U.S. patent application number 14/519436 was filed with the patent office on 2015-10-29 for implantable extravascular electrical stimulation lead having improved sensing and pacing capability.
The applicant listed for this patent is Medtronic, Inc.. Invention is credited to Jian Cao, Melissa G.T. Christie, Paul J. DeGroot, Mark T. Marshall, Vladimir P. Nikolski, Amy E. Thompson-Nauman.
Application Number | 20150306375 14/519436 |
Document ID | / |
Family ID | 54333834 |
Filed Date | 2015-10-29 |
United States Patent
Application |
20150306375 |
Kind Code |
A1 |
Marshall; Mark T. ; et
al. |
October 29, 2015 |
IMPLANTABLE EXTRAVASCULAR ELECTRICAL STIMULATION LEAD HAVING
IMPROVED SENSING AND PACING CAPABILITY
Abstract
Implantable medical electrical leads having electrodes arranged
such that a defibrillation coil electrode and a pace/sense
electrode(s) are concurrently positioned substantially over the
ventricle when implanted are described. The leads include an
elongated lead body having a distal portion and a proximal end, a
connector at the proximal end of the lead body, a defibrillation
electrode located along the distal portion of the lead body,
wherein the defibrillation electrode includes a first segment and a
second segment proximal to the first segment by a distance, a first
electrical conductor extending from the proximal end of the lead
body and electrically coupling to the first segment and the second
segment of the defibrillation electrode, and at least one
pace/sense electrode located between the first segment and the
second segment of the defibrillation electrode.
Inventors: |
Marshall; Mark T.; (Forest
Lake, MN) ; Cao; Jian; (Shoreview, MN) ;
Christie; Melissa G.T.; (Andover, MN) ; DeGroot; Paul
J.; (Shoreview, MN) ; Nikolski; Vladimir P.;
(Blaine, MN) ; Thompson-Nauman; Amy E.; (Ham Lake,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medtronic, Inc. |
Minneapolis |
MN |
US |
|
|
Family ID: |
54333834 |
Appl. No.: |
14/519436 |
Filed: |
October 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61984148 |
Apr 25, 2014 |
|
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|
Current U.S.
Class: |
607/4 ;
607/116 |
Current CPC
Class: |
A61N 1/3918 20130101;
A61N 1/0504 20130101; A61N 1/05 20130101 |
International
Class: |
A61N 1/05 20060101
A61N001/05; A61N 1/39 20060101 A61N001/39 |
Claims
1. An implantable medical electrical lead comprising: an elongated
lead body having a distal portion and a proximal end; a connector
at the proximal end of the lead body; a defibrillation electrode
located along the distal portion of the lead body, wherein the
defibrillation electrode includes a first segment and a second
segment proximal to the first segment by a distance; a first
electrical conductor extending from the proximal end of the lead
body and electrically coupling to the first segment and the second
segment of the defibrillation electrode; and at least one
pace/sense electrode located between the first segment and the
second segment of the defibrillation electrode.
2. The lead of claim 1, wherein the at least one pace/sense
electrode comprises a first pace/sense electrode and a second
pace/sense electrode located between the first segment and the
second segment, the implantable medical electrical lead further
comprising: a second electrical conductor extending from the
connector at the proximal end of the lead body and electrically
coupling to the first pace/sense electrode; and a third electrical
conductor extending from the connector at the proximal end of the
lead body and electrically coupling to the second pace/sense
electrode.
3. The lead of claim 2, wherein the first and second pace/sense
electrodes located between the first segment and the second segment
comprise one of or a combination of ring electrodes, hemispherical
electrodes, coil electrodes, partial-ring electrodes,
partial-hemispherical electrodes, partial-coil electrodes.
4. The lead of claim 1, further comprising at least one pace/sense
electrode located distal to the first segment of the defibrillation
electrode.
5. The lead of claim 1, further comprising at least one pace/sense
electrode located proximal to the second segment of the
defibrillation electrode.
6. The lead of claim 1, wherein the at least one pace/sense
electrode located between the first segment and the second segment
of the defibrillation electrode comprises a coil electrode or
partial-coil electrode.
7. The lead of claim 1, wherein the distance between the first
segment and the second segment is between approximately 1-3
centimeters (cm).
8. The lead of claim 1, wherein the distal portion of the lead is
arranged such that when the lead is implanted the at least one
pace/sense electrode and the defibrillation electrode are both
substantially centered over a ventricle of a heart of the
patient.
9. An implantable medical electrical lead comprising: an elongated
lead body having a distal portion and a proximal end; a connector
at the proximal end of the lead body; a defibrillation electrode
located along the distal portion of the lead body, wherein the
defibrillation electrode includes a first segment and a second
segment proximal to the first segment by approximately 1-3
centimeters (cm); and at least one pace/sense electrode located
between the first segment and the second segment of the
defibrillation electrode.
10. The lead of claim 9, further comprising an electrical conductor
extending from the proximal end of the lead body and electrically
coupling to the first segment and the second segment of the
defibrillation electrode.
11. The lead of claim 9, further comprising: a first electrical
conductor extending from the proximal end of the lead body and
electrically coupling to the first segment of the defibrillation
electrode; and a second electrical conductor extending from the
proximal end of the lead body and electrically coupling to the
second segment of the defibrillation electrode.
12. The lead of claim 9, wherein the at least one pace/sense
electrode comprises at least two pace/sense electrodes located
between the first segment and the second segment.
13. The lead of claim 9, wherein the at least one pace/sense
electrode located between the first segment and the second segment
of the defibrillation electrode comprises a coil electrode.
14. The lead of claim 9, further comprising at least one of a
pace/sense electrode located distal to the first segment of the
defibrillation electrode and a pace/sense electrode located
proximal to the second segment of the defibrillation electrode.
15. The lead of claim 9, wherein the distal portion of the lead is
configured such that when the lead is implanted the at least one
pace/sense electrode and the defibrillation electrode are both
substantially centered over a ventricle of a heart of the
patient.
16. An implantable cardioverter-defibrillator system comprising: an
implantable cardioverter-device (ICD) that includes a therapy
module configured to generate and deliver electrical stimulation
therapy; and an implantable medical electrical lead electrically
coupled to the therapy module, wherein the lead comprises: an
elongated lead body having a distal portion and a proximal end; a
connector at the proximal end of the lead body; a defibrillation
electrode located along the distal portion of the lead body,
wherein the defibrillation electrode includes a first segment and a
second segment proximal to the first segment by a distance; and at
least one pace/sense electrode located between the first segment
and the second segment of the defibrillation electrode.
