U.S. patent application number 13/941258 was filed with the patent office on 2013-11-14 for remote follow-up automaticity with intelligent data download restrictions.
The applicant listed for this patent is PACESETTER, INC.. Invention is credited to Paul A. Levine.
Application Number | 20130304150 13/941258 |
Document ID | / |
Family ID | 44455474 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130304150 |
Kind Code |
A1 |
Levine; Paul A. |
November 14, 2013 |
REMOTE FOLLOW-UP AUTOMATICITY WITH INTELLIGENT DATA DOWNLOAD
RESTRICTIONS
Abstract
An implanted device is equipped with a flag that indicates to a
remote monitoring unit that an event such as a patient medical
emergency or device failure has occurred. The remote monitoring
unit is configured in some embodiments to maintain a low power
communication link with the implanted device when they are within
range. When the flag indicates an event has occurred, the remote
monitoring unit quickly downloads sensed data collected by the
implanted device and transfers it over a network so that it can be
utilized by a medical practitioner. The remote monitoring unit is
further configured in some embodiments to query the implanted
device at regular intervals. The remote monitoring unit may read a
subset of the data stored by the implanted device and, based on
that data, determine whether to complete a full or partial
download.
Inventors: |
Levine; Paul A.; (Santa
Clarita, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PACESETTER, INC. |
Sylmar |
CA |
US |
|
|
Family ID: |
44455474 |
Appl. No.: |
13/941258 |
Filed: |
July 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13169928 |
Jun 27, 2011 |
8515539 |
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13941258 |
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11838781 |
Aug 14, 2007 |
8005546 |
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13169928 |
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Current U.S.
Class: |
607/32 |
Current CPC
Class: |
A61N 1/37282 20130101;
A61N 1/37252 20130101; A61N 1/37211 20130101 |
Class at
Publication: |
607/32 |
International
Class: |
A61N 1/372 20060101
A61N001/372 |
Claims
1. A method for controlling the download of information sensed by
an implantable cardiac device, comprising the steps of: sensing
cardiac activity; monitoring the performance of the implantable
cardiac device; determining whether an event has occurred based on
collected data corresponding to the sensed cardiac activity and to
the performance of the implantable cardiac device; storing the
collected data indicative of the event when the event has occurred;
determining whether the event corresponds to a dangerous condition
when the event has occurred; setting an indicator that induces an
immediate data download to an external monitoring device when it is
determined that the event corresponds to a dangerous condition; and
resetting the indicator after the data download.
2. The method of claim 1, wherein determining whether the event has
occurred comprises analyzing the collected data based on a
plurality of pre-selected criteria.
3. The method of claim 1, wherein determining whether the event
corresponds to a dangerous condition comprises analyzing the
collected data based on a plurality of pre-selected criteria.
4. The method of claim 1, wherein the indicator comprises a data
flag that has a first set condition indicating that the event
corresponding to a dangerous condition has occurred and a second
reset condition indicating that the data download has occurred
after the last event corresponding to a dangerous condition.
5. The method of claim 1, wherein the data download corresponds
only to data related to the event corresponding to a dangerous
condition.
6. The method of claim 1, wherein the event comprises at least one
of: an equipment malfunction, a low battery charge reading, and a
dangerous medical condition.
7. The method of claim 1, wherein the event comprises at least one
sensed medical condition selected from the group of ventricular
fibrillation, ventricular tachycardia, atrial fibrillation, and
atrial flutter.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of copending U.S. patent
application Ser. No. 13/169,928, filed Jun. 27, 2011, which is a
division of U.S. patent application Ser. No. 11/838,781, filed Aug.
14, 2007 (now U.S. Pat. No. 8,005,546).
FIELD OF THE INVENTION
[0002] The present invention generally relates to an implantable
pulse generator or implantable cardiac stimulation devices. The
present invention more particularly concerns a system for
efficiently downloading data collected by an implanted pulse
generator to a remote monitoring unit.
BACKGROUND OF THE INVENTION
[0003] Implantable cardiac pulse generators such as implantable
cardiac stimulation devices (IPGs) may take the form of implantable
cardioverter-defibrillators that utilize unique and rapid
stimulation rates or high energy shocks to treat accelerated or
chaotic rhythms of the heart in an effort to restore a normal heart
rhythm. IPGs can also include pacemakers that provide low voltage
stimulation to regulate the heart rate in the setting of a
bradycardia. In addition to providing therapeutic stimulation,
these IPGs include sensing circuits that sense electrical signals
generated by the heart indicative of cardiac activity and memory
device to store these sensed signals and data. IPGs are typically
also configured to transmit stored signals and data to external
devices or programmers in order to aid a diagnosis by a physician
or clinician. For the purpose of this patent, an IPG represents any
implantable medical device capable of monitoring one or more
physiologic functions and/or delivering therapy. As such, in
addition to cardiac pacemakers and cardioverter-defibrillators
which are well established in the art, this also includes
neurologic stimulation devices, gastric stimulation devices,
implantable monitors including cardiac monitors, glucose monitors
and others.
[0004] Historically, the transfer of data from the IPG to the
programmer or other device was performed either in the hospital or
the physician's office. Increasingly, the transfer of this data
from the implantable device to an external device accessible by a
physician is done in locations outside of a clinic, hospital, or
other traditional medical setting. For example, a patient having an
IPG may also have a remote monitoring unit (RMU) in their home that
automatically communicates with the IPG to wirelessly download data
acquired by the IPG. Data acquired by the RMU may be transferred
over a network to a remote server so that it is accessible to a
physician or a clinician at a remote medical site.
[0005] However, RMUs fail to handle many dangerous events and the
general transfer of data efficiently. For example, a typical RMU
located in a patient's home may operate by downloading information
obtained and stored on the IPG at regular intervals. However, an
event (e.g., a patient's medical condition) may occur shortly after
the previous download and this event would not be acquired by the
system until the next scheduled download. In the case that the
event represents a problem with the IPG or a patient emergency, the
proper medical professional may not be alerted quickly when another
scheduled download is not for some time. This may put the patient
at risk when a problem is being experienced and they are unable to
either detect or inform a physician or emergency medical technician
themselves.
[0006] One current solution to this problem used with some RMUs is
to increase the frequency at which data transfers occur. If the RMU
downloads information from the IPG more frequently, then the
average time between an event and data collection will decrease.
However, the frequent transfer of information from the implanted
device and the monitoring system may reduce the battery life of the
IPG because of the increased power requirements of the more
frequent wireless transfer of information. When there is no
meaningful event to report, this excessive transfer of information
is inefficient and needlessly reduces battery life as well as
potentially overloads the memory of the server or the RMU.
Additionally, the drain on the battery becomes worse as the time
between transfers decreases, forcing a trade-off with this solution
between device life and safe monitoring of the patient. Even in
circumstances where the download frequency has not been increased,
valuable battery power may be used to implement preplanned
downloads that contain information of limited value. Generally,
implantable cardiac stimulation devices that have download
capability are programmed to download at regular intervals.
However, some patients may have relatively stable cardiac
conditions such that the information being downloaded provides no
real new information to the treating physician. In this
circumstance, battery power is being consumed to provide
information of limited value. Conserving battery power is, of
course, of great concern with implanted devices as IPG replacement
due to battery depletion typically involves an invasive medical
procedure.
[0007] Thus, there is a need in the art for a system that more
efficiently provides information obtained by an IPG to a RMU. There
is a need in the art for a system that is able to quickly alert a
physician or emergency medical technician to the occurrence of a
major event, while limiting downloads and drain on battery power
when the downloaded information does not warrant the power
expense.
