U.S. patent application number 10/971551 was filed with the patent office on 2005-05-26 for myocardial lead attachment system.
This patent application is currently assigned to Cardiac Pacemakers, Inc.. Invention is credited to Coe, M. Sean, Gresl, Charles, Heil, Ronald W. JR., Kelley, Peter T., Palme, Donald F. II, Shiroff, Jason Alan, Westlund, Randy W..
Application Number | 20050113901 10/971551 |
Document ID | / |
Family ID | 34528512 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050113901 |
Kind Code |
A1 |
Coe, M. Sean ; et
al. |
May 26, 2005 |
Myocardial lead attachment system
Abstract
The present invention is a myocardial lead attachment system for
securing a distal end of a lead within a myocardium of a patient's
heart. The system includes an anchor, a tether coupled to the
anchor, and a delivery instrument for receiving and advancing the
anchor through a tract in the heart from a proximal entrance site
to a distal exit site in such a manner that the tether extends
proximally from the anchor through the tract. The delivery
instrument includes a needle having a distal tip and a nest. The
nest is positioned proximal to the distal tip and is sized to
receive the anchor. The delivery instrument further includes an
ejection mechanism for ejecting the anchor from the nest.
Inventors: |
Coe, M. Sean; (Plymouth,
MN) ; Heil, Ronald W. JR.; (Roseville, MN) ;
Kelley, Peter T.; (Buffalo, MN) ; Shiroff, Jason
Alan; (Shoreview, MN) ; Westlund, Randy W.;
(River Falls, WI) ; Palme, Donald F. II;
(Princeton, MN) ; Gresl, Charles; (San Francisco,
CA) |
Correspondence
Address: |
JASON R. KRAUS
FAEGRE & BENSON, LLP
2200 WELLS FARGO CENTER
90 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402-3901
US
|
Assignee: |
Cardiac Pacemakers, Inc.
St. Paul
MN
|
Family ID: |
34528512 |
Appl. No.: |
10/971551 |
Filed: |
October 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60514037 |
Oct 24, 2003 |
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60514665 |
Oct 27, 2003 |
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60514042 |
Oct 24, 2003 |
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60514714 |
Oct 27, 2003 |
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60514039 |
Oct 24, 2003 |
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60514146 |
Oct 24, 2003 |
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60514038 |
Oct 24, 2003 |
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60514713 |
Oct 27, 2003 |
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Current U.S.
Class: |
607/130 |
Current CPC
Class: |
A61B 2017/0417 20130101;
A61N 1/0568 20130101; A61B 5/296 20210101; A61N 2001/058 20130101;
A61B 17/06109 20130101; A61N 2001/0578 20130101; A61N 1/0587
20130101; A61B 2017/06042 20130101; A61B 2017/0608 20130101; A61B
17/0469 20130101 |
Class at
Publication: |
607/130 |
International
Class: |
A61N 001/05 |
Claims
We claim:
1. A myocardial lead attachment system for securing a distal end of
a lead within a myocardium of a patient's heart, the system
comprising: an anchor; a tether coupled to the anchor; and a
delivery instrument for receiving and advancing the anchor through
a tract in the heart from a proximal entrance site to a distal exit
site in such a manner that the tether extends proximally from the
anchor through the tract, said delivery instrument comprising: a
needle having a distal tip and a nest positioned proximal to the
distal tip and sized to receive the anchor, and an ejection
mechanism for ejecting the anchor from the nest.
2. The lead attachment system of claim 1 wherein the ejection
mechanism further comprises an actuator for ejecting the anchor
from the nest.
3. The lead attachment system of claim 1 wherein a distal portion
of the needle is formed with a radial curvature.
4. The lead attachment system of claim 2 wherein the ejection
mechanism further comprises an elongated member slidable from a
retracted position to an extended position in response to actuation
of the actuator to engage the anchor mechanism.
5. The lead attachment system of claim 4 further comprising: a
mechanical stop for limiting extension of the elongated member; and
a resilient member biasing the actuator to retract the elongated
member.
6. The lead attachment system of claim 1 wherein the delivery
instrument further comprises: a distal electrically active area on
the needle; and a conductive member for connecting the electrically
active area to an external electrical device.
7. The lead attachment system of claim 1 wherein the nest further
includes a slot for receiving the tether.
8. The lead attachment system of claim 1 wherein the nest includes
a ramp adapted to assist in ejection of the anchor.
9. The lead attachment system of claim 1 further comprising a lead
body having a proximal end, a distal end, and at least a first
electrode near the distal end, said lead body adapted to advance
over the tether through the tract.
10. The lead attachment system of claim 9 wherein the lead body is
a unipolar lead.
11. The lead attachment system of claim 10 wherein the lead body
includes a second electrode spaced apart the first electrode apart
by about at least 2 cm.
12. The lead attachment system of claim 9 wherein the lead body is
a pseudo-unipolar lead.
13. The lead attachment system of claim 9 wherein the lead body is
a bipolar lead.
14. A myocardial lead attachment system for securing a distal end
of a lead within a myocardium of a patient's heart, the system
comprising: an anchor having a longitudinal bore extending
therethrough; a tether coupled to the anchor; and a delivery
instrument for receiving and advancing the anchor through a tract
in the heart from a proximal entrance site to a distal exit site in
such a manner that the tether extends proximally from the anchor
through the tract, said delivery instrument comprising: a needle
having a proximal end, a distal end formed with a nest for
receiving the anchor and a central lumen extending therethrough; a
stylet slidably received in the needle lumen and the anchor bore,
and an ejector plug formed on the stylet for engaging the
anchor.
15. The lead attachment system of claim 14 wherein the nest is an
open sleeve at the distal end of the needle.
16. The lead attachment system of claim 15 wherein the nest has an
internal stop for transmitting an axial force to the anchor.
17. The lead attachment system of claim 15 wherein the anchor has a
proximal region sized to be received in the nest and a distal
region sized to be retained outside of the nest.
18. The lead attachment system of claim 15 wherein the anchor has a
tapered distal face shaped to dissect the tissue of the
myocardium.
19. The lead attachment system of claim 14 wherein the stylet has a
pointed distal end shaped to dissect the tissue of the
myocardium.
20. A method for using a delivery instrument to implant a
myocardial lead into the heart, said lead having at least a first
electrode, the method comprising: mating a myocardial anchor
coupled to a tether to a distal end of the delivery instrument;
advancing the distal end of the delivery instrument through a tract
in the heart; deploying the anchor into the heart; withdrawing the
delivery instrument through the tract in such a manner that the
tether extends through the tract; threading a myocardial lead onto
the tether; and advancing the lead over the tether into the
heart.
21. The method of claim 20 further comprising: advancing the anchor
through the epicardium, into the myocardium, and back through the
epicardium; and deploying the anchor mechanism on the epicardial
surface.
