U.S. patent application number 13/010720 was filed with the patent office on 2011-07-28 for non-rechargeable batteries and implantable medical devices.
Invention is credited to Kevin Wilmot Eberman, Lawrence Robert Heyn.
Application Number | 20110184482 13/010720 |
Document ID | / |
Family ID | 43743466 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110184482 |
Kind Code |
A1 |
Eberman; Kevin Wilmot ; et
al. |
July 28, 2011 |
NON-RECHARGEABLE BATTERIES AND IMPLANTABLE MEDICAL DEVICES
Abstract
A non-rechargeable battery comprising: an anode; a cathode
comprising a binder comprising styrene-butadiene rubber; a
separator between the anode and the cathode; and an electrolyte
contacting the anode, the cathode, and the separator. Such
batteries can be used in implantable medical devices.
Inventors: |
Eberman; Kevin Wilmot; (St.
Paul, MN) ; Heyn; Lawrence Robert; (Maple Grove,
MN) |
Family ID: |
43743466 |
Appl. No.: |
13/010720 |
Filed: |
January 20, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61297808 |
Jan 24, 2010 |
|
|
|
Current U.S.
Class: |
607/5 ;
429/217 |
Current CPC
Class: |
H01M 2004/021 20130101;
H01M 4/38 20130101; H01M 4/06 20130101; H01M 2220/30 20130101; H01M
2004/028 20130101; H01M 6/40 20130101; Y02P 70/50 20151101; A61N
1/362 20130101; Y10T 29/49115 20150115; H01M 4/502 20130101; H01M
6/14 20130101; A61N 1/3787 20130101; H01M 4/625 20130101; A61N
1/378 20130101; H01M 10/052 20130101; H01M 4/582 20130101; H01M
4/587 20130101; H01M 10/4264 20130101; H01M 4/364 20130101; H01M
16/00 20130101; A61N 1/3975 20130101; A61N 1/3956 20130101; A61N
1/39622 20170801; H01M 4/382 20130101; H01M 4/134 20130101; H01M
4/133 20130101; A61B 5/363 20210101; H01M 4/622 20130101; Y02E
60/10 20130101; H01M 6/16 20130101; H01M 4/131 20130101; H01M 4/485
20130101; H01M 4/54 20130101; H01M 2004/027 20130101 |
Class at
Publication: |
607/5 ;
429/217 |
International
Class: |
A61N 1/39 20060101
A61N001/39; H01M 4/62 20060101 H01M004/62 |
Claims
1. A non-rechargeable battery comprising: an anode; a cathode
comprising a binder comprising styrene-butadiene rubber; a
separator between the anode and the cathode; and an electrolyte
contacting the anode, the cathode, and the separator.
2. The battery of claim 1, wherein the cathode comprises a silver
vanadium oxide.
3. The battery of claim 2, wherein the cathode comprises a mixture
of two or more materials.
4. The battery of claim 3, wherein the cathode material further
comprises carbon monofluoride.
5. The battery of claim 1, wherein the cathode comprises carboxy
methyl cellulose.
6. An implantable medical device comprising a battery of claim
1.
7. The implantable medical device of claim 6 which is an
implantable cardioverter defibrillator device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application Ser. No. 61/297,808, filed on Jan. 24, 2010,
which is incorporated herein by reference.
BACKGROUND
[0002] A wide variety of implantable medical devices (IMDs) for
delivering a therapy and/or monitoring a physiologic condition have
been clinically implanted or proposed for clinical implantation in
patients. Some implantable medical devices may employ one or more
elongated electrical leads and/or sensors. Such implantable medical
devices may deliver therapy or monitor the heart, muscle, nerve,
brain, stomach or other organs. In some cases, implantable medical
devices deliver electrical stimulation therapy and/or monitor
physiological signals via one or more electrodes or sensor
elements, which may be included as part of one or more elongated
implantable medical leads. Implantable medical leads may be
configured to allow electrodes or sensors to be positioned at
desired locations for delivery of stimulation or sensing. For
example, electrodes or sensors may be located at a distal portion
of the lead. A proximal portion of the lead may be coupled to an
implantable medical device housing, which may contain electronic
circuitry such as stimulation generation and/or sensing
circuitry.
[0003] For example, implantable medical devices, such as cardiac
pacemakers or implantable cardioverter defibrillators (ICDs),
provide therapeutic stimulation to the heart by delivering
electrical therapy signals such as pacing pulses, or cardioversion
or defibrillation shocks, via electrodes of one or more implantable
leads. In some cases, such an implantable medical device may sense
intrinsic depolarization of the heart, and control the delivery of
such signals to the heart based on the sensing. When an abnormal
rhythm is detected, such as bradycardia, tachycardia or
fibrillation, an appropriate electrical signal or signals (e.g., in
the form of pulses) may be delivered to restore the normal rhythm.
For example, in some cases, an implantable medical device may
deliver pacing, cardioversion or defibrillation signals to the
heart of the patient upon detecting ventricular tachycardia, and
deliver cardioversion or defibrillation electrical signals to a
patient's heart upon detecting ventricular fibrillation.
[0004] Also, implantable medical devices, such as electrical
stimulators or therapeutic agent delivery devices, may be used in
different therapeutic applications, such as deep brain stimulation
(DBS), spinal cord stimulation (SCS), pelvic stimulation, gastric
stimulation, peripheral nerve stimulation or delivery of a
pharmaceutical agent, insulin, a pain relieving agent, or an
anti-inflammatory agent to a target tissue site within a patient. A
medical device may be used to deliver therapy to a patient to treat
a variety of symptoms or patient conditions such as chronic pain,
tremors, Parkinson's disease, other types of movement disorders,
seizure disorders (e.g., epilepsy), urinary or fecal incontinence,
sexual dysfunction, obesity, mood disorders, gastroparesis or
diabetes. In some cases, the electrical stimulation may be used for
muscle stimulation, e.g., functional electrical stimulation (FES)
to promote muscle movement or prevent atrophy. In some therapy
systems, an implantable electrical stimulator delivers electrical
therapy to a target tissue site within a patient with the aid of
one or more medical leads that include electrodes. In addition to
or instead of electrical stimulation therapy, a medical device may
deliver a therapeutic agent to a target tissue site within a
patient with the aid of one or more fluid delivery elements, such
as a catheter.
SUMMARY
[0005] The present disclosure is directed to implantable medical
devices, implantable medical device systems that include such
implantable medical devices, and implantable medical device
batteries, as well as methods of making. Such devices can include a
battery of relatively small volume but of relatively high power
(reported as therapeutic power) and relatively high capacity
(reported as capacity density), although this is not a requirement
of all embodiments of the present disclosure.
[0006] In one embodiment, the present disclosure provides a
non-rechargeable battery comprising: an anode; a cathode comprising
a binder comprising styrene-butadiene rubber (SBR); a separator
between the anode and the cathode; and an electrolyte contacting
the anode, the cathode, and the separator. This battery may be of
relatively small volume but of relatively high power (reported as
therapeutic power) and relatively high capacity (reported as
capacity density). Such batteries can be used in any of the
following embodiments.
[0007] In one embodiment, the present disclosure provides an
implantable cardioverter defibrillator device comprising: control
electronics for delivering therapy and/or monitoring physiological
signals, the control electronics comprising: a processor; memory; a
stimulation generator that generates at least one of cardiac pacing
pulses, defibrillation shocks, and cardioversion shocks; and a
sensing module for monitoring a patient's heart rhythm; one or more
defibrillator capacitors; and an implantable medical device battery
operably connected to the control electronics to deliver power to
the control electronics, and operably connected to the capacitors
to charge the capacitors (although the battery is not directly
connected to the capacitors, it is connected to a charging circuit,
thereby being operably connected to the capacitors); wherein the
battery has a total volume of no greater than 6.0 cubic centimeters
(cc), the battery comprising: an anode comprising lithium; a
cathode having a total uniform thickness of less than 0.014 inch; a
separator between the anode and the cathode; and an electrolyte
contacting the anode, the cathode, and the separator; wherein the
cathode material comprises a metal oxide; wherein the battery has a
therapeutic power of at least 0.11 watt (W) for every joule of
therapeutic energy delivered over the useful life of the battery,
and a therapeutic capacity density of at least 0.08 ampere hour per
cubic centimeter (Ah/cc).
[0008] In another embodiment, the present disclosure provides an
implantable medical device comprising: control electronics for
delivering therapy and/or monitoring physiological signals, the
control electronics comprising: a processor; and memory; and an
implantable medical device battery operably connected to the
control electronics to deliver power to the control electronics;
wherein the battery has a total volume of no greater than 6.0 cc,
the battery comprising: an anode comprising lithium; a cathode
having a total uniform thickness of less than 0.014 inch; a
separator between the anode and the cathode; and an electrolyte
contacting the anode, the cathode, and the separator; wherein the
cathode material comprises a metal oxide; wherein the battery has a
therapeutic power of at least 0.11 W for every joule of therapeutic
energy delivered over the useful life of the battery, and a
therapeutic capacity density of at least 0.08 Ah/cc.
[0009] In another embodiment, the present disclosure also provides
an implantable medical device comprising: control electronics for
delivering therapy and/or monitoring physiological signals, the
control electronics comprising: a processor; and memory; and an
implantable medical device battery operably connected to the
control electronics to deliver power to the control electronics;
wherein the battery has a total volume of no greater than 6.0 cc,
the battery comprising: an anode comprising lithium; a cathode
comprising a single current collector (e.g., in any one cathode
plate) and having a total uniform thickness of less than 0.014
inch; a separator between the anode and the cathode; and an
electrolyte contacting the anode, the cathode, and the separator;
wherein the cathode material comprises a layer on each major
surface of the single current collector, wherein the layer
comprises a mixture comprising a metal oxide and carbon
monofluoride; wherein the battery has a therapeutic power of at
least 0.11 W for every joule of therapeutic energy delivered over
the useful life of the battery, and a therapeutic capacity density
of at least 0.08 Ah/cc.
[0010] The present disclosure also provides an implantable medical
device system comprising: an implantable medical device as
described above; and components operably attached to the
implantable medical device for delivering therapy and/or monitoring
physiological signals.
[0011] The present disclosure also provides an implantable medical
device battery comprising: an anode comprising lithium; a cathode
having a total uniform thickness of less than 0.014 inch; wherein
the cathode comprises a metal oxide and an SBR binder; a separator
between the anode and the cathode; and an electrolyte contacting
the anode, the cathode, and the separator; wherein the battery has
a therapeutic power of at least 0.11 W for every joule of
therapeutic energy delivered over the useful life of the battery,
and a therapeutic capacity density of at least 0.08 Ah/cc.
[0012] In certain embodiments of the present disclosure, the
battery volume is preferably no greater than 5.0 cc. Typically, in
such devices the battery volume is at least 3.0 cc.
[0013] In certain embodiments of the present disclosure, the
therapeutic power of the battery is at least 0.14 W for every joule
of therapeutic energy delivered over the useful life of the
battery.
[0014] In certain embodiments of the present disclosure, the
therapeutic capacity density of the battery is at least 0.10
Ah/cc.
[0015] In certain embodiments of the present disclosure, the
surface area of each of the cathode and anode is at least 60
cm.sup.2.
[0016] In certain embodiments of the present disclosure, the
cathode comprises a silver vanadium oxide. In certain embodiments,
the cathode comprises a mixture of two or more materials
(particularly, a mixture of a silver vanadium oxide and carbon
monofluoride).
[0017] In certain embodiments of the implantable devices of the
present disclosure, the cathode comprises a single current
collector (e.g., in any one cathode plate of a stacked
cathode).
[0018] In certain embodiments, the cathode is prepared from a
slurry coated onto a current collector. Such slurry coating method
can be used in making a cathode a battery of relatively small
volume but of relatively high power (reported as therapeutic power)
and relatively high capacity (reported as capacity density).
Preferably, the slurry includes a binder comprising
styrene-butadiene rubber.
[0019] The present disclosure also provides a method of making a
battery (preferably, an IMD battery), the method comprising:
preparing a cathode material slurry comprising an active cathode
material, a binder (preferably including styrene-butadiene-rubber),
an optional thickener and/or an optional dispersant, and a solvent;
applying the cathode material slurry to at least one major surface
of a current collector; removing the solvent from the coated
cathode slurry material to form a dry cathode coating; compressing
the dry cathode coating to reduce porosity and thickness of the
coating; and combining the cathode with an anode, one or more
separators, and an electrolyte to form a battery. Preferably, the
cathode material slurry comprises fibrous particles, and even more
preferably a mixture of fibrous particles with irregularly shaped
agglomerates of needle-shaped particles.
[0020] The term "components for delivering therapy and/or
monitoring physiological signals" refers to components of an IMD
system that deliver electrical stimulation therapy (e.g.,
functional electrical stimulation to promote muscle movement, or
stimulation to the heart using pacing pulses, cardioversion or
defibrillation shocks), deliver a therapeutic agent, monitor
physiological signals (e.g., detect ventricular fibrillation), or
both deliver and monitor (e.g., detect tachycardia and deliver
electrical signals to restore normal rhythm to the heart).
[0021] The term "total volume" in the context of battery volume
refers to the total overall volume of the battery, not the volume
of any individual cell. Although a battery may include one or more
individual cells, each of which includes a cathode, anode,
separator, and an electrolyte, the total volume is the summation of
the volumes of the individual cells.
[0022] The term "total uniform thickness" in the context of an
electrode refers to the total overall thickness of the electrode,
not the thickness of any individual layer (e.g., a layer of cathode
material or a layer of metal foil used as a current collector) if
the electrode is a layered construction. Furthermore, this
thickness is uniform along its length (excluding any uncoated areas
such as tabs or edges on individual electrode plates and the
portions of the electrode forming the outermost wraps or plates),
with tolerances of no more than .+-.0.003 inch (3 mil), and
preferably no more than .+-.0.001 inch (1 mil).
[0023] The term "surface area" in the context of an electrode
refers to the total area of the electrode (e.g., the area of the
active cathode material, which excludes any areas such as tabs or
edges, for example, on individual cathode plates that do not
include cathode material) excluding any area that is not opposing
the other electrode. For example, the surface area of a stacked
plate electrode is the summation of the surface areas of the
individual electrode plates joined electrically to form one
electrode but does not include the outermost surface of the two
electrode plates at each end of the stack.
[0024] The term "therapeutic capacity" refers to the total capacity
delivered until the cell power decreases to a specified wattage. In
this context, the "cell power" is the average voltage times the
average current, and the "specified wattage" is defined when the
average voltage=1.6 Volts (V). This "therapeutic capacity" differs
from anode capacity, cathode capacity, and cell capacity as
traditionally used in discussions of batteries, in that the latter
terms all refer to complete discharge of the respective
components.
[0025] The term "therapeutic capacity density" refers to the
battery's therapeutic capacity delivered over the useful life of
the battery divided by the battery volume.
[0026] The term "useful life" in the context of the battery life
refers to the longevity that is typical for conventional
implantable medical device batteries, which is on the order of
years. Preferably, the useful life is at least 5 years.
[0027] The term "therapeutic power" refers to the amount of cell
power (defined above in the context of therapeutic capacity) a
battery delivers for every joule of therapeutic energy delivered.
In this context, "therapeutic energy" is the amount of energy
delivered by a stimulation generator to a patient in a single
stimulation event. Examples of such an event include pacing,
cardioversion, and defibrillation. A "single" event is, for
example, one pacing shock, one defibrillation shock, or one
cardioversion shock.
[0028] The term "particle size" refers to the longest dimension of
a particle. For a spherical particle, this is the diameter.
[0029] The terms "comprises" and variations thereof do not have a
limiting meaning where these terms appear in the description and
claims.
[0030] The terms "preferred" and "preferably" refer to embodiments
of the disclosure that may afford certain benefits, under certain
circumstances. However, other embodiments may also be preferred,
under the same or other circumstances. Furthermore, the recitation
of one or more preferred embodiments does not imply that other
embodiments are not useful, and is not intended to exclude other
embodiments from the scope of the disclosure.
[0031] As used herein, "a," "an," "the," "at least one," and "one
or more" are used interchangeably. Thus, for example, a device that
comprises "a" capacitors can be interpreted to mean that the device
includes "one or more" capacitors.
[0032] As used herein, the term "or" is generally employed in its
sense including "and/or" unless the content clearly dictates
otherwise. The term "and/or" means one or all of the listed
elements or a combination of any two or more of the listed elements
(e.g., delivering therapy and/or monitoring physiological signals
means delivering therapy, monitoring physiological conditions, or
doing both monitoring and delivering).
[0033] Also herein, all numbers are assumed to be modified by the
term "about" and preferably by the term "exactly." Notwithstanding
that the numerical ranges and parameters setting forth the broad
scope of the disclosure are approximations, the numerical values
set forth in the specific examples are reported as precisely as
possible. All numerical value, however, inherently contain certain
errors necessarily resulting from the standard deviation found in
their respective testing measurements.
[0034] Also herein, the recitations of numerical ranges by
endpoints include all numbers subsumed within that range (e.g., 1
to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).
[0035] The above summary of the present disclosure is not intended
to describe each disclosed embodiment or every implementation of
the present disclosure. The description that follows more
particularly exemplifies illustrative embodiments. In several
places throughout the application, guidance is provided through
lists of examples, which examples can be used in various
combinations. In each instance, the recited list serves only as a
representative group and should not be interpreted as an exclusive
list.