17. The system of claim 16, wherein the lead further comprises an
electrical conductor extending from the proximal end of the lead
body and electrically coupling to the first segment and the second
segment of the defibrillation electrode.
18. The system of claim 16, wherein the lead further comprises: a
first electrical conductor extending from the proximal end of the
lead body and electrically coupling to the first segment of the
defibrillation electrode; and a second electrical conductor
extending from the proximal end of the lead body and electrically
coupling to the second segment of the defibrillation electrode, and
the ICD further comprises a switching array configured to
selectively couple the therapy module to any one of just the first
segment of the defibrillation electrode, just the second segment of
the defibrillation electrode, and both the first and second
segments of the defibrillation electrode simultaneously.
19. The system of claim 16, wherein the distance between the first
segment and the second segment is between approximately 1-3
centimeters (cm).
20. The system of claim 16, wherein the distal portion of the lead
is arranged such that when the lead is implanted the at least one
pace/sense electrode and the defibrillation electrode are both
substantially centered over a ventricle of a heart of the patient.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/984,148, filed on Apr. 25, 2014, the entire
content of which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present application relates to electrical stimulation
leads and, more particularly, electrical stimulation leads with
improved sensing and/or pacing capability for use in extravascular
applications.
BACKGROUND OF THE INVENTION
[0003] Malignant tachyarrhythmia, for example, ventricular
fibrillation (VF), is an uncoordinated contraction of the cardiac
muscle of the ventricles in the heart, and is the most commonly
identified arrhythmia in cardiac arrest patients. If this
arrhythmia continues for more than a few seconds, it may result in
cardiogenic shock and cessation of effective blood circulation. As
a consequence, sudden cardiac death (SCD) may result in a matter of
minutes.
[0004] In patients at high risk of ventricular fibrillation, the
use of an implantable cardioverter defibrillator (ICD) system has
been shown to be beneficial at preventing SCD. An ICD system
includes an ICD, which is a battery powered electrical stimulation
device, that may include an electrical housing electrode (sometimes
referred to as a can electrode), that is coupled to one or more
electrical stimulation leads. The electrical stimulation leads may
be placed within the heart, within vasculature near the heart
(e.g., within the coronary sinus), attached to the outside surface
of the heart (e.g., in the pericardium or epicardium), or implanted
subcutaneously above the ribcage/sternum. If an arrhythmia is
detected, the ICD may generate and deliver a pulse (e.g.,
cardioversion or defibrillation shock) via the electrical
stimulation leads to shock the heart and restore its normal
rhythm.
SUMMARY
[0005] Subcutaneously implanted electrical stimulation leads or
substernally implanted electrical stimulation leads do not
intimately contact the heart, but instead reside in a plane of
tissue or muscle between the skin and sternum for subcutaneous, or
reside in a plane of tissue or muscle between the sternum and the
heart for substernal. Due to the distance between the heart and
electrodes of the electrical stimulation leads, to achieve improved
pacing, sensing, and/or defibrillation, the pace/sense electrodes
and the defibrillation coil electrode should be positioned in the
plane of tissue such that the electrodes are located directly above
or proximate the ventricular surface of the cardiac silhouette. For
example, the electrode(s) used to deliver pacing pulses should be
positioned in a vector over substantially the center of the chamber
to be paced to produce the lowest pacing capture thresholds for
pacing. Likewise, the electrode(s) used to sense cardiac electrical
activity of the heart should be positioned over substantially the
center the chamber to be sensed to obtain the best sensed signal.
For shocking purposes, it is preferred to have the defibrillation
coil electrode positioned over substantially the center the chamber
to be shocked.
[0006] Current medical electrical lead designs used for
subcutaneous defibrillation include a single defibrillation coil
electrode located between a first pace/sense electrode distal to
the defibrillation coil and a second pace/sense electrode proximal
to the defibrillation coil. In such a configuration, it is not
possible to concurrently position both the defibrillation coil
electrode and one of the first and second pace/sense electrode(s)
substantially over the center the ventricle. Electrical stimulation
leads described herein are designed such that concurrent
positioning of the defibrillation electrode and the pace/sense
electrode is possible.
[0007] In one example, this disclosure is directed to an
implantable medical electrical lead comprising an elongated lead
body having a distal portion and a proximal end, a connector at the
proximal end of the lead body, a defibrillation electrode located
along the distal portion of the lead body, wherein the
defibrillation electrode includes a first segment and a second
segment proximal to the first segment by a distance, a first
electrical conductor extending from the proximal end of the lead
body and electrically coupling to the first segment and the second
segment of the defibrillation electrode, and at least one
pace/sense electrode located between the first segment and the
second segment of the defibrillation electrode.
[0008] In another example, this disclosure is directed to an
implantable medical electrical lead comprising an elongated lead
body having a distal portion and a proximal end, a connector at the
proximal end of the lead body, a defibrillation electrode located
along the distal portion of the lead body, wherein the
defibrillation electrode includes a first segment and a second
segment proximal to the first segment by approximately 1-3
centimeters (cm), and at least one pace/sense electrode located
between the first segment and the second segment of the
defibrillation electrode.
[0009] In a further example, this disclosure is directed to an
extravascular implantable cardioverter-defibrillator system
comprising an implantable cardioverter-device (ICD) that includes a
therapy module configured to generate and deliver electrical
stimulation therapy and an implantable medical electrical lead
electrically coupled to the therapy module. The lead includes an
elongated lead body having a distal portion and a proximal end, a
connector at the proximal end of the lead body, a defibrillation
electrode located along the distal portion of the lead body,
wherein the defibrillation electrode includes a first segment and a
second segment proximal to the first segment by a distance, and at
least one pace/sense electrode located between the first segment
and the second segment of the defibrillation electrode.
[0010] This summary is intended to provide an overview of the
subject matter described in this disclosure. It is not intended to
provide an exclusive or exhaustive explanation of the techniques as
described in detail within the accompanying drawings and
description below. Further details of one or more examples are set
forth in the accompanying drawings and the description below. Other
features, objects, and advantages will be apparent from the
description and drawings, and from the statements provided
below.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIGS. 1A and 1B are conceptual drawings illustrating various
views of a patient implanted with an example extravascular
implantable cardioverter-defibrillator (ICD) system.
