U.S. patent application number 10/337208 was filed with the patent office on 2003-08-28 for single pass lead system.
This patent application is currently assigned to Cardiac Pacemakers, Inc.. Invention is credited to Bartig, Jeffrey T., Booker,, Robert S. III, Carlson, Gerrard M., Cole, Mary Lee, Flynn, David M., Goebel, Gary W., Heil, John E., Heil,, Ronald W. JR., Heitkamp, Douglas A., Hsu, William, Janke, Aaron W., Kelley, Peter T., Lin, Yayun, Lindstrom, Curtis C., Peterfeso, Randall M., Scheiner, Avram, Warren, Jay A., Werlein, Carol, Zhu, Qingsheng.
Application Number | 20030163184 10/337208 |
Document ID | / |
Family ID | 22392767 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030163184 |
Kind Code |
A1 |
Scheiner, Avram ; et
al. |
August 28, 2003 |
Single pass lead system
Abstract
A single-pass endocardial lead electrode adapted for
implantation in, on or about the heart and for connection to a
system for monitoring or stimulating cardiac activity includes a
lead body which is adapted for implantation within a single chamber
of the heart, or multiple chambers of the heart. The lead includes
a first distal end electrode which has a first electrical
conducting surface. The lead body also has a second electrode which
has a second electrical conducting surface. The first and second
electrodes are either passively or actively attached to the wall of
the heart. The lead body also includes a curved portion which
facilitates the positioning of the second electrode. The main lead
body alternatively includes a recess into which an atrial lead body
and an active fixation element attached to one end can travel from
a recessed position to a position for fixation to the wall of the
heart. The lead is attached to a pulse generator for producing
pulses to the multiple sites within the heart.
Inventors: |
Scheiner, Avram; (Vadnais
Heights, MN) ; Hsu, William; (Circle Pines, MN)
; Flynn, David M.; (Lino Lakes, MN) ; Zhu,
Qingsheng; (Little Canada, MN) ; Heil, John E.;
(White Bear Lake, MN) ; Heil,, Ronald W. JR.;
(Roseville, MN) ; Lindstrom, Curtis C.;
(Roseville, MN) ; Booker,, Robert S. III; (St.
Paul, MN) ; Lin, Yayun; (St. Paul, MN) ;
Kelley, Peter T.; (Buffalo, MN) ; Warren, Jay A.;
(North Oaks, MN) ; Carlson, Gerrard M.; (Champlin,
MN) ; Werlein, Carol; (Ham Lake, MN) ; Janke,
Aaron W.; (St. Paul, MN) ; Cole, Mary Lee;
(St. Paul, MN) ; Bartig, Jeffrey T.; (Maplewood,
MN) ; Goebel, Gary W.; (Vadnais Heights, MN) ;
Heitkamp, Douglas A.; (White Bear Lake, MN) ;
Peterfeso, Randall M.; (St. Paul, MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Cardiac Pacemakers, Inc.
|
Family ID: |
22392767 |
Appl. No.: |
10/337208 |
Filed: |
January 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10337208 |
Jan 6, 2003 |
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09643125 |
Aug 21, 2000 |
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6505082 |
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09643125 |
Aug 21, 2000 |
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09120824 |
Jul 22, 1998 |
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6212434 |
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Current U.S.
Class: |
607/122 |
Current CPC
Class: |
A61N 1/0563 20130101;
A61N 1/0573 20130101 |
Class at
Publication: |
607/122 |
International
Class: |
A61N 001/05 |
Claims
What is claimed is:
1. An endocardial heart lead system, comprising: an elongated
generally flexible tubular housing having a proximal end for
connection to a device and distal end for placement, in a use
position, through the right atrium to the right ventricle of a
heart; a pair of ventricular electrodes respectively at and
adjacent the distal end of the lead for contact in the ventricle
and receiving ventricular signals of the heart; an SVC electrode
positioned on the tubular housing at a position spaced from the
distal end for placement in the superior vena cava when the lead
system is in the heart; an atrial electrode positioned on the
tubular housing at a position spaced from the distal end and from
the SVC electrode for placement in the atrium when the lead system
is in the heart; the tubular housing including conductors therein
connected to the electrodes and for connection to a device at the
proximal end; and said tubular housing having a curved portion,
taking the form of a lateral protrusion along said tubular housing,
in region of the atrial electrode to mechanically bias the atrial
electrode into contact with the wall of the atrium of the heart
when the lead system is in the use position.
2. A lead adapted for implantation in, on or about the heart and
for connection to a system for monitoring or stimulating cardiac
activity, said lead comprising: a lead body having a curved portion
at a selected distance from the distal end of the lead body; a
first electrode attached to the lead body at the distal end of the
lead body for contact with a first chamber of the heart; and a
second electrode attached to the lead body, the second electrode
positioned a distance from the first electrode on the curved
portion of the lead body to facilitate attachment of the second
electrode to a second chamber of the heart.
3. A single pass dual chamber lead adapted for endocardial
implantation in, on or about the heart and for connection to a
system for monitoring or stimulating cardiac activity, said system
comprising: a signal generator for producing pulses to apply to the
heart; a main lead body adapted to carry signals to and from the
heart; a first electrode having an active fixation portion, said
main lead body having a first recess therein housing the first
electrode, the first electrode capable of moving between a first
recessed position within said first recess and a second extended
position outside the first recess so that the active fixation
portion of the distal electrode can attach to the wall of the
heart; and a second electrode associated with the main lead body,
the first electrode housed within a first chamber of the heart and
the second electrode housed within a second chamber in the heart,
the second electrode having an active fixation portion, said main
lead body having a second recess therein housing the second
electrode, the second electrode capable of moving between a first
recessed position within said second recess and a second extended
position outside the second recess so that the active fixation
portion of the proximal electrode can attach to the wall of the
heart.
4. A single pass dual chamber lead adapted for endocardial
implantation in, on or about the heart and for connection to a
system for monitoring or stimulating cardiac activity, said system
comprising: a signal generator for producing pulses to apply to the
heart; a main lead body adapted to carry signals to and from the
heart; a second lead body attached to the main lead body, the
second lead body having an active fixation portion for attachment
to the wall of the heart; and a first electrode attached to the
main lead body; and a second electrode attached to the second lead
body near the active fixation portion.
5. A lead adapted for endocardial implantation in, on or about the
heart and for connection to a system for monitoring or stimulating
cardiac activity, said system comprising: a lead body; a first
electrode attached to the distal end of the lead body; and a second
electrode attached to the lead body a selected distance away from
the first electrode, the portion of said lead body between the
first electrode and second electrode having a curve therein to
facilitate positioning of the first electrode and the second
electrode within the heart.
6. A system for detecting arrhythmias of the heart and for
delivering signals to the heart, said system comprising: an
electronics system further comprising, a cardiac activity sensor;
and a signal generator which produces signals to stimulate the
heart; and a lead adapted for endocardial implantation in, on or
about the heart and for connection to the electronic system, said
lead further comprising: a main lead body having a first recess
therein; a supplemental lead body carrying a first electrode, said
supplemental lead body capable of being moved between a first
position substantially within the first recess, and a second
position substantially outside the first recess; and a second
electrode attached to the lead body.
7. A lead comprising: a lead body; a first leg having at least one
pacing electrode; and a second leg having at least one pacing
electrode, said first and second leg for positioning within a
chamber of the heart; wherein the first leg is positioned at a
first site within a single chamber of the heart and the second leg
is positioned at a second site within the single chamber of the
heart.
8. A lead comprising: a lead body having a curved end portion; a
first leg having at least one pacing electrode; and a second leg
having at least one pacing electrode, said first and second leg for
positioning within a chamber of the heart; and the first pacing
electrode and the second pacing electrode positioned at two
positions on the curved end portion of the lead body, said curved
end portion being positioned within a single chamber of the heart
so that the first pacing electrode is located at a first position
within the single chamber and the second pacing electrode is
located at a second position with the single chamber of the
heart.
9. A lead comprising: a main lead body adapted to carry signals to
and from a heart, the main lead body having a first recess therein;
a first leg associated with the main lead body, the first leg
including a first electrode having an active fixation portion, the
first electrode removably disposed within the first recess; and a
second leg associated with the main lead body, the second leg
including a second electrode; and where the first recess receives
the first electrode therein.
10. An implantable electrode with a helical tip comprising: an
electrode having a distal end and a proximal end; and a helix
disposed on said electrode, which helix is aligned along a radial
axis of the electrode at said distal end; and said implantable
electrode having at least one feature selected from the group
consisting of: a) said helix having a coating of an insulating
material on 5-95% of its surface, b) said helix having at least
part of its surface beyond said distal end of said electrode and
said distal end of said electrode having a porous conductive
surface, c) a conductive porous surface at said distal end of said
electrode, and d) a porous conductive surface at the distal end of
the electrode having an insulating coating covering from 5-95% of
the surface of said porous conductive surface.
11. A distal tip electrode adapted for implantation in, on or about
the heart and for connection to a system for monitoring or
stimulating cardiac activity, said electrode comprising: an
electrode tip; a porous conductive element disposed at a distal end
of the electrode tip; a surface area at the distal end of the
electrode tip; a helix disposed within said electrode, said helix
comprising a conductor disposed in helical shape, wherein said
helix travels along a radial axis of the electrode through said
surface area; and a helix guiding mechanism for directing movement
of the helix during travel.
12. An electrode adapted for implantation in, on or about the heart
and for connection to a system for monitoring or stimulating
cardiac activity, said electrode comprising: a lead body having a
first end and a second end; an electrode disposed proximate the
first end of the lead body; connector terminal disposed at said
second end of the lead body, said connector terminal for connecting
with a pulse generating unit; an electrode tip disposed proximate
one end of the electrode; a surface at the distal end of the
electrode tip, said surface further comprising an electrical
conducting surface wherein said surface is comprised of a porous
conductive element; a helix disposed within said electrode, said
helix comprising a conductor disposed in a helical shape, wherein
said helix travels along a radial axis of the electrode through
said surface thereby placing said helix in extension and
retraction; and a helix guiding groove for directing movement of
the helix during extension and retraction of said helix.
13. A lead adapted for implantation in, on or about the heart and
for connection to a system for monitoring or stimulating cardiac
activity, said lead comprising: a lead body having a curved portion
at a selected distance from the distal end of the lead body; an
first electrode attached to the lead body; a second electrode
attached to one side of the curved portion of the lead body; said
first electrode disposed at the distal end of the lead body for
contact with a first chamber of the heart; and said second
electrode positioned a distance from the first electrode on the
curved portion of the lead body to facilitate attachment of the
second electrode to a second chamber of the heart, where the second
electrode protrudes outwardly from the lead body.
14. An electrode adapted for endocardial implantation in, on or
about the heart and for connection to a system for monitoring or
stimulating cardiac activity, said electrode comprising: an
electrode end; a first electrically conducting surface at the
distal end of the electrode end; and a lead body having a
circumferential outer surface, said lead body attached to said
electrode end, said lead body having second electrical conduction
surface protruding from a portion of the circumference of said lead
body.
15. A bifurcated lead adapted for implantation in, on or about a
heart, the lead comprising: a main lead adapted to carry signals to
and from the heart, the main lead body extending from a proximal
end to a distal end, the distal end of the main lead body having a
first electrode leg and a second electrode leg; the first electrode
leg including a first electrode assembly comprising a bipolar
electrode having a first electrode and a second electrode, the
first electrode assembly being adapted to be disposed within a
first chamber of the heart; and the second electrode leg including
a second electrode assembly, the second electrode assembly
comprising a bipolar electrode having a third electrode and a
fourth electrode, the second electrode assembly being adapted to be
disposed within a second chamber of the heart.
16. A lead adapted for implantation in, on or about a heart, the
lead comprising: a main lead body adapted to carry signals to and
from the heart, the main lead body extending from a proximal end to
a distal end, the distal end of the main lead body having at least
one leg; the at least one leg having an active fixation portion;
and a movement assembly operatively coupled with the active
fixation portion of the at least one leg, the movement assembly
configured to extend and retract the active fixation portion, the
movement assembly comprising: a housing having an internally
threaded portion; and an externally threaded collar engaged with
the internally threaded housing.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. patent
application Ser. No. 09/643,125, filed on Aug. 21, 2000, which is a
division of U.S. patent application Ser. No. 09/120,824, filed on
Jul. 22, 1998, now issued as U.S. Pat. No. 6,212,434, the
specifications of which are incorporated herein by reference.
[0002] This patent application is related to U.S. patent
application Ser. No. 10/288,155, filed on Nov. 5, 2002 entitled:
HIGH IMPEDANCE ELECTRODE TIP; U.S. patent application Ser. No.
09/121,020, filed on Jul. 22, 1998, entitled SINGLE PASS
DEFIBRILLATION/PACING LEAD WITH PASSIVELY ATTACHED ELECTRODE FOR
PACING AND SENSING; U.S. patent application Ser. No. 09/129,348,
filed on Aug. 5, 1998, now issued as U.S. Pat. No. 6,119,043; U.S.
patent application Ser. No. 09/661,531, filed on Sep. 14, 2000, now
issued as U.S. Pat. No. 6,345,204; U.S. Pat. No. 09/121,288, filed
on Jul. 22, 1998, now issued as U.S. Pat. No. 6,501,994; U.S.
patent application Ser. No. 09/121,005, filed on Jul. 22, 1998, now
issued as U.S. Pat. No. 6,141,594; U.S. patent application Ser. No.
09/121,019, filed on Jul. 22, 1998, now issued as U.S. Pat. No.
6,085,119; U.S. patent application Ser. No. 09/121,006, filed on
Jul. 22, 1998, now issued as U.S. Pat. No. 6,152,954; U.S. patent
application Ser. No. 09/121,018, filed on Jul. 22, 1998, now issued
as U.S. Pat. No. 6,321,122; and U.S. patent application Ser. No.
08/996,355, filed on Dec. 22, 1997, now issued as U.S. Pat. No.
5,885,221, each of which is assigned to a common assignee. The
related applications are incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0003] The present invention relates to the field of leads for
correcting arrhythmias of the heart. More particularly, this
invention relates to a single lead which can simultaneously pace,
sense, and/or defibrillate one or more chambers of the heart.
BACKGROUND OF THE INVENTION
[0004] Electrodes implanted in the body for electrical
cardioversion or pacing of the heart are well known. More
specifically, electrodes implanted in or about the heart have been
used to reverse (i.e., defibrillate or cardiovert) certain life
threatening arrhythmias, or to stimulate contraction (pacing) of
the heart, where electrical energy is applied to the heart via the
electrodes to return the heart to normal rhythm. Electrodes have
also been used to sense near the sinus node in the atrium of the
heart and to deliver pacing pulses to the atrium. An electrode
positioned in any chamber of the heart senses the electrical
signals that trigger the heartbeat. Electrodes detect abnormally
slow (bradycardia) or abnormally fast (tachycardia) heartbeats. In
response to the sensed bradycardia or tachycardia condition, a
pulse generator produces pacing or defibrillation pulses to correct
the condition. The same electrode used to sense the condition is
also used in the process of delivering a corrective pulse or signal
from the pulse generator of the pacemaker.
[0005] There are four main types of pulses or signals which are
delivered by a pulse generator. Two of the signals or pulses are
for pacing the heart. First of all, there is a pulse for pacing the
heart when it is beating too slowly. The pulses trigger the heart
beat. These pulses are delivered at a rate to increase the
abnormally low heart rate to a normal or desired level. The second
type of pacing is used on a heart that is beating too fast. This
type of pacing is called antitachycardia pacing. In this type of
pacing, the pacing pulses are delivered initially at a rate much
faster or slower than the abnormally beating heart until the heart
rate can be returned to a normal or desired level. The third and
fourth types of pulses are delivered through large surface area
electrodes used when the heart is beating too fast or is
fibrillating, respectively. The third type is called cardioversion.
This is delivery of a relatively low energy shock, typically in the
range of 0.5 to 5 joules, to the heart. The fourth type of pulse or
signal is a defibrillation signal which is the delivery of a high
energy shock, typically greater than 25 joules, to the heart.
[0006] Sick sinus syndrome and symptomatic AV block constitute the
major reasons for insertion of cardiac pacemakers today. Cardiac
pacing may be performed by the transvenous method or by electrodes
implanted directly onto the epicardium. Most commonly, permanent
transvenous pacing is performed using one or more leads with
electrodes positioned within one or more chambers of the heart. The
distal end of a lead, sometimes referred to as a catheter, may be
positioned in the right ventricle or in the right atrium through a
subclavian vein. The lead terminal pins are attached to a pulse
generator which is implanted subcutaneously.
[0007] Some patients require a pacing system to detect and correct
an abnormal heartbeat in both the atrium and ventricle which may
have independent rhythms, as well as a defibrillation system to
detect and correct an abnormally fast heart rate (tachycardia
condition). In the past, a common practice for a patient having to
pace both of these chambers would be to provide two different leads
attached to the heart. One would be implanted for delivering
pacing/sensing/defibrillating to the ventricle and one to the
atrium to both pace and sense.