SUMMARY OF THE INVENTION
[0008] According to one embodiment, an implantable pulse generator
is configured to sense cardiac activity and to provide therapeutic
electrical stimulation. The IPG advantageously provides for the
download of sensed data only when there has been a significant
change in the data in order to conserve the battery life of the IPG
and minimize data overload to the system. The IPG comprises a
wireless transceiver configured to establish a communications link
with an external computing device and to broadcast data to and
receive data from the external computing device. The IPG further
comprises at least one sensor configured to sense cardiac activity
including the activity of a patient's heart and the performance of
the implanted pulse generator. A memory is configured to store data
indicative of the sensed cardiac activity and further comprises a
download schedule including a plurality of scheduled downloads. A
processor of the IPG is configured to analyze the stored data
according to the download schedule in order to determine whether a
significant change has occurred. The processor is further
configured to induce the wireless transceiver to transmit the
stored data to the external computing device when it is determined
that a significant change has occurred. The processor is configured
to not undertake one of the plurality of scheduled downloads when
it is determined that a significant change has not occurred.
[0009] According to another embodiment, a cardiac monitoring system
is provided including an implantable cardiac stimulation device and
a monitoring device. The implantable cardiac stimulation device has
a memory and a communications link. The implantable cardiac
stimulation device provides therapy to the patient's heart in
accordance with a plurality of programmed parameters, senses the
performance of the device and the patient's heart, and stores
signals indicative thereof in the memory. The implantable cardiac
stimulation device categorizes the signals based upon pre-selected
criteria. The monitoring device includes a first communications
link that is capable of communicating with the implantable cardiac
stimulation device. The monitoring device periodically queries the
implantable cardiac stimulation device for update information about
the performance of the implantable cardiac stimulation device or
the patient's heart. The implantable cardiac stimulation device is
configured to transmit update information generated from the stored
signals in response to receiving the periodic query from the
monitoring device only when the implantable cardiac stimulation
device has categorized the signals based upon the pre-selected
criteria as being important enough to warrant transmission.
[0010] According to yet another embodiment, a method of controlling
a computing device that is configured to communicate with an
implantable device in order to read a first set of data from the
implantable device is provided. The method allows for the immediate
download of data relating to an emergency event detected by the
implantable device and for the generation of an alarm signaling the
emergency event. The method comprises the computing device
establishing a wireless communications link with the implantable
device and reading an indicator in the implantable device. The
computing device downloads the first set of data when the indicator
indicates that a first event has occurred. The computing device
then resets the indicator in the implantable device so that it
indicates that that the first set of data has been downloaded. The
method further comprises generating an alarm when the indicator
indicates that the first event has occurred.
[0011] Accordingly, different embodiments allow for the efficient
control and monitoring of an IPG or an implantable cardiac
stimulation device so that a data download is attempted to an RMU
as soon as the IPG is in proximity of an RMU after an emergency
event has occurred. Downloads otherwise occur in some embodiments
according to a schedule, but scheduled downloads may be canceled if
it is determined that the data stored in the IPG has not changed
significantly. In some embodiments, alarms are generated by the RMU
to notify those nearby or medical professionals at remote locations
in order to provide assistance when an emergency event occurs.
[0012] Throughout the disclosure, reference is made to an IPG in
order to describe certain aspects of the invention. However, a
skilled artisan will understand that some or all of the features
described herein may be applied to other implantable devices.
Specifically, other implantable devices that are capable of
detecting physiologic events and/or monitoring their own behavior,
and that are capable of transferring such data to a programmer in a
medical facility or to an RMU outside of a medical facility, may be
used according to certain embodiments of the invention.
Accordingly, the disclosure provided here may apply not only to
sensed data indicative of the activity of the heart, but to any
sensed data indicative of a patient's medical condition.
Furthermore, the disclosure may apply to devices that monitor
activity or device performance without providing any type of
therapy, such as electrical stimulation therapy.
[0013] For purposes of summarizing the invention, certain aspects,
advantages, and novel features of the invention have been described
herein. It is to be understood that not necessarily all such
advantages may be achieved in accordance with any particular
embodiment of the invention. Thus, the invention may be embodied or
carried out in a manner that achieves or optimizes one advantage or
group of advantages as taught herein without necessarily achieving
other advantages as may be taught or suggested herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Further features and advantages of the present invention may
be more readily understood by reference to the following
description taken in conjunction with the accompanying drawings, in
which:
[0015] FIG. 1 is a simplified diagram illustrating an implantable
stimulation device in electrical communication with three leads
implanted into a patient's heart for delivering multi-chamber
stimulation and shock therapy, according to an embodiment of the
invention;
[0016] FIG. 2 is a functional block diagram of a multi-chamber
implantable stimulation device illustrating the basic elements of a
stimulation device, which can provide cardioversion,
defibrillation, and pacing stimulation in four chambers of the
heart, according to an embodiment of the invention;
[0017] FIG. 3 is a functional block diagram of an external
programmer device, according to an embodiment of the invention;
[0018] FIG. 4 is a diagram of a system for connecting an implanted
cardiac device to a computing station at a medical facility,
according to an embodiment of the invention;
[0019] FIG. 5 is a flow chart describing a method for intelligently
controlling the recording and transfer of data from an implantable
pulse generator based upon the occurrence of a significant event or
change in stored data, according to one embodiment of the
invention;
[0020] FIG. 6 is a flow chart describing a method for intelligently
controlling the scheduled download of data to a remote monitoring
unit based upon the occurrence of a significant event or change in
stored data, according to an embodiment of the invention;
[0021] FIG. 7 is a flow chart describing a method for intelligently
controlling the download of data to a remote monitoring unit based
upon the occurrence of a significant event, according to an
embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] The following description is of the best mode presently
contemplated for practicing the invention. This description is not
to be taken in a limiting sense but is made merely for the purpose
of describing the general principles of the invention. The scope of
the invention should be ascertained with reference to the issued
claims. In the description of the invention that follows, like
numerals or reference designators will be used to refer to like
parts or elements throughout.
[0023] According to an embodiment shown in FIG. 1, there is an
implanted pulse generator throughout IPG 10 in electrical
communication with a patient's heart 12 by way of three leads, 20,
24 and 30, suitable for delivering multi-chamber stimulation and
shock therapy. To sense atrial cardiac signals and to provide right
atrial chamber stimulation therapy, the IPG 10 is coupled to an
implantable right atrial lead 20 having an atrial tip electrode 22,
which typically is implanted in the patient's right atrium, often
in the atrial appendage but not limited to this position.
[0024] To sense left atrial and ventricular cardiac signals and to
provide left chamber pacing therapy, the IPG 10 is coupled to a
"coronary sinus" lead 24 designed for placement in the "coronary
sinus region" via the coronary sinus is for positioning a distal
electrode adjacent to the left ventricle and/or additional
electrode(s) adjacent to the left atrium. As used herein, the
phrase "coronary sinus region" refers to the venous vasculature of
the left ventricle, including any portion of the coronary sinus,
great cardiac vein, left marginal vein, left posterior ventricular
vein, middle cardiac vein, and/or small cardiac vein or any other
cardiac vein accessible by the coronary sinus.
[0025] Accordingly, an exemplary coronary sinus lead 24 is designed
to receive atrial and ventricular cardiac signals and to deliver
left ventricular pacing therapy using a left ventricular tip
electrode 26, left atrial pacing therapy using a left atrial ring
electrode 27, and shocking therapy using a left atrial coil
electrode 28. For a complete description of a coronary sinus lead,
see U.S. Pat. No. 5,466,254, "Coronary Sinus Lead with Atrial
Sensing Capability" (Helland), which patent is hereby incorporated
herein by reference.
[0026] The IPG 10 is also shown in electrical communication with
the patient's heart 12 by way of an implantable right ventricular
lead 30 having, in this embodiment, a right ventricular tip
electrode 32, a right ventricular ring electrode 34, a right
ventricular (VR) coil electrode 36, and an SVC coil electrode 38.
Typically, the right ventricular lead 30 is transvenously inserted
into the heart 12 so as to place the right ventricular tip
electrode 32 in the right ventricular apex so that the VR coil
electrode 36 will be positioned in the right ventricle and the SVC
coil electrode 38 will be positioned in the superior vena cava.