22. The method of claim 20 further comprising: advancing the anchor
through the epicardium, into the myocardium and through the
endocardium; and deploying the anchor on the endocardial
surface.
23. The method of claim 20 further comprising: advancing the anchor
through the epicardium and into the myocardium; and deploying the
anchor into the myocardium.
24. The method of claim 20 further comprising: advancing the anchor
into the pericardium and out of the pericardium without traversing
the epicardium; and deploying the anchor on the pericardial
surface.
25. The method of claim 20 further comprising advancing the lead
body until the first electrode is in contact with the heart.
26. The method of claim 20 further comprising advancing the lead
body until the first electrode is in contact with the
myocardium.
27. The method of claim 26 wherein the lead body includes a second
electrode proximal to the first electrode and further comprising
advancing the lead body until the second electrode is at least
partially in contact with the heart.
28. The method of claim 27 further comprising advancing the lead
body until the second electrode straddles the epicardium.
29. The method of claim 27 further comprising advancing the lead
body until the second electrode is in contact with the
myocardium.
30. The method of claim 20 further comprising: forming a working
channel and a visual channel to the heart with an endoscopic probe;
and advancing the anchor and delivery instrument to the heart
through the working channel.
Description
CROSS REFERENCES
[0001] The present application claims the benefit of the following
U.S. Provisional Applications: application Ser. No. 60/514,037
filed Oct. 24, 2003, entitled "Absorbable Myocardial Lead Fixation
System", application Ser. No. 60/514,665 filed Oct. 27, 2003,
entitled "Lead Electrode Arrangement for Myocardial Leads",
application Ser. No. 60/514,042 filed Oct. 24, 2003, entitled
"Tapered Tip for Myocardial Lead", application Ser. No. 60/514,714
filed Oct. 27, 2003, entitled "Minimally-Invasive Fixation Systems
for Over-the-Tether Myocardial Leads", application Ser. No.
60/514,039 filed Oct. 24, 2003, entitled "Distal or Proximal
Fixation of Over-the-Suture Myocardial Leads", application Ser. No.
60/514,146 filed Oct. 24, 2003, entitled "Myocardial Lead with
Fixation Mechanism", application Ser. No. 60/514,038 filed Oct. 24,
2003 entitled "Delivery Instrument for Myocardial Lead Placement"
and application Ser. No. 60/514,713 filed Oct. 27, 2003, entitled
"Drug-Eluting Myocardial Leads", all of which are incorporated
herein by reference.
[0002] Reference is hereby made to the following commonly assigned
U.S. patent application Ser. No. 10/821,421, filed Apr. 9, 2004,
entitled "Cardiac Electrode Anchoring System" and the following
commonly assigned U.S. Patent applications filed on an even date
herewith, all of which are incorporated herein by reference:
application Ser. No. ______, entitled "Myocardial Lead",
application Ser. No. ______ entitled "Distal or Proximal Fixation
of Over-the-Tether Myocardial Leads", application Ser. No. ______,
entitled "Myocardial Lead with Fixation Mechanism" and application
Ser. No. ______, entitled "Absorbable Myocardial Lead Fixation
System."
FIELD OF THE INVENTION
[0003] This invention relates generally to implantable lead
assemblies for stimulating and/or sensing electrical signals in
muscle tissue. More particularly, it relates to myocardially
implanted leads for cardiac stimulation and systems for anchoring
the leads.
BACKGROUND OF THE INVENTION
[0004] Cardiac rhythm management systems are used to treat heart
arrhythmias. Pacemaker systems are commonly implanted in patients
to treat bradycardia (i.e., abnormally slow heart rate). A
pacemaker system includes an implantable pulse generator and leads,
which form the electrical connection between the implantable pulse
generator and the heart. An implantable cardioverter defibrillator
("ICD") is used to treat tachycardia (i.e., abnormally rapid heart
rate). An ICD also includes a pulse generator and leads that
deliver electrical energy to the heart.
[0005] The leads coupling the pulse generator to the cardiac muscle
are commonly used for delivering an electrical pulse to the cardiac
muscle, for sensing electrical signals produced in the cardiac
muscle, or for both delivering and sensing. The leads are
susceptible to categorization according to the type of connection
they form with the heart. An endocardial lead includes at least one
electrode at or near its distal tip adapted to contact the
endocardium (i.e., the tissue lining the inside of the heart). An
epicardial lead includes at least one electrode at or near its
distal tip adapted to contact the epicardium (i.e., the tissue
lining the outside of the heart). Finally, a myocardial lead
includes at least one electrode at or near its distal tip inserted
into the heart muscle or myocardium (i.e., the muscle sandwiched
between the endocardium and epicardium). Some leads have multiple
spaced apart distal electrodes at differing polarities and are
known as bipolar type leads. The spacing between the electrodes can
affect lead performance and the quality of the electrical signal
transmitted or sensed through the heart tissue.
[0006] The lead typically consists of a flexible conductor
surrounded by an insulating tube or sheath that extends from the
electrode at the distal end to a connector pin at the proximal end.
Endocardial leads are typically delivered transvenously to the
right atrium or ventricle and commonly employ tines at a distal end
for engaging the trabeculae.
[0007] The treatment of congestive heart failure ("CHF"), however,
often requires left ventricular stimulation either alone or in
conjunction with right ventricular stimulation. For example,
cardiac resynchronization therapy ("CRT") (also commonly referred
to as biventricular pacing) is an emerging treatment for heart
failure, which requires stimulation of both the right and the left
ventricle to increase cardiac output. Left ventricular stimulation
requires placement of a lead in or on the left ventricle near the
apex of the heart. One technique for left ventricular lead
placement is to expose the heart by way of a thoracotomy. The lead
is then positioned so that one or more electrodes contact the
epicardium or are embedded in the myocardium. Another method is to
advance an epicardial lead endovenously into the coronary sinus and
then advance the lead through a lateral vein of the left ventricle.
The electrodes are positioned to contact the epicardial surface of
the left ventricle.
[0008] The left ventricle beats forcefully as it pumps oxygenated
blood throughout the body. Repetitive beating of the heart, in
combination with patient movement, can sometimes dislodge the lead
from the myocardium. The electrodes may lose contact with the heart
muscle, or spacing between electrodes may alter over time.
[0009] There is a need for an improved myocardial pacing lead
suitable for chronic implantation and a minimally invasive delivery
system and method for implanting such a lead.
SUMMARY OF THE INVENTION
[0010] The present invention, according to one embodiment, is a
myocardial lead attachment system for securing a distal end of a
lead within a myocardium of a patient's heart. The system includes
an anchor, a tether coupled to the anchor and a delivery instrument
for receiving the anchor and advancing the anchor through a tract
in the heart from a proximal entrance site to a distal exit site in
such a manner that the tether extends proximally from the anchor
through the tract. The delivery instrument includes a needle having
a distal tip and a nest positioned proximal to the distal tip that
is sized to receive the anchor and an ejection mechanism for
ejecting the anchor from the nest.
