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Medical Patent Abstract
A header assembly for coupling a medical electrical lead to a medical
stimulating device includes a header having a first bore for receiving
a proximal terminal pin of the lead. A connector block coupled to
the header has a second bore aligned with the first bore and a tapped
bore transverse of, and in communication with, the second bore,
and the assembly includes a setscrew with mounting threads of defined
length threadedly engaged with the tapped bore. The tapped bore
defines a tapped region adjacent the second bore, and a smooth bore
region which is longer than the length of the threaded portion of
the setscrew to prevent the setscrew from being completely backed
out of the tapped bore.
Medical Patent Claims
What is claimed is:
1. A header assembly for coupling a medical electrical lead to
an implantable medical device, the header assembly comprising: a
connector block coupled to the header and having a first bore for
receiving a proximal terminal pin of the medical electrical lead
and a tapped bore in communication with the first bore, the tapped
bore defining proximal and distal ends; and a setscrew comprising
mounting threads of a defined length; wherein the tapped bore defines
a distal tapped region and a smooth bore region proximal of the
distal tapped region, the smooth bore region longer than the defined
length of the mounting threads; and wherein the tapped bore further
defines a proximal tapped region proximal to the smooth bore region.
2. A header assembly as set forth in claim 1 wherein one end of
the setscrew is formed to engageably receive a tool for tightening
the setscrew into engagement with the proximal terminal pin of the
medical electrical lead and, alternatively, for withdrawing the
setscrew from engagement with the proximal terminal pin of the medical
electrical lead.
3. A header assembly as set forth in claim 1 wherein the connector
block has a square shoulder at the interface between the distal
tapped region and the first bore.
4. A header assembly as set forth in claim 3 wherein the setscrew
defines a tip end that extends distally from the mounting threads
and configured to extend into the first bore.
5. A header assembly as set forth in claim 1 wherein the connector
block defines a shoulder at the interface between the proximal tapped
region and the smooth bore region.
6. A header assembly as set forth in claim 1 wherein the distal
tapped region extends to an outer surface of the connector block.
7. A connector system for use with a sealed implantable medical
device having a medical electrical lead receiving bore for slidably
receiving a proximal terminal pin of an electrical lead, the lead
receiving bore having an open end for receiving the proximal pin
and a closed end, the connector system comprising: a pulse generator
operative to generate electrical stimuli; a sealed housing containing
the pulse generator; a header having a first bore for receiving
the proximal terminal pin of the medical electrical lead; a connector
block coupled to the header and having a second bore aligned with
the first bore and a tapped bore transverse of, and in communication
with, the second bore; and a setscrew comprising a mounting shank
at a head end and mounting threads of defined length adjacent a
tip end; wherein the tapped bore has a first tapped region and a
smooth bore region which is longer than the defined length of the
mounting threads of the setscrew; and wherein the tapped bore further
defines a second tapped region proximal to the smooth bore region.
8. A header assembly as set forth in claim 7 wherein the head end
of the setscrew is formed to engageably receive a tool for tightening
the setscrew into engagement with the proximal terminal pin of the
medical electrical lead and, alternatively, for withdrawing the
setscrew from engagement with the proximal terminal pin of the medical
electrical lead.
9. A header assembly as set forth in claim 7 wherein the connector
block has a square shoulder at the interface between the second
tapped region and the smooth bore region.
10. A header assembly as set forth in claim 7 wherein the distal
tapped region extends to an outer surface of the connector block.
11. A header assembly as set forth in claim 7 wherein the connector
block has a square shoulder at the interface between the first tapped
region and the smooth bore region.
12. In combination, a connector block and a lead-locking setscrew
for use in a header of an implantable pulse generator, the header
having a first bore for receiving a proximal terminal pin of a medical
electrical lead, comprising: the connector block coupled to the
header and having a second bore aligned with the first bore and
a tapped bore transverse of, and in communication with, the second
bore; and a setscrew comprising mounting threads of defined length;
wherein the tapped bore has at least one tapped region and a smooth
bore region which is longer than the defined length of the mounting
threads of the setscrew; and wherein the tapped bore further defines
a proximal tapped region proximal to the smooth bore region.
13. A header assembly as set forth in claim 12 wherein the head
end of the setscrew is formed to engageably receive a tool for rotating
the setscrew.
