U.S. patent application number 10/781589 was filed with the patent office on 2004-08-19 for medical electrical lead having bending stiffnesses which increase in the distal direction.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Smits, Karel F.A..
Application Number | 20040162601 10/781589 |
Document ID | / |
Family ID | 23786079 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040162601 |
Kind Code |
A1 |
Smits, Karel F.A. |
August 19, 2004 |
Medical electrical lead having bending stiffnesses which increase
in the distal direction
Abstract
An elongated coronary vein lead having a variable stiffness lead
body and most preferably adapted to be advanced into a selected
coronary vein for delivering a pacing or defibrillation signal to a
predetermined region of a patient's heart, such as the left
ventricle is disclosed. A method of pacing and/or defibrillating a
patient's heart using the lead is also described. The method of
pacing or defibrillating the heart includes advancing the coronary
vein lead through both the coronary sinus and into a selected
coronary vein of a patient's heart, connecting the lead to an
electrical pacing source and applying electrical stimulation to a
particular chamber of the patient's heart via the implanted lead.
The lead includes a variable stiffness lead body that enhances the
ability of the lead to be retained in a coronary vein after the
lead has been implanted therein.
Inventors: |
Smits, Karel F.A.;
(Munstergeleen, NL) |
Correspondence
Address: |
MEDTRONIC, INC.
710 MEDTRONIC PARKWAY NE
MS-LC340
MINNEAPOLIS
MN
55432-5604
US
|
Assignee: |
Medtronic, Inc.
|
Family ID: |
23786079 |
Appl. No.: |
10/781589 |
Filed: |
February 17, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10781589 |
Feb 17, 2004 |
|
|
|
09947060 |
Sep 6, 2001 |
|
|
|
6718211 |
|
|
|
|
09947060 |
Sep 6, 2001 |
|
|
|
09449936 |
Nov 29, 1999 |
|
|
|
6549812 |
|
|
|
|
Current U.S.
Class: |
607/125 |
Current CPC
Class: |
A61N 2001/0585 20130101;
A61N 1/056 20130101 |
Class at
Publication: |
607/125 |
International
Class: |
A61N 001/05 |
Claims
I claim:
1. An elongated implantable medical electrical lead for
electrically stimulating a human heart or sensing electrical
signals originating therefrom, comprising: (a) a lead body having
proximal and distal sections; (b) at least one electrode for
sensing or electrically stimulating the heart; (c) a proximal end
comprising an electrical connector, the electrical connector being
contiguous with the proximal section of the lead body; (d) a distal
end contiguous with the distal section of the lead body; (e) at
least one electrical conductor having proximal and distal ends, the
distal end of the conductor being operatively connected to the at
least one electrode, the proximal end of the conductor being
operatively connected to the electrical connector; wherein the
distal section of the lead body comprises at least first and second
segments, the first segment having a bending stiffness S.sub.bs
which exceeds the bending stiffness S.sub.bf of the second segment,
the first and second segments being configured and dimensioned to
impart a distally directed force to the distal end of the lead when
the first and second segments are subjected to a bending moment
resulting in a sufficient curvature of the distal section of the
lead body.
2. The medical electrical lead of claim 1, wherein the ratio of the
bending stiffness of the first segment (S.sub.bs) in respect of the
second segment (S.sub.bf) is defined by the equation: 3 1.5 S bs S
bf 100
3. The medical electrical lead of claim 1, wherein the ratio of the
bending stiffness of the first segment (S.sub.bs) in respect of the
second segment (S.sub.bf) is defined by the equation: 4 1.5 S bs S
bf 20
4. The medical electrical lead of claim 1, wherein the ratio of the
bending stiffness of the first segment (S.sub.bs) in respect of the
second segment (S.sub.bf) is defined by the equation: 5 1.5 S bs S
bf 10
5. The medical electrical lead of claim 1, wherein the ratio of the
bending stiffness of the first segment (S.sub.bs) in respect of the
second segment (S.sub.bf) is defined by the equation: 6 2 S bs S bf
6
6. The medical electrical lead of claim 1, wherein the bending
stiffness of the first segment (S.sub.bs) is at least 1.5 times
that of the bending stiffness of the second segment (S.sub.bf).
7. The medical electrical lead of claim 1, wherein the bending
stiffness of the first segment (S.sub.bs) is at least 1.8 times
that of the bending stiffness of the second segment (S.sub.bf).
8. The medical electrical lead of claim 1, wherein the bending
stiffness of the first segment (S.sub.bs) is at least about 2 times
that of the bending stiffness of the second segment (S.sub.bf).
9. The medical electrical lead of claim 1, wherein the bending
stiffness of the first segment (S.sub.bs) is at least about 4 times
that of the bending stiffness of the second segment (S.sub.bf).
10. The medical electrical lead of claim 1, wherein the bending
stiffness of the first segment (S.sub.bs) is at least about 6 times
that of the bending stiffness of the second segment (S.sub.bf).
11. The medical electrical lead of claim 1, wherein the ratio of
the bending stiffness of the first segment (S.sub.bs) in respect of
the second segment (S.sub.bf) is selected from the group consisting
of at least about 2.2, at least about 2.4, at least about 2.6, at
least about 2.8, at least about 3.0, at least about 4, at least
about 5, at least about 6, at least about 7, at least about 8, at
least about 9, at least about 10, at least about 20, at least about
30, at least about 40, at least about 50, and at least about
100.
12. The medical electrical lead of claim 1, wherein the distal
section of the lead body comprises a plurality of alternating
series of substantially adjoining first and second segments.
13. The medical electrical lead of claim 1, wherein the distal
section of the lead body comprises a third segment having a bending
stiffness which exceeds the bending stiffness of the second
segment, the second segment being disposed between the first and
third segments.
14. The medical electrical lead of claim 1, wherein the distal
section of the lead body comprises a third segment having a bending
stiffness which is less than the bending stiffness of the first
segment, the first segment being disposed between the second and
third segments.
15. The medical electrical lead of claim 1, wherein the bending
stiffness of the distal section of the lead body increases distally
in one of step-wise, monotonic, exponential or logarithmic
fashion.
16. The medical electrical lead of claim 1, wherein the bending
stiffness of the distal section of the lead body decreases distally
in one of step-wise, monotonic, exponential or logarithmic
fashion.
17. The medical electrical lead of claim 1, wherein the lengths of
the first and second segments are selected according to a
particular venous anatomy in which the lead is to be implanted.
18. The medical electrical lead of claim 1, wherein the lead
assumes a substantially straight shape prior to implantation.
19. The medical electrical lead of claim 1, wherein the lead body
has at least one pre-formed curve disposed therein.
20. The medical electrical lead of claim 1, wherein the distal
section of the lead body is formed into a curved configuration.
21. The medical electrical lead of claim 1, wherein the distal
section of the lead body and the first and second sections thereof
are dimensioned and configured for use in a coronary sinus or
cardiac vein of the heart.
22. The medical electrical lead of claim 1, wherein a fixation
device is attached to the lead body.
23. The medical electrical lead of claim 22, wherein the fixation
device is selected from the group consisting of a helical screw, a
barb, a hook, at least one tine, and at least one arm.
24. The medical electrical lead of claim 22, wherein the fixation
device is disposed near the distal end.
25. The medical electrical lead of claim 1, wherein the at least
one electrode is located along the distal section of the lead body
at a location appropriate to locate the electrode adjacent the left
atrium or left ventricle of the heart.
26. The medical electrical lead of claim 1, wherein the lead, the
at least one electrode, and the first and second segments are
configured and dimensioned to form a single pass lead for dual
chamber pacing of a left atrium and a left ventricle via
implantation within a coronary sinus and a great cardiac vein of
the heart.
27. The medical electrical lead of claim 1, wherein the lead body
is configured to permit preferential bending thereof along at least
one pre-determined bending plane.
28. The medical electrical lead of claim 1, wherein the lead body
is configured to permit three dimensional bending thereof along at
least two pre-deteremined bending planes.
29. The medical electrical lead of claim 1, wherein the bending
stiffness of at least one of the first segment and the second
segment is rotationally symmetric.
30. The medical electrical lead of claim 1, wherein the bending
stiffness of at least one of the first segment and the second
segment is rotationally asymmetric.
31. The medical electrical lead of claim 30, wherein the at least
one electrode and the lead body are dimensioned and configured such
that when the lead is appropriately implanted within a venous
portion of the heart the rotationally asymmetric segment may be
employed by a physician to orient placement of the at least one
electrode such that the electrode is pressed against or directed
towards a selected portion of the heart.
32. The medical electrical lead of claim 1, wherein the lead has a
unipolar electrode configuration.
33. The medical electrical lead of claim 1, wherein the lead has a
multi-polar electrode configuration.
34. The medical electrical lead of claim 1, wherein the lead
further comprises at least one defibrillation electrode.
35. The medical electrical lead of claim 34, wherein the at least
one defibrillation electrode is one of a coil electrode and a ring
electrode.
36. The medical electrical lead of claim 1, wherein the lead
comprises pacing and defibrillation electrodes.
37. The medical electrical lead of claim 1, wherein the lead body
is configured and dimensioned such that when the lead is implanted
within a venous portion of the human heart the second segment is
located in portions of the venous portion which exhibit the
greatest curvature.
38. The medical electrical lead of claim 37, wherein the bending
stiffness of the lead body increases both proximally and distally
in respect of the second segment.
39. The medical electrical lead of claim 1, wherein the second
segment is disposed proximally from the first segment, the first
and second segments are contiguous with one another along a
junction, and the junction is located along the lead body at an
axial position such that when the lead is implanted within a venous
anatomy of the human heart the junction is located near an end of a
curve in the venous anatomy.
40. The medical electrical lead of claim 1, wherein the lead body
comprises a first asymmetric cross-section configured for
implantation in a first preferred orientation in pre-determined
distal-most portions of the heart's venous anatomy where bending
radii are small, a second asymmetric cross-section configured for
implantation in a second preferred orientation different from the
first orientation in pre-determined portions of the heart's venous
anatomy located proximal from the distal-most portions thereof.
41. The medical electrical lead of claim 1, wherein the bending
stiffness of a proximal portion of the distal section of the lead
body increases distally and wherein the proximal portion of the
distal section of the lead body is configured and dimensioned such
that the proximal portion of the distal section of the lead body is
located in a right atrium and a coronary sinus of the heart upon
implantation.
42. The medical electrical lead of claim 41, wherein a length of
the proximal portion of the distal section of the lead body is
selected from the group consisting of between about 5 cm and about
15 cm, about 10 cm, between about 2 cm and about 17 cm, between
about 7 cm and about 13 cm, and between about 9 cm and about 11
cm.
43. The medical electrical lead of claim 1, wherein the lead body
comprises a material selected from the group consisting of silicone
rubber, polyurethane, PEBAX, PTFE, and ETFE.
