U.S. patent application number 12/424298 was filed with the patent office on 2009-10-15 for bundle of his stimulation system.
Invention is credited to Matthew S. Finlay, G. Shantanu Reddy.
Application Number | 20090259272 12/424298 |
Document ID | / |
Family ID | 40771052 |
Filed Date | 2009-10-15 |
United States Patent
Application |
20090259272 |
Kind Code |
A1 |
Reddy; G. Shantanu ; et
al. |
October 15, 2009 |
BUNDLE OF HIS STIMULATION SYSTEM
Abstract
A system for therapeutically stimulating a His bundle includes
an implantable pulse generator and a multi-polar medical electrical
lead. The generator is configured for subcutaneous implantation and
to generate a pacing stimulus. The lead includes a connector
assembly, a flexible tubular body, a distal tip assembly and coil
conductors. The body extends intravascularly from the generator to
a location proximate the His bundle and includes a proximal end, a
distal end, and a longitudinal lumen. The tip assembly includes an
electrode, a fixation helix, and a shank portion. The helix extends
to a location proximate the His bundle and is operable as an
electrically isolated electrode. The shank portion extends within
the lumen and includes a receptacle for receiving a stylet tip. The
conductors extend longitudinally through the lumen and are coupled
to the electrode and the helix. One or both of the conductors
defines a stylet lumen.
Inventors: |
Reddy; G. Shantanu;
(Minneapolis, MN) ; Finlay; Matthew S.;
(Minneapolis, MN) |
Correspondence
Address: |
FAEGRE & BENSON LLP;PATENT DOCKETING - INTELLECTUAL PROPERTY (32469)
2200 WELLS FARGO CENTER, 90 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402-3901
US
|
Family ID: |
40771052 |
Appl. No.: |
12/424298 |
Filed: |
April 15, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61045168 |
Apr 15, 2008 |
|
|
|
Current U.S.
Class: |
607/28 ; 607/37;
607/9 |
Current CPC
Class: |
A61N 1/0573 20130101;
A61N 1/362 20130101; A61N 1/0565 20130101 |
Class at
Publication: |
607/28 ; 607/9;
607/37 |
International
Class: |
A61N 1/362 20060101
A61N001/362 |
Claims
1. A system for therapeutically stimulating a His bundle of a
patient's heart, the system comprising: an implantable pulse
generator configured for subcutaneous implantation in the patient
and to generate an electrical pacing stimulus; and a multi-polar
medical electrical lead operatively coupled to the pulse generator
for delivering the pacing stimulus to cardiac tissue proximate the
His bundle, the lead comprising: a proximal connector assembly
configured to mechanically and electrically couple the lead to the
pulse generator; a flexible tubular body dimensioned to extend at
least partially intravascularly from the implantation site of the
pulse generator through a superior vena cava of the patient to a
location proximate the His bundle, the body including a proximal
end coupled to the proximal connector, a distal end opposite the
proximal end and a longitudinal conductor lumen extending from the
proximal end of the body to the distal end of the body; a distal
tip assembly fixedly coupled to the distal end of the body, the tip
assembly comprising: a first electrode spaced from the distal end
of the body; a fixation helix fixedly coupled to the body and
extending distally of the first electrode, the fixation helix
configured as a second electrode electrically isolated from the
first electrode, the fixation helix further dimensioned to extend
from a wall of a right atrial septum of the patient to a location
proximate the His bundle and including a sharpened distal tip; and
a shank portion extending proximally of the first electrode and the
fixation helix within the conductor lumen of the body, the shank
portion including a proximal face having a receptacle for receiving
and engaging a stylet tip; a first coil conductor extending
longitudinally through the conductor lumen of the body and
electrically and mechanically coupled to the first electrode; and a
second coil conductor extending longitudinally through the
conductor lumen of the body and electrically and mechanically
coupled to the fixation helix, wherein one or both of the first and
second coil conductors defines a stylet lumen.
2. The system of claim 1, wherein the distal tip assembly further
includes a blunt distal tip, wherein the fixation helix extends
distally of the blunt distal tip, and wherein the first electrode
is located on the blunt distal tip of the distal tip assembly.