14. A header assembly as set forth in claim 12 wherein the connector
block has a square shoulder at the interface between the tapped
region and the second bore.
15. A header assembly as set forth in claim 12 wherein the connector
block defines a shoulder at the interface between the proximal tapped
region and the smooth bore region.
16. A header assembly as set forth in claim 12 wherein the distal
tapped region extends to an outer surface of the connector block.
Medical Patent Description
FIELD OF THE INVENTION
This invention relates to headers for coupling a lead for a tissue
stimulating devices, such as a cardiac pacemaker or implantable
cardioverter-defibrillator, to a pulse generator, and more particularly
to a mechanical connector which incorporates a unique setscrew retention
construction.
BACKGROUND
Implantable medical tissue stimulators including pacemakers, defibrillators
and neural stimulators are used to stimulate tissue such as cardiac
tissue or spinal cord tissue with electrical pulses. Such tissue
stimulators are now quite common and typically include a hermetically
sealed housing or can containing an electronic circuit and power
supply for producing electrical impulses under control of a programmed
microprocessor. The pulse generator is connected to target tissue
by means of a suitable medical lead. Such leads typically include
an elongated flexible lead body having a proximal end and a distal
end. Disposed at the distal end of the lead are one or more tissue
contacting electrodes. The electrodes are connected by wires running
through the lead body to associated contacts on a terminal pin at
the proximal end of the lead.
The proximal lead terminal pin is adapted to be inserted into a
longitudinal bore formed in a header of the stimulating pulse generator.
Contained within the header are one or more conductive connector
blocks that are connected to feedthrough pins that pass through
hermetic seals to join with input and/or output nodes of the electronic
circuit contained within the housing. The connector blocks will
typically have apertures formed therethrough in alignment with the
bore of the header, allowing the proximal lead terminal pin to be
inserted through them. To lock the lead in place, the connector
blocks will typically include a threaded bore that extends transverse
to the longitudinal direction of the bore in the header. Setscrews
are inserted into these threaded bores and tightened down against
contact areas on the proximal lead terminal. In prior art connector
block designs, from time to time the setscrew is accidentally backed
out completely from the block and could not be re-inserted in to
the block. Another equally problematic situation occurs when the
lead is not inserted in the connector block and the setscrew is
advanced to the extent that it falls into the longitudinal bore
of the block which is an extension of the longitudinal lead receiving
bore of the header.
U.S. Pat. No. 5,989,077 to Mast et al. provides an example of a
header assembly of the type which the present invention seeks to
avoid. Specifically, the header assembly serves for coupling a cardiac
lead to a cardiac stimulator and employs a setscrew threadedly coupled
to a connector housing of the header assembly but without provision
for retaining it in place so that it neither backs out of the tapped
bore in which it is received or advances too far in the absence
of an end of a lead which it is intended to engage.
In U.S. Pat. No. 5,000,177 to Hoffmann et al., an implantable system
is provided in which setscrews are confined within bores of the
connector block against advancing too far but, not with standing
the provision of plug seals over their heads, are capable of being
backed away from their threaded condition.
In U.S. Patent Application Publication US 2004/0225334 to Persuitti
et al., a connector block and its associated locking setscrew for
an implantable electronic tissue stimulating device are designed
to eliminate thread damage to the setscrew which is a cause of the
setscrew becoming stuck in the connector block. In this disclosure,
there is no concern presented for the problem addressed by the present
invention.
It was in light of the foregoing that the present invention was
conceived and has now been reduced to practice.
SUMMARY
A header assembly for coupling a medical electrical lead to a medical
stimulating device includes a connector block coupled to the header,
the connector block including a first bore to receive a terminal
pin of a lead and a tapped bore in communication with the first
bore. The assembly also includes a setscrew with mounting threads
of a defined length. The tapped bore has a tapped region proximate
the first bore, and a smooth bore region next to the tapped region
which is longer than the length of the threaded portion of the setscrew.
Thus, when a clinician backs out the setscrew, the threads of the
setscrew will disengage from the tapped region of the tapped bore
and reside in the smooth bore region. Because the setscrew is disengaged
from the tapped region, the clinician will be unable to further
unscrew the setscrew from the tapped bore, thereby retaining the
setscrew within the tapped bore. Furthermore, with the setscrew
residing in the smooth bore region, the clinician will have an indication
that the setscrew has been sufficiently unscrewed for removal or
insertion of the proximal pin of a lead.
