U.S. patent application number 14/257462 was filed with the patent office on 2014-11-06 for devices and techniques for anchoring an implantable medical device.
This patent application is currently assigned to Medtronic, Inc.. The applicant listed for this patent is Medtronic, Inc.. Invention is credited to Melissa G.T. Christie, Amy E. Thompson-Nauman.
Application Number | 20140330287 14/257462 |
Document ID | / |
Family ID | 51841837 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140330287 |
Kind Code |
A1 |
Thompson-Nauman; Amy E. ; et
al. |
November 6, 2014 |
DEVICES AND TECHNIQUES FOR ANCHORING AN IMPLANTABLE MEDICAL
DEVICE
Abstract
Anchoring mechanisms for an implantable electrical medical lead
that is positioned within a substernal space are disclosed. The
anchoring mechanisms fixedly-position a distal portion of the lead,
that is implanted in the substernal space.
Inventors: |
Thompson-Nauman; Amy E.;
(Ham Lake, MN) ; Christie; Melissa G.T.; (Andover,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medtronic, Inc. |
Minneapolis |
MN |
US |
|
|
Assignee: |
Medtronic, Inc.
Minneapolis
MN
|
Family ID: |
51841837 |
Appl. No.: |
14/257462 |
Filed: |
April 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61820024 |
May 6, 2013 |
|
|
|
Current U.S.
Class: |
606/129 ;
607/116 |
Current CPC
Class: |
A61N 1/057 20130101;
A61N 1/0573 20130101; A61N 1/05 20130101; A61N 2001/0578 20130101;
A61N 2001/058 20130101; A61N 1/3956 20130101 |
Class at
Publication: |
606/129 ;
607/116 |
International
Class: |
A61N 1/05 20060101
A61N001/05 |
Claims
1. An implantable medical system comprising: a stimulation therapy
generator; a first elongate lead coupled to the stimulation therapy
generator having a proximal end and a distal end; an electrode
coupled to the distal end of the first elongate lead; and an
anchoring mechanism disposed along a length of the first elongate
lead configured to fixedly-secure the first elongate lead within a
substernal space underneath the sternum.
2. The implantable medical system of claim 1, wherein the anchoring
mechanism comprises a reinforcement member coupled to the distal
end of the lead that is configured to prevent movement of the lead
responsive to a dislodgment force from the tissue at the implant
location.
3. The implantable medical system of claim 1, wherein the anchoring
mechanism comprises a canted distal portion formed at the distal
end of the lead such that the canted distal portion engages tissue
within the substernal space to anchor the lead.
4. The implantable medical system of claim 1, wherein the anchoring
mechanism comprises a distal section of the lead that is configured
having a material that includes a greater stiffness coefficient
relative to the proximal section of the lead.
5. The implantable medical system of claim 1, wherein the anchoring
mechanism is configured to position the electrode in a
pre-determined orientation relative to a target stimulation therapy
site that is not within the substernal space.
6. The implantable medical system of claim 1, wherein the anchoring
mechanism comprises a flange having at least one major surface that
is oriented in a parallel configuration with a length of the
lead.
7. The implantable medical system of claim 1, wherein the anchoring
mechanism is configured to fixedly-secure the first elongate lead
at an access point into the substernal space, wherein a distal end
of the lead is configured to be tunneled through a pathway across
subcutaneous tissue for insertion into the substernal space.
8. The implantable medical system of claim 1, wherein the anchoring
mechanism includes a porous structure disposed at the distal end of
the lead.
9. The implantable medical system of claim 8, wherein the anchoring
mechanism comprises an in-growth member having a substance
configured to promote tissue growth for anchoring the implantable
stimulation lead to tissue.
10. The implantable medical system of claim 1, wherein the
anchoring mechanism is slidingly-disposed along a length of a body
of the first elongate lead, and wherein the anchoring mechanism is
moveable along the length of the body during navigation of the
lead.
11. The implantable medical system of claim 1, wherein the
anchoring mechanism comprises a passive fixator disposed along a
length of a body of the first elongate lead and configured to
engage tissue.
12. The implantable medical system of claim 1, wherein the
anchoring mechanism comprises an active fixator disposed along a
length of a body of the first elongate lead and configured to
engage tissue.
13. The implantable medical system of claim 1, wherein the
anchoring mechanism comprises an expandable coil.
14. The implantable medical system of claim 1, wherein the
anchoring mechanism comprises an expandable porous structure having
pores for tissue engagement.
15. The implantable medical system of claim 1, wherein the first
elongate lead and the anchoring mechanism are configured for
deployment into the substernal space through a delivery system such
that the anchoring mechanism remains in the first constrained
configuration during delivery of the lead to the substernal space
and is released to the second expanded configuration subsequent to
release of the lead into the substernal space.
16. The implantable medical system of claim 1, further comprising a
second elongate lead coupled to the stimulation therapy generator
and wherein the second elongate is configured for implantation at a
subcutaneous implant location.
17. A method of implanting a medical system, comprising:
subcutaneously advancing a first lead through a subcutaneous space
from a subcutaneously positioned implantable medical device to an
access point into a substernal space; navigating a distal end of
the first lead to an implantation site within the substernal space;
placing the distal end of the first lead within the substernal
space; orienting a fixation element in a pre-determined direction
relative to the substernal space; and fixedly-securing a segment of
the first lead at the access point with a fixation element that
secures the lead at an intersection between the subcutaneous space
and the substernal space.