[0008] Having two separate leads implanted within the heart is
undesirable for many reasons. Among the many reasons are that the
implantation procedure for implanting two leads is more complex and
also takes a longer time when compared to the complexity and time
needed to implant a single lead. In addition, two leads may
mechanically interact with one another after implantation which can
result in dislodgment of one or both of the leads. In vivo
mechanical interaction of the leads may also cause abrasion of the
insulative layer along the lead which can result in an electrical
failure of one or both of the leads. Another problem is that as
more leads are implanted in the heart, the ability to add other
leads is reduced. If the patient's condition changes over time the
ability to add leads is restricted. Two separate leads also
increase the risk of infection and may result in additional health
care costs associated with re-implantation and follow-up.
[0009] Because of these problems, catheters having electrodes for
both pacing and sensing in both chambers of the heart on a single
lead body have been used. These leads, known as single pass lead
designs, have drawbacks since the single pass lead designs utilize
"floating" electrodes or electrodes which are not attached to the
endocardial wall of the heart. The catheter having the electrodes
which forms the lead body is essentially straight. The electrode or
electrodes may float or move slightly at a distance from the
endocardial wall within the heart.
[0010] The portion of the lead positioned within the atrium of
current single-pass endocardial leads has one or more electrodes
which are incorporated into the lead body as an electrically
conductive cylindrical or semicylindrical ring structure. In other
words, the lead body is basically cylindrical and the one or more
electrodes positioned within the atrium of the heart are
cylindrical metal structures incorporated into the cylindrical lead
body. The ring electrode structures do not allow for tissue
ingrowth into the electrode to enhance electrode stabilization
within the atrium. Since the location of the electrodes is not
fixed against the atrial wall, the performance of these leads is
more variable. In other words, variations with respect to
electrical contact with the wall of the atrium results in
suboptimal electrical sensing capability and pacing delivery
capability. Typically, the pacing characteristics of a floating
electrode are less desirable than the pacing characteristics
associated with an electrode fixed to the endocardial wall of the
heart. The performance of a lead using a floating electrode is
poorer than a lead having electrodes which contact or are nearer
the walls of the heart.
[0011] Another problem associated with the current straight single
pass leads, is that these electrodes may be unable or less able to
sense an arrhythmic condition. In addition, the applied voltage or
current needed for pacing may be ineffective. Additional energy may
have to be used to pace the heart thereby depleting energy from the
battery of the pulse generator of the pacing system.
[0012] There is a real need for a single-pass transvenous pacing or
defibrillation lead. A single-pass lead equipped with such an
electrode arrangement would allow for better sensing capability and
better pacing therapy to the heart. In addition, there is a need
for a single-pass lead having an electrode for positioning within
the atrium that allows for tissue ingrowth. Such an electrode would
further enhance lead stabilization within the heart. There is also
a need for a single-pass endocardial lead which has an electrode
for placing within the right atrium of the heart that accommodates
eluting anti-inflammatory drugs. There is still a further need for
a single pass endocardial lead that is easier for a surgeon to
implant.
SUMMARY OF THE INVENTION
[0013] A single-pass endocardial lead electrode adapted for
implantation and for connection to a system for monitoring or
stimulating cardiac activity includes a lead body. The lead, in one
embodiment, includes a first distal end electrode or electrode pair
which has a first electrical conducting surface. The lead body also
has a second electrode or electrode pairs which has a second
electrical conducting surface. The second electrode or electrode
pair is adapted for positioning and fixation to the wall of the
atrium of the heart. A passive fixation element is used as part of
the second electrode or electrode pair. The lead body also includes
a curved portion which facilitates the positioning and fixing of
the second electrode or electrode pair. The curved portion has a
radius near the natural radius of the atrium. The first and second
electrode may be a single electrode or a bipolar pair. The curve in
the lead body, which is positioned in the right atrium of the heart
after implantation, positions the electrode closer to the wall of
the atrium to enhance the sensing and pacing performance of the
lead.
[0014] The electrical conducting surface of the second electrode
has a relatively small diameter when compared to previous
electrodes. The small diameter electrode results in superior
electrical performance when compared to previous single-pass
endocardial leads. The benefits include increased pacing impedance,
increased P-wave signal amplitudes and decreased atrial pacing
capture thresholds. The increased impedance lets the battery energy
source last longer. The single-pass lead equipped with an atrial
electrode capable of being fixed to the endocardial wall allows for
better sensing capability and better current delivery to the heart.
The second electrode may be placed on the outside of the curved
portion of the lead body. The fixed atrial electrode enhances lead
stabilization within the heart and the result is no need for two
leads in the heart. The costs and complexity associated with
implanting and follow-up care for the single pass lead is less than
two separate leads.
[0015] In another embodiment, the lead includes a first distal end
electrode or pair of electrodes for positioning in the ventricle
and a second proximal electrode or pair of electrodes for
positioning in the atrium. The second electrode or pair of
electrodes are adapted for positioning and fixation to the wall of
the atrium of the heart. An active fixation element is used as part
of the second electrode or electrode pair. The lead body also may
include a curved portion which facilitates the positioning and
fixing of the second electrode or second pair of electrodes. The
lead body also includes at least one recess for positioning an
active fixation element within the recess.
[0016] In yet another embodiment, the recess is able to house the
active fixation electrode as well as a portion of a lead body
associated with the atrium (atrial lead body). By moving the
terminal pin with respect to a yoke, the lead body is moved out of
the recess. The atrial lead body can be a straight lead or a
J-shaped lead. The type of atrial lead body used will depend on the
placement of the lead within the atrium of the heart and the
preference of the surgeon doing the placement. The advantage is
that the active fixation electrode is placed into the recess during
placement of the lead to prevent it from attaching inadvertently to
the subclavian vein or other tissue while it is being inserted.
[0017] In another embodiment, an active fixation electrode is
included with the lead that can be controllably moved from a
recessed position to an attachment position by rotating the
terminal pin attached to the conductor coil which is attached to
the body of the active fixation electrode.
[0018] In yet another embodiment, the lead includes a distal end
having a first pacing electrode or electrode pair. The distal end
of the lead body also has a second electrode or electrode pair. The
second electrode or electrode pair is positioned away from the
first electrode or electrode pair. The first and second electrodes
fit within a single chamber of the heart for multi-site pacing or
pulse delivery to the single chamber. In a first embodiment, the
distal end of the lead body includes a curved portion which
facilitates the positioning of the first and second electrode or
electrode pair within the single chamber. The first electrode may
be a single electrode associated with a unipolar arrangement or may
be one of a pair of electrodes associated with a bipolar electrode.
The second electrode may be either unipolar or bipolar as well.
[0019] In another embodiment, the lead includes a first leg for the
first electrode and a second leg for the second electrode. One of
the first or second legs is movable between a withdrawn position
and an extended position. When inserting the lead, the withdrawn
leg is within the lead body which eases the task of insertion. In
yet another embodiment, the two legs may be withdrawn to a position
within the lead for easy insertion. In each of the embodiments, the
first electrode and second electrode can be passively or actively
fixed.
[0020] In another embodiment, the lead extends from two terminal
legs at a proximal end of the lead to two electrode legs at a
distal end of the lead. Each electrode leg includes a first
electrode and a second electrode. The second electrode is adapted
for positioning and fixation to the wall of the atrium of the
heart.
[0021] In one embodiment, a bifurcated lead includes a main lead
body which is adapted to carry signals to and from the heart. The
main body extends to a first electrode assembly which has a first
electrode and a second electrode, and is adapted to be implanted
within a first chamber of the heart. The body also extends to a
second electrode assembly which has a third electrode and a fourth
electrode, and is adapted to be implanted within a second chamber
of the heart. In another embodiment, the lead body has an
intermediate portion which comprises a quad lumen body. In yet
another embodiment, the first electrode leg and the second
electrode leg each have a semi-circular profile. A yoke, in another
configuration, couples the first electrode leg and the second
electrode leg with the intermediate portion. The first electrode
assembly and the second electrode assembly can be either actively
or passively fixated within the heart. A mesh screen can also be
provided to allow for better tissue in-growth.
[0022] In another embodiment, a bifurcated lead includes a main
lead body which is adapted to carry signals to and from the heart.
The main body extends to a first electrode assembly which has a
first electrode and a second electrode, and is adapted to be
implanted within a first chamber of the heart. The body also
extends to a second electrode assembly which has a third electrode
and a fourth electrode, and is adapted to be implanted within a
second chamber of the heart. The first electrode assembly and the
second electrode assembly include an active fixation portion, to
which a movement assembly is coupled. In one embodiment, the
movement assembly includes an externally threaded portion which is
engaged with an internally threaded housing. In another embodiment,
the internally threaded portion comprises an insert disposed within
the lead.
[0023] In another embodiment, a bifurcated lead includes a main
lead body which is adapted to carry signals to and from the heart.
The main body extends to a first electrode assembly which has a
first electrode and a second electrode, and is adapted to be
implanted within a first chamber of the heart. The body also
extends to a second electrode assembly which has a third electrode
and a fourth electrode, and is adapted to be implanted within a
second chamber of the heart. The lead is coupled with a signal
generator which is adapted for producing pulses to apply to the
heart.
[0024] According to one embodiment of the present invention, there
is provided a body-implantable lead assembly comprising a lead, one
end of the lead being adapted to be connected to electrical supply
for providing or receiving electrical pulses. The other end of the
lead comprises a distal tip which is adapted to be connected to
tissue of a living body. The lead is characterized by having either
a) a porous electrode at the base of the helix and/or b) an
insulating coating over a portion of the helix so that the
impedance is increased for the helix as compared to a helix of the
same size and materials without an insulating coating. The lead
also has an increased impedance or a high impedance which can act
to extend the life of the battery. The high or at least the
increased impedance may be effected in any of an number of ways,
including, but not limited to one or more of the following
structures: 1) a fully insulated tissue-engaging tip with an
electrode at the base of the insulated tip, 2) a partially
insulated (only a portion of the surface area of the engaging tip
being insulated), 3) a mesh or screen of material at the distal end
of the lead, at the base of an extended engaging tip (whether a
fixed or retractable tip), 4) the selection of materials in the
composition of the mesh and/or tip which provide higher impedance,
5) the partial insulative coating of a mesh or screen to increase
its impedance, and 6) combinations of any of these features. There
may be various constructions to effect the high impedance,
including the use of helical tips with smaller surface areas (e.g.,
somewhat shorter or thinner tips). There may also be a sheath of
material inert to body materials and fluids and at least one
conductor extending through the lead body. The use of these various
constructions in the tip also allows for providing the discharge
from the tip in a more highly resolved location or area in the
tip.
[0025] According to another embodiment of the present invention,
there is provided a body-implantable lead assembly comprising a
lead, one end being adapted to be connected to electrical supply
for providing or receiving electrical pulses. The lead further
comprises a distal tip which is adapted to be connected to tissue
of a living body. The lead also has a high impedance to extend the
life of the battery. There may be various constructions to effect
the high impedance. There may also be a sheath of material at the
distal end of the lead assembly, with the sheath being inert to
body materials and fluids and at least one conductor extending
through the lead body.
[0026] The distal tip electrode is adapted, for example, for
implantation proximate to the heart while connected with a system
for monitoring or stimulating cardiac activity. The distal tip
electrode includes an electrode tip (preferably with only a
percentage of its entire surface area being electrically
conductively exposed [only a portion of the surface is insulated]
to increase its impedance), preferably a mesh screen disposed at a
distal end of the electrode tip, a fixation helix disposed within
the electrode tip, and a helix guiding mechanism. The mesh screen
preferably is electrically active (conductive as well as active),
and the area of the mesh screen and the percentage of electrically
exposed surface area of the electrode tip can be changed to control
electrical properties. Further, the mesh screen can entirely cover
an end surface of the electrode tip, or a portion of the end
surface in the form of an annular ring. In one embodiment, the
helix guiding mechanism includes a hole punctured within the mesh
screen. Alternatively, the helix guiding mechanism can include a
guiding bar disposed transverse to a radial axis of the electrode.
The helix is retractable, and is in contact with a movement
mechanism. The movement mechanism provides for retracting the
helix, such as during travel of the electrode tip through veins.
The helix is aligned with the radial axis of the electrode and
travels through the guiding mechanism. The mesh may be tightly
woven or constructed so that there are effectively no openings, or
the mesh can be controlled to provide controlled porosity, or
controlled flow through the mesh.
[0027] In another embodiment, the electrode tip includes a mesh
screen forming a protuberance on the end surface of the electrode
tip. The protuberance is axially aligned with the radial axis of
the electrode. The helix travels around the protuberance as it
passes through the mesh while traveling to attach to tissue within
the heart. The helix also travels around the protuberance as it is
retracted away from the tissue within the heart. If the mesh screen
is insulated around the protuberance, then a high impedance tip is
created. Advantageously, the protuberance allows for better
attachment to the cardiac tissue without having the electrode tip
penetrating therethrough.
[0028] Additionally, a distal tip electrode is provided including
an electrode tip, a mesh screen disposed at a distal end of the
electrode tip, a fixation helix disposed within the electrode tip,
and a helix guiding mechanism. The electrode tip further may
include a piston for moving the helix. The piston further may
include a slot for receiving a bladed or fixation stylet. When
engaged and rotated, the piston provides movement to the helix. The
base provides a mechanical stop for the helix and piston when
retracted back in to the electrode tip.
[0029] In another embodiment, the distal tip assembly is adapted
for implantation proximate to the heart while connected with a
system for monitoring or stimulating cardiac activity. A fixation
helix/piston assembly is housed by an electrode collar, housing,
and base assembly. Attached to the proximal end of the helix is a
piston which includes a proximal slot for receiving a bladed or
fixation stylet. When a stylet is engaged in the slot and rotated,
the piston provides movement to the helix. Depending on the
embodiment, the fixation helix/piston assembly may be electrically
active or inactive. The electrode collar, housing, and base all
house the fixation helix/piston assembly. The proximal end of the
electrode collar is attached to the distal end of the housing.
Furthermore, the proximal end of the housing is attached to the
distal end of the base, and the proximal end of the base is
directly attached to the conductor coils of the lead.
[0030] A mesh screen may be attached to the distal tip of the
electrode collar. The mesh screen, in another embodiment, is
electrically active and serves as the electrode on the distal tip
assembly. The tip may then be fully insulated to increase the
impedance of the tip or may be partially insulated (with
preselected areas of the helix tip being insulated and other areas
being non-insulated) to adjust the impedance of the tip to the
specific or optimal levels desired. The area of the mesh screen can
be modified to cover differing portions of the end surface of the
distal tip assembly to control electrical properties of the lead.
The fixation helix travels through a guiding mechanism, where the
guiding mechanism allows the fixation helix to be extended and
retracted. In one embodiment, the helix guiding mechanism includes
a hole formed within the mesh screen. Alternatively, the helix
guiding mechanism can include a guiding bar disposed transverse to
a radial axis of the electrode collar. The mesh screen and/or
guiding bar also serve as a full extension stop when the helix is
fully extended. The base serves as a stop when the fixation
helix/piston assembly is fully retracted.
[0031] In yet another embodiment, the electrode uses a partially
insulated fixation helix to provide a relatively high pacing
impedance electrode. The fixation helix is insulated using
insulating coatings over a portion of the fixation helix.
[0032] The above lead embodiments are also incorporated into a
system, wherein the lead is operatively coupled with a pulse
generator. Signals or pacing pulses produced by the pulse generator
which are sent and/or received from the electrodes. The pulse
generator can be programmed and the electronics system includes a
delay portion so that the timing between a pulse at a first
electrode and a pulse at a second electrode.
[0033] The provided electrode tip supplies a retractable helix and
a mesh screen which advantageously allows for sufficient tissue
in-growth. The guide mechanism provides a convenient way to direct
the rotation of the helix. A further advantage of the electrode tip
is the provided mechanical stop. The mechanical stop aids in
preventing over-retraction of the helix during the installation or
removal of the electrode tip.
[0034] The electrodes are attached to the endocardium so that the
electrical signals received from the heart are better than with
floating, unattached electrodes. In addition, the active fixation
electrodes can be placed into a recess so that mechanisms, such as
a helical hook, used to attach the electrode to the wall of the
heart will not catch undesired tissue. A further advantage is that
only one lead needs to be placed into the patient to do both
sensing and pacing of all types. The lead can also be shaped to
facilitate placement of the lead.
[0035] A further advantage is that the bi-polar single pass lead
allows for two chambers of the heart to be paced and/or sensed,
while only one lead is implanted within the patient. This assists
in preventing added stress and expense for the patient. In
addition, the active fixation element will not hook nor snag tissue
when it is retracted within the lead. The active fixation element
does not require the use of a stylet, since the terminal pins are
used to extend and retract the active fixation element. An
additional benefit is that only one lead is placed into the patient
for both sensing and pacing, thereby eliminating the need for
placement of the second lead.
[0036] Yet another advantage is that the extendable portion of the
lead is mechanically isolated from the main lead body so that the
helical screw or hook can turn independently of the lead body. In
other words, the body of the lead does not need to be turned to
affix the helical screw to the heart.