Accordingly, the right ventricular lead 30 is capable of receiving
cardiac signals, and delivering stimulation in the form of pacing
and shock therapy to the right ventricle. The right ventricular tip
electrode 32, however can be placed virtually any place in the
right ventricle such as the mid-septal region or the right
ventricular outflow tract and is not limited to the right
ventricular apex.
[0027] While IPG 10 is shown in this embodiment as having certain
leads, according to other embodiments IPG 10 may additionally or
alternatively comprise other sensors and leads. For example, IPG 10
may sense the electrical activity of a patient's heart 12 utilizing
a multiple electrode lead having 8, 16, 32 or some other number of
electrodes spatially distributed across at least one chamber of the
heart 12. In some embodiments other sensors may be used such as
pressure sensors, or the like.
[0028] According to an embodiment illustrated in FIG. 2, a
simplified block diagram is shown of the multi-chamber IPG 10,
which is capable of treating both fast and slow arrhythmias with
stimulation therapy, such as cardioversion, defibrillation, and
pacing stimulation. While a particular multi-chamber device is
shown, this is for illustration purposes only, and one of skill in
the art could readily duplicate, eliminate, or disable the
appropriate circuitry in any desired combination to provide a
device capable of treating the appropriate chamber(s) with
cardioversion, defibrillation, and pacing stimulation. In certain
embodiments of the invention, an implanted device may be utilized
having appropriate circuitry for sensing the electrical activity of
the heart without circuitry for providing stimulation therapy.
[0029] The housing 40 for the IPG 10, shown schematically in FIG.
2, is often referred to as the "can", "case", or "case electrode"
and will act as the return electrode for all "unipolar" modes. The
housing 40 can further be used as a return electrode alone or in
combination with one or more of the coil electrodes, 28, 36, and
38, for shocking purposes. The housing 40 further comprises a
connector (not shown) having a plurality of terminals, 42, 44, 46,
48, 52, 54, 56, and 58 (shown schematically and, for convenience,
the names of the electrodes to which they are connected are shown
next to the terminals). As such, to achieve right atrial sensing
and pacing, the connector comprises a right atrial tip terminal (AR
TIP) 42 adapted for connection to the atrial tip electrode 22.
[0030] To achieve left chamber sensing, pacing, and shocking, the
connector comprises a left ventricular tip terminal (VL TIP) 44, a
left atrial ring terminal (AL RING) 46, and a left atrial shocking
terminal (AL COIL) 48, which are adapted for connection to the left
ventricular tip electrode 26, the left atrial ring electrode 27,
and the left atrial coil electrode 28, respectively.
[0031] To support right chamber sensing, pacing, and shocking, the
connector further comprises a right ventricular tip terminal (VR
TIP) 52, a right ventricular ring terminal (VR RING) 54, a right
ventricular shocking terminal (VR COIL) 56, and an SVC shocking
terminal (SVC COIL) 58, which are adapted for connection to the
right ventricular tip electrode 32, right ventricular ring
electrode 34, the RV coil electrode 36, and the SVC coil electrode
38, respectively.
[0032] At the core of the IPG 10 is a programmable microcontroller
60, which controls the various modes of stimulation therapy. As is
well known in the art, the microcontroller 60 typically comprises a
microprocessor, or equivalent control circuitry, designed
specifically for controlling the delivery of stimulation therapy
and can further include RAM or ROM memory, logic and timing
circuitry, state machine circuitry, and I/O circuitry. Typically,
the microcontroller 60 comprises the ability to process or monitor
input signals (data) as controlled by a program code stored in a
designated block of memory. The details of the design and operation
of the microcontroller 60 are not critical to the present
invention. Rather, any suitable microcontroller 60 can be used that
carries out the functions described herein. The use of
microprocessor-based control circuits for performing timing and
data analysis functions are well known in the art.
[0033] As shown in FIG. 2, an atrial pulse generator 70 and a
ventricular pulse generator 72 generate pacing stimulation pulses
for delivery by the right atrial lead 20, the right ventricular
lead 30, and/or the coronary sinus lead 24 via an electrode
configuration switch 74. It is understood that in order to provide
stimulation therapy in each of the four chambers of the heart, the
atrial and ventricular pulse generators, 70 and 72, can include
dedicated, independent pulse generators, multiplexed pulse
generators, or shared pulse generators. The pulse generators, 70
and 72, are controlled by the microcontroller 60 via appropriate
control signals, 76 and 78, respectively, to trigger or inhibit the
stimulation pulses.
[0034] The microcontroller 60 further comprises timing control
circuitry 79 that is used to control the timing of such stimulation
pulses (e.g., pacing rate, atrio-ventricular (AV) delay,
inter-atrial conduction (A-A) delay, or inter-ventricular
conduction (V-V) delay, etc.) as well as to keep track of the
timing of refractory periods, PVARP intervals, noise detection
windows, evoked response windows, alert intervals, marker channel
timing, etc., which is well known in the art.
[0035] The switch 74 comprises a plurality of switches for
connecting the desired electrodes to the appropriate I/O circuits,
thereby providing electrode programmability. Accordingly, the
switch 74, in response to a control signal 80 from the
microcontroller 60, determines the polarity of the stimulation
pulses (e.g., unipolar, bipolar, combipolar, etc.) by selectively
closing the appropriate combination of switches (not shown) as is
known in the art.
[0036] Atrial sensing circuits 82 and ventricular sensing circuits
84 can also be selectively coupled to the right atrial lead 20,
coronary sinus lead 24, and the right ventricular lead 30, through
the switch 74 for detecting the presence of cardiac activity in
each of the four chambers of the heart. Accordingly, the atrial
(ATR. SENSE) and ventricular (VTR. SENSE) sensing circuits, 82 and
84, can include dedicated sense amplifiers, multiplexed amplifiers,
or shared amplifiers. The switch 74 determines the "sensing
polarity" of the cardiac signal by selectively closing the
appropriate switches, as is also known in the art. In this way, the
clinician can program the sensing polarity independent of the
stimulation polarity.
[0037] Each sensing circuit, 82 and 84, preferably employs one or
more low power, precision amplifiers with programmable gain and/or
automatic gain control, bandpass filtering, and a threshold
detection circuit, as known in the art, to selectively sense the
cardiac signal of interest. The automatic gain control enables the
IPG 10 to deal effectively with the difficult problem of sensing
the low amplitude signal characteristics of atrial or ventricular
fibrillation. The outputs of the atrial and ventricular sensing
circuits, 82 and 84, are connected to the microcontroller 60 which,
in turn, are able to trigger or inhibit the atrial and ventricular
pulse generators, 70 and 72, respectively, in a demand fashion in
response to the absence or presence of cardiac activity in the
appropriate chambers of the heart. The sensing circuits, 82 and 84,
in turn, receive control signals over signal lines, 86 and 88, from
the microcontroller 60 for purposes of controlling the gain,
threshold, polarization charge removal circuitry (not shown), and
the timing of any blocking circuitry (not shown) coupled to the
inputs of the sensing circuits, 82 and 86, as is known in the
art.
[0038] For arrhythmia detection, the IPG 10 utilizes the atrial and
ventricular sensing circuits, 82 and 84, to sense cardiac signals
to determine whether a rhythm is physiologic or pathologic. As used
herein "sensing" is reserved for the noting of an electrical
signal, and "detection" is the processing of these sensed signals
and noting the presence of an arrhythmia. The timing intervals
between sensed events (e.g., P-waves, R-waves, and depolarization
signals associated with fibrillation, which are sometimes referred
to as "F-waves" or "Fib-waves") are then classified by the
microcontroller 60 by comparing them to a predefined rate zone
limit (i.e., bradycardia, normal, low rate VT, high rate VT, and
fibrillation rate zones) and various other characteristics (e.g.,
sudden onset, stability, physiologic sensors, and morphology, etc.)
in order to determine the type of remedial therapy that is needed
(e.g., bradycardia pacing, anti-tachycardia pacing, cardioversion
shocks or defibrillation shocks, collectively referred to as
"tiered therapy").