BRIEF DESCRIPTION OF FIGURES
[0036] The figures presented herein are idealized, not to scale,
and are intended to be merely illustrative and non-limiting.
[0037] FIG. 1 is a conceptual diagram illustrating an exemplary
implantable medical device system (e.g., a therapy system) of the
present disclosure.
[0038] FIG. 2 is a conceptual diagram illustrating an IMD and leads
of a therapy system of the present disclosure in greater
detail.
[0039] FIG. 3 is a conceptual diagram illustrating another example
of an implantable medical device system (e.g., a therapy system) of
the present disclosure.
[0040] FIG. 4 provides further detail of an exemplary IMD of the
present disclosure.
[0041] FIG. 5 is block diagram of an exemplary programmer used with
an implantable medical device of the present disclosure.
[0042] FIG. 6 is a block diagram illustrating a system that
includes an external device, such as a server, and one or more
computing devices coupled to an IMD of the present disclosure, and
a programmer via a network 196.
[0043] FIG. 7A is a conceptual diagram illustrating an exemplary
implantable medical device system (e.g., a therapy system) that
provides electrical stimulation therapy to a patient according to
the present disclosure.
[0044] FIG. 7B is a conceptual diagram of another example of an
implantable medical device system (e.g., therapy system) that
delivers electrical stimulation to target tissue sites proximate to
the spine of a patient according to the present disclosure.
[0045] FIG. 8 is a functional block diagram of an exemplary IMD of
the present disclosure.
[0046] FIG. 9 is a functional block diagram of an exemplary
programmer used with an IMD of the present disclosure.
[0047] FIG. 10 is a cutaway perspective view of an IMD of the
present disclosure.
[0048] FIG. 11 is a cutaway perspective view of a battery in the
IMD of FIG. 10.
[0049] FIG. 12 is an enlarged view of a portion of the battery
depicted in FIG. 11 and designated by line 212.
[0050] FIG. 13-16 are graphs of therapeutic capacity density
relative to cell volumes for various batteries having various
therapeutic power capabilities.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0051] The present disclosure is directed to implantable medical
devices, implantable medical device systems that include such
implantable medical devices, and implantable medical device
batteries, as well as methods of making. Such devices can include a
battery of relatively small volume but of relatively high power
(reported as therapeutic power) and relatively high capacity
(reported as capacity density), although various embodiments of the
present invention do not require a battery of relatively small
volume, relatively high power, and relatively high capacity
(reported as capacity density). A wide variety of implantable
medical devices (IMDs) for delivering a therapy and/or monitoring a
physiologic condition have been clinically implanted or proposed
for clinical implantation in patients. Exemplary such IMDs include
implantable pulse generators (IPGs), implantable cardioverter
defibrillators (ICDs), neurostimulators, or other suitable devices.
Of particular importance are implantable cardioverter
defibrillators (ICDs).
[0052] Whether for electrical stimulation therapy, delivering a
therapeutic agent, and/or monitoring a physiological condition, for
certain embodiments of the present disclosure it is desirable to
reduce IMD battery volumes for both patient comfort and aesthetics,
while maintaining relatively high power capability and
capacity.
Exemplary Implantable Medical Devices and Systems
[0053] FIG. 1 is a conceptual diagram illustrating an exemplary
implantable medical device system (e.g., a therapy system) 10 that
may be used to provide therapy to heart 12 of patient 14. Patient
14 ordinarily, but not necessarily, will be a human. Therapy system
10 includes IMD 16, which is coupled to leads 18, 20, 22, and
programmer 24. IMD 16 may be, for example, an implantable
pacemaker, cardioverter, and/or defibrillator that provides
electrical signals to heart 12 via electrodes coupled to one or
more of leads 18, 20, and 22.
[0054] Leads 18, 20, 22 extend into the heart 12 of patient 14 to
sense electrical activity of heart 12 and/or deliver electrical
stimulation to heart 12. In the example shown in FIG. 1, right
ventricular (RV) lead 18 extends through one or more veins (not
shown), the superior vena cava (not shown), and right atrium 26,
and into right ventricle 28. Left ventricular (LV) coronary sinus
lead 20 extends through one or more veins, the vena cava, right
atrium 26, and into the coronary sinus 30 to a region adjacent to
the free wall of left ventricle 32 of heart 12. Right atrial (RA)
lead 22 extends through one or more veins and the vena cava, and
into the right atrium 26 of heart 12.
[0055] IMD 16 may sense electrical signals attendant to the
depolarization and repolarization of heart 12 via electrodes (not
shown in FIG. 1) coupled to at least one of the leads 18, 20, 22.
In some examples, IMD 16 provides pacing pulses to heart 12 based
on the electrical signals sensed within heart 12. The
configurations of electrodes used by IMD 16 for sensing and pacing
may be unipolar or bipolar. IMD 16 may also provide defibrillation
therapy and/or cardioversion therapy via electrodes located on at
least one of the leads 18, 20, 22. IMD 16 may detect arrhythmia of
heart 12, such as fibrillation of ventricles 28 and 32, and deliver
defibrillation therapy to heart 12 in the form of electrical
pulses. In some examples, IMD 16 may be programmed to deliver a
progression of therapies, e.g., pulses with increasing energy
levels, until a fibrillation of heart 12 is stopped. IMD 16 detects
fibrillation by employing one or more fibrillation detection
techniques known in the art.
[0056] In some examples, programmer 24 may be a handheld computing
device or a computer workstation. Programmer 24 may include a user
interface that receives input from a user. The user interface may
include, for example, a keypad and a display, which may, for
example, be a cathode ray tube (CRT) display, a liquid crystal
display (LCD) or light emitting diode (LED) display. The keypad may
take the form of an alphanumeric keypad or a reduced set of keys
associated with particular functions. Programmer 24 can
additionally or alternatively include a peripheral pointing device,
such as a mouse, via which a user may interact with the user,
interface. In some embodiments, a display of programmer 24 may
include a touch screen display, and a user may interact with
programmer 24 via the display.
[0057] A user, such as a physician, technician, or other clinician,
may interact with programmer 24 to communicate with IMD 16. For
example, the user may interact with programmer 24 to retrieve
physiological or diagnostic information from IMD 16. A user may
also interact with programmer 24 to program IMD 16, e.g., select
values for operational parameters of the IMD.
[0058] For example, the user may use programmer 24 to retrieve
information from IMD 16 regarding the rhythm of heart 12, trends
therein over time, or tachyarrhythmia episodes. As another example,
the user may use programmer 24 to retrieve information from IMD 16
regarding other sensed physiological parameters of patient 14, such
as intracardiac or intravascular pressure, activity, posture,
respiration, or thoracic impedance. As another example, the user
may use programmer 24 to retrieve information from IMD 16 regarding
the performance or integrity of IMD 16 or other components of
system 10, such as leads 18, 20, and 22, or a power source of IMD
16.
[0059] The user may use programmer 24 to program a therapy
progression, select electrodes used to deliver defibrillation
shocks, select waveforms for the defibrillation shock, or select or
configure a fibrillation detection algorithm for IMD 16. The user
may also use programmer 24 to program aspects of other therapies
provided by IMD 16, such as cardioversion or pacing therapies. In
some examples, the user may activate certain features of IMD 16 by
entering a single command via programmer 24, such as depression of
a single key or combination of keys of a keypad or a single
point-and-select action with a pointing device.
[0060] IMD 16 and programmer 24 may communicate via wireless
communication using any techniques known in the art. Examples of
communication techniques may include, for example, low frequency or
radio frequency (RF) telemetry, but other techniques are also
contemplated. In some examples, programmer 24 may include a
programming head that may be placed proximate to the patient's body
near the IMD 16 implant site in order to improve the quality or
security of communication between IMD 16 and programmer 24.
[0061] FIG. 2 is a conceptual diagram illustrating IMD 16 and leads
18, 20, 22 of therapy system 10 in greater detail. Leads 18, 20, 22
may be electrically coupled to a stimulation generator, a sensing
module, or other modules IMD 16 via connector block 34. In some
examples, proximal ends of leads 18, 20, 22 may include electrical
contacts that electrically couple to respective electrical contacts
within connector block 34. In addition, in some examples, leads 18,
20, 22 may be mechanically coupled to connector block 34 with the
aid of set screws, connection pins, or another suitable mechanical
coupling mechanism.
[0062] Each of the leads 18, 20, 22 includes an elongated
insulative lead body, which may carry a number of concentric coiled
conductors separated from one another by tubular insulative
sheaths. In the illustrated example, a pressure sensor 38 and
bipolar electrodes 40 and 42 are located proximate to a distal end
of lead 18. In addition, bipolar electrodes 44 and 46 are located
proximate to a distal end of lead 20 and bipolar electrodes 48 and
50 are located proximate to a distal end of lead 22. In FIG. 2,
pressure sensor 38 is disposed in right ventricle 28. Pressure
sensor 30 may respond to an absolute pressure inside right
ventricle 28, and may be, for example, a capacitive or
piezoelectric absolute pressure sensor. In other examples, pressure
sensor 30 may be positioned within other regions of heart 12 and
may monitor pressure within one or more of the other regions of
heart 12, or may be positioned elsewhere within or proximate to the
cardiovascular system of a patient to monitor cardiovascular
pressure associated with mechanical contraction of the heart.
[0063] Electrodes 40, 44 and 48 may take the form of ring
electrodes, and electrodes 42, 46 and 50 may take the form of
extendable helix tip electrodes mounted retractably within
insulative electrode heads 52, 54 and 56, respectively. Each of the
electrodes 40, 42, 44, 46, 48 and 50 may be electrically coupled to
a respective one of the coiled conductors within the lead body of
its associated lead 18, 20, 22, and thereby coupled to respective
one of the electrical contacts on the proximal end of leads 18, 20,
22.
[0064] Electrodes 40, 42, 44, 46, 48 and 50 may sense electrical
signals attendant to the depolarization and repolarization of heart
12. The electrical signals are conducted to IMD 16 via the
respective leads 18, 20, 22. In some examples, IMD 16 also delivers
pacing pulses via electrodes 40, 42, 44, 46, 48 and 50 to cause
depolarization of cardiac tissue of heart 12. In some examples, as
illustrated in FIG. 2, IMD 16 includes one or more housing
electrodes, such as housing electrode 58, which may be fowled
integrally with an outer surface of hermetically-sealed housing 60
of IMD 16 or otherwise coupled to housing 60. In some examples,
housing electrode 58 is defined by an uninsulated portion of an
outward facing portion of housing 60 of IMD 16. Other division
between insulated and uninsulated portions of housing 60 may be
employed to define two or more housing electrodes. In some
examples, housing electrode 58 comprises substantially all of
housing 60. Any of the electrodes 40, 42, 44, 46, 48 and 50 may be
used for unipolar sensing or pacing in combination with housing
electrode 58.
[0065] As described with reference to FIG. 4, housing 60 may
enclose a stimulation generator that generates cardiac pacing
pulses and/or defibrillation and/or cardioversion shocks, as well
as a sensing module for monitoring the patient's heart rhythm.
[0066] Leads 18, 20, 22 also include elongated electrodes 62, 64,
66, respectively, which may take the form of a coil. IMD 16 may
deliver defibrillation shocks to heart 12 via any combination of
elongated electrodes 62, 64, 66, and housing electrode 58.
Electrodes 58, 62, 64, 66 may also be used to deliver cardioversion
pulses to heart 12. Electrodes 62, 64, 66 may be fabricated from
any suitable electrically conductive material, such as, but not
limited to, platinum, platinum alloy or other materials known to be
usable in implantable defibrillation electrodes.
[0067] Pressure sensor 38 may be coupled to one or more coiled
conductors within lead 18. In FIG. 2, pressure sensor 38 is located
more distally on lead 18 than elongated electrode 62. In other
examples, pressure sensor 38 may be positioned more proximally than
elongated electrode 62, rather than distal to electrode 62.
Further, pressure sensor 38 may be coupled to another one of the
leads 20, 22 in other examples, or to a lead other than leads 18,
20, 22 carrying stimulation and sense electrodes. In addition, in
some examples, pressure sensor 38 may be self-contained device that
is implanted within heart 12, such as within the septum separating
right ventricle 28 from left ventricle 32, or the septum separating
right atrium 26 from left atrium 33. In such an example, pressure
sensor 38 may wirelessly communicate with IMD 16.
[0068] The configuration of therapy system 10 illustrated in FIGS.
1 and 2 is merely one example. In other examples, a therapy system
may include epicardial leads and/or patch electrodes instead of or
in addition to the transvenous leads 18, 20, 22 illustrated in FIG.
1. Further, IMD 16 need not be implanted within patient 14. In
examples in which IMD 16 is not implanted in patient 14, IMD 16 may
deliver defibrillation shocks and other therapies to heart 12 via
percutaneous leads that extend through the skin of patient 14 to a
variety of positions within or outside of heart 12.
[0069] In other examples of therapy systems that provide electrical
stimulation therapy to heart 12, a therapy system may include any
suitable number of leads coupled to IMD 16, and each of the leads
may extend to any location within or proximate to heart 12. For
example, other examples of therapy systems may include three
transvenous leads located as illustrated in FIGS. 1 and 2, and an
additional lead located within or proximate to left atrium 33. As
another example, other examples of therapy systems may include a
single lead that extends from IMD 16 into right atrium 26 or right
ventricle 28, or two leads that extend into a respective one of the
right ventricle 28 and right atrium 26. An example of this type of
therapy system is shown in FIG. 3.
[0070] FIG. 3 is a conceptual diagram illustrating another example
of an implantable medical device system (e.g., a therapy system)
70, which is similar to therapy system 10 of FIGS. 1-2, but
includes two leads 18, 22, rather than three leads. Leads 18, 22
are implanted within right ventricle 28 and right atrium 26,
respectively. Therapy system 70 shown in FIG. 3 may be useful for
providing defibrillation and/or pacing pulses to heart 12.
[0071] FIG. 4 is a functional block diagram of one example
configuration of IMD 16, which includes processor 80, memory 82,
stimulation generator 84, sensing module 86, telemetry module 88,
and power source 90. Herein, for IMD 16, the processor 80, memory
82, stimulation generator 84, sensing module 86, and telemetry
module 88 are collectively referred to as "control electronics."
Memory 82 includes computer-readable instructions that, when
executed by processor 80, cause IMD 16 and processor 80 to perform
various functions attributed to IMD 16 and processor 80 herein.
Memory 82 may include any volatile, non-volatile, magnetic,
optical, or electrical media, such as a random access memory (RAM),
read-only memory (ROM), non-volatile RAM (NVRAM),
electrically-erasable programmable ROM (EEPROM), flash memory, or
any other digital media.
[0072] Processor 80 may include any one or more of a
microprocessor, a controller, a digital signal processor (DSP), an
application specific integrated circuit (ASIC), a
field-programmable gate array (FPGA), or equivalent discrete or
integrated logic circuitry. In some examples, processor 80 may
include multiple components, such as any combination of one or more
microprocessors, one or more controllers, one or more DSPs, one or
more ASICs, or one or more FPGAs, as well as other discrete or
integrated logic circuitry. The functions attributed to processor
80 herein may be embodied as software, firmware, hardware or any
combination thereof. Processor 80 controls stimulation generator 84
to deliver stimulation therapy to heart 12 according to a selected
one or more of therapy programs, which may be stored in memory 82.
Specifically, processor 80 may control stimulation generator 84 to
deliver electrical pulses with the amplitudes, pulse widths,
frequency, or electrode polarities specified by the selected one or
more therapy programs.
[0073] Stimulation generator 84 is electrically coupled to
electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, 66, e.g., via
conductors of the respective lead 18, 20, 22, or, in the case of
housing electrode 58, via an electrical conductor disposed within
housing 60 of IMD 16. Stimulation generator 84 is configured to
generate and deliver electrical stimulation therapy to heart 12.
For example, stimulation generator 84 may deliver defibrillation
shocks to heart 12 via at least two electrodes 58, 62, 64, 66.
Stimulation generator 84 may deliver pacing pulses via electrodes
40, 44, 48 (e.g., ring electrodes) coupled to leads 18, 20, 22,
respectively, and/or electrodes 42, 46, 50 (e.g., helical
electrodes) of leads 18, 20, 22, respectively. In some examples,
stimulation generator 84 delivers pacing, cardioversion, or
defibrillation stimulation in the form of electrical pulses. In
other examples, stimulation generator may deliver one or more of
these types of stimulation in the form of other signals, such as
sine waves, square waves, or other substantially continuous time
signals.
[0074] Stimulation generator 84 may include a switch module and
processor 80 may use the switch module to select, e.g., via a
data/address bus, which of the available electrodes are used to
deliver defibrillation shocks and/or pacing pulses. The switch
module may include a switch array, switch matrix, multiplexer, or
any other type of switching device suitable to selectively couple
stimulation energy to selected electrodes.