[0037] These and other embodiments, aspects, advantages, and
features of the present invention will be set forth in part in the
description which follows, and in part will become apparent to
those skilled in the art by reference to the following description
of the invention and referenced drawings or by practice of the
invention. The aspects, advantages, and features of the invention
are realized and attained by means of the instrumentalities,
procedures, and combinations particularly pointed out in the
appended claims and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a schematic view of a single-pass lead with
electrodes for pacing at multiple sites within a single chamber of
the heart.
[0039] FIG. 2 is a schematic view of a single-pass lead with
electrodes for pacing at multiple sites within a single chamber of
the heart, positioned within the right ventricle of the heart.
[0040] FIG. 3 is a block diagram illustrating a system for
delivering signals to the heart constructed in accordance with one
embodiment of the present invention.
[0041] FIG. 4 is a first perspective view illustrating a
single-pass lead constructed in accordance with one embodiment of
the present invention.
[0042] FIG. 5 is a second perspective view illustrating a
single-pass lead constructed in accordance with one embodiment of
the present invention.
[0043] FIG. 6 is a cross-section view taken along 6-6 of FIG. 4
illustrating a single-pass lead constructed in accordance with
another embodiment of the present invention.
[0044] FIG. 7 is a cross-section view illustrating a portion of a
single-pass lead constructed in accordance with yet another
embodiment of the present invention.
[0045] FIG. 8 is a cross-section view illustrating a portion of a
single-pass lead constructed in accordance with one embodiment of
the present invention.
[0046] FIG. 9 is a cross-section view illustrating a portion of a
single-pass lead constructed in accordance with one embodiment of
the present invention.
[0047] FIG. 10 is a cross-section view illustrating a portion of a
single-pass lead constructed in accordance with one embodiment of
the present invention.
[0048] FIG. 11 is a perspective view illustrating a single-pass
lead constructed in accordance with one embodiment of the present
invention.
[0049] FIG. 12 is a perspective view illustrating a single-pass
lead constructed in accordance with one embodiment of the present
invention.
[0050] FIG. 13 is a perspective view illustrating a single-pass
lead constructed in accordance with another embodiment of the
present invention.
[0051] FIG. 14 is a side view of the single-pass endocardial lead
for sensing and electrically stimulating the heart, positioned
within the right ventricle and right atrium of the heart,
constructed in accordance with one embodiment of the present
invention.
[0052] FIG. 15A is a side view of a single-pass lead for sensing
and electrically stimulating the heart constructed in accordance
with one embodiment of the present invention.
[0053] FIG. 15B is a side view of a single-pass lead for sensing
and electrically stimulating the heart constructed in accordance
with one embodiment of the present invention.
[0054] FIG. 16 is a side view of a single-pass endocardial lead for
sensing and electrically stimulating the heart constructed in
accordance with one embodiment of the present invention.
[0055] FIG. 17A is a side view of a single-pass endocardial lead
for sensing and electrically stimulating the heart constructed in
accordance with one embodiment of the present invention.
[0056] FIG. 17B is a side view of stylet for use with the
endocardial lead.
[0057] FIG. 18 is a perspective view of the atrial electrode
portion of the lead showing a passive attachment element for
attachment to the atrial wall of the heart.
[0058] FIG. 19 is a perspective view of another embodiment of the
electrode for passive attachment to the atrial wall of the
heart.
[0059] FIG. 20 is a perspective view of another embodiment of the
electrode for passive attachment to the atrial wall of the
heart.
[0060] FIG. 21 is a perspective view of another embodiment of the
electrode for passive attachment to the atrial wall of the
heart.
[0061] FIG. 22 is a perspective view of another embodiment of the
electrode for passive attachment to the atrial wall of the
heart.
[0062] FIG. 23 is a perspective view of another embodiment of the
electrode for passive attachment to the atrial wall of the
heart.
[0063] FIG. 24 is a perspective view of another embodiment of the
electrode for passive attachment to the atrial wall of the
heart.
[0064] FIG. 25 is a side view of a portion of a lead body showing
an electrode for passive attachment to the atrial wall of the
heart.
[0065] FIG. 26 is a side view of a single-pass endocardial lead for
electrically stimulating the heart constructed in accordance with
another embodiment of the present invention.
[0066] FIG. 27 is a side view of a single-pass endocardial lead
implanted within the heart constructed in accordance with another
embodiment of the present invention.
[0067] FIG. 28 is a side view of a single-pass endocardial lead for
multi-site pacing during insertion with a first atrial leg straight
and one atrial leg withdrawn into the lead body constructed in
accordance with one embodiment of the present invention.
[0068] FIG. 29 is a side view of a single-pass endocardial lead for
multi-site pacing during insertion with a first atrial leg formed
into atrial `J` after withdrawal of stylet and one atrial leg
withdrawn into the lead body constructed in accordance with one
embodiment of the present invention.
[0069] FIG. 30 is a side view of a single-pass endocardial lead for
multi-site pacing during insertion with both atrial legs formed
into a `J` constructed in accordance with one embodiment of the
present invention.
[0070] FIG. 31 is a side view of a single-pass endocardial lead for
multi-site pacing during insertion with one atrial leg formed into
a `J` and one leg straight constructed in accordance with one
embodiment of the present invention.
[0071] FIG. 32 is a side view of a single-pass endocardial lead for
multi-site pacing during insertion with two atrial legs formed into
a `J` and one leg straight constructed in accordance with one
embodiment of the present invention.
[0072] FIG. 33 is a side view of a single-pass endocardial lead for
multi-site pacing constructed in accordance with one embodiment of
the present invention.
[0073] FIG. 34 is a side view of a single-pass endocardial lead for
multi-site pacing constructed in accordance with one embodiment of
the present invention.
[0074] FIG. 35 is a side view of a single-pass endocardial lead for
multi-site pacing constructed in accordance with one embodiment of
the present invention.
[0075] FIG. 36 is a side elevational view illustrating a
single-pass lead constructed in accordance with another embodiment
of the present invention.
[0076] FIG. 37 is a cross-section view illustrating a single-pass
lead constructed in accordance with one embodiment of the present
invention.
[0077] FIG. 38 is a cross-section view illustrating a single-pass
lead constructed in accordance with one embodiment of the present
invention.
[0078] FIG. 39 is a cross-section view illustrating a single-pass
lead constructed in accordance with one embodiment of the present
invention.
[0079] FIG. 40 is a perspective view illustrating a movement
assembly of the lead constructed in accordance with one embodiment
of the present invention.
[0080] FIG. 41 is a first side elevational view illustrating a lead
constructed in accordance with one embodiment of the present
invention.
[0081] FIG. 42A is a cross-sectional view of an electrode tip of a
lead for monitoring and stimulating the heart constructed in
accordance with one embodiment of the present invention.
[0082] FIG. 42B is an end view of the electrode tip of the lead
shown in FIG. 42A.
[0083] FIG. 43A is a cross-sectional view of an electrode tip of a
lead for monitoring and stimulating the heart constructed in
accordance with one embodiment of the present invention.
[0084] FIG. 43B is an end view of the electrode tip of the lead
shown in FIG. 43A.
[0085] FIG. 44A is a cross-sectional view of an electrode tip of a
lead for monitoring and stimulating the heart constructed in
accordance with one embodiment of the present invention
[0086] FIG. 44B is an end view of the electrode tip of the lead
shown in FIG. 44A.
[0087] FIG. 45A is a cross-sectional view of an electrode tip of a
lead for monitoring and stimulating the heart constructed in
accordance with one embodiment of the present invention
[0088] FIG. 45B is an end view of the electrode tip of the lead
shown in FIG. 45A.
[0089] FIG. 46 shows a partially insulated helical tip constructed
in accordance with one embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0090] In the following detailed description, reference is made to
the accompanying drawings which form a part hereof, and in which is
shown by way of illustration specific embodiments in which the
invention may be practiced. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
the invention, and it is to be understood that other embodiments
may be utilized and that structural changes may be made without
departing from the scope of the present invention. Therefore, the
following detailed description is not to be taken in a limiting
sense, and the scope of the present invention is defined by the
appended claims and their equivalents.
[0091] FIG. 1 illustrates a schematic view of a system 100 for
delivering electrical pulses or signals to stimulate and/or pace
the heart. The system for delivering pulses 100 includes a pulse
generator 102 and a lead 110, where the lead 110 includes a
connector end or connector terminal 120 and extends to a distal end
130. The distal end 130 of the lead 110 includes at least two
electrodes 132 and 134, which comprise either unipolar or bipolar
type electrodes. For bipolar type electrodes, the electrode 132
would be part of a bipolar set including two electrodes. Similarly,
the electrode 134, if bipolar, would be part of a set. The lead 110
includes a lead body 112 which, in one embodiment, is comprised of
a tubing material formed of a biocompatible polymer suitable for
implementation within the human body. Preferably, the tubing is
made from a silicon rubber type polymer. The lead body 110 includes
at least one lumen (not shown) which carries each electrical
conductor from the connector terminal 120 to the electrodes 132 and
134. The electrical conductors carry current and pulses between the
pulse generator 102 and the electrodes 132 and 134 located in the
distal end 130 of the lead 110.
[0092] The pulse generator 102 includes a source of power as well
as an electronic circuitry portion 104. The pulse generator is a
battery-powered device which generates a series of timed electrical
discharges or pulses used to initiate depolarization of excitable
cardiac tissue. The pulses are delivered to the cardiac tissue and
operate as an artificial pulse formation source when used to pace
the heart. The pulse generator is generally implanted into a
subcutaneous pocket made in the wall of the chest. Alternatively,
the pulse generator 102 can be placed in a subcutaneous pocket made
in the abdomen, or other locations.
[0093] The lead 110 is connected to the pulse generator 102 by the
connector terminal 120. The lead 110 travels from the pulse
generator 102 into a major vein, and the distal end 130 of the lead
is placed inside the heart. The lead 110 is placed underneath the
skin and travels to the shoulder and neck where it enters a major
vein such as the subclavian vein. The distal end 130 of the lead
110 is placed directly within the endocardium. In one embodiment,
the lead 110 will be actively or passively affixed to the
endocardial wall of a chamber of the heart, as will be further
described below.
[0094] As can be seen in FIG. 1, the distal end 130 of the lead 110
is curved, where the electrodes 132, 134 are disposed along the
curve 136. The curve 136 is sized and positioned to allow the
electrodes 132 and 134 to be positioned within one chamber of the
heart. In FIG. 1, the chamber selected for implantation is the
right atrium 150. The lead 110 will include a lumen into which a
stylet may be placed. The stylet is basically a wire that
straightens out the lead while it is being placed within the heart.
By removing the stylet, the lead will take on its natural or
manufactured shape, which in this case, is a curved distal end 130.
The curve within the distal end 130 of the lead 110 has a small
enough radius such that it fits within the right atrium 150 of the
heart.
[0095] The electronics 104 associated with the pulse generator 102
include a delay circuit which allows the pulse delivered to one of
the electrodes 132 or 134 to be delayed with respect to the pulse
delivered to the other of the electrodes. This delay can be either
a delay of zero or it can be a delay that can be programmed to be
any desired length of time. The delay portion of the electronics
104 typically will include a clock source. The clock source will
produce a clocking pulse that can be used to produce the delay. In
other words, if a delay of so many clocking signals equals the
appropriate or selected delay, the pulse generator 102 and the
electronics 104 will initially deliver a pulse to a first
electrode, then the electronics will count the selected number of
pulses from a clock signal and then deliver a pulse to the other of
the electrodes 132 and 134.
[0096] Also shown in FIG. 1 is a programmer 106. The programmer is
typically an external-type programmer that can be used to program
many of the parameters of the electronics 104 and other parameters
of the pulse generator 102. One of the parameters that can be
programmed includes the length of delay between the pulse to the
electrode 132 and the pulse to the electrode 134. It should be
noted that the length of delay can also be set so that it's
nonexistent. In other words, if a delay of zero is used, the pulse
generator 102 and the electronics associated with the pulse
generator 104 will send pacing pulses to the electrode 132 and the
electrode 134 at substantially the same time. The programmer can
also be an external handheld-type programmer which a patient might
be able to use. The other type of programmer might be one that a
physician would have in his or her office which can be used to
program various parameters associated with the pulses produced by
the pulse generator. The programmer 106 will typically have a
feature which will allow readout of the status of the pulse
generator.
[0097] FIG. 2 is a schematic of a single-pass endocardial lead for
electrically stimulating multiple sites within a single chamber of
the heart which is positioned within the right ventricle of the
heart, where the lead 110 is shown as having a distal end 130. The
distal end 130 features includes a first electrode 132 and a second
electrode 134. In FIG. 2, the distal end 130 of the lead body 110
passes through the right atrium and is positioned within the right
ventricle 160 of the heart. Again, as before, the electrodes 132
and 134 may be unipolar or may be bipolar. In the instance when
each of the electrodes 132 and 134 are bipolar, there is an
additional electrode associated with each of the electrodes 132 and
134. Alternatively, in another embodiment, one of the electrodes
132 is unipolar and one of the electrodes 134 is bipolar.
[0098] The electrodes 134 and 132 are positioned along the curve
136 in the distal end 130 so that electrical stimulation or pulse
generation can be delivered to two sites within a single chamber of
the heart, namely, the right ventricle 160. The curve 136 is sized
and positioned to be received within the ventricle, where the
electrodes 132 and 134 are in contact with the wall of the heart,
as shown. The electrodes 132 and 134 are attached to the
endocardial wall of the heart with either passive fixation or
active fixation, as will be further described below. The shape of
the curve 136 associated with the distal end may be varied to
achieve a selected placement of the electrodes 134 and 132 within
the right ventricle of the heart. In addition, the distance between
the first electrode 132 and second electrode 134 can also be
changed for various applications for multi-site pacing within the
right ventricle. The pulse generator and electronics as well as the
connector end or terminal end 120 of the lead 110 and the
programmer 106, are all the same in FIG. 1 as in FIG. 2 and,
therefore, were not shown here.
[0099] FIG. 3 illustrates another embodiment of the present
invention, showing a lead 170 adapted for delivering electrical
pulses to stimulate the heart. The lead 170 has a lead body 172
extending from a proximal end 174, which is adapted to connect with
equipment which supplies electrical pulses, to a distal end 176
which is adapted to be inserted into the heart. The lead body 172
includes an intermediate portion 178 which includes quad-lumen
tubing as will be further discussed below. Proximate to the distal
end 176 is a first electrode tip 180 including a first electrode
assembly 182. A second electrode tip 184 is also provided, as
discussed below, which includes a second electrode assembly
186.
[0100] Proximate to the proximal end 174 of the lead 170 are
connector terminals 188. The connector terminals 188 electrically
connect the various electrodes and conductors within the lead 170
to a pulse generator and signal sensor 190. The pulse sensor and
generator 190 contains electronics to sense various electrical
signals of the heart and also produce current pulses for delivery
to the heart, depending on the type of lead 170 used. The pulse
sensor and generator 190 also contains electronics and software
necessary to detect certain types of arrhythmias and to correct for
them. The lead terminal connector 188 provides for the electrical
connection between the lead 170 and the pulse generator 190.
[0101] To implant the lead 170 within a patient, a single sheath
can be used for the single electrode 170 to implant the lead 170
within the heart, which prevents unnecessary trauma to the patient.
The first electrode assembly 182 is advanced into the ventricular
portion 192 of the heart 194. The first electrode assembly 182 is
secured to the wall of the heart 194 using either passive or active
fixation. In one embodiment, the active fixation elements are
advanced using the terminal pins (FIG. 4). In another embodiment,
the active fixation elements are advanced using a stylet, as
discussed further below.
[0102] The second electrode assembly 186 is advanced, in one
embodiment, into the atrium portion 196 of the heart 194 using a
straight stylet (not shown). To secure the second electrode
assembly 186 into the atrium, the straight stylet is removed and a
J-shaped stylet (not shown) is insert into the second electrode
assembly 186 and the second electrode assembly 186 takes on the
J-shape. Alternatively, the second electrode assembly 186 is placed
within the atrium portion 196 using a J-shaped lead, as shown and
discussed below in FIGS. 11 and 12. Similar to the first electrode
assembly, the second electrode assembly 186 is secured to the heart
194 using either passive or active fixation.
[0103] FIG. 4 illustrates the lead of FIG. 3 in greater detail. The
lead 200 extends from a proximal end 202 to a distal end 204 and
includes a first and second connector terminal 280, 282 near the
proximal end 202. The lead 200 also includes a lead body 220, a
first electrode assembly 210, and a second electrode assembly 212,
as will be further described below. The connector terminals 280,
282 electrically connect the various electrodes and conductors with
the lead body to a pulse sensor and generator 190 (FIG. 3). The
pulse sensor and generator 190 (FIG. 3) contain electronics to
sense various pulses of the heart and also produce pulsing signals
for delivery to the heart. The pulse sensor and generator 190 also
contain electronics and software necessary to detect certain types
of arrhythmias and to correct for them. Physicians are able to
program the pulse sensor and generator to correct a particular
arrhythmia that the patient may have. Numerous types of connector
terminals which connect to a pulse sensing and generating unit can
be used. In one embodiment, the connector terminals 280, 282 are
designed to conform with International Standards.
