U.S. patent application number 12/433770 was filed with the patent office on 2009-11-05 for techniques for placing medical leads for electrical stimulation of nerve tissue.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Matthew D. Bonner, John E. Burnes, Shailesh Kumar V. Musley, Avram Scheiner, Eduardo N. Warman.
Application Number | 20090275996 12/433770 |
Document ID | / |
Family ID | 40688441 |
Filed Date | 2009-11-05 |
United States Patent
Application |
20090275996 |
Kind Code |
A1 |
Burnes; John E. ; et
al. |
November 5, 2009 |
TECHNIQUES FOR PLACING MEDICAL LEADS FOR ELECTRICAL STIMULATION OF
NERVE TISSUE
Abstract
This disclosure is directed to extra, intra, and transvascular
medical lead placement techniques for arranging medical leads and
electrical stimulation and/or sensing electrodes proximate nerve
tissue within a patient.
Inventors: |
Burnes; John E.; (Coon
Rapids, MN) ; Warman; Eduardo N.; (Maple Grove,
MN) ; Bonner; Matthew D.; (Plymouth, MN) ;
Scheiner; Avram; (Vadnais Heights, MN) ; Musley;
Shailesh Kumar V.; (Blaine, MN) |
Correspondence
Address: |
Medtronic, Inc.
710 Medtronic Parkway
Minneapolis
MN
55432
US
|
Assignee: |
Medtronic, Inc.
Minneapolis
MN
|
Family ID: |
40688441 |
Appl. No.: |
12/433770 |
Filed: |
April 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61007542 |
Apr 30, 2008 |
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61007543 |
Apr 30, 2008 |
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61190045 |
Apr 30, 2008 |
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61190046 |
Apr 30, 2008 |
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Current U.S.
Class: |
607/2 |
Current CPC
Class: |
A61N 1/0551 20130101;
A61N 1/0558 20130101; A61N 1/36128 20130101; A61M 25/09 20130101;
A61N 1/057 20130101; A61N 1/36125 20130101; A61N 1/05 20130101;
A61N 1/36053 20130101; A61N 1/36114 20130101; A61N 1/36085
20130101 |
Class at
Publication: |
607/2 |
International
Class: |
A61N 1/36 20060101
A61N001/36 |
Claims
1. An implantable medical system configured to deliver electrical
stimulation from within a lumen of a blood vessel within a patient
to nerve tissue located adjacent to and outside of the blood
vessel, the system comprising: a generally cylindrical expandable
and contractible lead member arranged within the blood vessel lumen
relative to the nerve tissue; and a plurality of electrodes
connected to the lead member; wherein the lead member is
temporarily deployable for testing multiple combinations of the
plurality of electrodes before deploying the lead member for
chronic therapy of the patient.
2. The system of claim 1, wherein the electrodes are arranged on an
exterior surface of the lead member in one or more columns
substantially parallel to a longitudinal axis of the lead
member.
3. The system of claim 1, wherein the electrodes are arranged on an
exterior surface of the lead member in one or more columns oriented
at an angle with respect to a longitudinal axis of the lead
member.
4. The system of claim 1, wherein the lead member comprises a
helical structure with the plurality of electrodes on the helical
structure.
5. The system of claim 4, wherein the electrodes are arranged on an
exterior of the helical structure in one or more columns generally
parallel to a trajectory of the helical ribbon.
6. The system of claim 4, wherein the helical structure is
expandable in a transverse direction relative to a longitudinal
axis of the lead member by bringing two ends of the lead member
closer to one another and contractible in the transverse direction
by pulling the two ends of the lead member away from each
other.
7. The system of claim 1, wherein the helical structure comprises
one of a helical ribbon or an elongated substantially cylindrical
helical structure.
8. The system of claim 1, wherein the lead member comprises a
stent.
9. The system of claim 8, wherein the stent lead member comprises a
mesh of material segments each of which is pivotally joined at
either end to another segment at a vertex to form a plurality of
polygons.
10. The system of claim 9, wherein the mesh stent lead member is
expandable and contractible by rotation of the material segments
with respect to each other at the plurality of vertices at which
the segments are pivotally joined.
11. The system of claim 9, wherein the electrodes are arranged at a
plurality of the vertices pivotally joining the material segments
forming the mesh stent lead member.
12. The system of claim 8, wherein the stent lead member comprises
a drug-eluting layer configured to interact with tissue of the
blood vessel.
13. The system of claim 1 further comprising a catheter configured
to hold the lead member in an at least partially contracted
state.
14. The system of claim 13, wherein the catheter comprises a lumen
in which the lead member is arranged and including one or more
apertures arranged over one or more of the plurality of electrodes
connected to the lead member.
15. The system of claim 1, wherein the nerve tissue comprises one
of a vagus nerve, a hypoglossal nerve, a nerve plexus, nerve
ganglia, or a vascular baroreceptors.
16. A method comprising: arranging a generally cylindrical
expandable and contractible lead member within a lumen of a blood
vessel adjacent target nerve tissue; temporarily deploying the
cylindrical lead member within the lumen relative to the nerve
tissue; energizing one or more electrodes connected to the
cylindrical lead member to deliver electrical stimulation from
within the blood vessel lumen to the nerve tissue; and chronically
deploying the cylindrical lead member in an expanded state within
the lumen relative to the nerve tissue.
17. The method of claim 16 further comprising determining an
efficacy of the nerve tissue stimulation.
18. The method of claim 17 further comprising: comparing the
efficacy of the nerve tissue stimulation to a threshold efficacy;
and redeploying the cylindrical lead member within the lumen
relative to the nerve tissue, if the efficacy of the nerve tissue
stimulation does not meet or exceed the threshold efficacy.
19. The method of claim 18, wherein, if the efficacy of the nerve
tissue stimulation does not meet or exceed the threshold efficacy,
then further comprising: energizing one or more electrodes
connected to the redeployed cylindrical lead member to deliver
electrical stimulation from within the blood vessel lumen to the
nerve tissue; and determining if an efficacy of the electrical
stimulation delivered by the redeployed cylindrical lead member
meets or exceeds the threshold efficacy.
20. The method of claim 16, wherein deploying the cylindrical lead
member within the lumen relative to the nerve tissue comprises:
orienting the electrodes connected to the cylindrical lead member
within the lumen relative to the nerve tissue; and selecting one or
more combinations of the plurality of electrodes to deliver
electrical stimulation from within the blood vessel lumen to the
nerve tissue.
21. The method of claim 20, wherein deploying the cylindrical lead
member within the lumen relative to the nerve tissue further
comprises expanding the cylindrical lead member.
22. The method of claim 16, wherein the nerve tissue comprises one
of a vagus nerve, a hypoglossal nerve, a nerve plexus, nerve
ganglia, or a vascular baroreceptor.
Description
[0001] This application claims the benefit of U.S. Provisional
Application Nos. 61/007,542, 61/007,543, 61/190,045, and
61/190,046, all of which were filed Apr. 30, 2008, and the entire
contents of each of which is incorporated herein by this
reference.
TECHNICAL FIELD
[0002] The disclosure relates to medical devices and, more
particularly, medical devices that deliver electrical stimulation
therapy.
BACKGROUND
[0003] A wide variety of implantable medical devices ("IMD") that
deliver therapy to or monitor a physiologic condition of a patient
have been clinically implanted or proposed for clinical
implantation in patients. Such devices may deliver therapy or
monitor the heart, muscle, nerve, the brain, the stomach or other
organs or tissues. In some cases, IMD's deliver electrical
stimulation therapy and/or monitor physiological signals via one or
more electrodes or sensor elements, at least some of which may be
included as part of one or more elongated implantable medical
leads. Implantable medical leads may be configured to allow
electrodes or sensors to be positioned at desired locations for
delivery of stimulation or sensing electrical activity or other
physiological parameters. For example, electrodes or sensors may be
located at a distal portion of the lead. A proximal portion of the
lead is coupled to an IMD housing, which contains electronic
circuitry such as stimulation generation and/or sensing circuitry.
In some cases, electrodes or sensors are positioned on an IMD
housing as an alternative or in addition to electrodes or sensors
deployed on one or more leads.
[0004] One example IMD is an electrical stimulation device directed
to nerve tissue stimulation, which is sometimes referred to as an
implantable nerve stimulator or implantable neurostimulator
("INS"). One particular application of nerve tissue stimulation is
vagal nerve stimulation. Vagal nerve stimulation may provide
therapeutic effects for heart failure, as well as other conditions
including, e.g., depression, epilepsy and various digestion
conditions. Some vagal nerve stimulators, as well as nerve trunk
stimulators in general, have employed cuff electrodes to surround
the nerve tissue and anchor the stimulator lead and/or electrodes
within a patient. Cuff electrodes have some disadvantages, however,
including, that such electrodes require relatively invasive
techniques for placing them within a patient. In the case of vagal
nerve stimulation, cuff electrodes require an incision in the neck
and dissection of the vagus from within the carotid sheath for
placement around the nerve. Additionally, cuff electrodes are known
to cause lesions or otherwise damage the nerve tissue, which may
lead to deleterious effects on nerve function, as well as the
development of scar tissue.
SUMMARY
[0005] In general, examples disclosed herein are directed to extra,
intra, and transvascular medical lead placement techniques for
arranging medical leads and electrical stimulation and/or sensing
electrodes proximate nerve tissue within a patient.
[0006] In one example, an implantable medical system is configured
to deliver electrical stimulation from within a lumen of a blood
vessel within a patient to nerve tissue located adjacent to and
outside of the blood vessel. The system includes a generally
cylindrical expandable and contractible lead member arranged within
the blood vessel lumen relative to the nerve tissue. A number of
electrodes are connected to the lead member. The lead member is
temporarily deployable for testing multiple combinations of the
plurality of electrodes before deploying the lead member for
chronic therapy of the patient.
[0007] In another example, a method includes arranging a generally
cylindrical expandable and contractible lead member within a lumen
of a blood vessel adjacent target nerve tissue. The cylindrical
lead member is temporarily deployed within the lumen relative to
the nerve tissue. One or more electrodes connected to the
cylindrical lead member are energized to deliver electrical
stimulation from within the blood vessel lumen to the nerve tissue.
The cylindrical lead member is chronically deployed in an expanded
state within the lumen relative to the nerve tissue.
[0008] The details of one or more examples according to this
disclosure 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
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1A is a conceptual diagram illustrating an example
therapy system including an implantable medical device (IMD) that
delivers cardiac and nerve tissue stimulation to a patient.
[0010] FIG. 1B is a conceptual diagram illustrating an example
therapy system including an implantable cardiac device (ICD) and an
implantable neurostimulator (INS).
[0011] FIG. 2 is a functional block diagram of the IMD of FIG.
1A.
[0012] FIG. 3 is a functional block diagram of an example medical
device programmer.
[0013] FIGS. 4 and 5 are schematic illustrations depicting relevant
human anatomy for lead placement techniques described herein.
[0014] FIG. 6 is a schematic illustration depicting a medical lead
placed extravascularly adjacent a vagus nerve.
[0015] FIG. 7 is a flow chart illustrating an example extravascular
lead placement method.
[0016] FIGS. 8A and 8B show two example sleeve anchors for use with
extravascular lead placement techniques according to this
disclosure.
[0017] FIG. 8C shows deployable lobe member for use with
extravascular lead placement techniques according to this
disclosure.
[0018] FIG. 9 is a schematic illustration depicting a medical lead
placed intravascularly within the internal jugular vein adjacent a
vagus nerve.
[0019] FIG. 10 is a flow chart illustrating an example
intravascular lead placement method.
[0020] FIG. 11 is a schematic illustration of a two dimensional
ultrasonic image generated by a sensor used in conjunction with the
intravascular lead placement arrangement shown in FIG. 9.
[0021] FIGS. 12A and 12B show several example deployment members
for use in intravascular lead placement methods and systems
according to this disclosure.
[0022] FIG. 13 is a schematic illustration depicting a medical lead
placed intravascularly and actively fixed to a wall of the internal
jugular vein adjacent a vagus nerve.
[0023] FIGS. 14A-14J are elevation front views of example anchors
that may be used alone or in combination to anchor or bias a
medical lead and/or electrode placed in accordance with examples
disclosed herein.
[0024] FIG. 15 is a schematic illustration depicting a cylindrical
lead member connected to a medical lead placed intravascularly
within the internal jugular vein adjacent a vagus nerve.
[0025] FIG. 16 is a flow chart illustrating an example method of
intravascularly placing the cylindrical lead member of FIG. 15.
[0026] FIGS. 17A and 17B are schematic illustrations of a
cylindrical lead member arranged within a delivery catheter.
[0027] FIGS. 18A-18D are schematic illustrations of different
examples of a cylindrical lead member that is expandable and
contractible for deployment and redeployment within a blood
vessel.
[0028] FIG. 19 is a schematic illustration depicting a medical lead
placed transvascularly through a wall of the internal jugular
toward a vagus nerve.
[0029] FIG. 20 is a flow chart illustrating an example
transvascular lead placement method.
[0030] FIGS. 21A-21D show several example deployment members for
use in transvascular lead placement methods and systems according
to this disclosure.
[0031] FIG. 22 shows one example of a deployment member that
employs a guide member constructed from a shape memory
material.
[0032] FIGS. 23A and 23B illustrate example arrangements of
electrode pairs in flanking, non-contacting relationship with a
vagus nerve.
DETAILED DESCRIPTION
[0033] In general, this disclosure is directed toward techniques
for placing medical leads proximate nerve tissue within a patient
for electrical stimulation of the tissue without the use of
potentially deleterious electrode configurations including e.g.,
cuff electrodes. Techniques disclosed herein are also generally
directed to flexible placement techniques and structures that
provide for one or more temporary lead placements and stimulation
tests, prior to chronically placing the leads within the patient
for nerve tissue stimulation. Furthermore, techniques according to
this disclosure are adapted to enable minimally invasive
introduction of the medical leads into the patient. Implantable
electrical stimulation systems and methods in accordance with this
disclosure may be used to deliver therapy to patients suffering
from conditions that range from chronic pain, tremor, Parkinson's
disease, and epilepsy, to urinary or fecal incontinence, sexual
dysfunction, obesity, spasticity, and gastroparesis. Specific types
of electrical stimulation therapies for treating such conditions
include, e.g., cardiac pacing, neurostimulation, muscle
stimulation, or the like.
[0034] Systems disclosed generally include one or more medical
leads adapted to be placed within a patient proximate nerve tissue
targeted for electrical stimulation therapy. The leads include one
or more electrodes that are arranged toward a distal end of the
leads. In some examples, the leads are anchored at least proximate
the distal end of the leads by or according to one or more
structures or techniques described in detail below. The medical
leads are connected to an electrical stimulator including a
processor adapted to carry out the electrical stimulation of the
target nerve tissue according to, e.g., one or more therapy
programs stored in non-volatile memory. The electrical stimulator
may include, generally, stimulation generation and/or sensing
circuitry. In some examples, the stimulator may also include
circuitry for cardiac rhythm therapy, e.g., one or more of pacing,
cardioversion, and/or defibrillation therapy, to a heart of a
patient. The stimulator may be located at a distance from the
target tissue site and coupled to a proximal end of the leads. In
another example, however, the electrical stimulator may include one
or more electrodes or sensors on its housing or a member, element
or structure coupled to the housing, may be placed in conjunction
with the electrodes or sensors proximate the target nerve tissue
site, and may be powered by, e.g., battery or a remote power
source. In some examples, the electrical stimulator may be powered
by radio frequency pulses delivered from either an external or a
subcutaneously implanted RF transmitter to a receiver unit arranged
with the stimulator, lead, and/or electrodes. In other examples,
some part of the stimulator, lead, or electrodes may be composed of
a piezoelectric material that can generate current when excited
mechanically by ultra sound waves transmitted from an external or
implanted source. In yet another example, two separate implantable
devices, e.g. an INS and a cardiac therapy device are individually
implanted and communicatively connected to one another. Placement
of the leads and electrodes proximate the nerve tissue includes
extravascular, intravascular, and transvascular placement
structures and techniques.
[0035] The techniques disclosed herein are described generally in
the context of stimulation of one of the vagus nerves on the vagal
nerve trunk in the neck of a human patient. Vagal nerve stimulation
is useful in treating various conditions including, e.g., heart
failure, depression, epilepsy, and various gastrointestinal
conditions. However, the methods and systems disclosed are also
applicable to stimulation and treatment of other nerve tissues that
are located in diverse locations. For example, the disclosed
techniques may be used in the stimulation of a hypoglossal nerve.
In other examples, a nerve plexus that forms a node of intersecting
nerves including, e.g., the cervical, brachial, lumbar, sacral, or
solar plexus may be stimulated using methods and systems according
to this disclosure. Additionally, the techniques may be used for
stimulation of nerve ganglia including, e.g., one or more ganglia
of a nerve plexus.
[0036] As an additional example, the techniques disclosed herein
may be used in the stimulation of vascular baroreceptors including,
e.g., carotid baroreceptors. Baroreceptors are sensors located in
blood vessels that detect the pressure of blood flowing
therethrough, and can send messages to the central nervous system
to increase or decrease total peripheral resistance and cardiac
output. The receptors function by detecting the amount a blood
vessel wall stretches, and sending a signal to the nervous system
in response to the detected expansion of the vessel. Baroreceptors
act as part of a negative feedback system called the baroreflex
that returns blood pressure to a normal level as soon as there is a
deviation from a typical pressure, such as, e.g., the mean arterial
blood pressure.
[0037] Prior extravascular placement techniques have involved
invasive implantation procedures because the target tissue, such as
a vagus nerve must be dissected to place and anchor the leads
proximate the nerve tissue. Additionally, prior extravascular
placement techniques commonly included lead electrode fixation at
the lead distal end using, e.g., cuff electrodes, which may have
deleterious effects over time including, e.g., nerve tissue
necrosis. Techniques described herein provide for extravascular
placement of medical leads for nerve tissue stimulation using
implantation procedures with reduced invasiveness and without the
need to anchor the leads at or very near their distal end. In
general, the disclosed techniques include placing a portion of a
medical lead having an electrode in an extravascular space within a
sheath of tissue within a patient, and adjacent nerve tissue that
is also within the sheath of tissue. The lead is anchored offset
from the electrode at least partially outside of the sheath. As
used herein, the term sheath of tissue generally refers to
constraining connective tissue that holds together different
biological structures within the body of a patient (e.g., a common
carotid sheath).