[0011] The present invention, according to another embodiment, is a
myocardial lead attachment system for securing a distal end of a
lead within a myocardium of a patient's heart. The system includes
an anchor having a longitudinal bore extending therethrough, a
tether coupled to the anchor and a delivery instrument for
receiving the anchor and advancing the anchor through a tract in
the heart from a proximal entrance site to a distal exit site in
such a manner that the tether extends proximally from the anchor
through the tract. The delivery instrument includes a needle having
a proximal end, a distal end formed with a nest for receiving the
anchor and a central lumen extending therethrough. The delivery
instrument further includes a stylet slidably received in the
needle lumen and the anchor bore and an ejector plug formed on the
stylet for engaging the anchor.
[0012] The present invention, according to another embodiment, is a
method for using a delivery instrument to implant a myocardial lead
having at least a first electrode with a delivery instrument into a
heart. A myocardial anchor coupled to a tether. is mated to a
distal end of the delivery instrument. The distal end of the
delivery instrument is advanced through a tract in the heart. The
anchor is deployed into the heart. The delivery instrument is
withdrawn through the tract in such a manner that the tether
extends through the tract. A myocardial lead is threaded onto the
tether. The lead is advanced over the tether into the heart.
[0013] This summary is not intended to describe each embodiment or
every implementation of the present invention. Advantages and a
more complete understanding of the invention will become apparent
upon review of the detailed description and claims in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic view of a portion of the vasculature
and a myocardial lead attachment system according to one embodiment
of the present invention.
[0015] FIG. 2 is a side view of a delivery instrument for use in
conjunction with the myocardial lead attachment system of FIG. 1
according to one embodiment of the present invention.
[0016] FIG. 3A is a side view of a distal portion of the delivery
instrument of FIG. 2 according to one embodiment of the present
invention.
[0017] FIG. 3B is a side view of the distal portion of the delivery
instrument of FIG. 2 according to another embodiment of the present
invention.
[0018] FIG. 3C shows a side sectional view of the distal portion of
the delivery instrument shown in FIG. 3A.
[0019] FIG. 3D is a perspective view of the distal portion of the
delivery instrument shown in FIG. 3A.
[0020] FIG. 4A is a sectional view of a proximal portion of the
delivery instrument of FIG. 2 according to one embodiment of the
present invention.
[0021] FIG. 4B is a perspective view of a distal portion of the
delivery instrument of FIG. 2 according to one embodiment of the
present invention.
[0022] FIG. 4C is a partial sectional view of a distal portion of
the delivery instrument of FIG. 2 according to another embodiment
of the present invention.
[0023] FIG. 5A is a side view of an adjustable length delivery
instrument in an extended position according to one embodiment of
the present invention.
[0024] FIG. 5B is a side view of the delivery instrument of FIG. 5A
in a retracted position.
[0025] FIG. 6 is a sectional side view of a portion of an
adjustable length delivery instrument according to another
embodiment of the present invention.
[0026] FIG. 7 is a sectional view of a distal portion of a delivery
instrument for use in conjunction with the myocardial lead
attachment system of FIG. 1 according to one embodiment of the
present invention.
[0027] FIG. 8 is a sectional view of a distal portion of a delivery
instrument for use in conjunction with the myocardial lead
attachment system of FIG. 1 according to another embodiment of the
present invention.
[0028] FIG. 9 is a sectional view of a distal portion of a delivery
instrument for use in conjunction with the myocardial lead
attachment system of FIG. 1 according to still another embodiment
of the present invention.
[0029] FIG. 10 is a sectional side view of a distal portion of a
delivery instrument for use in conjunction with the myocardial lead
attachment system of FIG. 1 according to yet another embodiment of
the present invention.
[0030] FIG. 11 is a sectional side view of a distal portion of a
delivery instrument for use in conjunction with the myocardial lead
attachment system of FIG. 1 according to another embodiment of the
present invention.
[0031] FIG. 12 is a side view of a distal portion of a delivery
instrument for use in conjunction with the myocardial lead
attachment system of FIG. 1 according to still another embodiment
of the present invention.
[0032] FIG. 13 is a side view of a delivery instrument for use in
conjunction with the myocardial lead attachment system of FIG. 1
according to another embodiment of the present invention.
[0033] FIG. 14 is a side view of a delivery instrument for use in
conjunction with the myocardial lead attachment system of FIG. 1
according to another embodiment of the present invention.
[0034] FIG. 15A is a sectional view of the heart schematically
illustrating the use of a delivery instrument in conjunction with a
myocardial lead attachment system in an epicardial-epicardial
procedure according to one embodiment of the present invention.
[0035] FIG. 15B is a sectional view of the heart schematically
illustrating the use of a delivery instrument in conjunction with a
myocardial lead attachment system in an epicardial-endocardial
configuration according to one embodiment of the present
invention.
[0036] FIG. 15C is a sectional view of a portion of the heart
schematically illustrating the use of a delivery instrument in
conjunction with a myocardial lead attachment system in an
intra-myocardial procedure according to another embodiment of the
present invention.
[0037] FIG. 15D is a sectional view of a portion of the heart
schematically illustrating the use of a delivery instrument in
conjunction with a myocardial lead attachment system in a
pericardial-pericardial procedure according to yet another
embodiment of the present invention.
[0038] FIG. 16A is a sectional view of a portion of the heart and a
schematically illustrated distal portion of a myocardial lead
attachment system having a unipolar electrode arrangement according
to one embodiment of the present invention.
[0039] FIG. 16B is a sectional view of a portion of the heart and a
schematically illustrated distal portion of a myocardial lead
attachment system having a pseudo-unipolar electrode arrangement
according to one embodiment of the present invention.
[0040] FIG. 16C is a sectional view of a portion of the heart and a
schematically illustrated distal portion of a myocardial lead
attachment system having a pseudo-unipolar electrode arrangement
according to yet another embodiment of the present invention.
[0041] FIG. 16D is a sectional view of a portion of the heart and a
schematically illustrated distal portion of a myocardial lead
attachment system having a pseudo-unipolar electrode arrangement
according to still another embodiment of the present invention.
[0042] FIG. 16E is a sectional view of a portion of the heart and a
schematically illustrated distal portion of a myocardial lead
attachment system having a bipolar electrode arrangement according
to another embodiment of the present invention.
