Note: Descriptions are shown in the official language in which they were submitted.
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S-A NODE HELICAL LEAD
FOR AERIAL PACEMAKERS
AND LOATHED OF PLACEMENT
I. DESCRIPTION
Technical Field
This invention relates to an improved electrode
for Senatorial (S-A) node contact in the atrium to pro-
vise aerial pacing or aerial synchronized pacing to pro-
serve the contribution of the aerial contraction in the
overall cardiac output and at the same time to provide an
electrical lead which permits minimization of surgical risk.
Background of the Prior Art
There are approximately 100,000 pacemakers implanted
annually, about 10~ are of aerial type. One of the major
limitations of this type of pacer is the lack of suitable
lead Even so, aerial and atrio-ventricular pacers are
being increasingly recommended, and used.
Velltricular stimulating pacemakers are the preferred
method of treatment for atrio-ventricular conduction defects,
however, 20% of these pacemakers are implanted in patients
with senatorial nodal disease. The reason that the venturi-
cuter pacemakers are used rather than aerial stimulating
pacemakers is mainly related to the difficulty in implanting
and lack of stability of aerial leads and the resultant poor
reliability of P-wave sensing and aerial pacing. By using
ventricular stimulating pacemakers, the patient with a normal
atrio-ventricular conduction system is deprived of the hero-
dynamic advantages of aerial systole. This imparted function reduces the patient's exercise tolerance and may result in
congestive failure in those patients with poor ventricular
function.
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The advantages of aerial pacemaking are real for
both tachycardia and bradycardia syndromes. At present,
several basic types of aerial pacemakers are available.
One type can be used to pace and sense in aria only.
This is merely a modified ventricular pacer. Another
senses the P-wave in the aria and then, following an
appropriate delay may stimulate the ventricle to pace
if the A-V conduction is blocked. Still another type
pacer has the ability to sense and pace in both the aria
and ventricle. The last two types of pacers may be
used in patients with complete A-V block while the last
type may be used with S-A nodal bradycardia A-V and/or
tachycardia syndromes.
Conventional transvenous ventricular lead
systems will not remain in place in the aria, therefore,
an aerial lead must be either sutured to the aria directly
or a special ~IJII shape aerial lead may be passed trays-
venously. It is this latter J-shaped lead system either
in unpiler or bipolar configurations which are preferred
mainly because of its transvenous placement.
Common forms of the J-lead electrode are disclosed in
US. Patent 3,939,~3 to Smith issued February I 1976 and
US. Patent 3,890,~77 to Wilson issued June 24, 1975~
The disac1vantages of the J-lead include a large
diameter (> 8 Fry French catheter diameter especially at
the radius bend required to maintain the curve; the difficulty
in placing such a large stiff lead; and a high dislodgement
rate as compared to ventricular leads. In addition, the
tip of the J-lead can only be positioned in one place
and that is in the aerial appendage, thus negating the
ability to position the electrode for minimum pacing thresh
hold and maximum Pow sensing
Others have resorted to the use of one or more
pliant tines which extend from the electrode tip at an
acute angle as "anchor" means to maintain the electrode
tip in position. Exemplary of this form of electrode is
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the electrode disclosed in US. patent 3,902,501 to
Citron et alp issued September 2, 1975.
Flexing of implanted electrodes has also been
a problem as such an electrode must flex in the order of
30 million times each year. The Cardiac US. Patent
3,348,548 issued October 24, 1967 and US. Patent
4,057,067 to Laos issued November 8, 1977 discloses
an electrode wherein the electrical conductor is in the
form of spring coils coated with electrically insulating
and body computable material which has now become a
fairly uniform procedure for constructing the electrode's
conductors.
It is also known to form a cardiac pacer lead
which is formable, at the time of pacer implantation by
heating the pacer lead as disclosed in the US. Patent
4,154,247 to Only issued May 15, 1979.
BRIEF SUMMARY OF THE INVENTION
This invention is directed to a new lead system
specifically designed for trail sensing and pacing.
Briefly stated, the invention is an improved
electrically conductive lead for at least S-A Node
Atrium Contact to provide atrium pacing and sensing
comprising an electrical conductor having a lumen there
through, an electrode tip, said electrode tip being
electrically connected to the electrical conductor
adjacent one end of the conductor, and S-A Wove helix,
said helix extending from the electrode tip toward the
other end of the electrical conductor a distance of 6 to
1 inches and having at least one-and-a-half turns and
a non-conductive biocompatible coating encasing the
electrical conductor except the electrode tip.