18. The method of implanting the medical system of claim 17,
wherein the orientation of the fixation element is configured to
conform to curvature of a transition from the subcutaneous tissue
into the substernal space.
19. The method of implanting the medical system of claim 17,
further comprising performing an incision at a xiphoid process of a
patient to create the access point into substernal space.
20. The method of implanting the medical system of claim 17,
further comprising anchoring the distal end of the first lead to
the tissue.
21. The method of implanting the medical system of claim 20,
wherein the anchoring comprises suturing the distal end to the
tissue.
22. The method of implanting the medical system of claim 20,
wherein the anchoring comprises deploying a fixation element for
coupling with the tissue.
23. The method of implanting the medical system of claim 22,
wherein the fixation element is selected from the group consisting
of a prong, burb, clip, screw, flange, disk, flap, and a porous
structure.
24. The method of implanting the medical system of claim 20,
wherein the anchoring comprises deploying an anchoring mechanism
oriented in a first retracted configuration into the substernal
space such that the deployed anchoring mechanism is oriented in a
second expanded configuration when positioned in the substernal
space.
25. The method of implanting the medical system of claim 20,
wherein the orientation of the anchoring mechanism triggers a
corresponding orientation of an electrode of the first lead towards
a target stimulation therapy site.
26. The method of implanting the medical system of claim 20,
wherein the anchoring mechanism is configured in a first retracted
configuration during the navigation of the lead and configured into
a second expanded configuration when the lead is placed within the
substernal space.
27. The method of implanting the medical system of claim 17,
wherein navigating the first lead comprises: inserting the first
lead into a delivery system having a distal end portion that is
positioned within the substernal space, wherein the distal end of
the delivery system comprises a sheath having a lumen into which
the first lead is disposed; advancing the distal end of the first
lead towards the distal end portion of the delivery system; and
retracting the delivery system over the first lead from the
substernal space.
28. The method of implanting the medical system of claim 17,
further comprising positioning an electrode disposed on the distal
end of the first lead such that a field of an electrical
stimulation applied through the electrode is directed toward a
stimulation site.
29. The method of implanting the medical system of claim 17,
further comprising subcutaneously advancing a second lead for
fixation in subcutaneous tissue, wherein the first lead delivers a
pacing stimulation therapy and the second lead delivers a
defibrillation stimulation therapy.
30. The method of implanting the medical system of claim 17,
wherein the first lead delivers a combination therapy including
pacing stimulation and defibrillation stimulation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority from U.S.
Provisional Application No. 61/820,024, filed on May 6, 2013, the
content of which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present application relates to implantable medical
devices. In particular, methods, techniques devices are disclosed
for anchoring implantable medical leads.
BACKGROUND OF THE INVENTION
[0003] Electrical stimulation of body tissue and organs is often
used as a method of treating various conditions. Such stimulation
is generally delivered by means of electrical contact between a
pulse generator device and a target site via one or more
implantable medical electrical leads connected to the pulse
generator device; implantable leads typically include one or more
stimulation electrodes joined to a distal portion of the lead,
which are positioned and anchored in proximity to the target
site.
[0004] In patients at high risk of ventricular fibrillation, the
use of an implantable cardioverter defibrillator (ICD) system has
been shown to be beneficial. An ICD system includes an ICD, which
is a small battery powered electrical shock device, may include an
electrical housing, or can electrode, that is coupled to one or
more implantable medical leads that are implanted within the heart.
If an arrhythmia is sensed, the ICD may send a pulse via the
implantable leads to shock the heart and restore its normal rhythm.
Owing to the inherent surgical risks in attaching and replacing
implantable leads directly within or on the heart, methods have
been devised to achieve a similar effect to that of a transvenous
ICD system that is connected directly to the heart without placing
implantable leads within the heart or attaching the leads directly
to the heart.
[0005] Subcutaneous implantable cardioverter-defibrillator (SubQ
ICD) systems have been devised to deliver electrical impulses to
the heart by the use of one or more implantable leads that are
placed subcutaneously on the torso. In order to effectively
electrically stimulate the heart, the distal end of the implantable
lead may be oriented longitudinally spanning from approximately the
xiphoid to the high sternal area.
[0006] Various implantable medical lead structures and methods for
positioning and anchoring lead electrodes in proximity to target
sites have been developed over the years. New structures and
methods are necessary to anchor lead electrodes for emerging
therapy delivery requirements.
SUMMARY
[0007] Aspects in accordance with principles of the present
invention relate to an implantable medical electrical lead for
applying electrical stimulation to bodily tissue. The implantable
lead is adapted to be introduced through an access point adjacent
to the sternum and a distal portion is navigated into the
substernal space. With this in mind, the implantable lead includes
a lead body and an anchoring assembly. The lead body has a proximal
section adapted to be electronically coupled to a power source and
a distal section forming at least one exposed electrode
surface.
[0008] In accordance with embodiments of the disclosure, the
anchoring assembly may be located along a length of the lead body
that is configured to be located within the substernal space, such
as at or near the distal lead end. In other embodiments, the
anchoring assembly may be located along a length of the lead body
that is configured to be located at or near the access point into
the substernal space.