[0104] The lead body 220, in one embodiment, is formed from a
polymer biocompatible material, and can include tubing made from a
silicone rubber polymer. The lead body 220 extends from the
proximal end 202 of the lead 200 to the distal end 204 of the lead
200, and has an intermediate portion 206 therebetween. Near the
proximal end 202 of the lead body 220, the lead body 220 has at
least two IS1 terminal legs, including a first terminal leg 230 and
a second terminal leg 232.
[0105] At the proximal end 202 of the first terminal leg 230 and
the second terminal leg 232 are terminal pins 234, 236 which can be
operatively coupled with a pulse sensor and signal generator 190,
as discussed above. In one embodiment, the terminal pins 234, 236
are used to rotate the active fixation device, discussed further
below. In another embodiment, a stylet driven mechanism is used to
rotate the active fixation device. The first terminal leg 230 and
the second terminal leg 232 extend from the terminal pins 234, 236
of the proximal end 202 of the lead 200 to the intermediate portion
206 of the lead 200, where the first terminal leg 230 and the
second terminal leg 232 are coupled with the intermediate portion
206 at a proximal bifurcation point 208. In one embodiment, the
first terminal leg 230 and the second terminal leg 232 are coupled
with the intermediate portion 206 with a yoke 240 which operates as
a strain relief. The yoke 240, in one embodiment, comprises a
sheath for covering at least portions of the first and second
terminal legs 230, 232 and the intermediate portion 206, where the
sheath can be attached using medical adhesive or other attachment
methods. In another embodiment, the yoke 240 is over-molded
encompassing the intermediate portion 206 and the first and second
terminal legs 230, 232.
[0106] The intermediate portion 206 of the lead body 220, as shown
in FIG. 6, is comprised of quad-lumen tubing 242, which in one
embodiment comprises PTFE insulation. Disposed within each lumen of
the quad-lumen tubing 242 is a conductor 246, consisting of either
a cable or a coil. Referring again to FIGS. 4 and 5, the
intermediate portion 206 extends from the proximal bifurcation
point 208 to a distal bifurcation point 209. At the distal
bifurcation point 209, in one embodiment, the intermediate portion
206 transitions into two bi-lumen tubes 250, including a first
electrode leg 252 and a second electrode leg 254. The first
electrode leg 252, in one embodiment, is shorter in length than the
second electrode leg 254, where the first electrode leg 252 is for
implantation into an atrium (not shown) and the second electrode
leg 254 is for implantation within the ventricle (not shown). In
another embodiment, the first electrode leg 252 and the second
electrode leg 254 are coupled with the intermediate portion 206
with a yoke 241, similar to the yoke 240 discussed above. The first
electrode leg 252 and the second electrode leg 254 each extend to
the first electrode assembly 210 and the second electrode assembly
212, respectively.
[0107] In one embodiment, as shown in FIG. 4, the first electrode
assembly 210 and the second electrode assembly 212 are both
bipolar. In another embodiment, as shown in FIG. 5, the first
electrode assembly 210 is bipolar and the second electrode assembly
212 is unipolar. In yet another embodiment, similar to FIG. 5, the
first electrode assembly 210 is unipolar and the second electrode
assembly 212 is bipolar. To form a unipolar electrode assembly,
only a single conductor, discussed further below, is provided
within the electrode assembly, and a single electrode is provided.
The electrode, for either the bipolar or unipolar embodiments of
the first and second electrode assemblies 210, 212, comprises a
singular electrode or a combination of electrodes of the following:
a tip electrode, a ring electrode, a defibrillator coil, or their
equivalents. The various electrodes can be used for pacing,
sensing, defibrillating, or a combination of the same.
[0108] In another embodiment, a first conductor set is disposed
within the first electrode leg 252 and comprises a coil and a cable
which terminate in a first pacing tip 256 and a first pacing ring
258, respectively. Similarly, as shown in FIG. 4, a second
conductor set is disposed within the second electrode leg 254 and
comprises a coil and a cable which terminate in a second pacing tip
260 and a second pacing ring 262, respectively. For the embodiment
shown in FIG. 5, the second conductor set comprises only a second
pacing tip 260, thereby forming a unipolar leg.
[0109] The first electrode leg 252, in one embodiment, has a
semi-circular cross-section, as shown in FIG. 7. Similarly, the
second electrode leg 254, in another configuration, also has a
semi-circular cross-section. When placed adjacent to one another,
the first electrode leg 252 and the second electrode leg 254 form a
circular cross-section, as shown in FIG. 9. In one configuration,
medical adhesive or other equivalents 266, including dissolvable
substances such as mannitol, are disposed between the first
electrode leg 252 and the second electrode leg 254 to aid in the
installation of the lead 200 within a patient.
[0110] Alternatively, the first electrode leg 252 has an elliptical
cross-section, as shown in FIG. 8. Similarly, the second electrode
leg 254 has an elliptical cross-section. When placed adjacent to
one another, the first electrode leg 252 and the second electrode
leg 254 easily fit together, as shown in FIG. 10. In another
embodiment, medical adhesive or other equivalents 266, including
dissolvable substances such as mannitol, are disposed between the
first electrode leg 252 and the second electrode leg 254, as shown
in FIG. 10, to assist in the installation of the lead 200 within a
patient. The cross-section of the first and second electrode legs
252, 254 are not limited to the above and can have other
cross-sections.
[0111] FIG. 11 illustrates another embodiment showing a lead 300.
The lead 300 extends from a proximal end 302 to a distal end 304
and comprises a first and second connector terminal 380, 382 near
the proximal end 302. The lead 300 also includes a lead body 320, a
first electrode assembly 310, and a second electrode assembly 312.
Near the proximal end 302 of the lead body 320, the lead body 320
has at least two IS1 terminal legs, including a first terminal leg
330 and a second terminal leg 332.
[0112] At a distal bifurcation point 309, an intermediate portion
306 of the lead body 320 transitions into two bitumen tubes 350,
including a first electrode leg 352 and a second electrode leg 354.
The first electrode leg 352 and the second electrode leg 354 each
extend to the first electrode assembly 310 and the second electrode
assembly 312, respectively. A first conductor set is disposed
within the first electrode leg 352 and comprises, in one
embodiment, a coil and a cable which terminate in a first pacing
tip 356 and a first pacing ring 358, respectively. Similarly, a
second conductor set is disposed within the second electrode leg
354 and comprises, in another embodiment, a coil and a cable which
terminate in a second pacing tip 360 and a second pacing ring 362,
respectively. In another embodiment, as shown in FIG. 12, the first
conductor set and the second conductor set disposed within the
first electrode leg 352 and the second electrode leg 354,
respectively, terminate in a first pacing tip 356 and a first
defibrillator electrode 359 second pacing tip 360 and a second
defibrillator electrode 363.
[0113] The first electrode leg 352 and the second electrode leg
354, in one embodiment, comprise bipolar lead legs. In another
embodiment, the first electrode leg 352 is unipolar and the second
electrode leg 354 is bipolar (See FIG. 5). In yet another
embodiment, the first electrode leg 352 is bipolar and the second
electrode leg 354 is unipolar. The electrode, for either the
bipolar or unipolar embodiments of the first and second electrode
assemblies 310, 312, comprises a tip electrode, a ring electrode, a
defibrillator coil, or their equivalents. The various electrodes
can be interchanged and used for pacing, sensing, defibrillating,
or a combination of the same.
[0114] The second electrode leg 354, in one embodiment, has a
J-shape, which can have either passive or active fixation, as will
be further discussed below. Using a straight stylet (not shown) to
straighten the electrode leg 354 prior to implant, the second
electrode leg 354 is positioned within the right atrium of the
heart. As the stylet (not shown) is removed, the second electrode
leg 354 re-assumes the J-shape and becomes positioned within the
atrium of the heart. If a passive configuration is used, as further
discussed below (for example, FIG. 36), the distal end 355 of the
second electrode leg 354 becomes embedded within the wall of the
heart as tissue in-growth begins. If an active fixation
configuration is used, the distal end 355 of the second electrode
leg 354 is positioned adjacent the wall of the heart. The fixation
helix is advanced so that it screws into the wall of the heart and
the second electrode leg 312 is engaged. The discussions of leads
for multi-site pacing and/or passive and active fixation devices in
related U.S. Pat. Nos. 6,141,594 and 6,085,119 are hereby
incorporated by reference in their entirety.
[0115] FIG. 13 shows another embodiment of the invention. In this
configuration, the atrial lead 390 and/or the ventricle lead 396
each have an active fixation element 394, as further described
below, for fixating the leads 390, 396 to the endocardial wall of a
heart. The active fixation element 394 is rotatable by terminal
pins 398, and the active fixation element 394 is not retractable.
Alternatively, the active fixation element 394 can be rotated using
other manners, for example, a stylet. To protect the patient during
implantation or to prevent snagging of the fixation element 394,
the active fixation element 394 of the atrial lead 390 and/or the
ventricle lead 396 is covered with a dissolvable coating 397, such
as mannitol. The dissolvable coating 397 remains intact during
insertion of the leads 390, 396 through the subclavian vein and
into the heart. The dissolvable coating 397 prevents the active
fixation element 394 from catching tissue in the vein during
insertion. Once implanted, the coating 397 dissolves to expose
active fixation element 394 and allow it to be turned into the
atrial wall of the heart. The dissolvable coating 397 is depicted
by a dotted line enclosure around the active fixation element
394.
[0116] FIGS. 14-27 illustrate another embodiment of a lead coupled
with a system and the heart, wherein a portion of the lead body is
curved and at least one electrode is coupled with the curved
portion 450 of the lead 400. The lead 400 and, more specifically,
the distal end 430 of the lead 400 positioned within a heart 402.
The heart 402 includes four chambers which are the right atrium
404, the right ventricle 405, the left ventricle 406 and the left
atrium 407. Also shown in FIG. 14 is the superior vena cava
408.
[0117] The distal end 430 of the lead 400, in one embodiment, is
positioned within the superior vena cava 408, the right atrium 404
and the right ventricle 405. The curved portion 450 of the lead 400
positions the atrial electrode 461 on the curved portion 450 or
biased section closer to the wall of the heart 402 in the right
atrium 404. This enhances electrical performance as electrode 461
will be closer to the portion of the heart 402, namely the right
atrium 404, where the signal will pass. In addition, the electrode
461 is positioned closer to the wall of the right atrium 404 such
that passive fixation can occur. If passive fixation is achieved,
the distal end 430 of the lead 400 will be more stably fixed within
the heart 402. Even if the passive fixation is not achieved, the
electrode 161 will be biased closer to the wall of the right atrium
202 so as to enhance the electrical sensing capability of that
electrode. In another embodiment, a plurality of tines 480 are
coupled near the electrode 454. The plurality of tines 480 aid in
positioning the distal end 430 in the right ventricle 405 at the
time of lead insertion. At the time of lead implantation, the
distal electrode 454 is generally positioned in the right
ventricle. The tines 480 are used to engage tissue structures which
line the endocardial surface of the ventricle 405 and then hold the
lead 400 in place after it is implanted. Fibrous tissue grows over
these tines 480 over time to produce an attachment to the wall of
the heart in the right ventricle 405 and further secure the lead
400 within the heart 402.
[0118] FIG. 14 also shows the lead terminal connector 410 and its
connection into the pulse generator 440. The lead terminal
connector 410 makes electrical connection with a signal
processing/therapy circuit 442 which in turn is electrically
connected to a microcontroller 444. Within the microcontroller 444
is a synchronizer 446. The signal processing/therapy circuit 442
determines the type of therapy that should be delivered to the
heart 402. The microcontroller 444 controls the delivery of the
therapy to the heart 402 through the synchronizer 446. The
synchronizer 446 times the delivery of the appropriate signal to
the heart 402.
[0119] FIG. 15A shows the lead 400 in greater detail. The lead 400
includes a connector terminal 410, a distal end 430, and an
intermediate portion 420 which interconnects the distal end 430 and
the connector terminal 410, and include conductive wires (not
shown) covered by a silicone rubber tubing which is biocompatible,
to form the lead body 422. The connector terminal 410 electrically
connects the various electrodes and conductors within the lead body
422 to the pulse generator 440 (discussed above). The distal end
430 is the portion of the lead 400 that includes electrodes and is
positioned within the heart during implantation. The lead body 422
is a tubing material formed from a biocompatible polymer for
implantation, and preferably tubing made from a silicone rubber
polymer. The silicone rubber polymer tubing contains several
electrical conductors (not shown). The electrical conductors are
made of a highly conductive, highly corrosion resistant
material.
[0120] After the lead 400 has been implanted, the distal end 430 of
the lead body 422 is situated predominantly within the heart 402
(FIG. 14). The distal end 130 of the lead body 422 includes a
curved or bias portion 450 and, in one embodiment, a straight
portion 460. After implantation, the curved portion 450 of the
electrode end 130, in one embodiment, will generally be located in
the right atrium of the heart 402 (FIG. 14), and the straight
portion 460 will be located in the right ventricle 405. It should
be noted that the lead 400 could also be implanted within the left
atrium 407 and the left ventricle 406 of the heart 402.
[0121] In one embodiment, the electrode end 130 of the lead 400 has
four electrodes 453, 454, 461, and 462. Referring again to FIG. 14,
two of the electrodes 461, 461 are located in the atrium 404, and
two of the electrodes 453, 454 are located in the ventricle 405.
The first electrode 454 is provided at the farthest distal end 455
of the lead 400 for the purpose of delivering ventricular pacing
therapy. The first electrode 454 is referred to as the RV
pace/sense tip. A second electrode 453 is located proximate and
proximal to electrode 454 and can be used as a counter electrode or
as an electrode for defibrillation therapy. The electrode 453 is
also known as the distal coil or the RV shock coil. The second
electrode 453, in one embodiment, is a shocking coil and is much
longer than the first electrode 454. The first electrode 454 and
the second electrode 453 can each be coupled with the heart wall
using either passive or active fixation.
[0122] A third electrode 461 is located at a more proximal
position, for example, along the curved portion 450, for the
purpose of delivering atrial pacing therapy. The third electrode
461 is also used for atrial sensing, and is referred to as the
atrial sense/pace electrode. In one embodiment, the third electrode
461 is passively attached to the atrial wall of the heart. The
atrial electrode 461 has a relatively small electrically active
surface area. The advantages of this small surface area are high
impedance for lower current drainage and a small lead cross section
for ease of venous access and transport through the subclavian
vein. A fourth electrode 462 is located proximate and proximal to
electrode 461 and can be used with electrode 461 for atrial
sensing/pacing and as counter to 453 as part of a defibrillation
therapy system. Electrodes 453 and 462, in one configuration, are
coils of a biocompatible metal or metal alloy such as, but not
restricted to, platinum, or platinum/iridium. The coils are
generally known as shocking coils and deliver large amounts of
energy used in cardioversion and defibrillation. Electrode 462 is
also referred to as the proximal coil or the SVC shock coil. The
SVC shock coil 462 is positioned in the upper atrium or the
superior vena cava.
[0123] FIG. 15B shows an alternative embodiment, which includes a
fifth electrode 463 on the lead 400. The electrode 463 is
positioned on the lead 400 adjacent the electrode 461 so that there
are two sensing electrodes, 461 and 463 in the atrium of the heart
to enhance the sensing capability of this lead. In one embodiment,
the electrode 461 comprises a porous tip electrode, as will be
further described below.
[0124] FIG. 16 shows a lead 500 used to treat a bradycardia
condition. The reference numerals associated with the lead 400
shown in FIGS. 14 and 15 which describe similar parts have been
used here for the purposes of simplicity. The lead 500 includes a
distal or RV pace sense tip 454, an atrial sense electrode 461, and
a ring electrode 510. The distal end 430 of the lead 500 includes a
straight portion 460 and a curved portion 450. The atrial sense
electrode 461 is positioned on the curved portion 450. The atrial
sense electrode 461 can also be provided with a means for passive
fixation to the wall of the heart. In this unipolar application,
the distal tip electrode 454 serves as the negative pole and the
pulse sensor and generator 440 serves as the positive pole when a
pacing pulse is delivered to the right ventricle of the heart. It
should be noted that this is not the only possible unipolar
arrangement, but that other unipolar arrangements are possible.
Furthermore, it should be noted that a bipolar arrangement may also
be used.
[0125] The electrode 461 on the curved portion is disposed such
that points out in the direction of the bias of the curved portion
450. In one embodiment, the electrode 461 is a ring electrode which
is disposed transverse to the lead body 422. In another embodiment,
the electrode 461 is on the larger radius of the curved portion 450
of the lead. This assures that the distance between the electrode
161 and the wall of the atrium 404 is minimized. This also
maximizes the possibility that the electrode 461 will become
passively fixed to the wall of the heart. In another embodiment,
the outside surface of the curved portion 450 of the lead 500 can
be textured to further enhance the passive fixation of the lead 461
to the heart.
[0126] In another embodiment, the ring electrode 510 is also placed
a selected distance from the electrode 461. The ring electrode 510
has the opposite polarity of the electrode 461. The ring electrode
510 is placed so that it is near the superior vena cava of the
heart when the lead 500 is placed in the heart. The electrodes 510
and 461 are used as a bipolar pair for sensing and pacing. The lead
500 is a single pass lead that can be used for both sensing a
bradycardia condition and treating it by pacing.