[0038] Intra or transvascular lead placement proximate the target
nerve tissue, on the other hand, generally requires minimally
invasive surgical techniques because the leads may be guided to the
site through a blood vessel, e.g., a vein or artery, that may be
readily accessible, e.g., transcutaneously through a small
incision. Intra and transvascular lead placement techniques
described herein may facilitate placing the distal end of the lead
in close proximity of the target nerve tissue, the relative
position of which with respect to an adjacent blood vessel may vary
from patient-to-patient. Additionally, guided transvascular lead
placement as described herein may avoid safety risks of such
procedures including, e.g., piercing adjacent vessels, such as an
artery.
[0039] Some example intravascular techniques include structures and
methods for deployment of one or more medical leads at a first
location, testing stimulation at the first location, and, depending
on the efficacy of the stimulation provided by electrodes on the
leads at the first location, redeploying the leads to a second
location. In one example, lead placement is improved by locating
target nerve tissue with a sensor including, e.g., an intravascular
ultrasound (IVUS) imaging system and/or measuring the efficacy of
test electrical stimulation pulses from an electrode on the lead
through a blood vessel adjacent the target tissue. After a
placement location is determined, one or more leads including one
or more electrodes may be deployed into the vessel and anchored to
a vessel wall near the target nerve tissue. In some examples, the
electrodes may be anchored with a fixation member that actively
engages tissue of the blood vessel wall. In another intravascular
placement example, an expandable and contractible generally
cylindrical lead member is temporarily deployable for testing
multiple electrode locations and combinations before deploying the
member for chronic stimulation of the target nerve tissue.
[0040] Transvascular techniques generally include improving lead
placement by locating target nerve tissue with a sensor including,
e.g., an IVUS imaging system, through a blood vessel adjacent the
target tissue. After a placement location is determined, one or
more leads including one or more electrodes may be deployed through
the vessel wall and anchored to the vessel wall or other tissue
near the target nerve tissue.
[0041] The extra, intra, and transvascular lead placement
techniques disclosed may also benefit, in some examples, from
electrode pairs arranged in flanking, non-contacting relationship
with the target nerve tissue. In one example, multiple leads are
arranged longitudinally on opposing sides of the target nerve
tissue, and include electrodes in non-contacting relationship with
the target nerve tissue. In another example, one lead that includes
multiple electrodes is employed such that at least two of the
electrodes are arranged in flanking, non-contacting relationship
with the target nerve tissue. Such flanking, non-contacting
electrode arrangements may provide one or more anode and cathode
electrode combinations for electrical stimulation across the target
nerve tissue without the deleterious effects of tissue contacting
techniques, such as may be caused by cuff electrodes.
[0042] FIG. 1A is a conceptual diagram illustrating an example
therapy system 10 that provides cardiac rhythm therapy and nerve
tissue stimulation therapy to patient 12. Therapy system 10
includes implantable medical device (IMD) 16, which is connected
(or "coupled") to leads 18, 20, 22, 28, and programmer 24. IMD 16
may be subcutaneously or submuscularly implanted in the body of a
patient 12 (e.g., in a chest cavity, lower back, lower abdomen, or
buttocks of patient 12).
[0043] IMD 16 may include a cardiac therapy module (not shown in
FIG. 1A) and a neurostimulation module (not shown in FIG. 1A)
enclosed within outer housing 44. The cardiac therapy module may
generate and deliver cardiac rhythm management therapy to heart 14
of patient 12, and may include, for example, an implantable
pacemaker, cardioverter, and/or defibrillator that provide therapy
to heart 14 of patient 12 via electrodes coupled to one or more of
leads 18, 20, and 22. In some examples, the cardiac therapy module
may deliver pacing pulses, but not cardioversion or defibrillation
pulses, while in other examples, the cardiac therapy module may
deliver cardioversion or defibrillation pulses, but not pacing
pulses. In addition, in further examples, cardiac therapy module
may deliver pacing, cardioversion, and defibrillation pulses. IMD
16 may deliver pacing that includes one or both of anti-tachycardia
pacing (ATP) and cardiac resynchronization therapy (CRT).
[0044] The neurostimulation module of IMD 16 may include a signal
generator that generates and delivers electrical stimulation to a
tissue site of patient 12, e.g., tissue proximate a vagus nerve or
other target nerve tissue of patient 12. In some examples, the
tissue site may include a peripheral nerve. As previously
indicated, in some examples, the tissue site may include a nerve
plexus that forms a node of intersecting nerves including, e.g.,
the cervical, brachial, lumbar, sacral, or solar plexus.
Additionally, the techniques may be used for stimulation of nerve
ganglia including, e.g., one or more ganglia of a nerve plexus. As
an additional example, the techniques disclosed herein may be used
in the treatment of vascular baroreceptors including, e.g., carotid
baroreceptors. In the example shown in FIG. 1A, electrodes of lead
28 are position to deliver electrical stimulation to target tissue
site 40 proximate a vagus nerve of patient 12. The vagus nerve is
primarily referred to herein as an example target nerve for
neurostimulation therapy.
[0045] In some examples, delivery of electrical stimulation to a
nerve tissue site may provide cardiac benefits to patient 12. For
example, delivery of electrical stimulation to a peripheral nerve
tissue site by IMD 16 may help treat heart failure. In addition,
delivery of electrical stimulation to a nerve of patient 12 may
help reduce or eliminate cardiovascular conditions such as
bradycardia, tachycardia, unhealthy cardiac contractions, ischemia,
inefficient heart pumping, inefficient collateral circulation of
heart 14 or cardiac muscle trauma. In addition, delivery of
electrical stimulation to a nerve may complement antitachycardia
pacing or provide back-up therapy to cardiac therapy delivered by
IMD 16. In some examples, IMD 16 may deliver electrical stimulation
therapy to a nerve of patient 12 via a lead implanted within
vasculature (e.g., a blood vessel) of patient 12. In other
examples, stimulation may be delivered by IMD 16 via a lead located
in extravascular tissue, e.g., when lead 28 is not implanted within
vasculature, such as within a vein or artery. Additional examples
include transvascular placement of a lead from within a blood
vessel of patient 12 adjacent the target tissue site, through the
wall of the blood vessel, and into an extravascular space, where
the target nerve tissue may be located.
[0046] In the example shown in FIG. 1A, the neurostimulation
therapy module of IMD 16 delivers electrical stimulation therapy to
a nerve of patient 12 via a lead implanted within vasculature
(e.g., a blood vessel) of patient 12. In particular, lead 28 is
implanted such that electrodes of lead 28 are positioned within
jugular vein 46 proximate the vagus nerve (not shown). Stimulation
of a parasympathetic nerve of patient 12 may help slow intrinsic
rhythms of heart 14, which may complement antitachyarrhythmia
therapy (e.g., antitachycardia pacing, cardioversion or
defibrillation) delivered by IMD 16. In this way, neurostimulation
therapy may help control a heart rate of patient 12 or otherwise
control cardiac function.
[0047] In other examples, electrodes of lead 28 may be positioned
to deliver electrical stimulation to any other suitable nerve
(e.g., a peripheral nerve) or nerve tissue in patient 12. In some
examples, the neurostimulation module of IMD 16 may deliver
electrical stimulation to other sympathetic or parasympathetic
nerves, baroreceptors, hypoglossal nerve, carotid sinus, or a
cardiac branch of the vagal trunk of patient 12 in order to
facilitate or compliment the delivery of therapy by the cardiac
therapy module of IMD 16.
[0048] In FIG. 1A, leads 18, 20, and 22 extend into the heart 14 of
patient 12 to sense electrical activity (electrical cardiac
signals) of heart 14 and/or deliver electrical stimulation (cardiac
therapy) to heart 14. In particular, right ventricular (RV) lead 18
extends through one or more veins (not shown), superior vena cava
(not shown), and right atrium 30, and into right ventricle 32. Left
ventricular (LV) coronary sinus lead 20 extends through one or more
veins, the vena cava, right atrium 30, and into coronary sinus 34
to a region adjacent to the free wall of left ventricle 36 of heart
14. Right atrial (RA) lead 22 extends through one or more veins and
the vena cava, and into right atrium 30 of heart 14. In other
examples, IMD 16 is additionally or alternatively coupled to
extravascular, e.g., epicardial or subcutaneous electrodes, via
leads for cardiac sensing and/or stimulation.
[0049] The cardiac therapy module may sense electrical signals
attendant to the depolarization and repolarization of heart 14 via
electrodes (not shown in FIG. 1A) coupled to at least one of the
leads 18, 20, 22. These electrical signals within heart 14 may also
be referred to as cardiac signals or electrical cardiac signals. In
some examples, the cardiac therapy module provides pacing pulses to
heart 14 based on the electrical cardiac signals sensed within
heart 14. The configurations of electrodes used by the cardiac
therapy module for sensing and pacing may be unipolar or bipolar.
The cardiac therapy module may also provide defibrillation therapy
and/or cardioversion therapy via electrodes located on at least one
of the leads 18, 20, 22 and one or more electrodes on housing 44 of
IMD 16. IMD 16 may detect arrhythmia of heart 14, such as
fibrillation of ventricles 32 and 36, and deliver defibrillation
therapy to heart 14 in the form of electrical pulses via one or
more of leads 18, 20, and 22. In some examples, the cardiac therapy
module may be programmed to deliver a progression of therapies,
e.g., pulses with increasing energy levels, until a fibrillation of
heart 14 is stopped. IMD 16 detects fibrillation employing one or
more fibrillation detection techniques known in the art.
[0050] The neurostimulation therapy module of IMD 16 may provide a
programmable stimulation signal (e.g., in the form of electrical
pulses or a continuous signal) that is delivered to target
stimulation site 40 by implantable medical lead 28, and more
particularly, via one or more stimulation electrodes carried by
lead 28. Proximal end 28A of lead 28 may be both electrically and
mechanically coupled to connector 42 of IMD 16 either directly or
indirectly (e.g., via a lead extension). In particular, conductors
disposed in the lead body of lead 28 may electrically connect
stimulation electrodes (and sense electrodes, if present) of lead
28 to IMD 16. In some examples, the neurostimulation therapy module
of IMD 16 may be electrically coupled to more than one lead
directly or indirectly (e.g., via a lead extension).
[0051] In the example of FIG. 1A, one or more electrodes of lead 28
are intravascularly implanted in patient 12 proximate to target
tissue stimulation site 40, e.g., proximate to a vagus nerve (not
shown). In particular, one or more neurostimulation electrodes of
lead 28 are implanted within jugular vein 46. Generally speaking,
implanting lead 28 near the vagus nerve of patient 12 may be useful
for delivering neurostimulation therapy to the vagus nerve without
requiring lead 28 to be subcutaneously implanted in patient 12.
Implanting lead 28 intravascularly within jugular vein 46 may
thereby be useful for reducing trauma to patient 12, e.g., because
lead 28 is not tunneled through subcutaneous tissue from IMD 16 to
target site 40. As described in greater detail with reference to
FIGS. 4-22, in other examples according to this disclosure, lead 28
may be extravascularly or transvascularly placed proximate target
tissue stimulation site 40, e.g., proximate a vagus nerve of
patient 12.
[0052] The distal portion of lead 28 may include one or more
electrodes (not shown) for delivering neurostimulation to target
stimulation site 40. Various electrode configurations of lead 28
are described in further detail with respect to FIGS. 2 and 3. In
some examples, lead 28 may also carry sense electrodes (not shown)
to permit IMD 16 to sense electrical signals, such as electrical
cardiac signals or electrical nerve signals from the vagus nerve or
other nerve tissue at which therapy is directed. Lead 28 may also
carry one or more sensors including, e.g., sense electrodes,
pressure sensors, ultrasound sensors, motion sensors, acoustic
sensors (heart rate), optical sensors, blood oxygen sensors,
posture state sensors, respiration sensors, venous biomarker
sensors, temperature sensors or other devices that may detect
physiological signals of patient 12 indicative of the efficacy of
neurostimulation therapy delivered to the patient by stimulation
electrodes.
[0053] In some examples, IMD 16 may deliver an electrical
stimulation signal via one or more of the electrodes of lead 28,
and analyze a physiological signal to detect a response to the
stimulation signal. In one such example, IMD 16 analyzes an
electrical nerve signal to detect a response to the stimulation
signal. The characteristic of the electrical nerve signal that
indicates the desired response to the delivery of the electrical
stimulation signal by the neurostimulation therapy module of IMD 16
may be, for example, an amplitude or frequency of the electrical
signal. The target characteristic of the electrical nerve signal
may be determined by a clinician at any suitable time when lead 28
is known to be in the desired location within patient 12, e.g.,
immediately after lead 28 is implanted within patient 12.
[0054] The electrical nerve signal may be an electrical signal
generated by a nerve, such as the target nerve for the
neurostimulation therapy or a branch thereof, in response to an
electrical stimulation signal delivered by the electrodes of lead
28. The response to the electrical stimulation signal may indicate,
for example, whether the neurostimulation signal captured the
nerve, and, therefore, is within a desired distance of the nerve.
In the example shown in FIG. 1A, the target nerve is a vagus nerve,
however, other types of nerves are contemplated for the
neurostimulation therapy. The electrical nerve signal may be sensed
between two or more electrodes of lead 28. IMD 16 may analyze the
electrical nerve signal for a response, for example, by measuring
an amplitude of the electrical nerve signal and comparing the
determined value to a threshold value. In this case, the electrical
nerve signal may have a baseline amplitude value and a response to
the stimulation signal may be characterized by a spike in
amplitude. The nerve response may be characterized by an amplitude
or other characteristics of a sensed electrical signal.
[0055] In the context of lead placement techniques disclosed
herein, sensed physiological signals may be used to determine the
efficacy of neurostimulation delivered by electrodes on lead 28 to
target nerve tissue. In some examples, lead 28 may be intra, extra,
or transvascularly placed proximate the nerve tissue and electrodes
on lead 28 may deliver test stimulation pulses to the nerve tissue
in order to test the placement of lead 28 within patient 12
relative to the nerve tissue. Various physiological signals may be
observed to measure the efficacy of the test stimulation, and
thereby the need to reposition lead 28 relative the target nerve
tissue. In some examples, test treatment efficacy may be indicated
by, e.g., ECG, heart rate, blood pressure, blood flow, blood oxygen
content, blood biomarker content, cardiac output, and/or breathing,
of patient 12. Additionally, T-wave morphology, heart rate
variability, contractility, and atrioventricular (AV) intervals may
be observed as an indication of test treatment efficacy. These and
other physiological signals may be detected in a variety of ways
including sensing the signals using sense electrodes, pressure
sensors, ultrasound sensors, motion sensors or other devices. In
other examples, physiological reactions of patient 12 may be
observed or measured by, e.g., a clinician.
[0056] In the case one or more sensors are employed to detect
physiological signals of patient 12, such devices may be arranged
in a variety of locations depending on device configuration and the
particular signal being detected. For example, the efficacy of
electrical stimulation of a vagus nerve may be measured by an
accelerometer arranged in the neck of patient 12 that determines if
stimulation of neck muscles or the phrenic nerve is occurring with
or instead of stimulation of a vagus nerve. In another example, a
pressure sensor arranged coincident with or connected to lead 28
may measure blood pressure by detecting the pressure within a
vessel in which lead 28 is placed. A pressure sensor, or other type
of physiological feedback sensor, may also, in some examples, be
connected to a delivery catheter configured to place lead 28 within
patient 12. In still another example, a cardiac therapy module
included in IMD 16 may employ one or more electrodes arranged on or
within heart 14 of patient 12 to, e.g., to monitor electrical
activity of heart 14 via an electrogram (EGM) or electrocardiogram
(ECG) signal. In other examples, venous biomarker sensors
configured to sense, e.g., inflammation markers or catecholamines
may be used to measure the effect of the stimulation and provide
feedback to IMD 16.
[0057] The extra, intra, and transvascular lead placement
techniques described herein are applicable for implantation of a
variety of implantable therapy systems including, e.g., system 10
of FIG. 1A, as well as systems that do not deliver cardiac
stimulation and/or provide cardiac sensing, or, as with the example
of FIG. 1B, deliver cardiac therapy using a device that is separate
from and in addition to an implantable neurostimulator.
[0058] As illustrated in FIG. 1A, system 10 may include a
programmer 24. IMD 16 may transmit information to and receive
information from programmer 24 related to the operation of IMD 16
and/or the delivery of therapy by IMD 16 to patient 12. Upon
receiving the information, programmer 24 may upload the received
information to a remote server, from which a clinician may access
the data (such as a remote server of the CareLink Network available
from Medtronic, Inc. of Minneapolis, Minn.). A clinician may also
access the information directly by interacting with programmer 24.
Furthermore, the clinician may program various aspects of the
operation of IMD 16 remotely by accessing a remote server that
communicates with IMD 16 via a network and programmer 24, or
locally program IMD 16 by physically interacting with programmer.
In some examples, the clinician may interact with programmer 24 to,
e.g., program select values for operational parameters of IMD
16.
[0059] In some examples, programmer 24 may be a handheld computing
device or a computer workstation. The user may use programmer 24 to
program aspects of the neurostimulation module. The therapy
parameters for the neurostimulation module of IMD 16 may include an
electrode combination for delivering neurostimulation signals, as
well as an amplitude, which may be a current or voltage amplitude,
and, if the neurostimulation module delivers electrical pulses, a
pulse width, and a pulse rate for stimulation signals to be
delivered to patient 12. The electrode combination may include a
selected subset of one or more electrodes located on implantable
lead 28 coupled to IMD 16 and/or a housing of IMD 16. The electrode
combination may also refer to the polarities of the electrodes in
the selected subset. By selecting particular electrode
combinations, a clinician may target particular anatomic structures
within patient 12. In addition, by selecting values for amplitude,
pulse width, and pulse rate, the physician can attempt to generate
an efficacious therapy for patient 12 that is delivered via the
selected electrode subset.