The wire electrical conductor coil itself may be
made of standard materials such as ~lgiloy*, MY 35N,
stainless steel or another corrosion-resistant biocompatible
material. It may be made in either unpiler or bipolar
in configuration. The bipolar configuration may have
the conductor wires side-by-side or coaxial.
The conductor or conductors may be coated with a
segmented polyurethane such as Bummer* or Pelathane*
*trade mark
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or other similarly biocompatible materials. The coating
material is preferably bonded or attached to the lead
wire either by a dipping or extruding process so that the
coating and wire become bonded, so that the coated
electrode will have the ability to be heat-set.
Preferably, the distal (tip) end of the lead
of 6-12 inches is wrapped around a circular mold and the
mold and electrode are placed in an oven or other heat
source to cause the lead coating to set and hold this
coiled or "pig-tailed" shape which, hereinafter will be
referred to as the S-A node helical shape.
BRIEF DESCRIPTION OF TOE DRAWING
The invention will be more particularly described
in reference to the accompanying drawing wherein:
FIG. 1 is a diagrammatic view showing a coiled
monopolar lead of the invention positioned in the aria
and gave with the spring tension on the lead holding the
tip of the lead at the S-A Node area;
FIG. 2 is a diagrammatic view showing the coiled
bipolar lead of the invention positioned in the aerial and
gave with the spring tension on the lead holding the tip
of the lead in the zone of the S-A Node;
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glue
FIG. 3 is a view of the lead of the invention
in a configuration suitable for insertion;
FIG. 4 is an enlarged fragmentary sectional view
of the portion of the lead illustrated in FIG. 1 with a
straightening style within the coiled conductor;
FIG. 5 is a view of a mold for forming the lead
of the invention;
FIG. 6 is a view of the lead illustrated in FIG.
2 in a formed configuration;
FIG. 7 is a fragmentary view of a portion of a
monopolar lead of the invention;
FIG. 8 is a view like FIG. 7 of a bipolar lead;
and
FIG. 9 is a fragmentary view in partial section
of a modified form of the invention.
Detailed Description of the Invention
One form of the invention will be specifically
described in reference to a unpiler pacer lead as thus-
treated in FIGS. 1, 3, 4, 5, 6, 7 and 9 of the drawing. The
lead, generally designated 10 has a connector portion 11,
electrode portion 12 and central portion 13. The cross
section of the central portion 13 may be as illustrated in
FIG. 4. That is, an electrical conductor formed of a
coiled member 15 having a void lumen 16 encased in an in-
sulfating material 17 which is generally inert in body fluids and tissue.
The wire electrical conductor coil 15 may be
formed of standard material such as ELGILOY, MP-35N,
stainless steel, DUBS or other corrosion resistance
biocompatable material.
The conductor coil 15 diameter may be the standard
0.040 inch or preferably have a larger helical coil die-
meter such as 0.065 for added flexural strength. The
coil 15 is preferably coated with a segmented polyurethane
17 such as Bummer or Pelathane or other similarly boo-
compatible materials. The coating material is preferably
bonded or attached to the lead wire either by a dipping
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or extruding process so that the coating and wire become
bonded. A coating to provide overall outside diameter
in the order of (< 6 Fry is maintained and yet the lead
will have improved strength and have the ability to be
headset. The distal tip end of the lead 10 for 6-12 inches
is wrapped around a circular mold 18 with a diameter of
between one and three inches. This mold's diameter,
and thus the lead's resultant coil diameter should be
approximately one and one-half to two times the diameter
of the superior vent gave into which the lead is to be
inserted. The lead end should encircle the mold so that
between one and three complete revolutions are made,
either clockwise or counter-clockwise, as detailed here-
inciter. The lead is then placed in an oven or other
heat source to cause the lead coating to set and hold
this coiled or "pig-tailed" shape. For the segmented
polyurethane material (Bummer or Pelethane) a temperature
range of 260-275F for 45 minutes is adequate.
