medical device (MD), such as an implantable leadless
medical device that is implanted remote from the heart of the
patient, as shown at 706. The MD may determine one or more
physiological parameters based at least in part on the wirelessly
communicated signals, as shown at 708.
[0122] In some cases, the MD may determine an activity level and/or
an updated pacing rate based, at least in part, on the one or more
physiological parameters. The MD may then communicate the
determined activity level and/or updated pacing rate to the LCP
100, as shown at 710. The LCP 100 may then adjust the pacing rate
based on the received activity level and/or updated pacing rate, to
thereby provide rate responsive pacing by the LCP 100, as shown at
712.
[0123] Those skilled in the art will recognize that the present
disclosure may be manifested in a variety of forms other than the
specific examples described and contemplated herein. For instance,
as described herein, various examples include one or more modules
described as performing various functions. However, other examples
may include additional modules that split the described functions
up over more modules than that described herein. Additionally,
other examples may consolidate the described functions into fewer
modules. Accordingly, departure in form and detail may be made
without departing from the scope and spirit of the present
disclosure as described in the appended claims.
* * * * *