[0075] Sensing module 86 monitors signals from at least one of
electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, 66 in order to
monitor electrical activity of heart 12, e.g., via
electrocardiogram (ECG) signals. Sensing module 86 may also include
a switch module to select which of the available electrodes are
used to sense the heart activity. In some examples, processor 80
may select the electrodes that function as sense electrodes via the
switch module within sensing module 86, e.g., by providing signals
via a data/address bus. In some examples, sensing module 86
includes one or more sensing channels, each of which may comprises
an amplifier. In response to the signals from processor 80, the
switch module of within sensing module 86 may couple the outputs
from the selected electrodes to one of the sensing channels.
[0076] In some examples, one channel of sensing module 86 may
include an R-wave amplifier that receives signals from electrodes
40 and 42, which are used for pacing and sensing in right ventricle
28 of heart 12. Another channel may include another R-wave
amplifier that receives signals from electrodes 44 and 46, which
are used for pacing and sensing proximate to left ventricle 32 of
heart 12. In some examples, the R-wave amplifiers may take the form
of an automatic gain controlled amplifier that provides an
adjustable sensing threshold as a function of the measured R-wave
amplitude of the heart rhythm.
[0077] In addition, in some examples, one channel of sensing module
86 may include a P-wave amplifier that receives signals from
electrodes 48 and 50, which are used for pacing and sensing in
right atrium 26 of heart 12. In some examples, the P-wave amplifier
may take the form of an automatic gain controlled amplifier that
provides an adjustable sensing threshold as a function of the
measured P-wave amplitude of the heart rhythm. Examples of R-wave
and P-wave amplifiers are described in U.S. Pat. No. 5,117,824
(Keimel et al.). Other amplifiers may also be used. Furthermore, in
some examples, one or more of the sensing channels of sensing
module 86 may be selectively coupled to housing electrode 58, or
elongated electrodes 62, 64, 66, with or instead of one or more of
electrodes 40, 42, 44, 46, 48, 50, e.g., for unipolar sensing of
R-waves or P-waves in any of chambers 26, 28, 32 of heart 12.
[0078] In some examples, sensing module 86 includes a channel that
comprises an amplifier with a relatively wider pass band than the
R-wave or P-wave amplifiers. Signals from the selected sensing
electrodes that are selected for coupling to this wide-band
amplifier may be provided to a multiplexer, and thereafter
converted to multi-bit digital signals by an analog-to-digital
converter for storage in memory 82 as an electrogram (EGM). In some
examples, the storage of such EGMs in memory 82 may be under the
control of a direct memory access circuit. Processor 80 may employ
digital signal analysis techniques to characterize the digitized
signals stored in memory 82 to detect and classify the patient's
heart rhythm from the electrical signals. Processor 80 may detect
and classify the heart rhythm of patient 14 by employing any of the
numerous signal processing methodologies known in the art.
[0079] If IMD 16 is configured to generate and deliver pacing
pulses to heart 12, processor 80 may include pacer timing and
control module, which may be embodied as hardware, firmware,
software, or any combination thereof. The pacer timing and control
module may comprise a dedicated hardware circuit, such as an ASIC,
separate from other processor 80 components, such as a
microprocessor, or a software module executed by a component of
processor 80, which may be a microprocessor or ASIC. The pacer
timing and control module may include programmable counters which
control the basic time intervals associated with DDD, VVI, DVI,
VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR, and other modes
of single and dual chamber pacing. In the aforementioned pacing
modes, "D" may indicate dual chamber, "V" may indicate a ventricle,
"I" may indicate inhibited pacing (e.g., no pacing), and "A" may
indicate an atrium. The first letter in the pacing mode may
indicate the chamber that is paced, the second letter may indicate
the chamber in which an electrical signal is sensed, and the third
letter may indicate the chamber in which the response to sensing is
provided.
[0080] Intervals defined by the pacer timing and control module
within processor 80 may include atrial and ventricular pacing
escape intervals, refractory periods during which sensed P-waves
and R-waves are ineffective to restart timing of the escape
intervals, and the pulse widths of the pacing pulses. As another
example, the pace timing and control module may define a blanking
period, and provide signals from sensing module 86 to blank one or
more channels, e.g., amplifiers, for a period during and after
delivery of electrical stimulation to heart 12. The durations of
these intervals may be determined by processor 80 in response to
stored data in memory 82. The pacer timing and control module of
processor 80 may also determine the amplitude of the cardiac pacing
pulses.
[0081] During pacing, escape interval counters within the pacer
timing/control module of processor 80 may be reset upon sensing of
R-waves and P-waves. Stimulation generator 84 may include pacer
output circuits that are coupled, e.g., selectively by a switching
module, to any combination of electrodes 40, 42, 44, 46, 48, 50,
58, 62, 66 appropriate for delivery of a bipolar or unipolar pacing
pulse to one of the chambers of heart 12. Processor 80 may reset
the escape interval counters upon the generation of pacing pulses
by stimulation generator 84, and thereby control the basic timing
of cardiac pacing functions, including anti-tachyarrhythmia
pacing.
[0082] The value of the count present in the escape interval
counters when reset by sensed R-waves and P-waves may be used by
processor 80 to measure the durations of R-R intervals, P-P
intervals, P-R intervals and R-P intervals, which are measurements
that may be stored in memory 82. Processor 80 may use the count in
the interval counters to detect a tachyarrhythmia event, such as
ventricular fibrillation event or ventricular tachycardia event.
Upon detecting a threshold number of tachyarrhythmia events,
processor 80 may identify the presence of a tachyarrhythmia
episode, such as a ventricular fibrillation episode, a ventricular
tachycardia episode, or a non-sustained tachycardia (NST)
episode.
[0083] In some examples, processor 80 may operate as an interrupt
driven device, and is responsive to interrupts from pacer timing
and control module, where the interrupts may correspond to the
occurrences of sensed P-waves and R-waves and the generation of
cardiac pacing pulses. Any necessary mathematical calculations to
be performed by processor 80 and any updating of the values or
intervals controlled by the pacer timing and control module of
processor 80 may take place following such interrupts. A portion of
memory 82 may be configured as a plurality of recirculating
buffers, capable of holding series of measured intervals, which may
be analyzed by processor 80 in response to the occurrence of a pace
or sense interrupt to determine whether the patient's heart 12 is
presently exhibiting atrial or ventricular tachyarrhythmia.
[0084] In some examples, an arrhythmia detection method may include
any suitable tachyarrhythmia detection algorithms. In one example,
processor 80 may utilize all or a subset of the rule-based
detection methods described in U.S. Pat. No. 5,545,186 (Olson et
al.) or in U.S. Pat. No. 5,755,736 (Gillberg et al.). Other
arrhythmia detection methodologies may also be employed by
processor 80 in other examples.
[0085] In the examples described herein, processor 80 may identify
the presence of an atrial or ventricular tachyarrhythmia episode by
detecting a series of tachyarrhythmia events (e.g., R-R or P-P
intervals having a duration less than or equal to a threshold) of
an average rate indicative of tachyarrhythmia or an unbroken series
of short R-R or P-P intervals. The thresholds for determining the
R-R or P-P interval that indicates a tachyarrhythmia event may be
stored within memory 82 of IMD 16. In addition, the number of
tachyarrhythmia events that are detected to confirm the presence of
a tachyarrhythmia episode may be stored as a number of intervals to
detect (NID) threshold value in memory 82. In some examples,
processor 80 may also identify the presence of the tachyarrhythmia
episode by detecting a variable coupling interval between the
R-waves of the heart signal. For example, if the interval between
successive tachyarrhythmia events varies by a particular percentage
or the differences between the coupling intervals are higher than a
given threshold over a predetermined number of successive cycles,
processor 80 may determine that the tachyarrhythmia is present.
[0086] If processor 80 detects an atrial or ventricular
tachyarrhythmia based on signals from sensing module 86, and an
anti-tachyarrhythmia pacing regimen is desired, timing intervals
for controlling the generation of anti-tachyarrhythmia pacing
therapies by stimulation generator 84 may be loaded by processor 80
into the pacer timing and control module to control the operation
of the escape interval counters therein and to define refractory
periods during which detection of R-waves and P-waves is
ineffective to restart the escape interval counters.
[0087] If IMD 16 is configured to generate and deliver
defibrillation shocks to heart 12, stimulation generator 84 may
include a high voltage charge circuit and a high voltage output
circuit. In the event that generation of a cardioversion or
defibrillation shock is required, processor 80 may employ the
escape interval counter to control timing of such cardioversion and
defibrillation shocks, as well as associated refractory periods. In
response to the detection of atrial or ventricular fibrillation or
tachyarrhythmia requiring a cardioversion pulse, processor 80 may
activate a cardioversion/defibrillation control module, which may,
like pacer timing and control module, be a hardware component of
processor 80 and/or a firmware or software module executed by one
or more hardware components of processor 80. The
cardioversion/defibrillation control module may initiate charging
of the high voltage capacitors of the high voltage charge circuit
of stimulation generator 84 under control of a high voltage
charging control line.
[0088] Processor 80 may monitor the voltage on the high voltage
capacitor, e.g., via a voltage charging and potential (VCAP) line.
In response to the voltage on the high voltage capacitor reaching a
predetermined value set by processor 80, processor 80 may generate
a logic signal that terminates charging. Thereafter, timing of the
delivery of the defibrillation or cardioversion pulse by
stimulation generator 84 is controlled by the
cardioversion/defibrillation control module of processor 80.
Following delivery of the fibrillation or tachycardia therapy,
processor 80 may return stimulation generator 84 to a cardiac
pacing function and await the next successive interrupt due to
pacing or the occurrence of a sensed atrial or ventricular
depolarization.
[0089] Stimulation generator 84 may deliver cardioversion or
defibrillation shocks with the aid of an output circuit that
determines whether a monophasic or biphasic pulse is delivered,
whether housing electrode 58 serves as cathode or anode, and which
electrodes are involved in delivery of the cardioversion or
defibrillation shocks. Such functionality may be provided by one or
more switches or a switching module of stimulation generator
84.
[0090] Telemetry module 88 includes any suitable hardware,
firmware, software or any combination thereof for communicating
with another device, such as programmer 24 (FIG. 1). Under the
control of processor 80, telemetry module 88 may receive downlink
telemetry from and send uplink telemetry to programmer 24 with the
aid of an antenna, which may be internal and/or external. Processor
80 may provide the data to be uplinked to programmer 24 and the
control signals for the telemetry circuit within telemetry module
88, e.g., via an address/data bus. In some examples, telemetry
module 88 may provide received data to processor 80 via a
multiplexer.
[0091] In some examples, processor 80 may transmit atrial and
ventricular heart signals (e.g., electrocardiogram signals)
produced by atrial and ventricular sense amp circuits within
sensing module 86 to programmer 24. Programmer 24 may interrogate
IMD 16 to receive the heart signals. Processor 80 may store heart
signals within memory 82, and retrieve stored heart signals from
memory 82. Processor 80 may also generate and store marker codes
indicative of different cardiac episodes that sensing module 86
detects, and transmit the marker codes to programmer 24. An example
pacemaker with marker-channel capability is described in U.S. Pat.
No. 4,374,382 (Markowitz).
[0092] The various components of IMD 16 are coupled to power source
90, which includes a non-rechargeable (or "primary") battery as
described in greater detail herein below.
[0093] FIG. 5 is block diagram of an example programmer 24. As
shown in FIG. 5, programmer 24 includes processor 100, memory 102,
user interface 104, telemetry module 106, and power source 108.
Programmer 24 may be a dedicated hardware device with dedicated
software for programming of IMD 16. Alternatively, programmer 24
may be an off-the-shelf computing device running an application
that enables programmer 24 to program IMD 16.
[0094] A user may use programmer 24 to select therapy programs
(e.g., sets of stimulation parameters), generate new therapy
programs, modify therapy programs through individual or global
adjustments or transmit the new programs to a medical device, such
as IMD 16 (FIG. 1). The clinician may interact with programmer 24
via user interface 104, which may include display to present
graphical user interface to a user, and a keypad or another
mechanism for receiving input from a user.
[0095] Processor 100 can take the form one or more microprocessors,
DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, and
the functions attributed to processor 100 herein may be embodied as
hardware, firmware, software or any combination thereof. Memory 102
may store instructions that cause processor 100 to provide the
functionality ascribed to programmer 24 herein, and information
used by processor 100 to provide the functionality ascribed to
programmer 24 herein. Memory 102 may include any fixed or removable
magnetic, optical, or electrical media, such as RAM, ROM, CD-ROM,
hard or floppy magnetic disks, EEPROM, or the like. Memory 102 may
also include a removable memory portion that may be used to provide
memory updates or increases in memory capacities. A removable
memory may also allow patient data to be easily transferred to
another computing device, or to be removed before programmer 24 is
used to program therapy for another patient. Memory 102 may also
store information that controls therapy delivery by IMD 16, such as
stimulation parameter values.
[0096] Programmer 24 may communicate wirelessly with IMD 16, such
as using RF communication or proximal inductive interaction. This
wireless communication is possible through the use of telemetry
module 106, which may be coupled to an internal antenna or an
external antenna. An external antenna that is coupled to programmer
24 may correspond to the programming head that may be placed over
heart 12, as described above with reference to FIG. 1. Telemetry
module 106 may be similar to telemetry module 88 of IMD 16 (FIG.
4).
[0097] Telemetry module 106 may also be configured to communicate
with another computing device via wireless communication
techniques, or direct communication through a wired connection.
Examples of local wireless communication techniques that may be
employed to facilitate communication between programmer 24 and
another computing device include RF communication according to the
802.11 or Bluetooth specification sets, infrared communication,
e.g., according to the IrDA standard, or other standard or
proprietary telemetry protocols. In this manner, other external
devices may be capable of communicating with programmer 24 without
needing to establish a secure wireless connection.
[0098] Power source 108 delivers operating power to the components
of programmer 24. Power source 108 may include a battery and a
power generation circuit to produce the operating power. In some
embodiments, the battery may be rechargeable to allow extended
operation. Recharging may be accomplished by electrically coupling
power source 108 to a cradle or plug that is connected to an
alternating current (AC) outlet. In addition or alternatively,
recharging may be accomplished through proximal inductive
interaction between an external charger and an inductive charging
coil within programmer 24. In other embodiments, traditional
primary batteries (e.g., nickel cadmium or lithium ion batteries)
may be used. In addition, programmer 24 may be directly coupled to
an alternating current outlet to power programmer 24. Power source
108 may include circuitry to monitor power remaining within a
battery. In this manner, user interface 104 may provide a current
battery level indicator or low battery level indicator when the
battery needs to be replaced or recharged. In some cases, power
source 108 may be capable of estimating the remaining time of
operation using the current battery.
[0099] Referring again to FIG. 4, processor 80 of IMD 16 may detect
a tachyarrhythmia episode, such as a ventricular fibrillation,
ventricular tachycardia, fast ventricular tachyarrhythmia episode,
or a NST episode, based on electrocardiographic activity of heart
12 that is monitored via sensing module 86. For example, sensing
module 86, with the aid of at least some of the electrodes 40, 42,
44, 46, 48, 50, 58, 62, 64, 66 (shown in FIGS. 1-2), may generate
an electrocardiogram (ECG) or electrogram (EGM) signal that
indicates the electrocardiographic activity. Alternatively, sensing
module 86 may be coupled to sense electrodes that are separate from
the stimulation electrodes that deliver electrical stimulation to
heart 12 (shown in FIGS. 1-3), and may be coupled to one or more
different leads than leads 18, 20, 22 (shown in FIGS. 1-2). The ECG
signal may be indicative of the depolarization of heart 12.
[0100] For example, as previously described, in some examples,
processor 80 may identify the presence of a tachyarrhythmia episode
by detecting a threshold number of tachyarrhythmia events (e.g.,
R-R or P-P intervals having a duration less than or equal to a
threshold). In some examples, processor 80 may also identify the
presence of the tachyarrhythmia episode by detecting a variable
coupling interval between the R-waves of the heart signal.
[0101] FIG. 6 is a block diagram illustrating a system 190 that
includes an external device 192, such as a server, and one or more
computing devices 194A-194N that are coupled to IMD 16 and
programmer 24 shown in FIG. 1 via a network 196, according to one
embodiment. In this embodiment, IMD 16 uses its telemetry module 88
to communicate with programmer 24 via a first wireless connection,
and to communicate with an access point 198 via a second wireless
connection. In the example of FIG. 6, access point 198, programmer
24, external device 192, and computing devices 194A-194N are
interconnected, and able to communicate with each other, through
network 196. In some cases, one or more of access point 198,
programmer 24, external device 192, and computing devices 194A-194N
may be coupled to network 196 through one or more wireless
connections. IMD 16, programmer 24, external device 192, and
computing devices 194A-194N may each comprise one or more
processors, such as one or more microprocessors, DSPs, ASICs,
FPGAs, programmable logic circuitry, or the like, that may perform
various functions and operations, such as those described
herein.
[0102] Access point 198 may comprise a device that connects to
network 196 via any of a variety of connections, such as telephone
dial-up, digital subscriber line (DSL), or cable modem connections.
In other examples, access point 198 may be coupled to network 196
through different forms of connections, including wired or wireless
connections. In some examples, access point 198 may communicate
with programmer 24 and/or IMD 16. Access point 198 may be
co-located with patient 14 (e.g., within the same room or within
the same site as patient 14) or may be remotely located from
patient 14. For example, access point 198 may be a home monitor
that is located in the patient's home or is portable for carrying
with patient 14.