In construction of the lead, selecting a lead
having a coil diameter in the range of about 0.020 to
about 0.100 and preferably about 0.060 for the conductor
coated with a segmented polyurethane to an outside die-
meter in the order of 4-8 Fur heat set for about 30-120
minutes at a temperature range of 250-350 and preferably
about 260F the resulting coil is slinky or weak that it
does not matter which way the lead it wound onto the mold
18 that is whether the lead is wound clockwise or counter-
wise. The subsequent twisting, axially of the lead clock-
wise, after placement in the atrium cause the lead to form
a clockwise helix. However, with a larger diameter conductor
coil, or a heavier or thicker coating of segmented polyp
urethane, or a higher setting temperature or a longer setting
time or a combination of more than one of these factors,
which results in a stiffer lead, it would be necessary to
wind the lead on the mold in a clockwise direction for heat
setting. Further, it will be appreciated that the heat
set coil can not properly function unless the normal
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body movements are sufficient to cause the helical coil
to expand and contract, otherwise body movement may cause
the electrode tip of the lead to move from its S-A rode
sensing position.
alternate to heat-setting the urethane coating,
conductive wire with a special memory helical coil that
would cause the lead to retain the S-A nodal coiled
shape and yet be able to stretch could be used.
In the lead of the invention the distal portion
of the lead is coiled for at least 1 1/2 to 2 1/2 complete
or more turns in the unretracted state. This is necessary
to maintain the stretched helical coil configuration when
traction is used to position the electrode at the S-A
Node area.
In general the diameter of the distal helical
coil or twist in the lead is based upon the gave diameter.
It must be a diameter larger than the gave (probably 1 1/
to 2 times). This then allows the lead to extend out into
slinky or soft spring coil in the gave when traction is
applied to the connector end thereof and acts as a shock
absorber spring when the body or heart move. The lead then
is held in place by the action of tip extending into and
hooking around into the aria at the coveter junction
and the coil trying to return to its original configuration.
although a coil diameter ox approximately 0.060
inch would seem optimum, smaller (0.020) and larger coils
(0.10) may also be adaptable depending on the method and
materials used in construction. In addition, in the bit
polar version, which may be preferred mode, the coils
could be coaxial (0.020 inside an 0.060) or side-by-side
(two 0.040 inch coils).
The conductor 15 is in electrical contact with
a conductive tip 12 and extends from the conductive tip
12 through the central portion 13 and the connecting port
lion 11 and into electrical contact with a connecting
pin 20. The connecting pin 20 is adapted for connection
with a remote electrical device in known manner and has
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a lumen there through coincident with the lumen 16 of the
conductor 15. With this configuration, it is possible to
insert a stilt 22 through the end of the connecting pin
20, through the lumen 16 of conductor 15 into abutment with
the conducting tip 12. The electrically conductive tip
12 may be of any material suitable for the environment,
platinum-iridium, for example.
In use, a style 22, of conventional form, is
inserted down the center as stiffener and straightener
much the same way as one would use a conventional lead.
The lead is then passed transvenously into the
patient's heart so the lead's tip electrode is in the
aria (FIG. 1). The style is then removed so that the
lead is urged to return to its original coiled configuration
in the aria.
Now gentle traction is placed on the connector
end of the lead so that the lead is being withdrawn from
the heart. As the leads withdrawn, the end of the coil
closest to the connector begins to be pulled out of the
heart into the gave. The distal coil end of the lead
with the electrode tip or electrodes (if a bipolar con-
figuration is used) remains in the aria longest because the
lead's helical coil diameter is larger than that of the
gave. As more of the lead is withdrawn, several clock-
wise axial turns of the lead are made via the connector hub 11, causing the lead to be stretched and corkscrew-
like or helical in appearance similar to that of a
stretched spring foggily).
These clockwise turns are transmitted down the lead
causing the lead to assume its helical coiled configuration
and causing the electrode tip 12 to rotate into contact
that the S-A Node area 28. The clockwise axial turns
imparted to the lead are made regardless of whether the
lead was wound and heat set in the clockwise or counter-
clockwise direction.
While the lead is being withdrawn the leads position is monitored fluoroscopically. The P-wave
amplitude also maybe observed electrocardiographically
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by monitoring between the tip and subcutaneous ground
(unpiler lead) or between the tip and the ring (bipolar
configuration). The lead may be~witharawn until the tip
is placed in the coveter junction (FIG. 1). It is this
position that is the anatomic location of the S-A Node
and where maximum P-wave amplitude may be detected.