3. The system of claim 1, wherein the distal tip assembly includes
a tapered distal tip, wherein the fixation helix extends distally
of the tapered distal tip, and wherein the first electrode is
located on the tapered distal tip.
4. The system of claim 1, wherein an insulating material is
disposed between the first electrode and the fixation helix to
electrically isolate the first electrode and the fixation
helix.
5. The system of claim 4, wherein the insulating material is a
masking layer on a portion of the fixation helix proximate the
first electrode.
6. The system of claim 1, wherein the first electrode has a helical
shape and extends longitudinally adjacent a portion of the fixation
helix, and wherein the first electrode terminates proximal to the
distal tip of the fixation helix and includes a sharpened distal
end.
7. The system of claim 1, wherein the fixation helix includes an
electrically insulating masking material along a portion of the
fixation helix adjacent to the second electrode, wherein the
masking material terminates proximal to the distal tip of the
fixation helix.
8. The system of claim 1, wherein the first and second coil
conductors are co-axially disposed, and wherein the first conductor
is disposed about the second conductor.
9. The system of claim 1, wherein the first and second electrodes
are co-radially disposed.
10. The system of claim 1, wherein the receptacle in the face of
the shank portion is in the shape of a linear slot configured to
receive and engage a bladed stylet tip.
11. The system of claim 1, wherein a torque transfer ratio of the
body and the fixation helix is about 1:1.
12. The system of claim 1, wherein the lead further comprises:
longitudinally spaced third and fourth electrodes coupled to the
lead body proximal to the distal tip assembly; and third and fourth
conductors mechanically and electrically coupled to the third and
fourth electrodes.
13. The system of claim 12, wherein the lead body includes a second
conductor lumen and a third conductor lumen, wherein the third and
fourth conductors are cable conductors disposed, respectively,
within the second and third conductor lumens.
14. The system of claim 12, wherein the first, second, third, and
fourth conductors are arranged as individual filars in a single,
quad-filar coil, and wherein each of the individual filars is
electrically insulated from each of the other filars.
15. The system of claim 1, wherein the pulse generator is
configured to selectively transmit an electrical stimulus to the
first electrode or the second electrode.
16. The system of claim 1, wherein the first electrode is a
conductor needle extending longitudinally within a portion of the
fixation helix, wherein the conductor needle is longitudinally
extendable and retractable relative to the fixation helix.
17. A system comprising: a pulse generator configured to generate
an electrical pacing stimulus; a separable, splittable or slittable
guide catheter configured to deliver electrical stimulation to a
His bundle of a patient's heart, the catheter comprising: a
proximal shaft having a proximal end; a pre-curved distal portion
extending distally from the proximal shaft and terminating in a
distal tip, the distal portion including a series of contiguous
pre-formed curved segments, each having a different radius of
curvature and extending along a different arc length than each
immediately adjacent segment, the distal portion being configured
to locate the distal tip proximate an atrial wall of the heart
adjacent the His bundle when the proximal shaft portion is at least
partially located in a superior vena cava of the heart; an open
lumen extending longitudinally from the proximal end of the
proximal shaft to the distal tip of the pre-curved distal portion;
at least one electrode proximate the distal tip; and an
electrically conductive member extending from at least the proximal
end of the proximal shaft to the electrode for electrically
coupling the electrode to an external device for mapping electrical
activity of the heart; an implantable medical electrical lead sized
to be slidably received within the open lumen of the catheter, the
lead comprising: a proximal connector assembly configured to
mechanically and electrically couple the lead to the pulse
generator; a flexible tubular body dimensioned to extend at least
partially intravascularly from the pulse generator through the
patient's superior vena cava to a location proximate the His
bundle, the body including a proximal end coupled to the proximal
connector, a distal end opposite the proximal end, and a
longitudinal conductor lumen extending from the proximal end of the
body to the distal end of the body; a distal tip assembly fixedly
coupled to the distal end of the body, the tip assembly comprising:
a first electrode positioned adjacent to the distal end of the
body; a fixation helix fixedly coupled to the body and extending
distally of the first electrode, the fixation helix operable as a
second electrode electrically isolated from the first electrode,
the fixation helix further dimensioned to extend from a wall of a
right atrial septum to a location proximate the His bundle; and a
shank portion extending proximally of the first electrode and the
fixation helix within the conductor lumen, the shank portion
including a proximal face having a receptacle for receiving and
engaging a stylet tip; a first coil conductor extending
longitudinally through the conductor lumen and electrically and
mechanically coupled to the first electrode; and a second coil
conductor extending longitudinally through the conductor lumen and
electrically and mechanically coupled to the fixation helix,
wherein one or both of the first and second conductors defines a
stylet lumen; and a stylet having a proximal end and a distal end
including an engaging feature configured to mate with and engage
the receptacle on the shank portion of the distal tip assembly, the
stylet being configured to transmit a torque applied at its
proximal end to the distal tip assembly to cause rotation of the
fixation helix and the body.