[0060] As another example, programmer 24 may be used by a user,
e.g., a clinician while a medical lead is placed within patient in
accordance with this disclosure to retrieve or view sensor feedback
during the implantation of the lead. In one example, a physician
uses programmer 24 to retrieve and/or view physiological signals
sensed by one or more sensors in response to test electrical
stimulation pulses delivered to patient 12 during the placement of
lead 12 adjacent a vagus nerve. In this manner, the physician
employs programmer 24 to determine the efficacy of the test
stimulation delivered by lead 28, and thereby the position of lead
28 relative to the vagus nerve. In another example, the physician
may also use programmer 24 to view an imaging field produced by an
IVUS imaging system connected to a delivery catheter used to place
lead 28, and electrodes connected thereto intra or transvascularly
within patient 12. In this manner, the physician may employ
programmer 24 to view, in real time, the placement of lead 28
within patient 12 relative to target nerve tissue and a blood
vessel in which or through which the lead is placed.
[0061] Programmer 24 may communicate with IMD 16 via wireless
communication using any techniques known in the art. Examples of
communication techniques may include, for example, low frequency or
radiofrequency (RF) telemetry, but other techniques are also
contemplated. In some examples, programmer 24 may include a
programming head that may be placed proximate to the patient's body
near the IMD 16 implant site in order to improve the quality or
security of communication between IMD 16 and programmer 24.
[0062] FIG. 1B is a conceptual diagram illustrating another example
therapy system 11 that includes separate implantable cardiac device
(ICD) 17 and implantable electrical stimulator 26. ICD 17 is
connected to leads 18, 20, and 22, and programmer 24, while
electrical stimulator 26 is coupled to lead 28 and may be
communicatively connected to both ICD 17 and programmer 24. ICD 17
may be, for example, a device that provides cardiac rhythm
management therapy to heart 14, and may include, for example, an
implantable pacemaker, cardioverter, and/or defibrillator, as
described above with reference to IMD 16.
[0063] In some examples, ICD 17 may, in addition to or instead of
delivering cardiac rhythm management therapy to heart 14, sense
electrical cardiac signals of heart 14 and/or other physiological
parameters of patient 12 (e.g., blood oxygen saturation, blood
pressure, temperature, heart rate, respiratory rate, and the like),
and store the electrical cardiac signals and/or other physiological
parameters of patient 12 for later analysis by a clinician. In such
examples, ICD 17 may be referred to as a patient monitoring device.
Examples of patient monitoring devices include, but are not limited
to, the Reveal Plus Insertable Loop Recorder, which is available
from Medtronic, Inc. of Minneapolis, Minn. For ease of description,
ICD 17 will be referred to herein as a cardiac rhythm management
therapy delivery device.
[0064] Therapy system 11 also includes implantable electrical
stimulator 26, which is coupled to lead 28. Electrical stimulator
26 may also be referred to as an implantable neurostimulator
("INS") 26. INS 26 may be any suitable implantable medical device
(IMD) that includes a signal generator that generates electrical
stimulation signals that may be delivered via one or more
electrodes on lead 28 to a nerve tissue site of patient 12, e.g.,
tissue proximate a vagus nerve.
[0065] In the example shown in FIG. 1B, electrodes of lead 28 are
positioned outside the vasculature of patient 12 to deliver
electrical stimulation to a vagus nerve (not shown) of patient 12.
As described above, in other examples, stimulation may be delivered
to a nerve tissue site via electrodes of an intravascular lead that
is implanted within vasculature. In still other examples,
stimulation may be delivered to a nerve tissue site within patient
12 via electrodes of a transvascular lead that is guided proximate
the target tissue site intravascularly, i.e., through a vein,
artery, or other blood vessel and then pierces a wall of the vessel
to be arranged adjacent the target tissue outside of the blood
vessel.
[0066] In the example shown in FIG. 1B, the components of ICD 17
and INS 26 are enclosed in separate housings, such that ICD 17 and
INS 26 are physically separate devices. In contrast to the example
of FIG. 1A in which the functionality of ICD 17 and INS 26 are be
performed by IMD 16 that includes both a cardiac therapy module and
an electrical stimulation therapy module. In applications in which
cardiac and neurostimulation therapy operate cooperatively or
sensing feedback is provided from heart 14 or a nerve tissue site
within patient 12, ICD 17 and INS 26 of FIG. 1B may communicate
with one another via one or more wireless communication techniques
instead of being directly linked within the same device housing as
in IMD 16 of therapy system 10 shown in FIG. 1A. For example, INS
26 may include one or more sensors that analyze an electrical nerve
signal to detect a response to the stimulation signal delivered by
ICD 17 and/or INS 26 to patient 12. ICD 17 and INS 26 may
communicate wirelessly using, e.g., low frequency or radiofrequency
(RF) telemetry.
[0067] FIG. 2 is a functional block diagram of an example
configuration of IMD 16 of FIG. 1A, which includes processor 100,
memory 102, cardiac therapy module 104, neurostimulation therapy
module 106, telemetry module 108, and power source 110. Cardiac
therapy module 104 includes signal generator 112 and sensing module
114. Neurostimulation therapy module 106 includes signal generator
116 and sensing module 118. The components of IMD 16 shown in FIG.
2 may be substantially enclosed within a common, hermetically
sealed outer housing 44 of IMD 16. In other examples including the
example shown in FIG. 1B, components for carrying out the functions
of cardiac therapy module 104 and neurostimulation therapy module
106 may be arranged in separate communicatively connected devices.
Although cardiac therapy module 104 and neurostimulation therapy
module 106 are illustrated as separate modules in FIG. 4, in some
examples, cardiac therapy module 104 and neurostimulation module
106 and their respective components may share circuitry. For
example, signal generators 112 and 116 may share common circuitry,
e.g., a stimulation engine, charging circuitry, capacitors, and the
like. Additionally, in some examples in which cardiac therapy
module 104 and neurostimulation module 106 deliver stimulation in
alternation, cardiac therapy module 104 and neurostimulation module
106 may share some or all stimulation generation circuitry.
Similarly, in some examples, sensing modules 114 and 118 may also
share common circuitry, such as an analog-to-digital converter and
the like.
[0068] Memory 102 includes computer-readable instructions that,
when executed by processor 100, cause IMD 16 and processor 100 to
perform various functions attributed to IMD 16 and processor 100
herein. In FIG. 2, memory 102 includes cardiac programs 122 that
cardiac therapy module 104 uses for generating cardiac rhythm
therapy for delivery to heart 14, and neurostimulation programs 124
that neurostimulation module 106 uses for generating
neurostimulation therapy for delivery to target tissue site 40.
Memory 102 may include any volatile, non-volatile, magnetic,
optical, or electrical media, such as a random access memory (RAM),
read-only memory (ROM), non-volatile RAM (NVRAM),
electrically-erasable programmable ROM (EEPROM), flash memory, or
any other digital media.
[0069] Processor 100 may include any one or more of a
microprocessor, a controller, a digital signal processor (DSP), an
application specific integrated circuit (ASIC), a
field-programmable gate array (FPGA), or equivalent discrete or
integrated logic circuitry. In some examples, processor 100 may
include multiple components, such as any combination of one or more
microprocessors, one or more controllers, one or more DSPs, one or
more ASICs, or one or more FPGAs, as well as other discrete or
integrated logic circuitry. The functions attributed to processor
100 herein may be embodied as software, firmware, hardware or any
combination thereof. Processor 100 may control cardiac therapy
module 104 to deliver stimulation therapy according to a selected
one or more of cardiac programs 122 stored in memory 102. In
addition, processor 100 may control neurostimulation module 106 to
delivering stimulation therapy according to a selected one or more
of neurostimulation programs 124 stored in memory 102.
Specifically, processor 100 may control cardiac therapy module 104
and/or neurostimulation module 106 to deliver electrical signals
via electrode combinations with amplitudes, frequency, electrode
polarities, and, in the case of stimulation pulses, pulse widths
specified by the selected one or more cardiac and neurostimulation
therapy programs 122, 124, respectively.
[0070] In the example shown in FIG. 2, cardiac therapy module 104
is electrically connected to electrodes 50, 52, 54, 56, 58, 60, 72,
74, and 76 of leads 18, 20, and 22 and housing electrode 68, and
neurostimulation module 106 is electrically connected to electrodes
80-83 of lead 28 and housing electrode 68. In other examples,
cardiac therapy module 104 and neurostimulation module 106 may be
coupled to any suitable number of electrodes, which may comprise a
greater number of electrodes or a fewer number of electrodes than
that shown in the example of FIG. 2.
[0071] Cardiac therapy module 104 is configured to generate and
deliver cardiac rhythm therapy to heart 14. For example, signal
generator 112 of cardiac therapy module 104 may generate and
deliver cardioversion or defibrillation shocks and/or pacing pulses
to heart 14 via a selected combination of electrodes 50, 52, 54,
56, 58, 60, 72, 74, and 76 and housing electrode 68. Signal
generator 112 of cardiac therapy module 104 is electrically coupled
to electrodes 50, 52, 54, 56, 58, 60, 72, 74, and 76, e.g., via
conductors of the respective lead 18, 20, 22, or, in the case of
housing electrode 68, via an electrical conductor disposed within
housing 44 of IMD 16.
[0072] Sensing module 114 monitors signals from at least one of
electrodes 50, 52, 54, 56, 58, 60, 72, 74, and 76 in order to
monitor electrical activity of heart 14, e.g., via an EGM or ECG
signal. Sensing module 114 may also include a switching module (not
shown in FIG. 4) to select a particular subset of available
electrodes to sense heart activity. In this manner, sensing module
114 may detect R-waves, P-waves, or other cardiac electrical
activity, and provide indications of their occurrence to processor
100. In some examples, processor may analyze a digitized the EGM or
ECG to detect these or other morphological features of the EGM or
ECG, to determine heart rates or intervals (e.g., R-R intervals) or
sizes of features such as T-waves or QRS complexes, or provide any
other known cardiac sensing and monitoring functionality.
[0073] Neurostimulation module 106 is configured to generate and
deliver electrical stimulation therapy to a target site within
patient 12 proximate nerve tissue, e.g., in order to modulate an
autonomic nervous system or vascular tone. Example stimulation
sites for neurostimulation module 106 include, but are not limited
to, tissue proximate a vagus nerve or braches of a vagus nerve of
patient 12. For example, signal generator 116 may generate
stimulation signals that are delivered to a tissue site proximate a
vagus nerve via a selected combination of electrodes 80-83 of lead
28 and/or housing electrode 68. The stimulation signals may be
pulses as primarily described herein, or continuous time signals,
such as sine waves.
[0074] Signal generator 116 may be a single or multi-channel signal
generator. In particular, signal generator 116 may be capable of
delivering, a single stimulation pulse, multiple stimulation
pulses, or a continuous signal at a given time via a single
electrode combination or multiple stimulation pulses at a given
time via multiple electrode combinations. In some examples,
however, neurostimulation therapy module 106 may be configured to
deliver multiple channels on a time-interleaved basis. In this
case, neurostimulation therapy module 106 may include a switching
module (not shown) that serves to time division multiplex the
output of the signal generator across different electrode
combinations at different times to deliver multiple programs or
channels of stimulation energy to patient 12.
[0075] Sensing module 118 of neurostimulation module 106 monitors
signals from at least one of electrodes 80-83 of lead 28 and
housing electrode 68 in order to monitor electrical activity of the
target nerve tissue, e.g. nerve signals of a vagus nerve. For
example, the amount of afferent and efferent signals of nerve
fibers can be monitored. In one such example, the nerve signals of
the left vagus nerve of patient 12 can be compared to the right
vagus nerve and therapy may be delivered by neurostimulation module
106 and/or cardiac therapy module 104 as commanded by processor 100
based at least in part upon this comparison of sensed nerve tissue
traffic. Conversely, in the context of lead placement techniques
described herein, therapy may be delivered to a vagus nerve (e.g.
left or right, or both) by one or more of electrodes 80-83 and
sensing module 118 of neurostimulation module 106 and/or sensing
module 114 of cardiac therapy module 104 as commanded by processor
100 may monitor afferent and efferent signals of vagal nerve fibers
to measure the efficacy of the therapy.
[0076] Telemetry module 108 includes any suitable hardware,
firmware, software or any combination thereof for communicating
with another device, such as programmer 24 (FIG. 1). Under the
control of processor 100, telemetry module 108 may receive downlink
telemetry from and send uplink telemetry to programmer 24 with the
aid of an antenna, which may be internal and/or external. Processor
100 may provide the data to be uplinked to programmer 24 and the
control signals for the telemetry circuit within telemetry module
108, e.g., via an address/data bus. In some examples, telemetry
module 108 may provide received data to processor 100 via a
multiplexer.
[0077] The various components of IMD 16 are coupled to power source
100, which may include a rechargeable or non-rechargeable battery
or a supercapacitor. A non-rechargeable battery may be selected to
last for several years, while a rechargeable battery may be
inductively charged from an external device, e.g., on a daily or
weekly basis. Power source 100 may also include an external or a
subcutaneously implanted RF transmitter that is configured to
deliver power via radio frequency pulses to a receiver arranged
with IMD 16 or one of the leads and/or electrodes of cardiac
therapy module 104 and neurostimulation therapy module 106. In
other examples, some part of IMD 16, or one of the leads or
electrodes may be composed of a piezoelectric material that can
generate current when excited mechanically by ultra sound waves
transmitted from an external or implanted source.
[0078] In some examples, data generated by sensing module 114 or
sensing module 118 and stored in memory 102 may be uploaded to a
remote server, from which a clinician or another user may access
the data to determine whether a potential sensing integrity issue
exists. An example of a remote server includes the CareLink
Network, available from Medtronic, Inc. of Minneapolis, Minn. An
example system may include an external device, such as a server,
and one or more computing devices that are coupled to IMD 16 and
programmer 24 via a network.
[0079] In addition to the examples of FIGS. 1A, 1B, and 2 including
cardiac therapy and neurostimulation therapy implemented in a
single or separate devices, examples according to this disclosure
also include a standalone INS device implanted within patient 12
and configured to function in a manner consistent with the
description of neurostimulation therapy module 106 of IMD 16 or INS
26 shown in FIGS. 1A and 2, and 1B respectively.
[0080] FIG. 3 is block diagram of example programmer 24 of FIGS. 1A
and 1B. As shown in FIG. 3, programmer 24 includes processor 130,
memory 132, user interface 134, telemetry module 136, and power
source 138. Programmer 24 may be a dedicated hardware device with
dedicated software for programming one or more of IMD 16, ICD 17,
or INS 26. Alternatively, programmer 24 may be an off-the-shelf
computing device running an application that enables programmer 24
to program one or more of IMD 16, ICD 17, or INS 26. For
convenience and clarity, the description of FIG. 3 will be made
with reference to the operation of programmer 24 with IMD 16.
However, the components and functions of programmer 24 described
herein are equally applicable to use with ICD 17, INS 26 or any
other implantable medical device that may benefit from the
functions provided by an external programming device such as
programmer 24.
[0081] A user may use programmer 24 to select therapy programs
(e.g., sets of stimulation parameters), generate new therapy
programs, modify therapy programs through individual or global
adjustments or transmit the new programs to IMD 16 (FIG. 1A). The
therapy programs may be for either or both cardiac therapy module
104 and neurostimulation module 106 (FIG. 2). A clinician, e.g.,
may interact with programmer 24 via user interface 134, which may
include a display to present a graphical user interface to a user,
and a keypad or another mechanism for receiving input from a
user.
[0082] Processor 130 can take the form of one or more
microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry,
or the like, and the functions attributed to processor 130 herein
may be embodied as hardware, firmware, software or any combination
thereof. Memory 132 may store instructions that cause processor 130
to provide the functionality ascribed to programmer 24 herein, and
information used by processor 130 to provide the functionality
ascribed to programmer 24 herein. Memory 132 may include any fixed
or removable magnetic, optical, or electrical media, such as RAM,
ROM, CD-ROM, hard or floppy magnetic disks, EEPROM, or the like.
Memory 132 may also include a removable memory portion that may be
used to provide memory updates or increases in memory capacities. A
removable memory may also allow patient data to be easily
transferred to another computing device, or to be removed before
programmer 24 is used to program therapy for another patient.
Memory 132 may also store information that controls therapy
delivery by IMD 16, such as stimulation parameter values.
[0083] Programmer 24 may communicate wirelessly with IMD 16, such
as using RF communication or proximal inductive interaction. This
wireless communication is possible through the use of telemetry
module 136, which may be coupled to an internal antenna or an
external antenna. An external antenna that is coupled to programmer
24 may correspond to the programming head that may be placed
proximate to the patient's body near the IMD 16 implant site, as
described above with reference to FIG. 1A. Telemetry module 136 may
be similar to telemetry module 108 of IMD 16 (FIG. 2).
[0084] Telemetry module 136 may also be configured to communicate
with another computing device via wireless communication
techniques, or direct communication through a wired connection.
Examples of local wireless communication techniques that may be
employed to facilitate communication between programmer 24 and
another computing device include RF communication according to the
802.11 or Bluetooth specification sets, infrared communication,
e.g., according to the IrDA standard, or other standard or
proprietary telemetry protocols. In this manner, other external
devices may be capable of communicating with programmer 24 without
needing to establish a secure wireless connection.
[0085] Power source 138 delivers operating power to the components
of programmer 24. Power source 138 may include a battery and a
power generation circuit to produce the operating power. In some
examples, the battery may be rechargeable to allow extended
operation of programmer 24.