[0103] During operation, IMD 16 may collect, measure, and store
various forms of diagnostic data. In certain cases, IMD 16 may
directly analyze collected diagnostic data and generate any
corresponding reports or alerts. In some cases, however, IMD 16 may
send diagnostic data to programmer 24, access point 198, and/or
external device 192, either wirelessly or via access point 198 and
network 196, for remote processing and analysis.
[0104] In some cases, IMD 16 and/or programmer 24 may combine all
of the diagnostic data into a single displayable lead integrity
report, which may be displayed on programmer 24. The lead integrity
report contains diagnostic information concerning one or more
electrode leads that are coupled to IMD 16, such as leads 18, 20,
or 22. A clinician or other trained professional may review and/or
annotate the lead integrity report, and possibly identify any
lead-related conditions.
[0105] In another example, IMD 16 may provide external device 192
with collected diagnostic data via access point 198 and network
196. External device 192 includes one or more processors 200. In
some cases, external device 192 may request such data, and in some
cases, IMD 16 may automatically or periodically provide such data
to external device 192. Upon receipt of the diagnostic data via
input/output device 202, external device 192 is capable of
analyzing the data and generating reports or alerts upon
determination that there may be a possible condition with one or
more of leads 18, 20, and 22. For example, one or more of leads 18,
20, and 22 may experience a condition related to a lead fracture or
an insulation breach.
[0106] In one embodiment, external device 192 may combine the
diagnostic data into a lead integrity report. One or more of
computing devices 194A-194N may access the report through network
196 and display the report to users of computing devices 194A-194N.
In some cases, external device 192 may automatically send the
report via input/output device 202 to one or more of computing
devices 194A-194N as an alert, such as an audio or visual alert. In
some cases, external device 192 may send the report to another
device, such as programmer 24, either automatically or upon
request. In some cases, external device 192 may display the report
to a user via input/output device 196.
[0107] In one embodiment, external device 192 may comprise a secure
storage site for diagnostic information that has been collected
from IMD 16 and/or programmer 24. In this embodiment, network 196
may comprise an Internet network, and trained professionals, such
as clinicians, may use computing devices 194A-194N to securely
access stored diagnostic data on external device 192. For example,
the trained professionals may need to enter usernames and passwords
to access the stored information on external device 192. In one
embodiment, external device 192 may be a CareLink server provided
by Medtronic, Inc., of Minneapolis, Minn.
[0108] The techniques described in this disclosure, including those
attributed to IMD 16, programmer 24, or various constituent
components, may be implemented, at least in part, in hardware,
software, firmware or any combination thereof. For example, various
aspects of the techniques may be implemented within one or more
processors, including one or more microprocessors, DSPs, ASICs,
FPGAs, or any other equivalent integrated or discrete logic
circuitry, as well as any combinations of such components, embodied
in programmers, such as physician or patient programmers,
stimulators, image processing devices or other devices. The term
"processor" or "processing circuitry" may generally refer to any of
the foregoing logic circuitry, alone or in combination with other
logic circuitry, or any other equivalent circuitry.
[0109] Such hardware, software, firmware may be implemented within
the same device or within separate devices to support the various
operations and functions described in this disclosure. In addition,
any of the described units, modules or components may be
implemented together or separately as discrete but interoperable
logic devices. Depiction of different features as modules or units
is intended to highlight different functional aspects and does not
necessarily imply that such modules or units must be realized by
separate hardware or software components. Rather, functionality
associated with one or more modules or units may be performed by
separate hardware or software components, or integrated within
common or separate hardware or software components.
[0110] When implemented in software, the functionality ascribed to
the systems, devices and techniques described in this disclosure
may be embodied as instructions on a computer-readable medium such
as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage
media, optical data storage media, or the like. The instructions
may be executed by one or more processors to support one or more
aspects of the functionality described in this disclosure.
[0111] FIG. 7A is a conceptual diagram illustrating an exemplary
implantable medical device system (e.g., a therapy system) 110 that
provides electrical stimulation therapy to patient 112. Therapy
system 110 includes IMD 114 and medical lead 116. In the example
shown in FIG. 7A, IMD 114 provides deep brain stimulation (DBS) to
brain 118 of patient 112. Lead 116 is implanted within patient 112
such that one or more electrodes 117 carried by lead 116 are
located proximate to a target tissue site within brain 118. IMD 114
provides electrical stimulation to regions within brain 118 in
order to manage a condition of patient 112, such as to mitigate the
severity or duration of the patient condition. In some examples,
more than one lead 116 may be implanted within brain 118 of patient
112 to provide stimulation to multiple anatomical regions of brain
118. As shown in FIG. 7A, system 110 may also include a programmer
120, which may be a handheld device, portable computer, or
workstation that provides a user interface to a clinician or other
user. The clinician may interact with the user interface to program
stimulation parameters.
[0112] DBS may be used to treat various patient conditions, such
as, but not limited to, seizure disorders (e.g., epilepsy), pain,
migraine headaches, psychiatric disorders (e.g., mood or anxiety
disorders), movement disorders (e.g., essential tremor or
Parkinson's disease), Huntington's disease, and other
neurodegenerative disorders. The anatomic region within patient 112
that serves as the target tissue site for stimulation delivered by
IMD 114 may be selected based on the patient condition. For
example, stimulating an anatomical region, such as the substantia
nigra, in brain 118 may reduce the number and magnitude of tremors
experienced by patient 112. Other target anatomical regions for
treatment of movement disorders may include the subthalamic
nucleus, globus pallidus interna, ventral intermediate, and zona
inserta. Anatomical regions such as these may be targeted by the
clinician during implantation of lead 116. In other words, the
clinician may attempt to position lead 116 within or proximate to
these target regions within brain 118.
[0113] DBS lead 116 may include one or more electrodes 117 placed
along the longitudinal axis of lead 116. In some examples,
electrodes 117 may include at least one ring electrode that resides
along the entire circumference of lead 116. Electrical current from
the ring electrodes propagates in all directions from the active
electrode. The resulting stimulation field reaches anatomical
regions of brain 118 within a certain distance in all directions.
The stimulation field may reach the target anatomical region, but
the stimulation field may also affect non-target anatomical regions
and produce unwanted side effects. In other examples, lead 116 may
include a complex electrode array geometry that includes segmented
or partial ring electrodes in addition to or instead of ring
electrodes. The electrodes in a complex electrode array may be
located at different axial and angular positions around the
circumference of the lead, as well as at different longitudinal
positions (i.e., along the longitudinal axis of lead 116). A
complex electrode array geometry may be useful for customizing the
stimulation field and provide improved therapy while decreasing
side effects. For example, with a complex electrode array,
electrodes may be selected along the longitudinal axis of lead 116
as well as along the circumference of lead 116. Activating
selective electrodes of lead 116 can produce customizable
stimulation fields that may be directed to a particular side of
lead 116 in order to isolate the stimulation field around the
target anatomical region of brain 118. In this manner, specific
electrodes of the complex electrode array geometry may be selected
to produce a stimulation field at desired portions of the
circumference instead of always producing a stimulation field
around the entire circumference of the lead, as with some ring
electrodes.
[0114] Producing irregular stimulation fields with a lead 116 with
a complex electrode geometry may allow therapy system 110 to more
effectively treat certain anatomical regions of brain 118. In some
cases, a therapy system 110 including lead 116 with a complex
electrode array may also help reduce or eliminate side effects from
more spherical stimulation fields produced by a conventional array
of ring electrodes. The center of the stimulation field may be
moved away from lead 116 to avoid unwanted stimulation or
compensate for inaccurately placed leads.
[0115] In the example shown in FIG. 7A, lead 116 is coupled to IMD
114 via connector 122, which defines a plurality of electrical
contacts for electrically coupling electrodes 117 to a stimulation
generator within IMD 114. Lead 116 is indirectly coupled to
connector 122 with the aid of lead extension 124. In some examples,
lead 116 may be directly coupled to connector 122 without the aid
of extension 124.
[0116] In this example, programmer 120 is an external computing
device that is configured to wirelessly communicate with IMD 114.
For example, programmer 120 may be a clinician programmer that the
clinician uses to communicate with IMD 114. Alternatively,
programmer 120 may be a patient programmer that allows patient 112
to view and modify therapy parameters. The clinician programmer may
include more programming features than the patient programmer. In
other words, more complex or sensitive tasks may only be allowed by
the clinician programmer to prevent patient 112 from making
undesired changes to IMD 114.
[0117] Programmer 120 may be a hand-held computing device that
includes a display viewable by the user and a user input mechanism
that can be used to provide input to programmer 120. For example,
programmer 120 may include a small display screen (e.g., a liquid
crystal display or a light emitting diode display) that presents
information to the user. In addition, programmer 120 may include a
keypad, buttons, a peripheral pointing device, touch screen or
another input mechanism that allows the user to navigate though the
user interface of programmer 120 and provide input.
[0118] If programmer 120 includes buttons and a keypad, the buttons
may be dedicated to performing a certain function, i.e., a power
button, or the buttons and the keypad may be soft keys that change
in function depending upon the section of the user interface
currently viewed by the user. Alternatively, the screen (not shown)
of programmer 120 may be a touch screen that allows the user to
provide input directly to the user interface shown on the display.
The user may use a stylus or their finger to provide input to the
display.
[0119] In other examples, rather than being a handheld computing
device or a dedicated computing device, programmer 120 may be a
larger workstation or a separate application within another
multi-function device. For example, the multi-function device may
be a cellular phone or personal digital assistant that can be
configured to an application to simulate programmer 120.
Alternatively, a notebook computer, tablet computer, or other
personal computer may enter an application to become programmer 120
with a wireless adapter connected to the personal computer for
communicating with IMD 114.
[0120] When programmer 120 is configured for use by the clinician,
programmer 120 may be used to transmit initial programming
information to IMD 114. This initial information may include system
110 hardware information such as the type of lead 116, the position
of lead 116 within patient 112, the therapy parameter values of
therapy programs stored within IMD 114 or within programmer 120,
and any other information the clinician desires to program into IMD
114.
[0121] With the aid of programmer 120 or another computing device,
a clinician may select values for therapy parameters for
controlling therapy delivery by therapy system 110. The values for
the therapy parameters may be organized into a group of parameter
values referred to as a "therapy program" or "therapy parameter
set." "Therapy program" and "therapy parameter set" are used
interchangeably herein. In the case of electrical stimulation, the
therapy parameters may include an electrode combination, and an
amplitude, which may be a current or voltage amplitude, and, if IMD
114 delivers electrical pulses, a pulse width, and a pulse rate for
stimulation signals to be delivered to the patient. An electrode
combination may include a selected subset of one or more electrodes
117 located on one or more implantable leads 116 coupled to IMD
114. The electrode combination may also refer to the polarities of
the electrodes in the selected subset. By selecting particular
electrode combinations, a clinician may target particular anatomic
structures within brain 118 of patient 112. In addition, by
selecting values for amplitude, pulse width, and pulse rate, the
physician can attempt to generate an efficacious therapy for
patient 112 that is delivered via the selected electrode subset.
Due to physiological diversity, condition differences, and
inaccuracies in lead placement, the parameters may greatly vary
between patients.
[0122] During a programming session, the clinician may determine
one or more therapy programs that may provide effective therapy to
patient 112. Patient 112 may provide feedback to the clinician as
to the efficacy of the specific program being evaluated. Once the
clinician has identified one or more programs that may be
beneficial to patient 112, patient 112 may continue the evaluation
process and determine which program best alleviates the condition
of patient 112 or otherwise provides efficacious therapy to patient
112. Programmer 120 may assist the clinician in the
creation/identification of therapy programs by providing a
methodical system of identifying potentially beneficial therapy
parameters.
[0123] In some examples, the clinician may select therapy
parameters using the techniques described in U.S. Patent
Application Publication Nos. 2007/0203546 (Stone et al.) and
2007/0203541 (Goetz et al.), which describe programming systems and
methods that support the programming of stimulation parameters with
a therapy system 110 including a lead 116, which may include a
complex electrode array geometry.
[0124] In accordance with techniques described in U.S. Patent
Application Publication No. 2007/0203546, a user interface of
programmer 120 may display a representation of the anatomical
regions of patient 112, such as anatomical regions of brain 118.
The three-dimensional (3D) space of the anatomical regions may be
displayed as multiple two-dimensional (2D) views or a 3D
visualization environment. Lead 116 may also be represented on the
display of the user interface, positioned according to the actual
implantation location by the clinician or directly from an image
taken of the lead within brain 118. The clinician may interact with
the user interface of programmer 120 to manually select and program
certain electrodes of lead 116, select an electrode level of the
lead and adjust the resulting stimulation field with the anatomical
regions as guides, or defining one or more stimulation fields that
only affect anatomical regions of interest. Once the clinician has
defined the one or more stimulation fields, system 110
automatically generates the stimulation parameter values associated
with each of the stimulation fields and transmits the parameter
values to IMD 114. The stimulation parameter values may be stored
as therapy programs within a memory of IMD 114 and/or a memory
within programmer 120.
[0125] In accordance with techniques described in U.S. Patent
Application Publication No. 2007/0203541, programmer 120 may
present a user interface that displays electrodes of lead 116 and
enables a user to select individual electrodes to form an electrode
combination and specify parameters for stimulation delivered via
the electrode combination. In accordance with other techniques
described in U.S. Patent Application Publication No. 2007/0203541,
programmer 120 may present a user interface to a user that enables
the user to manipulate a representation of an electrical
stimulation field (i.e., one type of therapy field) produced by a
selected electrode combination. A processor within programmer 120
may then select the appropriate electrode combination, electrode
polarities, amplitudes, pulse widths, and pulse rates of electrical
stimulation sufficient to support the field manipulation operations
inputted by the user into programmer 120. That is, programmer 120
may automatically generate a therapy program, that best fits a
stimulation field created by a user via a user interface of
programmer 120.
[0126] Programmer 120 may also be configured for use by patient
112. When configured as the patient programmer, programmer 120 may
have limited functionality in order to prevent patient 112 from
altering critical functions or applications that may be harmful to
patient 112. In this manner, programmer 120 may only allow patient
112 to adjust certain therapy parameters or set an available range
of values for a particular therapy parameter. Programmer 120 may
also provide an indication to patient 112 when therapy is being
delivered or when the power source within programmer 120 or IMD 114
need to be replaced or recharged.
[0127] Whether programmer 120 is configured for clinician or
patient use, programmer 120 may communicate with IMD 114 or any
other computing device via wireless communication. Programmer 120,
for example, may communicate via wireless communication with IMD
114 using radio frequency (RF) telemetry techniques known in the
art. Programmer 120 may also communicate with another programmer or
computing device via a wired or wireless connection using any of a
variety of local wireless communication techniques, such as RF
communication according to the 802.11 or Bluetooth specification
sets, infrared communication according to the RDA specification
set, or other standard or proprietary telemetry protocols.
Programmer 120 may also communicate with another programming or
computing device via exchange of removable media, such as magnetic
or optical disks, or memory cards or sticks. Further, programmer
120 may communicate with IMD 114 and other another programmer via
remote telemetry techniques known in the art, communicating via a
local area network (LAN), wide area network (WAN), public switched
telephone network (PSTN), or cellular telephone network, for
example.
[0128] In other applications of therapy system 110, the target
therapy delivery site within patient 112 may be a location
proximate to a spinal cord or sacral nerves (e.g., the S2, S3 or S4
sacral nerves) in patient 112 or any other suitable nerve, organ,
muscle or muscle group in patient 112, which may be selected based
on, for example, a patient condition. For example, therapy system
110 may be used to deliver an electrical stimulation to tissue
proximate to a pudendal nerve, a perineal nerve or other areas of
the nervous system, in which cases, lead 116 would be implanted and
substantially fixed proximate to the respective nerve. As further
examples, an electrical stimulation system may be positioned to
deliver a stimulation to help manage peripheral neuropathy or
post-operative pain mitigation, ilioinguinal nerve stimulation,
intercostal nerve stimulation, gastric stimulation for the
treatment of gastric mobility disorders and obesity, muscle
stimulation, for mitigation of other peripheral and localized pain
(e.g., leg pain or back pain). In addition, although a single lead
116 is shown in FIG. 7A, in some therapy systems, two or more leads
may be electrically coupled to IMD 114.
[0129] FIG. 7B is a conceptual diagram of another example of an
implantable medical device system (e.g., therapy system) 130 that
delivers electrical stimulation to target tissue sites proximate to
spinal cord 132 of patient 112. Therapy system 130 includes IMD
114, which is coupled to leads 134, 136 via connector block 122.
Leads 134, 136 each include an array of electrodes 135, 137,
respectively. IMD 114 may deliver stimulation to patient 112 via a
combination of electrodes 135, 137. Electrodes 135, 137 may each be
any suitable type of electrode, such as a ring electrode, partial
ring electrode or segmented electrode.
[0130] In some examples, the array of electrodes 135, 137 may also
include at least one sense electrode that senses a physiological
parameter of patient 112, such as, but not limited to, a heart
rate, respiration rate, respiratory volume, core temperature,
muscular activity, electromyogram (EMG), an electroencephalogram
(EEG), an electrocardiogram (ECG) or galvanic skin response.
Therapy systems 110, 130 may also include sensor 126 (shown in FIG.