44. The medical electrical lead of claim 1, wherein the first and
second segments comprise means for changing the bending stiffness
of the lead body as a function of axial distance selected from the
group consisting of coils having variable pitch as a function of
axial distance, coils having variable winding as a function of
axial distance, coils having variable diameter as a function of
axial distance, coils having variable pitch as a function of axial
distance, the lead body having variable diameter as a function of
axial distance, progressively adding more material to the lead body
as a function of axial distance, adding more coils to the lead body
as a function of axial distance, varying lead body insulation
thickness as a function of axial distancie, varying lead body
insulation type as a function of axial distance, progressively
incorporating more ring-shaped members into the lead body as a
function of axial distance, varying electrode structure as a
function of axial distance, varying electrode positioning as a
function of axial distance, including members having changing
bending stiffness along an outside portion of the lead body,
disposing a member internally in the lead body having variable
thickness as a function of axial distance, flattening portions of
the lead body, and incorporating depressions into the lead
body.
45. The medical electrical lead of claim 1, wherein the first and
second segments comprise means for changing the bending stiffness
of the lead body as a function of axial distance x selected from
the group consisting of varying the bending modulus as a function
of axial distance x of the material from which the lead body is
formed, varying the density as a function of axial distance x of
the material from which the lead body is formed, varying the
composition as a function of axial distance x of a polymer from
which the lead body is formed, varying the amount of cross-linking
as a function of axial distance x in a polymer from which the lead
body is formed, varying the flexule moduli as a function of axial
distance x of the material from which the lead body is formed,
varying the amount of a first polymer included, blended or mixed in
a second polymer as a function of axial distance x, a shape-memory
alloy member capable of having its bending stiffness be varied
through selective activation of pre-determined portions thereof as
a function of axial distance x, varying the composition of polymers
included in the lead body as a function of axial distance x.
46. The medical electrical lead of claim 1, wherein the lead body
is configured and dimensioned such that when the lead is implanted
within the heart the first segment is disposed in a distal portion
of one of a great cardiac vein, a middle cardiac vein, a coronary
sinus, a small cardiac vein, a posterior cardiac vein, an oblique
left atrial vein, and an anterior cardiac vein.
47. The medical electrical lead of claim 1, wherein the lead body
is configured and dimensioned such that when the lead is implanted
within the heart the second segment is disposed in a distal portion
of one of a great cardiac vein, a middle cardiac vein, a coronary
sinus, a small cardiac vein, a posterior cardiac vein, an oblique
left atrial vein, and an anterior cardiac vein.
48. The medical electrical lead of claim 1, wherein the lead body
and the at least one electrode are configured and dimensioned such
that when the lead is appropriately implanted within a great
cardiac vein or a posterior cardiac vein of the heart a left
ventricle of the heart may be electrically stimulated.
49. The medical electrical lead of claim 1, wherein the lead body
and the at least one electrode are configured and dimensioned such
that when the lead is appropriately implanted within an oblique
left atrail vein of the heart a left atrium of the heart may be
electrically stimulated.
50. The medical electrical lead of claim 1, wherein the lead body
and the at least one electrode are configured and dimensioned such
that when the lead is appropriately implanted within a middle
portion of a great cardiac vein a right ventricle of the heart may
be electrically stimulated.
51. The medical electrical lead of claim 1, wherein the lead body
and the at least one electrode are configured and dimensioned such
that when the lead is appropriately implanted within an anterior
cardiac vein a left atrium of the heart may be electrically
stimulated.
52. The medical electrical lead of claim 1, wherein the lead body
and the at least one electrode are configured and dimensioned such
that when the lead is appropriately implanted within an anterior
cardiac vein a left ventricle of the heart may be electrically
stimulated.
53. The medical electrical lead of claim 1, wherein the at least
one electrode further comprises an anode and a cathode, and wherein
the lead body and the anode and the cathode are configured and
dimensioned such that when the lead is appropriately implanted
within a middle cardiac vein electrical stimulation of apical
portions of the heart may be effected.
54. The medical electrical lead of claim 1, wherein the at least
one electrode further comprises an anode and a cathode, and wherein
the lead body and the anode and the cathode are configured and
dimensioned such that when the lead is appropriately implanted
within a posterior cardiac vein electrical stimulation of basal
portions of the heart may be effected.
55. The medical electrical lead of claim 1, wherein the at least
one electrode further comprises an anode and a cathode, and wherein
the lead body and the anode and the cathode are configured and
dimensioned such that when the lead is appropriately implanted
within a great cardiac vein electrical stimulation of basal
portions of the heart may be effected.
56. The medical electrical lead of claim 1, wherein the distal
section of the lead body comprises a plurality of alternating first
segments and second segments.
57. The medical electrical lead of claim 1, wherein at least one of
the first segment and the second segment has a length selected from
the group consisting of about 8 mm, between about 5 mm and about 10
mm, between about 5 mm and about 12 mm, and between about 5 mm and
about 50 mm.
58. The medical electrical lead of claim 1, wherein the distal end
is tapered.
59. The medical electrical lead of claim 1, wherein at least a
portion of the lead body has an outer diameter selected from the
group consisting of between about 1 mm and about 2 mm, about 0.5
mm, about 3 mm, and exceeding 3 mm.
60. The medical electrical lead of claim 1, wherein the at least
one electrode is disposed in the first segment.
61. The medical electrical lead of claim 1, wherein the distal
section of the lead body comprises a plurality of alternating first
segments and second segments and the at least one electrode further
comprises a cathode and an anode, the anode and the cathode being
disposed on different first segments.
62. The medical electrical lead of claim 1, wherein the at least
one electrode further comprises a cathode and an anode, the anode
and the cathode being disposed on the first segment.
63. The medical electrical lead of claim 1, wherein the at least
one electrode further comprises a cathode and an anode, the anode
and the cathode being separated from one another along the lead
body by a distance selected from the group consisting of between
about 4 mm and about 12 mm, between about 5 mm and about 10 mm,
between about 5 mm and about 7 mm, and about 5 mm, between about 20
mm and about 50 mm, about 60 mm, and about 15 mm.
64. The medical electrode of claim 1, wherein the lead body further
comprises a lumen formed therein for accepting a stylet.
65. The medical electrical lead of claim 1, wherein the distal
section of the lead body comprises a plurality of first and second
segments, the first and second segments being configured and
dimensioned such that the lead body exhibits a number of different
minimum mechanical energy storage positions the lead body may
assume within a venous anatomy of a patient.
66. The medical electrical lead of claim 65, wherein the first and
second segments have first and second lengths, and wherein the
first and second lengths are selected according to the radii of
different venous curves which are anticipated to be encountered
when the lead is implanted within the heart.
67. The medical electrical lead of claim 1, wherein the distal
section of the lead body comprises a plurality of first and second
segments having first and second lengths, respectively, and wherein
the second segments are configured and dimensioned to be located in
or along at least a first curve having a first radius of curvature
in a venous anatomy of the heart, and wherein the first segments
are configured and dimensioned to be located in or along a second
curve having a second radius of curvature, the first radius being
smaller than the second radius.
68. An elongated implantable medical electrical lead for
electrically stimulating a human heart or sensing electrical
signals originating therefrom, comprising: (a) an elongated lead
body comprising proximal and distal sections, the elongated lead
body defining axial distances which increase distally; (b) at least
one electrode for sensing or electrically stimulating the heart;
(c) a proximal end comprising an electrical connector, the
connector being contiguous with the proximal section of the lead
body; (d) a distal end portion contiguous with the distal section
of the lead body, the distal end portion extending distally from
the distal section of the lead body; (e) at least one electrical
conductor having proximal and distal ends, the distal end of the
conductor being operatively connected to the at least one
electrode, the proximal end of the conductor being operatively
connected to the electrical connector; wherein the distal section
of the lead body further comprises a variable bending stiffness
portion having bending stiffnesses which increase in respect of
axial distance.
69. The medical electrical lead of claim 68, wherein the ratio of
the bending stiffness of a distal-most portion of the distal
section (S.sub.bs) in respect of the bending stiffness of a
proximal-most portion of the distal section (S.sub.bf) is defined
by the equation: 7 1.5 S bs S bf 100
70. The medical electrical lead of claim 68, wherein the ratio of
the bending stiffness of a distal-most portion of the distal
section (S.sub.bs) in respect of the bending stiffness of a
proximal-most portion of the distal section (S.sub.bf) is defined
by the equation: 8 1.5 S bs S bf 10
71. The medical electrical lead of claim 65, wherein the bending
stiffness of a distal-most portion of the distal section (S.sub.bs)
is greater than the bending stiffness of a proximal-most portion of
the distal section (S.sub.bf) by a factor of at least about 2.
72. The medical electrical lead of claim 65, wherein the bending
stiffness of the distal section of the lead body increases distally
in one of step-wise, monotonic, exponential or logarithmic
fashion.
73. The medical electrical lead of claim 65, wherein the lead
assumes a substantially straight shape prior to implantation.
74. The medical electrical lead of claim 65, wherein the distal
section of the lead body is formed into a curved configuration.
75. The medical electrical lead of claim 65, wherein the distal
section of the lead body is dimensioned and configured for
implantation within a coronary sinus or cardiac vein of the
heart.
76. The medical electrical lead of claim 65, wherein a fixation
device is attached to the lead body.
77. The medical electrical lead of claim 76, wherein the fixation
device is selected from the group consisting of a helical screw, a
barb, a hook, at least one tine, and at least one arm.
78. The medical electrical lead of claim 65, wherein the at least
one electrode is located along the distal section of the lead body
at a location appropriate to locate the electrode adjacent the left
atrium or left ventricle of the heart.
79. The medical electrical lead of claim 65, wherein the lead, the
at least one electrode, and distal section of the lead body are
configured and dimensioned to form a single pass lead for dual
chamber pacing of a left atrium and a left ventricle via
implantation within a coronary sinus and a great cardiac vein of
the heart.
80. The medical electrical lead of claim 65, wherein the lead body
is configured to permit preferential bending thereof along at least
one pre-determined bending plane.
81. The medical electrical lead of claim 65, wherein the bending
stiffness of the distal section of the lead body is rotationally
symmetric.
82. The medical electrical lead of claim 65 wherein the bending
stiffness of the distal section of the lead body is rotationally
asymmetric.
83. The medical electrical lead of claim 82, wherein the at least
one electrode and the lead body are dimensioned and configured such
that when the lead is appropriately implanted within a venous
portion of the heart the rotationally asymmetric segment may be
employed by a physician to orient placement of the at least one
electrode such that the electrode is pressed against or directed
towards a selected portion of the heart.
84. The medical electrical lead of claim 65, wherein the lead has a
unipolar electrode configuration.
85. The medical electrical lead of claim 65, wherein the lead has a
multi-polar electrode configuration.
86. The medical electrical lead of claim 65, wherein the lead
further comprises at least one defibrillation electrode.