[0009] Other aspects of the disclosure relate to a method of
anchoring an implantable lead system. The method comprises
subcutaneously advancing the lead to an access point into a
substernal space of a patient, navigating a distal end of the lead
to an implantation site within the substernal space, placing the
distal end of the lead within the substernal space, orienting a
fixation element in a pre-determined direction relative to the
substernal space, and fixedly-securing a segment of the lead at the
access point with a fixation element that secures the lead at an
intersection between the subcutaneous space and the substernal
space.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The following drawings are illustrative of particular
embodiments of the invention and therefore do not limit the scope
of the invention, but are presented to assist in providing a proper
understanding. The drawings are not to scale (unless so stated) and
are intended for use in conjunction with the explanations in the
following detailed description. The present invention will
hereinafter be described in conjunction with the appended drawings,
wherein like numerals denote like elements, and:
[0011] FIG. 1A is a front view of a patient implanted with
implantable cardiac system;
[0012] FIG. 1B is a side view the patient implanted with
implantable cardiac system 10;
[0013] FIG. 1C is a transverse view of the patient implanted with
implantable cardiac system;
[0014] FIG. 2 depicts an embodiment of a lead anchoring mechanism
of a lead of the implantable cardiac system;
[0015] FIG. 3 depicts an embodiment of a lead anchoring mechanism
of a lead of the implantable cardiac system;
[0016] FIG. 4 depicts an embodiment of a lead anchoring mechanism
of a lead of the implantable cardiac system;
[0017] FIG. 5 depicts an embodiment of a lead anchoring mechanism
of a lead of the implantable cardiac system;
[0018] FIG. 6 depicts an embodiment of a lead anchoring mechanism
of a lead of the implantable cardiac system; and
[0019] FIG. 7 is a flow diagram illustrating an exemplary method of
implanting a lead according to an embodiment.
DETAILED DESCRIPTION
[0020] The disclosure describes techniques, components, assemblies,
and methods for anchoring a lead in a patient's substernal space or
extra-pericardium, with the lead being attachable to a
subcutaneously implanted medical device. A distal end of the lead
is positioned at a target implant site and anchored therein.
[0021] In this disclosure, "substernal space" refers to the region
defined by the undersurface between the sternum and the body
cavity, but not including the pericardium. In other words, the
region is posterior to the sternum and anterior to the ascending
aorta. 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 region referred
to as the anterior mediastinum. 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. For ease of description, the term
substernal space will be used in this disclosure, it being
understood that the term is interchangeable with any of the other
aforementioned terms.
[0022] In this disclosure, the term "extra-pericardial" space
refers to region around the outer heart surface, but not within the
pericardial sac/space. The region defined as the extra-pericardial
space includes the gap, tissue, bone, or other anatomical features
around the perimeter of, and adjacent to the pericardium.
[0023] In this specification, "anchor" means to fix a position of
an object relative to tissue to minimize movement of the object
relative to the tissue. Thus, although there may be small movements
of the object relative to the tissue, arising for example from body
movements of the patient that give rise to small deflections of the
object within the tissue, the object is nevertheless "anchored" in
the tissue. It is to be understood that features of the various
exemplary embodiments described herein may be combined with each
other, unless specifically noted otherwise.
[0024] FIGS. 1A-C are conceptual diagrams of a patient 12 implanted
with an example implantable cardiac system 10. FIG. 1A is a front
view of patient 12 implanted with implantable cardiac system 10.
FIG. 1B is a side view patient 12 with implantable cardiac system
10. FIG. 1C is a transverse view of patient 12 with implantable
cardiac system 10.
[0025] Implantable cardiac system 10 includes an implantable
cardiac defibrillator (ICD) 14 connected to a first lead 16 and a
second lead 18. The first lead 16 and the second lead 18 may be
utilized to provide an electrical stimulation therapy such as
pacing or defibrillation. For example, lead 16 may provide
defibrillation therapy while lead 18 may provide pacing therapy, or
vice versa, while in other embodiments, both lead 16 and lead 18
may provide pacing therapy or defibrillation therapy. In the
example illustrated in FIGS. 1A-C ICD 14 is implanted
subcutaneously on the left midaxillary of patient 12. ICD 14 may,
however, be implanted at other subcutaneous locations on patient 12
as described later.
[0026] Lead 16 includes a proximal end that is connected to ICD 14
and a distal end that includes one or more electrodes. Lead 16
extends subcutaneously from ICD 14 toward xiphoid process 20. At a
location near xiphoid process 20, lead 16 bends or turns and
extends subcutaneously superior, substantially parallel to sternum
22. The distal end of lead 16 may be positioned near the second or
third rib. However, the distal end of lead 16 may be positioned
further superior or inferior depending on the location of ICD 14
and other factors. Although illustrated as being offset laterally
from and extending substantially parallel to sternum 22 in the
example of FIGS. 1A-C, lead 16 may be implanted over sternum 22,
offset from sternum 22, but not parallel to sternum 22 (e.g.,
angled lateral from sternum 22 at either the proximal or distal
end).
[0027] Lead 16 includes a defibrillation electrode 24, which may
include an elongated coil electrode or a ribbon electrode, toward
the distal end of lead 16. Lead 16 is placed such that a therapy
vector between defibrillation electrode 24 and a housing or can
electrode of ICD 14 is substantially across the ventricle of heart
26.
[0028] Lead 16 may also include one or more sensing electrodes,
such as sensing electrodes 28 and 30, located toward the distal end
of lead 16. In the example illustrated in FIGS. 1A-C, sensing
electrode 28 and 30 are separated from one another by
defibrillation electrode 24. ICD 14 may sense electrical activity
of heart 26 via a combination of sensing vectors that include
combinations of electrodes 28 and 30 and the housing or can
electrode of ICD 14. For example, ICD 14 may obtain electrical
signals sensed using a sensing vector between electrodes 28 and 30,
obtain electrical signals sensed using a sensing vector between
electrode 28 and the conductive housing or can electrode of ICD 14,
obtain electrical signals sensed using a sensing vector between
electrode 30 and the conductive housing or can electrode of ICD 14,
or a combination thereof. In some instances, ICD 14 may even sense
cardiac electrical signals using a sensing vector that includes
defibrillation electrode 24.