7A, not shown in FIG. 7B) in addition to or instead of sense
electrodes on the leads 116, 134, 136. Sensor 126 may be a sensor
configured to detect an activity level, posture, or another
physiological parameter of patient 112. For example, sensor 126 may
generate a signal that changes as a function of the physiological
parameter of patient 112. Sensor 126 may be implanted or external
to patient 112, and may be wirelessly coupled to IMD 114 or via a
lead, such as leads 116, 134, 136, or another lead. For example,
sensor 126 may be implanted within patient 112 at a different site
than IMD 114 or sensor 126 may be external. In some examples,
sensor 126 may be incorporated into a common housing with IMD 114.
In addition to, or instead of, being coupled to IMD 114, in some
cases, sensor 126 may be wirelessly coupled to programmer 120 or
coupled to programmer 120 by a wired connection.
[0131] In the example shown in FIG. 7B, leads 134, 136 are
positioned to deliver bilateral stimulation to patient 112, i.e.,
stimulation signals are delivered to target tissue sites on
opposite sides of a midline of patient 112. The midline may
generally be defined along spinal cord 132. Just as with therapy
system 110, a clinician may generate one or more therapy programs
for therapy system 130 by selecting values for one or more types of
therapy parameters that provide efficacious therapy to patient 112
with the aid of programmer 120 or another computing device. The
therapy parameters may include, for example, a combination of the
electrodes of leads 134 and/or 136, the voltage or current
amplitude, pulse width, and frequency of stimulation.
[0132] FIG. 8 is a functional block diagram of an exemplary IMD
114. IMD 114 includes a processor 140, memory 142, stimulation
generator 144, switching module 146, telemetry module 148, and
power source 150. Herein, for IMD 114, the processor 140, memory
142, stimulation generator 144, switching module 146, and telemetry
module 148 are collectively referred to as "control electronics."
As shown in FIG. 8, stimulation generator 144 is coupled to leads
134, 136, for example, via switching module 146. Alternatively,
stimulation generator 144 may be coupled to a single lead (e.g., as
shown in FIG. 7A) or more than three leads directly or indirectly
(e.g., via a lead extension, such as a bifurcating lead extension
that may electrically and mechanically couple to two leads) as
needed to provide stimulation therapy to patient 112.
[0133] In the example illustrated in FIG. 8, lead 134 includes
electrodes 135A-135D (collectively referred to as "electrodes 135")
and lead 136 includes electrodes 137A-137D (collectively referred
to as "electrodes 137"). Electrodes 135, 137 may be ring
electrodes. In other examples, electrodes 135, 137 may be arranged
in a complex electrode array that includes multiple non-contiguous
electrodes at different angular positions about the outer
circumference of the respective lead 134, 136, as well as different
levels of electrodes spaced along a longitudinal, axis of the
respective lead 134, 136. The configuration, type, and number of
electrodes 135, 137 illustrated in FIG. 8 are merely exemplary. In
other examples, IMD 114 may be coupled to any suitable number of
leads with any suitable number and configuration of electrodes.
[0134] Memory 142 includes computer-readable instructions that,
when executed by processor 140, cause IMD 114 to perform various
functions. Memory 142 may include any volatile, non-volatile,
magnetic, optical, or electrical media, such as a random access
memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM),
electrically-erasable programmable ROM (EEPROM), flash memory, or
any other digital media. Memory 142 may include programs 152,
program groups 154, and operating instructions 156 in separate
memories within memory 142 or separate areas within memory 142.
Each program 152 defines a particular program of therapy in terms
of respective values for electrical stimulation parameters, such as
electrode combination, electrode polarity, current or voltage
amplitude, pulse width and pulse rate. A program group 154 defines
a group of programs that may be delivered together on an
overlapping or non-overlapping basis. Operating instructions 156
guide general operation of IMD 114 under control of processor 140,
and may include instructions for measuring, for example, the
impedance of electrodes 135, 137 and/or determining the distance
between electrodes 135, 137.
[0135] Stimulation generator 144 produces stimulation signals,
which may be pulses as primarily described herein, or continuous
time signals, such as sine waves, for delivery to patient 112 via
selected combinations of electrodes 135, 137. Processor 140
controls stimulation generator 144 according to programs 152 and
program groups 154 stored in memory 142 to apply particular
stimulation parameter values specified by one or more of programs,
such as amplitude, pulse width, and pulse rate. Processor 140 may
include a microprocessor, a controller, a digital signal processor
(DSP), an application specific integrated circuit (ASIC), a
field-programmable gate array (FPGA), or equivalent discrete or
integrated digital or analog logic circuitry, and the functions
attributed to processor 140 herein may be embodied as software,
firmware, hardware or any combination thereof.
[0136] Processor 140 also controls switching module 146 to apply
the stimulation signals generated by stimulation generator 144 to
selected combinations of electrodes 135, 137. In particular,
switching module 146 couples stimulation signals to selected
conductors within leads 134, 136 which, in turn, deliver the
stimulation signals across selected electrodes 135, 137. Switching
module 146 may be a switch array, switch matrix, multiplexer, or
any other type of switching device suitable to selectively couple
stimulation energy to selected electrodes. Hence, stimulation
generator 144 is coupled to electrodes 135, 137 via switching
module 146 and conductors within leads 134, 136. In some examples,
IMD 114 does not include switching module 146.
[0137] Stimulation generator 144 may be a single- or multi-channel
stimulation generator. In particular, stimulation generator 144 may
be capable of delivering, a single stimulation pulse, multiple
stimulation pulses, or a continuous signal at a given time via a
single electrode combination or multiple stimulation pulses at a
given time via multiple electrode combinations. In some examples,
however, stimulation generator 144 and switching module 146 may be
configured to deliver multiple channels on a time-interleaved
basis. In this case, switching module 146 serves to time division
multiplex the output of stimulation generator 144 across different
electrode combinations at different times to deliver multiple
programs or channels of stimulation energy to patient 112.
[0138] Telemetry module 148 supports wireless communication between
IMD 114 and an external programmer 120 (not shown in FIG. 8) or
another computing device under the control of processor 140.
Processor 140 of IMD 114 may receive, as updates to programs,
values for various stimulation parameters such as amplitude and
electrode combination, from programmer 120 via telemetry interface
(i.e., module) 148. The updates to the therapy programs may be
stored within programs 152 portion of memory 142.
[0139] The various components of IMD 114 are coupled to power
source 150, which includes a non-rechargeable (i.e., primary)
battery as described herein.
[0140] FIG. 9 is a functional block diagram of an example of
programmer 120. As shown in FIG. 9, external programmer 120
includes processor 160, memory 162, user interface 164, telemetry
module 166 (i.e., telemetry interface), and power source 168. A
clinician or another user may interact with programmer 120 to
generate and/or select therapy programs for delivery in IM) 114.
For example, in some examples, programmer 120 may allow a clinician
to define stimulation fields and generate appropriate stimulation
parameter values. Processor 160 may store stimulation parameter
values as one or more therapy programs in memory 162. Processor 160
may send programs to IMD 114 via telemetry module 166 to control
stimulation automatically and/or as directed by the user.
[0141] As previously described, programmer 120 may be a handheld
computing device, a workstation or another dedicated or
multifunction computing device. For example, programmer 120 may be
a general purpose computing device (e.g., a personal computer,
personal digital assistant (PDA), cell phone, and so forth) or may
be a computing device dedicated to, for example, programming IMD
114. Programmer 120 may be one of a clinician programmer or a
patient programmer in some examples, i.e., the programmer may be
configured for use depending on the intended user. A clinician
programmer may include more functionality than the patient
programmer. For example, a clinician programmer may include a more
featured user interface that allows a clinician to download usage
and status information from IMD 114, and allows the clinician to
control aspects of IMD 114 not accessible by a patient programmer
example of programmer 120.
[0142] A user, either a clinician or patient 112, may interact with
processor 160 through user interface 164. User interface 164 may
include a display, such as a liquid crystal display (LCD),
light-emitting diode (LED) display, or other screen, to present
information related to stimulation therapy, and buttons or a pad to
provide input to programmer 120. In examples where user interface
164 requires a 3D environment, the user interface may support 3D
environments such as a holographic display, a stereoscopic display,
an autostereoscopic display, a head-mounted 3D display, or any
other display that is capable of presenting a 3D image to the user.
Buttons may include an on/off switch, plus and minus buttons to
zoom in or out or navigate through options, a select button to pick
or store an input, and pointing device, e.g. a mouse, trackball, or
stylus. Other input devices may be a wheel to scroll through
options or a touch pad to move a pointing device on the display. In
some examples, the display may be a touch screen that enables the
user to select options directly from the display screen.
[0143] Processor 160 processes instructions from memory 162 and may
store user input received through user interface 164 into memory
162 when appropriate for the current therapy. In addition,
processor 160 provides and supports any of the functionality
described herein with respect to each example of user interface
164. Processor 160 may comprise any one or more of a
microprocessor, DSP, ASIC, FPGA, or other digital logic circuitry,
and the functions attributed to processor 160 herein may be
embodied as software, firmware, hardware or any combination
thereof.
[0144] Memory 162 may include instructions for operating user
interface 164, telemetry module 166 and managing power source 168.
Memory 162 may store program instructions that, when executed by
processor 160, cause processor 160 and programmer 120 to provide
the functionality ascribed to them herein. Memory 162 also includes
instructions for generating therapy programs, such as instructions
for determining stimulation parameters for achieving a
user-selected stimulation fields or instructions for determining a
resulting stimulation field from user-selected stimulation
parameters. Memory 162 may include any one or more of a RAM, ROM,
EEPROM, flash memory, or the like.
[0145] Wireless telemetry in programmer 120 may be accomplished by
radio frequency (RF) communication or proximal inductive
interaction of programmer 120 with IMD 114. This wireless
communication is possible through the use of telemetry module 166.
Accordingly, telemetry module 166 may include circuitry known in
the art for such communication.
[0146] Power source 168 delivers operating power to the components
of programmer 120. Power source 168 may include a battery and a
power generation circuit to produce the operating power. In some
examples, the battery may be rechargeable to allow extended
operation. Recharging may be accomplished through proximal
inductive interaction, or electrical contact with circuitry of a
base or recharging station. In other examples, primary (i.e.,
non-rechargeable) batteries may be used. In addition, programmer
120 may be directly coupled to an alternating current source, such
would be the case with some computing devices, such as personal
computers.
[0147] The techniques described in this disclosure, including those
attributed to IMD 114, programmer 120, or various constituent
components, may be implemented, at least in part, in hardware,
software, firmware or any combination thereof. For example, various
aspects of the techniques may be implemented within one or more
processors, including one or more microprocessors, DSPs, ASICs,
FPGAs, or any other equivalent integrated or discrete logic
circuitry, as well as any combinations of such components, embodied
in programmers, such as physician or patient programmers,
stimulators, image processing devices or other devices. The term
"processor" or "processing circuitry" may generally refer to any of
the foregoing logic circuitry, alone or in combination with other
logic circuitry, or any other equivalent circuitry.
[0148] Such hardware, software, firmware may be implemented within
the same device or within separate devices to support the various
operations and functions described in this disclosure. In addition,
any of the described units, modules or components may be
implemented together or separately as discrete but interoperable
logic devices. Depiction of different features as modules or units
is intended to highlight different functional aspects and does not
necessarily imply that such modules or units must be realized by
separate hardware or software components. Rather, functionality
associated with one or more modules or units may be performed by
separate hardware or software components, or integrated within
common or separate hardware or software components.
[0149] When implemented in software, the functionality ascribed to
the systems, devices and techniques described in this disclosure
may be embodied as instructions on a computer-readable medium such
as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage
media, optical data storage media, or the like. The instructions
may be executed by one or more processors to support one or more
aspects of the functionality described in this disclosure.
Exemplary Implantable Medical Device Batteries
[0150] Although certain materials described herein are
rechargeable, implantable medical device batteries of the present
disclosure are preferably primary (i.e., non-rechargeable)
batteries. A typical battery includes a case, a liner, and an
electrode assembly. The liner surrounds the electrode assembly to
prevent the electrode assembly from contacting the inside of the
case. The electrode assembly includes one or more electrochemical
cells, wherein each electrochemical cell includes an anode and a
cathode with one or more separators therebetween, and an
electrolyte to facilitate ionic transport and form a conductive
pathway between the anode and cathode. Although the following
description focuses on ICDs, one of skill in the art would
appreciate that these concepts can also apply to other IMDs.
[0151] In a more detailed description, FIG. 10 depicts an IMD 210
that includes a case or housing 250, a control module 252, a
battery 254, and one or more capacitor(s) 256. Control module 252
controls one or more sensing and/or stimulation processes from IMD
210 via leads (not shown). Battery 254 includes an insulator 258
disposed therearound. Battery 254 charges capacitor(s) 256 and
powers control module 252. For example, in an implantable
cardioverter defibrillator, the control module includes control
electronics for delivering therapy and/or monitoring physiological
signals, and includes a processor, memory, a stimulation generator
that generates at least one of cardiac pacing pulses,
defibrillation shocks, and cardioversion shocks, and a sensing
module for monitoring a patient's heart rhythm. The capacitors are
typically high voltage capacitors (e.g., typically greater than 600
volts for ICDs, although this can vary and is generally known to
one of skill in the art what is suitable for various IMD
applications). The ICD also includes an implantable medical device
battery operably connected to the control electronics to deliver
power to the control electronics and operably connected to the
capacitors to charge the capacitors.
[0152] FIGS. 11 and 12 depict details of an exemplary battery 254.
Battery 254, which as shown includes one cell, includes a case 270,
an anode 272, separators 274, a cathode 276, a liquid electrolyte
278, and a feed-through terminal 280. Cathode 276 is wound in a
plurality of turns, with anode 272 interposed between the turns of
the cathode winding. Separator 274 insulates anode 272 from cathode
276 windings. Case 270 contains the liquid electrolyte 278 to
create a conductive path between anode 272 and cathode 276.
Electrolyte 278 serves as a medium for migration of ions between
anode 272 and cathode 276 during discharge of the cell.
[0153] Exemplary ways to construct battery 254 are described, for
example, in U.S. Pat. Nos. 5,439,760 (Howard et al.) and 6,017,656
(Crespi et al.), and U.S. Patent Application Publication No.
2006/0166078A1 (Chen et al.).
[0154] Typical commercial IMD batteries cannot meet the power and
capacity requirements of either conventional IMDs or those in
development in less than about 6.5 cubic centimeters (cc). Thus,
there is a need for batteries with smaller volumes while
maintaining relatively high power capability and capacity, which
are provided herein in certain embodiments.
[0155] In the design of an IMD battery, the desired longevity of
the device and average current drains are used to determine the
required battery capacity. The energy density of the electrode
materials can then be used to determine the volume of battery anode
and cathode required. The desired capacitor charge time, charge
energy, and charge circuit efficiency are used to determine the
required battery power. The rate capability (power per unit area)
of the electrode materials can then be used to determine the
surface area required for the anode and cathode. The required
surface area will then determine how much inert material (such as
current collector and separator) is needed, and therefore the total
cell volume. So, generally, a smaller battery (and, hence, a
smaller IMD) can be produced by reducing IMD current drain,
improving charging circuit efficiency, using an electrode set with
greater energy density, and using an electrode set with greater
rate capability.
[0156] It has proven difficult, however, to balance battery power,
capacity, and volume in an IMD battery having a practical
longevity. For example, an IMD battery volume can be reduced by
reducing the anode and cathode thicknesses, as described herein;
however, while this alone may produce powers of a level suitable
for use, the capacity may be too low. Alternatively, an IMD battery
volume can be reduced by reducing the active area of the electrodes
as well as the amount of inert material within the cell; however,
while this alone may produce capacities of a level suitable for
use, the powers may be too low. Certain aspects of the present
disclosure have overcome the significant challenges associated with
designing a battery having relatively small volume with both
relatively high power and relatively high capacity for a relatively
long useful life. Thus, certain embodiments of the present
disclosure are directed to a battery of relatively small volume but
of relatively high power (reported as therapeutic power) and
relatively high capacity (reported as capacity density).
[0157] Significantly, in certain embodiments, IMD batteries of the
present disclosure have a longevity (i.e., "useful life") of
conventional IMD batteries, which is on the order of years.
Preferably, IMD batteries of the present disclosure have a
longevity of at least 5 years. More preferably, the useful life is
at least 7 years. Even more preferably, the useful life is at least
9 years. Typically, the useful life is no greater than 15
years.
[0158] In certain embodiments, IMD batteries of the present
disclosure have a total volume of no greater than 6.0 cubic
centimeters ("cc" or cm.sup.3). In some embodiments, the total
volume is no greater than 5.5 cc, no greater than 5.0 cc, no
greater than 4.5 cc, or no greater than 4.0 cc. Preferably, the
battery total volume is at least 3.0 cc. The term "total volume" is
the total overall volume of the battery, not the volume of any
individual cell (unless the battery includes only one cell). An IMD
battery of the present disclosure may include one or more
individual cells, each of which includes one cathode (e.g., "one"
cathode can include an assembly of individual cathode plates
electrically connected as in a stacked plate construction), one
anode (e.g., "one" anode can include an assembly of individual
anode plates electrically connected as in a stacked plate
construction), one or more separator(s), and an electrolyte. Thus,
the summation of the volumes of the individual electrochemical
cells is the total volume of the battery. Typically, IMD batteries
of the present disclosure include one cell, although this is not
required for all embodiments of the disclosure.