[0086] FIGS. 4 and 5 are schematic illustrations depicting relevant
anatomy for lead placement techniques described herein. FIG. 4
illustrates vagus nerve 150 including many branches, such as
pharyngeal and laryngeal branches 152, cardiac branches 154, as
well as the gastric and pancreaticoduodenal branches (not
specifically labeled in FIG. 4). The illustration of FIG. 5 is a
cross section through the neck of patient 12 that shows carotid
sheath 156 in which is contained internal jugular vein 158, carotid
artery 160, and left and right vagus nerves 150L and 150R
respectively. Vagus nerve 150 originates in the brainstem, runs in
the neck through carotid sheath 156 with jugular vein 158 and
common carotid artery 160, and then adjacent to the esophagus to
the thoracic and abdominal viscera. Vagus nerve 150 provides the
primary parasympathetic nerve to the thoracic and most of the
abdominal organs. For example, vagus nerve 150 provides
parasympathetic innervation to the heart, and stimulation of the
nerve has been demonstrated to drive the parasympathetic nervous
system and thereby overcome an accelerated sympathetic tone, which
may be exhibited by patients suffering from various tachycardia
conditions, as well as heart failure. In one such tachycardia
application, the efferent fibers of the vagus nerve, such as one or
more superior and/or inferior cardiac branches may be electrically
stimulated to manage the accelerated arrhythmia. Vagal nerve
stimulation may also have afferent effects that result in nerve
reflex changes that affect heart rate. In addition to heart
innervations, vagus nerve 150 is responsible for such varied tasks
as gastrointestinal peristalsis, sweating, as well as muscle
movements related to speech. Electrical stimulation of vagus nerve
150 may be useful in treating, not only heart failure and
arrhythmia conditions, but also various other conditions including,
e.g., depression, epilepsy, and various gastrointestinal
conditions. To determine the need for and/or response to nerve
tissue stimulation according to methods and systems disclosed
herein, ECG, heart rate, blood pressure, blood flow, cardiac
output, and/or breathing, for instance, of patient 12 can be
sensed. Such patient feedback information can be gleaned from,
e.g., clinician observation, as well as employing one of
implantable cardiac device (ICD) 17 shown in FIG. 1B or cardiac
therapy module 104 shown in FIG. 2. Again, although the techniques
disclosed herein are described generally in the context of
stimulation of one of the vagus nerves on the vagal nerve trunk in
the neck of a human patient, the methods and systems disclosed are
also applicable to stimulation and treatment of other nerve tissues
that are located in diverse locations including, e.g.,
baroreceptors, hypoglossal nerves, and nerve plexus and
ganglia.
[0087] In addition to various biological structures of patient 12,
FIG. 5 shows intra and extravascularly placed leads 29' and 29''
respectively. Medical lead 29 is used for purposes of describing
placement techniques according to this disclosure. In general, lead
29 may correspond to lead 28 shown in FIGS. 1A and 1B above.
Intravascular lead 29' is arranged within internal jugular vein
158, while extravascular lead 29'' is arranged within carotid
sheath 156, adjacent vagus nerve 150. In addition to intra and
extravascular leads 29' and 29'' shown in FIG. 5, examples
according to this disclosure include transvascular placement of
lead 29 such that the lead passes from within a blood vessel of
patient 12 through a wall of the vessel to terminate adjacent a
target nerve tissue stimulation site. For example, lead 29 may be
guided proximate a target site intravascularly through internal
jugular vein 158 and then pierce a wall of jugular vein 158 to be
arranged adjacent vagus nerve 150. Although the examples disclosed
herein are generally described in the context of stimulating vagal
nerves in the neck of patient 12, lead 29 and electrodes attached
thereto may also be arranged for vagal nerve stimulation in, e.g.,
the thorax, and/or adjacent to the esophagus.
[0088] Extravascular lead placement techniques according to this
disclosure provide placement of leads for nerve tissue stimulation
and/or nerve signal sensing using implantation procedures with
reduced invasiveness and without the need to anchor the leads at or
very near their distal end. In general, the disclosed techniques
include placing a portion of a medical lead having an electrode in
an extravascular space within a sheath of tissue within a patient,
and adjacent nerve tissue that is also within the sheath of tissue.
The lead is anchored offset from the electrode at least partially
outside of the sheath.
[0089] FIGS. 6-8 illustrate examples of extravascular lead
placement techniques in the context of vagal nerve stimulation in a
human patient. FIG. 6 is a schematic illustration depicting lead 29
extravascularly placed adjacent vagus nerve 150 within carotid
sheath 156 in patient 12. After or during placement, lead 29 may be
connected to IMD 16 or INS 26 similar to lead 28 shown in FIGS. 1A
and 1B respectively. FIG. 7 is a flow chart illustrating an example
method of placing lead 29 in accordance with the example of FIG. 6.
The example method of FIG. 7 generally includes placing a portion
of a medical lead having an electrode electrically connected
thereto in an extravascular space adjacent nerve tissue within a
sheath of tissue within a patient (180), anchoring the lead offset
from the electrode outside of the sheath, (182), and stimulating
the nerve tissue (184). One example of the method illustrated in
FIG. 7 will be described in the context of the example lead
placement shown in FIG. 6.
[0090] The arrangement shown in FIG. 6 includes lead 29, electrodes
170, and anchor 172. Electrodes 170 are connected to and arranged
toward a distal end of lead 29. The example of FIG. 6 also includes
biasing member 176 and deployable lobe member 178 connected to lead
29 to bias and/or stabilize lead 29 and electrodes 170 toward vagus
nerve 150. Although the example of FIG. 6 shows four electrodes
170, other examples may include fewer or more electrodes connected
to lead 29 and, in some cases, other leads in addition to lead 29.
In some examples, electrodes 170 may include multiple types
including, e.g., electrode pads on a paddle lead, circular (e.g.,
ring) electrodes surrounding the body of leads 16, conformable
electrodes, segmented electrodes, or any other type of electrodes
capable of forming unipolar, bipolar or multipolar electrode
configurations for delivering nerve tissue stimulation therapy to
patient 12. In some examples including ring electrodes, electrodes
170 may be arranged on lead 29 with part of the rings electrically
insulated to limit the spread of the stimulating field so that only
a portion of the electrodes and electrical stimulation may be
directed at vagus nerve 150.
[0091] The distal end of lead 29 to which electrodes 170 are
attached is arranged within carotid sheath 156, adjacent vagus
nerve 150. Biasing member 176 and deployable lobe member 178 are
arranged at the distal end of lead 29 and bias lead 29 toward vagus
nerve 150 by exerting a force on surrounding tissue including,
e.g., internal jugular vein 158. A proximate end of lead 29 (not
shown in FIG. 6) may be connected to IMD 16 (see FIG. 1A). Anchor
172 is connected to lead 29 offset from the distal end of lead 29
outside of carotid sheath 156. Anchor 172 may be any suitable
fixation element that stabilizes the placement of lead 29 and
electrodes 170 within sheath 156 adjacent vagus nerve 150. For
example, anchor 172 may be one of a variety of sutureless fixation
elements connected to lead 29 that are configured to engage tissue
of patient 12 outside of carotid sheath 156. In one example, one or
more tines or barbs may protrude from lead 29 to pierce and thereby
attach lead 29 to tissue of patient 12 outside of sheath 156. In
addition to or instead of sutureless anchors, anchor 172 may
include various fixation elements that engage lead 29 and are
configured to be sutured by a clinician to the tissue of patient 12
outside of carotid sheath 156. Additionally, in some examples,
anchor 172 may include a sleeve configured to receive lead 29
therethrough and tabs protruding from the sleeve that may passively
engage or be sutured to tissue of patient 12. In some examples,
such sleeve anchors may be used to seal a tissue access site, such
as incision 174 in carotid sheath 156. Anchor 172 is offset from
the most proximal of electrodes 172 by a distance D. In some
examples, the offset distance D of anchor 172 from the most
proximal of electrodes 172 is in the range from and including
approximately 1 cm to and including approximately 15 cm. In other
examples, the offset distance D may be in the range from and
including approximately 1 cm to and including approximately 2
cm.
[0092] In practice, a variety of techniques may be employed to
extravascularly place lead 29 within carotid sheath 156 adjacent
vagus nerve 150. In the example of FIG. 6, the portion of carotid
sheath 156 and surrounding tissue of patient 12 shown may be
exposed by an incision in the neck of the patient. However, because
lead 29 is not anchored at the distal end that is arranged within
carotid sheath 156, all of or even a portion of vagus nerve 150
need not be dissected from sheath 156. Instead, lead 29 may be
guided through a relatively small incision 174 in carotid sheath
156 to place the distal end of lead 29 including electrodes 170
adjacent vagus nerve 150. Lead 29 may be placed through incision
174 within carotid sheath 156 using a variety of introducer
elements including, e.g., a catheter and/or a guide wire to
stabilize and guide the placement of lead 29 adjacent vagus nerve
150. Lead 29 may be stiffened within carotid sheath 156 by, e.g.,
the guide wire or a stylus. Additionally, the distal end of lead 29
including electrodes 170 may be biased toward vagus nerve 150 using
biasing member 176. Biasing member 176 may be, e.g. an inflatable
or otherwise expandable structure including, e.g. a stent-like
member or a balloon as schematically illustrated in FIG. 6. In
other examples, biasing member 176 may be static, e.g. protruding
tines, or retractable and/or deployable, e.g. one or more elongated
splines or lobes that deflect away from lead 29 when placed under
tension. For example, in addition to biasing member 176, the
example of FIG. 6 includes deployable lobe member 178 including a
plurality of deployable lobes that protrude from and are
circumferentially distributed about lead 29.
[0093] An example of deployable lobe member 178 may be the
Attain.RTM. StarFix.TM. fixation element included in the
over-the-wire lead Model 4195 developed and sold by Medtronic, Inc.
of Minneapolis, Minn. The design of this fixation element allows
clinicians to place and stabilize elongated medical electrical
leads within patients. The StarFix.TM. element generally includes a
number of deployable lobes that are formed lengthwise on an
insulating sheath that surrounds the medical lead by pairs of
elongated, parallel cuts or slits. The deployable lobes are formed
by the material between the elongated, substantially parallel
slits. The spacing between the slits generally defines the width of
the deployable lobe formed therebetween. Accordingly, the rigidity
of each lobe may be increased or decreased by increasing or
decreasing the distance between the parallel slits that define the
lobe. The rigidity of the lobes may also be altered by using
different types of materials and changing the thickness of the
insulating sheath in which the slits are cut to produce the
deployable lobes. The StarFix.TM. lobes are deployed by pushing the
insulating sheath on either side of the parallel slits. The pushing
action causes the sheath to become compressed, thus causing the
extension of the deployable lobes outwardly. As necessary, the
lobes can be relaxed to allow for acute repositioning of the lead
by withdrawing a coupling member so as to reduce compression on the
lobe structure. The StarFix.TM. lead technology provides reliable
fixation of medical leads that can be readily customized to fit a
variety of anatomical dimensions. Examples of deployable lobe
members for biasing and/or stabilizing lead 29 within carotid
sheath 156 include those described in U.S. Patent Publication No.
2004/0176782 A1, to George H. Hanse et al., filed Mar. 3, 2004,
titled "METHOD AND APPARATUS FOR FIXATING AN IMPLANTABLE MEDICAL
DEVICE," the entire content of which is incorporated herein by
reference.
[0094] The placement of lead 29 adjacent vagus nerve 150 may be
stabilized by anchor 172. As explained above, anchor 172 may be any
suitable fixation element that stabilizes the placement of lead 29
and electrodes 170 within sheath 156 adjacent vagus nerve 150. In
one example, anchor 172 includes one or more tines protruding from
lead 29 offset from the most proximate of electrodes 170 by a
distance D. The tines of anchor 172 may be angled with respect to
lead 29 and flexible such that as lead 29 is guided forward through
tissue of patient 12 the tines lay down against an exterior surface
of the lead and do not engage the tissue of the patient. After
placement, lead 29 may be backed slightly out through the tissue of
patient 12 to cause the tines of anchor 172 to pull away from the
lead and catch and pierce the tissue of patient 12, thereby
connecting lead 29 to the tissue.
[0095] In other examples, anchor 172 may include a sleeve anchor
configured to receive lead 29 therethrough and passively engage or
be sutured to tissue of patient 12. FIGS. 8A-8B show two example
sleeve anchors 200 and 202 respectively. Both anchors 200 and 202
have interior bore 204 that is sized to receive lead 29
therethrough. Anchors 200 and 202 also include tabs 206 and 208
respectively protruding away from bore 204. Tabs 206 of anchor 200
are configured to passively engage tissue of patient 12 to
substantially fix the anchor and thereby stabilize the placement of
lead 29. Tabs 208 of anchor 202, on the other hand, includes
suture-receiving apertures 210 that may receive sutures to attach
anchor 202 to tissue of patient 12 and thereby stabilize the
placement of lead 29. Anchor 202 also includes ribs 212, which may
be adapted to inhibit longitudinal movement of anchor 202 and/or
lead 29 with respect to tissue of patient 12 to further stabilize
the placement of lead 29. In some examples, sleeve anchors 200 and
202 may be used to seal a tissue access site, such as incision 174
in carotid sheath 156.
[0096] In addition to the above described examples, anchor 172 may
include deployable lobes that are arranged to deploy on either side
of incision 174 in carotid sheath 156 to stabilize the placement of
lead 29 adjacent vagus nerve 150. FIG. 8C shows deployable lobe
member 178 arranged at incision 174 in carotid sheath 156 to
stabilize placement of lead 29. As with the example arrangement
shown in FIG. 6, deployable lobe member 178 in FIG. 8C includes a
plurality of deployable lobes that protrude from and are
circumferentially distributed about lead 29. In FIG. 8C, however,
lobe member 178 is arranged with respect to incision 174 such that
the incision in carotid sheath 156 lies between two sets of
deployable lobes 178A, 178B of deployable lobe member 178.
Deployable lobe set 178A lies adjacent incision 174 outside of
carotid sheath 156, while set 178B lies inside the sheath. Upon
deployment of lobe sets 178A and 178B on either side of incision
174, deployable lobe member 178 stabilizes the placement of lead 29
and electrodes 170 within sheath 156 adjacent vagus nerve 150. As
with the example of FIG. 6, an example of deployable lobe member
178 arranged as in the example of FIG. 8C may be the Attain.RTM.
StarFix.TM. fixation element developed and sold by Medtronic, Inc.
of Minneapolis, Minn.
[0097] A portion of lead 29 extending from anchor 172 in the
examples of FIGS. 6-8C may be guided to connect with IMD 16. In one
example, lead 29 may be guided intravascularly to an implantation
location of IMD 16 within patient 12. In other examples, lead 29
may be tunneled through tissue of patient 12 to be connected to IMD
16. Although the example of FIGS. 6 and 7 is described with
reference to implanted medical device 16 arranged within patient
12, examples according to this disclosure also include lead 29
connected transcutaneously to an external medical device that is
configured to deliver electrical stimulation to the target nerve
tissue, e.g., vagus nerve 150. After lead 29 is placed adjacent
vagus nerve 150 and connected to IMD 16, IMD 16, either
automatically or as partially or completely commanded by programmer
24, may deliver electrical stimulation therapy to and/or receive
sensor feedback from vagus nerve 150 through electrodes 170.
[0098] Intravascular lead placement proximate target nerve tissue
within a patient generally requires minimally invasive surgical
techniques because the medical leads used to deliver therapy are
guided to the site through a blood vessel, e.g., a vein or artery
that may be readily accessible, e.g., transcutaneously through a
small incision. Intravascular lead placement techniques disclosed
herein further facilitate placing the distal end of the lead in
close proximity of the target nerve tissue, which can be arranged
in different circumferential positions with respect to the blood
vessel in which the lead is located.
[0099] Intravascular techniques described in greater detail below
may include structures and methods for deployment of one or more
medical leads at a first location, testing stimulation at the first
location, and, depending on the efficacy of the stimulation
provided by electrodes on the leads at the first location,
redeploying the leads to a second location. In one example, lead
placement is improved by locating target nerve tissue with a sensor
including, e.g., an IVUS imaging system and/or measuring the
efficacy of test electrical stimulation pulses from an electrode on
the lead through a blood vessel adjacent the target tissue. After a
placement location is determined, one or more leads including one
or more electrodes may be deployed into the vessel and anchored to
a vessel wall near the target nerve tissue.
[0100] FIGS. 9 and 10 illustrate examples of intravascular lead
placement techniques in the context of vagal nerve stimulation in a
human patient. FIG. 9 is a schematic illustration depicting lead 29
intravascularly placed adjacent vagus nerve 150 within internal
jugular vein 158 in patient 12. After or during placement, lead 29
may be connected to IMD 16 or INS 26 similar to lead 28 shown in
FIGS. 1A and 1B respectively. FIG. 10 is a flow chart illustrating
an example method of placing lead 29 in accordance with the example
of FIG. 9. The example method of FIG. 10 includes deploying a
delivery catheter through a lumen of a blood vessel to a target
nerve tissue site (240), identifying a location of the nerve tissue
with respect to the blood vessel with one or more sensors connected
to the delivery catheter (242), advancing an electrical stimulation
electrode from the catheter within the blood vessel lumen toward
the nerve tissue (244), energizing the electrode to deliver
electrical stimulation from within the blood vessel lumen to the
nerve tissue (246), comparing the efficacy of the nerve tissue
stimulation to a threshold efficacy (248), and repositioning the
delivery catheter and the electrode within the blood vessel lumen
if the efficacy of the nerve tissue stimulation does not meet or
exceed the threshold efficacy (250), or chronically deploying the
electrode within the blood vessel lumen adjacent the nerve tissue
if the efficacy of the nerve tissue stimulation meets or exceeds
the threshold efficacy (252). One example of the method illustrated
in FIG. 10 will be described in the context of the example lead
placement structure shown in FIG. 9.
[0101] The arrangement shown in FIG. 9 includes delivery catheter
220, sensor 222, and deployment member 224. Sensor 222 is connected
to catheter 220 toward a distal end thereof. Deployment member 224
is extendable and retractable from catheter 220. Sensor 222 is
arranged between the distal end of catheter 220 and the location
along catheter 220 from which deployment member 224 is extendable
and retractable. Deployment member 224 includes tubular member 226,
lead 29, electrode 228, and guidewire 230. Guidewire 230 includes
anchor portion 230A at a distal end thereof. Electrode 228 is
connected toward a distal end of lead 29. Lead 29 and guidewire 230
are received within and advanceable through a lumen of tubular
member 226. Lead 29 is advanceable along guidewire 230.