[0012] FIG. 2 is a drawing illustrating a distal portion of an
example implantable medical electrical lead.
[0013] FIGS. 3A-3C are conceptual drawings illustrating various
views of a patient implanted with an example extravascular ICD
system in which a distal portion of the lead is implanted
substernally.
[0014] FIG. 4 is a block diagram illustrating components of an
example ICD.
DETAILED DESCRIPTION
[0015] FIGS. 1A and 1B are conceptual diagrams of an extravascular
implantable cardioverter-defibrillator (ICD) system 10
subcutaneously implanted within a patient 12. FIG. 1A is a front
view of ICD system 10 implanted within patient 12. FIG. 1B is a
side view of ICD system 10 implanted within patient 12. ICD system
10 includes an ICD 14 connected to a medical electrical lead 16.
FIGS. 1A and 1B are described in the context of an ICD system
capable of providing defibrillation and/or cardioversion shocks
and, in some instances, pacing pulses. However, the techniques of
this disclosure may also be used in the context of other
implantable medical devices configured to provide electrical
stimulation pulses to stimulate other portions of the body of
patient 12.
[0016] ICD 14 may include a housing that forms a hermetic seal that
protects components of ICD 14. The housing of ICD 14 may be formed
of a conductive material, such as titanium or titanium alloy, that
may function as a housing electrode (sometimes referred to as a can
electrode). ICD 14 may also include a connector assembly (also
referred to as a connector block or header) that includes
electrical feedthroughs through which electrical connections are
made between conductors of lead 16 and electronic components
included within the housing of ICD 14. As will be described in
further detail herein, housing may house one or more processors,
memories, transmitters, receivers, sensors, sensing circuitry,
therapy circuitry, power sources and other appropriate components.
The housing is configured to be implanted in a patient, such as
patient 12. ICD 14 is implanted subcutaneously on the left side of
patient 12 above the ribcage. ICD 14 may, in some instances, be
implanted between the left posterior axillary line and the left
anterior axillary line of patient 12. ICD 14 may, however, be
implanted at other subcutaneous locations on patient 12 as
described later.
[0017] Lead 16 includes an elongated lead body having a proximal
end that includes a connector (not shown) configured to be
connected to ICD 14 and a distal portion that includes electrodes
24 (formed by electrode segments 24A and 24B), 28, 29, and 30. Lead
16 extends subcutaneously above the ribcage from ICD 14 toward a
center of the torso of patient 12, e.g., toward xiphoid process 20
of patient 12. At a location near xiphoid process 20, lead 16 bends
or turns and extends superior subcutaneously above the ribcage
and/or sternum, substantially parallel to sternum 22. Although
illustrated in FIGS. 1A and 1B as being offset laterally from and
extending substantially parallel to sternum 22, lead 16 may be
implanted at other locations, such as over sternum 22, offset to
the right or left of sternum 22, angled lateral from sternum 22 at
either the proximal or distal end, or the like.
[0018] The elongated lead body of lead 16 contains a plurality of
elongated electrical conductors (not illustrated) that extend
within the lead body from the connector at the proximal lead end to
electrodes 24, 28, 29, and 30 located along the distal portion of
lead 16. The elongated lead body may have a generally uniform shape
along the length of the lead body. In one example, the elongated
lead body may have a generally tubular or cylindrical shape along
the length of the lead body. The elongated lead body may have a
diameter of between 3 and 9 French (Fr) in some instances. However,
lead bodies of less than 3 Fr and more than 9 Fr may also be
utilized. In another example, the distal portion (or all of) the
elongated lead body may have a flat, ribbon or paddle shape. In
this instance, the width across the flat portion of the flat,
ribbon or paddle shape may be between 1 and 3.5 mm. Other lead body
designs may be used without departing from the scope of this
disclosure. The lead body of lead 16 may be formed from a
non-conductive material, including silicone, polyurethane,
fluoropolymers, mixtures thereof, and other appropriate materials,
and shaped to form one or more lumens within which the one or more
conductors extend. However, the techniques are not limited to such
constructions.
[0019] The one or more elongated electrical conductors contained
within the lead body of lead 16 may engage with respective
electrodes 24, 28, 29, and 30. In one example, each of electrodes
28, 29, and 30 are electrically coupled to a respective conductor
within the lead body. Electrode segments 24A and 24B may be
electrically coupled to separate conductors, but may be capable of
being jumpered, tied or otherwise electrically connected such that
segments 24A and 24B may together form an anode or cathode of a
therapy vector. Alternatively, electrode segments 24A and 24B may
be electrically coupled to the same conductor. In any case, the
respective conductors may electrically couple to circuitry, such as
a therapy module or a sensing module, of ICD 14 via connections in
the connector assembly, including associated feedthroughs. The
electrical conductors transmit therapy from a therapy module within
ICD 14 to one or more of electrodes 24 (or one of segments 24A and
24B), 28, 29 and 30 and transmit sensed electrical signals from one
or more of electrodes 24 (or one of segments 24A and 24B), 28, 29
and 30 to the sensing module within ICD 14.
[0020] Defibrillation electrode 24 is located toward the distal
portion of defibrillation lead 16, e.g., toward the portion of
defibrillation lead 16 extending superior near sternum 22. As
indicated above, defibrillation electrode 24 is formed of a first
electrode segment 24A and a second electrode segment 24B separated
by a distance. In one example, first segment 24A and second segment
24B are each approximately 2-5 cm in length and the proximal end of
segment 24A is separated by approximately 1-3 cm from the distal
end of segment 24B. The first electrode segment 24A and the second
electrode segment 24B of defibrillation electrode 24 may in one
example be coil electrode segments. In other embodiments, however,
defibrillation electrode 24 may be a flat ribbon electrode, paddle
electrode, braided or woven electrode, mesh electrode, directional
electrode, patch electrode or other type of electrode that is
segmented in the manner described herein. Moreover, in other
examples, defibrillation electrode 24 may be constructed of more
than two segments.
[0021] A total length of defibrillation electrode 24 may vary
depending on a number of variables. Defibrillation electrode 24
may, in one example, have a total length (e.g., length of the two
segments combined) of between approximately 5-10 centimeters (cm).
However, defibrillation electrode 24 may have a total length less
than 5 cm and greater than 10 cm in other embodiments. In another
example, defibrillation electrode 24 may have a total length of
approximately 2-16 cm. In some instances, defibrillation segments
24A and 24B may be approximately the same length. In other
instances, one of defibrillation segments 24A and 24B may be longer
or shorter than the other one of the defibrillation segments 24A
and 24B.