[0039] Cardiac signals are also applied to the inputs of an
analog-to-digital (A/D) data acquisition system 90. The data
acquisition system 90 is configured to acquire intracardiac
electrogram (EGM) signals, convert the raw analog data into a
digital signal, and store the digital signals for later processing
and/or telemetric transmission to an external device 102. The data
acquisition system 90 is coupled to the right atrial lead 20, the
coronary sinus lead 24, and the right ventricular lead 30 through
the switch 74 to sample cardiac signals across any pair of desired
electrodes.
[0040] Advantageously, the data acquisition system 90 can be
coupled to the microcontroller, or other detection circuitry, for
detecting an evoked response from the heart 12 in response to an
applied stimulus, thereby aiding in the detection of "capture".
Capture occurs when an electrical stimulus applied to the heart is
of sufficient energy to depolarize the cardiac tissue, thereby
causing the heart muscle to contract. The microcontroller 60
detects a depolarization signal during a window following a
stimulation pulse, the presence of which indicates that capture has
occurred. The microcontroller 60 enables capture detection by
triggering the ventricular pulse generator 72 to generate a
stimulation pulse, starting a capture detection window using the
timing control circuitry 79 within the microcontroller 60, and
enabling the data acquisition system 90 via control signal 92 to
sample the cardiac signal that falls in the capture detection
window and, based on the amplitude, determines if capture has
occurred.
[0041] Capture detection can occur on a beat-by-beat basis or on a
sampled basis. Preferably, a capture threshold search is performed
once a day during at least the acute phase (e.g., the first 30
days) and less frequently thereafter. A capture threshold search
would begin at a desired starting point (either a high energy level
or the level at which capture is currently occurring) and decrease
the energy level until capture is lost. The lowest value at which
there is consistent capture is known as the capture threshold.
Thereafter, a safety margin or a working margin is added to the
capture threshold.
[0042] The microcontroller 60 is further coupled to a memory 94 by
a suitable data/address bus 96, wherein the programmable operating
parameters used by the microcontroller 60 are stored and modified,
as required, in order to customize the operation of the IPG 10 to
suit the needs of a particular patient. Such operating parameters
define, for example, pacing pulse amplitude, pulse duration,
electrode polarity, rate, sensitivity, automatic features,
arrhythmia detection criteria, and the amplitude, waveshape, and
vector of each shocking pulse to be delivered to the patient's
heart 12 within each respective tier of therapy. An embodiment of
the invention senses and stores a relatively large amount of data
(e.g., from the data acquisition system 90), which data can then be
used for subsequent analysis to guide the programming of the IPG
10.
[0043] Advantageously, the operating parameters of the IPG 10 can
be non-invasively programmed into the memory 94 through a telemetry
circuit 100 in telemetric communication with the external device
102, such as a remote monitoring unit, programmer, transtelephonic
transceiver, or a diagnostic system analyzer. The telemetry circuit
100 is activated by the microcontroller by a control signal 106.
The telemetry circuit 100 advantageously allows intracardiac
electrograms and status information relating to the operation of
the IPG 10 (as contained in the microcontroller 60 or memory 94) to
be sent to the external device 102 through an established
communication link 104.
[0044] In the preferred embodiment, the IPG 10 further comprises a
physiologic sensor 108, commonly referred to as a "rate-responsive"
sensor because it is typically used to adjust pacing stimulation
rate according to the exercise state of the patient. However, the
physiological sensor 108 can further be used to detect changes in
cardiac output, changes in the physiological condition of the
heart, or diurnal changes in activity (e.g., detecting sleep and
wake states). Accordingly, the microcontroller 60 responds by
adjusting the various pacing parameters (such as rate, AV Delay,
V-V Delay, etc.) at which the atrial and ventricular pulse
generators, 70 and 72, generate stimulation pulses. While shown as
being included within the IPG 10, it is to be understood that the
physiologic sensor 108 can also be external to the IPG 10, yet
still be implanted within or carried by the patient. A common type
of rate responsive sensor is an activity sensor, such as an
accelerometer or a piezoelectric crystal, which is mounted within
the housing 40 of the IPG 10. Other types of physiologic sensors
are also known, for example, sensors that sense the oxygen content
of blood, respiration rate and/or minute ventilation, pH of blood,
ventricular gradient, etc. However, any sensor can be used that is
capable of sensing a physiological parameter that corresponds to
the exercise state of the patient. The type of sensor used is not
critical and is shown only for completeness.
[0045] The stimulation device additionally comprises a battery 110,
which provides operating power to the circuits shown in FIG. 2,
including telemetry circuit 100. For the IPG 10, which employs
shocking therapy, the battery 110 is capable of operating at low
current drains for long periods of time, and then be capable of
providing high-current pulses (for capacitor charging) when the
patient requires a shock pulse. The battery 110 also has a
predictable discharge characteristic so that elective replacement
time can be detected. Accordingly, the IPG 10 preferably employs
lithium/silver vanadium oxide batteries.
[0046] The IPG 10 further comprises magnet detection circuitry (not
shown), coupled to the microcontroller 60. It is the purpose of the
magnet detection circuitry to detect when a magnet is placed over
the IPG 10, which magnet can be used by a clinician to perform
various test functions of the IPG 10 and/or to signal the
microcontroller 60 that the external programmer 102 is in place to
receive or transmit data to the microcontroller 60 through the
telemetry circuits 100. However, the magnet detection circuitry is
not necessary to establish a communication link 104 according to
some embodiments. In certain embodiments, the magnetic detection
circuitry may trigger specific behavior such as signaling the
status of the battery 110 or storing an electrogram.
[0047] As further shown in FIG. 2, the IPG 10 is shown as having an
impedance measuring circuit 112, which is enabled by the
microcontroller 60 via a control signal 114. The known uses for an
impedance measuring circuit 112 include, but are not limited to,
lead impedance surveillance during the acute and chronic phases for
proper lead positioning or dislodgement; detecting operable
electrodes and automatically switching to an operable pair if
dislodgement occurs; measuring respiration or minute ventilation;
measuring thoracic impedance for determining shock thresholds;
detecting when the device has been implanted; measuring stroke
volume; and detecting the opening of heart valves, etc. The
impedance measuring circuit 112 is advantageously coupled to the
switch 74 so that any desired electrode can be used.
[0048] In the case where the IPG 10 is intended to operate as an
implantable cardioverter/defibrillator (ICD) device, it detects the
occurrence of an arrhythmia, and automatically applies an
appropriate electrical shock therapy to the heart aimed at
terminating the detected arrhythmia. To this end, the
microcontroller 60 further controls a shocking circuit 116 by way
of a control signal 118. The shocking circuit 116 generates
shocking pulses of low (up to 0.5 Joules), moderate (0.5-10
Joules), or high energy (11 to 40 Joules), as controlled by the
microcontroller 60. Such shocking pulses are applied to the
patient's heart 12 through at least one shocking electrode but
potentially more shocking electrodes, and as shown in this
embodiment, selected from the left atrial coil electrode 28, the RV
coil electrode 36, and/or the SVC coil electrode 38. As noted
above, the housing 40 can act as an active electrode in combination
with the RV electrode 36, or as part of a split electrical vector
using the SVC coil electrode 38 or the left atrial coil electrode
28 (i.e., using the RV electrode as a common electrode).
[0049] Cardioversion shocks are generally considered to be of low
to moderate energy level (so as to conserve battery life), and/or
synchronized with an R-wave and/or pertaining to the treatment of
tachycardia. Defibrillation shocks are generally of moderate to
high energy level (i.e., corresponding to thresholds in the range
of 5-40 Joules), and pertaining to the treatment of fibrillation.
Accordingly, the microcontroller 60 is capable of controlling the
synchronous or asynchronous delivery of the shocking pulses.