[0102] In FIG. 9, catheter 220 is deployed through internal jugular
vein 158 of patient 12 to a target nerve tissue stimulation site.
In other examples, catheter 220 may be deployed in other blood
vessels within patient 12 including, e.g., carotid artery 160, or
the superior or inferior vena cava. Catheter 220 can be any
suitable delivery catheter capable of intravenous delivery within
patient 12 and adapted to accommodate sensor 222 and deployment
member 224. Sensor 222 is connected to the distal end of catheter
220 and is configured to detect the relative position of vagus
nerve 150 outside of jugular vein 158, as well as electrode 228 on
lead 29 within the lumen of vein 158. Sensor 222, in general, may
be any suitable imaging or guidance system including, e.g., a
fiberoptic endoscope, ultrasound imaging system, or any other
on-board imaging system capable of assisting in the positioning of
catheter 220 and electrode 228 within jugular vein 158 relative to
vagus nerve 150 by providing an image of the area adjacent the
location of sensor 222 on catheter 220. In some examples, sensor
222 could be an array of receivers in relationship to a transmitter
that provide an image of surrounding tissue and structures
including vagus nerve 150 and electrode 228. In other examples,
sensor 222 may be configured to send or receive signals to or from
any of a series of known signal generators including sonic,
electromagnetic, light or radiation signals. In still other
examples, sensor 222 may be an optical oxygen content sensor that
may be used to ensure that lead 29 and electrode 228 are not
directed toward, e.g., carotid artery 160 during lead placement. In
some examples, sensor 222 may be employed in conjunction with one
or more opaque markers viewable with fluoroscopic techniques or
with an irrigated lumen that dispenses contrast media to assist in
imaging the relative positions of vagus nerve 150 and electrode 228
on lead 29 within the lumen of jugular vein 158.
[0103] After the clinician identifies the location of vagus nerve
150 with respect to jugular vein 158 based on the output of sensor
222, the clinician may advance deployment member 224 including
electrode 228 toward the wall of the lumen of vein 158 adjacent the
nerve. Deployment member 224, in general, is extendable and
retractable from catheter 220 from, e.g., an aperture formed in a
sidewall thereof. Deployment member 224 includes tubular member
226, lead 29, electrode 228, and guidewire 230. Tubular member 226
may be any structure including at least one lumen through which
various electrode deployment structures including, e.g., lead 29
and guidewire 230 may be advanced to place an electrode within vein
158 adjacent vagus nerve 150. In the example of FIG. 9, tubular
member 226 may be a needle with a lumen in which lead 29 and
guidewire 230 are received and through which the same are
advanceable. Electrode 228 is connected to lead 29, which is
advanceable along guidewire 230.
[0104] With the aid of sensor 222, the clinician advances
deployment member 224 from catheter 220 toward vagus nerve 150.
Lead 29, to which electrode 228 is connected, and guidewire 230 may
be advanced through a lumen of deployment member 224 to position
electrode 228 within vein 158 adjacent vagus nerve 150. Guidewire
230 includes anchor portion 230A at a distal end thereof that is
configured to temporarily anchor deployment member 224, lead 29 and
electrode 228, and guidewire 230 to the wall of the lumen of vein
158. In the example of FIG. 9, anchor portion 230A of guidewire 230
is formed in a spiral that is configured to be twisted into the
lumen wall. Anchor portion 230A can be freed from the vessel wall
by either untwisting guidewire 230, or in the case that guidewire
230 is sufficiently flexible, pulling the wire away from the
spiraling anchor portion 230A to effectively unwind and release the
anchor from the wall of jugular vein 158. In addition to anchor
portion 230A of guidewire 230, lead 29 includes barbs 231 that are
configured to engage tissue of jugular vein 158 to anchor lead 29
and electrode 228 to the wall of the vein after guidewire 230 has
been retracted. In other examples, lead 29 may be anchored to the
wall of vein 158 with different structures including, e.g., a
helical coil or other spiral coil shapes, C-shaped members,
harpoon-like structures, hooks, expandable or serrated members, and
the like. In FIG. 9, deployment member 224 and electrode 228 on
lead 29 are advanced such that at least lead 29 lies in the sensory
field of sensor 222.
[0105] In one example, sensor 222 is an intravenous ultrasound
("IVUS") imaging system that is adapted to radiate ultrasonic waves
out from sensor 222 to generate a two dimensional image of the
tissue and structures surrounding catheter 220 and sensor 222. FIG.
11 is a schematic illustration of an example two dimensional
ultrasonic image generated by a device coupled to sensor 222 as
arranged with catheter 220, lead 29 and electrode 228 of FIG. 9
located within the jugular vein 158. When activated, sensor 222
produces an imaging field 260 from ultrasonic waves produced by and
radiating radially from sensor 222. The size of imaging field 260
may vary depending on the particular configuration and capabilities
of sensor 222. The tissues and other structures caught within
imaging field 260 of sensor 222 may be distinguished from one
another and the relative positioning of the different structures
may be discerned. In the example of FIG. 11, vagus nerve 150,
jugular vein 158, and carotid artery 160 are located within imaging
field 260, while carotid sheath 156 shown in shadow lines is not
within the sensing range of sensor 222. By distinguishing different
structures and displaying relative positions, sensor 222 may be
used to facilitate positioning catheter 220 and electrode 228 on
lead 29 within jugular vein 158 in a desired location relative to
vagus nerve 150 by, e.g., rotating the catheter and electrode
within the blood vessel in the directions indicated by arrow 262 in
FIG. 11.
[0106] Having deployed catheter 220, detected the location of vagus
nerve 150 relative to jugular vein 158, and advanced electrode 228
toward vagus nerve 150, electrical stimulation may be delivered to
vagus nerve 150 through the wall of the lumen of vein 158 via
electrode 228. During test stimulation of vagus nerve 150, a
portion of lead 29 extending away from a distal end toward which
electrode 228 is arranged may be connected, e.g., transcutaneously
to an external neurostimulation device that is configured to
deliver electrical stimulation to the target nerve tissue, e.g.,
vagus nerve 150 while lead 29 and electrode 228 are being
positioned relative thereto within vein 158. After lead 29 is
connected to the neurostimulator, the device, either automatically
or as partially or completely commanded by a programmer, such as
programmer 24, may deliver electrical stimulation therapy to and/or
receive sensor feedback from vagus nerve 150 through electrode
228.
[0107] In the example of FIGS. 9 and 10, as well as other examples
disclosed herein, the efficacy of the electrical stimulation
delivered by electrode 228 to vagus nerve 150 may be compared to a
threshold efficacy to determine whether or not electrode 228 is
satisfactorily positioned with respect to nerve 150. Efficacy
refers, in general, to a combination of complete or partial
alleviation of symptoms alone, or in combination with a degree of
undesirable side effects. Efficacy may be measured, in general, by
verbal feedback from patient 12, clinician observation of various
conditions of patient 12, or sensory feedback from one or more
devices including, e.g., ICD 17 shown in FIG. 1A or cardiac therapy
module 104 shown in FIG. 4. Various physiological signals may be
observed to measure the efficacy of the test stimulation, and
thereby the need to reposition lead 29 relative vagus nerve 150.
For example, to determine the response to stimulation of vagus
nerve 150, ECG, heart rate, blood pressure, blood flow, cardiac
output, and/or breathing, of patient 12 can be sensed or observed.
These and other physiological signals may be detected in a variety
of ways including sensing the signals using sense electrodes,
pressure sensors, ultrasound sensors, motion sensors or other
devices. In other examples, physiological reactions of patient 12
may be observed or measured by, e.g., a clinician. In one example,
efficacy may be measured by a sensor including, e.g., an
accelerometer that determines if stimulation of the neck muscles or
phrenic nerve of patient 12 is occurring with or instead of
stimulation of vagus nerve 150. In another example, a pressure
sensor arranged coincident with or connected to lead 29 may measure
blood pressure by detecting the pressure within jugular vein 158. A
pressure sensor, or other type of physiological feedback sensor,
may also, in some examples, be connected to catheter 220 to
measure, e.g., blood pressure within vein 158.
[0108] In the event the nerve tissue stimulation meets or exceeds
the threshold efficacy, lead 29 and electrode 228 may be
chronically deployed within jugular vein 158 adjacent vagus nerve
150. On the other hand, if the nerve stimulation delivered by
electrode 228 does not provide the threshold level of efficacy in
relieving the symptoms of patient 12, catheter 220 and electrode
228 may be repositioned within jugular vein 158 to improve the
location of the components, in particular electrode 228 with
respect to vagus nerve 150. Generally speaking, catheter 220 and
electrode 228 may be repositioned by rotating catheter 220 within
jugular vein 158 in the manner described with reference to FIG. 11
and with the assistance of, e.g., ultrasound imaging provided by
sensor 222. In some examples, guidewire 230 including anchor
portion 230A may be retracted along with lead 29 and electrode 228
into deployment member 224 before repositioning catheter 220 and
then redeployed after the catheter has be relocated. After
repositioning catheter 220 and electrode 228, the process of
stimulating vagus nerve 150 and comparing the efficacy of the nerve
stimulation to a threshold efficacy may be repeated until the
arrangement of electrode 228 with respect to vagus nerve 150
delivers electrical stimulation therapy that meets or exceeds the
threshold efficacy level.
[0109] After determining a placement location that delivers
satisfactory treatment efficacy, lead 29 and electrode 228 may be
chronically deployed within jugular vein 158 adjacent vagus nerve
150. After chronic deployment of lead 29 and electrode 228, a
portion of lead 29 extending away from a distal end toward which
electrode 228 is arranged may be guided to connect with, e.g., IMD
16. In one example, lead 29 may be guided intravascularly to an
implantation location of IMD 16 within patient 12. In other
examples, lead 29 may be tunneled through tissue of patient 12 to
be connected to IMD 16. After lead 29 is placed adjacent vagus
nerve 150 and connected to IMD 16, IMD 16, either automatically or
as partially or completely commanded by programmer 24, may deliver
electrical stimulation therapy to and/or receive sensor feedback
from vagus nerve 150 through electrode 228.
[0110] FIGS. 12A and 12B show alternative examples of deployment
member 224 for use in methods and systems according to this
disclosure. In general, FIGS. 12A and 12B show different
arrangements and combinations of anchoring members and electrodes
with respect to tubular member 226, lead 29, and guidewire 230 of
deployment member 224. In the interest of simplicity, catheter 220
has been omitted from the illustrations of FIGS. 12A and 12B. In
FIG. 12A, deployment member 224 is arranged within jugular vein 158
adjacent vagus nerve 150 and includes tubular member 226, lead 29,
electrode 228, guidewire 230, and expandable member 270. In some
examples, expandable member 270 may provide additional
stabilization or biasing of lead 29 or other components of
deployment member 224 within jugular vein 158. For example,
expandable member 270 may push against catheter 220 (not shown in
FIG. 12A) to bias lead 29 and electrode 228 toward the wall of the
lumen of vein 158. In another example, expandable member 270 may
further stabilize the placement of lead 29 and electrode 228 by
expanding to apply force on the lumen wall and catheter 220. The
expandable member 270 may, in some examples, be a balloon catheter
including, e.g., an angioplasty catheter. In other examples,
expandable member 270 may be a stent or deployable spline or
lobe.
[0111] FIG. 12B shows deployment member 224 with additional
electrode 272 connected to tubular member 226. In FIG. 12B,
deployment member 224 is arranged within jugular vein 158 adjacent
vagus nerve 150 and includes tubular member 226, lead 29, electrode
228, guidewire 230, and electrode 272. Although intravascular
placement examples of lead 29 have been described herein with
reference to a single electrode 228 for simplicity, in practice,
lead 29 will commonly include a plurality of electrodes that may be
employed in different anode and cathode combinations to stimulate
vagus nerve 150 as, e.g., described with reference to electrodes
80-83 in FIG. 2. Additionally and as illustrated in FIG. 12B,
deployment member 224 may include electrodes in addition to lead
electrode 228 arranged in different locations and/or connected to
different components. Electrode 272 is connected to tubular member
226 in the example of FIG. 12B. In some examples, tubular member
226 and electrode 272 may be advanced toward vagus nerve 150 prior
to chronically deploying lead 29 and electrode 228. In such
examples, electrode 272 may be used to deliver test stimulation
pulses to vagus nerve 150 to determine the efficacy of the
placement of deployment member 224 within jugular vein 158 with
respect to vagus nerve 150. After determining a position of
deployment member that provides a threshold efficacy in stimulating
vagus nerve 150, lead 29 and guidewire 230 may be advanced through
tubular member 226 and lead 29 and electrode 228 may be chronically
deployed along the wall of the lumen of jugular vein 158 adjacent
vagus nerve 150.
[0112] In addition to placing lead 29 and electrode 228
intravascularly using deployment member 224 as shown in the
examples of FIGS. 9, 11, 12A and 12B, lead 29 and electrode 228 may
be advanced from a distal tip of catheter 220 to be actively fixed
to the wall of jugular vein 158 as shown in FIG. 13. The
arrangement shown in FIG. 13 includes delivery catheter 220, sensor
222, lead 29, electrodes 228 and 229, and active fixation member
274. Sensor 222 and electrode 229 are connected to catheter 220
toward a distal end thereof. Electrode 228 is connected toward a
distal end of lead 29. Lead 29 and electrode 228 are received
within and advanceable through a lumen of catheter 220 and out of
the tip of the catheter to place electrode 228 within vein 158
adjacent vagus nerve 150. Although not shown in FIG. 13, lead 29
may be advanced along and guided by a guide member including, e.g.,
a guidewire or a stylus.
[0113] In FIG. 13, catheter 220 is deployed through internal
jugular vein 158 of patient 12 to a target nerve tissue stimulation
site. In other examples, catheter 220 may be deployed in other
blood vessels within patient 12 including, e.g., carotid artery
160, or the superior or inferior vena cava. Catheter 220 can be any
suitable delivery catheter capable of intravenous delivery within
patient 12 and adapted to accommodate sensor 222, electrode 229,
and lead 29. In some examples, catheter 220 may be flexible or
curved to direct the tip of the catheter laterally toward the wall
of jugular vein 158. Sensor 222 is connected to the distal end of
catheter 220 and is configured to detect the relative position of
vagus nerve 150 outside of jugular vein 158. Sensor 222, in
general, may be any suitable imaging or guidance system including,
e.g., a fiberoptic endoscope, ultrasound imaging system, or any
other on-board guidance or imaging system capable of assisting in
the positioning of catheter 220 within jugular vein 158 relative to
vagus nerve 150 by providing an image of the area adjacent the
location of sensor 222 on catheter 220.
[0114] Electrode 229 is also connected to a distal end of catheter
220 and may be advanced toward the wall of the lumen of jugular
vein 158 to deliver test stimulation pulses to vagus nerve 150
through the wall of vein 158. Electrode 229 may therefore be
employed in addition to or in lieu of sensor 222 to detect the
relative position of vagus nerve 150 outside of jugular vein 158.
During test stimulation of vagus nerve 150, electrode 229 may be
connected to a conductor connected, e.g., transcutaneously to an
external neurostimulation device that is configured to deliver
electrical stimulation to the target nerve tissue, e.g., vagus
nerve 150. After electrode 229 is connected to the neurostimulator,
the device, either automatically or as partially or completely
commanded by a programmer, such as programmer 24, may deliver
electrical stimulation therapy to and/or receive sensor feedback
from vagus nerve 150.
[0115] In the example of FIG. 13, as well as other examples
disclosed herein, the efficacy of the electrical stimulation
delivered by electrode 229 to vagus nerve 150 may be compared to a
threshold efficacy to determine whether or not electrode 229, and
thereby catheter 220 is satisfactorily positioned with respect to
nerve 150. Efficacy may be measured, in general, by verbal feedback
from patient 12, clinician observation of various conditions of
patient 12, or sensory feedback from one or more devices including,
e.g., ICD 17 shown in FIG. 1A or cardiac therapy module 104 shown
in FIG. 4. Various physiological signals may be observed to measure
the efficacy of the test stimulation, and thereby the need to
reposition catheter 220 and electrode 229 relative vagus nerve 150.
For example, to determine the response to stimulation of vagus
nerve 150, ECG, heart rate, blood pressure, blood flow, cardiac
output, and/or breathing, of patient 12 can be sensed or observed.
These and other physiological signals may be detected in a variety
of ways including sensing the signals using sense electrodes,
pressure sensors, ultrasound sensors, motion sensors or other
devices. In other examples, physiological reactions of patient 12
may be observed or measured by, e.g., a clinician. In one example,
efficacy may be measured by a sensor including, e.g., an
accelerometer that determines if stimulation of the neck muscles or
phrenic nerve of patient 12 is occurring with or instead of
stimulation of vagus nerve 150. In another example, a pressure
sensor arranged coincident with or connected to catheter 220 may
measure blood pressure by detecting the pressure within jugular
vein 158.
[0116] In the event the nerve tissue stimulation meets or exceeds
the threshold efficacy, lead 29 and electrode 228 may be
chronically deployed by advancing the lead from the tip of catheter
220 within jugular vein 158 toward vagus nerve 150. On the other
hand, if the nerve stimulation delivered by electrode 229 does not
provide the threshold level of efficacy in relieving the symptoms
of patient 12, catheter 220 and electrode 229 may be repositioned
within jugular vein 158 to improve location with respect to vagus
nerve 150. Generally speaking, catheter 220 and electrode 229 may
be repositioned by rotating catheter 220 within jugular vein 158 to
different incremental positions until an acceptable position for
catheter 220 relative to vagus nerve 150 is determined. After
repositioning catheter 220 and electrode 229, the process of
stimulating vagus nerve 150 and comparing the efficacy of the nerve
stimulation to a threshold efficacy may be repeated until the
arrangement of catheter 220 with respect to vagus nerve 150
delivers electrical stimulation therapy that meets or exceeds the
threshold efficacy level.