18. The system of claim 17, wherein the distal tip assembly further
includes a blunt distal tip, wherein the fixation helix extends
distally of the blunt distal tip, and wherein the first electrode
is located on the blunt distal tip of the distal tip assembly.
19. The system of claim 17, wherein the distal tip assembly
includes a tapered distal tip, wherein the fixation helix extends
distally of the tapered distal tip, and wherein the first electrode
is located on the tapered distal tip.
20. The system of claim 17, wherein an insulating material is
disposed between the first electrode and the fixation helix to
electrically isolate the first electrode and the fixation
helix.
21. The system of claim 17, wherein the first electrode has a
helical shape and extends longitudinally adjacent a portion of the
fixation helix, the first electrode terminating proximal to the
distal tip of the fixation helix and including a sharpened distal
end.
22. The system of claim 17, wherein the first and second electrodes
are co-radially disposed.
23. The system of claim 17, wherein a torque transfer ratio of the
body and the fixation helix is about 1:1.
24. The system of claim 17, wherein the first electrode is a
conductor needle extending longitudinally within a portion of the
fixation helix, wherein the conductor needle is longitudinally
extendable and retractable relative to the fixation helix.
25. A method of implanting a lead for stimulating a His bundle in a
patient's heart, the method comprising: introducing the lead in the
right atrium of the patient's heart proximate to the apex of the
triangle of Koch; mapping the His bundle with at least a helix of
the lead; engaging a shank portion of the lead with a bladed stylet
to fixate the helix into cardiac tissue of the patient's heart; and
monitoring a His capture threshold and a ventricular capture
threshold of the His bundle obtained by the helix while torquing
the helix into the cardiac tissue.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to U.S. Provisional Application No. 61/045,168, filed on Apr. 15,
2008, entitled "Bundle of HIS Stimulation System," which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to medical electrical leads
for use in cardiac rhythm management systems. In particular, the
present invention relates to medical electrical leads configured
for mapping and pacing the bundle of His in a heart of a
patient.
BACKGROUND
[0003] Cardiac rhythm management systems are useful for
electrically stimulating a patient's heart to treat various cardiac
arrhythmias. A proposed method of electrically stimulating the
heart includes stimulating the His bundle located proximate to the
apex of the triangle of Koch in the right atrium of the heart. By
directly stimulating the bundle of His, both the right and left
ventricles can be physiologically activated, potentially avoiding
pacing induced dyssynchrony present with right ventricular apex
pacing. There is a continuing need for improved His bundle lead
designs and assemblies.