[0050] Microcontroller 60 of the IPG 10 further comprises an event
flag module 123. As discussed below, flag 123 can be set by an
external device 102 in order to indicate that the external device
102 has downloaded data contained in the memory 94 of
microcontroller 60. When the external device 102 sets the flag 123,
the flag 123 may correspond to an enabled condition and in some
embodiments a logical "I" value. The microcontroller 60 is further
configured in some embodiments to set the flag 123 when an event
has occurred to a disabled condition, corresponding in some
embodiments to a logical "0" value. The use of a particular
electrical value or signal for each condition of the flag may, of
course, be varied depending on a particular design choice. In some
embodiments, flag 123 includes multiple flags corresponding to a
variety of indicators for indicating different events or
conditions. As will be explained in more detail below, the flag 123
may therefore be used in some embodiments to indicate when a remote
monitoring unit 62 should download data from the IPG 10.
[0051] FIG. 3 is a functional block diagram of one embodiment of
the external device 102, such as a physician's programmer or remote
monitoring unit. The external device 102 comprises a CPU 122 in
communication with an internal bus 124. The internal bus 124
provides a common communication link and power supply between
various electrical components of the external device 102, such as
the CPU 122. The external device 102 also comprises memory and data
storage such as ROM 126, RAM 130, and a hard drive 132 commonly in
communication with the internal bus 124. The ROM 126, RAM 130, and
hard drive 132 provide temporary memory and non-volatile storage of
data in a well known manner. In one embodiment, the ROM 126, RAM
130, and hard drive 132 can store control programs and commands for
upload to the IPG 10 as well as operating software for display of
data received from the IPG 10. It will be appreciated that in
certain embodiments alternative data storage/memory devices, such
as flash memory, can be included or replace one or more of the ROM
126, RAM 130, and hard drive 132 without detracting from the spirit
of the invention.
[0052] The external device 102 also comprises a display 134. The
display 134 is adapted to visually present graphical and
alphanumeric data in a manner well understood in the art. The
external device 102 also comprises input devices 136 to enable a
user to provide commands and input data to the external device 102.
In one embodiment, the input devices 136 include a keyboard 140, a
plurality of custom keys 142, and a touch screen 144 aspect of the
display 134. The keyboard 140 facilitates entry of alphanumeric
data into the external device 102. The custom keys 142 are
programmable to provide one touch functionality of predefined
functions and/or operations. The custom keys 142 can be embodied as
dedicated touch keys, such as associated with the keyboard 140
and/or predefined areas of the touch screen 144. In this
embodiment, the external device 102 also comprises a speaker 146
and a printer 150 in communication with the internal bus 124. The
speaker 146 is adapted to provide audible alert send signals to a
user. The printer 150 is adapted to provide a printed readout of
information from the external device 102.
[0053] In this embodiment, the external device 102 also comprises a
CD drive 152 and a floppy drive 154 which together provide
removable data storage. In this embodiment, the external device
also comprises a parallel input-output (IO) circuit 156, a serial
IO circuit 160, and an analog output circuit 162. In certain
embodiments, the external device 102 also comprises a USB
interlace. In some embodiments, the external device 102 may also
comprise an industry standard interface compatible with other
portable storage devices such as a flash memory device. These
circuits 156, 160, 162 provide a variety of communication
capabilities between the external device 102 and other devices in a
manner well understood in the art.
[0054] The external device 102 also comprises an electrocardiogram
(ECG) circuit 170 in communication with a plurality of ECG leads
172. The ECG circuit 170 and the ECG leads 172 obtain electrical
signals from the surface of a patient's body and configure the
signals for display as an ECG waveform on the display 134 of the
external device 102.
[0055] The external device 102 also comprises a telemetry CPU 164
and a telemetry circuit 166, which establish the telemetric link
104 in cooperation with the IPG 10. The telemetric link 104
comprises a bidirectional link to enable the external device 102
and the IPG 10 to exchange data and/or commands. As previously
noted, the establishment of the telemetric link 104 is in certain
embodiments facilitated by a wand or programmer head, which is
placed in proximity to the IPG 10. The wand or programmer head
facilitates establishment of the telemetric link 104 by placing an
antenna structure in a closer proximity to the IPG 10 to facilitate
conduction of transmitted signals to the external device 102.
[0056] The telemetric link 104 can in some embodiments comprise a
variety of communication protocols appropriate to the needs and
limitations of a given application. In certain embodiments, the
telemetric link 104 comprises radio frequency (RF) telemetry. In
one particular embodiment, the telemetric link 104 comprises a
frequency modulated digital communication scheme wherein logic ones
are transmitted at a first frequency A and logic zeros are
transmitted second frequency B. As the IPG 10 is powered by a
battery having limited capacity and in certain embodiments the
external device 102 is powered by line voltage, e.g., not subject
to the stringent power limitations of the IPG 10, the bidirectional
telemetric link 104 can proceed in an asymmetric manner. For
example, in one embodiment, a transmission power and data rate from
the external device 102 to the IPG 10 via the telemetric link 104
can proceed at higher power levels and/or higher data transmission
rates than the reciprocal data rates and transmission power from
the IPG 10 to the external device 102. The telemetry circuit 100 of
the IPG 10 as well as the telemetry circuit 166 and CPU 164 of the
external device 102 can select or be adjusted to provide a desired
communication protocol and transmission power.
[0057] FIG. 4 shows an example of a remote monitoring system
comprising a home location 405 and a medical facility 445 connected
over a network 450. The home location includes a patient 400 with
an implanted pulse generator 10 which in this implementation is an
implanted cardiac stimulation device. IPG 10 collects data
indicative of the activity of the heart of patient 400, as
described above with reference to FIGS. 1 and 2. Home location 405
further includes a remote monitoring unit 410. RMU 410 may be an
external device 102 as described above with reference to FIG. 3,
but may be specifically adapted for use in a home, office, or other
location outside a typical medical setting. RMU 410 periodically
communicates with the IPG 10 implanted in the patient 400 in order
to upload cardiac data collected by the IPG 10.
[0058] Data collected by the IPG 10 and transferred to the RMU 410
may be transferred over a network 450. In some embodiments, network
450 corresponds to the Internet. In other embodiments, network 450
comprises a local area network. For example, network 450 may
comprise a local area network in a hospital or other medical
facility. In still other embodiments, network 450 corresponds to a
direct connection between computing devices, a wireless network, or
the like.
[0059] Data transferred over the network 450 may further be stored
on a server 420. Server 420 may comprise any computing device
capable of communicating over network 420, such as a personal
computer or blade server. In some embodiments, server 420 may store
and operate a hospital or medical database system that contains
patient data and records. The server may include software that
allows access to the database system by certain medical
professionals 440 and by the RMU 410.
[0060] A monitoring station 430 located at medical facility 445
accesses the data stored on server 420 over the network 450. In
some other embodiments, monitoring station 430 may download patient
data directly from the RMU 410. Monitoring station 430 obtains the
patient data stored on server 420 and displays the data to a
physician or clinician 440. A physician or clinician 440 may use
monitoring station 430 in order to view some or all the patient
data according to the display software of the monitoring station
430. Monitoring station 430 may have some or all of the same
functionality of the external device 102 shown in FIG. 3. For
example, monitoring station 430 may not include a telemetry circuit
166 in some embodiments. In some embodiments, monitoring station
430 further comprises other features, such as an alarm or ethernet
port.
[0061] While the system shown in FIG. 4 conveniently allows for the
transfer of information from an IPG 10 to a medical provider
without requiring the patient 400 to travel to the medical facility
445, the transfer of information from implanted IPG 10 to RMU 410
requires more power consumption than the standard operation of
implanted IPG 10 because the transmitter must be powered. As more
data is transferred from implanted IPG 10, and at a higher
frequency, the amount of power required by this process increases.
As that occurs, the useful life of the implanted IPG 10 decreases.
When the batteries are near or at their depleted levels the user
must have them replaced, which may involve invasive surgery. Thus,
it is desired that the battery life of the IPG 10 be extended as
much as possible.