[0043] While the invention is amenable to various modifications and
alternative forms, specific embodiments have been shown by way of
example in the drawings and are described in detail below. The
intention, however, is not to limit the invention to the particular
embodiments described. On the contrary, the invention is intended
to cover all modifications, equivalents, and alternatives falling
within the scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION
[0044] FIG. 1 shows a myocardial lead attachment system 10 deployed
in a human heart 12 according to one embodiment of the present
invention. The heart 12 includes a right atrium 14 and a right
ventricle 16 separated from a left atrium 18 and a left ventricle
20 by a septum 22. During normal operation of the heart 12,
deoxygenated blood is fed into the right atrium 14 through the
superior vena cava 24 and the inferior vena cava 26. The
deoxygenated blood flows from the right atrium 14 into the right
ventricle 16. The deoxygenated blood is pumped from the right
ventricle 16 into the lungs, where the blood is re-oxygenated. From
the lungs the oxygenated blood flows into the left atrium 18, then
into the left ventricle 20. The left ventricle 20 beats forcefully
to pump the oxygenated blood throughout the body.
[0045] The outer walls of the heart 12 are lined with a tissue
known as the epicardium 28. The inner walls of the heart are lined
with a tissue known as the endocardium 30. The heart muscle, or
myocardium 32, is sandwiched between the endocardium 30 and the
epicardium 28. A tough outer pericardial sac 33 surrounds the heart
12.
[0046] The myocardial lead attachment system 10 includes a pulse
generator 34 coupled to a myocardial lead 36. The pulse generator
34 is typically implanted in a pocket formed, underneath the skin
of the patient's chest or abdominal region. The lead 36 extends
from the pulse generator 34 to the heart 12 and is implanted in the
myocardium 32 near an apex 38 of the heart 12. The lead 36 delivers
electrical signals from the pulse generator 34 to an electrode
located at or near a distal tip to accomplish pacing of the heart
12 (not shown in FIG. 1). An anchor mechanism 44 is coupled to the
lead 36 via a tether 45 to secure the lead 36 to the heart 12 and
to retain the electrode in a chosen location.
[0047] According to one embodiment, and generally shown in the
following figures, the anchor mechanism 44 is an elongated T-bar,
in which the tether 45 is coupled to the anchor mechanism 44
between its opposite ends and preferably at a mid-point to form the
"T". According to other embodiments, the anchor mechanism 44 has
any other shape suitable for forming an anchor against the heart 12
to retain the lead 36 in the desired location. An important feature
of the anchor mechanism 44 is that its shape is configured to
engage the heart tissue following implantation through a tract (not
visible in FIG. 1) in the heart 12 to reduce the likelihood of
re-entry of the anchor mechanism 44 into the tract. According to
one embodiment, the length of the anchor mechanism 44 is greater
than the diameter of the tract. The "T" configuration is such that
tension exerted on the mid-point of the anchor mechanism 44 via the
tether 45 tends to position the anchor mechanism 44 cross-wise over
the tract, preventing the anchor mechanism from siding proximally
through the tract. The lead 36 is then advanced over the tether 45
into the myocardium 32. The anchor mechanism 44 resists the
tensioning force exerted on the tether 45 such that the lead 36 may
be easily advanced through the tract.
[0048] Placement of the lead 36 and anchor mechanism 44 of FIG. 1
may be accomplished by exposing a portion of the heart 12, for
example by way of a sternotomy, thoracotomy or mini-thoracotomy.
According to other embodiments, the heart 12 may be accessed via an
endoscopic procedure according to known methods. Although shown
implanted near the apex 38, the lead 36 may be implanted in the
heart 12 anywhere pacing therapy is needed. The anchor mechanism 44
is delivered to the heart 12 with a delivery instrument according
to any of the following embodiments.
[0049] FIG. 2 shows a delivery instrument 50 according to one
embodiment of the present invention. The delivery instrument 50
includes a needle portion 58 having a distal tip 60 and a nest 62.
The nest 62 is sized to receive at least a portion of the anchor
mechanism 44 (not visible in FIG. 2). The delivery instrument 50
further includes an ejection mechanism 66 coupled to an actuator
(not visible in FIG. 2) for ejecting the anchor mechanism 44 from
the nest 62.
[0050] The delivery instrument 50 includes a handle 52 having a
proximal end 54 and a distal end 56. The needle portion 58 is
coupled to the handle 52 and extends from the distal end 56. The
needle portion 58 is of a hypotube construction with an internal
lumen 59. The handle 52 has an internal lumen 64 continuous with
the needle lumen 59. The ejection mechanism 66 is located on the
handle 52 and is operable within the internal lumen 64. According
to other embodiments, the ejection mechanism 66 is located
elsewhere on the handle 52.
[0051] The handle 52 is sized with a length a and diameter b for
easy grasping and manipulation. According to one embodiment of the
present invention, a diameter b of about 5 mm provides a mechanical
advantage allowing stable control over the direction of the distal
needle tip 60. Further, a diameter b of about 5 mm can be used
within a standard 7 mm or larger thoracic port, which is commonly
used in minimally-invasive thoracoscopic procedures to access the
heart 12.
[0052] An outer surface 70 of the handle 52 includes a surface
feature 68. Surface feature 68 may include bumps, ribs, or bulging
features on the outer surface 70 chosen to enhance the friction
between the handle 58 and the surgeon's hand. Surface feature 68
advantageously reduces slippage between the surgeon's hand and the
handle 52 while in wet, slippery environments. The handle 52 can be
made of any sterilizable metal or polymeric material, including
stainless steel, polypropylene, and polyurethane.
[0053] The shape of the distal needle portion 58 is configured to
facilitate access to the heart 12 via thoracotomy or other
procedures, such as those mentioned above. According to one
embodiment of the present invention, the needle portion 58 is
shaped with a curved portion 72. The shape of the curved portion 72
will be dictated in part by patient anatomy (e.g., overall heart
size, peculiarities in geometry due to dilation, epicardial fat,
infarct, and vessels), location of the thoracotomy (posterior or
anterior to an imaginary mid-axillary line bisecting the heart 12),
and size of the incision into the heart tissue. According to one
embodiment, the curved portion 72 has a radius of curvature
R.sub.72 of about 22 mm, a shape intended to be approximately what
the physician would need for implanting the lead 36 via a
thoracotomy. According to other embodiments, the radius of
curvature R.sub.72 of curved portion 72 is from about 10 to about
35 mm (not shown). According to other embodiments, the curved
portion 72 is constructed of multiple curved segments, or is
straight (not shown).
[0054] According to one embodiment, the needle portion 58 is
constructed of stainless steel. The curved portion 72 may be formed
according to a variety of methods. The curved portion 72 may be
formed by mechanically bending the needle portion 58. Alternately,
the needle portion 58 is heat-set so that the needle portion 58, or
a smaller portion thereof, is malleable. A chosen curvature can be
imparted to the needle portion 58 contemporaneous with the
implantation procedure according to the surgeon's needs.
[0055] FIG. 3A shows a portion of the needle portion 58 according
to one embodiment of the present invention. The tip 60 and nest 62
are shown as previously described. A distal end 60b of the tip 60
is configured to minimize trauma to the myocardium 32 during
insertion. This is accomplished by dissecting the myocardium 32 as
opposed to cutting the myocardium 32. According to one embodiment,
the tip 60 is generally conical in shape, terminating at a slightly
rounded point.