[0117] Once catheter 220 is positioned within jugular vein 158 such
that electrode 229 delivers stimulation that meets or exceeds the
threshold efficacy, lead 29 and electrode 228 may be advanced
through a lumen of catheter 220 and out of the tip of the catheter
to actively fix lead 29 and electrode 228 to the wall of vein 158
adjacent vagus nerve 150. In FIG. 13, catheter 220 is curved to
direct the tip of the catheter laterally toward the wall of jugular
vein 158. Connected to a distal end of lead 29 is active fixation
member 274, which, in the example of FIG. 13 is a helical coil that
is configured to be twisted into the wall of jugular vein 158.
[0118] In practice, lead 29, electrode 228, and fixation member 274
may be advanced laterally from the tip of catheter 220 toward the
wall of jugular vein 158 adjacent vagus nerve 150. In some
examples, lead 29 may be directed toward the wall of vein 158 along
a trajectory that is approximately perpendicular to the wall.
Active fixation member 274 engages the wall of the lumen of jugular
vein 158 by, e.g., twisting lead 29 to screw the helical fixation
member into the wall. After actively fixing lead 29 and electrode
228 to the wall of vein 158 adjacent vagus nerve 150, catheter 220
may be removed, after which lead 29 and electrode 228 will lay down
along and approximately tangential to the wall of vein 158.
[0119] In some examples, active fixation member 274 may be
electrically active such that it acts as an electrode in addition
to or in lieu of electrode 228. Fixation member 274 may have a
variety of lengths and helical pitches. In some examples, fixation
member 274 may have a length in the range from and including
approximately 0.5 millimeters to and including approximately 2.5
millimeters. In other examples, fixation member 274 may have a
length in the range from and including approximately 1 millimeters
to and including approximately 2 millimeters. The pitch of the
helical coil of active fixation member 274 may also vary in
different examples according to this disclosure. In general, in
examples in which fixation member 274 is electrically active, it
may be desirable to increase the pitch to increase the amount of
surface area engaging tissue of the wall of jugular vein 158. In
some examples, fixation member 274 may have a helical pitch in the
range from and including approximately 0.5842 millimeters to and
including approximately 1.016 millimeters.
[0120] FIGS. 14A-14J are elevation front views of various anchors
that may be used alone or in combination to anchor or bias a
medical lead and/or electrode within a vessel in accordance with
examples disclosed herein. The anchors illustrated in FIGS. 14A-14J
may be employed, for example, in a manner as described with
reference to anchor portion 230A of guidewire 230 and/or barbs 231
in FIG. 9. In such examples, anchor portion 230A of guidewire 230
and/or barbs 231 may take an alternative form to that shown in FIG.
9 including, e.g., the harpoon shapes of FIGS. 14B and 14C. In
another example, a portion of lead 29 may be shaped as shown in
FIGS. 14A, 14D, or 14F and wedged into jugular vein 158 to anchor
the lead and electrode 228 within the vein adjacent vagus nerve
150.
[0121] In addition to the intravascular techniques described with
reference to FIGS. 9-14, examples according to this disclosure also
include techniques employing an expandable and contractible
generally cylindrical lead member that is temporarily deployable
for testing multiple electrode orientations and combinations before
deploying the member for chronic stimulation of target nerve tissue
within a patient.
[0122] FIGS. 15 and 16 illustrate examples of intravascular lead
placement techniques including a generally cylindrical expandable
and contractible lead member in the context of vagal nerve
stimulation in a human patient. FIG. 15 is a schematic illustration
depicting lead 29 attached to cylindrical lead member 300, both of
which are intravascularly placed adjacent vagus nerve 150 within
internal jugular vein 158 in patient 12. After or during placement,
lead 29 and lead member 300 may be connected to IMD 16 or INS 26
similar to lead 28 shown in FIGS. 1A and 1B respectively. FIG. 16
is a flow chart illustrating an example method of placing lead 29
and cylindrical lead member 300 in accordance with the example of
FIG. 15. The example method of FIG. 16 includes arranging a
generally cylindrical expandable and contractible lead member
within a lumen of a blood vessel adjacent target nerve tissue
(310), temporarily deploying the cylindrical lead member within the
lumen relative to the nerve tissue (312), energizing one or more
electrodes connected to the cylindrical lead member to deliver
electrical stimulation from within the blood vessel lumen to the
nerve tissue (314), comparing the efficacy of the nerve tissue
stimulation to a threshold efficacy (316), and redeploying the
cylindrical lead member within the lumen relative to the nerve
tissue if the efficacy of the nerve tissue stimulation does not
meet or exceed the threshold efficacy (318), or chronically
deploying the cylindrical lead member in an expanded state within
the lumen if the efficacy of the nerve tissue stimulation meets or
exceeds the threshold efficacy (320). One example of the method
illustrated in FIG. 16 will be described in the context of the
example lead structure shown in FIG. 15.
[0123] The arrangement shown in FIG. 15 includes lead member 28,
cylindrical lead member 300, and electrodes 302. As will be
described in greater detail below, some examples may include
additional components for arranging and deploying cylindrical lead
member 300 within a blood vessel including, e.g., a delivery
catheter and/or a stylus or other active deployment mechanism.
Cylindrical lead member 300 is connected to a distal end of lead
member 28. Electrodes 302 are connected to an exterior surface of
lead member 300 and are arranged in columns 304 parallel to a
longitudinal axis of lead member 300. Depending on how electrodes
302 are grouped, they may also be seen in FIG. 15 as arranged in
columns 306 that wrap around the exterior surface of lead member
300 oriented at an angle with respect to the longitudinal axis of
the cylindrical lead member. In other examples according to this
disclosure, lead member 300 may include fewer or more electrodes
302 than shown in the example of FIG. 15. For example, lead member
302 may include more than two columns 306 of electrodes 302
distributed circumferentially around the exterior surface of
cylindrical lead member 300. Cylindrical lead member 300 is an
expandable and retractable component that may be deployed and
redeployed passively or actively within a blood vessel. Lead member
300 is shown schematically in FIG. 15 in a contracted state in
dashed lines and in an expanded state in solid lines. As described
in greater detail below, cylindrical lead member 300 may be any one
of a number of different structures that are capable of active
and/or passive deployment and redeployment including, e.g.,
circular cylindrical members, wire mesh stents, and spiral wire and
ribbon members.
[0124] In FIG. 15, lead 29 and cylindrical lead member 300 are
arranged within the lumen of internal jugular vein 158 adjacent
vagus nerve 150. In other examples, lead member 300 may be deployed
in other blood vessels within patient 12 including, e.g., carotid
artery 160 adjacent vagus nerve 150 or another vein or artery
adjacent the target nerve tissue at which stimulation therapy is
directed. Cylindrical lead member 300 may be guided to the target
nerve tissue site within patient 12 by, e.g., a small
transcutaneous incision to gain access to jugular vein 158 and then
directed through the vein by, e.g., a delivery catheter to the
target site adjacent vagus nerve 150.
[0125] After arranging cylindrical lead member 300 within the lumen
of jugular vein 158 adjacent vagus nerve 150, lead member 300 may
be temporarily deployed within the lumen relative to vagus nerve
150. Vagus nerve 150 is positioned within patient 12 outside of
jugular vein 158, which has a generally tubular shape. Upon
intravascular implantation of lead member 300 within jugular vein
158, the relative orientation of vagus nerve 150 around the
periphery of jugular vein 158 may not be known without, e.g.,
complete dissection of carotid sheath 156. Deployment of lead
member 300 within jugular vein 158 and stimulation of vagus nerve
150 by selected ones of electrodes 302 may initially be somewhat
arbitrary with respect to the actual position of vagus nerve 150
without testing or feedback regarding the orientation and
combination of electrodes 302 used. Therefore, cylindrical lead
member 300 is capable of deployment and redeployment within jugular
vein 158 adjacent vagus nerve 150 to test multiple orientations and
combinations of electrodes 302 before deploying the lead member for
chronic treatment of patient 12.
[0126] As indicated in FIG. 15 by arrow 308, lead member 300 is
capable of being rotated within jugular vein 158 to vary the
orientation of lead member 300, and thereby electrodes 302 within
the vein. Lead member 300 may be oriented within jugular vein 158
both by rotating the lead member and also may be, in some examples,
temporarily expanded to abut the walls of the lumen of vein 158 as
shown in FIG. 15. In addition to orienting and expanding lead
member 300, electrodes 302 may be selectively activated in
different combinations in a manner similar to that described with
reference to FIG. 2. For example, lead 29 and cylindrical lead
member 300 may be connected to IMD 16 shown in FIGS. 1A and 2.
Neurostimulation therapy module 106 of IMD 16 may include a
switching module to selectively couple pairs of electrodes 302 to
signal generator 112 and/or sensing module 114 to form different
anode-cathode combinations. The switching module may include, e.g.,
a switch array, switch matrix, multiplexer, or any other type of
switching device suitable to selectively couple stimulation energy
to selected electrodes. In one example, the switching module may
select combinations of electrodes 302 grouped along longitudinal
column 304 in FIG. 15. In another example, however, the switching
module may select combinations of electrodes 302 grouped along the
skewed columns 306. In this manner, deploying lead member 300
within the lumen of jugular vein 158 may include both orienting and
expanding lead member 300 and electrodes 302 within the vein, and
selecting combinations of electrodes 302 to stimulate (and/or sense
nerve signals from) vagus nerve 150. During the placement of lead
member 300, lead 29 may be transcutaneously connected to IMD 16 to
test the placement of lead member 300 prior to implanting the
device within patient 12. In another example, lead 29 may be
connected to an external neurostimulation device that is configured
to deliver electrical stimulation to vagus nerve 150 while lead
member 300 is being positioned relative thereto within vein
158.
[0127] After cylindrical lead member 300 and electrodes 302 have
been temporarily deployed within jugular vein 158, one or more of
the electrodes may be energized to deliver electrical stimulation
to vagus nerve 150. During test stimulation of vagus nerve 150, a
portion of lead 29 extending away from a distal end to which lead
member 300 and electrodes 302 may be connected, e.g.,
transcutaneously to an external neurostimulation device that is
configured to deliver electrical stimulation to the target nerve
tissue, e.g., vagus nerve 150 while lead member 300 and electrodes
302 are being positioned relative thereto within vein 158. After
cylindrical lead member 300 is placed adjacent vagus nerve 150 and
connected to the external neurostimulator, the device, either
automatically or as partially or completely commanded by a
programmer, such as programmer 24, may deliver electrical
stimulation therapy to and/or receive sensor feedback from vagus
nerve 150 through one or more of electrodes 302.
[0128] In the example of FIGS. 14 and 15, as well as other examples
disclosed herein, the efficacy of the electrical stimulation
delivered by electrodes 302 to vagus nerve 150 may be compared to a
threshold efficacy to determine whether or not cylindrical lead
member 300 and electrodes 302 are satisfactorily positioned with
respect to nerve 150 and/or an optimal combination of electrodes
302 has been selected to deliver stimulation to the nerve. As
described above with reference to FIGS. 9 and 10, efficacy may be
measured, in general, by verbal feedback from patient 12, clinician
observation of various conditions of patient 12, or sensory
feedback from one or more sensors. Various physiological signals
may be observed to measure the efficacy of the test stimulation,
and thereby the need to reposition lead member 300 relative vagus
nerve 150. For example, to determine the response to stimulation of
vagus nerve 150, ECG, heart rate, blood pressure, blood flow,
cardiac output, and/or breathing, of patient 12 can be sensed or
observed.
[0129] In the event the nerve tissue stimulation meets or exceeds
the threshold efficacy, cylindrical lead member 300, to which
electrodes 302 are attached, may be chronically deployed in an
expanded state within jugular vein 158 adjacent vagus nerve 150.
The orientation of cylindrical lead member 300 and selected
combination of electrodes 302 that delivered therapy to patient 12
meeting or exceeding the threshold efficacy may be used to deliver
chronic, i.e. long term therapy to the patient. On the other hand,
if the nerve stimulation delivered by cylindrical lead member 300
and electrodes 302 does not provide the threshold level of efficacy
in treating patient 12, lead member 300 may be redeployed within
jugular vein 158 relative to vagus nerve 150. As with the initial
temporary deployment, redeploying lead member 300 may include
orienting the lead member by rotating within jugular vein 158, as
well as selecting one or more combinations of electrodes 302 to
stimulate vagus nerve 150. In some examples of redeployment, lead
member 300 may also be contracted and then re-expanded to abut the
walls of the lumen of jugular vein 158 as shown in FIG. 15. For
example, in the event lead member 300 was previous expanded within
jugular vein 158, the lead member may need to be contracted in
order to be reoriented by rotating it within the vein. After
redeploying cylindrical lead member 300, the process of stimulating
vagus nerve 150 and comparing the efficacy of the nerve stimulation
to a threshold efficacy may be repeated until the arrangement of
lead member 300 with respect to vagus nerve 150 delivers electrical
stimulation therapy that meets or exceeds the threshold efficacy
level.
[0130] After determining a placement location that delivers
satisfactory treatment efficacy, cylindrical lead member 300, to
which electrodes 302 are attached, may be chronically deployed in
an expanded state within jugular vein 158 adjacent vagus nerve 150.
After chronic deployment of lead member 300, a portion of lead 29
extending away from a distal end toward which lead member 300 is
arranged may be guided to connect with, e.g., IMD 16. In one
example, lead 29 may be guided intravascularly to an implantation
location of IMD 16 within patient 12. In other examples, lead 29
may be tunneled through tissue of patient 12 to be connected to IMD
16. After lead 29 is placed adjacent vagus nerve 150 and connected
to IMD 16, IMD 16, either automatically or as partially or
completely commanded by programmer 24, may deliver electrical
stimulation therapy to and/or receive sensor feedback from vagus
nerve 150 through electrodes 302.
[0131] FIGS. 17A and 17B, and 18A-18D show several examples of
cylindrical lead member 300 and delivery mechanisms appropriate for
use in the example of FIGS. 15 and 15. FIGS. 17A and 17B are
schematic illustrations of a cylindrical lead member arranged
within a delivery catheter for deploying and redeploying the lead
member within jugular vein 158 relative to vagus nerve 150. FIGS.
18A-18D are schematic illustrations of different examples of a
cylindrical lead member that is expandable and contractible for
deployment and redeployment within vein 158.
[0132] Generally speaking, there are several methods by which
cylindrical lead member 300 may be temporarily and then chronically
deployed within a blood vessel to test various orientations and
combinations of electrodes 302 relative to vagus nerve 150. In some
examples, cylindrical lead member 300 may be arranged adjacent
vagus nerve 150 within a delivery mechanism that allows for the
flexible orientation and selection of combinations of electrodes
302 within jugular vein 150 relative to the position of vagus nerve
150. For example, lead member 300 may be arranged within a delivery
catheter that accommodates relative movement of the lead member and
the catheter to expose different combinations of electrodes 302
oriented in different positions within vein 158 relative to vagus
nerve 150. In other examples, cylindrical lead member 300 may be
actively expandable and contractible such that the lead member may
be expanded within jugular vein 158 and thereafter contracted and
re-expanded in a different orientation relative to vagus nerve
150.
[0133] FIGS. 17A and 17B are schematic illustrations of a
cylindrical lead member arranged within a delivery catheter that
accommodates relative movement of the lead member and the catheter
to expose different combinations of electrodes 302 oriented in
different positions within vein 158 relative to vagus nerve 150. In
FIG. 17A, lead 29 and cylindrical lead member 300 connected thereto
are arranged within delivery catheter 330. Electrodes 302 are
connected to lead member 300 and arranged in columns 304 that are
generally parallel to a longitudinal axis of the lead member.
Catheter 330 includes a plurality of apertures 332 that are shaped
and sized to expose groups of electrodes 302. In the example of
FIG. 17A, apertures 332 are generally rectangular slots in catheter
330. However, in other example, apertures 332 may be, e.g., holes
arranged to expose one or more of electrodes 302.
[0134] In practice, delivery catheter 330 and lead member 300 may
be guided intravascularly to a target tissue site through jugular
vein 158 adjacent vagus nerve 150. Cylindrical lead member 300 may
be oriented within catheter 330 such that select groups of
electrodes 302 are exposed by apertures 332. In the example of FIG.
17A, electrodes 302 will be generally exposed in groups arranged
along longitudinal columns 304. However, in other examples,
apertures 332 may be shaped and oriented to expose one or more
electrodes 302 in different groups including, e.g., groups arranged
along columns oriented at an angle with respect to a longitudinal
axis of lead member 300, such as columns 306 shown in FIG. 15. In
any event, after lead member 300 and electrodes 302 are oriented
within catheter 330, different combinations of electrodes 302 may
deliver electrical stimulation to vagus nerve 150. Cylindrical lead
member 300 and/or catheter 330 may be reoriented within jugular
vein 158 one or more times to test different orientations and
combinations of electrodes 302 until a threshold efficacy is
indicated. Thereafter, cylindrical lead member 300 and electrodes
302 may be chronically deployed in an expanded state by, e.g.,
withdrawing delivery catheter 330 to allow lead member 300 to
passively expand to abut the walls of the lumen of jugular vein
158.
[0135] In FIG. 17B, cylindrical lead member 340 is arranged within
delivery catheter 342. Electrodes 344 are connected to lead member
340. Electrodes 344 are ring electrodes arranged around the
exterior surface of and distributed longitudinally along lead
member 340. Catheter 342 includes helical aperture 346 that is
shaped and sized to expose portions of each of electrodes 340 at
different rotational orientations within a blood vessel. In the
example of FIG. 17A, apertures 346 is a generally rectangular slot
in catheter 342. However, in other examples, catheter 342 may
include a series of holes arranged in a helical line to expose
different portions of electrodes 344 oriented at different
rotational positions.
[0136] Similar to the example of FIG. 17A, delivery catheter 342
and lead member 340 may be guided intravascularly to a target
tissue site through jugular vein 158 adjacent vagus nerve 150.
Cylindrical lead member 340 may be oriented within catheter 342
such that select portions of electrodes 344 are exposed at
different rotational orientations with respect to vagus nerve 150.
After lead member 340 and electrodes 344 are oriented within
catheter 346, different combinations of electrodes 344 may deliver
electrical stimulation to vagus nerve 150. Catheter 346 may then be
rotated relative to lead member 340 within jugular vein 158 one or
more times to test different orientations and combinations of
electrodes 344 until a threshold efficacy is indicated.