Other and further features, advantages, and benefits of the invention
will become apparent in the following description taken in conjunction
with the following drawings. It is to be understood that the foregoing
general description and the following detailed description are exemplary
and explanatory but are not to be restrictive of the invention.
The accompanying drawings which are incorporated in and constitute
a part of this invention, illustrate one of the embodiments of the
invention, and together with the description, serve to explain the
principles of the invention in general terms. Like numerals refer
to like parts throughout the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and other features of the present invention
are explained in the following description, taken in connection
with the accompanying drawings, wherein:
FIG. 1 is an exploded perspective view of an implantable medical
device embodying the present invention, illustrating a sealed pacemaker
housing and its associated header assembly, and an associated lead
ready for insertion into a receiving channel of the connector;
FIG. 2 is a side elevation view of a connector block according
to one illustrative embodiment;
FIG. 3 is a top plan view of the connector block illustrated in
FIG. 2;
FIG. 4 is a cross section view taken generally along line 4--4
in FIG. 3;
FIG. 5 is a detail cross section view, in elevation, illustrating
in greater detail a portion of FIG. 4;
FIG. 6 is a perspective view of a setscrew according to one illustrative
embodiment;
FIG. 7 is a top plan view of the setscrew illustrated in FIG. 6;
FIG. 8 is a side elevation view of the setscrew illustrated in
FIGS. 6 and 7;
FIG. 9 is a cross section view taken generally along line 9--9
in FIG. 8;
FIG. 10 is a side elevation view in section illustrating one relative
position of the combination of the connector block and the setscrew;
FIG. 11 is a side elevation view in section illustrating another
relative position of the combination of the connector block and
the setscrew;
FIG. 12 is an exploded perspective view of another embodiment of
a connector block and setscrew;
FIG. 13 is a cross-sectional view of the connector block and setscrew
of FIG. 12 in an assembled state; and
FIG. 14 is a cross-sectional view similar to FIG. 13 and showing
another illustrative embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Turn now to the drawings and, initially to FIG. 1 which generally
illustrates, diagrammatically, an elevation view of a header assembly
or connector system 40 for a sealed implantable medical device such
as a cardiac stimulation device 16, possibly in the form of a pacemaker.
Although the present invention will be described with reference
to the embodiments shown in the drawings, it should be understood
that the present invention can be embodied in many alternate forms
or embodiments. In addition, any suitable size, shape or type of
elements or materials may be used.
In order to appreciate the advantages of the present invention,
it will help first to have a basic understanding of the manner in
which the mechanical and electrical connection functions are carried
out in known cardiac stimulation devices, a pacemaker here being
exemplary. The main components associated with the connection function
of such known pacemakers are shown diagrammatically in FIG. 1 but
apply to the present invention as well. A pacemaker 10 electrically
includes a battery 14 that powers electrical circuits 12. The pacemaker
electrical circuits 12 and battery 14 are mechanically enclosed
and hermetically sealed in a suitable housing 16. Typically, this
housing or case 16 is shaped to include a flat side or platform
20 to which a suitable header assembly 22 can be mounted. At least
one feedthrough terminal, 18, in electrical contact with the electrical
circuits 12, passes through the case or housing 16 and protrudes
beyond the platform 20. This feedthrough terminal 18 is electrically
isolated from the case 16. A platinum wire 24, or other suitable
conductive element, connects the terminal 18 to a conductive connector
block 26 that is fitted within the header assembly 22. A pacemaker
lead 28 having a proximal electrode or terminal pin 30 connects
to the pacemaker electrical circuits by inserting the terminal pin
30 into a receiving channel or first bore 31 of the header assembly
22 until the terminal pin 30 is in contact with the connector block
26 by way of a block receiving channel or second bore 31a. A setscrew
32 is then securely tightened using a tool 34 such as a torque wrench
to firmly hold the electrode 30 in both mechanical and electrical
connection with the connector block 26. A septum, not shown but
typically having the construction generally described in commonly
assigned U.S. Pat. No. 5,509,928 issued Apr. 23, 1996 to Acken,
may be placed over the setscrew 32 in order to prevent body fluids
from seeping through the setscrew hole. Further, sealing ribs or
ridges 36 on the connecting end of the pacemaker lead are designed
to tightly engage the inside edges of the receiving channel 31 in
order to prevent any body fluids from entering into the receiving
channel 31 once the connecting end of the lead has been inserted
into the header assembly 22.