87. The medical electrical lead of claim 65, wherein the lead body
further comprises a first asymmetric cross-section configured for
implantation in a first preferred orientation in pre-determined
distalmost portions of the heart's venous anatomy where bending
radii are small, and a second asymmetric cross-section configured
for implantation in a second preferred orientation different from
the first orientation in pre-determined portions of the heart's
venous anatomy located proximal from the distalmost portions
thereof.
88. The medical electrical lead of claim 65, wherein the distal
section of the lead body comprises means for changing the bending
stiffness of the lead body as a function of axial distance selected
from the group consisting of coils having variable pitch as a
function of axial distance, coils having variable winding as a
function of axial distance, coils having variable diameter as a
function of axial distance, coils having variable pitch as a
function of axial distance, the lead body having variable diameter
as a function of axial distance, progressively adding more material
to the lead body as a function of axial distance, adding more coils
to the lead body as a function of axial distance, varying lead body
insulation thickness as a function of axial distance, varying lead
body insulation type as a function of axial distance, progressively
incorporating more ring-shaped members into the lead body as a
function of axial distance, varying electrode structure as a
function of axial distance, varying electrode positioning as a
function of axial distance, including members having changing
bending stiffness along an outside portion of the lead body,
disposing a member internally in the lead body having variable
thickness as a function of axial distance, flattening portions of
the lead body, and incorporating depressions into the lead
body.
89. The medical electrical lead of claim 65, wherein the distal
section of the lead body comprises means for changing the bending
stiffness of the lead body as a function of axial distance x
selected from the group consisting of varying the bending modulus
as a function of axial distance x of the material from which the
lead body is formed, varying the density as a function of axial
distance x of the material from which the lead body is formed,
varying the composition as a function of axial distance x of a
polymer from which the lead body is formed, varying the amount of
cross-linking as a function of axial distance x in a polymer from
which the lead body is formed, varying the flexule moduli as a
function of axial distance x of the material from which the lead
body is formed, varying the amount of a first polymer included,
blended or mixed in a second polymer as a function of axial
distance x, a shape-memory alloy member capable of having its
bending stiffness be varied through selective activation of
pre-determined portions thereof as a function of axial distance x,
varying the composition of polymers included in the lead body as a
function of axial distance x.
90. The medical electrical lead of claim 65, wherein the distal
section of the lead body has a length selected from the group
consisting of about 8 mm, between about 5 mm and about 10 mm,
between about 5 mm and about 12 mm, and between about 5 mm and
about 50 mm.
91. The medical electrical lead of claim 65, wherein the distal end
portion is tapered.
92. The medical electrical lead of claim 65, wherein at least a
portion of the lead body has an outer diameter selected from the
group consisting of between about 1 mm and about 2 mm, about 0.5
mm, about 3 mm, and exceeding 3 mm.
93. The medical electrical lead of claim 65, wherein the at least
one electrode further comprises a cathode and an anode.
94. The medical electrical lead of claim 65, wherein the at least
one electrode further comprises a cathode and an anode, the anode
and the cathode being separated from one another along the lead
body by a distance selected from the group consisting of between
about 4 mm and about 12 mm, between about 5 mm and about 10 mm,
between about 5 mm and about 7 mm, and about 5 mm, between about 20
mm and about 50 mm, about 60 mm, and about 15 mm.
95. The medical electrode of claim 65, wherein the lead body
further comprises a lumen formed therein for accepting a
stylet.
96. A system for electrically stimulating, or sensing electrical
signals originating from, a human heart, the system comprising: (a)
an implantable cardiac stimulator, and (b) an elongated implantable
medical electrical lead for electrically stimulating the heart or
sensing electrical signals originating therefrom, comprising: (i) a
lead body having proximal and distal sections; (ii) at least one
electrode for sensing or electrically stimulating the heart; (iii)
a proximal end comprising an electrical connector, the electrical
connector being contiguous with the proximal section of the lead
body, the electrical connector being configured for operative
attachment to the cardiac stimulator; (iv) a distal end contiguous
with the distal section of the lead body; (v) at least one
electrical conductor having proximal and distal ends, the distal
end of the conductor being operatively connected to the at least
one electrode, the proximal end of the conductor being operatively
connected to the electrical connector; wherein the distal section
of the lead body comprises at least first and second segments, the
first segment having a bending stiffness S.sub.bs which exceeds the
bending stiffness S.sub.bf of the second segment, the first and
second segments being configured and dimensioned to impart a
distally directed force to the distal end of the lead when the
first and second segments are subjected to a bending moment
resulting in a sufficient curvature of the distal section of the
lead body.
97. The system of claim 96, wherein the cardiac stimulator is
selected from the group consisting of a pacemaker, an implantable
pulse generator (IPG), an implantable cardioverter-defibrillator
(ICD), a pacer-cardioverter-defibrillator (PCD), and an implantable
defibrillator.
98. A system for electrically stimulating, or sensing electrical
signals originating from, a human heart, the system comprising: (a)
an implantable cardiac stimulator, and (b) an elongated implantable
medical electrical lead for electrically stimulating the heart or
sensing electrical signals originating therefrom, comprising: (i)
an elongated lead body comprising proximal and distal sections,
thee elongated lead body defining axial distances which increase
distally; (ii) at least one electrode for sensing or electrically
stimulating the heart; (iii) a proximal end comprising an
electrical connector, the connector being contiguous with the
proximal section of the lead body; (iv) a distal end portion
contiguous with the distal section of the lead body, the distal end
portion extending distally from the distal section of the lead
body; (v) at least one electrical conductor having proximal and
distal ends, the distal end of the conductor being operatively
connected to the at least one electrode, the proximal end of the
conductor being operatively connected to the electrical connector;
wherein the distal section of the lead body further comprises a
variable bending stiffness portion having bending stiffnesses which
increase in respect of axial distance.
99. The system of claim 98, wherein the cardiac stimulator is
selected from the group consisting of a pacemaker, an implantable
pulse generator (IPG), an implantable cardioverterdefibrillator
(ICD), a pacer-cardioverter-defibrillator (PCD), and an implantable
defibrillator.
100. A method of electrically stimulating a patient's heart with an
implantable cardiac stimulator and an elongated implantable medical
electrical lead, the lead comprising a lead body having proximal
and distal sections, at least one electrode for sensing or
electrically stimulating the heart, a proximal end comprising an
electrical connector, the electrical connector being contiguous
with the proximal section of the lead body, the electrical
connector being configured for operative attachment to the cardiac
stimulator, a distal end contiguous with the distal section of the
lead body, at least one electrical conductor having proximal and
distal ends, the distal end of the conductor being operatively
connected to the at least one electrode, the proximal end of the
conductor being operatively connected to the electrical connector,
the distal section of the lead body comprising at least first and
second segments, the first segment having a bending stiffness
S.sub.bs which exceeds the bending stiffness S.sub.bf of the second
segment, the first and second segments being configured and
dimensioned to impart a distally directed force to the distal end
of the lead when the first and second segments are subjected to a
bending moment resulting in a sufficient curvature of the distal
section of the lead body, the method comprising: (a) providing the
cardiac stimulator; (b) providing the medical electrical lead; (c)
transvenously inserting and positioning the lead through a coronary
sinus and into a coronary vein in the heart, (d) operatively
connecting the connector of the lead to the cardiac stimulator; and
(e) delivering at least one electrical pulse originating in the
cardiac stimulator through the lead and the at least one electrode
to the heart.
101. The method of claim 100, wherein the at least one electrical
pulse is a pacing pulse, the method further comprising delivering a
pacing pulse to the heart.
102. The method of claim 100, wherein the at least one electrical
pulse is a defibrillation pulse, the method further comprising
delivering a pacing pulse to the heart.
103. The method of claim 100, the method further comprising
employing a stylet when inserting and positioning the lead in the
heart.
104. The method of claim 100, the method further comprising
employing a guide catheter when introducing the lead into the
coronary sinus.
105. The method of claim 100, the method further comprising
removing the guide catheter after the lead has been inserted
through the coronary sinus.
106. A method of electrically stimulating a patient's heart with an
implantable cardiac stimulator and an elongated implantable medical
electrical lead, the lead comprising an elongated lead body
comprising proximal and distal sections, the elongated lead body
defining axial distances which increase distally, at least one
electrode for sensing or electrically stimulating the heart, a
proximal end comprising an electrical connector, the connector
being contiguous with the proximal section of the lead body, a
distal end portion contiguous with the distal section of the lead
body, the distal end portion extending distally from the distal
section of the lead body, at least one electrical conductor having
proximal and distal ends, the distal end of the conductor being
operatively connected to the at least one electrode, the proximal
end of the conductor being operatively connected to the electrical
connector, the distal section of the lead body further comprising a
variable bending stiffness portion having bending stiffnesses which
increase in respect of axial distance, the method comprising: (a)
providing the cardiac stimulator; (b) providing the medical
electrical lead; (C) transvenously inserting and positioning the
lead through a coronary sinus and into a coronary vein in the
heart, (d) operatively connecting the connector of the lead to the
cardiac stimulator; and (e) delivering at least one electrical
pulse originating in the cardiac stimulator through the lead and
the at least one electrode to the heart.
107. The method of claim 106, wherein the at least one electrical
pulse is a pacing pulse, the method further comprising delivering a
pacing pulse to the heart.
108. The method of claim 106, wherein the at least one electrical
pulse is a defibrillation pulse, the method further comprising
delivering a pacing pulse to the heart.
109. The method of claim 106, the method further comprising
employing a stylet when inserting and positioning the lead in the
heart.
110. The method of claim 106, the method further comprising
employing a guide catheter when introducing the lead into the
coronary sinus.
111. The method of claim 110, the method further comprising
removing the guide catheter after the lead has been inserted
through the coronary sinus.
112. A method of electrically stimulating a patient's heart with an
implantable cardiac stimulator and an elongated implantable medical
electrical lead, the lead comprising a lead body having proximal
and distal sections, at least one electrode for sensing or
electrically stimulating the heart, a proximal end comprising an
electrical connector, the connector being contiguous with the
proximal section of the lead body, a distal end connected to the
distal section of the lead body, at least one electrical conductor
having proximal and distal ends, the distal end of the conductor
being operatively connected to the at least one electrode, the
proximal end of the conductor being operatively connected to the
electrical connector, the distal section of the lead body
comprising at least first and second segments, the first segment
having a bending stiffness S.sub.b1, the second segment having a
bending stiffness S.sub.b2, S.sub.b1 not equalling S.sub.b2, the
first segment, and the second segment being configured and
characterized such that a distally directed force is imparted to
the distal end of the lead when the first and second segments are
subjected to a bending moment resulting in a sufficient curvature
of the distal section of the lead body, the bending moment being
provided by an external force applied to the lead, the method
comprising: (a) providing the cardiac stimulator; (b) providing the
medical electrical lead; (c) transvenously inserting and
positioning the lead through a coronary sinus and into a coronary
vein in the heart, (d) operatively connecting the connector of the
lead to the cardiac stimulator; and (e) delivering at least one
electrical pulse originating in the cardiac stimulator through the
lead and the at least one electrode to the heart.