SUMMARY
[0004] In a first aspect, the present invention is a system for
therapeutically stimulating a His bundle of a patient's heart
including an implantable pulse generator and a multi-polar medical
electrical lead. The implantable pulse generator is configured for
subcutaneous implantation in the patient and to generate an
electrical pacing stimulus. The lead is operatively coupled to the
pulse generator to deliver the pacing stimulus to cardiac tissue
proximate the His bundle and includes a proximal connector
assembly, a flexible tubular body, a distal tip assembly and first
and second coil conductors. The proximal connector assembly is
configured to mechanically and electrically couple the lead to the
pulse generator. The body is dimensioned to extend at least
partially intravascularly from the pulse generator to a location
proximate the His bundle. The body includes a proximal end coupled
to the proximal connector, a distal end opposite the proximal end
and a longitudinal conductor lumen extending from the proximal end
of the body to the distal end of the body. The distal tip assembly
is fixedly coupled to the distal end of the body and includes a
first electrode spaced from the distal end of the body, a fixation
helix, and a shank portion. The fixation helix is fixedly coupled
to the lead body and extends distally of the first electrode. The
fixation helix has a sharpened distal tip and is operable as a
second electrode electrically isolated from the first electrode and
is dimensioned to extend to a location proximate the His bundle.
The shank portion extends proximally of the first electrode and the
fixation helix within the conductor lumen and includes a proximal
face having a receptacle for receiving and engaging a stylet tip.
The first and second coil conductors extend longitudinally through
the conductor lumen and are electrically and mechanically coupled
to the first electrode and the fixation helix, respectively. Either
one or both of the first and second coil conductors defines a
stylet lumen.
[0005] In a second aspect, the present invention is a system
including a pulse generator configured to generate an electrical
pacing stimulus, a separable, splittable or slittable guide
catheter configured to deliver electrical stimulation to a His
bundle of a patient's heart, and an implantable medical electrical
lead sized to be slidably received within an open lumen of the
catheter. The catheter includes a proximal shaft having a proximal
end, a pre-curved distal portion extending distally from the
proximal shaft and terminating in a distal tip, an open lumen
extending longitudinally from the proximal end of the shaft portion
to the distal tip, at least one electrode proximate the distal tip,
and an electrically conductive member extending from at least the
proximal end of the shaft portion to the electrode. The pre-curved
distal portion includes a series of contiguous pre-formed curved
segments, each having a different radius of curvature and extending
along a different arc length than each immediately adjacent
segment. The distal portion is configured to locate the distal tip
proximate an atrial wall of the heart adjacent the His bundle when
the proximal shaft portion is at least partially located in a
superior vena cava of the heart. The electrically conductive member
electrically couples the electrode to an external device for
mapping electrical activity of the heart. The implantable medical
electrical lead includes a proximal connector assembly configured
to mechanically and electrically couple the lead to the pulse
generator, a flexible tubular body, a distal tip assembly, first
and second coil conductors and a stylet. The flexible tubular body
is dimensioned to extend at least partially intravascularly from
the pulse generator through the patient's superior vena cava to a
location proximate the His bundle. The body includes a proximal end
coupled to the proximal connector, a distal end opposite the
proximal end, and a longitudinal conductor lumen extending from the
proximal end of the body to the distal end of the body. The distal
tip assembly is fixedly coupled to the distal end of the body and
includes a first electrode positioned adjacent to the distal end of
the body, a fixation helix fixedly coupled to the body and
extending distally of the first electrode, and a shank portion
extending proximally of the first electrode and the fixation helix
within the conductor lumen. The fixation helix is operable as a
second electrode electrically isolated from the first electrode and
is further dimensioned to extend from a wall of a right atrial
septum to a location proximate the His bundle. The shank portion
includes a proximal face having a receptacle for receiving and
engaging a stylet tip. The first and second coil conductors extend
longitudinally through the conductor lumen and are electrically and
mechanically coupled to the first electrode and the fixation helix,
respectively. Either one or both of the first and second coil
conductors defines a stylet lumen. The stylet has a proximal end
and a distal end including an engaging feature configured to mate
with and engage the receptacle on the shank portion of the lead
distal tip assembly. The stylet is configured to transmit a torque
applied at its proximal end to the distal tip assembly to cause
rotation of the fixation helix and the lead body.
[0006] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention.
Accordingly, the drawings and detailed description are to be
regarded as illustrative in nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic view of a His bundle stimulation and
pacing system including a pulse generator and a lead implanted in a
patient's heart according to an embodiment of the present
invention.
[0008] FIG. 2A is a plan view of a lead of the His bundle
stimulation and pacing system of FIG. 1 according to an embodiment
of the present invention.