While the descriptions presented in the prior art vary greatly
relative to, for example, different types of locking mechanisms
for performing the mechanical connection function, or different
types of arrangements for performing the electrical feedthrough
function, including the use of bipolar or multiple pacemaker leads,
all such systems include the use of a pre-molded or cast header
assembly 22 that is bonded to a sealed pacemaker housing 16 in which
the electrical circuits are located.
Typically, prior art header assemblies 22 are cast in place from
epoxy to the platform 20 of the pacemaker or, using more recent
technology, a pre-molded header assembly may be mounted to the platform
using a suitable sealing and bonding agent. Further, once the electrical
connection is made from the terminal post 18 to the connector block
26, and the header assembly is attached to the housing, all remaining
voids within the header 22, not including the receiving channel
31 into which the proximal end of the pacemaker lead 28 is to be
inserted, must be filled with a suitable filler material, such as
a two-component epoxy or silicone rubber.
It was earlier mentioned that the focus of the present invention
is to provide retention features for the setscrew for a pair of
potential problematic situations. By using the teachings of the
invention, the setscrew 32 will not be able to be advanced all the
way in or backed out completely from the connector block. For an
explanation of the specifics of the invention, while continuing
to view FIG. 1, turn now also to FIGS. 2 to 9.
As earlier noted, the connector block 26 (see FIGS. 2, 3, 4, and
5) is suitably coupled to the header assembly 22 and has the second
bore 31a aligned with the first bore 31 and a tapped bore 42 provided
in the connector block 26 has an axis transverse of, and in communication
with, the second bore. Associated with the connector block is the
setscrew 32 (see FIGS. 6, 7, 8, and 9) which extends from a mounting
shank 44 at a head end 46 to mounting threads 48 of a defined length
49 adjacent a tip end 50. The tapped bore 42 of the connector block
26 has first and second tapped regions 52, 54, respectively, spaced
by a smooth bore region 56 which is longer than the defined length
49 of the mounting threads 48 of the setscrew 32.
Turn now to FIGS. 10 and 11 in addition to the prior figures. FIGS.
10 and 11 illustrate another embodiment of the connector block 26
and in this embodiment, the connector block is indicated by reference
numeral 26b and all other components in this connector block embodiment
are indicated by similar reference numerals with the suffix "b".
The setscrew 32 is threadedly engaged with the tapped bore 42, 42b.
The head end 46 of the setscrew 32 is formed, as at 57, to engageably
receive the tool 34 (FIG. 1) for tightening the setscrew into engagement
with the proximal terminal pin 30 of the medical electrical lead
28 and, alternatively, for withdrawing the setscrew from engagement
with the proximal terminal pin of the medical electrical lead. With
particular attention to FIGS. 10 and 11, it is seen that the connector
block 26b has a square shoulder 58b at the interface between the
second tapped region 54 and the second bore 31b engageable with
a shoulder 60 of the setscrew 32 spaced from the tip end 50 to prevent
the setscrew from advancing farther into the second bore. It will
be-understood that, in the instance of the connector block 26 of
FIGS. 4 and 5, if the diameter of the bore 31a is larger than the
length of the setscrew 32, the setscrew could advance until it deleteriously
falls into the bore 31a. The altered construction of the connector
block 26b illustrated in FIGS. 10 and 11 prevents this occurrence.
With this construction, as the setscrew 32 is tightened into engagement
with the tapped bore of the connector block, it has already been
threaded through the first tapped region 52, 52b and resides within
the smooth bore region 56, 56b, and then becomes threadedly engaged
with the second tapped region 54, 54b until the tip end 50 is firmly
engaged with the proximal terminal pin 30 of the medical electrical
lead 28 extending through the first bore 31 and into the second
bore 31a, 31b. It will be appreciated that with the tip end 50 of
the setscrew 32 engaged with the proximal terminal pin 30, a space
will exist between the shoulder 60 of the setscrew and the square
shoulder 58b of the connector block 26b. Should the proximal terminal
pin 30 be removed from the bore 31b, the setscrew 32 can then be
advanced but only to the extent that the shoulder 60 engages the
square shoulder 58b and farther advance of the setscrew is halted.