113. The method of claim 112, wherein the at least one electrical
pulse is a pacing pulse, the method further comprising delivering a
pacing pulse to the heart.
114. The method of claim 112, wherein the at least one electrical
pulse is a defibrillation pulse, the method further comprising
delivering a pacing pulse to the heart.
115. The method of claim 112, the method further comprising
employing a stylet when inserting and positioning the lead in the
heart.
116. The method of claim 112, the method further comprising
employing a guide catheter when introducing the lead into the
coronary sinus.
117. The method of claim 116, the method further comprising
removing the guide catheter after the lead has been inserted
through the coronary sinus.
118. A method of making an elongated implantable medical electrical
lead, the lead comprising a lead body having proximal and distal
sections, at least one electrode for sensing or electrically
stimulating the heart, a proximal end comprising an electrical
connector, the electrical connector being contiguous with the
proximal section of the lead body, the electrical connector being
configured for operative attachment to the cardiac stimulator, a
distal end contiguous with the distal section of the lead body, at
least one electrical conductor having proximal and distal ends, the
distal end of the conductor being operatively connected to the at
least one electrode, the proximal end of the conductor being
operatively connected to the electrical connector, the distal
section of the lead body comprising at least first and second
segments, the first segment having a bending stiffness S.sub.bs
which exceeds the bending stiffness S.sub.bf of the second segment,
the first and second segments being configured and dimensioned to
impart a distally directed force to the distal end of the lead when
the first and second segments are subjected to a bending moment
resulting in a sufficient curvature of the distal section of the
lead body, the method comprising: (a) providing the at least one
electrode; (b) providing the at least one electrical conductor; (c)
providing the electrical connector; (d) operatively connecting the
electrical connector to the proximal end of the electrical
conductor; (e) operatively connecting the distal end of the
electrical conductor to the at least one electrode; (f) providing
the lead body; and (g) incorporating the at least one electrical
conductor, the at least one electrode, the electrical connector and
the lead body into the lead.
119. A method of making an elongated implantable medical electrical
lead, the lead comprising an elongated lead body comprising
proximal and distal sections, the elongated lead body defining
axial distances which increase distally, at least one electrode for
sensing or electrically stimulating the heart, a proximal end
comprising an electrical connector, the connector being contiguous
with the proximal section of the lead body, a distal end portion
contiguous with the distal section of the lead body, the distal end
portion extending distally from the distal section of the lead
body, at least one electrical conductor having proximal and distal
ends, the distal end of the conductor being operatively connected
to the at least one electrode, the proximal end of the conductor
being operatively connected to the electrical connector, the distal
section of the lead body further comprising a variable bending
stiffness portion having bending stiffnesses which increase in
respect of axial distance, the method comprising: (a) providing the
at least one electrode; (b) providing the at least one electrical
conductor; (c) providing the electrical connector; (d) operatively
connecting the electrical connector to the proximal end of the
electrical conductor; (e) operatively connecting the distal end of
the electrical conductor to the at least one electrode; (f)
providing the lead body; and (g) incorporating the at least one
electrical conductor, the at least one electrode, the electrical
connector and the lead body into the lead.
120. A method of making an elongated implantable medical electrical
lead, the lead comprising a lead body having proximal and distal
sections, at least one electrode for sensing or electrically
stimulating the heart, a proximal end comprising an electrical
connector, the connector being contiguous with the proximal section
of the lead body, a distal end connected to the distal section of
the lead body, at least one electrical conductor having proximal
and distal ends, the distal end of the conductor being operatively
connected to the at least one electrode, the proximal end of the
conductor being operatively connected to the electrical connector,
wherein the distal section of the lead body comprises at least
first and second adjoining segments, the first segment being
relatively stiff, the second segment being relatively flexible, the
first and second segments being configured to impart a distally
directed force to the distal end of the lead when the segments are
subjected to a bending moment resulting in a sufficient curvature
of the distal section of the lead body, the method comprising: (a)
providing the at least one electrode; (b) providing the at least
one electrical conductor; (c) providing the electrical connector;
(d) operatively connecting the electrical connector to the proximal
end of the electrical conductor; (e) operatively connecting the
distal end of the electrical conductor to the at least one
electrode; (f) providing the lead body; and (g) incorporating the
at least one electrical conductor, the at least one electrode, the
electrical connector and the lead body into the lead.
121. A method of making an elongated implantable medical electrical
lead, the lead comprising a lead body having proximal and distal
sections, at least one electrode for sensing or electrically
stimulating the heart, a proximal end comprising an electrical
connector, the connector being contiguous with the proximal section
of the lead body, a distal end connected to the distal section of
the lead body, at least one electrical conductor having proximal
and distal ends, the distal end of the conductor being operatively
connected to the at least one electrode, the proximal end of the
conductor being operatively connected to the electrical connector,
the distal section of the lead body comprising at least first and
second segments, the first segment having a bending stiffness
S.sub.b1 the second segment having a bending stiffness S.sub.b2,
S.sub.b1 not equalling S.sub.b2, the first segment and the second
segment being configured and characterized such that a distally
directed force is imparted to the distal end of the lead when the
first and second segments are subjected to a bending moment
resulting in a sufficient curvature of the lead body, the bending
moment being provided by an external force applied to the lead, the
method comprising: (a) providing the at least one electrode; (b)
providing the at least one electrical conductor; (c) providing the
electrical connector; (d) operatively connecting the electrical
connector to the proximal end of the electrical conductor; (e)
operatively connecting the distal end of the electrical conductor
to the at least one electrode; (f) providing the lead body; and (g)
incorporating the at least one electrical conductor, the at least
one electrode, the electrical connector and the lead body into the
lead.
Description
[0001] This patent application hereby incorporates by reference
herein, in its entirety, co-pending U.S. Patent Application Ser.
No.______ , filed Nov.______ , 1999 for "Medical Electrical Lead
Having Variable Bending Stiffness" to Smits having Attorney Docket
No. P-8975.
FIELD OF THE INVENTION
[0002] The present invention relates to pacing and defibrillation
medical electrical leads. The present invention also relates to
medical electrical leads adapted and configured for implantation
within the coronary sinus and coronary veins.
BACKGROUND OF THE INVENTION
[0003] Transvenously inserted leads for implantable cardiac
pacemakers have conventionally been positioned within the right
atrium or right ventricle of the patient's heart for pacing or
defibrillating the right atrium and/or right ventricle,
respectively. While it is relatively safe to insert a pacing or
defibrillation lead and its associated electrodes into the right
atrium or right ventricle, there is a reluctance to install a
similar lead in the left ventricle because of the possibility of
clot formation and resulting stroke.
[0004] When a lead is implanted within a patient's circulatory
system, there is always the possibility of a thrombus being
generated and released. If the lead is positioned in the right
atrium or right ventricle, a generated thrombus tends to migrate
through the pulmonary artery and is filtered by the patient's
lungs. A thrombus generated in the left atrium or left ventricle,
however, would pose a danger to the patient due to the possibility
of a resulting ischemic episode.
[0005] Thus, in those instances where left heart stimulation is
desired, it has been a common practice to use an intercostal
approach using a myocardial screw-in, positive-fixation lead. The
screw-in lead may, however, be traumatic for the patient. There are
additional instances when left ventricular pacing is desired, such
as during bi-ventricular pacing. In U.S. Pat. No. 4,928,688, Mower
describes an arrangement for achieving bi-ventricular pacing in
which electrical stimulating pulses are applied via electrodes
disposed on a single pacing lead to both the right and left
ventricular chambers so as to obtain a coordinated contraction and
pumping action of the heart. The '688 patent also discloses a split
pacing lead having first and second separate electrodes, wherein
the first electrode is preferably introduced through the superior
vena cava for pacing the right ventricle and the second electrode
is introduced through the coronary sinus for pacing the left
ventricle. Other electrode leads which are inserted into the
coronary sinus have been described. For example, in U.S. Pat. No.
5,014,696 to Mehra and U.S. Pat. No. 4,932,407 to Williams
endocardial defibrillation electrode systems are disclosed.
[0006] Still other leads and catheters have been proposed,
including those described in the patents listed in Table 1
below.
1TABLE 1 U.S. Pat. No. Title 5,951,597 Coronary sinus lead having
expandable matrix anchor 5,935,160 Left ventricular access lead for
heart failure pacing 5,931,864 Coronary venous lead having fixation
mechanism 5,931,819 Guidewire with a variable stiffness distal
portion 5,925,073 Intravenous cardiac lead with wave shaped
fixation segment 5,897,584 Torque transfer device for temporary
transvenous endocardial lead 5,871,531 Medical electrical lead
having tapered spiral fixation 5,855,560 Catheter tip assembly
5,833,604 Variable stiffness electrophysiology catheter 5,810,867
Dilation catheter with varied stiffness 5,803,928 Side access "over
the wire" pacing lead 5,755,766 Open-ended intravenous cardiac lead
5,755,765 Pacing lead having detachable positioning member
5,749,849 Variable stiffness balloon catheter 5,733,496 Electron
beam irradiation of catheters to enhance stiffness 5,639,276 Device
for use in right ventricular placement and method for using same
5,628,778 Single pass medical electrical lead 5,605,162 Method for
using a variable stiffness guidewire 5,531,685 Steerable variable
stiffness device 5,499,973 Variable stiffness balloon dilatation
catheters 5,437,632 Variable stiffness balloon catheter 5,423,772
Coronary sinus catheter 5,330,521 Low resistance implantable
electrical leads 5,308,342 Variable stiffness catheter 5,144,960
Transvenous defibrillator lead and method of use 5,111,811
Cardioversion and defibrillation lead system with electrode
extension into the Coronary sinus and great vein 4,930,521 Variable
stiffness esophageal catheter 4,215,703 Variable stiffness guide
wire 08/794,175 Single Pass Medical Electrical Lead 08/794,402
Single Pass Medical Electrical Lead with Cap Electrodes
[0007] As those skilled in the art will appreciate after having
reviewed the specification and drawings hereof, at least some of
the devices and methods discussed in the patents of Table 1 may be
modified advantageously in accordance with the present invention.
All patents listed in Table 1 herein above are hereby incorporated
by reference herein, each in its respective entirety.
[0008] Prior art coronary vein leads for heart failure applications
(i.e., pacing leads) or sudden death applications (i.e.,
defibrillation leads) generally must be wedged in a coronary vein
to obtain a stable mechanical position and to prevent dislodgment.