[0127] FIG. 17A illustrates an alternative form of a lead 520. A
conventional endocardial lead, having standard electrodes for the
RV tip 522, RV coil 524, and SVC coil 526 on a generally flexible
multi-lumen tubular body 530 is shown. Also included is an
additional SVC sense ring 528, and a curved shape 532 to hold the
sense ring into contact with the interior wall of the atrium or
superior vena cava. The lead 520 includes a curved portion 532
which in one embodiment, comprises a semi-flexible, semi-rigid arch
which is set in the lead to form a lateral protrusion. The curved
portion 532 mechanically biases the atrial sense ring into contact
with the inside wall of the atrium, or can be used to bias the lead
520 into contact with other parts of the heart wall. In one
embodiment, the curved portion 532 is spaced from the distal tip
534 of the lead 520 so as to be placed in the atrium when the lead
520 is in its use position with the RV tip 522 is in the ventricle.
In one embodiment, the atrial sense ring 528 is a small ring
electrode paced around the lead at the curved portion 532, in a
position where it will be in contact with the atrium when the lead
is placed in the heart. In another embodiment, the axis of the
sense ring 528 is aligned with the axis of the lead body 530. In
yet another embodiment, the axis of the sense ring 528 is co-axial
with the axis of the lead body 530. The advantage of the above
embodiments is that the atrial sense ring 528 is held in direct
contact with the atrial wall, which provides better signals for P
wave discrimination, as compared with lead designs which do not
ensure such direct contact.
[0128] The lead may be constructed generally according to known
techniques for multi-lumen intravascular electrode leads, an
example of which is shown and described in U.S. Pat. No. 4,603,705
to Speicher et al. The addition of atrial sense ring 528 will
require an additional conductor inside the body of the lead. For
this reason, the lead of FIG. 17A has four lumens 536, which are
seen in the section 550 drawn at the top of the FIG. 17A. The four
lumens 536 are the atrial ring lumen, the distal RV coil lumen, the
proximal SVC coil lumen, and the lumen for the stylet coil 540
(FIG. 17B) which may also serve as the conductor for the tip
electrode. A stylet coil 540, as illustrated in FIG. 17B, is
normally found in multi-lumen intravascular electrode leads,
consisting of a flexible metallic coil in one of the lumens serving
to receive a stylet as is generally known for facilitating
directional control of the lead during its placement in the heart.
The double-bend portion or curved portion 542 of the stylet coil
540 which forms the curved portion 532 may preferably be formed by
forming the bends in the stylet coil to take a `set` in which the
curved portion 532 is shaped as shown in FIG. 17A. The stylet coil
540 has sufficient flexibility to straighten, then return towards
the set shape after removal of the stylet.
[0129] In one embodiment, the distance 548 of the offset of the
curved portion 532 as indicated in FIG. 17A ranges from 1 to 3
centimeters. The length or axial extent 546 of atrial sense ring
528, in one embodiment, as indicated in FIG. 17A is 0.5 to 3.0
millimeters. The axial distance 547, in another embodiment, of
atrial sense ring 528 from the SVC coil 526 as indicated in FIG.
17A is 0.5 to 3.0 centimeters.
[0130] FIGS. 18-25 further detail certain elements of the passive
fixation single pass electrode used for an electrode to be disposed
along the curved portion. FIG. 11 shows a conductive ring made of a
highly conductive, and highly corrosion resistant, material such as
an alloy of platinum-iridium. The ring 552 includes a small porous
tip electrode 554. The ring 552 is electrically insulated from body
fluids. The porous tip electrode is electrically active and in
contact with body fluids and tissue. The active porous tip
electrode 552 includes a screen of porous conductive material such
as the alloy of platinum and iridium. Over time, the tissue
encapsulation grows into the screen made of a platinum-iridium
alloy to attach the electrode or electrodes to the endocardial wall
of the heart. The ring 552, in one embodiment, has a nominal radius
of 0.04 inches (1 mm). The advantage of this small radius is ease
of venous access and high impedance for conserving pacing
energy.
[0131] FIG. 19 shows another passive fixation electrode. FIG. 19
shows a conductive ring 560 made of a highly corrosion-resistant
material such as an alloy of platinum and iridium, and in one
embodiment is electrically insulated from body fluids. The ring
includes two small porous tip electrodes 556 and 558, which are
electrically active and in contact with body fluids. The active
porous tip electrodes 556 and 558 each include a screen of porous
conductive material made of the highly corrosion-resistant alloy of
platinum and iridium. Tissue encapsulation grows into the screen on
the tips 556 and 558 to attach the electrode to the endocardial
wall of the heart.
[0132] FIG. 20 shows another passive fixation element associated
with the curved portion of the lead. A conductive ring 562 made of
a highly corrosion-resistant material such as an alloy of platinum
and iridium, and in one embodiment is electrically insulated from
body fluids. The ring 562 includes a porous tip electrode 564,
which is electrically active and in contact with body fluids. The
porous tip 564 in FIG. 20 is larger than the porous tip 554 shown
in FIG. 18, where the porous tip 564 extends across a substantial
amount of the tip 564. In one embodiment, the porous tip 564 is
made of corrosion-resistant material and comprises a screen. When
the porous tip 564 rests against the endocardial wall of the heart,
the tissue of the heart encapsulates and grows into the screen to
passively attach the electrode to the heart.
[0133] FIG. 21 illustrates a variation of the electrode shown in
FIG. 20, where the conductive ring 570 includes a first porous tip
572 and a second porous tip 574. The ring 570 is electrically
insulated from body fluids, and the first and second porous tips
572 and 574 are electrically active and in contact with body
fluids. The porous tips 572, 574 are also made of highly
corrosion-resistant material. Like the previous conductive rings
shown, the tissue of the heart encapsulates and grows into the
porous screen in order to provide passive attachment of the
electrode to the endocardial wall of the heart.
[0134] FIG. 22 shows that a smooth ring 578 can also be used as the
main element of the electrode in the curved portion of the lead.
The smooth ring 578 is made of a corrosion-resistant material that
is highly conductive. All of the ring 578 can be exposed or a
portion of it can be masked or insulated, so that a portion is
nonconductive.
[0135] FIG. 23 shows another variation and includes a ring 580. A
surface 582 of the ring 580 is comprised of layers of conductive
mesh or other porous materials attached to the ring 580. The layers
of conductive mesh or porous materials create an active surface for
pacing and sensing and a layer for enhanced tissue ingrowth.
Alternatively, texturization or other surface treatment could be
applied directly to the ring 580 to enhance tissue ingrowth.
[0136] FIG. 24 illustrates another embodiment of an electrode for
use with the curved portion of the lead. A ring 584, made of highly
conductive material insulated from body fluids includes a modified
raised ridge 586. In one embodiment, layers of conductive porous
material are deposited on an electrically conductive thin band 587
rather than across the entire width of the ring. In another
embodiment, all of the ring 584 can be exposed or a portion of it
can be masked or insulated so that a portion is nonconductive.
[0137] FIG. 25 shows an portion of a lead 590 including a porous
tip type of electrode 594 (similar to the porous tip shown in FIGS.
18 and 19) which is not mounted on a ring. The porous tip electrode
594 is placed in either a straight or curved portion of the lead.
In one embodiment, the porous tip electrode 594 is placed directly
into the surface of the lead 590, and an electrical conductor 596
is attached to the electrode. In another embodiment, the surface of
the lead 590 near the electrode 594 may be textured to enhance the
ability of the lead 590 to become passively fixed to the wall of
the heart. It should be noted that the above described electrodes
illustrated in FIGS. 18-25 can be used along any curved or straight
portion of a lead, and can be disposed in the various positions
described above. The pacing and sensing tip points out in the
direction of the bias or, alternatively, is on the portion of the
lead body that is closest to the wall of the heart.
[0138] FIG. 26 is a side view of one type of lead 600 for
delivering electrical pulses to stimulate the heart. The lead 600
is comprised of a connector terminal 610 and a lead body 620. The
lead 600 attaches to a pulse sensor and generator 640. The lead
body has a number of electrodes in the distal end 630 which is
implanted within, on, or about the heart (FIG. 27). The distal end
130 of the lead body 120 includes a curved or bias portion 150 and
a straight portion 160. The connector terminal 610 electrically
connects the various electrodes and conductors within the lead body
to the pulse sensor and generator 640. The pulse sensor and
generator 640 contains electronics to sense various pulses of the
heart and also produce pulsing signals for delivery to the heart.
The pulse sensor and generator 640 also contains electronics and
software necessary to detect certain types of arrhythmias and to
correct for them. Physicians are able to program the pulse sensor
and generator to correct a particular arrhythmia that the patient
may have. It should be noted that there are numerous types of
connector terminals which connect to a pulse sensing and generating
unit 640. The lead terminal connector 610 provides for the
electrical connection between the electrodes on the lead 100 and
pulse generator 640. The connector terminal end 610 shown is
designed to international IS-1 Standard ISO 5841-3(E).
[0139] The lead body 620, in one embodiment, is cylindrical in
shape and includes tubing material formed from a polymer
biocompatible for implantation, and preferably the tubing is made
from a silicone rubber polymer. The silicone rubber polymer tubing
contains several electrical conductors (not shown). The electrical
conductors are made of a highly conductive, highly
corrosion-resistant material which is formed into a helix, and are
housed within the lead body 620. When there is more than one such
electrical conductor within the lead body 620, the lead is called a
multifilar lead. The electrical conductors carry current and
signals between the pulse sensor and generator 640 and the
electrodes located at the distal end 630 of the lead 600.
[0140] After implantation within or on or about the heart 612, as
illustrated in FIG. 27, the curved or biased portion 650 will
generally be located in the right ventricle 613 of the heart. The
straight portion 660 of this lead body will generally be located in
the right atrium 614.
[0141] In one embodiment, the distal end 630 of the lead 600 has
four electrodes. The first electrode 654, also referred to as the
distal electrode, is provided at the farthest distal end of the
lead for the purpose of delivering ventricular pacing therapy. A
second electrode 653 is located near the first or distal electrode
654 and can be used as a counter electrode for electrode 654 or as
a current source for defibrillation therapy. This electrode 653 is
sometimes referred to as a ventricular shocking coil. A third
electrode 661 is located at a more proximal position for the
purpose of delivering atrial pacing therapy. The electrode 661, in
another embodiment, is actively attached to the atrial wall of the
heart 612. The third electrode 661 is also referred to as the
proximal electrode. A fourth electrode 662 is located near the
electrode 661 and can be used as a counter electrode for electrode
661 or as part of a defibrillation therapy system. The fourth
electrode 662 is sometimes called the SVC shocking coil. The lead
600 may be generally described as a tachycardia or tachy lead. The
shocking coils 653 and 662 are electrically conductive rings made
of an alloy of platinum and iridium which is highly conductive and
highly resistant to corrosion. The electrode 661 uses, in one
embodiment, the active fixation element described further below.
The electrode 654 may include an active fixation or passive
fixation portion. It should be noted that the lead shown and
described above is a bipolar lead in that the positive and negative
portions of a circuit are located in the lead body 600. It should
be noted that this lead may also be made a unipolar lead. In other
words, one electrode of the lead body 600 can be the shocking coil
and the other electrode can be the signal generator.
[0142] In one embodiment, the relaxed shape of the lead body 620
conforms to the shape the lead is expected to take after
implantation. The distal portion of the straight portion 660 and
the proximal portion of the curved portion 650 are biased to
conform to the mid-portion of the atrial wall. This shape
facilitates the placement of electrode 661 against the atrial wall
during implantation. Furthermore, because the natural unstressed
shape of the lead before implantation is approximately the same
after implantation, this reduces the nominal residual stresses in
the lead body. Also, this will reduce the nominal forces between
the atrial wall and the point of attachment of the electrode 661 in
the atrium. In another embodiment, the shape of the middle and end
portions of portion 650 conforms to the shape of the upper
ventricular chamber below the tricuspid valve and ventricular
septal wall. This shape will tend to cause the lead 600 to lie
across the top of the ventricle in a gradual arc with the electrode
653 lying against the ventricular septum and electrode 654 resting
in the ventricular apex. This lead position is advantageous because
the arc shape will tend to reduce the transmitted forces between
the lead fixation points at electrode 661 in the atrium and
electrode 654 in the ventricle as they move relative to each other
during heart rhythm. This preformed shape will ease the surgeon's
task of positioning of lead 600 and, particularly, of the electrode
end 630 such that less time is required and the placement procedure
is less prone to error.
[0143] The discussions of leads having a curved portion in related
U.S. patent application Ser. No. 09/121,020, filed on Jul. 22, 1998
entitled SINGLE PASS DEFIBRILLATION/PACING LEAD WITH PASSIVELY
ATTACHED ELECTRODE FOR PACING AND SENSING, and related U.S. Pat.
Nos. 6,152,954, 6,321,122 and 5,885,221, all of which are hereby
incorporated by reference in their entirety. The above described
leads, including but not limited to multi-site pacing leads for one
or more chambers of the heart, as well as bifurcated leads can also
be combined with the embodiments relating to the leads having a
curved portion.
[0144] FIG. 28 illustrates a side view of a single-pass endocardial
lead 700 for multi-site pacing within a single chamber of the
heart. During insertion, a stylet or wire is placed down a lumen
within the lead 700. This makes for a stiffened lead body 700 which
can be pushed through the body into the appropriate chamber of the
heart. The lead 700 includes a connector end 720 which, in one
embodiment, has a yoke 710 and extends to a distal end 730. The
lead 700 also includes a first leg 740 and a second leg 750, which
each include at least one electrode.
[0145] The lead 700 includes a recess 712 which houses the second
leg 750. The second leg 750 is maintained within the recess 712
while the lead 700 is being routed through the body, into the major
vein or subclavian vein and ultimately into one of the chambers of
the heart. The electrode 732 associated with the first leg 740, in
one embodiment, includes a passive fix element 733. The passive fix
element 733, in one embodiment, includes a wire mesh screen which
allows for the fibers of the heart to grow within the fiber mesh
screen over time. In yet another embodiment, the passive fix
element 733 includes a set of tines 734 near the electrode 732. The
tines 734 also provide for attachment of the electrode 732 to the
endocardial wall of the specific chamber in the heart to which the
first leg 740 of the lead 700 is to be attached.
[0146] FIG. 29 illustrates another side view of the lead 700 after
the stylet (not shown) which extends down the body of the lead 700
and into the first leg 740 has been removed. When the stylet is
removed, the first leg 740 is allowed to return to its natural
state. In this particular case, the first leg 740 of the lead 700
includes a curve therein, for example, a J-shaped curve. The radius
of the curve and the length of the leg 740 are or may be varied in
order to accomplish placement of the lead 732 at various positions
within a particular single chamber of the heart. It should be noted
that FIG. 29 illustrates the second leg 750 still housed within the
recess 712 in the body of the lead 700.
[0147] Now turning to FIG. 30, the single-pass endocardial lead 700
for multi-site pacing is shown after the second leg 750 has been
removed or pushed out of the recess 712 within the body of the lead
700. The second leg 750 is also J-shaped or curved and has an
electrode 752 positioned near the free end 755 of the leg 750. The
free end 755 of the second leg 750 also includes an active fix
element 754 which is used to actively fix the electrode 754 to an
endocardial wall of a chamber of the heart. It should be noted that
the first leg 740 and the second leg 750 need not be J-shaped or
curved and that either the first leg or the second leg each can
either include a passive fix element or an active fix element. The
advantage of this particular configuration is that the passive fix
element will not catch on any of the veins or tissue as it is
passing through the subclavian vein and into the heart. As this is
being done, the active fix portion 754 of the second leg is kept
within the recess 712 of the lead 700 so that the active fix
element 754 will not catch on any tissue during insertion. It
should also be noted that the radius of the curve and the position
and length of the first leg 740 and the second leg 750 can be
varied for various applications of multi-site pacing within a
single chamber of the heart. It should be noted that for different
chambers, different lengths of the legs 750 and 740 might be
appropriate, as well as different radii. The configuration shown in
FIG. 30 could be placed or positioned within the atrium (not shown)
of the heart. This configuration could be used for simultaneous
atrial appendage and Bachman's Bundle pacing.
[0148] FIG. 31 shows a variation of a single-pass endocardial lead
760 for multi-site pacing from the ones shown in FIGS. 28-30. The
lead 760 shown in FIG. 31 includes many of the same elements of the
lead shown in FIGS. 28, 29, and 30. Rather than repeat all the same
elements or similar elements between the lead 760 and the lead 700
shown in FIGS. 28, 29, and 30, only the differences will be touched
upon or described in the following paragraph.
[0149] The lead 760 differs from the lead 700 in that the lead 760
includes a second leg 762 which is straight after it has been
removed or forced out of the recess in the lead body 764. The
second leg 762 includes an electrode 752 as well as an active fix
portion 754 for attaching to the endocardial wall of the heart. If
this configuration was placed in the atrium, it could be used for
simultaneous atrial appendage pacing, and pacing at the entrance of
the coronary sinus.