[0137] The catheters shown in FIGS. 17A and 17B may, in some
examples, act as permanent components deployed along with
cylindrical lead members, instead of temporary delivery components
that are used to arrange and deploy the lead members and are
thereafter removed. For example, the catheters and the cylindrical
lead members may be arranged within a blood vessel such that the
catheter abuts and thereby is fixed within the lumen of the blood
vessel. In such examples, the cylindrical lead member may be
rotated within the catheter to vary electrode orientation and
combinations. The lead member may remain in an expanded state
abutting a lumen of the catheter from initial implantation until
chronic deployment, or, in other examples, may contract to be
reoriented and expand to test the new electrode orientation and/or
combination. In any event, the catheters may remain deployed along
with the cylindrical lead members within the blood vessel for
chronic treatment of a patient.
[0138] FIGS. 18A-18D are schematic illustrations of different
examples of a cylindrical lead member that is expandable and
contractible for deployment and redeployment within jugular vein
158 of patient 12. FIGS. 18A and 18B show mesh stent lead member
350 with different electrode configurations, while FIGS. 18C and
18D show two different helical lead members 352 and 354
respectively. In FIGS. 18A and 18B, mesh stent lead member 350
includes a plurality of material segments 356 each of which is
pivotally joined at either end to another segment at a vertex.
Material segments 356 may be constructed from various biocompatible
materials that resists corrosion and degradation from bodily fluids
including, e.g., titanium or biologically inert polymers. Generally
speaking, mesh stent lead member 350 is expandable and contractible
by rotation of material segments 356 with respect to each other at
the plurality of vertices at which the segments are pivotally
joined. As mesh stent lead member 350 contracts, material segments
356 rotate such that the angle of each segment with respect to a
longitudinal axis of lead member 350 decreases, which in turn
decreases the diameter and increases the overall length of the lead
member. Conversely, as mesh stent lead member 350 expands, material
segments 356 rotate such that the angle of each segment with
respect to the longitudinal axis of lead member 350 increases,
which in turn increases the diameter and decreases the overall
length of the lead member. Other examples according to this
disclosure may include stent lead members having different
configurations than lead member 350 of FIGS. 18A and 18B. For
example, in one example, a mesh stent member may include fewer or
more material segments pivotally joined at fewer or more vertices
to form coarser or finer meshes than mesh stent lead member 350. In
another example, a stent lead member may be constructed from a
polymer that is expandable to take the shape of the blood vessel in
which it is arranged. In still another example, a mesh stent member
may include a resorbable material interconnecting some or all of
the mesh that would, over a period of time leave only the mesh of
material segments and electrodes within the blood vessel of the
patient.
[0139] FIGS. 18A and 18B illustrate stent lead member 350 with
different electrode configurations. In FIG. 18A, electrodes 302 are
connected to lead member 350 substantially coincident with the
vertices at which material segments 356 are joined. In other
examples, only some of the junctions between material segments 356
may include electrodes 302 arranged thereon or about. Electrodes
302, as illustrated in FIG. 18A, may protrude from the exterior
surface of lead member 350, or any other cylindrical lead member
according to this disclosure. In this manner, electrodes 302 may
penetrate the wall of the blood vessel lumen in which lead member
350 is arranged, e.g. jugular vein 158, to assist in fixing the
lead member within the vessel. In FIG. 18B, on the other hand, lead
29 is wrapped partially or completely around stent lead member 350
and includes ring electrodes 358 attached thereto. Wrapping lead 29
around lead member 350 along a helical trajectory as shown in FIG.
18B may provide a mechanical advantage for expansion of the lead
member, because, in such an orientation, lead 29 may not need to
stretch as the overall length of lead member 350 increases.
[0140] FIGS. 18C and 18D show two different helical lead members
352 and 354 respectively. Lead member 352 is a helical wire, while
lead member 354 is a helical ribbon. Both wire and ribbon helical
lead members 352 and 354 include electrodes 302 electrically
connected to lead 29 and arranged generally in one or more lines
parallel to the helical trajectory of each lead member. Generally
speaking, helical lead members 352 and 354 are expandable and
contractible by bringing their respective ends 352A, 352B and 354A,
354B closer together or further apart. In the case of helical wire
lead member 352, as ends 352A and 352B are brought closer together,
individual windings of the helical wire are also brought closer
together and the diameter of the helix of lead member 352 expands.
Conversely, as ends 352A and 352B are brought further apart,
individual windings of the helical wire are also brought further
apart and the diameter of the helix of lead member 352 contracts.
In the case of helical ribbon lead member 354, as ends 354A and
354B are brought closer together, helical slot 360 closes and the
diameter of the helix of lead member 354 expands. Conversely, as
ends 354A and 354B are brought further apart, helical slot 360 is
opened and the diameter of the helix of lead member 354
contracts.
[0141] Cylindrical lead members employed in examples according to
this disclosure, in general, may include several additional
features. In some examples, a lead member may include a
non-conductive material that insulates non-targeted tissue from
stimulation pulses delivered by one or more electrodes connected to
the lead member or otherwise isolates one or more electrodes from,
e.g., other parts of the lead member. In addition to employing
electrodes that protrude from the exterior surface of a cylindrical
lead member to assist in fixation within a vessel (see, e.g., FIG.
18A), the lead member may include an abrasive or otherwise coarse
exterior surface or a drug-eluting coating that promotes tissue
growth around the lead member, e.g. promotes fibrosis. Conversely,
in other examples, a cylindrical lead member according to this
disclosure may include a drug-eluting coating that inhibits tissue
growth, such as fibrosis to, e.g., increase the long term period
over which the cylindrical member may be redeployed within a blood
vessel. Additionally, in some examples, a cylindrical lead member
may include a drug-eluting coating that prevents or inhibits
stenosis of the blood vessel in which it is arranged. In other
examples, the cylindrical lead member may include a number
microhooks or small barbs arranged on an exterior surface to hold
the lead member in place within the blood vessel.
[0142] Cylindrical lead members according to this disclosure may
also be deployed and redeployed with the assistance of, e.g. a cup
and release plate that receive one end of the lead member and serve
to retain the lead member in place when, e.g., a sheath is
retracted to temporarily or chronically deploy the lead member in a
blood vessel. In some examples, the cup may be relatively deep to
encapsulate a large longitudinal length of a proximal end of the
lead member that is configured to expand to deploy the lead member.
The cup may hold and encapsulate the proximal end of the lead
member while a sheath extends over and encapsulates the lead member
and the cup prior to deployment and after the sheath is retracted.
After the sheath is retracted to partially deploy the lead member,
e.g., allow the distal end to expand in the blood vessel, the
sheath may then either be extended again to redeploy the
cylindrical lead member, or the release plate may be extended to
push out and thereby release and deploy the proximal end of the
cylindrical member from the cup. Other examples and a more detailed
explanation of deployment mechanisms including such cup
arrangements are described in U.S. Patent Publication No.
2007/0043420 A1 to Timothy W. Lostetter, filed on Aug. 17, 2005 and
entitled "APPARATUS AND METHOD FOR STENT-GRAFT RELEASE USING A
CAP," the entire content of which is incorporated herein by this
reference.
[0143] In some examples, a cylindrical lead member may include an
electrical stimulator and, in some cases, need not be coupled to an
implantable medical device via a lead. In such examples, the
electrical stimulator on, within or attached to the cylindrical
lead member may be powered by radio frequency pulses delivered from
either an external or a subcutaneously implanted RF transmitter to
a receiver unit arranged with the stimulator or cylindrical lead
member. In other examples, some part of the stimulator or
cylindrical lead member may be composed of a piezoelectric material
that can generate current when excited mechanically by ultra sound
waves transmitted from an external or implanted source.
[0144] Similar to intravascular techniques, transvascular lead
placement proximate a target nerve tissue site generally requires
minimally invasive surgical techniques because the leads are guided
to the site through a blood vessel, e.g., a vein or artery that may
be readily accessible, e.g., transcutaneously through a small
incision. Unlike intravascular, however, transvacular techniques
guide the lead adjacent the target tissue site and then pierce the
vessel wall to arrange the lead and electrodes outside of the
vessel adjacent the nerve tissue at which therapy is directed.
Transvascular lead placement techniques according to this
disclosure provide for lead placement relative to the target nerve
tissue and neighboring blood vessels to improve the therapeutic
effects of electrical stimulation provided to the patient by lead
electrodes. Additionally, guided transvascular lead placement as
described herein may avoid safety risks of such procedures
including, e.g., piercing adjacent vessels, such as an artery. The
disclosed transvascular techniques generally include improving lead
placement by locating target nerve tissue with a sensor, such as an
IVUS imaging system, through a blood vessel adjacent the target
tissue. After a placement location is determined, one or more leads
including one or more electrodes may be deployed through the vessel
wall and anchored to the vessel wall or other tissue near the
target nerve tissue.
[0145] Transvascular techniques generally include improving lead
placement by locating target nerve tissue with a sensor including,
e.g., an IVUS imaging system through a blood vessel adjacent the
target tissue. After an optimal placement location is determined
relative to the nerve tissue with the assistance of the tissue
sensor, one or more leads including one or more electrodes may be
deployed through the vessel wall and anchored to the vessel wall or
other tissue near the target nerve tissue.
[0146] FIGS. 18 and 19 illustrate examples of transvascular lead
placement techniques in the context of vagal nerve stimulation in a
human patient. FIG. 19 is a schematic illustration depicting lead
29 transvascularly placed adjacent vagus nerve 150 outside of
internal jugular vein 158 in patient 12. After or during placement,
lead 29 may be connected to IMD 16 or INS 26 similar to lead 28
shown in FIGS. 1A and 1B respectively. FIG. 20 is a flow chart
illustrating an example method of placing lead 29 in accordance
with the example of FIG. 19. The example method of FIG. 20 includes
deploying a delivery catheter through a lumen of a blood vessel to
a target nerve tissue site (380), identifying a location of the
nerve tissue with respect to the blood vessel with one or more
sensors connected to the delivery catheter (382), advancing an
electrical stimulation electrode from the catheter through a wall
of the blood vessel toward the nerve tissue (384), and energizing
the electrode to deliver electrical stimulation to the nerve tissue
(386). One example of the method illustrated in FIG. 20 will be
described in the context of the example lead placement structure
shown in FIG. 19.
[0147] The arrangement shown in FIG. 19 includes delivery catheter
220, sensor 222, deployment member 224, and spline 370. Sensor 222
is connected to catheter 220 toward a distal end thereof.
Deployment member 224 is extendable and retractable from catheter
220. Spline 370 is also connected to a distal end of catheter 220
and is deployable to stabilize the catheter within jugular vein
158. Sensor 222 is arranged between the distal end of catheter 220
and the location along catheter 220 from which deployment member
224 is extendable and retractable. Deployment member 224 includes
tubular member 226, lead 29, electrode 228, and guidewire 230.
Guidewire 230 includes anchor portion 230A at a distal end thereof.
Electrode 228 is connected toward a distal end of lead 29. Lead 29
and guidewire 230 are received within and advanceable through a
lumen of tubular member 226. Lead 29 is advanceable along guidewire
230.
[0148] In FIG. 19, catheter 220 is deployed through internal
jugular vein 158 of patient 12 to a target nerve tissue stimulation
site. In other examples, catheter 220 may be deployed in other
blood vessels within patient 12 including, e.g., carotid artery
160, or the superior or inferior vena cava. Catheter 220 can be any
suitable delivery catheter capable of intravenous delivery within
patient 12 and adapted to accommodate sensor 222 and deployment
member 224. Sensor 222 is connected to the distal end of catheter
220 and is configured to detect the position of vagus nerve 150
relative to jugular vein 158. Sensor 222, in general, may be any
suitable imaging or guidance system including, e.g., a fiberoptic
endoscope, ultrasound imaging system, or any other on-board imaging
system capable of positioning catheter 220 to advance electrode 228
through jugular vein 158 toward vagus nerve 150 by providing an
image of the area adjacent the location of sensor 222 on catheter
220. In some examples, sensor 222 could be an array of receivers in
relationship to a transmitter that provide an image of surrounding
tissue and structures including vagus nerve 150 and carotid artery
160. In other examples, sensor 222 may be configured to send or
receive signals to or from any of a series of known signal
generators including sonic, electromagnetic, light or radiation
signals. In still other examples, sensor 222 may be an optical
oxygen content sensor that may be used to ensure that lead 29 and
electrode 228 are not directed toward, e.g., carotid artery 160
during lead placement. In some examples, sensor 222 may be employed
in conjunction with one or more opaque markers viewable with
fluoroscopic techniques or with an irrigated lumen that dispenses
contrast media to assist in imaging the position of vagus nerve 150
relative to jugular vein 158. In still other examples, sensor 222
may employed in addition to a separate optical oxygen content or
venous biomarker sensor that may be used to ensure that lead 29 and
electrode 228 are not directed toward, e.g., carotid artery 160
during lead placement. In some such examples, an optical oxygen
content or venous biomarker sensor may be connected to deployment
member 224 to detect the presence of and reduce the risk of
piercing or otherwise damaging carotid artery 160 as deployment
member 224 including electrode 228 is advanced through the wall of
the lumen of jugular vein 158 toward vagus nerve 150.
[0149] In one example, sensor 222 is an intravenous ultrasound
("IVUS") imaging system that is adapted to radiate ultrasonic waves
out from sensor 222 to generate a two dimensional image of the
tissue and structures surrounding catheter 220 and sensor 222. When
activated, sensor 222 may produce an imaging field from ultrasonic
waves produced by and radiating radially from catheter 220 and
sensor 222 (see, e.g., FIG. 11). The size of the imaging field may
vary depending on the particular configuration and capabilities of
sensor 222. The tissues and other structures caught within the
imaging field of sensor 222 may be distinguished from one another
and the relative positioning of the different structures may be
discerned. Therefore, in the context of transvacular lead
placement, vagus nerve 150, jugular vein 158, and carotid artery
160 may be caught within the imaging field of sensor 222 to detect,
e.g., the position of nerve 150 relative to vein 158.
[0150] After sensor 222 identifies the location of vagus nerve 150
with respect to jugular vein 158, deployment member 224 including
electrode 228 may be advanced through the wall of the lumen of
jugular vein 158 toward vagus nerve 150. Deployment member 224, in
general, is extendable and retractable from catheter 220 from,
e.g., an aperture formed in a sidewall thereof. Deployment member
224 includes tubular member 226, lead 29, electrode 228, and
guidewire 230. Tubular member 226 may be any structure including at
least one lumen through which various electrode deployment
structures including, e.g., lead 29 and guidewire 230 may be
advanced to place an electrode outside of vein 158 adjacent vagus
nerve 150. In the example of FIG. 19, tubular member 226 may be a
needle capable of piercing the wall of the lumen of vein 158 and
including a lumen in which lead 29 and guidewire 230 are received
and through which the same are advanceable. Electrode 228 is
connected to lead 29, which is advanceable along guidewire 230.
[0151] With the aid of sensor 222, deployment member 224 is
advanced from catheter 220 through jugular vein 158 toward vagus
nerve 150. Lead 29, to which electrode 228 is connected, and
guidewire 230 may be advanced through a lumen of deployment member
224 to position electrode 228 outside of vein 158 adjacent vagus
nerve 150. Guidewire 230 includes anchor portion 230A at a distal
end thereof that is configured to anchor deployment member 224,
lead 29 and electrode 228, and guidewire 230 to tissue outside of
vein 158. In the example of FIG. 19, anchor portion 230A includes
guidewire 230 formed in a spiral that is configured to be twisted
tissue adjacent vagus nerve 150. Anchor portion 230A can be freed
from the tissue by either untwisting guidewire 230, or in the case
that guidewire 230 is sufficiently flexible, pulling the wire away
from the spiraling anchor portion 230A to effectively unwind and
release the anchor from the tissue.
[0152] Having deployed catheter 220, detected the location of vagus
nerve 150 relative to jugular vein 158, and advanced electrode 228
through vein 158 toward vagus nerve 150, electrical stimulation may
be delivered to vagus nerve 150 via electrode 228. A portion of
lead 29 extending away from a distal end toward which electrode 228
is arranged may be guided to connect with IMD 16. In one example,
lead 29 may be guided intravascularly to an implantation location
of IMD 16 within patient 12. In other examples, at least a portion
of lead 29 may be tunneled through tissue of patient 12 to be
connected to IMD 16. Although the example of FIGS. 18 and 19 is
described with reference to implanted medical device 16 arranged
within patient 12, examples according to this disclosure also
include lead 29 connected transcutaneously to an external medical
device that is configured to deliver electrical stimulation to the
target nerve tissue, e.g., vagus nerve 150. After lead 29 is placed
adjacent vagus nerve 150 outside of jugular vein 158 and connected
to IMD 16, IMD 16, either automatically or as partially or
completely commanded by programmer 24, may deliver electrical
stimulation therapy to and/or receive sensor feedback from vagus
nerve 150 through electrode 228.
[0153] In the example of FIGS. 18 and 19, as well as other examples
disclosed herein, the efficacy of the electrical stimulation
delivered by electrode 228 to vagus nerve 150 may be compared to a
threshold efficacy to determine whether or not electrode 228 is
satisfactorily positioned with respect to nerve 150. Efficacy may
be measured, in general, by verbal feedback from patient 12,
clinician observation of various conditions of patient 12, or
sensory feedback from one or more devices including, e.g., ICD 17
shown in FIG. 1A or cardiac therapy module 104 shown in FIG. 4. For
example, to determine the response to stimulation of vagus nerve
150, ECG, heart rate, blood pressure, blood flow, cardiac output,
and/or breathing, of patient 12 can be sensed or observed. In
another example, efficacy may be measured by a sensor including,
e.g., an accelerometer that determines if stimulation of the neck
muscles or phrenic nerve of patient 12 is occurring with or instead
of stimulation of vagus nerve 150.