[0056] FIG. 3B shows another embodiment in which the distal end 60b
of the tip 60 is more rounded or blunt than the embodiment shown in
FIG. 3A. A rounded or blunted tip 60 is understood to be less
traumatic and less likely to damage coronary vessels when passing
through the myocardium 32. According to one embodiment, the tip 60
is generally isodiametric. An isodiametric configuration generally
exerts force equally on the myocardial tissue 32 about the tip 60
when passing through tissue. A uniform force distribution reduces
excessive force on the myocardial tissue 32 in directions other
than along the axis of dissection. According to other embodiments,
the tip 60 is provided with a sharp cutting edge.
[0057] The nest 62 is sized with a length d and a width e chosen
such that the nest 62 retains the anchor mechanism 44 when the
needle portion 58 is advanced through the myocardium 32 (anchor
mechanism 44 not visible in FIGS. 3A and 3B--see FIG. 3D).
According to one embodiment, the nest 62 is an elongated slot in
the needle portion 58 opening to the needle lumen 59. The nest 62
further includes a tether slot 78 located near its proximal end.
The tether slot 78 is adapted to accept the tether 45 when the
needle portion 58 is advanced through the myocardium 32 (See FIG.
3D).
[0058] FIG. 3C shows the needle portion 58 of FIG. 3A. A proximal
end 60a of the tip 60 is sized with a diameter c chosen to mate
with the needle lumen 59. The nest 62 includes a distal angled face
or ramp 76 facing the interior of the nest 62. The. ramp 76 is
disposed at an angle .theta. relative to a longitudinal axis 77 of
the needle 58.
[0059] FIG. 3D shows the anchor mechanism 44 received in the nest
62. The anchor mechanism 44 is placed in the slot 62 and slid
proximally into the needle lumen 59. The tether 45 is received in
the tether slot 78, permitting the anchor mechanism 44 to be slid
further into the lumen 59. The ramp 76 is inclined away from the
anchor mechanism 44 at the angle .theta. at distal sliding of the
anchor mechanism 44 along the axis 77 causes the anchor mechanism
44 to ride up the ramp 76 and out of the nest 62.
[0060] FIG. 4A shows a proximal portion of the handle 52 and FIG.
4B shows a distal portion of the needle portion 58, both detailing
the ejection mechanism 66. The ejection mechanism 66 includes an
elongated member 80 extending from the proximal end 54 of the
handle 52, through the handle lumen 64 and needle lumen 59, and
terminating proximal to the nest 62. A proximal end 82 of the
elongated member 80 is operationally coupled to an actuator 84.
According to one embodiment, the actuator 84 is a depressible
button operable to slide the elongated member 80 distally from a
neutral or retracted position to an advanced position. FIG. 4B
shows the elongated member 80 in an advanced position such that a
distal end 86 of the elongated member 80 has engaged the anchor
mechanism 44 and is pushing the anchor mechanism 44 distally within
the nest 62. Doing so forces the anchor mechanism 44 to slide
distally along the ramp 76 and out of the nest 62.
[0061] According to one embodiment, shown in FIGS. 4A and 4B, the
elongated member 80 is a solid tubular member sufficiently flexible
to navigate the curved portion 72 (see FIG. 2) of the needle
portion 58. According to another embodiment, as shown in FIG. 4C,
the elongated member 80 is constructed of a combination of a solid
member 88 and a helically-wound member 89. The solid member 88
extends through the needle lumen 59 to the curved portion 72 and
transfers axial force to the distally positioned helical member 89,
which extends through the needle lumen 59 at the curved portion 72.
The helical member 89 is sufficiently flexible to navigate the
curved portion 72, while the solid member 88 may be rigid.
According to other embodiments, the elongated member 80 is a rigid
member. Elongated member 80 may be constructed of a polymer or
metal.
[0062] Returning to FIG. 4A, the handle lumen 64 is formed with a
ledge 90 forming a mechanical stop. The ledge 90 blocks actuation
of the actuator 84 (i.e. further depression of the button), and
prevents over-advancement of the elongated member 80. A biasing
mechanism 92, including a resilient member 93, such as a spring, is
interposed between the actuator 84 and the handle 52. The biasing
mechanism 92 biases the actuator 84 to a neutral position in which
the elongated member 80 is retracted.
[0063] According to one embodiment, the ejection mechanism 66 and
actuator 84 are operable to advance the elongated member 80 to one
of a plurality of pre-set positions. According to another
embodiment, the present invention is an automatic or semi-automatic
delivery instrument. In this embodiment a lever mechanism, or
trigger and spring mechanism, drives the needle portion 58 from a
retracted position into the myocardium 32 in a prescribed path,
ejects the anchor mechanism 44 and retracts the needle portion 58
to its original position.
[0064] FIGS. 5A and 5B show a delivery instrument 50' which is
generally similar to the delivery instrument 50 shown FIG. 2. The
length of the needle portion 58' of the instrument 50' extending
from the handle 52' is adjustable by sliding portions of the needle
portion 58' into the handle lumen 64'. In one embodiment, needle
portion 58' is retained in a chosen position within the handle
lumen 64' via a keeper mechanism, such as a set screw 94',
extending through the handle 52'. If the physician desires more
needle length, N, as shown in FIG. 5A, either for patients with
thick thoracic walls requiring a deeper reach to the epicardium 28
or for thoracoscopic procedures, he may adjust accordingly. If he
requires less length N', as shown in FIG. 5B, the needle portion
58' may be retracted into the lumen 64'.
[0065] FIG. 6 shows another embodiment of the adjustable length
delivery instrument 50' in which the needle portion 58' is
adjustably coupled to the handle 52' via a collet mechanism 95'.
According to one embodiment, the needle portion 58' is provided
with a sleeve 96' having an open end 96a' facing proximally and a
distal end 96b' coupled to the needle portion 58' via guide member
98'. The sleeve 96' is sized to receive the distal end 56' of the
handle 52'. The sleeve 96' and the distal end 56' of the needle 52'
are provided with complementary threads 97'. Rotation of the sleeve
96' about the handle threads 98' advances the sleeve 96' onto the
handle 52', shortening the effective length of the needle portion
58'. Reverse rotation advances the needle portion 58' distally from
the handle 52', increasing the effective length of the needle 58'.
According to other embodiments, the needle 58' and handle 52' may
be provided with complementary teeth or other means for providing
an adjustable length coupling.
[0066] FIG. 7 shows a delivery instrument 100 for use in
conjunction with the myocardial lead attachment system 10 of FIG. 1
according to another embodiment of the present invention. The
instrument 100 includes a tube or needle 102 having a nest 106 for
receiving an anchor mechanism 108, and an ejection mechanism 109
for ejecting the anchor mechanism 108 from the nest 106. A proximal
portion of the needle 102 may be attached to a handle to facilitate
manipulation (not shown).