While such an arrangement is generally acceptable for
defibrillation leads (which usually must be implanted with the
distal tip thereof located near the apex of the heart), such is not
the case for heart failure or pacing leads, where more basal
stimulation of the heart is generally desired. Basal stimulation of
the heart via the coronary vein, however, presents certain
difficulties because vein diameters in the basal area of the heart
are large and generally do not permit the distal end or tip of a
pacing lead to be sufficiently well wedged therein.
[0009] Medical electrical leads suitable for implantation within
the right atrium and/or right the ventricle are known in the art.
Leads having J-shapes imparted to the distal ends thereof are
likewise known in the art. Such leads having J-shaped distal ends
typically exhibit substantial bending stiffness at the distal
thereof, and are most often configured for placement in the right
atrium. It is typical that during implantation of such a lead
having a J-shaped section at the distal end thereof that, once the
lead has been placed within the right atrium, the lead is retracted
slightly to impart a positive tip force to the distal end of the
lead. Relatively small displacements of the lead in such a manner
can result in large variations in the force exerted by the tip of
the lead upon the atrial wall. It is therefore not uncommon for the
force exerted by the tip to either be excessive or to even become
negative, in which event the distal end of the lead is suspended
from its own tines or other distally disposed positive fixation
device. This, in turn, leads to mechanical instability of the
positioning of the distal section of the lead within the right
atrium or the right ventricle.
[0010] Thus, there exists a need to provide a pacing or
defibrillation medical electrical lead which exhibits better
mechanical stability following implantation.
SUMMARY OF THE INVENTION
[0011] The present invention has certain objects. That is, the
present invention provides solutions to one or more problems
existing in the prior art. For example, various embodiments of the
present invention have one or more of the following objects: (a)
providing a medical electrical lead suitable for implantation in
the right atrium or right ventricle which is not mechanically
unstable once implanted therein; (b) providing a medical electrical
lead which exhibits enhanced removability following implantation
and fibrosis; (c) providing a medical electrical lead suitable for
implantation within the right atrium or right ventricle which
requires less time and effort to implant; (d) providing a medical
electrical lead which exhibits reduced overall stiffness at the
distal end thereof; (e) providing a medical electrical lead, the
implantation of which exhibits decreased dependency on the
longitudinal position of the lead body thereof in the veins leading
to the right atrium or right ventricle; (f) a medical electrical
lead wherein small dislodgments occurring near the entrance of the
lead in the vein near the anchoring sleeve do not lead to electrode
tip dislodgment; and (g) a medical electrical lead wherein the
width of the J-shape imparted thereto resulting from implantation
within the right atrium or right ventricle may vary according to
the distance between the electrode position and the location of the
superior vena cava.
[0012] Various embodiments of the present invention suitable for
implantation within the right atrium or right ventricle possess
certain advantages, including one or more of the following: (a)
exhibiting multiple lead mechanical stability points which exhibit
less dependence on positive fixation mechanisms for proper
positioning relative to prior art leads; (b) providing a lead whose
retention within the right atrium or right ventricle is less
dependent upon the particular shape or diameter of such heart
chambers and venous anatomy than prior art leads; (c) providing a
lead which permits improved pacing electrode positioning within the
right atrium or right ventricle; (d) providing a lead which permits
lower pacing thresholds and improved sensing of intra-cardiac
signals; (e) providing a lead which exhibits improved acute and
chronic pacing thresholds and sensing characteristics; (f)
providing a lead which has no or reduced positive fixation
mechanisms attached thereto; (g) providing a lead which may be
implanted with an introducer of reduced size; (h) providing a lead
which improves chronic lead removability thereof; (i) providing a
straight lead which is easier, more reproducible and less expensive
to manufacture; A) providing a lead which exerts a positive
electrode tip pressure or force upon the side wall of the right
atrium or right ventricle; (k) providing a lead wherein the tip
pressure exerted thereby is less dependent on the specific location
of the lead body with respect-to the venous anatomy leading into
the atrium; (I) providing a lead wherein the depth of the placement
of the lead tip into the right atrial appendix may be selectively
varied; and (m) providing a medical electrical lead having a
stiffness which varies as a function of axial distance adapted for
specific placement and stability within veins other than the
coronary sinus and great cardiac vein, wherein the lead exhibits
appropriate distal curvatures and bending stiffnesses required for
implantation within the hepatic vein, spinal column,
sub-cutaneously, or in other locations within the human body.
[0013] Various embodiments of the present invention exhibit one or
more of the following features: (a) a distal section of a pacing or
defibrillation lead having variable bending stiffness adapted and
configured to create a forward driving force of the lead when the
variable bending stiffness portion of the distal end of the lead is
subjected to a bending moment resulting in sufficient curvature;
(b) a pacing or defibrillation lead having in a distal portion
thereof a variable bending stiffness section in which the bending
stiffness increases with respect to axial distance; (c) a medical
electrical lead which owing to variations in bending stiffness
along its axial direction imparts a positive tip force or a forward
driving force to the lead, and where bending of the lead may
preferentially take place along different pre-determined bending
planes (e.g., three dimensional bending along multiple preferred
orientations); (d) a pacing or defibrillation lead wherein
variations in bending stiffness are rotationally symmetric; (e) a
pacing or defibrillation lead wherein bending stiffness is
rotationally asymmetric to permit orientation of one or more
electrodes, fixation means, or other lead features relative to the
bending plane of a bent or curved section; (f) a pacing or
defibrillation lead exhibiting variable stiffness over at least
distal portions thereof and which is further characterized in
having active or passive fixation features, or no such features,
being unipolar or multi-polar, being a pacing or sensing lead,
being a defibrillation lead, or having a combination of
pacing/sensing and defibrillation capabilities; (g) providing a
lead capable of implantation within the right atrium or the right
ventricle; (h) providing a lead which may be implanted within the
right atrium, right ventricle, the coronary sinus, any of the
various and/or one or more of the coronary veins; (i) providing a
medical electrical lead having enhanced positive tip pressure
exerted thereby to promote the transfer of drugs released from the
distal tip or a distal portion thereof into the cardiac wall; (J)
providing a medical electrical lead having a side arm extending
therefrom in a single pass multi-chamber lead, wherein the side arm
is employed to pace or defibrillate the right atrium, and wherein
the size of the heart within which the lead is implanted assumes
less importance is respect of prior art leads because the lead body
may assume a greater range of positions within the superior vena
cava; (k) in a single pass multi-chamber lead, a medical electrical
lead having a side arm extending therefrom for implantation within
the right atrium, which side arm may be more easily located along
distal portions of the lead body to facilitate orientation and
location of the ventricular electrode; and (I) a medical electrical
lead employed in conjunction with a pulled wire for imparting
curvature to the distal portion thereof to facilitate handling and
prevent the electrode from becoming dislodged during the
implantation procedure. Methods of making, using, and implanting a
lead of the present invention are also contemplated in the present
invention.
[0014] These and other objects, features and advantages of the
present invention will be readily apparent to those skilled in the
art from a review of the following detailed description of the
preferred embodiment in conjunction with the accompanying drawings
in which like numerals in the several views refer to corresponding
parts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1A and 1B illustrate two different embodiments of the
present invention implanted within a human heart;
[0016] FIG. 2A illustrates parameters employed in modeling one
embodiment of the present invention;
[0017] FIG. 2B shows results obtained using the modeling
assumptions of FIG. 2A;
[0018] FIG. 3A illustrates one embodiment of a distal section of a
lead body of the present invention and its corresponding bending
stiffness profile;
[0019] FIG. 3B illustrates a conventional lead implanted within a
right atrium;
[0020] FIG. 3C illustrates a lead of the present invention
implanted within a right atrium;
[0021] FIGS. 4A-4E illustrate various means of increasing the being
stiffness of the distal section of a lead body in the present
invention as a function of axial distance;
[0022] FIG. 5 shows a partial cross-sectional view of a heart
having one embodiment of a lead of the present invention disclosed
therein;
[0023] FIGS. 6A-6C illustrate various principles associated with
bending stiffness in respect of several embodiments of the present
invention;
[0024] FIGS. 7A-7C illustrate schematically several different
embodiments of leads of the present invention and their
corresponding bending stiffnesses and derivatives of stored
mechanical energy with respect to axial distance;
[0025] FIGS. 8A and 8B show two different embodiments of a lead
body of the present invention in cross-section;
[0026] FIGS. 9A and 9B illustrate combined cross-sectional and
perspective views of two different lead bodies of the present
invention;
[0027] FIG. 10 illustrates an enlarged cross-sectional view of one
embodiment of a lead of the present invention disposed within
portions of the venous anatomy;
[0028] FIG. 11 illustrates one embodiment of the present invention
adapted for implantation within various portions of the venous
anatomy;
[0029] FIG. 12 illustrates several methods of implanting a lead of
the present invention within a human heart and electrically
stimulating same.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] FIG. 1A shows human heart 1 with medical electrical lead 10
of the present invention implanted therein. Proximal end 20 of
medical electrical lead 10 is connected to implantable cardiac
stimulator 30 by means of connector or terminal 18. Cardiac
stimulator 30 may be a pacemaker, an implantable pulse generator
(IPG), an implantable cardiodefibrillator (ICD), a
pacer-cardioverter-defibrillator (PCD), or any other type of
similar cardiac stimulator well known in the art. Medical
electrical lead 10 comprises proximal portion 20, distal portion 22
and lead body 12. Tip 50 is disposed at the distalmost end of lead
10. Electrode 14 may be positioned near tip 50 or at any other
suitable location along lead body 12. Tip 50 may also have disposed
thereon or adjacent thereto tines 57 or any other positive fixation
means such as a helical screw, barb, hook or the like.
[0031] As shown in FIG. 1A, lead 10 of the present invention may be
implanted in right atrium 3, and preferably displays a J-shaped
curve at the distal end thereof upon implantation. Medical
electrical lead 10 comprises one or more electrodes 14 disposed
thereon for pacing, sensing and/or defibrillating heart 1.
[0032] Referring now to FIG. 1B, there is shown human heart 1 with
medical electrical lead 10 of the present invention implanted
within right ventricle 5. Distal portion 22 of medical electrical
lead 10 may similarly exhibit a J-shaped curvature similar to that
shown in FIG. 1A. In a preferred embodiment of the present
invention distal portion 22 of medical electrical lead 10 does not
have a pre-formed J-shaped curve formed therein, but rather prior
to implantation assumes a substantially straight configuration
which facilitates implantation thereof. In less preferred
embodiments of the present invention, however, distal portion 22 of
lead 10 may be pre-shaped as desired into, for example, a
J-shape.
[0033] It is a basic principle of the present invention that distal
portion 22 of lead body 12 exhibits increased bending stiffness
relative to sections of lead body 12 disposed proximally therefrom.
Such a bending stiffness profile as a function of axial distance x
has the surprising result of a distally directed force acting upon
lead 10 to thereby push lead 10 forwardly or distally, more about
which we say below.