[0154] FIGS. 21A-21D show several alternative examples of
deployment member 224 for use in methods and systems according to
this disclosure. In general, FIGS. 21A-21D show different
arrangements and combinations of anchoring members and electrodes
with respect to tubular member 226, lead 29, and guidewire 230 of
deployment member 224. In the interest of simplicity, catheter 220
has been omitted from the illustrations of FIGS. 21A and 21B. In
FIG. 21A, deployment member 224 is advanced through the lumen wall
of jugular vein 158 toward vagus nerve 150 and includes tubular
member 226, lead 29, electrode 228, guidewire 230, and expandable
member 390. In some examples, it may be desirable or necessary to
use expandable member 390 to enlarge the tract along which tubular
member 226 and guidewire 230 are advanced through and outside vein
158 prior to placing lead 29 and electrode 228. In one example
employing expandable member 390, tubular member 226 and guidewire
230 may be advanced through the lumen wall of jugular vein 158
toward vagus nerve 150. Thereafter, expandable member 390 may be
advanced over guidewire 230 and used to enlarge the tract along
which lead 29 and electrode 228 will be advanced. The expandable
member 390 may, in some examples, be a balloon catheter including,
e.g., an angioplasty catheter. Instead of or in addition to
expandable member 390, other tract enlarging devices may be
employed including, e.g., electrosurgical debulking devices or
tissue cutting devices.
[0155] In addition to or in lieu of tract enlargement, in some
examples, expandable member 390 may provide additional
stabilization or biasing of lead 29 or other components of
deployment member 224 outside of jugular vein 158 adjacent vagus
nerve 150. For example, expandable member 390 may push against the
exterior surface of jugular vein 158 as shown in FIG. 21A to bias
lead 29 and electrode 228 toward vagus nerve 150. In another
example, expandable member 390 may further stabilize the placement
of lead 29 and electrode 228 by expanding to apply force on jugular
vein 158 and vagus nerve 150.
[0156] FIG. 21B shows deployment member 224 with anchor 392. In
FIG. 21B, deployment member 224 is advanced through the lumen wall
of jugular vein 158 toward vagus nerve 150 and includes tubular
member 226, lead 29, electrode 228, guidewire 230, and anchor 392.
Anchor 392 is connected to lead 29 and is configured to secure lead
29 and thereby electrode 228 to tissue outside of jugular vein 158
adjacent nerve 150. Anchor 392 may be any number of structures that
are actively or passively deployable from within tubular member 226
to engage tissue within patient 12. In the example of FIG. 21B,
anchor 392 is in the form of passive tines or barbs that protrude
from lead 29 and that may engage tissue outside of jugular vein 158
after lead 29 is advanced through and out of tubular member 226. In
other examples, anchor 392 may come in different shapes and sizes
including, e.g., helical coils, C-shaped members, harpoon-like
structures, hooks, expandable or serrated members, and the like. In
FIG. 21B, anchor 392 is employed in lieu of anchor portion 230A of
guidewire 230. However, in other examples both anchor 392 and
anchor portion 230A may be used to securely deploy lead 29 and
electrode 228 outside of jugular vein 158 adjacent vagus nerve
150.
[0157] The anchors illustrated in FIGS. 14A-14J and described with
reference to intravascular lead placement techniques may also be
used in transvascular techniques disclosed herein. One or more of
the anchors illustrated in FIGS. 14A-14J may be employed, for
example, alone or in combination in a manner as described with
reference to anchor portion 230A of guidewire 230 in FIG. 19. In
such examples, anchor portion 230A of guidewire 230 may take an
alternative form to that shown in FIG. 19 including, e.g., the
harpoon anchors of FIGS. 14B and 14C. In another example, one of
the illustrated anchors of FIGS. 14A-14J may be employed as anchor
392 shown in FIG. 21B.
[0158] FIG. 21C shows catheter 220 with additional electrode 394
and deployment member 224 with additional electrode 396 connected
to tubular member 226. In FIG. 21C, deployment member 224 is
advanced through the lumen wall of jugular vein 158 toward vagus
nerve 150 and includes tubular member 226, lead 29, electrode 228,
guidewire 230, and additional electrodes 394, 396. Although
transvascular placement examples of lead 29 have been described
herein with reference to a single electrode 228 for simplicity, in
practice, lead 29 will commonly include a plurality of electrodes
that may be employed in different anode and cathode combinations to
stimulate vagus nerve 150 as, e.g., described with reference to
electrodes 80-83 in FIG. 2.
[0159] Additionally and as illustrated in FIG. 21C, catheter 220
may include electrode 394 in addition to lead electrode 228. In the
example of FIG. 21C, deployment member 224 may be advanced through
the wall of jugular vein 158 and thereafter used to pull catheter
220 and electrode 394 toward the lumen wall within jugular vein
158. For example, deployment member 224 may include an active or
passive anchor (e.g. anchor portion 230A of FIG. 21A, or anchor 392
of FIG. 21B) that fixes deployment member 224 outside of vein 158
adjacent vagus nerve 150. After deployment member 224 is anchored
outside of jugular vein 158, catheter 220 may be pulled along
deployment member 224 to abut the wall of the lumen of jugular vein
158 as shown in FIG. 21C, thereby positioning electrode 394 within
the vein proximate vagus nerve 150.
[0160] Deployment member 224 may also include electrodes in
addition to lead electrode 228 arranged in different locations
and/or connected to different components. In FIG. 21C, electrode
396 is connected to tubular member 226. In some examples, tubular
member 226 and electrode 396 may be advanced through the wall of
vein 158 toward vagus nerve 150 prior to chronically deploying lead
29 and electrode 228. In such examples, electrode 396 may be used
to deliver test stimulation pulses to vagus nerve 150 to determine
the efficacy of the placement of deployment member 224 outside of
jugular vein 158 with respect to vagus nerve 150. After determining
a position of deployment member that provides a threshold efficacy
in stimulating vagus nerve 150, lead 29 and guidewire 230 may be
advanced through tubular member 226 and lead 29 and electrode 228
may be chronically deployed along the wall of the lumen of jugular
vein 158 adjacent vagus nerve 150.
[0161] FIG. 21D shows guidewire 230 and lead 29 deployed
transvascularly to create a cuff arrangement that wraps around
vagus nerve 150. In FIG. 21D, deployment member 224 is advanced
through the lumen wall of jugular vein 158 toward vagus nerve 150
and includes tubular member 226, lead 29, electrode 228, and
guidewire 230. In some examples, it may be desirable to anchor
and/or localize the stimulation field delivered by electrodes
connected to lead 29 around the nerve. In one example, a curved
member may be deployed from tubular member 226 to loop and thereby
create a cuff around vagus nerve 150. The curved member may be,
e.g., a tubular needle adapted to receive guidewire 230 and/or lead
29. In the example of FIG. 21D, the curved member is guidewire 230,
which is advanced from tubular member 226 of deployment member 224
around vagus nerve 150. After guidewire 230 is arranged around
nerve 150, lead 29 and electrode 228 may be advanced along the
guidewire to wrap around the nerve.
[0162] In certain applications, transvascular lead placement may
carry certain inherent risks. In some examples, advancing medical
leads from within a lumen of a blood vessel, through a wall of the
vessel to place the leads adjacent nerve tissue in an extravascular
space may carry the risk of piercing or otherwise damaging other
neighboring biological structures including, e.g., other blood
vessels. In the context of vagal nerve stimulation/sensing examples
disclosed herein, for example, transvascularly placing a lead
adjacent vagus nerve 150 may carry the risk of piercing or
otherwise causing damage to carotid artery 160 adjacent the nerve
and jugular vein 158. Therefore, in some examples according to this
disclosure, transvascular lead placement techniques may employ a
deployment member part or all of which is constructed from a shape
memory material such that the deployment member is configured to
pass laterally through a vessel wall and turn outside of the vessel
to be arranged longitudinally along the vessel adjacent the target
nerve tissue. In this way, the deployment member and other
components of the transvascular lead placement apparatus may reduce
the risk of advancing too far laterally from the blood vessel and,
e.g., piercing an adjacent vessel such as an artery.
[0163] FIG. 22 shows one example of deployment member 224 employing
tubular member 226 constructed from a shape memory material.
Examples disclosed herein may use a variety of shape memory
materials including, e.g., nickel titanium (NiTi) alloys. NiTi is a
shape memory alloy, which is sometimes referred to as Nitinol.
Other shape-memory alloys may also be used in examples disclosed
herein including, e.g., copper tin (CuSn), indium titanium (InTi),
and manganese copper (MnCu) alloys. A reversible, solid phase
transformation known as martensitic transformation is the physical
mechanism that underpins shape memory materials. Generally
speaking, shape memory materials form a crystal structure that can
undergo a change from one crystal form to another initiated by a
temperature change or application of force. Above its
transformation temperature, Nitinol, e.g., is superelastic, able to
withstand a small amount of deformation when a load is applied and
return to its original shape when the load is removed. Below its
transformation temperature, it displays the shape memory effect.
When it is deformed it will remain in that shape until heated above
its transformation temperature, at which time it will return to its
original shape. Nitinol is typically composed of approximately 50
to 55.6% nickel by weight. However, small changes in material
composition can change the transition temperature of the alloy
significantly. As such, Nitinol may or may not be superelastic at
room temperature. The flexibility and unique properties of Nitinol
to be used in a wide range of temperatures makes it suitable for
many applications, particularly in medicine.
[0164] In FIG. 22, deployment member 224 includes tubular member
226, lead 29, electrode 228, and guidewire 230. Tubular member 226
may be any structure including at least one lumen through which
various electrode deployment structures including, e.g., lead 29
and guidewire 230 may be advanced to place an electrode outside of
vein 158 adjacent vagus nerve 150. In the example of FIG. 22,
tubular member 226 may be a needle capable of piercing the wall of
the lumen of vein 158 and including a lumen in which lead 29 and
guidewire 230 are received and through which the same are
advanceable. Electrode 228 is connected to lead 29, which is
advanceable along guidewire 230.
[0165] Deployment member 224 is advanced from catheter 220 through
jugular vein 158 toward vagus nerve 150. Lead 29, to which
electrode 228 is connected, and guidewire 230 may be advanced
through a lumen of deployment member 224 to position electrode 228
outside of vein 158 adjacent vagus nerve 150. In the example of
FIG. 22, tubular member 226 is constructed from a shape memory
material including, e.g., Nitonol and generally takes an S-shape
after being advanced through the lumen of from catheter 220 (shown
in FIG. 19) through the wall of jugular vein 158. The material
properties and shape of tubular member 226 reduce the risk that the
needle, or another component of deployment member 224 will advance
too far laterally from jugular vein 158 and, e.g., pierce or
otherwise damage carotid artery 160. After tubular member 226 is
advanced through the wall of vein 158, guidewire 230 may be
deployed and lead 29 and electrode 228 may be advanced along
guidewire 230 to arrange electrode 228 adjacent vagus nerve
150.
[0166] In other examples according to this disclosure, other
components of deployment member 224 may be constructed from a shape
memory material. For example, guidewire 230 may, in addition to or
in lieu of tubular member 226, be constructed from a shape memory
material including, e.g., Nitonol. In some such examples, tubular
member 226 of deployment member 224 is advanced from catheter 220
toward vagus nerve 150. Lead 29, to which electrode 228 is
connected, and guidewire 230 may be advanced through a lumen of
tubular member 226 to position electrode 228 outside of vein 158
adjacent vagus nerve 150. In particular, guidewire 230 is
constructed from a shape memory material and generally takes an
S-shape to pass out of tubular member 226, through the wall of vein
158, and run longitudinally along and adjacent to vagus nerve 150
outside of vein 158. After guidewire 230 is advanced through the
wall of vein 158, lead 29 and electrode 228 may be advanced along
guidewire 230 to arrange electrode 228 adjacent vagus nerve
150.
[0167] The extra, intra, and transvascular lead placement
techniques disclosed herein may benefit, in some examples, from
electrode pairs arranged in flanking, non-contacting relationship
with the target nerve tissue. In one example, multiple leads are
arranged longitudinally on opposing sides of and including
electrodes in non-contacting relationship with the target nerve
tissue. In another example, a single lead including multiple
electrodes is arranged such that at least two of the electrodes are
arranged on opposing sides of and in non-contacting relationship
with the target nerve tissue. Such flanking, non-contacting
electrode arrangements may provide one or more anode and cathode
electrode combinations for electrical stimulation across the target
nerve tissue without the deleterious effects of tissue contacting
techniques, such as may be caused by, e.g., cuff electrodes.
[0168] FIGS. 23A and 23B illustrate example arrangements of
electrode pairs in flanking, non-contacting relationship with vagus
nerve 150. The example of FIG. 23A includes multiple leads and may
be applicable to different combinations of intra, extra, and
transvascular lead placement techniques disclosed herein. The
example of FIG. 23B includes a single lead including a pair of
electrodes in flanking, non-contacting relationship with vagus
nerve 150. The example of FIG. 23B may be generally applicable to
extra and transvascular lead placement techniques according to this
disclosure.
[0169] The example of FIG. 23A includes leads 400 and 402, and
electrodes 228. In FIG. 23A, Lead 400 is arranged longitudinally
along one side of vagus nerve 150. Lead 402 is arranged
longitudinally along a generally opposing side of vagus nerve 150
across from lead 400. Each of leads 400 and 402 include a plurality
of electrodes 228 connected to the distal end of each lead. In the
example of FIG. 23A, each lead 400 and 402 includes four electrodes
228. However, in other examples, leads 400, 402 may include fewer
or more electrodes and may include different numbers of electrodes.
Additionally, although FIG. 23A shows two leads 400, 402, other
examples may include more than two leads including, e.g., four or
six leads, two of each of which are respectively arranged
longitudinally on opposing sides of and including electrodes in
non-contacting relationship with vagus nerve 150.
[0170] The example leads 400 and 402 shown in FIG. 23A may be
placed within patient 12 according to different combinations of
intra, extra, and transvascular lead placement techniques disclosed
herein. For example, lead 400 may be placed intravascularly within
jugular vein 158 adjacent vagus nerve 150, while lead 402 is placed
extravascularly within carotid sheath 156. In another example, lead
400 may be placed intravascularly within jugular vein 158 adjacent
vagus nerve 150, while lead 402 is placed transvascularly through
the wall of vein 158 to an extravascular location adjacent the
nerve. In still another example, both leads 400 and 402 may be
placed extravascularly within carotid sheath 156 adjacent vagus
nerve 150. Similarly, both leads 400 and 402 may be placed
transvascularly through the wall of vein 158 to an extravascular
location adjacent vagus nerve 150.
[0171] Pairs of electrodes 228 from leads 400, 402 may be employed
to provide one or more anode/cathode combinations for electrical
stimulation across vagus nerve 150. The neurostimulator or other
device to which leads 400, 402 are connected may include a
switching module as described with reference to neurostimulation
module 106 of IMD 16 in FIG. 2. The switching module may
selectively couple pairs of electrodes 228 to a signal generator
and/or sensing module to form different anode-cathode combinations
as indicated by dashed electrical field lines 404 in FIG. 23A. The
switching module may include, e.g., a switch array, switch matrix,
multiplexer, or any other type of switching device suitable to
selectively couple stimulation energy to selected electrodes.
[0172] The example of FIG. 23B shows deployment member 224 that is
configured to be advanced and retracted from, e.g., a delivery
catheter (not shown in FIG. 23B) through the wall of jugular vein
158 toward vagus nerve 150. Deployment member 224 includes tubular
member 226, lead 29, and a pair of electrodes 228. Tubular member
226 may be any structure including at least one lumen through which
various electrode deployment structures including, e.g., lead 29
and a guide member may be advanced to place an electrodes 228 in
flanking, non-contacting relationship with vagus nerve 150.
Electrodes 228 are connected to lead 29, which is advanceable
through tubular member along, e.g., a guide wire or stylus. In the
example of FIG. 23B, lead 29 includes two electrodes 228. However,
in other examples, lead 29 may include more electrodes including,
e.g., four or six electrodes arranged in opposing pairs with
respect to vagus nerve 150.
[0173] Deployment member 224 is advanced through jugular vein 158
toward vagus nerve 150. Lead 29, to which electrodes 228 are
connected, may be advanced through a lumen of tubular member 226 to
position one electrode 228 inside jugular vein 158 and one
electrode 228 outside of vein 158 such that the two electrodes 228
flank vagus nerve 150 as shown in FIG. 23B. In the example of FIG.
23B, lead 29 and electrodes 228 may be guided along, e.g., a
guidewire that is constructed from a shape memory material as
described with reference to FIG. 22. Although the example of FIG.
23B illustrates lead 29 and electrodes 228 placed transvascularly,
other examples may include lead 29 placed extravascularly adjacent
vagus nerve 150 in carotid sheath 156. After lead 29 and electrodes
228 are placed with respect to vagus nerve 150, the pair of
electrodes may be employed to provide electrical stimulation across
vagus nerve 150. In some examples, the neurostimulator or other
device to which lead 29 is connected may include a signal generator
and/or sensing module to couple and energize electrodes 228 in
anode-cathode combinations to stimulate vagus nerve 150 as
indicated by dashed electrical field line 404 in FIG. 23B.
[0174] Examples according to this disclosure generally provide
medical lead placement proximate nerve tissue within a patient for
electrical stimulation of the tissue without the use of potentially
deleterious electrode configurations including e.g., cuff
electrodes. Techniques disclosed herein also generally provide
flexible placement techniques and structures by employing one or
more temporary lead placements and stimulation tests, prior to
chronically placing the leads within the patient for nerve tissue
stimulation. Furthermore, techniques according to this disclosure
are adapted to enable minimally invasive introduction of the
medical leads into the patient. Implantable electrical stimulation
systems and methods in accordance with this disclosure may be used
to deliver therapy to patients suffering from conditions that range
from chronic pain, tremor, Parkinson's disease, and epilepsy, to
urinary or fecal incontinence, sexual dysfunction, obesity,
spasticity, and gastroparesis. Specific types of electrical
stimulation therapies for treating such conditions include, e.g.,
cardiac pacing, neurostimulation, muscle stimulation, or the
like.
[0175] Various examples have been described in this disclosure.
These and other examples are within the scope of the following
claims.
* * * * *