[0062] However, the less frequent download of data sensed by the
implanted IPG 10 increases the likelihood that a major event, such
as a patient medical condition or a device failure, will not be
detected by the remote monitoring unit 410 and the relevant
information sent to clinician or physician 440 until it is too late
to provide patient 400 with the necessary treatment. Current
systems may have this problem, because they operate on periodic
cycles of set times. Thus, whether data is downloaded once per
week, once per day, or once per hour, there is a significant amount
of time between downloads. If a patient 400 experiences a medical
emergency or there is a device failure shortly after a download
occurs, then the next scheduled download will not occur for a
relatively long time. If the patient 400 is not aware of this event
or is unable to contact a physician 440 or other emergency medical
technician for assistance, the necessary medical attention may not
be received.
[0063] According to some embodiments, these problems related to
battery life and critical events are substantially reduced. For
example, according to some embodiments, the battery life of an IPG
10 may be extended by only downloading information that reflects a
significant change, or only downloading information related to the
occurrence of an event. When the time period for the scheduled
download occurs and there is not significant information to
download, the download can be limited so as to minimize unnecessary
battery depletion.
[0064] Alternatively, in order to provide efficient and fast
assistance during a significant event, a system is provided for
causing the IPG 10 to transfer information to the RMU 410 after the
occurrence of an event and as soon as the implanted IPG 10 is in
range of the RMU 410 rather than waiting for a download period.
Thus, as will be described in more detail below, the more efficient
and intelligent monitoring of data collected by an IPG 10 is
achieved according to some embodiments of the current
invention.
[0065] FIG. 5 is a flow chart describing a process 500 for the
efficient collection and analysis of data sensed by an IPG 10
according to one embodiment. The process 500 may be utilized, for
example, by an IPG 10 when sensing data indicative of the activity
of a patient's heart 12 and communicating with an RMU 410.
[0066] The process 500 begins at state 501 where the IPG 10
monitors heart and device activity. For example, the IPG 10 may
monitor the electrical activity of the patient's heart 12 as sensed
by VL tip electrode 26, the VR tip electrode 32, or AR tip
electrode 22. IPG 10 may further sense data such as pressure data,
movement data, impedance measurements, battery life, or the like.
Based on the monitored heart and device activity, the IPG 10 may
determine the occurrence of an event. An event may include a
medical event, such as an arrhythmia, or the like. An event may
also include a device event such a dislodged or damaged lead or a
low battery.
[0067] The process 500 continues to decision state 502. At decision
state 502 the IPG 10 determines if a recordable event has been
detected. In some embodiments, parameters determining what
constitutes a recordable event are programmed, for example, by a
physician using an external programmer 102. In some embodiments,
any event detected by IPG 10 is recordable. In other embodiments
only a limited number of events are recorded to preserve limited
memory space. If it is determined that its decision state 502 that
a recordable event has occurred, then the process 500 proceeds to
state 503. Otherwise the process 500 continues to state 509.
[0068] At 503, the detected event is recorded and stored in the
memory 94 of the IPG 10. In some embodiments, data collected by the
IPG 10 is stored in the memory 94 for predetermined amount of time
before being erased. In such embodiments, when it is determined at
decision state 502 a recordable event has occurred, then the IPG 10
may prevent data representing that event from being erased from
memory 94. In some embodiments, certain events may be detected at
their outset and recorded and stored in memory 94 only after they
have been detected. In some embodiments, only an indicator that an
event has occurred is stored, rather than the data surrounding the
event. For example, a low battery event might cause an indication
of the low battery to be stored rather than measured data.
Similarly, the incident of a capture threshold may be recorded
rather than measured amplitude.
[0069] The process 500 then continues to decision state 504. At
decision state 504 it is determined whether the recorded event
constitutes a high risk or emergency event. A high risk or
emergency event may be determined by the IPG 10 based on
predetermined factors. In some embodiments, these factors are
programmed using an external programmer 102 by a physician. High
risk or emergency events may represent, for example, a medical
condition that requires immediate medical attention in order to
prevent patient injury or death such as the occurrence of a new
type of heart arrhythmia or the occurrence of particularly severe
or frequent heart arrhythmias. A high risk event may also
correspond to a device malfunction or condition requiring immediate
medical attention, such as a very low battery life or a broken or
dislodged lead. If it is determined at decision state 504 that the
recorded event is not a high risk or emergency event, then the
process 500 continues to state 509. If it is determined at decision
state 504 that the recorded event constitutes a high risk or
emergency event, then the process 500 continues to state 505.
[0070] At state 505, the IPG 10 disables the flag of the event flag
module 123. Although in the description of process 500 only one
flag is utilized, it is understood that in other embodiments
multiple flags may be used by IPG 10. For example, certain flags
may indicate different types of conditions. For example, one flag
may indicate a device malfunction and another flag may indicate a
medical condition. In some embodiments, a number of flags may be
used and may be programmed by a physician using an external
programmer 102. The flag disabled at state 505 signifies that at
least one type of high risk or emergency event has occurred since
the last data download by the RMU 410.
[0071] The process 500 then continues to decision state 506. At
decision state 506, it is determined whether the IPG 10 is
connected to RMU 410 over a wireless communications link 104. If
the IPG 10 is in range of the RMU 410 and is connected, then the
process 500 proceeds to state 508. If the RMU 410 is not connected
to the IPG 10, then the process 500 continues to state 507. At
state 507 of the process 500, the IPG 10 waits and attempts to
connect with the RMU 410. For example, the IPG 10 may wait until
the RMU 410 is within range. For example, a patient having an IPG
10 may have an RM 410 located in his or her home. If the patient is
away from the home when an event is detected, then the IPG 10 will
connect with the RMU 410 when the patient returns home and is
within range of the RMU 410 such that the IPG senses the proximity
of the RMU, e. g. by receiving a polling signal from the RMU 410.
In some embodiments, the IPG 10 continues to record data related to
the current activity of the patient's heart 12 or the IPG 10. The
process 500 then continues to state 508. At state 508, the IPG 10
which is connected to the RMU 410 transmits the notification of the
high risk or emergency event determined at decision state 504 to
the RMU 410.
[0072] The IPG 10 then proceeds to perform a full download of the
data stored in the memory 94 of the IPG 10 to the RMU 410. In some
embodiments, all of the data stored in the memory 94 is downloaded
by the RMU 410 during a full download. In other embodiments, only
data related to the changed data or a significant event is
downloaded. In some embodiments, the data to be downloaded is
determined based on one or more indicators or flags 123. Process
500 continues from state 513 to state 514 where the flag of the
event flag module 123 is reset. The set flag indicates in some
embodiments that a full data download has occurred, and that no
major events have occurred since that time.
[0073] Returning to decision state 502, if no recordable event is
detected, then the process 500 continues to decision state 509. At
decision state 509 it is determined whether or not a scheduled
download should occur. A scheduled download may be determined by
the IPG 10 or by the RMU 10. In some embodiments, an external
programmer 102 is used by a physician to program a download
schedule into the memory 94 of the IPG 10. In some embodiments, a
download schedule is maintained by the RMU 410 and the IPG 10
determines at decision state 509 whether a scheduled download
should occur based upon whether or not a query has been received
from the RMU 410. If no scheduled download should occur, then the
process 500 returns to state 501 and continues sensing monitored
heart and device activity. Of course, in some embodiments, the IPG
10 continues to monitor heart and device activity throughout the
process 500 for all the steps recited herein. If a download is
determined to be scheduled at decision state 509, then the process
500 continues to decision state 510.
[0074] At decision state 510 it is determined whether or not a
significant change in stored data has occurred. The IPG 10 may
determine whether significant change in data has occurred by
analyzing data stored in memory 94 of the IPG 10. The data stored
in memory 94 may be compared and analyzed, based upon, for example,
criteria programmed by a physician using an external programmer
102. For example, a significant change in stored data may be
determined to have occurred if a certain number of events have
occurred. In some embodiments, IPG 10 may determine whether certain
threshold values for a heart rate or other sensed data have been
crossed in order to determine whether significant change in stored
data has occurred. If no significant change in stored data has
occurred since the previous download, then the process 500 returns
to state 501 and the IPG 10 continues to monitor heart and device
activity. If a significant change in stored data has occurred at
decision state 510, then the process 500 continues to decision
state 511.