[0159] Herein, IMD batteries are preferably described in terms of
"therapeutic capacity density" and "therapeutic power." These are
not to be mistaken with conventional terms like "capacity" or
"capacity density" or "power" but are more useful in understanding
the benefits of the present disclosure. This is because
conventional terms may include differing fractions of capacity that
are not usable for the application, making design and comparison of
batteries difficult.
[0160] Briefly, "therapeutic capacity density" refers to the
battery's therapeutic capacity delivered over the useful life of
the battery divided by the battery volume, wherein "therapeutic
capacity" refers to the total capacity delivered until the cell
power (average voltage times the average current) decreases to a
specified wattage (the wattage when the average voltage is 1.6 V.
How these values are determined is shown in the Examples
Section.
[0161] Briefly, the term "therapeutic power" refers to the amount
of cell power (as defined above) a battery delivers for every joule
of therapeutic energy delivered, calculated as the amount of energy
delivered by a stimulation generator to a patient in a single
stimulation event (e.g., one pacing shock, one defibrillation
shock, or one cardioversion shock). How these values are determined
is shown in the Examples Section.
[0162] Significantly, preferred small IMD batteries of the present
disclosure possess a therapeutic power of at least 0.11 Watt (W)
for every joule of therapeutic energy delivered over the useful
life of the battery. In some embodiments, the therapeutic power is
at least 0.14 W, at least 0.17 W, or at least 0.20 W, for every
joule of therapeutic energy delivered over the useful life of the
battery. Typically, for such embodiments, the therapeutic power is
no greater than 0.5 W for every joule of therapeutic energy
delivered over the useful life of the battery.
[0163] Significantly, preferred small IMD batteries of the present
disclosure possess a therapeutic capacity density of at least 0.08
ampere hours per cubic centimeter (Ah/cc). In some embodiments, the
therapeutic capacity density is at least 0.10 Ah/cc, at least 0.13
Ah/cc, at least 0.15 Ah/cc, at least 0.18 Ah/cc, or at least 0.20
Ah/cc. Typically, for such embodiments, the therapeutic capacity
density is no greater than 0.5 Ah/cc.
[0164] For certain embodiments, the anode to cathode capacity ratio
is preferably within a range of 0.6:1 to 1.5:1. For certain
embodiments, anodes of IMD batteries of the present disclosure have
a total uniform thickness determined by the anode to cathode
capacity ratio and the cathode capacity. For example, typical
thicknesses are less than 0.015 inch, and at least 0.002 inch.
[0165] Significantly, for certain embodiments, cathodes of IMD
batteries of the present disclosure have a total uniform thickness
that is thinner than that of cathodes of conventional IMD batteries
of similar power and capacity.
[0166] The term "total uniform thickness" in the context of an
electrode refers to the total overall thickness of the electrode,
not the thickness of any individual layer (e.g., an extruded or
coated layer of cathode material or a layer of metal foil used as a
current collector). This thickness is uniform along its length
(excluding any uncoated areas such as tabs or edges on individual
electrode plates and the portions of the electrode forming the
outermost wraps or plates), with tolerances of no more than
.+-.0.003 inch (3 mil), and preferably no more than .+-.0.001 inch
(1 mil).
[0167] For certain embodiments, the cathodes of IMD batteries of
the present disclosure have a total uniform thickness of less than
0.014 inch. In certain embodiments, the total uniform thickness of
a cathode is no greater than 0.013 inch, no greater than 0.012
inch, no greater than 0.011 inch, no greater than 0.010 inch, no
greater than 0.009 inch, no greater than 0.008 inch, or no greater
than 0.007 inch. The total uniform thickness of a cathode of an IMD
battery of the present disclosure is typically at least 0.004
inch.
[0168] Typical thicknesses of commercial IMD battery cathodes
having the power and capacity requirements of the batteries of the
present disclosure are 0.014 inch and greater. Although certain
reported cathodes are prepared from layers of very thin material,
thereby resulting in a total thickness that may be thinner than
0.014 inch, such batteries would not have the small volume, high
therapeutic power, and high capacity density of the batteries of
the present disclosure; hence no commercially available IMD
batteries include cathodes as thin as those of the present
disclosure.
[0169] Cathodes and anodes of IMD batteries of the present
disclosure have surface areas sufficient to provide the desired
power. Preferably, the surface areas are independently at least 60
square centimeters (cm.sup.2). In some embodiments, the surface
areas of the cathode and anode are independently at least 70
cm.sup.2, at least 80 cm.sup.2, or at least 90 cm.sup.2. Typically,
the surface areas of the cathode and anode are independently no
greater than 110 cm.sup.2. The surface area of a cathode may be the
same or different than that of the anode.
[0170] Cathodes and anodes of IMD batteries of the present
disclosure may have a variety of shapes. Typically, they are in the
limn of plates or coils. For example, an electrode (cathode or
anode) is typically a thin coating, sheet, or foil of the active
material disposed on one or both major surfaces of a thin film of a
current collector (e.g., nickel, copper, aluminum, titanium, gold,
platinum, tantalum, stainless steel, or another conductive metal
that is corrosion-resistant when associated with the active
material). An anode, cathode, and separator can be combined in a
variety of structures, including, for example, spiral wound form,
stacked plate form, or serpentine form, as disclosed, for example,
in U.S. Pat. No. 5,439,760 (Howard et al.) and U.S. Patent
Application Publication No. 2006/0166078 (Chen et al.).
[0171] Preferably, each electrode includes one current collector
(i.e., one single layer of a current collector). That is, for
certain preferred embodiments, for a coiled electrode, each of the
cathode and anode includes one current collector. For a stacked
plate electrode assembly, however, in any one electrode plate,
there is one current collector or one single layer of a current
collector, which are electrically connected to each other to form a
"single" current collector for the combined set of electrode
plates.
[0172] If a stacked plate electrode is used, an individual
electrode is formed of individual electrode plates that are
electrically connected on each side. Thus, the "surface area"
referred to above in the context of an electrode refers to the
total area of the electrode (e.g., the area of the active cathode
material, which excludes any areas such as tabs or edges on
individual cathode plates that do not include active cathode
material), which is the summation of the surface areas of each
individual electrode plate, excluding any area that is not opposing
the other electrode. Thus, the surface area of a stacked plate
electrode does not include the outermost surface of the two
electrode plates at each end of the stack.
[0173] Typically, anodes of IMD batteries, such as anode 272, are
fowled of an active material that includes lithium, which can be in
metallic or ionic form (typically, metallic form). It may also
include other materials, particularly those selected from Group IA,
IIA, or IIIB of the periodic table of elements (e.g., sodium,
potassium, etc.). The anode can include mixtures, alloys (e.g.,
Li--Al alloy), or intermetallic compounds (e.g., Li--Si, Li--B,
Li--Si--B etc.) of the elements of Groups IA, IIA, or IIIB of the
periodic table with each other or with other elements of the
periodic table.
[0174] Cathodes of IMD batteries of the present disclosure, such as
cathode 276, are formed of an active material that includes one or
more metal oxides. Such metal oxides may include one or more
different metals (e.g., the active material can include mixed metal
oxides). The cathode material can also include two or more
different materials, which can be in admixture or in layers, or
both.
[0175] Exemplary metal oxides for use in the cathode active
material include MnO.sub.2, V.sub.6O.sub.13, silver vanadium oxide
(e.g., AgV.sub.2O.sub.5, Ag.sub.2V.sub.4O.sub.11,
Ag.sub.0.35V.sub.2O.sub.5.8, Ag.sub.0.74V.sub.2O.sub.5.37,
AgV.sub.4O.sub.5.5), copper silver vanadium oxide (e.g.,
Cu.sub.0.16Ag.sub.0.67V.sub.2O.sub.5.5 or
Cu.sub.0.5Ag.sub.0.5V.sub.2O.sub.5.75), V.sub.2O.sub.5, copper
oxide, copper vanadium oxide, or combinations thereof. Combinations
of such materials can be used if desired. Preferred metal oxides
are the various materials that include silver and vanadium oxide,
referred to generally as "silver vanadium oxide" or "SVO." SVO is
capable of being synthesized using a variety of methods. Methods of
synthesis generally fall within two categories, depending on the
type of chemical reaction that produces the SVO. SVO can be
synthesized using a decomposition reaction, resulting in
decomposition-produced SVO (DSVO). Alternatively, SVO can be
synthesized using a combination reaction, resulting in
combination-produced SVO (CSVO). Regardless of how it is made, SVO
can be formed in a variety of different structural phases (e.g.,
.beta., .gamma., and .di-elect cons.) and have a variety of
different crystalline forms. A particularly preferred metal oxide
is Ag.sub.2V.sub.4O.sub.11, which is prepared by the addition
reaction described in U.S. Pat. No. 5,221,453 (Crespi).
[0176] Preferably, cathode material of IMD batteries of the present
disclosure also includes a second active material that is of a
higher energy density and a lower rate capability than the metal
oxide active material (i.e., the first active material) described
above. Typically and preferably, this second active material is
carbon monofluoride, although other materials such as Ag.sub.2O,
Ag.sub.2O.sub.2, CuF, Ag.sub.2CrO.sub.4, MnO.sub.2, and even SVO
can be used. Combinations of such materials can be used if desired.
Carbon monofluoride, often referred to as carbon fluoride,
polycarbon monofluoride, CF.sub.x or graphite fluoride is a solid,
structural, non-stoichiometric fluorocarbon of empirical formula
CF.sub.x, wherein x is 0.01 to 1.9, preferably 0.1 to 1.5, and more
preferably 1.1. One commercial faun of carbon monofluoride is
(CF.sub.x).sub.n where 0<x<1.25 (and n is the number of
monomer units in the polymer, which can vary widely).
[0177] Generally, production of CF.sub.x involves an exemplary
chemical reaction such as:
F.sub.2+(x+y+z)C.fwdarw.xCF.sub.1.1+yC+z(CF.sub.n.gtoreq.2)
where x, y, and z are numerical values that may be positive
integers or positive rational numbers. In this reaction, fluorine
and carbon react to form CF.sub.1.1. Unreacted carbon and
impurities are by-products of the chemical reaction, which are
preferably minimized during production of CF.sub.x. It is desirable
to achieve a weight percentage of fluorine greater than or equal to
61% in CF.sub.x while reducing impurities. Preferably, greater than
or equal to 63% or 65% of fluorine exists in the CF.sub.x. Purity,
crystallinity, and particle shape, particularly of the carbon
precursor, are also properties to consider in the selection of
carbon monofluoride. This is described in greater detail in U.S.
Patent Application Publication No. 2007/0178381 (Howard et al.).
Therein, fibrous CF.sub.x materials are described, which are
particularly advantageous.
[0178] A particularly preferred cathode material is silver vanadium
oxide used in combination with carbon monofluoride, preferably as a
mixture. The CF.sub.x:SVO capacity ratio is preferably within a
range of 10:1 to 1:1. The CF.sub.x:SVO stoichiometric ratio is
preferably within a range of 2:1 to 4:1 (electrochemical
equivalents). There are various forms of silver vanadium oxide and
carbon monofluoride, such as those described in U.S. Pat. Nos.
5,180,642 (Weiss et al.) and 6,783,888 (Gan et al.), and U.S.
Patent Application Publication No. 2007/0178381 (Howard et
al.).
[0179] The particle sizes and shapes are also characteristics of
the cathode materials to be considered. This is particularly true
in obtaining the thin, yet effective, coatings of the cathode
material on the current collector. For example, desirably,
particles of the cathode material are less than 20% of the
electrode thickness. The particle size is typically no greater than
100 microns, although even smaller particles (e.g., no greater than
20 microns) can be more desirable in certain situations.
[0180] Although uniformly or regularly shaped (e.g., spherical)
particles are desired for ease of coating, mechanical integrity of
the cathode, enhanced compressibility (providing increased cell
capacity), rod-shaped (i.e., fibrous or filamentous) particles may
contribute to higher power. For certain embodiments of the present
invention, the cathode material includes fibrous particles, and for
certain embodiments, the cathode material includes a mixture of
fibrous particles with irregularly shaped agglomerates of
needle-shaped particles.
[0181] The cathode material typically also includes a conductivity
enhancer and a binder. The conductivity enhancer is typically a
conductive carbon, such as carbon black, acetylene black, and/or
graphite, although other metallic powders can be used such as
aluminum, titanium, nickel, and stainless steel. Various
combinations of such conductivity enhancers can be used if desired.
The amount of conductive enhancer is typically at least 1 wt-%, and
typically no more than 10 wt-%, based on the total weight of the
dry cathode mix (without solvent).
[0182] The binder can be carboxy methyl cellulose (CMC),
styrene-butadiene rubber (SBR), polyvinylidene difluoride (PVDF),
polytetrafluoroethylene (PTFE), or combinations thereof. Preferred
binders are SBR and PVDF. A more preferred binder is SBR. The
amount of binder is typically at least 1 wt-%, and typically no
more than 5 wt-%, based on the total weight of the dry cathode mix
(without solvent).
[0183] Such binders can be used in a battery of relatively small
volume but of relatively high power (reported as therapeutic power)
and relatively high capacity (reported as capacity density), but
this is not a requirement. Using these polymers, particularly the
SBR, the active ingredients can be increased to greater than 92
wt-%, making the cathode/battery more energy dense. The cathode
mixture can be slurry coated, as discussed in greater detail below,
allowing for much thinner layers, which is more cost effective, and
provides higher yields. Thus, for certain embodiments of the
present disclosure, a non-rechargeable battery is provided that
includes: an anode; a cathode comprising a binder comprising
styrene-butadiene rubber; a separator between the anode and the
cathode; and an electrolyte contacting the anode, the cathode, and
the separator.
[0184] The current collectors used in the electrodes of IMD
batteries of the present disclosure are of the type used
conventionally. Generally, they are metal films or foils, such as
aluminum, titanium, nickel, copper, or another conductive metal
that is corrosion-resistant when associated with the active anode
material. They may be primed or unprimed. They may be perforated or
not. The thicknesses of the current collectors are typically at
least 0.0001 inch, and more often at least 0.003 inch. The
thicknesses of the current collectors are typically no greater than
0.01 inch (e.g., a titanium current collector is typically 0.005
inch thick to handle the current load without becoming excessively
hot), and often no greater than 0.001 inch (e.g., an aluminum
current collector can be as thin as 20 microns (0.0008 inch)). The
separators used in electrochemical cells of IMD batteries of the
present disclosure are selected to electrically insulate the anode
from the cathode. Conventional materials can be used. The material
is generally wettable by the cell electrolyte, sufficiently porous
to allow the electrolyte to flow through separator material, and
maintains physical and chemical integrity within the cell during
operation. Examples of suitable separator materials include, but
are not limited to, fluoropolymeric fabrics,
polytetrafluoroethylene (PTFE), ceramics, non-woven glass, glass
fiber material, polypropylene, and polyethylene. For example, the
separator can include microporous polyethylene (PE) or
polypropylene (PP) and/or a layer of non-woven polypropylene or
polyethylene laminated to it. As described in U.S. Patent
Application Publication No. 2006/0166078 (Chen et al.), a separator
can consist of three layers, for example, having a polyethylene
layer sandwiched between two layers of polypropylene. The
polyethylene layer has a lower melting point than the polypropylene
layers and provides a shut down mechanism in case of cell over
heating.
[0185] The electrolyte includes a liquid organic electrolyte, which
typically includes an organic solvent in combination with an
ionizing solute. The organic solvent can be, for example,
diethylcarbonate, dimethylcarbonate, dipropylcarbonate,
diisopropylcarbonate, di-tert-butylcarbonate, dibutylcarbonate,
diphenylcarbonate, dicyclopentylcarbonate, ethylenecarbonate,
butylenecarbonate, 3-methyl-2-oxazolidone, sulfolane,
tetrahydrofuran (THF), methyl-substituted tetrahydrofuran,
1,3-dioxolane, propylene carbonate (PC), ethylene carbonate,
gamma-butyrolactone, ethylene glycol sulfite, dimethylsulfite,
dimethyl sulfoxide, 1,2-dimethoxyethane, dimethyl isoxazole,
dioxane, ethyl methyl carbonate, methyl formate, diglyme, glyme,
acetonitrile, N-methyl-2-pyrrolidone (NMP), solvents of the type
disclosed in U.S. Pat. No. 6,017,656 (Crespi et al.), or the like,
or mixtures thereof. The ionizing solute can be a simple or soluble
salt or mixtures thereof, for example, an alkali metal salt (e.g.,
LiBF.sub.4, LiAsF.sub.6, LiPF.sub.6, LiClO.sub.4,
LiN(SO.sub.2CF.sub.3).sub.2, LiC(SO.sub.2CF.sub.3).sub.3,
LiSbF.sub.6, LiO.sub.2, LiAlCl.sub.4, LiGaCl.sub.4, LiSCN,
LiO.sub.3SCF.sub.3, LiC.sub.6F.sub.5SO.sub.3, LiO.sub.2CCF.sub.3,
LiSO.sub.6F, LiB(C.sub.6H.sub.5).sub.4, LiCF.sub.3SO.sub.3, and
mixtures thereof), which will produce an ionically conductive
solution when dissolved in one or more solvents. For example, the
electrolyte can include a lithium salt (e.g., 1.0M LiClO.sub.4 or
LiPF.sub.6 or LiAsF.sub.6) in a 50/50 mixture of propylene
carbonate and 1,2-dimethoxyethane. A preferred electrolyte is 1.0M
LiAsF.sub.6 in a mixture of 50 vol-% propylene carbonate (PC) and
50 vol % 1,2-dimethoxyethane (DME).