Once positioned, the lead is ligated at 30
(FIG. 1), in place at the pacemaker implant site and
connected to a pacemaker. Stability of the leads main-
twined because the spring tension of the lead in thecava allows the lead to move freely in and out as the
lead tries to return to its preset coil diameter. The
gave will hold the lead stably in this elongated spring
or corkscrew shape and the tip will continue to be
gently but firmly lodged at the S-A Nodal area 28 (FIG.
1 and 2).
Referring now to FIGS. 2 and 8 there is thus-
treated a bipolar form of the lead of the present invention.
In FIGS. 2 and 8 10' generally designates the
bipolar lead having a connector portion 11', an electrode
portion 12', a space ring conductor 32 and a central
portion 13'. The electrode tip 12' of the lead 10' is
connected to the connector 11' via a wire electrical con-
doctor coil 15' whereas the ring electrode 32 is electrically
connected to the connector 11' via the wire electrical
conductor coil 34.
The two conductor coils 15' and 34 are separated
electrically by an insulating layer 36 which may comprise
segmented polyurethane as is the outer insulating material
17 as discussed in reference to the unpiler pacer lead
herein before described.
The inner conductor 15' is provided with a void
lumen such as lumen 16 of the unpiler lead. The lumen
is sized to receive the style designated 22' which style
is employed to straighten and stiffen the electrode during
insertion of the patient's atrium. In an example of a
bipolar lead the ring electrode 32 area would be in
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the order of 25 to 75 square millimeters and would be
spaced from, for example, 1.5 to 3 centimeters from the
tip electrode 12'.
Referring now specifically to FIG. 2, it will
be noted that the electrode tip 12' is positioned sub-
staunchly at the S-A Node which then positions the ring
electrode 32 a few centimeters toward the superior vent
gave from the S-A Node. It is not necessary that the
ring electrode 32 be in actual contact with any portion
of the aria as the blood in the aria acts as an electrical
conductor thereby transmitting electrical signals from
the aria to the ring electrode.
As in the case of the unpiler electrode approxi-
mutely 6-12 inches of the distal end thereof is for example
wrapped about a cylindrical mold and maintained in such
wrapped conditions until the segmented polyurethane ox-
tenor insulative coating 17' and/or the internal insulator
36 are heat set to provide the lead with a coiled or "pig-
tailed" configuration.
As described in reference to the unpiler lead,
the lead 10' is coiled for at least one-and-a-half to
two-and-a-half or more complete turns in the unretracted
state.
Insertion and placement of the bipolar lead is
the same as that employed in placement of unpiler lead
and will not be repeated herein.
Referring to FOG. 9 there is shown a modified form
of the present invention, wherein the helical coil con fig-
unction is imparted by the electrical conductor rather than
by the heat set biocompatible coating as described in
reference to the other forms of the invention.
In FIG. 9, 10'' generally designates a single
conductor lead comprising a metallic conductor coil 15'',
and insulating biocompatible coating 17'' which may
consist of urethane, silicone rubber or the like. At
the distal end of the conductor coil 15" is an electrode
tip 12'' and at the opposite end is a connector portion 11''
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having a male connector pin 20''.
The wire coil conductor 15'' is constructed of
heavier yaugewire than the conductors 15 and 15', which
conductor coil is heat treated or tempered to maintain
the helical configuration. It is only necessary that
the heavier gage wire comprise the distal end portion
of the lead or, 6 to 12 inches.
Where this form of the invention is employed
in a two conductor configuration for bipolar sensing
only the outer most wire conductor of a coaxial con-
figuration would be required to have the helical
memory imparted thereto.
The advantages of the leads of the invention
lie in their ease of placement, their long term stability
and the position of the tip in a more electrically active
area of the aria. Placement is simply a matter of
inserting a stylet-straightened lead, removing the
straightening wire, turning the lead clockwise axially
about two turns, then withdrawing the lead several inches
to stretch the coil out in the gave. The tip remains
stable against the aria wall at the S-A nodal area.
By having this coiled configuration, the lead can move
around in the gave, yet it will remain sprung out
against the walls. This lead relies on the heart's
own anatomy and the helical coil itself acts as a shock
absorber trying to return a preset diameter. Thus the
lead is passively fixed and less irritating to the heart
and conductive tip of the lead is placed at the S-A
Nodal area.