[0029] Lead 18 includes a proximal end that is connected to ICD 14
and a distal end that includes one or more electrodes. Lead 18
extends subcutaneously from ICD 14 toward xiphoid process 20. At a
location near xiphoid process 20 lead 18 bends or turns and extends
superior upward in the substernal space. In one example, lead 18
may be placed in the mediastinum 36 and, more particularly, in the
anterior mediastinum. The anterior mediastinum is bounded laterally
by pleurae 40, posteriorly by pericardium 38, and anteriorly by
sternum 22. Lead 18 may be implanted within the mediastinum such
that one or more electrodes 32 and 34 are located over a cardiac
silhouette of the ventricle as observed via fluoroscopy. In the
example illustrated in FIGS. 1A-C, lead 18 is located substantially
centered under sternum 22. In other instances, however, lead 18 may
be implanted such that it is offset laterally from the center of
sternum 22. Although described herein as being implanted in the
substernal space, the mediastinum, or the anterior mediastinum,
lead 18 may be implanted in other extra-pericardial locations.
[0030] Lead 18 includes electrodes 32 and 34 located near a distal
end of lead 18. Electrodes 32 and 34 may comprise ring electrodes,
hemispherical electrodes, coil electrodes, helical electrodes,
ribbon electrodes, or other types of electrodes, or combination
thereof. Electrodes 32 and 34 may be the same type of electrodes or
different types of electrodes. In the example illustrated in FIGS.
1A-C electrode 32 is a hemispherical electrode and electrode 34 is
a ring or coil electrode.
[0031] ICD 14 may deliver pacing pulses to heart 26 via a pacing or
therapy vector that includes any combination of one or both of
electrodes 32 and 34 and a housing electrode or can electrode of
ICD 14. For example, ICD 14 may deliver pacing pulses using a
pacing or therapy vector between electrodes 32 and 34, deliver
pacing pulses using a pacing or therapy vector between electrodes
32 and the conductive housing or can electrode of ICD 14, deliver
pacing pulses using a pacing or therapy vector between electrodes
34 and the conductive housing or can electrode of ICD 14, or a
combination thereof. In some instances, ICD 14 may deliver pacing
therapy via a therapy vector between one of electrode 32 (or
electrode 34) and defibrillation electrode 24. In still further
instances, ICD 14 may deliver pacing therapy via a therapy vector
between one of electrode 32 (or electrode 34) and one of sensing
electrodes 28 or 30. ICD 14 may generate and deliver the pacing
pulses to provide anti-tachycardia pacing (ATP), bradycardia
pacing, post shock pacing, or other pacing therapies or combination
of pacing therapies. In this manner, ATP therapy or post shock
pacing (or other pacing therapy) may be provided in an ICD system
without entering the vasculature or the pericardial space, nor
making intimate contact with the heart.
[0032] ICD 14 may generate and deliver pacing pulses with any of a
number of amplitudes and pulse widths to capture heart 26. The
pacing thresholds of heart 26 when delivering pacing pulses
substernally using lead 18 may depend upon a number of factors,
including location of electrodes 32 and 34, location of ICD 14,
physical abnormalities of heart 26 (e.g., pericardial adhesions),
or other factors. The pacing thresholds needed to capture heart 26
tend to increase with shorter pulse widths. In the case of ATP, ICD
14 may deliver pacing pulses having longer pulse widths than
conventional ATP pulses to reduce the amplitude of the pacing
pulses. For example, ICD 14 may be configured to deliver pacing
pulses having pulse widths or durations of greater than or equal to
one (1) millisecond. In another example, ICD 14 may be configured
to deliver pacing pulses having pulse widths or durations of
greater than or equal to ten (10) milliseconds. In a further
example, ICD 14 may be configured to deliver pacing pulses having
pulse widths or durations of greater than or equal to fifteen (15)
milliseconds. In yet another example, ICD 14 may be configured to
deliver pacing pulses having pulse widths or durations of greater
than or equal to twenty (20) milliseconds. 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. 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 extracardiac stimulation.
[0033] ICD 14 may sense electrical activity of heart 26 via a
combination of sensing vectors that include combinations of
electrodes 32 and 34 and the housing or can electrode of ICD 14.
For example, ICD 14 may obtain electrical signals sensed using a
sensing vector between electrodes 32 and 34, obtain electrical
signals sensed using a sensing vector between electrode 32 and the
conductive housing or can electrode of ICD 14, obtain electrical
signals sensed using a sensing vector between electrode 34 and the
conductive housing or can electrode of ICD 14, or a combination
thereof. In some instances, ICD 14 may sense electrical activity of
heart 26 via a sensing vector between one of electrode 32 (or
electrode 34) and electrodes 24, 28 and 30 of lead 16. ICD 14 may
deliver the pacing therapy as a function of the electrical signals
sensed via the one or more of the sensing vectors of lead 18.
Alternatively or additionally, ICD 14 may deliver the pacing
therapy as a function of the electrical signals sensed via one or
more of the sensing vectors of lead 16.