[0150] FIG. 32 shows yet another embodiment of a single-pass
endocardial lead 770 for multi-site pacing within a single chamber
of the heart. The lead 770 includes a connector end 774 and a
distal end 776 having a first leg 778, a second leg 780 and a third
leg 782. The lead 700 has a recess which is capable of holding a
second leg 780, and a third leg 760. The first leg 778 is, in one
embodiment, J-shaped or, alternatively, curved and includes an
electrode 784. The electrode 784, in another embodiment, is used as
part of an active fix element 786. The first leg 778 also includes
a set of tines 788 which enables or allows active fixation of the
electrode 778 to an endocardial wall of the heart. The second leg
780 is a straight leg having an electrode 792 and an active fix
portion 794. The third leg 782 includes an electrode 796 and an
active fix portion 798.
[0151] During insertion of the lead 770 into a patient, a stylet
(not shown) is placed into a lumen of the lead 770. The stylet will
pass all the way down to and into the first leg 778 of the lead
770. During insertion, the second leg 780 and the third leg 782
will be housed or in a withdrawn position within either a single
recess 790, or alternatively a pair of recesses within the lead
770. With the stylet in place, the lead can be maneuvered and
positioned through the major arteries and into the heart. Once the
lead 770 is positioned within the heart, the stylet is removed and
a J-shaped natural shape is assumed by the first leg 778. After the
lead 770 has been placed within the selected chamber of the heart,
the second leg 780 and the third leg 782 can be removed or extended
out of the recess in the body of the lead 770. It should be noted
that the first, second and third legs 778, 780, 782 may either be
curved or alternatively J-shaped and can also either be attached to
the endocardial wall of the heart by active fixation or passive
fixation. The position and length of the legs can be varied to
produce different multi-site placements of the electrodes within
the heart. Each of the electrodes 784, 792 and 796 can be either a
bipolar or unipolar configuration. The particular configuration
shown in FIG. 32, if placed within the atrium of the heart, can be
used for a simultaneous atrial appendage, pacing at the Bachman's
Bundle and pacing at the entrance to the coronary sinus.
[0152] FIGS. 33, 34, and 35 show several other embodiments of the
invention. FIG. 33 is a side view of a lead 800 which includes an
active fixation element 832 for attachment to the atrial wall of
the heart. The lead 800 includes a main lead body 802, an atrial
lead body 805 (FIGS. 34 and 35) and a ventricle lead body 804. The
main lead body 802 is attached to a yoke 806. The yoke 806 acts as
a strain reliever and also has a series of terminal pins 808, 810
and 812 attached to the yoke/strain reliever 806. The terminal pins
808, 810, and 812 are attached to the pulse generator (not shown).
The main lead body 802 is longer than as shown; a break has been
put into the main lead body 802 to illustrate that the main lead
body 802 is longer than that shown in FIG. 33.
[0153] The main lead body 802 includes a recess 814 where the
atrial lead body 805 (FIGS. 34 and 35) fits within the recess 814
in the main lead body 802. When the atrial lead body 805 is housed
within the recess 814, an active fixation element 832 on the end of
the atrial lead body 805 and associated with the proximate
electrode is also housed within the recess 814. Advantageously, the
active fixation element 832 will not hook or snag tissue when it is
housed within the recess 814. Typically, the atrial lead body 805
is pulled back or housed within the recess 814 when the lead 800 is
being surgically implanted into the patient. Typically, the lead
800 is placed in the subclavian vein of the patient and then passed
through the subclavian vein to the inner chambers of the heart.
Once the lead and, more specifically, the distal electrode and the
proximal electrode are within the ventricle and atrium of the
heart, the various leads are removed from their respective recesses
so that a surgeon can attach them to the inner wall of the
heart.
[0154] FIG. 34 is a side view of the embodiment of a lead 800 shown
in FIG. 33. FIG. 34 has a J-shaped atrial lead body 807 which
emerges from the recess 814 in the main body 802 of the lead 820.
On the end of the atrial lead 807 is an active fixation element
832. The active fixation element 832, in one embodiment, includes a
helically shaped hook for screwing into the atrium of the heart.
The J-shape of the lead facilitates positioning of the end of the
electrode having the active fixation element 832 to a desired
position within the atrium. The J-shape eases positioning within
the atrium of the heart when certain portions of the atrium are the
target for connection of the active fixation element 832. Once
properly positioned, a surgeon can turn and/or advance the active
fixation element 832 causing it to hook the tissue in the inner
wall of the heart. The atrial lead 807, in one embodiment, is moved
with respect to the recess 814 by pushing the respective terminal
pin 810 toward the yoke 806. By moving the terminal pin 810 toward
the yoke 806, a conductor, which connects the terminal pin 810 and
the active fixation element 832, moves with respect to the main
body 802 of the lead 820. Alternatively, the terminal pin 810 can
be moved longitudinally with respect to the main body 802. This
movement causes the atrial lead body 807 to emerge or pass through
or pass out of the recess 814 in the main body 802. The terminal
pin 810 and the active fixation element 832 attached to it, in one
embodiment, move independently of the lead body 820. Twisting the
terminal pin causes the active fixation element 832 on the atrial
lead body 807 to turn and affix itself to the atrial wall of the
heart. This additional degree of freedom allows for movement of the
lead body relative to the fixed atrial electrode without unscrewing
(or over-screwing) the electrode from the endocaridal tissue. A
locking mechanism may be provided to prevent the active fixation
element 832 from "backing out" after it has been affixed to the
wall. The atrial lead 807, in another embodiment, is prestressed so
that it will take the J-shape upon leaving or coming out of the
recess 814.
[0155] FIG. 35 is a side view of another embodiment of the lead
shown in FIG. 33. In this particular embodiment, the lead 830 has a
straight atrial lead body 840 which comes out of the recess 814 in
the main lead body 802. The position of the atrial lead body 840 is
controlled by movement of the terminal pin 810 with respect to the
yoke 806. Moving the terminal pin 810 with respect to the yoke 806
causes the atrial lead 840 to come out of the recess 814. An active
fixation element 832 is positioned on the end of the atrial lead
840. Once the surgeon positions the atrial lead 840 and the active
fixation element 832 at the end of the atrial lead 840 in a proper
position or desired position, the active fixation element 832 is
used to attach the proximal electrode to the endocardial wall of
the atrium.
[0156] The above and below-discussed lead embodiments can each be
provided with, for example, active or passive fixation devices.
FIG. 36 illustrates one embodiment of a passive fixation device
856. A plurality of tines 852 are disposed about the distal end 854
of the electrode 850. Other examples of a passive fixation device
856 include a mesh screen (further discussed below) which can be
used independently or in combination with other passive fixation
devices such as the plurality of tines 852. Other passive fixation
devices are also shown in FIGS. 14, 15A, 15B, 16, 17A, and
28-35.
[0157] In another embodiment, the above and below discussed lead
embodiments can alternatively and/or additionally be provided an
active fixation device. One example of an active fixation device
for the lead is a retractable screw, as shown in FIGS. 10-13, 26,
30-32, 34, and 35, and also further described below. FIGS. 37 and
38 illustrate another embodiment of an active fixation device. As
mentioned previously, the electrode 861 is designed to be attached
to the wall of the heart. FIG. 37 shows electrode 861 in a recessed
position and FIG. 38 shows electrode 861 actively extended. In this
embodiment, the electrode 861 includes an active fixation screw 863
which, in one embodiment, comprises a helical screw. The electrode
861, in one embodiment, is configured to initially rest inside the
lead body 860, and then extend and rotate independent of the lead
body 860 for attachment to the wall of the heart. FIG. 37 shows the
electrode 861 and the fixation screw 863 resting within the lead
body 860. A seal 870 is provided, in another embodiment, which
assists in preventing body fluids from traveling into the recess in
the lead body. The seal 870 is made of a biocompatible material
such as silicone rubber and may take any appropriate shape. In this
instance, the seal 870 is shaped as a permanent O-ring affixed to
the recess in the lead body 860. This covered position of the
electrode 861 and active fixation screw 763 makes the lead
placement process easier since the electrode 861 does not snag the
vein during initial venous access and subsequent movement of the
lead to the heart. The seal 870 can also be used to hold a
lubricant (not shown) within the recess of the body 860 of the
lead. The lubricant will allow the electrode 861 to move from
inside the recess to outside the recess with greater ease. The
lubricant can be a substance such as fluorosilicone which is
biocompatible.
[0158] FIG. 38 shows the electrode 861 extended from the lead body
860. The electrode 161 and active fixation screw 863 move
independent of the lead body 860. This relative movement allows the
electrode to come in contact with the wall without manipulation of
the lead body 860. The electrode 861 can then be fixed by rotating
the electrode 861 and attached fixation screw 863. The fixation
screw 863 of the electrode 861 can be advanced and retracted
independent of rotation of the lead body 860. The active fixation
screw and attached electrode, in one embodiment, are controlled
from the terminal end, as discussed above.
[0159] As mentioned previously, the electrically conductive portion
864 which either senses electrical energy produced by the heart or
delivers pacing signals to the heart is a small radius electrode.
The electrode 861 has a diameter, in one embodiment, in the range
of 0.024 inches to 0.050 inches. The advantage of this small radius
is ease of venous access and small surface area resulting in high
impedance for saving energy. Saving energy makes the battery used
to power the pulse generator (discussed above) last longer.
[0160] Also shown in FIGS. 37 and 38 is a multifilar coil 865 and
an electrically conductive sleeve 866. The conductive sleeve 866
has the smaller radius electrode tip 864 attached at one end of the
sleeve. At the other end of the sleeve 866, the multifilar coil 865
is attached. The multifilar coil 865 includes at least one
conductor which is used to carry electrical signals to and from the
electrode tip 864.
[0161] In yet another embodiment, the active fixation device
comprises the movement assembly as shown in FIGS. 39 and 40. A lead
900 is provided extending to a distal end 904 which includes an
active fixation element 970. The active fixation element 970, in
one embodiment, comprises a helical screw 972. In one
configuration, the active fixation element 970 is retractable,
which assists in avoiding injury to the patient during
implantation. Alternatively, the active fixation element 970
rotates without translating along the lead 900. For the
configuration where the active fixation element 970 rotates without
translating along the lead 900, a material, such as mannitol, is
disposed about the active fixation element 970 to prevent snagging
the interior of the vein as the lead 900 is positioned within the
patient. The lead 900, in one embodiment, includes a movement
assembly 902 which is adapted to transport the active fixation
element 970. Alternatively, in another configuration, the distal
end 904 of the lead 900 can include a passive fixation element, as
discussed above.
[0162] The movement assembly 902 includes external threads 920
associated therewith. In one configuration, the external threads
920 are disposed about a collar 922 of the lead 900. The external
threads 920 are adapted to engage with internal threads 926
disposed within a housing 924 of the lead 900. The external threads
920 provide a helical path for the internal threads 926. The
movement assembly 902 is not, however, limited to the components
described herein. For instance, the external threads 920 and the
internal threads 926 can be provided on alternative components, and
still be considered within the scope of the invention.
[0163] In one configuration, an insert 930 is provided for the
internal threads 926, as shown in FIG. 40. The insert 930 contains
internal threads 926 which are adapted to engage with the external
threads 920 of the collar 922. Although internal and external
threads are described, other equivalent movement assemblies can
also be incorporated such as those incorporating a track. During
use, the terminal pins (discussed above) are rotated which causes
the collar 922 to rotate. As the collar 922 is rotated and the
external threads 920 and the internals threads 926 engage, the
active fixation element 970 moves along the axis of the lead 900.
The movement assembly 902 can be used with a wide variety of leads
implementing active fixation, including, but not limited to, single
pass dual chamber pacing leads, single pass dual chamber
pacing/defibrillator leads, single chamber pacing leads, and single
chamber pacing/defibrillator leads.
[0164] Referring again to FIG. 39, a mesh screen 940 is provided in
another embodiment. The mesh screen 940 allows for better tissue
in-growth, as well as enhanced sensing capabilities. The mesh
screen 940 is disposed proximate to the active fixation element
970. In one embodiment, as the active fixation element 970 is
translated and extended from the lead 900, mesh screen 940 moves
with the active fixation element 970. The fixation element 970
engages the heart tissue and draws the mesh screen 940 into contact
with the surface of the heart.
[0165] In another configuration, the lead 900 is provided with a
medication distribution member which is adapted to release medicine
after the lead 900 has been implanted into a patient. In one
embodiment, the medication distribution member comprises a steroid
plug 942 which is provided proximate to the mesh screen 940. The
steroid plug 942 is located behind the mesh screen 940 relative to
the heart. In another embodiment, the medication distribution
member comprises a medication collar 943 to release drugs, such as
a steroid medication. Drugs can be provided which prevent tissue
inflammation after the electrode has been attached to the heart or
which assist in blood clotting, or assist in providing other
treatments.
[0166] In yet another embodiment, the lead, as described above and
below, has an increased impedance or a high impedance which can act
to extend the life of the battery. The discussion of leads having a
curved portion in related U.S. Pat. No. 6,501,994 is hereby
incorporated by reference in its entirety. It should be noted that,
in an alternative embodiment, the below discussed high impedance
embodiments can also be combined with the above described lead
embodiments including, but not limited to multi-site pacing for one
or more chambers of the heart, bifurcated leads, and leads having
curved portions. There are a number of ways in which increased
impedance may be effected for mechanically fastened electrode
connections in atrial/ventricular implantable catheters (AVIC)
systems. These include at least the following: 1) a fully insulated
tissue engaging tip (at least with respect to all surfaces that are
in electrical contact or electrically active physical relationship
to heart muscles so that a pace would be effective if discharged at
that portion of the tip), 2) a partially insulated (only a portion
of the surface area of the engaging tip being insulated, preferably
there is sufficient coating so that at there is at least 5%, or at
least 10%, or at least 20 or 30%, or at least 40, 50 or 60%, or at
least 70, 75, 80 or 90% of the surface area of the tip which can
discharge to heart muscle [or as percentages of the entire tip or
as percentages of the entire tip that extends physically beyond the
end plane of the catheter and which may therefore penetrate tissue
or muscle]), 3) a porous, electrically conductive element, such as
a mesh or screen of material at the proximal end of the helix or
the distal end of the lead (excluding the helix), at the base of an
extended engaging tip, 4) the selection of materials in the
composition of the mesh and/or tip which provide higher impedance,
5) the partial insulative coating of a porous conductive element,
such as the mesh or screen to increase its impedance, and 6)
combinations of any of these features. There may be various
constructions to effect the increased or high impedance, including
the use of helical tips with smaller surface areas (e.g., somewhat
shorter or thinner tips). There may also be other elements
associated with the catheter and/or leads, such as a sheath of
material inert to body materials and fluids, circuitry,
microcatheters, and at least one conductor extending through the
lead body.
[0167] One aspect of the present invention comprises an implantable
electrode with a helical tip comprising:
[0168] an electrode having a distal end and a proximal end; and
[0169] a helix disposed within the electrode, which helix is
aligned along a radial axis of the electrode towards the distal
end, and which helix is either retractable or fixed; and
[0170] the implantable electrode having at least one feature
selected from the group consisting of:
[0171] a) the helix having a coating of an insulating material on
its surface which covers at least 5% of its surface area but less
than 95% of its surface area (which is exposed beyond the distal
end of the electrode),
[0172] b) the helix extending beyond the distal end of the
electrode and the distal end of the electrode having a porous
conductive surface at a base of the helix,
[0173] c) a porous conductive element such as a screen or mesh at a
base of the helix, which is retractable/extendable, with the helix
being either active or inactive (electrically), and
[0174] d) a partially insulated (partially insulation coated)
porous conductive element (e.g., screen or mesh) at the base of an
active or inactive, retractable/extendable or fixed helix.
[0175] The implantable electrode preferably has the helix with a
coating of insulating material on it surface which covers from
5-100% (to 100% where there is an additional electrode element
within the system) or 5-95% of surface area of the helix beyond the
distal end of the electrode, or surface of the helix which can be
considered to be in electrically discharge-functional physical
relationship with tissue or muscle into which it is embedded. For
purposes of measuring or determining the distal end of the
electrode, the tip extends beyond a tubular or cylindrical housing
or structural portion which is considered the electrode, and the
tip is an engaging portion that extends beyond the housing portion
of the electrode. The distal end of the electrode is usually
characterized as the end of the cylindrical housing or tubing
carrying the tip, circuits, conductive elements, guides, etc. It is
more preferred that the helix of the implantable electrode has a
coating of insulating material on it surface which covers from
5-95% or 10-90% of the surface area of said helix beyond the distal
end of the electrode.
[0176] A lead 1010 is illustrated in FIG. 1. The lead 1010
comprises a lead body 1011, an elongate conductor 1013 contained
within the lead body, and a lead tip 1020 with an optional
retractable tip assembly 1024 contained in the lead tip 1020. In
addition, a stylet 1014 is shown inserted into the lead body 1011.
A helix 1100 (FIGS. 42A-45A), which consists of an electrical
conductor coil, is contained in the retractable lead tip 1024. In
an alternative practice of the invention, the helix 1100 extends
and retracts by rotation of the stylet 1014, as will be discussed
further below. A Brady lead body is shown, although the invention
could be incorporated with other leads, such as Tachy leads. The
lead body 1011 consists of electrical conductors 1013 which are
covered by a biocompatible insulating material 1022. Polymers, such
as silicone rubber, fluorinated resins, polyacrylates, polyamides
ceramic or composite materials or other insulating material can be
used for covering the lead body 1011.