[0022] Defibrillation lead 16 also includes electrodes 28, 29 and
30 located along the distal portion of defibrillation lead 16. In
the example illustrated in FIGS. 1A and 1B, electrodes 28 and 29
are located between defibrillation electrode segments 24A and 24B
and electrode 30 is located distal of defibrillation electrode
segment 24A. Electrodes 28 and 29 are illustrated as ring
electrodes and electrode 30 is illustrated as a hemispherical tip
electrode. However, electrodes 28, 29, and 30 may comprise any of a
number of different types of electrodes, including ring electrodes,
short coil electrodes, paddle electrodes, hemispherical electrodes,
directional electrodes, segmented electrodes, or the like. For
example, electrodes 28 and 29 may be formed of a conductive
material that only extends around a portion of the circumference of
the lead body, e.g., a half-ring electrode, quarter-ring electrode,
or other partial-ring electrode. In another example, electrodes 28
and 29 may be formed of conductive material that extends around the
entire circumference of the lead body, but may be partially coated
with an insulating material to form the half-ring electrode,
quarter-ring electrode, or other partial-ring electrode. Likewise,
electrode 30 may be formed into a partial-hemispherical electrode
in a similar manner as described above with respect to ring
electrodes 28 and 29. In still other instances, one or more of
electrodes 28, 29, and 30 may be segmented electrodes (e.g., half-
or quarter-ring or hemispherical electrodes) with separate
conductors connected to each of the segments or a single conductor
with a multiplexor or other switch to switch between the segmented
electrodes such that the segments may be used as individual
electrodes.
[0023] Electrodes 28, 29, and 30 of lead 16 may have substantially
the same outer diameter as the lead body. In one example,
electrodes 28, 29, and 30 may have surface areas between 1.6-150
mm.sup.2. Electrodes 28 and 30 may, in some instances, have
relatively the same surface area or different surface areas.
[0024] Electrodes 28 and 29 are spaced apart from one another along
the length of the lead. The spacing between electrodes 28 and 29
may be dependent upon the configuration of lead 16. In one example,
electrodes 28 and 29 are spaced apart by less than 2 cm. In some
instances, electrodes 28 and 29 may be spaced apart by less than 1
cm. In further instances, electrodes 28 and 29 may be spaced apart
from one another by more than 2 cm. Electrode 30 is spaced apart
from the distal end of defibrillation electrode segment 24A by a
distance, which may again be less than 2 cm. However, electrode 30
may be spaced apart from the distal end of defibrillation electrode
segment 24A by more than 2 cm.
[0025] The example dimensions provided above are exemplary in
nature and should not be considered limiting of the embodiments
described herein. In other embodiments, lead 16 may include less
than three pace/sense electrodes or more than three pace/sense
electrodes. In further instances, the pace/sense electrodes may be
located elsewhere along the length of lead 16, e.g., distal to
defibrillation electrode segment 24A or proximal to defibrillation
electrode segment 24B, with one or more of the sense/pace
electrodes being located between defibrillation electrode segments
24A and 24B. In other examples, defibrillation electrode may be
constructed of more than two segments, such as three segments with
electrode 28 located between the proximal segment and middle
segment and electrode 29 located between the middle segment and the
distal segment.
[0026] To achieve improved sensing and/or pacing, it is desirable
to have the pace/sense electrodes located substantially over the
chamber of heart 26 that is being paced and/or sensed. For example,
it is desirable to locate the pace/sense electrodes over a cardiac
silhouette of the ventricle as observed via an anterior-posterior
(AP) fluoroscopic view of heart 26 for sensing or pacing the
ventricle. Likewise, to achieve improved defibrillation therapy, it
is desirable to have the defibrillation electrode located
substantially over the chamber of heart 26 to which the
defibrillation or cardioversion shock is being applied, e.g., over
a cardiac silhouette of the ventricle as observed via an AP
fluoroscopic view of heart 26. In conventional subcutaneous lead
designs, it is only possible to position either the defibrillation
electrode or the sense electrode over the relevant chamber, but not
both.
[0027] Leads designed in accordance with any of the techniques
described herein can be implanted to achieve desirable electrode
positioning for both defibrillation and pacing/sensing. In
particular, lead 16 may be implanted such that electrodes 28 and 29
are substantially located over a cardiac silhouette of the
ventricle as observed via an AP fluoroscopic view of heart 26. In
other words, lead 16 may be implanted such that one or both of a
unipolar pacing/sensing vector from electrode 28 or 29 to a housing
electrode of ICD 14 are substantially across the ventricles of
heart 26. The therapy vector may be viewed as a line that extends
from a point on electrode 28 or 29, e.g., center of electrode 28 or
29, to a point on the housing electrode of ICD 14, e.g., center of
the housing electrode. In another example, the spacing between
electrodes 28 and 29 as well as the placement of lead 16 may be
such that a bipolar pacing vector between electrode 28 and
electrode 29 is centered or otherwise located substantially over
the ventricle.
[0028] Electrode 30 may be located over the cardiac silhouette of
the atrium or near the top of the cardiac silhouette of the atrium
as observed via an AP fluoroscopic view. As such, electrode 30 may
offer an alternate sensing vector and/or provide atrial pacing if
needed or desired.
[0029] Not only are electrodes 28 and 29 located over the
ventricle, but defibrillation electrode segments 24A and 24B are
substantially centered over the cardiac silhouette of the ventricle
as observed via an AP fluoroscopic view of heart 26. As such, the
therapy vector from defibrillation electrode segments 24A and 24B
to the housing of ICD 14 is substantially across the ventricles of
heart 26.
[0030] In some instances, electrodes 24, 28, 29, and/or 30 of lead
16 may be shaped, oriented, designed or otherwise configured to
reduce extra-cardiac stimulation. For example, electrodes 24, 28,
29, and/or 30 of lead 16 may be shaped, oriented, designed,
partially insulated or otherwise configured to focus, direct or
point electrodes 24, 28, 29, and/or 30 toward heart 26. In this
manner, pacing pulses delivered via lead 16 are directed toward
heart 26 and not outward toward skeletal muscle. For example,
electrodes 24, 28, 29, and/or 30 of lead 16 may be partially coated
or masked with a polymer (e.g., polyurethane) or another coating
material (e.g., tantalum pentoxide) on one side or in different
regions so as to direct the pacing signal toward heart 26 and not
outward toward skeletal muscle. In the case of a ring electrode,
for example, the ring electrode may be partially coated with the
polymer or other material to form a half-ring electrode,
quarter-ring electrode, or other partial-ring electrode.