[0009] FIG. 2B is a cross-sectional view of the lead of FIG. 2A
according to an embodiment of the present invention.
[0010] FIG. 3 is a side view of a distal tip assembly of the lead
of FIGS. 2A and 2B according to an embodiment of the present
invention.
[0011] FIG. 4 is a perspective view of a bullet-nose distal tip
assembly of the His bundle stimulation and pacing system of FIG. 1
according to an embodiment of the present invention.
[0012] FIG. 5 is an enlarged view of a double helix of a distal tip
assembly of the His bundle stimulation and pacing system of FIG. 1
according to an embodiment of the present invention.
[0013] FIG. 6 is an enlarged view of a helix with an electrode of a
distal tip assembly of the His bundle stimulation and pacing system
of FIG. 1 according to an embodiment of the present invention.
[0014] FIG. 7 is a schematic view of a delivery catheter of the His
bundle stimulation and pacing system of FIG. 1 according to an
embodiment of the present invention.
[0015] While the invention is amenable to various modifications and
alternative forms, specific embodiments have been shown by way of
example in the drawings and are described in detail below. The
intention, however, is not to limit the invention to the particular
embodiments described. On the contrary, the invention is intended
to cover all modifications, equivalents, and alternatives failing
within the scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION
[0016] FIG. 1 is a schematic view of a His bundle mapping and
pacing system 10 ("His bundle system 10") according to an
embodiment of the present invention. As shown in FIG. 1, the His
bundle system 10 includes an implantable pulse generator 12 coupled
to a His bundle lead 14 deployed in a patient's heart 16. The pulse
generator 12 generates an electrical pacing stimulus to be
delivered to the heart 16. The lead 14 operates to convey
electrical signals and stimuli between the heart 16 and the pulse
generator 12. As further shown in FIG. 1, the heart 16 includes a
right atrium and a right ventricle separated by a tricuspid valve.
During normal operation of the heart 16, deoxygenated blood is fed
into the right atrium through the superior vena cava 18 and the
inferior vena cava. The major veins supplying blood to the superior
vena cava 18 include the right and left axillary veins, which flow
into the right and left subclavian veins. The right and left
external jugular veins of the heart, along with the right and left
internal jugular veins of the heart, join the right and left
subclavian veins to form the right and left brachiocephalic veins,
which in turn combine to flow into the superior vena cava.
[0017] As shown, the lead 14 enters the vascular system through a
vascular entry site 20 formed in the wall of the left subclavian
vein, extends through the left brachiocephalic vein and the
superior vena cava 18, and is implanted in the right atrium. In
other embodiments of the present invention, the lead 14 may enter
the vascular system through the right subclavian vein, the left
axillary vein, the left external jugular, the left internal
jugular, or the left brachiocephalic vein. In still other
embodiments, other suitable vascular access sites may be utilized.
In short, any suitable venous path may be utilized for delivering
the lead 14 to the desired implantation site.
[0018] In the illustrated embodiment, the lead 14 is implanted in
the right atrium proximate to the apex of the triangle of Koch. The
His bundle system 10 allows direct therapeutic stimulation of the
His bundle by fixating a lead proximate to the apex of the triangle
of Koch. Once the His bundle has been located through one of
various mapping techniques, the His bundle is directly stimulated
through the right atrium of the heart. Although the His bundle
system 10 is described as stimulating and pacing the His bundle,
the His bundle system 10 may also be used in other applications,
such as right ventricular septal placement, without departing from
the intended scope of the present invention.
[0019] The lead 14 facilitates obtaining selective His bundle
pacing (SHBP) where His capture thresholds are low and ventricular
capture thresholds are high. In the case of SHBP, the His potential
recorded by the lead 14 should be near field and high amplitude.
Alternatively, the lead 14 can also be used for Parahisian pacing
(PHP), where His capture thresholds are high and ventricular
capture thresholds are low. With PHP, the His potential recorded by
the lead 14 should be far field and low in amplitude.