Preferred Process of Making Cathodes for Batteries
[0186] Conventional methods of making IMD batteries, particularly
cathodes for IMD batteries, are limited in their ability to make
cathodes having the total uniform thicknesses described herein
without sacrificing function, such as power and capacity, of the
battery. For example, for designs above 6 cc and up to 9 cc of
high-rate batteries, the cathode powder is typically pressed into a
Ti grid, that is then wound together with lithium foil
electrically-isolated by a porous membrane. To supply the required
power, the double-sided area of the cathode approaches 90 cm.sup.2.
This powder dispensing cathode technology generally limits the
available capacity of 90 cm.sup.2 batteries to be 850 mAh or
greater.
[0187] Although such powder dispensing cathode technology can be
used in certain situations to prepare cathodes for IMD batteries of
the present disclosure (e.g., some of the larger volume batteries),
in certain embodiments, the present disclosure provides a more
generally effective method of forming a cathode that overcomes many
of the problems of the powder dispensing technology. The preferred
method described herein provides primary high-rate batteries of 6
cc and smaller with high power and high capacity capabilities.
Although this method is described for coating the cathodes for use
in an IMD battery, it could also apply to coating cathodes for use
in other batteries. Also, this method can be used in making
cathodes for batteries of other sizes, powers, capacities, etc.
than those described herein.
[0188] This method involves coating a slurry that includes the
components of the cathode material, such as an active cathode
material (e.g., SVO/CF.sub.x mixture), binder (e.g., PVDF, CMC,
SBR, or combinations thereof), and conductivity enhancer (carbon
black, acetylene black, and/or graphite), which can optionally be
combined and mixed with a dispersant and/or thickener in a solvent.
The materials are typically combined in a high-shear mixer (e.g., a
centrifugal mixer) and/or high-speed mixer, with or without mixing
media (e.g., 21-mm.times.21-mm, cylindrically shaped, ceramic
media).
[0189] The components of the cathode material are typically
combined with a solvent and dispersant and/or thickener in amounts
to provide the desired viscosity suitable for the desired coating
method. The solvent can be any of a wide variety of organic
solvents (e.g., N-methylpyrrolidone (NMP), methyl ethyl ketone),
water, or a combination thereof. The thickener/dispersant can be
any of a wide variety of materials, such as CMC, guar gum, xanthum
gum, polyethylene glycol, and combinations thereof. If PVDF is used
as the binder, NMP is typically used as the solvent. If SBR is used
as the binder, water is typically used as the solvent. Also, from a
practical processing point, CMC is used with the SBR to better
disperse the SBR.
[0190] The amounts of the solvent, dispersant, and/or thickener
relative to the other components can vary depending on the desired
viscosity. The amount of solvent can vary widely, but is typically
at least 30 wt-%, and typically no more than 60 wt-%, based on the
total weight of the slurry. The amount of dispersant and/or
thickener can vary widely, but is typically no more than 4 wt-%,
based on the total weight of the slurry.
[0191] The mixing conditions (e.g., time, temperature, velocity of
mixing) are sufficient to form a homogeneous mixture without any
non-wetted clumps of dry material. These conditions can vary and
depend on the concentrations of the cathode materials, but can be
readily determined by one of skill in the art.
[0192] Preferably, during mixing, the temperature of the slurry is
controlled so it does not exceed levels where oxidation of
components could occur. Also, it is controlled to limit evaporation
of the solvent. Furthermore, the temperature of the resulting
slurry affects the viscosity. Thus, it is desirable to control the
temperature during both mixing and coating.
[0193] The desired viscosity of the slurry depends on the type of
coating method used (e.g., knife over blade coating, knife over
roll coating, doctor blade coating, slot die coating, ink-jet
coating (e.g., as described in International Patent Application
Publication No. WO 2009/035488) (Nielsen et al.), etc.), the
thickness of the coating desired, the concentrations of the
components remaining in the coated cathode material, etc. The
static viscosity of a suitable slurry is typically at least 70,000
centipoise (cP), and typically no more than 150,000 cP, for
appropriate leveling and to avoid sagging or running.
[0194] The coating slurry, however, is a non-Newtonian fluid. Thus,
the viscosity of the slurry will change as a function of flow rate
(e.g., the viscosity drops under shear). Desirably, the dynamic
viscosity is such that the value of "n" in the equation of
(Visc.sub.0).times.(Shear Rate).sup.n-1 is 0.3 to 0.6. When this
occurs, the viscosity drops enough under shear to effectively pump
the slurry, and the cross-web control of the coated material is
maintained (e.g., such that deposition (mg/cm.sup.2) is
substantially constant cross-web, and there are good "clean" edges
formed upon coating the material).
[0195] This slurry coating method results in coating chemistries of
controlled thicknesses. To provide smaller batteries with the
volume of interest, the amount of cathode material deposited using
this slurry coating method is preferably within a range of 16
mg/cm.sup.2 to 35 mg/cm.sup.2, depending on the desired power and
capacity
[0196] Upon slurry coating, the mixture is dried to remove
substantially all the solvent. Typically, drying of the slurry
coated cathode material occurs by heating it up to a temperature of
60.degree. C. to 100.degree. C. for water, or 60.degree. C. to
120.degree. C. for NMP, optionally under vacuum or a nitrogen
atmosphere, or it can be allowed to air dry at room
temperature.
[0197] After being dried, the coated material can be compressed to
obtain the desired porosity, packing density, and thickness of the
cathode material. The amount of compression can be determined by
one of skill in the art. Typically, pressures of 20,000 psi to
45,000 psi can be used.
EXEMPLARY EMBODIMENTS OF THE DISCLOSURE
[0198] The following outlines exemplary embodiments of the present
disclosure, which are also described in Attorney Docket Nos.
134.03980101 (P0031258.01) and 134.04150101 (P0035803.00), each of
which is filed on even date herewith.
1. An implantable cardioverter defibrillator device comprising:
[0199] control electronics for delivering therapy and/or monitoring
physiological signals, the control electronics comprising: [0200] a
processor; [0201] memory; [0202] a stimulation generator that
generates at least one of cardiac pacing pulses, defibrillation
shocks, and cardioversion shocks; and [0203] a sensing module for
monitoring a patient's heart rhythm;
[0204] one or more defibrillator capacitors; and
[0205] an implantable medical device battery operably connected to
the control electronics to deliver power to the control
electronics, and operably connected to the capacitors to charge the
capacitors; wherein the battery has a total volume of no greater
than 6.0 cc, the battery comprising: [0206] an anode comprising
lithium; [0207] a cathode having a total uniform thickness of less
than 0.014 inch; [0208] a separator between the anode and the
cathode; and [0209] an electrolyte contacting the anode, the
cathode, and the separator; [0210] wherein the cathode material
comprises a metal oxide;
[0211] wherein the battery has a therapeutic power of at least 0.11
W for every joule of therapeutic energy delivered over the useful
life of the battery, and a therapeutic capacity density of at least
0.08 Ah/cc.
2. An implantable medical device comprising:
[0212] control electronics for delivering therapy and/or monitoring
physiological signals, the control electronics comprising: [0213] a
processor; and [0214] memory; and
[0215] an implantable medical device battery operably connected to
the control electronics to deliver power to the control
electronics; wherein the battery has a total volume of no greater
than 6.0 cc, the battery comprising: [0216] an anode comprising
lithium; [0217] a cathode having a total uniform thickness of less
than 0.014 inch; [0218] a separator between the anode and the
cathode; and [0219] an electrolyte contacting the anode, the
cathode, and the separator; [0220] wherein the cathode material
comprises a metal oxide;
[0221] wherein the battery has a therapeutic power of at least 0.11
W for every joule of therapeutic energy delivered over the useful
life of the battery, and a therapeutic capacity density of at least
0.08 Ah/cc.
3. The implantable device of embodiment 1 or embodiment 2, wherein
the battery volume is no greater than 5.0 cc. 4. The implantable
device of any one of the preceding embodiments, wherein the battery
volume is at least 3.0 cc. 5. The implantable device of any one of
the preceding embodiments, wherein the therapeutic power of the
battery is at least 0.14 W for every joule of therapeutic energy
delivered over the useful life of the battery. 6. The implantable
device of any one of the preceding embodiments, wherein the
therapeutic capacity density of the battery is at least 0.10 Ah/cc.
7. The implantable device of any one of the preceding embodiments,
wherein the surface area of each of the cathode and anode is at
least 60 cm.sup.2. 8. The implantable device of any one of the
preceding embodiments, wherein the cathode comprises a silver
vanadium oxide. 9. The implantable device of any one of the
preceding embodiments, wherein the cathode comprises a mixture of
two or more materials. 10. The implantable device of embodiment 9,
wherein the cathode material further comprises carbon monofluoride.
11. The implantable device of any one of the preceding embodiments,
wherein the cathode comprises a single current collector. 12. An
implantable medical device comprising:
[0222] control electronics for delivering therapy and/or monitoring
physiological signals, the control electronics comprising: [0223] a
processor; and [0224] memory; and
[0225] an implantable medical device battery operably connected to
the control electronics to deliver power to the control
electronics; wherein the battery has a total volume of no greater
than 6.0 cc, the battery comprising: [0226] an anode comprising
lithium; [0227] a cathode comprising a single current collector and
having a total uniform thickness of less than 0.014 inch; [0228] a
separator between the anode and the cathode; and [0229] an
electrolyte contacting the anode, the cathode, and the separator;
[0230] wherein the cathode material comprises a layer on each major
surface of the single current collector, wherein the layer
comprises a mixture comprising a metal oxide and carbon
monofluoride;
[0231] wherein the battery has a therapeutic power of at least 0.11
W for every joule of therapeutic energy delivered over the useful
life of the battery, and a therapeutic capacity density of at least
0.08 Ah/cc.
13. An implantable medical device system comprising: [0232] an
implantable medical device of any one of embodiments 1 through 12;
and [0233] components operably attached to the implantable medical
device for delivering therapy and/or monitoring physiological
signals. 14. An implantable medical device battery comprising:
[0234] an anode comprising lithium;
[0235] a cathode having a total uniform thickness of less than
0.014 inch; wherein the cathode material comprises a metal
oxide;
[0236] a separator between the anode and the cathode; and
[0237] an electrolyte contacting the anode, the cathode, and the
separator;
[0238] wherein the battery has a therapeutic power of at least 0.11
W for every joule of therapeutic energy delivered over the useful
life of the battery, and a therapeutic capacity density of at least
0.08 Ah/cc.
15. The battery of embodiment 14, wherein the battery volume is no
greater than 5.0 cc. 16. The battery of embodiment 14 or embodiment
15, wherein the battery volume is at least 3.0 cc. 17. The battery
of any one of embodiments 14 through 16, wherein the therapeutic
power of the battery is at least 0.14 W for every joule of
therapeutic energy delivered over the useful life of the battery.
18. The battery of any one of embodiments 14 through 17, wherein
the therapeutic capacity density of the battery is at least 0.10
Ah/cc. 19. The battery of any one of embodiments 14 through 17,
wherein the surface area of each of the cathode and anode is at
least 60 cm.sup.2. 20. The battery of any one of embodiments 14
through 19, wherein the cathode comprises a silver vanadium oxide.
21. The battery of any one of embodiments 14 through 20, wherein
the cathode comprises a mixture of two or more materials. 22. The
battery of embodiment 21, wherein the cathode material further
comprises carbon monofluoride. 23. The battery of any one
embodiments 14 through 22, wherein the cathode is prepared from a
slurry coated onto a current collector. 24. The battery of any one
of embodiments 14 through 23, wherein the cathode material
comprises a binder comprising styrene-butadiene-rubber. 25. A
method of making a battery, the method comprising:
[0239] preparing a cathode material slurry comprising an active
cathode material, a binder, and a solvent;
[0240] applying the cathode material slurry to at least one major
surface of a current collector;
[0241] removing the solvent from the coated cathode slurry material
to form a dry cathode coating;
[0242] compressing the dry cathode coating to reduce porosity and
thickness of the coating;
and
[0243] combining the cathode with an anode, one or more separators,
and an electrolyte to form a battery.
26. The method of embodiment 25, wherein the battery is an
implantable medical device battery. 27. The method of embodiment 25
or embodiment 26, wherein the cathode material slurry comprises
fibrous particles. 28. The method of embodiment 27, wherein the
cathode material comprises a mixture of fibrous particles with
irregularly shaped agglomerates of needle-shaped particles 29. The
method of any one of embodiments 25 through 28, wherein the cathode
material slurry comprises a thickener and/or dispersant. 30. The
method of embodiment 29, wherein the thickener and/or dispersant
comprises carboxy methyl cellulose, guar gum, xanthum gum,
polyethylene glycol, and combinations thereof. 31. The method of
any one of embodiments 25 through 30, wherein the binder comprises
styrene-butadiene rubber. 32. The method of embodiment 31, wherein
the solvent comprises water. 33. The method of embodiment 31,
wherein the cathode material slurry comprises carboxy methyl
cellulose. 34. The method of any one of embodiments 25 through 30,
wherein the binder comprises polyvinylidene difluoride. 35. The
method of embodiment 34, wherein the solvent comprises
N-methyl-2-pyrrolidone. 36. A non-rechargeable battery
comprising:
[0244] an anode;
[0245] a cathode comprising a binder comprising styrene-butadiene
rubber;
[0246] a separator between the anode and the cathode; and
[0247] an electrolyte contacting the anode, the cathode, and the
separator.
37. The battery of embodiment 36, wherein the cathode comprises a
silver vanadium oxide. 38. The battery of embodiment 36 or 37,
wherein the cathode comprises a mixture of two or more materials.
39. The battery of embodiment 38, wherein the cathode material
further comprises carbon monofluoride. 40. The battery of any one
of embodiments 36 through 39, wherein the cathode comprises carboxy
methyl cellulose. 41. An implantable medical device comprising a
battery of any one of embodiments 36 through 40. 42. The
implantable medical device of embodiment 41 which is an implantable
cardioverter defibrillator device.
EXAMPLES
[0248] Objects and advantages of this disclosure are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this disclosure.
[0249] The following materials were used in the Examples:
TABLE-US-00001 Material Source and/or Specifications SVO Silver
vanadium oxide in the form of Ag.sub.2V.sub.4O.sub.11, manufactured
according to the procedure of U.S. Pat. No. 5,221,453 (Crespi) and
jet milled to a particle size of 20 microns or less (although this
is not required, rather it is done for processing purposes in slot
die coating). CFx Fibrous carbon monofluoride (62-67 wt-% total
fluorine, less than 0.10 wt-% free fluorine, X-ray diffraction peak
ratio I (2 theta, 25.86)/I (2 theta, 28.64) of less than 1), ground
to less than 100 micron particle size (although this is not
required, rather it is done for processing purposes in slot die
coating). Carbon Chevron Phillips Shawinigan Black .RTM. Acetylene
Black, 70% black Compressed, available from Chevron Philips, The
Woodlands, TX. Binder 40 wt-% in water of an SBR (a modified
styrene-butadiene copolymer) emulsion (BM-400B, trade name of
product manufactured by Zeon Corp., Tokyo, Japan). Dispersant
Daicel 2200 CMC (0.7 wt-% solution of Carboxy Methyl solution
Cellulose in water) available at Daicel Chemical Industries, Ltd.,
Japan. DI water Deionized water
Example 1a
Preparation of Slurry with SpeedMixer and Ceramic Media
[0250] A centrifugal mixer such as a SpeedMixer DAC 150 FV,
available from FlackTek, Inc. (Landrum, S.C.) was used with mixing
cups and cup holders of various sizes. Also, two 21-mm.times.21-mm,
cylindrically shaped, ceramic media were used. The SpeedMixer can
make batches of slurry in amounts up to 60 grams.
[0251] To make 20 grams of slurry, 5.41 grams of SVO, 3.79 grams of
CFx, and 0.60 gram of carbon black were weighed and placed into a
powder cup. The powder cup was placed in the cup holder, and then
the cup holder was placed into the SpeedMixer. The materials were
mixed by the SpeedMixer for 30 seconds at about 2500 revolutions
per minute (RPM). The powder cup then was removed from the cup
holder.
[0252] The CMC dispersant was measured and added to the powder cup
(9.87 grams of Daicel 2200 CMC (0.7% solution)). Two
21-mm.times.21-mm ceramic cylindrical shaped media were placed into
the cup with the mixture. The powder cup was then placed into the
cup holder and then the cup holder was placed into the
SpeedMixer.
[0253] The materials were mixed by the SpeedMixer for 1 minute at
about 3000 RPM. The slurry cup was removed from the mixer.
Non-wetted clumps of material were broken up with a laboratory
stirring tool (e.g., Spoonula Lab Spoon). The materials were mixed
for three to five 60-second intervals with non-wetted clumps being
broken up between the 60-second intervals.