[0031] ICD 14 may obtain sensed electrical signals corresponding
with electrical activity of heart 26 via a combination of sensing
vectors that include combinations of electrodes 28, 29, and/or 30
and the housing electrode of ICD 14. For example, ICD 14 may obtain
electrical signals sensed using a sensing vector between any two of
electrodes 28, 29 and 30 or obtain electrical signals sensed using
a sensing vector between any one of electrodes 28, 29, or 30 and
the conductive housing electrode of ICD 14. In some instances, ICD
14 may even obtain sensed electrical signals using a sensing vector
that includes one or both segments 24A or 24B of defibrillation
electrode 24 in combination with electrodes 28, 29, and/or 30, or
the housing electrode of ICD 14.
[0032] ICD 14 analyzes the sensed electrical signals obtained from
one or more of the sensing vectors of lead 16 to monitor for
tachyarrhythmia, such as ventricular tachycardia (VT) or
ventricular fibrillation (VF). ICD 14 may analyze the heart rate
and/or morphology of the sensed electrical signals to monitor for
tachyarrhythmia in accordance with any of a number of techniques
known in the art. One example technique for detecting
tachyarrhythmia is described in U.S. Pat. No. 7,761,150 to Ghanem
et al., entitled "METHOD AND APPARATUS FOR DETECTING ARRHYTHMIAS IN
A MEDICAL DEVICE." The entire content of the tachyarrhythmia
detection algorithm described in Ghanem et al. are incorporated by
reference herein in their entirety.
[0033] ICD 14 generates and delivers electrical stimulation therapy
in response to detecting tachycardia (e.g., VT or VF). In response
to detecting the tachycardia, ICD 14 may deliver one or more
cardioversion or defibrillation shocks via defibrillation electrode
24 of lead 16. ICD 14 may deliver the cardioversion or
defibrillation shocks using either of the electrode segments 24A
and 24B individually or together. ICD 14 may generate and deliver
electrical stimulation therapy other than cardioversion or
defibrillation shocks, including post-shock pacing using a therapy
vector formed from one or more of electrodes 24, 28, 28, 30, and
the housing electrode.
[0034] The examples illustrated in FIGS. 1A and 1B are exemplary in
nature and should not be considered limiting of the techniques
described in this disclosure. In other examples, ICD 14 and lead 16
may be implanted at other locations. For example, ICD 14 may be
implanted in a subcutaneous pocket in the right pectoral region. In
this example, defibrillation lead 16 may extend subcutaneously from
the device toward the manubrium of sternum 22 and bend or turn and
extend inferior from the manubrium to the desired location. In yet
another example, ICD 14 may be placed abdominally or
intrathoracically. Lead 16 may be implanted in other extravascular
locations as well. For instance, as described with respect to FIGS.
3A-3C, lead 16 may be implanted underneath the sternum/ribcage.
[0035] In the example illustrated in FIG. 1, system 10 is an ICD
system that provides cardioversion/defibrillation and, in some
instances, pacing therapy. However, these techniques may be
applicable to other cardiac systems, including cardiac
resynchronization therapy defibrillator (CRT-D) systems or other
cardiac stimulation therapies, or combinations thereof. For
example, ICD 14 may be configured to provide electrical stimulation
pulses to stimulate nerves, skeletal muscles, diaphragmatic
muscles, e.g., for various neuro-cardiac applications and/or for
sleep apnea or respiration therapy. As another example, lead 16 may
be placed further superior such that the defibrillation electrode
24 is placed substantially over the atrium of heart 26 to provide a
shock or pulse to the atrium to terminate atrial fibrillation (AF).
In still other examples, defibrillation lead 16 may include a
second defibrillation electrode (e.g., second elongated coil
electrode) near a proximal end of lead 16 or near a middle portion
of lead 16.
[0036] FIG. 2 is a conceptual diagram illustrating a distal portion
of another example implantable electrical lead 40 with improved
pacing and/or sensing capability for use in non-vascular,
extra-pericardial applications. Lead 40 can include one or more of
the structure and/or functionality of lead 16 of FIGS. 1A and 1B
(and vice versa). Repetitive description of like numbered elements
described in other embodiments is omitted for sake of brevity. Lead
40 may be used in place of lead 16 in ICD system 10 of FIGS. 1A and
1B.
[0037] Lead 40 conforms substantially with lead 16 of FIGS. 1A and
1B, but instead of having ring electrodes 28 and 29 located between
defibrillation segments 24A and 24B, lead 40 includes a pace/sense
coil electrode 42 between defibrillation segments 24A and 24B and a
pace/sense ring electrode 44 proximal to defibrillation electrode
segment 24B. Such a configuration may increase the surface area
located over the ventricles.
[0038] The length of pace/sense coil electrode 42 may be dependent
upon the spacing between defibrillation segments 24A and 24B. In
one example, defibrillation segments 24A and 24B may each have
lengths approximately equal to 4 cm and be spaced apart by a
distance greater than 1 cm. In this case, the pace/sense coil
electrode 42 may have a length of approximately 1 cm. However,
other spacings and lengths greater than or less than 1 cm may be
used, including the ranges provided above with respect to FIGS. 1A
and 1B. ICD 14 may be configured to sense and deliver pacing and/or
cardioversion/defibrillation using any combination of electrodes
24, 30, 42, 44, and the housing electrode. Lead 40 may be implanted
such that electrode 42 and defibrillation electrode 24 is
subtantially over the ventricular surface of the cardiac silhouette
in the same manner as described above with respsect to FIGS. 1A and
1B.
[0039] FIGS. 3A-3C are conceptual diagrams of patient 12 implanted
with another example ICD system 110. FIG. 3A is a front view of
patient 12 implanted with ICD system 110. FIG. 3B is a side view of
patient 12 implanted with ICD system 110. FIG. 3C is a transverse
view of patient 12 with ICD system 110. ICD system 110 can include
one or more of the structure and/or functionality of system 10 of
FIGS. 1A-1B (and vice versa). ICD system 110 of FIGS. 3A-3C is
illustrated with lead 16 for purposes of illustration, but may be
utilized with any of leads 16 or 40 or other similar lead.
Repetitive description of like numbered elements described in other
embodiments is omitted for sake of brevity.