[0034] ICD 14 also analyzes the sensed electrical signals from one
or more of the sensing vectors of lead 18 and/or one or more of the
sensing vectors of lead 16 to detect tachycardia, such as
ventricular tachycardia or ventricular fibrillation. In some
instances, ICD 14 delivers one or more ATP therapies via the one or
more pacing or therapy vectors of lead 18 in response to detecting
the tachycardia in an attempt to terminate the tachycardia without
delivering a defibrillation shock. If the one or more ATP therapies
are not successful or it is determined that ATP therapy is not
desired, ICD 14 may deliver one or more defibrillation shocks via
defibrillation electrode 24 of lead 16.
[0035] The configuration described above in FIGS. 1A-1C is directed
to providing ventricular pacing via lead 18. In situations in which
atrial pacing is desired in addition to or instead of ventricular
pacing, lead 18 may be positioned further superior. A pacing lead
configured to deliver pacing pulses to both the atrium and
ventricle may have more electrodes. For example, the pacing lead
may have one or more electrodes located over a cardiac silhouette
of the atrium as observed via fluoroscopy and one or more
electrodes located over a cardiac silhouette of the ventricle as
observed via fluoroscopy. A pacing lead configured to deliver
pacing pulses to only the atrium may, for example, have one or more
electrodes located over a cardiac silhouette of the atrium as
observed via fluoroscopy. In some instances, two substernal pacing
leads may be utilized with one being an atrial pacing lead
implanted such that the electrodes are located over a cardiac
silhouette of the atrium as observed via fluoroscopy and the other
being a ventricle pacing lead being implanted such that the
electrodes are located over a cardiac silhouette of the ventricle
as observed via fluoroscopy.
[0036] 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. 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 within leads 16
and 18 and electronic components included within the housing. As
will be described in further detail herein, housing may house one
or more processors, memories, transmitters, receivers, sensors,
sensing circuitry, therapy circuitry and other appropriate
components. Housing 34 is configured to be implanted in a patient,
such as patient 12.
[0037] Leads 16 and 18 include a lead body that includes one or
more electrodes located near the distal lead end or elsewhere along
the length of the lead body. The lead bodies of leads 16 and 18
also contain one or more elongated electrical conductors (not
illustrated) that extend through the lead body from the connector
assembly of ICD 14 provided at a proximal lead end to one or more
electrodes of leads 16 and 18. The lead bodies of leads 16 and 18
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.
[0038] The one or more elongated electrical conductors contained
within the lead bodies of leads 16 and 18 may engage with
respective ones of electrodes 24, 28, 30, 32, and 34. In one
example, each of electrodes 24, 28, 30, 32, and 34 is electrically
coupled to a respective conductor within its associated lead body.
The respective conductors may electrically couple to circuitry,
such as a therapy module or a sensing module, of ICD 14 via
connections in connector assembly, including associated
feedthroughs. The electrical conductors transmit therapy from a
therapy module within ICD 14 to one or more of electrodes 24, 28,
30, 32, and 34 and transmit sensed electrical signals from one or
more of electrodes 24, 28, 30, 32, and 34 to the sensing module
within ICD 14.
[0039] The lead 18 further includes one or more anchoring
mechanisms that are positioned along the length of the lead body.
The anchoring mechanisms affix the lead 18 that is implanted in a
substernal space in a fixed location to prevent dislodging of the
lead 18 once it is implanted. For example, the lead 18 may be
anchored at one or more locations situated between the distal lead
end positioned within the substernal space of patient 12 and a
point along the length of the portion of the lead body at or near
the insertion point of the lead body into the substernal space. The
one or more anchoring mechanism(s) may either engage cartilage,
bone, fascia, muscle or other tissue of patient 12 or may simply be
wedged therein to affix the lead under the sternum to prevent
excessive motion or dislodgment. Furthermore, it should be
understood that various anchoring mechanisms described in this
disclosure may additionally be utilized for delivery of a
stimulation therapy as is known in the art.
[0040] In accordance with various embodiments, this disclosure
describes anchoring mechanisms that are integrated into the lead
body. In such embodiments, a portion or segment of the lead body
may be formed with materials that function to encase conductors and
other elements internal to the lead while also anchoring the lead
within the implant environment.
[0041] In alternative embodiments, anchoring mechanisms of the
disclosure are described as discrete elements that may be formed in
line with the lead body. In some embodiments, the discrete
components may be provided in a fixedly-secured relationship to the
lead body. In other embodiments, the anchoring mechanism may be
detachedly coupled in a sliding relationship over the lead
body.
[0042] The anchoring mechanisms may include a passive anchoring
mechanism, an active anchoring mechanism or a combination of both.
In one embodiment, the anchoring mechanism is coupled along a
length of the lead body and it may also function as an electrically
active element. Examples of passive anchoring mechanisms include
flanges, disks, pliant tines, flaps, porous structures such as a
mesh-like element that facilitates tissue growth for engagement,
bio-adhesive surfaces (such as those described in U.S. Pat. No.:
8,594,809, which is incorporated herein by reference in its
entirety), and/or any other non-piercing elements. Examples of
active anchoring mechanisms may include rigid tines, prongs, burbs,
clips, screws, and/or other projecting elements that pierce and
penetrate into tissue to anchor the lead. As another example of an
active anchoring mechanism, the lead may be provided with a side
helix for engaging tissue. It is contemplated that any of these
anchoring mechanisms will be formed from materials including shape
memory alloys such as Nitinol to facilitate the deployment of the
lead.
[0043] The various examples of the anchoring mechanisms may be
deployable. As such, the anchoring mechanism assumes a first state
during maneuvering of the lead (during which time the lead is
disposed within a lumen of a delivery system or over a guidewire or
stylet) to the desired implant location. Subsequently, the
anchoring mechanism assumes a second state following the release of
the lead from the delivery system into the substernal space to
thereby anchor the distal end portion of the lead body relative to
the adjacent tissue.