[0067] According to the present embodiment, the nest 106 is an open
sleeve at a distal end of the needle 102. The anchor mechanism 108
is received in the nest 106 and protrudes outwardly from the nest
106. The needle 102 includes a crimp or detent 110 near to and
proximal to the nest 106 for contacting a proximal or trailing edge
112 of the anchor mechanism 108. An inside diameter f of the nest
106 is slightly greater than an outside diameter g of the anchor
mechanism 108, such that the anchor mechanism 108 can readily
release from the nest 106 upon application of a relatively small
force on the anchor mechanism 108 directed distally from the needle
102. The anchor mechanism 108 is coupled to a tether 113 as
previously described. The needle 102 is further provided with a
central lumen 114 extending therethrough.
[0068] The ejection mechanism 109 is a stylet 115 coupled to an
ejection plug 116. The stylet 115 has a sharpened distal tip 117
shaped to effectively dissect the tissue of the myocardium 32.
According to other embodiments, the tip 117 is blunt or rounded to
reduce trauma to the myocardium 32. The stylet 115 extends through
the needle lumen 114 and through a bore 118 extending
longitudinally through the anchor mechanism 108. The ejector plug
116 is spherical and is sized and shaped smaller than an inside
diameter h of the needle 102 at the crimp 110 so as to pass through
the crimp 110 but larger than an inside diameter I of the bore 118
in the anchor mechanism 108 so as to contact the trailing edge 112
of the anchor mechanism 108. According to other embodiments, the
ejector plug 116 has a cylindrical or other shape. According to
still other embodiments, the ejector plug 116 is not formed
integrally with the stylet 115 but rather is a separate member such
as a clip that is affixed to the stylet 115.
[0069] During implantation, the anchor mechanism 108 is received in
the nest 106. The tip 117 of the stylet 115 extends through the
bore 118 in the anchor mechanism 108 and protrudes from the bore
118. The tube 102 and the stylet 115 are used to guide the anchor
mechanism 108 through the myocardium 32. The crimp 110 contacts the
trailing edge 112 of the anchor mechanism 108 to force the anchor
mechanism 108 through the myocardium 32. Once the anchor mechanism
108 emerges from the myocardium 32, the ejection mechanism 109 is
actuated by advancing the stylet 115 distally with respect to the
tube 102, such that the ejection plug 116 contacts the trailing end
112 of the anchor mechanism 108 and ejects the anchor mechanism 108
from the nest 106. This deploys the anchor mechanism 108 on the
surface of the heart 12. The needle 102 and stylet 115 are then
withdrawn.
[0070] According to one embodiment, the ejection mechanism 109 is
coupled to an actuator as described with respect to the embodiment
shown generally in FIGS. 2-6 to distally advance the stylet 106
(not shown). According to other embodiments, the ejection mechanism
109 is actuated by manually advancing the stylet 115 with respect
to the needle 102.
[0071] FIG. 8 shows a distal portion of delivery instrument 120
according to another embodiment of the present invention. As shown
in FIG. 8, the instrument 120 includes many of the same components
as the delivery instrument 100 of FIG. 7. The instrument 120
includes a tube or needle 122 having a nest 123, an ejection
mechanism 124 including a stylet or guide wire 126 and an anchor
mechanism 128 coupled to a tether 130. The instrument 120 does not
include a crimp or detent 110 as described with respect to
instrument 100 of FIG. 7, but instead includes a ledge 132 forming
an internal stop in the needle 122 proximal to the nest 123. The
ledge 132 contacts a trailing edge 134 of the anchor mechanism 128
to drive the anchor 128 forward during implantation. The outer
profile of the needle 102 is smooth and continuous.
[0072] The stylet 126 is provided with an ejector plug 136 as
described previously. According to the present embodiment, however,
the ejector plug 136 is cylindrical in shape. According to the
embodiment shown, the anchor mechanism 128 includes an angled or
tapered leading edge 138. Tapered edge 138 facilitates dissection
of the myocardium 32 during implantation. The leading edge 138 of
the anchor mechanism 128 may have a blunt or rounded profile
similar to the profile of the needle tip 60 described with
reference to the embodiment shown in FIGS. 3A and 3B. The
instrument 120 is used in a similar manner as described above with
reference to the embodiment shown in FIG. 7.
[0073] FIG. 9 shows a sectional view of a distal portion of a
stylet delivery instrument 140 according to another embodiment of
the present invention. The instrument 140 includes many of the same
components as the delivery instruments 100 and 120 of FIGS. 7 and
8. The instrument 140 includes a tube or needle 142 having a nest
143 and an ejection mechanism 144. The ejection mechanism 144 is a
stylet or guide wire 146 having an ejector plug 145 as described
previously. An anchor mechanism 148 having a stepped outside
diameter is received in the nest 143. A distal portion 150 of the
anchor mechanism 148 has a diameter j that is roughly equal to an
outside diameter k of the needle 142. A proximal portion 152 of the
anchor mechanism 148 has a diameter l slightly smaller than an
inside diameter m of the needle 142, such that the anchor mechanism
148 can be inserted into the nest 143. In this embodiment, a
leading edge 154 of the tube 142 serves to contact the anchor
mechanism 148 and transmit axial force during implantation. In this
embodiment, the anchor 148 may include either a blunt or a tapered
leading edge 156 as described previously. The instrument 140 is
used in the manner described above with reference to FIG. 7.
[0074] FIG. 10 shows a sectional view of a distal portion of a
delivery instrument 160 according to another embodiment of the
present invention. The instrument 160 includes a stylet 162 and an
anchor mechanism 164. The stylet 162 includes a distal tip 166,
which is shaped for efficient dissection of the myocardium 32. A
distal end 168 of the stylet 162 is provided with a raised region
170 forming a mechanical stop. According to one embodiment, a
tubular sleeve 172 is positioned about the stylet 162 to form the
raised region 170. According to other embodiments the raised region
170 is integrally formed with the stylet 162. The anchor mechanism
164, which is coupled to a tether 174, has an inner bore 176
extending therethrough. An inner surface of the bore 176 includes a
ledge 178. A distal end 168 of the stylet 162 is received in the
bore 176, such that the tip 166 protrudes from the bore 176. The
ledge 178 is adapted to mate with and contact the raised region 170
of the stylet 162 such that upon application of an axial force on
the stylet 162, the raised region 170 contacts the ledge 178 and
forces the anchor mechanism 164 to advance distally.
[0075] The instrument 160 is advanced through the heart 12, and the
stylet 162 is manipulated into the heart 12 and position the anchor
mechanism 164. When the anchor mechanism 164 has been properly
positioned, the stylet 162 is withdrawn.