[0034] Because the bending stiffness of lead 10 increases with
axial position x, the amount of energy stored along the curve
formed in distal section 22 depends on the position of distal
section 22 relative to the curve. When the distal section 22 is
moved forward along the curve, the bending stiffness and
corresponding stored energy of the portion of section 22 disposed
in the curve decreases. That is, a lead which prior to implantation
assumes a substantially straight shape and in which distal portion
22 exhibits variable bending stiffness, where the bending stiffness
increases in the distal direction upon implantation, exerts a
positive tip pressure or force on the walls of atrium 3 or
ventricle 5 when it is shaped into a curved J-shape in an attempt
to minimize the amount of stored mechanical potential energy. In
fact, when lead 10 exhibits a stiffness gradient of about 1
Nmm/radian in distal section 22, a tip force of about 0.1 N results
(assuming lead 10 has been bent through a 180.degree. curve over a
15 mm curve radius).
[0035] In the present invention, it is contemplated that bending
stiffness gradients of distal section 22 of lead 10 range between
about 0.05 and about 1.0 Nmm per radian, or between about 0.05 and
about 1.5 Nmm per radian, forces exerted by tip 50 of lead 10 of
the present invention may range between about 0.005 N and about 0.1
N. Other ranges of bending stiffness gradients and forces are also
contemplated in the present invention, such as stiffness gradients
ranging between about 0.1 to about 0.5 Nmm per radian, and forces
exerted by distal section 22 ranging between about 0.01 N and about
0.05 N. Other ranges of stiffness gradients and forces are likewise
contemplated in the present invention even though not explicitly
set forth herein.
[0036] Referring now to FIG. 2A, the feasibility of the present
invention was tested by means of a computer program. The physical
parameters employed in the program are shown in FIG. 2A. The
results provided by the program are shown in FIG. 2B.
[0037] The lead design parameters employed as inputs to the program
included the following: lead 10, rigidly clamped by the "fixed
world" 99 at its proximal end, comprised an originally straight
lead section 22 which was bent over about 180.degree.. Tip 50 was
assumed to form a section about 15 mm long, while reinforced or
relatively stiff section 2 had its length varied between about 10
mm and 40 mm. Reinforced section 2 corresponds to relatively stiff
section described here below in connection with various embodiments
of the present invention. Section 4 of lead body 12 shown in FIG.
2A corresponds to relatively flexible section 4 described below in
connection with various embodiments of the present invention. The
calculated tip force exerted on distal section 22 of lead 10 having
various different lengths of relatively stiff section 2 are shown
in FIG. 2B. The calculated tip forces shown in FIG. 2B proved the
feasibility of the basic concept of the present invention. A
positive force component F.sub.y of the total force F acting on tip
50 is representative for a stable position of tip 50. For a
reinforcement (2) of 40 mm length (E40), F.sub.y is positive for
vertical tip positions from Y=-10 mm till y =30 mm, corresponding
to a range of 40 mm.
[0038] Referring now to FIG. 3A, there is shown lead 10 of the
present invention having disposed immediately therebelow its
corresponding bending stiffness (S.sub.b) profile, where the
bending stiffness varies as a function of axial distance x. Lead 10
comprises distal portion 22, lead body 12, relatively flexible
section 4, relatively stiff section 2, tip 50 and tines 57. Other
positive fixation means such as a helical screw, barb, hook, and
the like may be disposed on or near tip 50, such as optional tip 50
illustrated to the right of tined tip 57 in FIG. 3A. The bending
stiffness profile of lead 10 is shown to increase over the length
of that portion of lead 10 which is to have a J-shaped curve upon
implantation within right atrium 3 (e.g., at least portions of
distal section 22). That is, when initially straight lead 10 is
implanted in human heart 1, lead 10 is bent into a J-shaped
configuration within right atrium 3 (or right ventricle 5).
[0039] Referring now to FIGS. 3B and 3C, there are shown two
different leads. FIG. 3B shows conventional lead 10 disposed in
right atrium 3 such that distal portion 22 is bent into a J-shape.
Superimposed upon the cross-section of lead 10 and heart 1 in FIG.
3B are corresponding force vectors acting upon distal portion 22 of
lead 10 in response to the axial forces exerted by lead 10 upon the
walls of atrium 3. Note that those force vectors are relatively
uniform respecting magnitude.
[0040] Contrariwise, the force vectors shown in FIG. 3C acting upon
lead 10 are not uniform, and increase in magnitude in the distal
direction of lead 10. This feature of the present invention results
in the distally directed forward pushing force (F.sub.push) shown
in FIG. 3C which is conteracted by the axial tip force F.sub.tip
and an axial force on lead body 12, to provide a static equilibrium
of forces and moments. As discussed hereinabove, that pushing force
is the direct result of the unique bending stiffness profile of
distal section 22 of lead body 12.
[0041] FIGS. 4A-4E illustrate various means of increasing the
bending stiffness of distal section 22 of lead body 10 as a
function of axial distance x. FIG. 4A shows coil 59 disposed within
lead body 12. The pitch of spring of coil 59 increases in the axial
direction x to thereby increase the bending stiffness as one moves
towards tip 50 along lead body 12.
[0042] FIG. 4B shows another embodiment of the present invention,
where the bending stiffness of lead body 12 increases in the distal
direction along axial direction x by means of increasing the
thickness of the outer covering or layer of lead body 12. Note that
an inwardly disposed layer or substrate could also exhibit
increasing thickness in the distal direction to achieve the same
result. Likewise, a material of uniform thickness but exhibiting
changes in its elastic modulii as a function of axial distance x
could also be employed to achieve the same result.
[0043] FIG. 4C shows another embodiment of the present invention,
where an increase in bending stiffness with increasing axial
distance x is achieved by increasing the diameter of lead body 12
in the distal direction.
[0044] FIG. 4D shows distal portion 22 of lead 10 having
successively more layers 61A, 61B and 62B, disposed over outer
portions thereof to impart an increase in bending stiffnessess as a
function of axial distance x.
[0045] FIG. 4E shows one embodiment of the present invention where
an increase in bending stiffness with axial distance x is achieved
by decreasing the diameter of a coil disposed therein as a function
of axial distance x.
[0046] It will now become apparent to those skilled in the art,
after having read the specification and reviewed the drawings
thereof, that many other means of achieving the results of the
present invention are possible, where the bending stiffness of lead
body 12 in distal section 22 increases in the distal direction.
[0047] It is contemplated in the present invention that means of
varying the bending stiffness of the distal section of a lead of
the present invention other than those described here and above
respective FIGS. 4A-4E fall within the scope of the present
invention. For example, the material from which lead body 12 is
formed may be varied compositionally or otherwise as a function of
axial distance x, to thereby effectuate changes in the bending
stiffness thereof. The degree to which a polymer forming lead body
12 is cross-linked may be varied as a function of axial distance x.
The density of the polymers or other materials employed to form
lead body 12 may be varied as a function of axial distance x. The
molecular weight of the polymers or other materials from which lead
body 12 is formed may be varied as a function of axial distance x.
A flexible tubular member containing a shape-memory tube may be
included in a lumen extending along a central axis of the lead
body, and a control system may then selectively heat portions of
the shape-memory tube to change the bending stiffness or shape
thereof. The foregoing and other methods of varying the bending
stiffness of the distal section of a lead body of the present
invention are contemplated in the present invention. See, for
example, U.S. Pat. No. 5,437,632 for "Variable stiffness balloon
catheter"; U.S. Pat. No. 5,499,973 for "Variable stiffness balloon
dilatation catheters"; U.S. Pat. No. 5,531,685 for "Steerable
variable stiffness device"; U.S. Pat. No. 5,639,276 for "Device for
use in right ventricular placement and method for using same"; U.S.
Pat. No. 5,833,604 for "Variable stiffness electrophysiology
catheter"; and U.S. Pat. No. 5,733,496 for "Electron beam
irradiation of catheters to enhance stiffness", the disclosures of
which are hereby incorporated by reference herein, each in its
respective entirety.
[0048] Referring now to FIG. 5, there is shown a cross-sectional
view of lead 10 disposed in, for example, posterior cardiac vein 17
of heart 1 via coronary sinus 13 and great cardiac vein 23. At
least portions of distal portion 22 of lead 10 are located in
posterior cardiac vein 17. FIG. 5 illustrates how lead 10 must be
routed through a series of winding tortuous pathways when implanted
in the cardiac veins. Such pathways not only make implantation and
placement of lead 10 in desired portions of heart 1 difficult, but
also have a tendency to cause prior art leads to be pushed out of
the cardiac vein in which they have been located by implantation,
further discussion concerning which follows below.
[0049] Continuing to refer to FIG. 5, there is shown medical
electrical lead 10 of the present invention, which prior to
implantation most preferably has a straight distal section 22 and
which is adapted for implantation within coronary sinus 13, great
cardiac vein 23, or within any other of the left ventricular
coronary veins or left atrial veins when appropriately configured
and dimensioned. In the present invention, the bending stiffness of
distal section 22 of lead 10 is made variable so as to increase or
decrease in a predetermined singular or periodic fashion.
[0050] Thus, in one embodiment of the present invention distal
portion 22 of lead 10 has at least one distalmost stiff section 2
disposed distally of a flexible section 4 located adjacent thereto.
That is, lead body 12 may be configured to have at least one stiff
section 2 and at least one flexible section 4 located in distal
portion 22 thereof. Medical electrical lead 10 of the present
invention may additionally have adjacent adjoining portions which
alternate between being flexible and being stiff relative to one
another. More particularly, the flexibility or stiffness of
sections 2 and 4 of lead 10 may be more accurately characterized as
having different bending stiffnesses (S.sub.b), wherein the ratio
of the bending stiffness of the stiff section 2 (S.sub.bs) is at
least 1.5 times that of the bending stiffness of the flexible
section 4 (S.sub.bf). The bending stiffness ratios between more
flexible sections 4 and more stiff sections 2 of lead 10 may also
exceed about 1.8, about 2, about 2.2, about 2.4, about 2.6, about
2.8, about 3.0, about 4, about 5, about 6, about 7, about 8, about
9, about 10, about 20, about 30, about 40, about 50, about 100 or
even greater.
[0051] Expressed mathematically, the ratio of bending stiffnesses
of stiff sections 2 and flexible sections 4 of lead 10 of the
present invention are: 1 1.5 S bs S bf 100 ( eq . 1 ) 1.5 S bs S bf
20 ( eq . 2 ) 2 S bs S bf 10 ( eq . 3 ) 2 S bs S bf 5 ( eq . 4
)
[0052] When lead 10 is advanced through coronary sinus 13 into
great cardiac vein 23 and then into posterior cardiac vein 17, for
example, lead 10 will assume a winding, almost wave-shaped
configuration, such that distal portion 22 is curved at the
transition between coronary sinus 13 and posterior 1o cardiac vein
17 as well as along the pathway of posterior cardiac vein 17.