[0044] In addition or alternatively, the lead may be anchored
through a suture that fixedly-secures the lead to the cartilage,
musculature, tissue or bone at the access point into the substernal
space of patient 12. In some embodiments, the suture may be sewn to
the patient 12 through pre-formed suture holes to the patient
12.
[0045] As shown in FIG. 1A, an anchoring mechanism 50a or anchoring
mechanism 50b (collectively "anchoring mechanism 50") may be
provided along the lead body to couple the lead 18 at an access
point through which the distal end of the lead 18 is inserted into
the substernal space. The access point is any location that
provides access into the substernal space. In one exemplary
embodiment, the access point is adjacent to or below the xiphoid
process (also referred to as "subxiphoid"). The access point may
also be at the notch (not shown) that connects the xiphoid process
to the sternum. In other embodiments, the substernal space may also
be accessed through the manubrium.
[0046] An example of the anchoring mechanism 50a includes a suture
or clip or other fastener that anchors the lead body to the patient
12. The anchoring mechanism 50a embodied as a fastener may be
coupled directly to the lead body or to a suture sleeve such as
that described in U.S. Pat. No. 5,273,053, issued to Pohndorf and
incorporated herein by reference in its entirety. The anchoring
mechanism 50a is fixedly-coupled to cartilage, musculature, tissue
or bone at the entry point into the substernal space at or near the
access point at which site the body of the lead 18 transitions from
the subcutaneous tissue into the substernal space of patient
12.
[0047] In an embodiment, the anchoring mechanism 50a that is
positioned at the access point may further be formed to accommodate
the curvature of the patient 12 anatomy. In other words, the body
of the anchoring mechanism 50a embodied, for example as a suture
sleeve, may be malleable or pre-shaped to conform to the bend angle
of the site at which the lead 18 transitions from the subcutaneous
tissue into the substernal space of patient 12. As such, the suture
sleeve may include a segment having a preformed bend angle of
approximately 90 degrees. Thus, the anchoring sleeve may be
positioned partially in the subcutaneous tissue and partially
within the substernal space. The anchoring sleeve may be coupled to
the patient 12 at one or more points along the length of the
anchoring sleeve.
[0048] The anchoring mechanism 50a may further be constructed to
facilitate tissue in-growth for long-term fixation of the lead 18.
To promote such tissue in-growth, the anchoring mechanism 50a may
be formed having a multi-layer construction or having pores. In
some embodiments, the anchoring mechanism 50a may be constructed
having a cross-linked structure. In accordance with other
embodiments, the materials for construction of the anchoring
mechanism 50a having a multi-layer structure may include
bio-absorbable materials which will degrade a short time after
implant. The anchoring mechanism 50a may also include a collagen
layer which has been pre-treated to promote the tissue growth.
[0049] An example of the anchoring mechanism 50b may include a
fixation element that is disposed continuously or partially around
the body of lead 18 to couple the lead 18 to the access point. The
anchoring mechanism may be fixedly coupled to the lead or
slidingly-disposed over the lead, such as the anchoring member
described in U.S. Pat. No. 5,476,493 to Muff, which is configured
to be movable axially along the length of the lead body, to
facilitate positioning of the anchoring mechanism 50b at a point
suitable for affixation to tissue adjacent to the xiphoid process.
In other words, anchoring mechanism 50b may be disposed around the
lead body in a sliding relationship to facilitate navigation and
placement of the distal end of the lead into the substernal space
and the subsequent movement of the anchoring mechanism 50b to the
site for fixation.
[0050] In some embodiments, lead 18 further includes a reinforced
distal end 36 that is formed to facilitate anchoring of the lead 18
within the substernal space. The reinforced distal end 36 of the
lead 18 prevents flexing of the lead 18 responsive to body motions.
The distal end 36 may be formed from a material having a greater
stiffness coefficient relative to that of the material of the lead
body, or with a coating, or a resilient member--such as a
coil--coupled over the lead body, any of which is fabricated to
impart stiffness to the distal end 36. The reinforced distal end 36
exhibits characteristics that eliminate or minimize the motion of
the distal end of the lead. As such, the distal end 36 functions to
anchor the lead 18 within the tissue of patient 12.
[0051] In addition, the reinforced distal end 36 may be constructed
to facilitate tissue in-growth for long-term fixation of the lead
18. To promote such tissue in-growth, the distal end 36 may be
formed having a multi-layer construction or having pores. In some
embodiments, the distal end 36 may be constructed having a
cross-linked structure. In accordance with other embodiments, the
materials for construction of the distal end 36 having a
multi-layer structure may include bio-absorbable materials which
will degrade a short time after implant. The distal end 36 may also
include a collagen layer which has been pre-treated to promote the
tissue growth.
[0052] A backfilling process may be utilized to increase the
stiffness coefficient of the reinforced distal end 36 relative
other segments of the body of lead 18. For example, the lead 18
body may be formed with multiple insulative layers with the
backfill material--such as a medical adhesive or additional
material--being added to reinforce the distal end 36. In other
embodiments, the reinforced distal end 36 may be formed with
materials having an increased rigidity, relative to the rest of the
lead body. For example, the reinforced distal end 36 may be
fabricated from such materials as an ultra-high molecular density
polyethylene, polyester or other high tensile strength fiber or
plastic. In other examples, a lead body of lead 18 that is
manufactured of relatively soft plastics of low tensile strength
may be reinforced to provide a reinforced distal end 36 by
increasing the layers of material used in the region of distal end
36.