[0177] In one embodiment shown in FIGS. 43A and 43B, the helix 1100
is formed of electrically conductive material offering low
electrical resistance and also resistant to corrosion by body
fluids. A biocompatible metal, such as titanium or platinum-iridium
alloy is an example of a suitable material. Alternatively, the
helix 1100 is electrically inactive or insulated. In one
embodiment, the helix 1100 may be coated with an insulative
material (not shown) or may be constructed of a rigid, corrosion
resistant, non-electrically-conductive material (e.g., a ceramic).
A housing 1182, described in further detail below, is made from an
electrically conductive material and covered with an insulating
material such as a synthetic or natural polymer such as a silicone
rubber. The housing 1182 is directly connected to an electrical
conductor within the lead 1120. These materials are additionally
suitable because they tend to be biologically inert and well
tolerated by body tissue.
[0178] The helix 1100 defines a lumen and thereby is adapted to
receive a stiffening stylet 1014 that extends through the length of
the lead. The stylet 1014 stiffens the lead 1120, and can be
manipulated to introduce an appropriate curvature to the lead,
facilitating the insertion of the lead into and through a vein and
through an intracardiac valve to advance the distal end of the lead
1120 into the right ventricle of the heart (not shown). A stylet
knob 1154 is coupled with the stylet 1014 for rotating the stylet
1014 and advancing the helix 1100 into tissue of the heart.
[0179] In one embodiment, as shown in FIGS. 42A and 42B, a lead
1310 has an electrode tip 1320 which is provided with a mesh screen
1330. The mesh screen 1330, in one embodiment, completely
encapsulates the diameter of the lead, and may serve, at least in
part, as a pacing/sensing interface with cardiac tissue. If the
helix 1100 is electrically active, it too can help serve as a
portion of a pacing or sensing interface. The mesh screen 1330 is
of a porous construction, preferably made of electrically
conductive, corrosion resistant material. Using a mesh screen 1330
having a porous construction allows for fibrotic ingrowth. This
provides for a further anchoring of the lead tip 1320 and also
increases the sensing capability of the lead 1310 by increasing the
surface area in contact with the cardial tissue. The mesh screen
1330 may be attached to an electrode collar 1040, which is
electrically active. In a retractable catheter system, a housing
1380, which is electrically conductive, encapsulates the piston
1350 and the fixation helix 1100. Insulation 1382 is disposed about
the housing 1380 and collar 1040.
[0180] Disposed within the lead 1310 is a lead fastener 1100 for
securing the lead 1310 to cardiac tissue. The lead fastener 1100
can be disposed along the radial axis 1015 of the electrode lead
1310. In this embodiment, the lead fastener 1100 comprises a
fixation helix 1100. The fixation helix 1100 can be made
electrically active or inactive as discussed above. Attached to the
fixation helix 1100 in a retractable tip system is a piston 1350.
The piston 1350 is configured to mate with a bladed locking stylet
1014 at a stylet slot 1354, and acts as an interface between the
stylet 1014 and the helix 1100. The stylet 1014, coupled with the
piston 1350 at the stylet slot 354, extends and retracts the
fixation helix 1100 when the stylet 1014 is rotated. The piston
1350 can either be electrically active or inactive. The piston 1350
also has a slot 1352, which allows the piston 1350 to mate with a
base 1360.
[0181] Fitted with a knob 1362, as shown in FIG. 42A, the base 1360
mates with the slot 1352 of the piston 1350. The base 1360 serves
as a stop once the fixation helix 1100 is fully retracted. The
electrically conductive base 1360 also allows passage of a bladed
locking stylet 1014 and attachment of electrode coils (not
shown).
[0182] In addition, the lead 1310 has a guide groove 1370. The
groove 1370 is formed, in one embodiment, by puncturing a hole (not
shown) within the mesh screen 1330, although the guide groove 1370
can be formed by other methods known by those skilled in the art.
Having a circular cross-section, the guide groove 1370 may have a
diameter greater than that of the conductor forming the helix 1100.
The groove 1370 is disposed within the mesh screen 1330, and
directs the fixation helix 1100 from its retracted position, as
illustrated in FIG. 42A, to an extended position (not shown). The
groove 1370 also reversibly directs the fixation helix 1100 from an
extended position to the retraction position.
[0183] In a second embodiment, as shown in FIGS. 43A and 43B, a
lead 1110 has an electrode tip 1120 which is provided with a mesh
screen 1130. The mesh screen 1130 completely encapsulates the
diameter of the lead or electrode tip 1120, and serves as the
pacing/sensing interface with cardiac tissue. The screen 1130 is of
a porous construction, made of electrically conductive, corrosion
resistant material. Using a mesh screen 1130 having a porous
construction allows for fibrotic ingrowth. This provides for a
further anchoring of the lead tip 1120 to tissue and also increases
the sensing capability of the lead 1110. The sensing capability is
enhanced because the mesh screen 1130 has more surface area than
corresponding solid material. The ingrowth of fibrotic tissue into
the mesh screen 1130 increase the sensing capability of the lead
1110 by increasing the surface area in contact with the cardial
tissue. Furthermore, the geometry of the mesh screen 1130,
particularly any protuberance, as will be discussed below, creates
a high pacing impedance tip.
[0184] The mesh screen 1130 may form a protuberance 1135 from a
flat edge portion 1137 of the mesh screen 1130 in a generally
central portion of the electrode tip 1120. The protuberance 1135
may be generally circular in cross-section, but may be any shape
(e.g., truncated cylindrical, truncated pyramidal, oval,
ellipsoidal, etc.) as a result of design or circumstance which
provides a flat or conformable surface (preferably not a rigid,
sharp face which will not conform to tissue) abutting tissue, and
preferably has a diameter smaller than a diameter of the lead 1110
(although a larger. In addition, the protuberance 1135 is aligned
with the radial axis 1015 of the lead 1110. Sintered to an
electrode collar 1040, a process known by those skilled in the art,
the mesh screen 1130 is attached to the electrode tip 1120. The
electrode collar 1040 is electrically active.
[0185] Disposed within the electrode lead 1110 is a lead fastener
for securing the electrode lead 1110 to cardiac tissue. The lead
fastener can be disposed along the radial axis 1015 of the
electrode lead 1110. In this embodiment, the lead fastener
comprises a fixation helix 1100. The fixation helix 1100 can be
made electrically active or inactive to change sensing and pacing
characteristics, as discussed above. Attached to the fixation helix
1100 is a piston 1150. The piston 1150 is configured to mate with a
bladed locking stylet 1014, thereby providing a movement assembly.
The stylet 1014 extends and retracts the fixation helix 1100 when
the stylet 1014 is rotated. The piston 1150 can either be
electrically active or inactive. The piston 1150 also has a slot
1152. The slot 1152 of the piston 1150 allows the piston 1150 to
mate with a base 1160 upon full retraction.
[0186] The base 1160 is modified with a knob 1162 to mate with the
slot 1152 of the piston 1150. The knob 1162 mates with the piston
1150 to prevent over-retraction once the helix 1100 has been fully
retracted. The stylet 1014 operates to advance the fixation helix
1100. As the implanter rotates the stylet 1014, the stylet 1014
engages the piston 1150 at the stylet slot 1154 and rotates the
piston 1150, which moves the fixation helix 1100 through a guide
groove 1170. The guide groove 1170 is for ensuring that the
fixation helix 1100 is properly guided out of and into the end of
the electrode. Once the fixation helix 1100 is fully retracted, the
base 1160 serves as a mechanical stop. The base 1160 also allows
passage of a bladed locking stylet 1014 and attachment of electrode
coils. Additionally, the base 1060 is electrically active.
[0187] The electrode lead 1110 also has a guide groove 1170. The
groove 1170 is formed by puncturing a hole within the mesh screen.
Having a circular cross-section, the groove 1170 has a diameter
greater than that of the conductor forming the helix 1100. The
groove 1170 is disposed within the mesh screen 1130, and directs
the fixation helix 1100 from its retracted position, as illustrated
in FIG. 42A, to an extended position (not shown). During
implantation, after the electrode is in contact with tissue at the
desired location in the heart, the stylet 1014 is rotated which
causes the piston to advance the fixation helix out of the groove
1170. As the fixation helix 1100 is placed in an extended position,
the helix 1100 travels through groove 1170 and circles around the
protuberance 1135. The groove 1170 also directs the fixation helix
1100 from an extended position to the retracted position.
Advantageously, the mesh screen 1130 prevents the implanter from
overextension and advancing the helix 1100 too far into the tissue.
An electrically conductive housing 1180 encapsulates both the
piston 1050 and the fixation helix 1100. Insulation 1182 covers the
housing 1180, the collar 1040, and a portion of the mesh screen
1130. The insulation 1182 over the mesh screen 1130 controls the
impedance of the electrode tip 1120.
[0188] In a third embodiment as shown in FIGS. 44A and 44B, a lead
1010 has an electrode tip 1020 which is provided with a mesh screen
1030. The mesh screen 1030 completely encapsulates the diameter of
the lead tip. Sintered to an electrode collar 1040, the mesh screen
1030 is attached to the electrode tip 1020. The electrode collar
1040 is electrically active. A housing 1080 is disposed about the
helix 1100, and is electrically active. Insulation 1082,
encompasses the housing 1080 and collar 1040.
[0189] In one embodiment, as shown in FIGS. 42A and 42B, a lead
1310 has an electrode tip 1320 which is provided with a mesh screen
1330. The mesh screen 1330 completely encapsulates the diameter of
the lead, and serves as the pacing/sensing interface with cardiac
tissue. If the helix 1100 is electrically active, it too can help
serve as a pacing or sensing interface. The mesh screen 1330 is of
a porous construction, made of electrically conductive, corrosion
resistant material. Using a mesh screen 1330 having a porous
construction allows for fibrotic ingrowth. This provides for a
further anchoring of the lead tip 1320 and also increases the
sensing capability of the lead 1310 by increasing the surface area
in contact with the cardial tissue. The mesh screen 1330 is
attached to an electrode collar 1040, which is electrically active.
A housing 1380, which is electrically conductive, encapsulates the
piston 1350 and the fixation helix 1100. Insulation 1382 is
disposed about the housing 1380 and collar 1040.
[0190] Disposed within the lead 1310 is a lead fastener for
securing the lead 1310 to cardiac tissue. The lead fastener can be
disposed along the radial axis 1015 of the electrode lead 1310. In
this embodiment, the lead fastener comprises a fixation helix 1100.
The fixation helix 1100 can be made electrically active or inactive
as discussed above. Attached to the fixation helix 1100 is a piston
1350. The piston 1350 is configured to mate with a bladed locking
stylet 1014 at a stylet slot 1354, and acts as an interface between
the stylet 1014 and the helix 1100. The stylet 1014, coupled with
the piston 1350 at the stylet slot 1354, extends and retracts the
fixation helix 1100 when the stylet 1014 is rotated. The piston
1350 can either be electrically active or inactive. The piston 1350
also has a slot 1352, which allows the piston 1350 to mate with a
base 1360.
[0191] Fitted with a knob 1362, as shown in FIG. 42A, the base 1360
mates with the slot 1352 of the piston 1350. The base 1360 serves
as a stop once the fixation helix 1100 is fully retracted. The
electrically conductive base 1360 also allows passage of a bladed
locking stylet 1014 and attachment of electrode coils.
[0192] In addition, the lead 1310 has a guide groove 1370. The
groove 1370 is formed by puncturing a hole within the mesh screen,
although the guide groove can be formed by other methods known by
those skilled in the art. Having a circular cross-section, the
groove 1370 has a diameter greater than that of the conductor
forming the helix 1100. The groove 1370 is disposed within the mesh
screen 1330, and directs the fixation helix 1100 from its retracted
position, as illustrated in FIG. 42A, to an extended position (not
shown). The groove 1370 also directs the fixation helix 1100 from
an extended position to the retraction position.
[0193] In a second embodiment, as shown in FIGS. 43A and 43B, a
lead 1110 has an electrode tip 1120 which is provided with a mesh
screen 1130. The mesh screen 1130 completely encapsulates the
diameter of the lead tip, and serves as the pacing/sensing
interface with cardiac tissue. The screen 1130 is of a porous
construction, made of electrically conductive, corrosion resistant
material. Using a mesh screen 1130 having a porous construction
allows for fibrotic ingrowth. This provides for a further anchoring
of the lead tip 1120 and also increases the sensing capability of
the lead 1110. The sensing capability is enhanced because the mesh
screen 1130 has more surface area than corresponding solid
material. The ingrowth of fibrotic tissue into the mesh screen 1130
increase the sensing capability of the lead 1110 by increasing the
surface area in contact with the cardial tissue. Furthermore, the
geometry of the mesh screen, particularly the protuberance, as will
be discussed below, creates a high pacing impedance tip.
[0194] The mesh screen 1130 forms a protuberance 1135 from a flat
edge portion 1137 of the mesh screen 1130 in a generally central
portion of the electrode tip 1120. The protuberance 1135 is
generally circular in cross-section, and has a diameter smaller
than a diameter of the lead 1110. In addition, the protuberance
1135 is aligned with the radial axis 1015 of the lead 1110.
Sintered to an electrode collar 1040, a process known by those
skilled in the art, the mesh screen 1130 is attached to the
electrode tip 1120. The electrode collar 1040 is electrically
active.
[0195] Disposed within the electrode lead 1110 is a lead fastener
for securing the electrode lead 1110 to cardiac tissue. The lead
fastener can be disposed along the radial axis 1015 of the
electrode lead 1110. In this embodiment, the lead fastener
comprises a fixation helix 1100. The fixation helix 1100 can be
made electrically active or inactive to change sensing and pacing
characteristics, as discussed above. Attached to the fixation helix
1100 is a piston 1150. The piston 1150 is configured to mate with a
bladed locking stylet 1014, thereby providing a movement assembly.
The stylet 1014 extends and retracts the fixation helix 1100 when
the stylet 1014 is rotated. The piston 1150 can either be
electrically active or inactive. The piston 1150 also has a slot
1152. The slot 1152 of the piston 1150 allows the piston 1150 to
mate with a base 1160 upon full retraction.
[0196] The base 1160 is modified with a knob 1162 to mate with the
slot 1152 of the piston 1150. The knob 1162 mates with the piston
1150 to prevent over-retraction once the helix 1100 has been fully
retracted. The stylet 1014 operates to advance the fixation helix
1100. As the implanter rotates the stylet 1014, the stylet 1014
engages the piston 1150 at the stylet slot 1154 and rotates the
piston 1150, which moves the fixation helix 1100 through a guide
groove 1170. The guide groove 1170 is for ensuring that the
fixation helix 1100 is properly guided out of and into the end of
the electrode. Once the fixation helix 1100 is fully retracted, the
base 1160 serves as a mechanical stop. The base 1160 also allows
passage of a bladed locking stylet 1014 and attachment of electrode
coils. Additionally, the base 1060 is electrically active.
[0197] The electrode lead 1110 also has a guide groove 1170. The
groove 1170 is formed by puncturing a hole within the mesh screen.
Having a circular cross-section, the groove 1170 has a diameter
greater than that of the conductor forming the helix 1100. The
groove 1170 is disposed within the mesh screen 1130, and directs
the fixation helix 1100 from its retracted position, as illustrated
in FIG. 42A, to an extended position (not shown). During
implantation, after the electrode is in contact with tissue at the
desired location in the heart, the stylet 1014 is rotated which
causes the piston to advance the fixation helix out of the groove
1170. As the fixation helix 1100 is placed in an extended position,
the helix 1100 travels through groove 1170 and circles around the
protuberance 1135. The groove 1170 also directs the fixation helix
1100 from an extended position to the retracted position.
Advantageously, the mesh screen 1130 prevents the implanter from
overextension and advancing the helix 1100 too far into the tissue.
An electrically conductive housing 1180 encapsulates both the
piston 50 and the fixation helix 1100. Insulation 1182 covers the
housing 1180, the collar 40, and a portion of the mesh screen 1130.
The insulation 1182 over the mesh screen 1130 controls the
impedance of the electrode tip 1120.
[0198] In a third embodiment as shown in FIGS. 44A and 44B, a lead
1010 has an electrode tip 1020 which is provided with a mesh screen
1030. The mesh screen 1030 completely encapsulates the diameter of
the lead tip. Sintered to an electrode collar 1040, the mesh screen
1030 is attached to the electrode tip 1020. The electrode collar
1040 is electrically active. A housing 1080 is disposed about the
helix 1100, and is electrically active. Insulation 1082,
encompasses the housing 1080 and collar 1040.
[0199] Disposed within the lead 1010 is a lead fastener for
securing the lead 1010 to cardiac tissue. The lead fastener can be
disposed along the radial axis 1015 of the lead 1010. In this
embodiment, the lead fastener comprises a fixation helix 1100. The
fixation helix 1100 can be made electrically active or inactive to
change sensing and pacing characteristics.