[0053] It has been discovered that lead 10 will attempt to assume a
position with minimal stored mechanical energy after having been
implanted within veins 17 and 13. It has further been discovered
that flexible sections 4 of lead 10 are most preferably located in
those portions of the venous pathway having the curves of smallest
radius (and therefore requiring the lowest amounts of stored
potential mechanical energy).
[0054] Thus, first radius of lead body curvature 36 shown in FIG.
1A and 1B is most preferably located along those portions of lead
10 which comprise flexible portion 4 of lead body 12. Likewise,
second, third and fourth radii of 20 lead body curvatures 38, 40
and 42, respectively, shown in FIG. 5 are likewise located along
portions of lead 10 comprising flexible portions 4. Relatively
straight portions of lead 10, implanted within human heart 1 in a
desired-position preferably comprise relatively stiff portions 2 of
lead body 12 as shown in FIG. 5.
[0055] In the present invention, therefore, moving flexible
sections 4 from their locations within first, second, third and
fourth curves 38, 40 and 42 requires that an axial force be exerted
on lead 10 to advance lead 10 distally (i.e., exertion of a pushing
force) or to retract lead 10 (i.e., exertion of a pulling force).
Thus, owing to the unique variation of bending stiffness along the
length and axial direction x of lead body 12 of lead 10, lead 10,
once implanted, has a pronounced tendency to remain implanted and
not to become dislodged from the cardiac vein within which it has
been implanted.
[0056] FIGS. 6A-6C illustrate various principles associated with
the foregoing discussion concerning FIGS. 1 and 5. The principle of
a relatively straight lead having variable bending stiffness as a
function of lead position is based on two mechanical laws: (1) a
mechanical body subjected to an external load or deformation
assumes a shape which minimizes the potential mechanical energy
stored in that body; and (2) variation of the stored potential
energy in a body with displacement of the body results from an
external force acting thereon. The external force (F) equals the
derivative of energy (E) with respect to displacement (x) as shown
below: 2 F = E x ( eq . 5 ) E x = b R b R b S b x = b S b x ( eq .
6 )
[0057] where S.sub.b=bending stiffness, R.sub.b=bending radius and
.phi..sub.b is the bend angle.
[0058] In FIG. 6A the additional energy stored in curved flexible
section 4 of lead body 12 is defined by the force F required to
displace lead 12 into the position shown along with the change in
displacement dX. FIGS. 6B and 6C illustrate that the amount of
bending energy required to bend lead body 12 through an approximate
90.degree. curvature is greater for the geometry shown in FIG. 6C
than is that illustrated in FIG. 6B. This is because stiff section
2 is located in the curved section of lead body 12 is FIG. 6C.
Greater bending energy is therefore required to bend lead body 12
into the configuration shown in FIG. 6C than the configuration
shown in FIG. 6B, where flexible section 4 is disposed along most
of the curved section. In other words, the lead configuration shown
in FIG. 6B is mechanically more stable than is the configuration
shown in FIG. 6C because the configuration of FIG. 6C achieves a
lower stored mechanical energy level.
[0059] Applying the law of minimum stored mechanical energy to the
distal section of lead 10, we can draw the following conclusions.
When lead 10 is implanted in coronary sinus 13 and great cardiac
vein 23, mechanical energy is stored in those curved sections of
lead 10 which are located in the transition from coronary sinus 13
to coronary vein 23 or 17. Such stored mechanical energy is
proportional to the stiffness of lead 10 and the length being
curved, as well as to the curvature (which is the inverse of the
bending radius). Assume that the curvature is determined mainly by
the venous anatomy, that the angle or curvature is about 90.degree.
and that the bend radius is about 5 mm. Such a curve will be
maintained by forces acting on both sides of the lead body. The
energy stored in lead body 12 is proportional to the average
stiffness in the curved section.
[0060] Because the stiffness in the curved section varies with the
position of the lead along the curve, the average stiffness of the
lead body disposed in the curve will change if the lead is moved
along the curve or the curve is moved with respect to the lead.
Thus, axial displacement x of lead 10 along the curve defined by
the venous anatomy results in a change in stored mechanical energy.
If a lead of the present invention has been implanted within the
venous anatomy of a patient properly, additional energy from an
external source (e.g., a physician pulling or pushing the lead
along the axial direction x) will have to be provided to displace
lead 10 from its preferred minimum stored mechanical energy
position.
[0061] It has been discovered that it is preferred to locate the
most flexible section of the lead in those portions of the venous
anatomy which exhibit the greatest curvature (or maximum bend
radii). In such a configuration, the stiffness of lead 10 increases
both proximally and distally with respect to the flexible section
disposed in the curved section, and thus the stored energy of the
lead body will become greater if the lead is moved either distally
or proximally, or the venous anatomy moves with respect to the lead
either distally or proximally. Stored mechanical energy is
maintained at a minimum when the flexible section remains in the
center of the curve. This results in a stable mechanical
equilibrium, which in turn requires that external force of
sufficient magnitude be exerted on lead 10 to move it distally or
proximally from its minimum stored mechanical energy position.
[0062] In accordance with some embodiments of the present
invention, lead may be configured to have one relatively stiff
portion 2 adjoining a relatively flexible portion 4, or may have a
series of alternating relatively stiff portions 2 and relatively
flexible sections 4. The bending stiffness of adjoining sections
may increase or decrease in step-wise fashion, or may increase or
decrease monotonically, exponentially or logrithmically. The
respective lengths of relatively stiff portions 2 and relatively
flexible portions 4 may also be varied according to the particular
venous anatomy in which lead 10 is to be implanted.
[0063] In one embodiment of the present invention lead 10 is
substantially straight prior to implantation and exhibits variable
stiffness in distal portion 22 thereof such that at least one
flexible section 4 adjoins proximally disposed and adjacent stiff
portion 2 and distally disposed and adjacent stiff section 2,
respectively. Such a lead configuration exhibits a bilateral,
stable equilibrium (see FIG. 7C).
[0064] In another embodiment of the present invention lead 10 has a
single stiff section 2 disposed in distal portion 22 which has a
relatively flexible section 4 disposed proximally therefrom and
adjacent thereto. Such a lead configuration has a unilateral,
mechanically stable equilibrium, wherein the bending stiffness
junction between sections 2 and 4 of differing stiffness is
optimally placed at either end of a curve in a venous anatomy (see
FIG. 7B). FIGS. 7A-7C illustrate the behavior of several selected
embodiments of lead 10 of the present invention, where bending
stiffness (S.sub.b) of lead body 12 is varied as a function of lead
axial position x. In each of FIGS. 7A-7C, the upper diagram
illustrates bending stiffness S.sub.b as a function of lead axial
position x, the middle diagram illustrates the derivative of stored
mechanical energy E with respect to axial distance x, (such
derivative of stored mechanical energy being proportional to the
axial force F.sub.ax exerted by the lead), and the lower diagram
illustrates a lead structure corresponding to the bending
stiffnesses and axial forces illustrated thereabove. In all of
FIGS. 7A-7C the distal tip of the lead is positioned at the right
side of the diagrams, relatively stiff portions of lead 10 are
indicated by numeral 2 and relatively flexible sections of lead 10
are indicated by numeral 4.
[0065] Referring now to FIG. 7A, the monotonic increase in bending
stiffness begins at the junction between sections 4 and 2 and
increases to a maximum is at tip 50. Such a configuration results
in an axial force (F.sub.ax) being exerted by lead 10 as shown in
the middle diagram. Here, as in other axial force diagrams which
follow below, a positive axial force is one which acts to pull the
lead in a distal direction, whereas a negative axial force acts to
pull a lead in a proximal direction (i.e., out of the vein within
which it has been implanted).
[0066] Referring now to FIG. 7B, there is shown a lead exhibiting a
step-wise jump in bending stiffness which occurs at the junction
between sections 2 and 4 thereof. Once distalmost stiff portion 2
has been pushed beyond the venous curve of interest, and flexible
section 4 is disposed in such curve, the 25 axial force (F.sub.ax)
exerted by distal portion 22 of lead 10 upon the venous anatomy is
again positive and tends to retain the lead in the implanted
position unless an axial pulling force operating in the proximal
direction is exerted on lead 10 to pull lead 10 around the curve of
interest to thereby overcome F.sub.ax.
[0067] FIG. 7C shows lead 10 having a series of contiguous
alternating relatively flexible and relatively stiff sections 2 and
4, respectively. Lead 10 shown in FIG. 7C exhibits a number of
points of bilateral stability separated by a distance equal to the
length of relatively flexible and relatively stiff 5 sections 4 and
2, respectively. Such a lead configuration has the advantage that a
tip or electrode thereof may be placed at any of several positions
along one or more coronary veins. That is, the embodiment of lead
10 shown in FIG. 7C has a number of different minimum mechanical
energy storage positions which it may assume within the venous
anatomy of a patient. The lo relative lengths of relatively
flexible portions 4 and relatively stiff portions 2 may be varied
according to the radii of the different venous curves which are
anticipated to be encountered during lead implantation.
[0068] Thus, if it is anticipated that lead 10 will be implanted in
a portion of the venous anatomy which is characterized by tightly
curved venous portions, is lead 10 may be configured to have
relatively short stiff and flexible sections 2 and 4, respectively,
to provide optimal results. Contrariwise, in the event the venous
anatomy to be encountered during the implantation process is
expected to be characterized by relatively gently curves, lead 10
may be configured such that relatively stiff sections 2 and
relatively flexible section 4 have longer lengths to thereby
provide optimal results. Lead 10 may also be appropriately
configured such that portions 2 and 4 are of appropriate differing
lengths for small, medium, and large radii curves encountered by
the same lead 10.
[0069] It is important to note that when relatively stiff portion 2
of lead 10 is disposed in or along a curved section of the venous
anatomy, an unstable mechanical equilibrium associated with a local
maximum of stored potential mechanical energy being disposed in the
curve results. It is therefore desired in the present invention
that lead 10 have alternating relatively flexible sections 4 and
relatively stiff sections 2 located within the venous anatomy in
such a way that relatively flexible sections 4 are located in at
least the major curves thereof.
[0070] The principle of varying the bending stiffness of lead 10 as
a function of axial distance x may also be expanded to cover
circumstances where the bending stiffness (S.sub.b) is symmetric
and equal around each axis of bending, or asymmetric and unequal
around each axis of bending.
[0071] Referring now to FIGS. 8A and 8B, there are shown in
cross-section lead body 12 exhibiting symmetric equal bending
stiffnesses around each axis of bending in FIG. 8A and lead body 12
having asymmetric unequal bending stiffnesses around each axis of
bending in FIG. 8B. Thus, lead 10 shown in FIG. 8A may be bent in
any direction from 0.degree. to 360.degree. without any change in
bending moment being required. Contrariwise, lead 10 shown in FIG.
8B requires more bending moment when lead 10 is bent in the
directions of 0.degree. and 180.degree., while less bending moment
is required when lead 10 is bent in the 90.degree. and 270.degree.
directions.