[0053] The examples illustrated in FIGS. 1A-C are exemplary in
nature and should not be considered limiting of the techniques
described in this disclosure. In other examples, ICD 14, lead 16,
and lead 18 may be implanted at other locations. For example, ICD
14 may be implanted in a subcutaneous pocket in the right chest. In
this example, lead 16 may be extend subcutaneously from the device
toward the manubrium of the sternum and bend or turn and extend
subcutaneously inferiorly from the manubrium of the sternum,
substantially parallel with the sternum and lead 18 may extend
subcutaneously from the device toward the manubrium of the sternum
to the desired location and bend or turn and extend substernally
inferiorly from the manubrium of the sternum to the desired
location.
[0054] In the example illustrated in FIG. 1, system 10 is an ICD
system that provides pacing therapy. However, these techniques may
be applicable to other cardiac systems, including cardiac
resynchronization therapy defibrillator (CRT-D) systems,
cardioverter systems, or combinations thereof.
[0055] In addition, it should be noted that system 10 may not be
limited to treatment of a human patient. In alternative examples,
system 10 may be implemented in non-human patients, e.g., primates,
canines, equines, pigs, bovines, ovines, and felines. These other
animals may undergo clinical or research therapies that may benefit
from the subject matter of this disclosure.
[0056] FIG. 2 depicts a lead anchoring mechanism 60 that includes a
plurality of struts 62 that are disposed over the lead 18 in a
sliding relationship and are configured to expand from a collapsed
configuration to an expanded configuration such that the plurality
of struts 62 expand to press against tissue surrounding the implant
location.
[0057] In one embodiment, the struts 62 may be displaced
distally--relative to a mid-axis of the lead 18--by employing a
deployment member (not shown) that causes both distal-ward movement
and expansive displacement of the struts 62 into the expanded
state. Other deployment mechanisms may include pneumatic activation
(fluid or gas activated), or direct connection via rods, or any
other type of proximally applied torque that causes force transfer
to deploy the struts 62.
[0058] According to one exemplary embodiment, the lead anchoring
mechanism 60 is made from a super-elastic material. The struts 62
may be formed from a tubular collar with material being removed to
form two or more expandable struts 62.
[0059] The lead 18 in FIG. 2 further includes a canted distal
portion 64. As illustrated, the body of lead 18 is pre-shaped to be
canted at an angle in the range of 10 degrees to 90 degrees,
relative to the remaining, proximal, portion of the lead body. The
pre-shape canted distal portion 64 may be constructed by providing
an inner layer having a shape memory material over this section of
the lead body. During delivery of the lead body, the lead 18 may be
positioned with a catheter or other delivery system that causes the
canted distal portion 64 to be straightened. Therefore, the bias of
the distal portion 64 is such that the introduction of a straight
stylet into a center lumen of the lead body or the insertion of
lead body into a guide catheter may cause the bend to be
straightened. Upon insertion into the substernal space, the canted
distal portion 64 permits the lead body to assume the
pre-determined shape thereby causing the distal portion 64 to
anchor to tissue within the substernal space.
[0060] Although the canted distal portion 64 is shown in
conjunction with the anchoring mechanism 60, it should be noted
that alternative embodiments of the lead 18 may simply include the
canted distal portion 64 without the anchoring mechanism 60.
[0061] In FIG. 3, an anchoring mechanism 70 is coupled to the
distal end of the lead 18. The anchoring mechanism 70 may be
configured as a flange or pad mounted to the distal end of the lead
18. The anchoring mechanism 70 includes a major surface 72 that is
greater than a minor surface (not shown) that is perpendicular to
the major surface. The major surface 72 is characterized by a width
that is greater relative to the width of the minor surface. When
coupled to the lead 18, the major surface is oriented in line with
an imaginary axis of the body of lead 18 running continuously
between the proximal end and the distal end. The cross-sectional
profile of the anchoring mechanism 70 is dimensioned to be greater
than a cross-sectional profile of the lead 18. For example, the
anchoring mechanism 70 may be configured having a width that is
greater than that of the lead 18 as viewed from a side perspective
or side cross-section.
[0062] Electrode 32 may be attached to the lead 18 overlying a
portion of lead anchoring mechanism 70. In this mounting
configuration, the electrode 32 may be oriented to direct the field
of the stimulation energy in a pre-determined direction at the
implant location.
[0063] In one embodiment, anchoring mechanism 70 may include a
mesh-like structure having pores that permit ingrowth of tissue
that affixes to the anchoring mechanism. In other embodiments, the
anchoring mechanism 70 may include a bioreactive adhesion layer
(not shown) such as that described in the U.S. Patent Application
No. 2009/0270962, with the bioreactive adhesion layer being coupled
to the surface of the anchoring mechanism 70. In such an
embodiment, a cover (not shown) may be utilized to seal off the
bioreactive adhesion layer from the external environment until the
anchoring mechanism is situated at an appropriate implant site.
[0064] FIG. 4 illustrates an anchoring mechanism 80 having a
combination passive fixation element 82 and an active fixation
element 84 coupled to the distal end of lead 18. The illustration
depicts the fixation element 82 and fixation element 84 in an
expanded or deployed configuration. The passive fixation element 82
may be a disk that expands radially relative to the width of the
lead body to define a circumference that is larger than the
circumference of the lead body. The anchoring mechanism 80 further
illustrates active fixation element 84 that may be a helix that
extends in axially from the distal end of the lead body and is
configured for insertion into tissue. The fixation element 84 may
be screwed out of the distal tip of the lead body, for example,
through a rotational force that is imparted by rotating the lead
body.