Although the setscrew 32 can be loosened from its engagement with
the proximal terminal pin 30, it can no longer leave the confines
of the tapped bore 42, 42b because the tool 34 used for its initial
advancement into the connector block 26, 26b is incapable of applying
an oppositely directed force for its removal from the connector
block. More specifically, the defined length 49 of the mounting
threads 48 of the setscrew 32 is shorter than the length of the
smooth bore region 56, 56b. With the setscrew freely residing within
the smooth bore region, it would be necessary to pull the setscrew
toward the first tapped region 52, 52b but the tool 34 has no such
capability. Hence, once the setscrew 32 is advanced into the smooth
bore region 56, 56b, it remains in the tapped bore 42, 42b for the
life of the connector block unless extraordinary steps are taken.
Referring now to FIGS. 12 and 13, yet another embodiment of a connector
block 100 is shown. Connector block 100 is formed having the first
bore 102 and transverse, tapped bore 104 that receives a setscrew
106, similar to the embodiments described above. However, tapped
bore is not formed having two tapped regions, but instead has only
a single tapped region 108 adjacent the distal end of tapped bore
104. Rather than being threaded, proximal end of tapped bore 104
includes a retaining washer 110 that defines a relatively narrow
opening. Retaining washer 110 is received in a countersunk portion
of tapped bore 104 defining a recess 111 and may either be press
fit into recess 111, or placed in recess 111 and then spot welded
to remain in place, or any other suitable method of securing retaining
washer 110 in recess 111.
Thus, retaining washer 110 provides a shoulder that prevents setscrew
106 from being removed from tapped bore 104. As with the above-described
embodiments, tapped bore 104 includes a smooth bore region 112 whose
length is longer than the threaded portion of setscrew 106. As such,
setscrew 106 cannot be unscrewed and backed out of tapped bore 104,
because the threads will disengage from the tapped region 108 while
setscrew still resides in tapped bore 104. Moreover, retaining washer
110 prevents setscrew 106 from exiting tapped bore 104.
As described above, in one embodiment the distal end of tapped
bore 104 is preferably formed with a shoulder or tapering threads
(not shown) to prevent setscrew 106 from being over-advanced into
the first bore 102.
FIG. 14 depicts still another embodiment of a connector block 200
and setscrew 202. In this embodiment, a first bore 204 is provided
to accept the proximal pin of a lead, and transverse bore 206 is
provided to receive setscrew 202. Transverse bore 206 extends from
one end of connector block 200 to the other end, and differs in
that regard from the other embodiments described herein. Furthermore,
transverse bore 206 defines a tapped region 208 that extends from
the bottom of block 200 into the upper portion of block 200, and
then transitions to a smooth bore region 210 similar to the smooth
bore regions of the other embodiments described herein.
Connector block 200 is further formed having an integral shoulder
212 at the upper end of block 200, which replaces the retaining
washer 110 shown in FIGS. 12 and 13.
Thus, in the embodiment of FIG. 14, setscrew 202 is installed through
the bottom of block 200. Once setscrew is threaded upwardly through
the transverse bore 206 until it resides in the smooth bore region
210 (as shown in FIG. 14), setscrew 202 is retained within transverse
bore 206 by shoulder 212. A proximal terminal pin may then be inserted
into first bore 204, and setscrew 202 may be advanced through transverse
bore 206 until setscrew 202 engages the terminal pin. To remove
the terminal pin from connector block 200, setscrew 202 is unscrewed,
either partially until the terminal pin may be removed, or unscrewed
completely until setscrew 202 resides in the smooth bore portion
of transverse bore 206. In either case setscrew 202 is retained
within connector block 200 and there is no concern of setscrew 202
being removed from connector block 200.
It should be understood that the foregoing description is only
of illustrative embodiments. Various alternatives and modifications
can be devised by those skilled in the art without departing from
the invention. Accordingly, the present invention is intended to
embrace all such alternatives, modifications and variances which
fall within the scope of the appended claims.
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