[0076] FIG. 11 shows a sectional view of a distal portion of a
stylet delivery instrument 180 according to another embodiment of
the present invention. The instrument 180 includes a stylet 182 and
an anchor mechanism 184. The anchor mechanism 184 includes a blind
bore 186 extending from a proximal end 188 of the anchor mechanism
184 but not all the way through to a distal end 190. The inner
surface of the blind bore 186 has a diameter sized to receive a
distal end 192 of the stylet 182. As shown, the anchor 184 has a
tapered leading edge 194 to facilitate dissection of the myocardium
32. A tether 196 is attached to the anchor 184. The stylet 182 is
used to advance the anchor mechanism 184 through the myocardium 32.
When the anchor mechanism 184 is located in a chosen position, for
example, on the endocardial surface 30, the stylet 182 is
withdrawn.
[0077] FIG. 12 shows a side view of a stylet delivery instrument
200 according to another embodiment of the present invention. The
instrument 200 includes a guide wire or stylet 202 and an anchor
mechanism 204 coupled to a tether 206. The stylet 202 includes a
tapered tip 208 shaped for efficient dissection of the myocardium
32. The anchor mechanism 204 is coupled to a catch mechanism 210
for receiving the stylet 202. The catch mechanism 210 is a
ring-shaped member and may be formed from a looped region of the
tether 206 or formed separately and attached to the anchor
mechanism 204. According to one embodiment, the catch mechanism 210
is generally flexible. According to another embodiment, the catch
mechanism 210 is rigid.
[0078] The catch mechanism 210 has an inner diameter smaller than
an outside diameter n of the stylet 202, such that the stylet tip
208 can be inserted partially into the catch mechanism 210, but the
stylet 202 cannot fully pass through the catch mechanism 210. The
stylet tip 202 is inserted into the catch mechanism .210 so that
the anchor 204 lies adjacent the length of the stylet 202.
According to other embodiments, the stylet 202 is provided with a
circumferential groove for receiving the catch mechanism 210 (not
shown). The stylet 202 is inserted into the myocardium 32, drawing
the anchor mechanism 204 along via the catch mechanism 210. Once
the stylet tip 208 and the anchor mechanism 204 emerge from the
myocardium 32, the stylet 202 is withdrawn, disengaging from the
catch mechanism 210. Following implantation, the catch mechanism
210 may be removed or may be left in place.
[0079] FIG. 13 shows a delivery instrument 300 in accordance with
another embodiment of the present invention. The delivery
instrument 300 includes many of the features of the delivery
instrument 50 shown in FIGS. 2-6. In addition, the delivery
instrument 300 may be used for identifying an appropriate or
desired implant site. The delivery instrument 300 includes a handle
302, a needle 304, an anchor mechanism 306 and an ejection
mechanism 308 as previously described. According to the present
embodiment, the needle 304 is electrically conductive and extends
nearly to a proximal end 310 of the handle 302. The needle 304 is
electrically isolated or masked via a non-conductive insulating or
dielectric material polymer sleeve 311 extending the length of the
needle 304. According to one embodiment, the sleeve 311 is formed
of a heat shrinkable polyimide. According to other embodiments, the
sleeve 311 is formed of a conformal polymer such as parylene or
ethylene-tetrafluoro ethylene. According to another embodiment, the
needle 304 is coated with a layer of non-conductive polymer
material.
[0080] The needle 304 is electrically exposed at a distal tip 312
and at a proximal region 314. The proximal exposed region 314 is
accessible via a cut-out or window 316 formed in the handle 302.
The needle 304 acts as an electrical conductor between the exposed
proximal region 314 and the exposed distal tip 312. Alligator clips
or other electrical connectors may be coupled to the needle 304
through the window 316 to electrically couple the exposed distal
tip 312 to a pacing and sensing analyzer for performing sensing and
pacing functions (not shown).
[0081] The exposed area at tip 312 is brought into contact with the
epicardium 28 or myocardium 32 to perform sensing and pacing
functions prior to ejection of the myocardial anchor 306.
Additionally, acute therapeutic benefit at a particular site may be
assessed using said embodiment. If acute benefit is unacceptable,
the implant site may be changed prior to implanting the lead
36.
[0082] FIG. 14 shows a delivery instrument 400 according to another
embodiment of the present invention. The delivery instrument 400
includes a handle 402 coupled to a needle 404, an anchor mechanism
406 and an ejection mechanism 408 as previously described with
respect to various embodiments. In addition, the delivery
instrument 400 may be used for identifying an appropriate or
desired implant site. According to one embodiment, this is
accomplished by electrically isolating the needle region 404 except
for a small exposed or electrically active area 410 on the conical
tip 412. The needle region 404 may be electrically isolated
according to the techniques described with respect to the
previously described embodiment shown in FIG. 13. A conductive wire
414 with a terminal end 416 in electrical communication with the
electrically active area 410 is located in the handle 402. The wire
414 is connected to a pacing and sensing analyzer 418. The
electrically active area 410 is brought into contact with the
epicardium 28 or myocardium 32 to perform sensing and pacing as
previously described.
[0083] The systems shown in FIGS. 2-14 are amenable to
minimally-invasive introduction into the heart 12, such as by known
thoracoscopic, mini-thoracoscopic or endoscopic techniques. In one
embodiment employing an endoscopic technique, a small subxiphoid
incision is made to gain visualization of the apex 38 of the heart
12. The pericardium 33 is perforated to gain access to the
epicardial surface 28. An endoscopic probe having an open working
channel is then introduced into the chest. The endoscopic probe
includes common features such as a light tube, fiber optic
visualization, and means to accomplish distal deflections of the
tube or needle when formed of a malleable material as described
above.
[0084] A target region of the heart 12 is approached and advanced
sensing probes may be used to assess the suitability of the
location. This assessment may include typical measurements such as
pacing thresholds, sensing amplitudes, and tissue impedance. These
functions may be accomplished with a delivery instrument in
accordance with the embodiments shown in FIGS. 13 and 14. The
working channel may also be used to assess the physiological
suitability of the heart tissue. Temporary pacing of the heart 12
may also be performed at the location through the working
channel.
[0085] After a determination that the location is suitable for lead
implantation, an anchor mechanism 44 as is shown in FIG. 1 is
advanced through the working channel with a delivery instrument 50
as is shown in FIGS. 2-6 in accordance with one embodiment of the
present invention. A separate channel for fiber optic visualization
may be used to assist the operator in guiding the delivery
instrument 50 through the myocardial tissue 32. In one embodiment,
the visualization channel is further used to avoid tissue
structures, such as vessels, fat pads, nervous system tissue, and
infarcts.