[0065] FIG. 5 illustrates an anchoring mechanism 90 coupled along a
length of the lead body. The anchoring mechanism 90 comprises a
side helix that engages with tissue. The side helix may be formed
as a coil wound over the lead body. Engagement of the tissue occurs
through protrusion of the side helix in a direction that is
perpendicular to an imaginary axis from the proximal to the distal
end of the lead.
[0066] FIG. 6 is a side view of anchoring mechanism 100 positioned
at a proximal end of electrode 32 of a lead of a medical device
according to an embodiment. The anchoring mechanism 100 is
positioned proximal from the electrode 32 on the lead body of lead
18 and includes proximal tines that are formed of flexible or
pliant material such as polymeric materials for example, as
silicone rubber or polyurethane to passively fixate to tissue. In
another embodiment, the tines may be formed of a rigid material
such as titanium or PEEK for active fixation to the tissue. During
deployment of the anchoring mechanism 100, the tines are folded
such that the tine elements are retracted or constrained against
the lead body. This may be accomplished by positioning the lead 18
within a lumen of a delivery system having a diameter smaller than
the width defined by the expanded tines. Upon delivery to the
proper location, the lead 18 is released from the delivery system
allowing the tines to return to their extended position whereby
they push against or pierce the tissue improving both acute and
chronic fixation.
[0067] FIG. 7 is a flow diagram illustrating an exemplary method of
implanting a lead according to an embodiment of the disclosure. In
particular, the method involves implantation of a medical lead in a
substernal space underneath the sternum and fixedly-securing the
distal end of the lead to patient tissue. Lead 18
[0068] (FIGS. 1-6) comprises one example of such a medical lead
that may be implanted in the substernal space.
[0069] The lead 18 is implanted in a region that is underneath the
sternum and within the mediastinum space. The mediastinum space may
include the region that is posterior to the sternum and anterior to
the pericardial sac from the xiphoid to the manubrium and bounded
laterally on the left and right by the internal thoracic arteries.
A lead implanted in the substernal space may provide a stimulation
therapy, such as a pacing therapy (including anti-tachy pacing,
post-shock pacing, chronic pacing) or a defibrillation therapy or
both.
[0070] A delivery system such as that disclosed in U.S. Patent
Application No.: 61/820,014, "Systems And Methods For Implanting A
Medical Electrical Lead Within A Substernal Space" which is hereby
incorporated by reference in its entirety, may be utilized to
implant the lead. When used, the delivery system is navigated into
the substernal space through an access point on the patient (202).
The navigation of the delivery system to the appropriate location
may be aided by various navigation aids discussed in the 61/820,014
application, including: a radiopaque marker that is visualized
through fluoroscopy, signals obtained from the distal end of the
delivery system body, and a directional indicator on the delivery
system. Again, the access point may be any location on the tissue
of the patient 12 where an incision is made to provide access into
the substernal space.
[0071] At task 204, a distal end of the lead is navigated to the
implantation site within the substernal space. The lead body may
extend from a stimulation therapy generating device, such as device
14, that is positioned subcutaneously, such as at the left
mid-axillary of the patient, and tunneled toward the xiphoid
process. The navigation of the lead from the xiphoid process into
the substernal space may be performed such that the distal end of
the lead is directed toward the jugular notch from the xiphoid
process in a generally axial direction.
[0072] The distal end of the lead is positioned within the
substernal space at a location over a cardiac silhouette of the
ventricle as observed via fluoroscopy. In particular, the
electrodes may be oriented towards a target stimulation site (206).
In one example, the desired orientation of the electrode may be
achieved by orienting an anchoring mechanism that is coupled to the
lead in a direction that causes the electrode to be positioned in a
direction towards the target stimulation site. For example, the
electrode may be formed integrally with an anchoring mechanism such
as that described in FIG. 3. In this configuration, the movement,
including rotational or longitudinal movement, of the anchoring
mechanism triggers movement of the electrode in the corresponding
direction which facilitates orientation of the electrode in the
desired direction.
[0073] At task 208, the lead is anchored to tissue surrounding the
implant environment. The lead may be anchored at the distal end,
proximate to the distal end or any other location along the length
of the lead between the access point into the xiphoid process and
the distal end of the lead. In doing so, the portion of the lead
within the substernal space is anchored to prevent dislodgment of
the lead.
[0074] In some embodiments, the anchoring mechanism may be
configured in a first retracted configuration during the navigation
of the lead and re-configured into a second expanded configuration
when the lead is released within the substernal space. In other
embodiments, the anchoring mechanism is retracted from an interior
portion of the lead. Additionally, the lead body may be sutured at
or near the xiphoid process to fixedly couple the lead.
[0075] At task 210, the delivery system is retracted from the
patient after the lead has been guided to the implant site.
[0076] As described herein, anchoring devices, systems and methods
in accordance with various embodiments are provided that facilitate
implantation and stabilization of a lead in the substernal space.
In alternative implementations, the devices, systems and methods
may be utilized for lead implantation and fixation in locations
other than the substernal space including but not limited to the
aforementioned extra-pericardial space.
[0077] Various examples have been described. It is contemplated
that the features described in the different embodiments may be
combined to create additional embodiments. All such disclosed and
other examples are within the scope of the following claims.
* * * * *