[0040] ICD system 110 conforms substantially to ICD system 10 of
FIGS. 1A-1B, except defibrillation lead 16 of system 110 is
implanted at least partially underneath sternum 22 of patient 12.
Lead 16 extends subcutaneously from ICD 14 toward xiphoid process
20, and at a location near xiphoid process 20 bends or turns and
extends superior underneath/below sternum 22 within anterior
mediastinum 36. Anterior mediastinum 36 may be viewed as being
bounded laterally by pleurae 39, posteriorly by pericardium 38, and
anteriorly by sternum 22. In some instances, the anterior wall of
anterior mediastinum 36 may also be formed by the transversus
thoracis and one or more costal cartilages. Anterior mediastinum 36
includes a quantity of loose connective tissue (such as areolar
tissue), some lymph vessels, lymph glands, substernal musculature
(e.g., transverse thoracic muscle), branches of the internal
thoracic artery, and the internal thoracic vein. In one example,
the distal portion of lead 16 extends along the posterior side of
sternum 22 substantially within the loose connective tissue and/or
substernal musculature of anterior mediastinum 36. A lead implanted
such that the distal portion is substantially within anterior
mediastinum 36 will be referred to herein as a substernal lead.
Also, electrical stimulation, such as pacing, cardioversion or
defibrillation, provided by lead 16 implanted substantially within
anterior mediastinum 36 will be referred to herein as substernal
electrical stimulation, substernal pacing, substernal
cardioversion, or substernal defibrillation.
[0041] The distal portion of lead 16 is described herein as being
implanted substantially within anterior mediastinum 36. Thus,
points along the distal portion of lead 16 may extend out of
anterior mediastinum 36, but the majority of the distal portion is
within anterior mediastinum 36. In other embodiments, the distal
portion of lead 16 may be implanted in other non-vascular,
extra-pericardial locations, including the gap, tissue, or other
anatomical features around the perimeter of and adjacent to, but
not attached to, the pericardium or other portion of heart 26 and
not above sternum 22 or ribcage. As such, lead 16 may be implanted
anywhere within the "substernal space" defined by the undersurface
between the sternum and/or ribcage and the body cavity but not
including the pericardium or other portion of heart 26. The
substernal space may alternatively be referred to by the terms
"retrosternal space" or "mediastinum" or "infrasternal" as is known
to those skilled in the art and includes the anterior mediastinum
36. The substernal space may also include the anatomical region
described in Baudoin, Y. P., et al., entitled "The superior
epigastric artery does not pass through Larrey's space (trigonum
sternocostale)." Surg. Radiol. Anat. 25.3-4 (2003): 259-62 as
Larrey's space. In other words, the distal portion of lead 16 may
be implanted in the region around the outer surface of heart 26,
but not attached to heart 26.
[0042] The distal portion of lead 16 may be implanted substantially
within anterior mediastinum 36 such that electrodes 28 and 29 are
located near a ventricle of heart 26. To achieve improved sensing
and/or pacing, it is desirable to have the pace/sense electrodes
located substantially over the chamber of heart 26 that is being
paced and/or sensed. For instance, lead 16 may be implanted within
anterior mediastinum 36 such that 28 and 29 are located over a
cardiac silhouette of one or both ventricles as observed via an AP
fluoroscopic view of heart 26. In other words, lead 16 may be
implanted such that one or both of a unipolar pacing/sensing vector
from electrode 28 or 29 to a housing electrode of ICD 14 are
substantially across the ventricles of heart 26. In another
example, the spacing between electrodes 28 and 29 as well as the
placement of lead 16 may be such that a bipolar pacing vector
between electrode 28 and electrode 29 is centered or otherwise
located over the ventricle.
[0043] Likewise, to achieve improved defibrillation therapy, it is
desirable to have the defibrillation electrode located
substantially over the chamber of heart 26 to which the
defibrillation or cardioversion shock is being applied, e.g., over
a cardiac silhouette of the ventricle as observed via an AP
fluoroscopic view of heart 26. In conventional subcutaneous lead
designs, it is only possible to position either the defibrillation
electrode or the sense electrode over the relevant chamber, but not
both. Thus, not only are electrodes 28 and 29 located over the
ventricle, but due to the layout of the electrodes on the lead 16,
defibrillation electrode segments 24A and 24B are also
substantially centered over the cardiac silhouette of the ventricle
as observed via an AP fluoroscopic view of heart 26. In this
manner, lead 16 is designed to provide desirable electrode
positioning for both defibrillation and pacing/sensing
concurrently.
[0044] In the example illustrated in FIGS. 3A-3C, lead 16 is
located substantially centered under sternum 22. In other
instances, however, lead 16 may be implanted such that it is offset
laterally from the center of sternum 22. In some instances, lead 16
may extend laterally enough such that all or a portion of lead 16
is underneath/below the ribcage in addition to or instead of
sternum 22.
[0045] Placing lead 16 in the substernal space may provide a number
of advantages. For example, placing lead 16 in the substernal space
may significantly reduce the amount of energy that needs to be
delivered to defibrillate heart 26. In some instances, ICD 14 may
generate and deliver cardioversion or defibrillation shocks having
energies of less than 65 Joules (J), less than 60 J, between 35-60
J, and in some cases possibly less than 35 J. As such, placing
defibrillation lead 16 within the substernal space, e.g., with the
distal portion substantially within anterior mediastinum 36, may
result in reduced energy consumption and, in turn, smaller devices
and/or devices having increased longevity.
[0046] Another advantage of placing lead 16 in the substernal space
is that pacing, such as anti-tachycadia pacing (ATP), post-shock
pacing and, in some cases, bradycardia pacing, may be provided by
system 110. For example, ICD 14 may deliver one or more sequences
of ATP in an attempt to terminate a detected VT without delivering
a defibrillation shock. The ATP may be delivered via one or more
therapy vectors of lead 16, e.g., unipolar therapy vector, bipolar
pacing vector or multipolar pacing vector, formed using electrodes
28, 29, or 30, housing electrode of ICD 14, and/or defibrillation
electrode 24 or individual defibrillation electrode segments 24A or
24B. If the one or more sequences of ATP are not successful, it is
determined that ATP is not desired (e.g., in the case of VF), or
ICD 14 is not configured to deliver ATP, ICD 14 may deliver one or
more cardioversion or defibrillation shocks via defibrillation
electrode 24 of lead 16. ICD 14 may deliver the cardioversion or
defibrillation shocks using either of the electrode segments 24A
and 24B individually or together. ICD 14 may generate and deliver
electrical stimulation therapy other than ATP, cardioversion or
defibrillation shocks, including post-shock pacing, bradycardia
pacing, or other electrical stimulation therapy using a therapy
vector formed from one or more of electrodes 24, 28, 28, 30, and
the housing electrode.