[0072] FIGS. 9A and 9B illustrate lead bodies which require
asymmetric bending moments as a function of angular direction. In
order to maintain minimal mechanical energy, lead body 12
illustrated in FIG. 9B will attempt to orient itself along the
plane of the curve within which it is disposed such that 20 bending
preferentially occurs over the lead axis along the most flexible
lead cross-section (e.g., the 90.degree. and 270.degree.
orientations). This characteristic may be exploited so that lead
body 12 may be oriented such that an electrode disposed along or
near such a section exhibiting asymmetric bending stiffness is
strategically placed within a vein. Thus, for example, a pacing or
defibrillation electrode 14 disposed near such an asymmetric
bending stiffness section may be oriented towards the myocardium
(which may be beneficial in obtaining low pacing thresholds and
improved sensing of signals).
[0073] FIG. 9A illustrates the natural orientation which the lead
of FIG. 8B will assume within a curved portion of the venous
anatomy. The lead configuration shown in FIG. 9B is one which
requires maximum mechanical energy and therefore will not be
assumed by lead 10 when disposed in a curved section of the venous
anatomy.
[0074] Referring now to FIG. 10, there is shown an enlarged
cross-sectional view of lead 10 disposed within posterior cardiac
vein 17 after having been routed through coronary sinus 13. FIG. 10
shows how venous vasculature exhibits curves having radii which
alternate in direction and magnitude. Bending of lead body 12 along
posterior cardiac vein 17 occurs substantially within a single
plane (i.e. R.sub.1R.sub.2 and R.sub.3 are disposed substantially
in the same plane). Because radii R.sub.1R.sub.2 and R.sub.3 are so
much smaller than radius R.sub.4, more radical bending of lead 10
is required in posterior cardiac vein 17. Bending of lead body 12
occurring along R.sub.4 of coronary sinus 13 occurs in a plane
which is approximately perpendicular to the plane along which
R.sub.1R.sub.2 and R.sub.3 are disposed. Note that R.sub.4 is
substantially longer than R.sub.1-R.sub.3 and thus the curve of
coronary sinus 13 is not only along a different plane but of
substantially less magnitude. Consequently, a preferential
orientation of lead 10 is determined principally by radii
R.sub.1-R.sub.3 rather than by radius R.sub.4. This, in turn, means
that a lead having an asymmetric cross-sectional configuration or
bending stiffness which varies asymmetrically as a function of
cross-sectional angular position may be successfully employed to
ensure the retention of lead 10 within a desired portion of the
venous anatomy. For example, lead 10 may be configured to have a
first asymmetric cross-sectional configuration for implantation
along the distalmost portions of a selected cardiac vein in a first
preferred orientation where bending radii are small, and to have-a
second asymmetric cross-sectional configuration for implantation in
or along more proximally disposed portions of the venous anatomy
and in a second preferred orientation, wherein the first and second
orientations are different owing, for example, to the first and
second cross-sections being angularly rotated in respect of one
another.
[0075] Assuming the embodiment of the present invention illustrated
in FIGS. 8B and 9A is employed for implantation within a desired
portion of the venous anatomy, such a lead will have two
orientations where stored mechanical energy will be achieved,
namely at .phi.=90.degree. or .phi.=270.degree., assuming that the
bending stiffness of the lead is equal in those opposite
directions. Electrode 14(b) may be positioned on one side or the
other of lead body 12 to stimulate a desired portion of the heart
as shown in FIG. 10. Such positioning may be confirmed through the
use of x-ray or echo identification of the orientation of electrode
14(b). If required, lead 10 may be rotated through 180.degree. such
that electrode 14(b) faces a desired direction.
[0076] FIG. 11 illustrates another embodiment of the present
invention, where lead 10 is adapted for implantation within right
atrium 3, coronary sinus 13 and a selected cardiac vein. The distal
tip 50 of lead 10 is disposed in the selected cardiac vein, while
proximal therefrom a portion of lead 10 having bending stiffness
characteristics which differ from those of the distalmost portions
of lead 10. More particularly, and referring now to FIG. 11 again,
it will be seen that distal portion 22 of lead 10 is characterized
in having a bending stiffness profile which alternates between
relatively stiff portions 2 and relatively flexible portions 4.
Proximal from such sections of alternating relatively stiff and
relatively flexible sections 2 and 4 there is disposed a section of
lead body 12 in which bending stiffness increases in the distal
direction, most preferably in the manner shown in FIG. 11. Note,
however, that the increase in bending stiffness shown over those
portions of lead 10 illustrated in FIG. 11 intended for
implantation in right atrium 3, and optionally at least portions of
coronary sinus 13, may increase monotonically, exponentially,
step-wise or logrithmically. The important point is that bending
stiffness over the portion of the lead implanted within the right
atrium and optionally at least portions of the Coronary sinus have
an increasing bending stiffness to create a force which will have a
tendency to push the lead in the distal direction, even after
implantation.
[0077] An outer layer or sleeve may surround lead body 12. Without
any limitation intended, the sleeve may be constructed from a
carbon coated silicone, steroid, steroid-eluting silicone, or a
combination of silicone and an anti-fibrotic surface treatment
element. Any of those compositions may help reduce tissue response
to lead insertion so that lead 10 will not cause clots or adhere to
the vessel wall, thereby allowing retraction of the lead in the
future, if necessary. These compositions may also help prevent
encapsulation of the electrode, thereby enhancing the effectiveness
of the pacing and sensing capabilities.
[0078] One or more electrical conductors are disposed on or in lead
body 12 and convey signals sensed by electrode 14 or permit the
delivery of electrical pacing or defibrillation signals
therethrough. Such conductors may be helically wound coils or
multistrand twisted cables, ETFE coated, or fixed within a
longitudinally disposed lumen of the lead body 12. The distal end
of lead conductor 16 may be attached to electrode 14 while the
proximal end thereof is attached to terminal pin 18 by crimping or
laser weld means well known to those skilled in the art. Without
any limitation intended, electrode 14 and terminal pin 18 may be
manufactured from titanium or platinum-plated titanium. Conductor
16 preferably comprises electrically conductive braided or stranded
wires. A lumen 30 may be formed within lead body 12 wherein a
stylet of known construction may be positioned therein.
[0079] Having generally explained the features and positioning of
lead 10, and referring now to the flow diagram of FIG. 12, some
methods of pacing and/or defibrillating a patient's heart using a
coronary vein lead 10 and implanting same will now be discussed.
The method of pacing a patient's heart identified in the flow chart
of FIG. 12 allows a user to effectively pace the left ventricle
without increased risk of an ischemic episode.
[0080] The operator first positions a guide catheter of the tear
away type known to those skilled in the art within coronary sinus
13 (block 150). Although the use of a guide catheter is not
absolutely necessary, a guide catheter increases the ability of the
operator to properly position lead 10 within a preselected coronary
vein. Once the guide catheter has been positioned within coronary
sinus 13, lead 10 is inserted through the lumen of the guide
catheter and into a predetermined coronary vein under fluoroscopic
observation (see Block 152). Lead 10 is positioned within the
selected coronary vein, wherein the electrodes of lead 10 are
aligned with the selected chambers to be paced. Those skilled in
the art will appreciate that the electrodes may be constructed from
a radiopaque material such that the position of the electrode is
readily determined. After lead 10 is appropriately positioned in
heart 1, the stylet or guide wire (if present) is removed from lead
10 (see block 154). The catheter is then removed from coronary
sinus 13 (block 156) and the catheter is torn away as the catheter
is pulled past the terminal pins of lead 10. Before removing the
catheter from lead, however, electrical measurements may be taken.
As noted above, a guide catheter may be used to direct a guide wire
which is used to guide a support catheter to a desired position
within a pre-selected coronary vein. The support catheter is then
used to position lead 10 as described above.
[0081] After the guide catheter has been removed, the operator
decides whether there are additional coronary vein leads to be
inserted and positioned within the coronary veins of a patient's
heart (see decision block 158). If other leads 10 are to be
positioned within pre-selected coronary veins, then the above steps
represented by blocks 150-156 are repeated (see loop 160). Those
skilled in the art will appreciate that an additional lead of
suitable construction could be positioned within the right atrium
or ventricle. If no other leads 10 are to be inserted and
positioned, then terminal pins 18 attached to each coronary vein
lead 10 are coupled to corresponding terminal ports of cardiac
stimulator 30 (block 162). Stimulator 30 is then programmed by
known means to transmit a pacing and/or defibrillation pulse
through each coupled lead 10 (block 164) to pace or defibrillate
the pre-selected chamber of the patient's heart.
[0082] For placement of the lead tip in the atrial appendix a
stylet is inserted and the lead pushed until the distal end of the
lead is in the right atrium. The stylet is replaced with a J-shaped
stylet to impart curvature on the distal end of the lead and to
place the tip in the desired location of the right atrial
appendix.
[0083] Once lead 10 of a suitable embodiment of the present
invention has been inserted and positioned in heart 1, and without
any limitation intended, the operator has the ability to, for
example, pace or sense both the left atrium and left ventricle, or
pace or sense the left atrium, left ventricle, and right atrium.
When a separate right ventricular lead is positioned, pacing and/or
sensing from all chambers of the heart may be possible. The
diameter and construction of lead 10 provides the flexibility
necessary to reduce substantially the likelihood that flexure of
lead 10 will result in the coronary vein being eroded through. In
this regard, the lead body 12 of lead 10 may be coated or
impregnated with a biomedical steroid to reduce the inflammatory
response of the coronary veins to the insertion and positioning of
lead 10 therein. The selected biomedical steroid may also be used
to reduce the amount of fiber build-up occurring between lead 10
and the coronary vein. Lead 10 may also be constructed to include
an anchoring member such that lead 10 may be additionally anchored
within the coronary vein or Coronary sinus.
[0084] Although specific embodiments of the invention have been set
forth herein in some detail, it is to be understood that this has
been done for the purposes of illustration only, and is not to be
taken as a limitation on the scope of the invention as defined in
the appended claims. Thus, the present invention may be carried out
by using equipment and devices other than those described
specifically herein. Various modifications, both as to the
equipment and operating procedures, may be accomplished without
departing from the scope of the invention itself. It is to be
understood that various alternatives, substitutions and
modifications may be made to the embodiment describe herein without
departing from the spirit and scope of the appended claims.
[0085] In the claims, means-plus-function clauses are intended to
cover the structures described herein as performing the recited
function and not only structural equivalents but also equivalent
structures. Thus, although surgical glue and a screw may not be
structurally similar in that surgical glue employs chemical bonds
to fasten biocompatible components together, whereas a screw
employs a helical surface, in the environment of fastening means,
surgical glue and a screw are equivalent structures.
[0086] All patents cited hereinabove are hereby incorporated by
reference into the specification hereof, each in its respective
entirety.
* * * * *