[0200] The helix 1100 is of a well known construction. Using a
conductor coil such as helix 1100 has been shown to be capable of
withstanding constant, rapidly repeated flexing over a period of
time which can be measured in years. The helix 1100 is wound
relatively tightly, with a slight space between adjacent turns.
This closely coiled construction provides a maximum number of
conductor turns per unit length, thereby providing optimum strain
distribution. The spirally coiled spring construction of helix 1100
also permits a substantial degree of elongation, within the elastic
limits of the material, as well as distribution along the conductor
of flexing stresses which otherwise might be concentrated at a
particular point.
[0201] Attached to the fixation helix 1100 is a piston 1050. The
piston 1050 is configured to mate with a bladed locking stylet
1014. The piston 1050 advances the fixation helix 1100 once the
lead is placed in position within the heart. The piston 1050 can
either be electrically active or inactive. The piston 1050 also has
a slot 1052 and a stylet slot 1054. The stylet 1014 couples with
the stylet slot 1054 and extends or retracts the fixation helix
1100 when the stylet 1014 is rotated. The slot 1052 of the piston
1050 allows the piston 1050 to mate with a base 1060 when the helix
1100 is retracted to prevent over retraction. The base 1060 is
configured with a knob 1062 to mate with the slot 1052 of the
piston 1050. Once the fixation helix 1100 is fully retracted, the
base 1060 serves as a stop at full retraction. The base 1060 also
allows passage of a bladed locking stylet 1014 and attachment of
electrode coils. In addition, the base 1060 is electrically
active.
[0202] The lead 1010 also includes a guiding bar 1070. Extending
across the diameter of the tip, the guiding bar 1070 is generally
cylindrical in shape. The guiding bar 1070 directs the fixation
helix 1100 from its retracted position, as illustrated in FIG. 42A,
to an extended position (not shown) as the piston 1052 advances the
helix 1100. The guiding bar 1070 also directs the fixation helix
1100 as it is retracted from an extended position to the retraction
position through the mesh screen. Although a guiding bar 1070 is
described, other types of guiding mechanisms can be used such as
helical passageways, threaded housings, springs, and are considered
within the scope of the invention. Additionally, the lead 1010 is
provided with a seal (not shown) for preventing entry of body
fluids and tissue from entering the lead through the opening
therein. The seal could be a puncture seal between the piston 1050
and the base 1060. Alternatively, O-rings could be used to seal the
electrode.
[0203] In a fourth embodiment as shown in FIGS. 45A and 45B, a lead
1210 has an electrode tip 1220 which is provided with a mesh screen
1230. The mesh screen 1230 forms an annular ring having an open
center, where the annular ring is centered at a radial axis 1015 of
the electrode lead 1210. The mesh screen 1230 provides more surface
area than a smooth tipped electrode which aids in sensing. The
removal of the center portion of the mesh screen creates a high
impedance pacing tip due to the nature of the surface geometry.
Sintered, fused, bonded, adhesively secured or mechanically
attached to an electrode collar 1040, the mesh screen 1230 is
attached to the electrode tip 1220. The electrode collar 1040 is
electrically active.
[0204] Disposed within the lead 1210 is a lead fastener for
securing the lead 1210 to cardiac tissue. The lead fastener can be
disposed along the radial axis 1015 of the electrode lead 1210. In
this embodiment, the lead fastener comprises a fixation helix 1100.
The fixation helix 1100 can be made electrically active or inactive
as discussed above. Attached to the fixation helix 1100 is a piston
1250. The piston 1250 has a stylet slot 1254 and is configured to
mate with a bladed locking stylet 1014. The stylet 1014, coupled
with the piston 1250 at the stylet slot 1254, extends and retracts
the fixation helix 1100 when the stylet 1014 is rotated. The piston
1250 can either be electrically active or inactive. The base 1260
serves as a stop once the fixation helix 1100 is fully retracted.
The base 1260 also allows passage of a bladed locking stylet 1014
and attachment of electrode coils. The base 1060 is electrically
active.
[0205] Additionally, the lead also has a guiding bar 1270. The
guiding bar 1270 directs the fixation helix 1100 from its retracted
position, as illustrated in FIGS. 45A and 45B, to an extended
position (not shown). The guiding bar 1270 also directs the
fixation helix 1100 from an extended position to the retracted
position. Although a guiding bar 1270 has been described, other
types of mechanisms could be used to extend the helix, and are
considered within the scope of the invention. A housing 1280
encapsulates the piston 1250 and the fixation helix 1100, and
insulation 1282 is disposed over the housing 1280 and collar
1040.
[0206] Insulation generally covers the housing, the collar, and a
portion of the electrical discharge surface (e.g., the cathode, the
helix and/or the porous material or mesh). The insulation over the
mesh screen further controls the impedance of the electrode tip.
The insulated coating, whether present on the helix or the mesh or
other elements which are potentially electrically active or on
which electrical activity is to be suppressed, should be
biocompatible, non-thrombogenic, and otherwise safe for
implantation. The insulation coating should be of dimensions which
effect the insulation, increase the impedance (where desired), but
which dimensions do not interfere with the performance of the tip,
the lead or the helix or the health of the patient. The insulation
is present as a coating (a material which tends to conform to the
surface rather than completely reconfigure it, as would a lump of
material). The coating usually should be at least 0.5 microns in
thickness, usually between 0.5 and 100 microns, preferably between
1.0 and 30 or 50 microns, more preferably between 1 and 20 microns,
still more preferably between 1.5 and 15 microns, and most
preferably between 1.5 or 2.0 microns and 10 or 15 microns. The
coating may be provided by any convenient process, such as
electrophoretic deposition, dip coating, spin coating, in situ
polymerization, vapor deposition, sputtering and the like. Any
insulating material is useful, such as polymers, ceramics, glasses,
and the like, but because of their convenience in application,
flexibility and availability, polymers are preferred. Polymers from
such classes as polyesters, polyamides, polyurethanes, polyethers,
polysiloxanes, polyfluorinated resins, polyolefins, polyvinyl
polymers, polyacrylates (including polymethacrylates), and the like
may be used with various leads and tips according to the practice
of the present invention. Parylene is a preferred material, as
described herein, with a thickness of between 1.5 and 10
microns.
[0207] In yet another embodiment, a partially insulated fixation
helix is used to provide a relatively high impedance electrode
design. Leads comprising a distal or electrode end and a proximal
or connector end may be used. A "miniature" wire-in-basket porous
electrode may be sintered upon the distal end of a metallic pin,
provided with a blind hole. Circumferential to this subassembly, a
sharpened wire fixation helix may be positioned and attached at a
general location proximal to the electrode by any convenient means
which allows electrical continuity. This attachment includes, but
is not limited to, crimping, spot welding, laser welding, the use
of grooves upon the surface of the pin, the use of thin metallic
overband (also not shown) or any combination thereof. A portion of
this fixation helix is provided with an extremely thin layer of a
biostable, biocompatible polymer, which, inter alia, provides
electrical insulation between the fixation helix and the cardiac
tissue. In one embodiment, the insulated portion is the majority of
the fixation helix, leaving a relatively small uninsulated region
of fixation helix. This approach offers increased impedance to
reduce energy dissipation in pulsing functions, such as pacing
functions. Other varying embodiments include, but are not limited
to, a portion which is approximately or substantially equal to half
of the fixation helix, and a portion which is approximately or
substantially equal to a minority of the fixation helix. Such
embodiments provide different amounts of uninsulated region and
different amounts of impedance. The thin coating of electrically
insulating coating must usually be at least 1 micron in thickness
to provide a significant insulating effect, depending upon its
insulating ability and properties. The thickness of the coating is
limited primarily by physical limitations on the system. The
coating can not be so thick as to interfere with the fastening
ability of the helix or to in crease the size of the helix beyond
that which is tolerable for the use of the helix and the patient.
Typically, the coating is at least one micron up to about 100
microns, more typically the coating is between 1 and 30 microns,
preferably between 1.5 and 20 microns, more preferably between 1.5
and 15 microns, and most preferably between 2 and 10 microns. The
material used for the coating should, of course, be biocompatible
and even more preferably non-thrombogenic. Materials such as
Parylene TM, polyurethanes, polyacrylates (including
polymethacrylates), polyesters, polyamides, polyethers,
polysiloxanes, polyepoxide resins and the like can be used.
Crosslinked polymers within these classes may be preferred for
their resistance to breakdown and their physical durability. As the
coating is to be maintained within the body of a recipient, the
coating composition should not be water-soluble or aqueous soluble
within the parameters and environment encountered within animal
bodies (e.g., it should not be soluble within blood, serum or other
body fluids with which it might come into contact).
[0208] To the proximal end of this pin, a metallic conductor coil
may be conveniently attached to provide electrical connection to
the implantable pacemaker (not shown) by means of a connector. In
one embodiment, local (e.g., steroid or other medicinal) therapy is
provided by a (e.g., circumferential) steroid/polymer matrix
positioned immediately proximal to the porous electrode. In one
embodiment, the circumferential steroid/polymer matrix is provided
with a distal taper. Other embodiments include other distal
configurations, including, but not limited to, non-tapered or
"inflated" configurations. In one embodiment, an internalized,
medicinal or biologically active (e.g., steroid) releasing matrix
is used. Proximal to this biologically active (e.g., steroid)
eluting matrix, a generally cylindrical polymeric tubing (this is
the preferred shape, but the shape is a matter of choice) 1820 is
used to provide electrical insulation of this entire assembly. In
one embodiment the lead is "unipolar." In one embodiment an
ablative protective covering positioned over the entirety of distal
end 520 is used (not shown). One example of such a covering is the
mannitol "Sweet Tip"TM electrode of Cardiac Pacemaker, Inc.
CPI/Guidant. In one embodiment, a "bipolar" lead is provided with
the distal electrode features described.
[0209] During an in vitro evaluation of this electrode design,
polymeric coatings intended to partially insulate the fixation
helix were prepared and evaluated. In one embodiment, the Parylene
coating is extremely thin (.about.3.mu.), providing a coating with
uniform coverage which is adherent to the metallic substrate, and
which is controllable to provide an abrupt margin. The silicone
rubber coating is known to be somewhat thicker (.about.10.mu.),
uniform in coverage, somewhat less adherent to the metallic
substrate, and controllable to an abrupt margin. Other coatings may
be used without departing from the spirit and scope of the present
invention.
[0210] The Parylene or other insulative coating effectively
increases in vitro "pacing impedance." Application of a
non-continuous or partially extensive coating of an electrically
insulating polymer such as Parylene to the metallic fixation helix
produces the desired increase in impedance compared to an
uninsulated helix as well as other existing designs. For example,
it has been demonstrated that one embodiment using a coated
fixation helix provides a pacing impedance of over approximately
800 ohms which is larger than the impedance of some electrodes
using an uncoated fixation helix. The post-implant pacing impedance
of an embodiment using a coated fixation helix remains higher than
that of typical electrodes using an uncoated fixation helix. In one
experiment, a coated fixation helix using Parylene as an insulating
layer provided over 1200 ohms average pacing impedance on the day
of implantation and over 900 ohms ten days after the implant.
[0211] Additionally, post-implant average voltage threshold of the
Parylene insulated miniaturized electrode is less than the other
high impedance electrodes. Such performance is considered to be
desirable. In one experiment, an embodiment with a coated fixation
helix 1804 having a voltage threshold of approximately 0.2 volts on
the day of implant was measured at about 0.7 volts at ten days
after the implant (using a 0.5 ms pulse width). An electrode with
an uncoated fixation helix demonstrated over 0.8 volts average
voltage threshold at ten days after the implant, illustrating the
benefits of the coated fixation helix.
[0212] An additional benefit is that the coated fixation helix
embodiments may provide an improvement in both the implant as well
as post-implant average S-wave amplitude detection.
[0213] The miniaturized high impedance, positive fixation porous
electrode technology described here provides the following
advantages over the prior art. For one example, the coated fixation
helix embodiments provide an electrode where the benefits of high
impedance pacing are realized through downsizing the porous
electrode and insulating the fixation helix. Downsizing of the
porous electrode may be accomplished, for example, by having a
smaller porous (e.g., mesh) electrode supported on a non-conductive
surrounding support element (e.g., a polymeric or composite film
with a mesh central area, particularly a mesh truncated conical or
pyramidal area of flexible, conductive mesh). An area of the
completely conductive mesh may also be discontinuously coated
leaving a conductive central or conductive raised area,
particularly surrounding a contact, engaging element, or helix.
Further, an external steroid collar provides a fabrication
advantage since such a component can be readily mass produced
compared to smaller components with elaborate profiles. Still
further, fabrication of a lead with this external collar is
streamlined. The higher impedance design conserves battery power to
provide longer battery life with fewer battery replacements. Other
benefits exist which are not described in detail herein, however,
which those skilled in the art will appreciate.
[0214] FIG. 46 shows a high impedance catheter tip 1800 with a
partially insulated tip 1802 and a partially insulated mesh 1808.
The partially insulated tip (or helix) 1802 comprises one fully
insulated section 1804 and one uninsulated section 1806. The
partially insulated mesh 1808 comprises a first area 1810 of the
mesh 1808 which is insulated and second are 1812 of the mesh 1808
which is not insulated. The impedance of the catheter tip can be
readily controlled by the amount of surface area of the helical tip
itself and the area of the mesh (if present) which is insulated.
With a fixed conductivity in the tip and the mesh (if present), the
impedance can be increased by increasing the percentage of the
surface area of the tip or mesh which is insulated.
[0215] A hole 1820 is shown in the mesh 1808. The mesh 1808 may be
flat and flush with the end 1822 of the catheter 1816 or may be
partially wrapped (not shown) over the end 1820 or inside the end
1820 to affix the mesh to the catheter 1816. The mesh 1808 may also
be hemispherical, truncated conical, truncated pyramidal or any
other shape which may assist in allowing the mesh 1808 to more
compliantly contact tissue (not shown) surface to transmit the
pacing signal or discharge. Within the catheter 1816 may be a
soluble, elutable or dispersible material which carries medication
or biologically active material along with the catheter. For
example, anti-inflammatants, antibiotics, analgesics, pain-reducing
medication, vitamins, anti-viral medication, or the like may be
transmitted to the attachment site along with the catheter by
inclusion within a material 1814 carried within or on the catheter
1816.
[0216] The coating of insulation on the helical tip or mesh may be
applied by any convenient method, including, but not limited to
coating (e.g., dip coating), printing, spraying, brush application,
resist application and removal and the like. The insulation may
also contain active ingredients (such as those recited within
material 1814) to benefit the patient. The insulation carrying the
active material must not be soluble, so a polymer or other material
that is porous or has elutable materials must be used. The material
delivery does not have to be coextensive with the life of the
implant or the tip, and delivery of the material may be desirable
only over a short time period after insertion of the helical tip
and catheter.
[0217] A soluble or dispersible protective cap may also be placed
over the helical tip to reduce the possibility of any incidental
damage while catheterizing or moving the tip within a patient. As
previously noted, the cap material should preferably be
biocompatible or even digestible and may include such materials as
natural and synthetic materials such as sugars, starches, gelation
(unhardened), gums, resins, polymers, and the like. All components
of the catheter and tip which are exposed to the tissue or fluids
within a patient should be non-thrombogenic, and bio-acceptable.
There are extensive classes of commercially available materials
which meet these needs for metal, polymeric, composite and other
materials described within the practice of the present
invention.
[0218] It is contemplated that slight variations in the design of
the lead could be used for a particular application as required.
One such variation would be the provision of steroid elution from
any of the electrodes provided on the lead. Steroid elution can be
provided by using one or more of the steroid-releasing technologies
such as sleeves or collars positioned in close proximity to the
electrodes or by the use of internalized steroid-containing plugs.
Steroids are generally used in order to reduce the inflammation
associated with attaching an electrode to the endocardial wall of
the heart. By reducing the inflammation at the time of
implantation, the threshold values associated with the electrodes
are usually lower when compared to threshold values associated with
electrodes that did not elute a steroid over the attachment site.
An example of the composition of at least one collar is
dexamethasone acetate in a simple silicone medical adhesive rubber
binder or a steroid-releasing plug similarly fabricated.
[0219] Advantageously, the single pass lead allows for one, two, or
more chambers of the heart to be paced and/or sensed, while only
one lead is implanted within the patient. This assists in
preventing added stress and expense for the patient. In addition,
the active fixation element will not hook nor snag tissue when it
is retracted within the lead. The active fixation element also does
not require the use of a stylet, since the terminal pins are used
to extend and retract the active fixation element. The active
fixation allows for the lead to be positioned almost anywhere in
the atrium. The movement assembly assists in protecting the shape
of the helix even when the helix is under tension.
[0220] It is to be understood that the above description is
intended to be illustrative, and not restrictive. Many other
embodiments will be apparent to those of skill in the art upon
reading and understanding the above description. For example, the
present invention can be used with a variety of medical devices.
Although the use of the lead has been described for use in a
cardiac pacing system, the lead could also be applied to other
types of body stimulating systems. It should also be noted that the
above described embodiments of the systems and leads include
combinations of the various embodiments described herein. The scope
of the invention should, therefore, be determined with reference to
the appended claims, along with the full scope of equivalents to
which such claims are entitled.
* * * * *