[0047] FIG. 4 is a functional block diagram of an example
configuration of electronic components of an example ICD 14. ICD 14
includes a control module 60, sensing module 62, therapy module 64,
communication module 68, and memory 70. The electronic components
may receive power from a power source 66, which may be a
rechargeable or non-rechargeable battery. In other embodiments, ICD
14 may include more or fewer electronic components. The described
modules may be implemented together on a common hardware component
or separately as discrete but interoperable hardware or software
components. Depiction of different features as modules is intended
to highlight different functional aspects and does not necessarily
imply that such modules must be realized by separate hardware or
software components. Rather, functionality associated with one or
more modules may be performed by separate hardware or software
components, or integrated within common or separate hardware or
software components. FIG. 4 will be described in the context of ICD
being coupled to lead 16 for exemplary purposes only. However, ICD
14 may be coupled to other leads, such as lead 40 described herein,
and thus other electrodes, such as electrodes 42 and 44.
[0048] Sensing module 62 is electrically coupled to some or all of
electrodes 24 (or separately to segments 24A and/or 24B), 28, 29,
and 30 via the conductors of lead 16 and one or more electrical
feedthroughs, or to the housing electrode via conductors internal
to the housing of ICD 14. Sensing module 62 is configured to obtain
signals sensed via one or more combinations of electrodes 24 (or
segments 24A and/or 24B), 28, 29, and 30 and the housing electrode
of ICD 14 and process the obtained signals.
[0049] The components of sensing module 62 may be analog
components, digital components or a combination thereof. Sensing
module 62 may, for example, include one or more sense amplifiers,
filters, rectifiers, threshold detectors, analog-to-digital
converters (ADCs) or the like. Sensing module 62 may convert the
sensed signals to digital form and provide the digital signals to
control module 60 for processing or analysis. For example, sensing
module 62 may amplify signals from the sensing electrodes and
convert the amplified signals to multi-bit digital signals by an
ADC. Sensing module 62 may also compare processed signals to a
threshold to detect the existence of atrial or ventricular
depolarizations (e.g., P- or R-waves) and indicate the existence of
the atrial depolarization (e.g., P-waves) or ventricular
depolarizations (e.g., R-waves) to control module 60.
[0050] Control module 60 may process the signals from sensing
module 62 to monitor electrical activity of heart 26 of patient 12.
Control module 60 may store signals obtained by sensing module 62
as well as any generated EGM waveforms, marker channel data or
other data derived based on the sensed signals in memory 70.
Control module 60 may analyze the EGM waveforms and/or marker
channel data to detect cardiac events (e.g., tachycardia). In
response to detecting the cardiac event, control module 60 may
control therapy module 64 to deliver the desired therapy to treat
the cardiac event, e.g., defibrillation shock, cardioversion shock,
ATP, post-shock pacing, or bradycardia pacing.
[0051] Therapy module 64 is configured to generate and deliver
electrical stimulation therapy to heart 26. Therapy module 64 may
include one or more pulse generators, capacitors, and/or other
components capable of generating and/or storing energy to deliver
as pacing therapy, defibrillation therapy, cardioversion therapy,
cardiac resynchronization therapy, other therapy or a combination
of therapies. In some instances, therapy module 64 may include a
first set of components configured to provide pacing therapy and a
second set of components configured to provide defibrillation
therapy. In other instances, therapy module 64 may utilize the same
set of components to provide both pacing and defibrillation
therapy. In still other instances, therapy module 64 may share some
of the defibrillation and pacing therapy components while using
other components solely for defibrillation or pacing.
[0052] Control module 60 may control therapy module 64 to deliver
the generated therapy to heart 26 via one or more combinations of
electrodes 24 (or separately to segments 24A and/or 24B), 28, 29,
and 30 of lead 16 and the housing electrode of ICD 14 according to
one or more therapy programs, which may be stored in memory 70. In
instances in which control module 60 is coupled to a different
lead, e.g., lead 40, other electrodes may be utilized, such as
electrodes 42 and 44. Control module 60 controls therapy module 64
to generate electrical stimulation therapy with the amplitudes,
pulse widths, timing, frequencies, electrode combinations or
electrode configurations specified by a selected therapy
program.
[0053] Therapy module 64 may include a switch module to select
which of the available electrodes are used to deliver the therapy.
The switch module may include a switch array, switch matrix,
multiplexer, or any other type of switching device suitable to
selectively couple electrodes to therapy module 64. Control module
60 may select the electrodes to function as therapy electrodes, or
the therapy vector, via the switch module within therapy module 64.
In instances in which defibrillation segments 24A and 24B are each
coupled to separate conductors, control module 60 may be configured
to selectively couple therapy module 64 to either one of segments
24A or 24B individually or couple to both of the segments 24A and
24B concurrently. In some instances, the same switch module may be
used by both therapy module 64 and sensing module 62. In other
instances, each of sensing module 62 and therapy module 64 may have
separate switch modules.
[0054] In the case of pacing therapy being provided from the
substernal space, e.g., ATP, post-shock pacing, and/or bradycardia
pacing provided via electrodes 28, 29, and/or 30 (and possibly
defibrillation electrode 24 or segments 24A or 24B thereof) of lead
16, control module 60 controls therapy module 64 to generate and
deliver pacing pulses with any of a number of shapes, amplitudes,
pulse widths, or other characteristic to capture heart 26. For
example, the pacing pulses may be monophasic, biphasic, or
multi-phasic (e.g., more than two phases). The pacing thresholds of
heart 26 when delivering pacing pulses from the substernal space,
e.g., from electrodes 28, 29, and/or 30 substantially within
anterior mediastinum 36, may depend upon a number of factors,
including location, type, size, orientation, and/or spacing of
electrodes 28, 29, and 30, location of ICD 14 relative to
electrodes 28, 29, and 30, physical abnormalities of heart 26
(e.g., pericardial adhesions or myocardial infarctions), or other
factor(s).