[0254] BM-400B binder (Zeon) was weighed (0.335 gram) and added
into the cup. The contents of the cup were mixed by the SpeedMixer
for 30 seconds at 1500 RPM.
[0255] The mixture was observed while stirring with a stirring tool
to verify complete mixing. The mixing was repeated for three to
five 30-second intervals followed by stirring with a stirring tool,
until the slurry looked smooth. Complete wetting was visually
verified.
Example 1b
Preparation of Slurry with SpeedMixer without Ceramic Media
[0256] To make 20 grams of slurry, 5.41 grams of SVO, 3.79 grams of
CFx, and 0.60 gram of carbon black were weighed and placed into a
powder cup. The powder cup was placed in the cup holder, and then
the cup holder was placed into the SpeedMixer. The materials were
mixed by the SpeedMixer for 30 seconds at about 2000 RPM. The
powder cup then was removed from the cup holder.
[0257] Fifty percent of the CMC dispersant was added to the powder
cup (50% of 9.87 grams of Daicel 2200 CMC (0.7% solution)). The
powder cup was then placed into the cup holder and then the cup
holder was placed into the SpeedMixer.
[0258] The materials were mixed by the SpeedMixer for 1 minute at
3300 RPM. The slurry cup was removed from the mixer. Non-wetted
clumps were broken up with a laboratory stirring tool (e.g.,
Spoonula Lab Spoon). The materials were mixed for three to five
60-second intervals with non-wetted clumps being broken up between
the 60-second intervals.
[0259] The mixture was observed for state of mix and to allow time
for cooling if the mixture temperature was near 60.degree. C.
Another 10% of the CMC solution was added to the mixture, when the
mixture did not wet-out completely. While mixing in 60-second
intervals, the mixture evolved from a dry mix, to a paste, to a
high-viscosity slurry. Mixing in 60-second intervals was continued
until all of the particles were wetted.
[0260] The remaining amount of CMC dispersant was added to the
mixture. The materials were mixed by the SpeedMixer for 60 seconds
at 2500 RPM. The mixture was observed and mixing in 60-second
intervals was continued until materials were a smooth mixture by
visual inspection while not exceeding 60.degree. C.
[0261] Zeon BM-400B binder (0.335 gram) was weighed and added into
the cup. The contents of the cup were mixed by the SpeedMixer for
30 seconds at 1500 RPM. The mixture was observed while stirring
with a stirring tool to verify complete mixing. The mixing was
repeated for three to five more 30-second intervals followed by
stirring, until the slurry looked smooth. Complete wetting was
visually verified.
Example 1c
Preparation of Slurry with SpeedMixer without Ceramic Media
[0262] To make 20 grams of slurry, 5.32 grams of SVO, 3.73 grams of
CFx, and 0.60 gram of carbon black were weighed and placed into a
powder cup. The powder cup was placed in the cup holder, and then
the cup holder was placed into the SpeedMixer. The materials were
mixed by the SpeedMixer for 30 seconds at about 2000 RPM. The
powder cup then was removed from the cup holder.
[0263] Fifty percent of the CMC dispersant was added to the powder
cup (50% of 10 grams of Daicel 2200 CMC (1% solution)). The powder
cup was then placed into the cup holder and then the cup holder was
placed into the SpeedMixer.
[0264] The materials were mixed by the SpeedMixer for 1 minute at
3300 RPM. The slurry cup was removed from the mixer. Non-wetted
clumps were broken up with a laboratory stirring tool (e.g.,
Spoonula Lab Spoon). The materials were mixed for three to five
60-second intervals with non-wetted clumps being broken up between
the 60-second intervals.
[0265] The mixture was observed for state of mix and to allow time
for cooling if the mixture temperature was near 60.degree. C.
Another 10% of the CMC solution was added to the mixture, when the
mixture did not wet-out completely. While mixing in 60-second
intervals, the mixture evolved from a dry mix, to a paste, to a
high-viscosity slurry. Mixing in 60-second intervals was continued
until all of the particles were wetted.
[0266] The remaining amount of CMC dispersant was added to the
mixture. The materials were mixed by the SpeedMixer for 60 seconds
at 2500 RPM. The mixture was observed and mixing in 60-second
intervals was continued until materials were a smooth mixture by
visual inspection while not exceeding 60.degree. C.
[0267] Zeon BM-400B binder (0.335 gram) was weighed and added into
the cup. The contents of the cup were mixed by the SpeedMixer for
30 seconds at 1500 RPM. The mixture was observed while stirring
with a stirring tool to verify complete mixing. The mixing was
repeated for three to five more 30-second intervals followed by
stirring, until the slurry looked smooth. Complete wetting was
visually verified.
Example 2
Coating the Current Collectors
[0268] In this Example, a knife-over-plate slurry coater, such as a
P1-1210 Filmcoater available from Sangyo Company, LTD, was employed
along with an adjustable doctor blade.
[0269] The current collector was a 20-micrometer aluminum foil. A
foil strip of the current collector was placed on a vacuum plate.
The vacuum source was activated to hold the foil in place, a
parting sheet was taped to an aluminum plate, and the current
collector (substrate) was taped to the parting sheet. A visual
inspection verified that the foil was flat on the plate, the
perimeter edges of foil were taped onto the plate.
[0270] Then, the height of the coating blade of the P1-1210
Filmcoater was adjusted to the desired thickness of the coating.
For an electrode to have a 0.010 inch end thickness, the blade
height was set at 0.018 inch. Then, a quantity of the slurry
prepared as in Example 1a or 1b was placed on the end of the grid
closest to the blade start.
[0271] Prior to each coating run the slurry was remixed for 20
seconds at 1500 RPM. The coating head was run to coat at a speed of
about 1 inch per second.
[0272] The tape was removed from the perimeter of the foil. Then
the wet coated electrode on the aluminum plate was placed into a
pre-heated oven at 60.degree. C. and was dried for 30 minutes.
[0273] The current collector, having a coating on one major
surface, was then coated on the opposite major surface. The height
of the doctor blade was set to deposit the same coating thickness
on the second side of the current collector as was deposited on the
first side. A quantity of slurry from Example 1a or 1b was
deposited and coated on the second side of the current collectors
using the coating procedure described above.
Example 3
Cathode Preparation and Measurement
Cell Preparation and Assembly
[0274] With a steel rule die, cathode plates with uncoated tabs
were punched out of the coated current collectors prepared
according to Example 2. Then, the punched-out cathode plates were
compressed for about 10 seconds at 34,000 psi (pounds per square
inch) press pressure. The cathode plates were then vacuum dried at
80.degree. C. and about 300 mbar for over 12 hours.
Example 4
Preparation of Cell Assembly
[0275] A battery was assembled and included fifteen cathode plates
prepared according to Example 3, fourteen two-sided anode plates,
and two single-sided anode plates. The anode plates contained
lithium metal on a 0.001 inch thick (1 mil) perforated copper foil
collector.
[0276] The individual cathode plates were sealed in Celgard 2320
polymer battery separator (20 micrometer microporous trilayer
membrane (PP/PE/PP), available from Celgard, LLC, Charlotte, N.C.).
The individual anode plates were sealed in Celgard 2500 polymer
battery separator (25 micrometer microporous membrane (PP),
available from Celgard, LLC, Charlotte, N.C.). The anode plates and
cathode plates were electrically connected such that the batteries
were made to be case negative.
[0277] All cathode plates were incorporated into a single cell in a
case having a cover with one feedthrough hole and one hole for a
fill port. A feedthrough was welded on the inside of the case with
the ferrule inside the case. A plastic pin protector was used. A
thermal cup and stacking fixture was used to stack the anode plates
and cathode plates. The insulator cup with stacked electrodes was
removed from the stacking fixture and the case liner was placed
over the electrode assembly. The stack was placed into the case,
aligning the feedthrough pin with the hole in the case liner. Two
feedthrough insulator discs were placed over the feedthrough
pin.
[0278] A thin strip of titanium sheet material ("jumper") was used
for interconnecting the cathode stack to the feedthrough pin, and
the hole in the jumper was located over the feedthrough pin. The
other end of the jumper was positioned on the tab. A foil shield
was placed over the case wall next to the jumper and stack. The
jumper was welded to the stack. The feedthrough pin was trimmed
flush to the jumper surface. Then, the pin was welded to the
jumper. A headspace cover insulator was placed over the cathode
interconnect. The anode stack was resistance spot welded to the
case. The cover was inserted into the case while ensuring that the
headspace cover insulator had not rotated past the edge of the
cover. The cover was welded and dielectric withstand test was
performed at 1000 volts.
[0279] The cell was filled with high rate electrolyte with the
following formulation: 1.0M LiAsF.sub.6 in a mixture of 50 vol-%
propylene carbonate (PC) and 50 vol % 1,2-dimethoxyethane
(DME).
[0280] The fill port holes were welded closed. A safety holder was
used as the fixture. A sleeve insulator was placed over the pin on
the outside of the battery.
[0281] The data in Table 2 were calculated regarding the
battery.
TABLE-US-00002 TABLE 2 Cathode utilization 0.8 Number of cathodes
15 Cathode capacity density (Ah/cc) 1.49 Area (total 2 sides of
each plate) (cm.sup.2) 6.06 Anode capacity density (Ah/cc) 2.06
Total separator thickness (mil) 62 Cathode/Anode vol ratio (Beta)
2.94 Total effective collector thickness (mil) 28 Porosity of
cathode 0.41 Thickness of an electrode pair (active) 13.7 Allowable
space in thickness direction (mil) 296 Thickness ignoring lithium
excess (mil) 10.7 Lithium thickness at PLF (mil) - on each side 1.5
Lithium thickness used (mil) 2.7 Ave thickness of cathode grid
(mil) 0.8 Total lithium thickness (mil) (sum of both sides) 5.7 Ave
thickness of anode grid (mil) 1 Cathode thickness (mil) Active (sum
of both sides) 8.0 Separator thickness (mil) 1 Total Cathode
Thickness (mil) 8.8 Area for a 15 cathode battery of 6.06 cm2 per
cathode (cm2) 90.9 Capacity for a 15 cathode battery of 6.06 cm2
per cathode (Ah) 0.62 for thickness calculation case 0.016 in
cathode density as built 2.01 g/cc 2.5% SBR on 1085 cover 0.016 in
cathode capacity 0.44 Ah/g theor. Based on slurry formula cup
insulator 0.014 in cathode capacity density 0.88 Ah/cc Calculated
liner 0.004 in Porosity 41% Calculated sub-total 0.050 in
theoretically dense Ah/cc 1.49 Ah/cc Calculated total thickness
0.346 in at cathode utilization Total at cathode utilization total
0.31 anode volume (cc) 0.66 0.92 cathode volume (cc) 0.92 0.65
anode capacity (Ah) 1.36 0.65 cathode capacity (Ah) 0.81
Example 5
Cell Modeling
[0282] In this example, modeling of cells was performed using an
electrical model and a mechanical model.
[0283] Mechanical modeling used design dimensions of various cell
components to calculate total cell volume and electrode surface
area. The mechanical modeling also used known material properties
of cell components, such as density of electrode materials,
theoretical capacity of electrode materials, porosity of the
finished cathode, and the area normalized resistance of the
finished cathode.
[0284] Electrical modeling included an Ohm's Law model using cell
background voltage and resistance (calculated in the mechanical
model) to calculate available power.
[0285] In this manner, for example, capacity delivered in terms of
ampere hours per cubic centimeter was calculated given a power at
1.6 volts and a material. Also, for example, cell capacity density
in terms of ampere hours per cubic centimeter was calculated given
a cell volume and at a given therapy power at 1.6 volts.
[0286] Calculation of the Therapeutic Capacity Density of a cell is
performed as follows:
[0287] The Cell Power,
CP=(V.sub.avg)*(i.sub.avg) Eq. 1
[0288] where V.sub.avg and i.sub.avg are the average cell voltage
and current under load, respectively, during a high power discharge
for therapeutic purposes.
[0289] The Cell Resistance,
R=(A.sub.elect)*(R.sub.norm) Eq. 2
[0290] where A.sub.elect is the electrode area and R.sub.norm is
the area normalized resistance of the cell. It should be noted that
R.sub.norm will be a function of depth of discharge of the cell,
and may also be a function of the time over which that discharge
occurs.
[0291] At a given depth of discharge of the cell, the current
supplied during a high power discharge is,
i.sub.avg(x)=[(V.sub.back(x)-V.sub.avg(x))/R(x)] Eq. 3
[0292] where V.sub.back(x), V.sub.avg(X), and R(x) are the
background voltage, average loaded voltage, and cell resistance,
respectively, at depth of discharge, x.
[0293] V.sub.back(X) and R(x) are determined experimentally, as
described in Crespi et al., "Modeling and Characterization of the
Resistance of Lithium/SVO Batteries for Implantable Cardioverter
Defibrillators," Journal of the Electrochemical Society, 148,
A30-A37 (2001).
[0294] The Specified Wattage occurs when V.sub.avg=1.6V. The Cell
Power at the Specified Wattage is therefore
CP=1.6V*[(V.sub.back(x)-1.6V)/R(x)] Eq. 4
[0295] The average current that is observed for the Specified
Wattage is
i.sub.avg(x)=CP/1.6V Eq. 5
or
i.sub.avg(x)=[(V.sub.back(x)-1.6V)/R(x)] Eq. 6
[0296] The Therapeutic Capacity,
TC=(Q.sub.total)*(x)-(Q.sub.init) Eq. 7
[0297] where Q.sub.total is the total cathode capacity, x is the %
utilization of the cathode to the point at which the Specified
Wattage is met, and Q.sub.init is the amount of cathode capacity
removed prior to implant of the device.
[0298] The cathode utilization, x, of the cell at the end of the
therapeutic life of the cell is determined by: [0299] 1. Choosing
the Specific Wattage that defines the end of therapeutic life.
[0300] 2. Setting the Cell Power to the Specific Wattage, and
iteratively solving Eqs. 5 and 6 for x.
[0301] The Therapeutic Capacity is then calculated from Eq. 7, and
the Therapeutic Capacity Density is calculated by dividing the
Therapeutic Capacity by the cell volume.
[0302] For example, for the 4.5 cc Type 2 cell in FIG. 16 [0.2
W/J], the total cell Capacity, Q.sub.total, is 1.08 Ah and the
initial capacity, Q.sub.init, is 0.033 Ah. The battery area is 90.9
cm.sup.2. For a 35 J therapy, the Specified Wattage is 7 W. For the
Type 2 chemistry, 7 W will be produced with an average load voltage
of 1.6V when the cathode utilization, x, is 72%. At that point, the
background voltage of the cell, V.sub.back, will be 2.579V, and its
resistance, R, will be 0.224 ohms. The Therapeutic Capacity will
therefore be 0.75 Ah, and Therapeutic Capacity Density is 0.17
Ah/cm.sup.3.
[0303] Therapeutic Power as depicted in FIGS. 13-16 is chosen to
reflect the desire to deliver a given amount of defibrillation
therapy to the patient in an acceptable amount of time. That time
is approximately 15 seconds. Beyond 15 seconds, the efficacy of the
therapy is thought to decrease.
[0304] Most ICDs are designed to deliver up to 35 J of
defibrillation therapy to the patient. Because there are circuit
inefficiencies and delivery losses associated with the ICD system,
approximately 60 J of energy are removed from the battery to
deliver 35 J of defibrillation therapy to the patient. (This varies
up to approximately 25%, depending on the device and system.)
Therefore, the desired minimum power of the cell is approximately
0.11 W/J of therapeutic energy (=[60 J/35 J]/15 s). Greater power
is desirable, as short therapy times are highly valued by
physicians.
[0305] The data shown in FIGS. 13-16 reflect both actual and
theoretical (indicated by open data points) therapeutic cell
density (Ah/cc) for various cell volumes (cc). The data shown in
each of FIGS. 13-16 are based on a given therapeutic power at 1.6
volts, ranging from 0.11 W/J (FIG. 13) to 0.2 W/J (FIG. 16). Each
series of data labeled 1-5 in the legend indicates one of the five
different materials for coating cathodes. The materials used are as
follows: series Type "1" represents LiAgVO.sub.2 (anode limited, as
described in U.S. Pat. No. 5,458,977 (Crespi et al.)); series Type
"2" represents (CF.sub.x/SVO (2:1 ratio as described in U.S. Patent
Publication No. 2007/0178381 (Howard et al.)); series Type "3"
represents CF.sub.x/V.sub.6O.sub.13 (2:1 ratio as described in U.S.
Pat. No. 5,180,642 (Weiss et al.)); series Type "4" represents
MnO.sub.2; and series Type "5" represents SVO (as described in U.S.
Pat. No. 5,221,453 (Crespi)). Actual test data is indicated with
filled data points in FIGS. 13-16, whereas calculated theoretical
values are indicated with open data points.
[0306] The complete disclosures of the patents, patent documents,
and publications cited herein are incorporated by reference in
their entirety as if each were individually incorporated. Various
modifications and alterations to this disclosure will become
apparent to those skilled in the art without departing from the
scope and spirit of this disclosure. It should be understood that
this disclosure is not intended to be unduly limited by the
illustrative embodiments and examples set forth herein and that
such examples and embodiments are presented by way of example only
with the scope of the disclosure intended to be limited only by the
claims set forth herein as follows.
* * * * *