[0020] In the illustrated embodiment, a second right atrial lead 22
is situated in the right atrium, as is known for conventional
cardiac rhythm management systems. In another embodiment, the His
bundle system 10 is a three lead system having a right ventricular
lead (not shown) in addition to the His bundle lead 14 and the
right atrial lead 22. While the His bundle lead 14 stimulates the
His bundle, if His capture is not maintained or is unreliable,
suitable ventricular capture could also be maintained by the right
ventricular lead. If the His bundle lead 14 is faulty, the right
ventricular lead acts as a back up to the His bundle lead 14. For
example, the His bundle system 10 could be configured such that the
back up right ventricular lead would pace if it sensed a lack of
contraction, otherwise it would lay dormant. The His bundle system
10 may also include additional leads depending on the particular
therapeutic needs of the patient. For example, in various
embodiments, the His bundle system 10 includes a lead extending
into a coronary vein for stimulating the left ventricle in a
bi-ventricular pacing or cardiac resynchronization therapy system.
Alternatively or additionally, one or more
cardioversion/defibrillation leads (not shown) can also be included
in the His bundle system 10, in which case the pulse generator 12
will include defibrillation capabilities.
[0021] FIGS. 2A and 2B are isometric and partial cross-sectional
views, respectively, of the lead 14 of the His bundle system 10
according to one embodiment of the present invention. As shown, the
lead 14 is a multi-polar medical electrical lead and includes a
lead body 24, a stylet lumen 26, a first coil conductor 28 and a
second coil conductor 30. The lead body 24 is a flexible tubular
body including a proximal end 32 and a distal end 34, and defines a
conductor lumen 36 extending between the proximal and distal ends
32, 34. The coil conductors 28, 30 extend longitudinally within the
conductor lumen 36. In the illustrated embodiment, the coil
conductors 28, 30 are arranged coaxially, with the conductors 28,
30 defining the stylet lumen 26.
[0022] As shown, the lead 14 further includes a fixation helix 38
extending distally from the distal end 34 of the lead body 24, and
a proximal electrode 40 located at the distal end 34 of the lead
body 24 and spaced from the fixation helix 38. Additionally, the
proximal end 32 of the lead body 24 is connected to a proximal
connector assembly 42 configured to mechanically and electrically
couple the lead 14 to the pulse generator 12 (shown in FIG. 1). As
shown, the coil conductors 28, 30 are coupled to the proximal
electrode 40 and the fixation helix 38, respectively. As will be
appreciated, the coil electrodes 38, 40 are also electrically
coupled to individual electrical contacts in the connector assembly
42.
[0023] The fixation helix 38 is a fixed helix having a sharpened
tip portion 44 and is electrically active to function as the
cathode electrode. In one embodiment, the tip portion 44 of the
fixation helix 38 is flat ground to enable better penetration
through the fibrous His bundle and is sufficiently long to
penetrate through the central fibrous body of the heart 16 and
contact the His bundle. In an exemplary embodiment, the fixation
helix 38 is about 2.5 mm long (measured from the lead body 24 to
the tip of the fixation helix 38 along the general axis of the lead
14). In various embodiments, the lead body 24 is configured to have
sufficient torsional stiffness to allow as much direct torque
transfer as possible to allow penetration of the relatively tough
central fibrous body proximate the His bundle with the fixation
helix 38. The application of torque typically occurs by the user at
the proximal connector assembly 42 or at the lead body 24 proximate
the proximal connector assembly 42. In an exemplary embodiment, the
lead 14 has as close to infinite torsional stiffness as possible
and a torque transfer of about 1:1 such that one turn of the
proximal connector assembly 42 or lead body 24 is transferred to
the fixation helix 38 with no to minimal attenuation, even when
penetrating the fixation helix 38 into a tough structure, such as
fibrous tissue. An approximate 1:1 torque transfer ratio enables
precise control over the fixation process into the fibrous tissue,
enabling the physician to stop when the His potential is
maximized.