[0086] FIGS. 15A -15D illustrate the use of the delivery instrument
50. The needle portion 58 of the delivery instrument 50 is used to
create a channel or tract 37 through the tissue of a patient's
heart 12. FIG. 15A shows an epicardial-epicardial procedure, in
which the needle portion 58 is inserted in the direction shown by
the arrow 99', such that it both enters and exits the myocardium 32
through the epicardium 28. According to one embodiment, the needle
tip 60 is rounded or blunt, as previously described to reduce
trauma to the myocardial tissue 32 during advancement. During
insertion through the myocardium 32, the anchor mechanism 44 is
located within the nest 62. A tether 45 is attached to the anchor
44 and extends along the outside of the needle portion 58 and the
handle 52.
[0087] FIG. 15B shows an epicardial-endocardial procedure, in which
the needle portion 58 travels in the path indicated by the arrow
99', such that it enters the myocardium 32 through the epicardium
28 and exits through the endocardium 30. Again, the anchor
mechanism 44 is located within the nest 62 and a tether 45 travels
along the outside of the needle portion 58 and handle 52.
[0088] FIG. 15C shows an intra-myocardial procedure, in which the
needle portion 58 travels in the path indicated by arrow 99', such
that it enters the myocardium 32 through the epicardium 28. The
anchor mechanism 44 is ejected into the myocardium 32 and the
delivery instrument 50 is withdrawn. The anchor mechanism 44
remains positioned within the myocardium 32.
[0089] FIG. 15D shows a pericardial-pericardial procedure, in which
the needle portion 58 travels in the path indicated by arrow 99'
such that it enters and exits through the pericardium 33 without
traversing the myocardium 32.
[0090] Once the delivery instrument 50 emerges through the
epicardium 28 (or the endocardium 30, pericardium 33, or myocardium
32), the ejection mechanism 66 is activated to dislodge the anchor
mechanism 44 from the nest 62. The delivery instrument 50 is then
withdrawn back through the tract 37 and removed. The tether 45 is
then tensioned to cause the anchor 44 to engage against the
epicardium 28 (or endocardium 30, pericardium 33 or myocardium
32).
[0091] According to other embodiments (see FIGS. 7-10C, but
referring generally to FIG. 7), a stylet or guide wire 106 in
combination with a needle 102 and an anchor mechanism 108 is used
to create the tract 37 through the myocardium 32 for delivery of
the anchor mechanism 108. Once the distal end of the needle 104 and
anchor mechanism 108 have emerged through the epicardium 28 (or
endocardium 30, the myocardium 32 or pericardium 33), the stylet
106 is advanced. The ejector plug 116 engages the trailing edge 112
of the anchor mechanism 108 to eject the anchor mechanism 108 from
the needle lumen 104. The needle 102 and stylet 106 are then
withdrawn through the tract 37.
[0092] According to still other embodiments (see FIGS. 11 and 12,
but referring generally to FIG. 11), a stylet or guide wire 182 in
combination with an anchor mechanism 184 is used to create the
tract 37 through the myocardium 32 for delivery of the anchor
mechanism 184. Once the distal end 192 of the stylet or guide wire
182 and anchor mechanism 184 have emerged through the epicardium 28
(or endocardium 30, myocardium 32 or pericardium 33) the stylet 182
is withdrawn. The anchor mechanism 184 remains in place. The tether
196 is tensioned and the lead 36 advanced as described above.
According to other embodiments, the stylet 182 and anchor mechanism
184 are advanced through the working channel rather than creating a
separate tract 37.
[0093] Following delivery of the anchor mechanism 44 to the
epicardial surface 28 (or the myocardium 32, the endocardial
surface 30 or the pericardial surface 33) according to any of the
aforementioned embodiments, the tether 45 is tensioned and the lead
36 advanced as described above. Following implantation of the
myocardial lead 36, the tether 45 is tensioned and secured to the
myocardial lead 36 to secure the myocardial lead 36 within the
myocardium 32. According to other embodiments, the myocardial lead
36 is provided with additional means to secure the myocardial lead
36 within the myocardium 32 following delivery.
[0094] The lead 36 is positioned in the heart 12 and anchored, as
described above, to position the lead electrode 40 in chosen
locations in the heart 12. Although generally shown in implanted
near the apex 38, the lead 36 may be implanted anywhere in the
heart pacing therapy is needed. For example, the lead 36 may be
implanted in the free wall of the left ventricle 20. According to
one embodiment, shown in FIG. 16A, the lead 36 is configured as a
unipolar lead. The electrode 40 is inserted into the heart tissue
and is an active "can." The electrode 40 may be positioned in the
myocardium 32, as shown, or may contact the epicardium 30 or the
pericardium 33.
[0095] FIG. 16B shows another embodiment in which the lead 36 has
two electrodes, a proximal anode 40a and a distal cathode 40b.
According to one embodiment, the lead 36 is implanted in a
pseudo-unipolar arrangement, such that the cathode 40b is
positioned within the myocardial tissue 32 and the anode 40a is
positioned on the lead body 36, but not in contact with the heart
tissue.
[0096] FIG. 16C shows another embodiment, in which the lead
electrode arrangement is pseudo-unipolar, such that the cathode 40b
is positioned in the heart and the anode 40a partially contacts the
exterior epicardial tissue 28 of the heart 12.
[0097] FIG. 16D shows yet another pseudo-unipolar embodiment in
which the cathode 40b is positioned in the myocardium 32 and the
anode 40a is positioned in alignment with the outer layers of the
epicardial tissue 28 of the heart 12. The anode 40a may, for
example, straddle the epicardium 28 such that a portion anode 40a
is within the heart tissue and another portion is exposed to a
space outside of the heart 12.
[0098] FIG. 16E shows another embodiment in which the lead 36 has a
bipolar arrangement wherein the cathode 40b and anode 40a are
completely within the myocardial tissue 32.
[0099] In one embodiment, the cathode 40b has an active electrode
surface area of about 1 square mm. The cathode 40b is located near
the distal tip 35 of the lead body 36. An electrode spacing between
the cathode 40b and anode 40a of more than about 2 cm would
generate a unipolar lead, as defined above. An electrode spacing of
between about 1 and about 2 cm would generate a pseudo-unipolar
lead, as defined above. An electrode spacing of less than about 1
cm would generate a bipolar lead, as defined above.
[0100] In the epicardium to epicardium configuration, the
epicardium to endocardium configuration and the intramyocardial
configuration, once implanted, the lead body 36 will serve to block
the tract in the myocardium 32 created by the delivery instrument
50 and prevent further loss of blood from the heart 12. If it
becomes necessary to reposition the lead 36 and create a second
tract, a porous, clot-promoting "plug" material can be fed over the
tether 45 into the tract 37 to serve as a seal. Following
implantation of the myocardial lead 36, the tether 45 is tensioned
and secured to the myocardial lead 36 to secure the myocardial lead
36 within the myocardium 32.
[0101] Various modifications and additions can be made to the
exemplary embodiments discussed without departing from the scope of
the present invention. Accordingly, the scope of the present
invention is intended to embrace all such alternative,
modifications, and variations as fall within the scope of the
claims, together with all equivalents thereof.
* * * * *