[0055] The increased distance from electrodes 28, 29, and 30 of
lead 16 to the heart tissue may result in heart 26 having increased
pacing thresholds compared to transvenous pacing thresholds. To
this end, therapy module 64 may be configured to generate and
deliver pacing pulses having larger amplitudes and/or pulse widths
than conventionally required to obtain capture via leads implanted
within the heart (e.g., transvenous leads) or leads attached
directly to heart 26. In one example, therapy module 64 may
generate and deliver pacing pulses having amplitudes of less than
or equal to 8 volts and pulse widths between 0.5-3.0 milliseconds.
In another example, therapy module 64 may generate and deliver
pacing pulses having amplitudes of between 5 and 10 volts and pulse
widths between approximately 3.0 milliseconds and 10.0
milliseconds. In another example, therapy module 64 may generate
and deliver pacing pulses having pulse widths between approximately
2.0 milliseconds and 8.0 milliseconds. In a further example,
therapy module 64 may generate and deliver pacing pulses having
pulse widths between approximately 0.5 milliseconds and 20.0
milliseconds. In another example, therapy module 64 may generate
and deliver pacing pulses having pulse widths between approximately
1.5 milliseconds and 20.0 milliseconds.
[0056] Pacing pulses having longer pulse durations than
conventional transvenous pacing pulses may result in lower energy
consumption. As such, therapy module 64 may be configured to
generate and deliver pacing pulses having pulse widths or durations
of greater than two (2) milliseconds. In another example, therapy
module 64 may be configured to generate and deliver pacing pulses
having pulse widths or durations of between greater than two (2)
milliseconds and less than or equal to three (3) milliseconds. In
another example, therapy module 64 may be configured to generate
and deliver pacing pulses having pulse widths or durations of
greater than or equal to three (3) milliseconds. In another
example, therapy module 64 may be configured to generate and
deliver pacing pulses having pulse widths or durations of greater
than or equal to five (5) milliseconds. In another example, therapy
module 64 may be configured to generate and deliver pacing pulses
having pulse widths or durations of greater than or equal to ten
(10) milliseconds. In a further example, therapy module 64 may be
configured to generate and deliver pacing pulses having pulse
widths between approximately 3-10 milliseconds. In a further
example, therapy module 64 may be configured to generate and
deliver pacing pulses having pulse widths or durations of greater
than or equal to fifteen (15) milliseconds. In yet another example,
therapy module 64 may be configured to generate and deliver pacing
pulses having pulse widths or durations of greater than or equal to
twenty (20) milliseconds.
[0057] Depending on the pulse widths, ICD 14 may be configured to
deliver pacing pulses having pulse amplitudes less than or equal to
twenty (20) volts, deliver pacing pulses having pulse amplitudes
less than or equal to ten (10) volts, deliver pacing pulses having
pulse amplitudes less than or equal to five (5) volts, deliver
pacing pulses having pulse amplitudes less than or equal to two and
one-half (2.5) volts, deliver pacing pulses having pulse amplitudes
less than or equal to one (1) volt. In other examples, the pacing
pulse amplitudes may be greater than 20 volts. Typically the lower
amplitudes require longer pacing widths as illustrated in the
experimental results. Reducing the amplitude of pacing pulses
delivered by ICD 14 reduces the likelihood of extra-cardiac
stimulation and lower consumed energy of power source 66. Some
experimental results are provided later illustrating some example
combinations of pacing amplitudes and widths.
[0058] For pacing therapy provided from the subcutaneous placement
of lead 16 above the sternum and/or ribcage, pacing amplitudes and
pulse widths may vary.
[0059] In the case of cardioversion or defibrillation therapy,
e.g., cardioversion or defibrillation shocks provided by
defibrillation electrode segments 24A and/or 24B (individually or
together), control module 60 controls therapy module 64 to generate
cardioversion or defibrillation shocks having any of a number of
waveform properties, including leading-edge voltage, tilt,
delivered energy, pulse phases, and the like. Therapy module 64
may, for instance, generate monophasic, biphasic or multiphasic
waveforms. Additionally, therapy module 64 may generate
cardioversion or defibrillation waveforms having different amounts
of energy. As with pacing, delivering cardioversion or
defibrillation shocks from the substernal space, e.g., from
electrode 24 substantially within anterior mediastinum 36, may
reduce the amount of energy that needs to be delivered to
defibrillate heart 26. When lead 16 is implanted in the substernal
space, therapy module 64 may generate and deliver cardioversion or
defibrillation shocks having energies of less than 65 J, less than
60 J, between 40-50 J, between 35-60 J, and in some instances less
than 35 J. When lead 16 is implanted subcutaneously, ICD 14 may
generate and deliver cardioversion or defibrillation shocks having
energies around 65-80 J.
[0060] Therapy module 64 may also generate defibrillation waveforms
having different tilts. In the case of a biphasic defibrillation
waveform, therapy module 64 may use a 65/65 tilt, a 50/50 tilt, or
other combinations of tilt. The tilts on each phase of the biphasic
or multiphasic waveforms may be the same in some instances, e.g.,
65/65 tilt. However, in other instances, the tilts on each phase of
the biphasic or multiphasic waveforms may be different, e.g., 65
tilt on the first phase and 55 tilt on the second phase. The
example delivered energies, leading-edge voltages, phases, tilts,
and the like are provided for example purposes only and should not
be considered as limiting of the types of waveform properties that
may be utilized to provide substernal defibrillation via
defibrillation electrode 24.
[0061] Communication module 68 includes any suitable hardware,
firmware, software or any combination thereof for communicating
with another device, such as a clinician programmer, a patient
monitoring device, or the like. For example, communication module
68 may include appropriate modulation, demodulation, frequency
conversion, filtering, and amplifier components for transmission
and reception of data with the aid of antenna 72. Antenna 72 may be
located within connector block of ICD 14 or within housing ICD
14.
[0062] The various modules of ICD 14 may include any one or more
processors, controllers, digital signal processors (DSPs),
application specific integrated circuits (ASICs),
field-programmable gate arrays (FPGAs), or equivalent discrete or
integrated circuitry, including analog circuitry, digital
circuitry, or logic circuitry. Memory 70 may include
computer-readable instructions that, when executed by control
module 60 or other component of ICD 14, cause one or more
components of ICD 14 to perform various functions attributed to
those components in this disclosure. Memory 70 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), static non-volatile RAM (SRAM),
electrically-erasable programmable ROM (EEPROM), flash memory, or
any other non-transitory computer-readable storage media.
[0063] Various examples have been described. These and other
examples are within the scope of the following claims.
* * * * *