[0024] The fixation helix 38 is optionally coated with a
polymer-drug, such as an anti-inflammatory agent, that is durable
and able to withstand fixation of the fixation helix 38. In one
embodiment, the fixation helix 38 includes a durable
steroid-polymer matrix capable of withstanding positioning and
repositioning in the fibrous bundle. In addition, the
steroid-polymer matrix also reduces inflammation associated with
the fixation process and promotes high pacing thresholds. Examples
of suitable steroid-polymer matrices include, but are not limited
to: paclitaxel, clobetasol and dexamethasone.
[0025] The stylet lumen 26 enables the use of a stiffening stylet
wire 46 to deliver the lead 14 to the desired location. If the lead
14 dislodges from the heart 16, the stylet lumen 26 also allows the
lead 14 to be repositioned without having to remove the lead 14,
reaccess the vein, and place a new catheter. In one embodiment, the
stylet lumen 26 may be configured to receive a locking stylet which
allows the lead 14 to be more easily extracted if needed. In an
alternative embodiment, the stylet lumen 26 may be sized to
accommodate a torque tube design, rather than a traditional stylet
wire. While the lead 14 is discussed as including a stylet lumen
26, in an alternative embodiment, the lead 14 may be a lumenless
lead without departing from the intended scope of the present
invention.
[0026] In one embodiment, the lead 14 is fixated in the heart 16 by
rotating the lead body 24 to screw the helix 38 into the heart
tissue. When implanted, the tip portion 44 of the fixation helix 38
extends from a wall of the right atrial septum to the His bundle.
Because the lead 14 includes a fixed helix 38, the lead body 24 is
configured to provide efficient torque transfer from the proximal
end 32 of the lead body 24 to the fixation helix 38, so as to
penetrate through the central fibrous body at the triangle of Koch.
In order to fixate the fixed helix 38 at the bundle of His, the
lead body 24 is turned such that torque is transferred down the
lead body 24, resulting in rotation of the fixed fixation helix 38
of the lead 14. In one embodiment, the lead body 24 is sufficiently
lubricious to facilitate the passage of the lead 14 and torque
transfer to the lead body 24. In an exemplary embodiment, the lead
body 24 is formed of polyurethane to enable torque transfer and
also to provide the desired lubricity. In another embodiment, the
lead body 24 is formed of silicone which may or may not include a
lubricious coating or treatment to increase lubricity and also may
be reinforced to enhance torque transfer. Although the fixation
helix 38 is discussed as being a fixed helix, in an alternative
embodiment, the fixation helix 38 is an extendable-retractable
helix.
[0027] Alternatively, the lead body 24 and fixation helix 38 can be
rotated with a bladed stylet configured to engage a feature at the
distal end 34 of the lead 14 (shown in FIG. 3 below). In another
embodiment, a stylet can be keyed to a terminal pin to separately
facilitate torque transfer. In one embodiment, a torque tube having
a keyed end could be used to mate with a receptacle in the lead
tip.
[0028] In the illustrated embodiment, the lead 14 of the His bundle
system 10 includes dual coil conductors arranged coaxially within
the lead body 24. In other embodiments, other conductor
configurations may be employed. For example, a bipolar lead may
include a co-radial design, or alternatively, may have dual cables,
one on either side of a center lumen. The center lumen is only used
for stylet passage and either a dummy coil or a polymer sheath is
used for stylet puncture protection. In another embodiment, the
lead is a multi-polar lead including longitudinally spaced third
and fourth electrodes coupled proximal to the distal end of the
lead. The third and fourth electrodes are mechanically and
electrically coupled to third and fourth conductors. In this
embodiment, the third and fourth conductors may be positioned
within a second conductor lumen of the lead. The lead may also
include a third conductor lumen such that the third conductor is
positioned within the second conductor lumen and the fourth
conductor is positioned within the third conductor lumen. The
multi-polar lead may also include a co-radial coil flanked by two
cables or two cables running in one lumen; a quad-filar co-radial
design; a trifilar co-radial inner coil; an outer flat wire coil
that provides torque transfer and enables a size reduction over a
round wire; and a design with four cables flanking a center lumen.
Examples of co-radial designs are further described in co-pending
U.S. Patent Publication No. 20060293737 entitled "Multiple
Electrode Implantable Lead", which is hereby incorporated by
reference. Still other lead body and conductor configurations will
become apparent to those of skill in the art.