[0075] At decision state 511 it is determined whether or not the
IPG 10 is connected to RMU 410. As explained with respect to
decision state 506 above, this step comprises determining whether
or not the RMU 410 is in range and the communication link 104 has
been established. If no such link 104 has been established at
decision state 511, then the process 500 continues to state 512. If
a link 104 has been established, then the process 500 continues to
state 513. At 512, the process 500 waits and attempts to connect
the IPG 10 with the RMU 410.
[0076] When the IPG 10 is connected with the RMU 410 at state 511
or 512, then the process 500 continues to state 513 where a full
interrogation or download occurs. Sensed data stored in memory 94
of the IPG 10 is transmitted to the RMU 410 as described above. In
some embodiments, all of the data stored in memory 94 of the IPG 10
is transmitted to the RMU 410. In some embodiments, sensed data is
transmitted to the RMU 410 but certain other data including
configuration data and settings are not transmitted to the RMU 410.
In some embodiments, the data transmitted to the RMU 410 is
determined in part based upon whether a high risk event has
occurred or whether a significant change has occurred, as well as
the specific sensed data corresponding to the events or changes.
For example, if multiple flags are used with the IPG 10, then the
data downloaded from memory 94 may be determined in part based upon
which flags are disabled.
[0077] The process 500 then continues to state 514 where the flag
of event flag module 123 is reset. The reset flag indicates the
data in memory 94 has been downloaded by the RMU 410 since the last
event has occurred. The process 500 then returns to state 501 and
the IPG 10 continues to monitor heart and device activity.
[0078] While the process 500 describes the operation of the IPG 10
according to some embodiments, the RMU 410 also may perform some of
the steps shown in FIG. 5 and provide additional functionality.
FIG. 6 is a flow chart describing a process 600 for the efficient
monitoring of cardiac data collected by an IPG 10 according to one
embodiment. The process 600 may be utilized, for example, by an RMU
410 at periodic intervals to collect data from an implanted IPG 10
when there has been a significant change in the data stored in the
memory 94 of the implanted IPG 10, or when an event has
occurred.
[0079] The process 600 begins at state 601 when the remote
monitoring unit 410 recognizes the implanted pulse generator 10 and
establishes a communications link 104. In a preferred embodiment,
the RMU 410 attempts to perform the process 600 at periodic
intervals, such as once each day or once each week. Of course,
other periods may be set between attempted downloads according to
the process 600. In the event that the IPG 10 is outside of the
range of the RMU 410 or for some other reason the RMU 410 cannot
open a communications channel with the IPG 10 at the scheduled
time, then the RMU 410 may continue to attempt to establish contact
until it is successful. The communications link 104 between the RMU
410 and the IPG 10 may comprise any type of wireless transmission,
protocol such as RF transmissions, as discussed above. At state
601, the IPG 10 is in a low power consumption mode, because the IPG
10 is not transferring significant amounts of data to the RMU 410,
but has merely verified its presence and opened a wireless channel
with the RMU 410.
[0080] At state 602, the RMU 410 reads the flag 123 in the IPG 10.
The flag 123 may be in either an enabled or disabled condition. In
general, an enabled flag condition corresponds to the flag being
set and indicates that no event has occurred since the previous
data download by the RMU 410. A disabled flag condition indicates
that between the time that the RMU 410 last downloaded data from
the IPG 10, an event has occurred that triggered the microprocessor
60 of the IPG 10 to disable the flag 123. An event may comprise a
medical condition in some embodiments, such as a supraventricular
tachycardia, atrial fibrillation, any other arrhythmia, or some
other condition that may require medical assistance. In some
embodiments, an event may comprise a current or imminent device
failure, such as a low battery power level in the IPG, a dislodged
lead, or the like. While this state has been discussed with
reference to a single flag, the IPG 10 may store multiple flags 123
corresponding to different conditions. For example, the IPG 10 may
store one flag 123 related to the occurrence of a patient medical
condition and another flag 123 related to the occurrence of an
equipment malfunction. In some embodiments, multiple flags
correspond to multiple medical conditions, such as one for a high
ventricular rate episode, one corresponding to a high atrial rate
episode, and any others that may be useful in distinguishing
events.
[0081] At decision state 603, if the flag is set, corresponding to
an enabled condition, then the process 600 continues to state 604.
If the flag is not set, corresponding to a disabled condition, then
the process 600 continues to state 606.
[0082] At state 604, the RMU 410 reads other data stored in the
memory 94 of IPG 10. The other data read at state 604 may comprise
a subset of the data stored in the memory of IPG 10. For example,
the subset of data may indicate whether or not there has been
significant change in the larger collection of cardiac data stored
by the IPG 10. A significant change in the data stored by IPG 10
may comprise a change in the average heart rate, the occurrence of
electrical stimulation therapy, or the like. The transmitting of
the subset of data may require more power than only reading the
flag 123, but may require substantially less power than a full
download.
[0083] At decision state 605, based on the subset of data read at
state 604, it is determined by the RMU 410 whether a significant
change has occurred in the larger collection of cardiac data since
the last download. What constitutes a significant change may be
determined by a physician in some embodiments. If it is determined
that a significant change has occurred, the process continues to
state 606. If a significant change has not occurred, then the
process continues to state 609.
[0084] The process 600 reaches state 606 if the flag 123 is not set
as determined at decision state 603 or there has been significant
change in the data stored in the IPG 10 as determined at decision
state 605. At state 606, a full interrogation or download of the
data stored in the memory 94 of the IPG 10 is performed. During
state 606, the IPG may transfer data collected that is related to,
for example, electrical signals generated by the heart, pulses and
other therapeutic stimulation provided by the IPG 10, impedance
measurements sensed by the IPG 10, or the like. In some embodiments
utilizing multiple flags 123, having one flag 123 that is in a
disabled condition may initialize a full download. In some
embodiments, having less than all of the flags 123 in a disabled
condition may cause the RMU 410 to download data related to the
events indicated by any of the flags 123 in a disabled condition,
but not to download data related to the flags 123 in an enabled
condition. A download at state 606 represents a high power
consumption mode for the IPG 10, and therefore some embodiments of
the current invention allow for the efficient use of this process
by downloading the full set of data only when it is necessary,
rather than at every scheduled period.
[0085] After data has been downloaded to the RMU 410, the process
600 continues to state 607. At state 607, the RMU 410 may transmit
data collected during the download process to server 420. In some
embodiments, server 420 may store a collection of medical data and
may be accessible by a monitoring station 430 located at a medical
facility 445 through a network 450. In some embodiments, the data
downloaded at state 606 and transmitted to the server 420 at state
607 is read by the server 420 to determine if the data indicates an
event requiring an alarm or other notification be sent to a
physician 440 or any other emergency technician at the medical
facility 445. If it is determined that a condition exists
warranting an alarm be sent, then alarm data is transferred to the
monitoring station 430 and is displayed to a physician or clinician
440 at that location. The alarm data may induce the monitoring
station to sound an audio alarm, display a visual alarm or message,
or the like. In some embodiments, an alarm may comprise an e-mail,
SMS text message, voice message sent electronically or over an
automated telephone system, pager, fax, or the like. In some
embodiments, the server 420 may continue to send an alarm until an
acknowledgement is received such as by return e-mail or SMS text
message.
[0086] In some embodiments, an alarm may be provided on the RMU 410
itself. This may be beneficial, for example, where a patient 400 is
living with a care provider. In this case, the alarm, whether it is
an audio alarm or visual alarm, may alert a care provider to the
patient's condition and possible need for assistance. In some
embodiments, an error code determined by analyzing the data
downloaded from the IPG 10 is used to determine a specific alarm
output by the RMU 410. In some embodiments, this error code may be
transmitted with the data at state 607.
[0087] The process 600 continues at state 608, where the flag 123
in the IPG 10 is set by the RMU 410. The flag 123 indicates that
the data contained in the IPG 10 has been downloaded. With the flag
in an enabled condition, as set at state 608, the RMU 410 will not
download data from the IPG 10 until the next scheduled download
period, and then only if significant change in the data has
occurred. State 608 is shown occurring after state 607. However, in
some embodiments, state 608 may occur substantially simultaneously
with state 607 or before state 607. Once the data has been
transmitted to the RMU 410 at state 606, and the flag has been set
at state 608, then the IPG 10 returns to a low power state because
it is no longer transferring the collected data. The process 600
then continues to state 609.
[0088] At state 609, the RMU 410 continues to maintain a
communications link 104 with the IPG 10. This link 104 may be
maintained as long as the IPG 10 is within the wireless
communications range of the RMU 410. In some embodiments, this
communications channel is only maintained as long as a
predetermined percentage of data transfer attempts are successful
in order to avoid the need to use battery life retransmitting
previously sent data that was lost during transmission. When the
IPG 10 is in range, maintaining the handshake with the IPG requires
only a low power consumption and allows the RMU 410 to maintain
efficient contact with the IPG 10.
[0089] The process 600 next continues to decision state 610. At
decision state 610, it is determined whether the established
communication link 104 between the RMU 410 and the IPG 10 has been
broken. If it is determined that the link 104 has not been broken,
then the process 600 returns to state 602 and reads the flag 123 of
the IPG 10 at the next scheduled download. If it is determined that
the communications link between the RMU and the IPG 10 has been
broken at state 610, then the RMU waits to reestablish the
communication link 104 with the IPG at state 611. When it is
determined at state 611 that the communications link 104 with the
IPG can be reestablished, then the process returns to state
601.
[0090] The process 600 described above therefore allows for the
efficient periodic download of data stored on IPG 10 to a remote
monitoring unit 410. Downloads occur at a periodic interval, but
only on the condition that a flag has been disabled indicating that
an event has occurred, or if there has been a significant change in
the stored data. Thus, data indicating the continued normal
operation of the IPG 10 is not downloaded. This allows the IPG 10
to transmit data stored in memory 94 only when necessary. This, in
turn, preserves the battery life of the IPG 10 because power is not
wasted broadcasting unnecessary information.
[0091] FIG. 7 shows an embodiment of a process 700 for downloading
information stored in the IPG 10 when an event occurs between the
scheduled download times. The process 700 advantageously allows for
the nearly immediate download of data after an event has occurred
if the IPG 10 is in range of the RMU 410.
[0092] The process 700 begins at state 701, where the RMU 410
recognizes the IPG 10 and establishes a communications link 104.
The link 104 may be established, for example, when the patient
enters an area within the broadcasting range of the RMU 410. For
example, this range may correspond approximately with the patient's
home. In some embodiments, multiple RMUs 410 may be located at
different locations including a home, office, coffee shop, or the
like. After a link has been established in state 701, the process
continues to state 702.
[0093] At state 702, the RMU 410 reads flag 123 of the IPG 10. As
discussed in more detail above with respect to process 600, in some
embodiments multiple flags 123 may be stored in the IPG 10 and read
by RMU 410. When multiple flags 123 are used, any or some
combination of the flags 123 being disabled may trigger a complete
download. In some embodiments, each of the multiple flags 123 may
correspond to a type of event and determine whether data stored by
IPG 10 related to that event is downloaded. If it is determined at
state 703 that the flag 123 is set corresponding to an enabled
condition, then the process continues to state 709 without
performing any download of data. If it is determined at state 703
that the flag 123 is not set, corresponding to a disabled
condition, then the process 700 continues to state 706 and a full
interrogation or download is performed. At state 706, the sensed
data indicative of cardiac activity or device performance or
condition and stored in the memory 94 of the IPG 10 is transferred
from the IPG 10 to the RMU 410.
[0094] At state 707, the RMU 410 transmits the data collected from
the IPG 10 to server 420. Server 420 may determine that an alarm
should be sent to medical facility 445 indicating that an event has
occurred, such as a patient medical condition or a device
malfunction. An alarm may be provided on monitoring station 430 to
indicate to a physician 440 or other emergency medical technician
that patient 400 may need assistance. An alarm may additionally be
provided on RMU 410 indicating an event in some embodiments. As
discussed in more detail above, an alarm may be provided at the
medical facility 445, the RMU 410, or be sent by some other method
to a physician 440.
[0095] At state 708, the flag 123 is set in the IPG 10. The set
flag indicates that the data stored in the IPG 10 has been
downloaded by the RMU 410. Thus, when an event occurs, the flag
123, having been disabled by the IPG 10, will indicate to the RMU
410 that a download is necessary. At state 708, after a download
has occurred and the information related to the event has been
obtained by the RMU 410, then the flag 123 will again be set
indicating that no further download is necessary at that time. In
this way, the amount of energy used to transmit information from
the IPG 10 to the RMU 410 is reduced while allowing for a quick
emergency response. In this embodiment, only the information that
needs to be transferred is transferred, but that information is
transferred as soon as it is needed.
[0096] If the flag is set at state 703, or after the flag is set by
the RMU 410 at state 708, the process 700 continues to state 709.
At state 709, the RMU 410 continues the communications link 104 and
handshake protocol established at state 701 with the IPG 10.
[0097] At decision state 710, if it is determined that the link 104
has not been broken, then the process 700 returns to state 702 and
reads the flag. In some embodiments, this may entail a short wait
that is not likely to endanger the patient 400. For example, the
RMU 410 may wait five minutes, one minute, or less than a minute
between attempts to read the flag 123. This process 700 may occur
in some embodiments as long as the IPG 10 is within range of the
transmitter of the RMU 410. If it is determined at state 710 that
the link 104 has been broken, then the process continues to state
711 where the RMU waits to reestablish the communications link with
the IPG 10. When the IPG 10 is again detected, the process 700
returns to state 701 and establishes the link 104. Thus, according
to this embodiment, whenever the RMU 410 is in range of the IPG 10,
a communications link 104 is established. If an event occurs while
a communications link 104 is established, such as a medical
emergency or a device failure, then the IPG 10 disables a flag
condition, causing the RMU 410 to determine that data should be
downloaded from the IPG 10.
[0098] As can be seen, various embodiments described herein provide
a number of advantages over the prior art. For example, according
to some embodiments of the invention, a remote monitoring unit may
advantageously monitor data stored in an implanted device over
periodic intervals, but only perform a full download when the data
has changed significantly. This may allow for the more efficient
use of the implanted device battery and longer device life span.
According to some embodiments of the invention, a remote monitoring
unit may continually be in contact and in communication with an IPG
whenever the IPG is within range of the RMU. Advantageously, the
IPG may operate in a low power state during this communication
while it is not downloading or transferring any information from
the device memory to the RMU. Only when an event occurs and the IPG
sets a flag will a data download be initiated. Thus, the system
advantageously allows for the nearly immediate download of data
related to the occurrence of a significant event, such as a medical
emergency or device failure. It will be understood that not all of
the advantages described herein may be achieved in each embodiment
of the invention. Furthermore, advantages not specifically
discussed may nonetheless be achieved by some embodiments as taught
herein. Nonetheless, those embodiments may be practiced without
departing from the spirit of the invention. An artisan of ordinary
skill will also understand that while reference is made to the
monitoring of cardiac activity by an IPG, other implantable devices
that sense other aspects of a patient's medical condition and
transmit sensed data to a monitoring computer may be utilized in
order to accomplish certain advantages described herein without
departing from the scope of the invention. For example, certain
aspects disclosed herein may be utilized with implantable glucose
monitors, or the like.
[0099] The methods and steps described herein describe particular
embodiments, and are not limiting. An artisan of ordinary skill
will understand that certain steps described herein may be removed
or performed in a different order, and other steps not described
may be added. Furthermore, the steps are generally described as
being performed by a remote monitoring unit, but certain steps may
be implemented utilizing either hardware components or software
instructions in any computing device.
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