[0029] FIG. 3 is a side view of a distal tip assembly 48 configured
to be incorporated into the His bundle lead 14. As shown in FIG. 3,
the distal tip assembly 48 includes the fixation helix 38, the
proximal electrode 40 and a shank portion 50 and is configured to
be coupled to the distal end 34 of the lead body 24, with the shank
portion 50 received by the conductor lumen 36 of the lead body 24.
The proximal electrode 40 is spaced from the distal end 34 of the
lead body 24 and the fixation helix 38 extends distally of the
proximal electrode 40. As discussed above, the fixation helix 38
can function as a second electrode that is electrically isolated
from the proximal electrode 40. To isolate the first and second
electrodes 38, 40, an insulating material 52 may be disposed
between the electrodes 38, 40. In an exemplary embodiment, the
insulating material 52 is a masking layer applied proximate the
proximal electrode 40. The proximal electrode 40 is electrically
and mechanically connected to the first coil conductor 28 (shown in
FIG. 2B) and the fixation helix 38 is electrically and mechanically
connected to the second coil conductor 30 (shown in FIG. 2B).
[0030] The shank portion 50 of the distal tip assembly 48 extends
within the conductor lumen 36 of the lead body 24 proximally of the
proximal electrode 40 and the fixation helix 38. The shank portion
50 includes a proximal face 54 having a recess 56 for receiving and
engaging the tip of a bladed stylet, such as the stiffening stylet
wire 46. The stiffening stylet wire 46 includes a shaft 58 having a
proximal end 60 and a distal end 62. The proximal end 60 includes a
handle 64 and the distal end 62 includes an engagement member 66
that is configured to mate with and engage the recess 56 of the
shank portion 50 of the distal tip assembly 48. The stiffening
stylet wire 46 is configured to transmit a torque applied at the
handle 64 to the distal tip assembly 48 to rotate the lead body 24
and the fixation helix 38. Precise application of torque through
the lead body 24 into the heart 16 occurs by engaging the
engagement member 66 of the stiffening stylet wire 46 with the
recess 56 and rotating the stiffening stylet wire 46. In an
exemplary embodiment, the recess 56 has a linear slot
configuration.
[0031] As shown, the distal tip assembly 48 includes a blunt tip 70
to prevent over-extension or penetration into the heart tissue when
the lead 14 is being implanted. The proximal electrode 40 is
located on the blunt tip 70 and the fixation helix 38 extends
distally of the blunt tip 70.
[0032] Although the entire fixation helix 38 has been discussed as
being electrically active, in an alternative embodiment, only the
tip portion 44 of the fixation helix 38 is active and the rest of
the fixation helix 38 is coated with an insulator to prevent
ventricular capture. With this configuration, the lead 14 can be
fixated until a near field His bundle signal is obtained. In this
embodiment, because only the tip portion 44 of the fixation helix
38 is electrically active, only low output His capture is obtained.
As the fixation helix 38 is advanced into the cardiac tissue during
fixation, the His potential may be mapped and the lead 14 can be
continually repositioned until His capture is obtained. Once a near
field His signal is recorded, further advancement of the fixation
helix 38 into the tissue can be discontinued. Any suitable,
biocompatible electrical insulative material (i.e. parylene) can be
used as the insulating material.
[0033] In one embodiment, the shaft 58 of the stiffening stylet
wire 46 is configured to radially expand when torque is applied to
the stiffening stylet wire 46. Upon expansion, the shaft 58 is
configured to frictionally engage an inner wall of the stylet lumen
26 and to transfer torque to the stylet lumen 26. In yet another
embodiment, the stiffening stylet wire 46 includes a torque tube in
which there are two overlapping helical coils--an inner coil and an
outer coil. When rotated, the inner coil expands against the outer
coil and creates a torque transfer system in a flexible shaft. When
counter-rotated, the inner coil radially contracts and axially
compresses to a solid stacked height to provide torque transfer in
a flexible shaft. In yet another embodiment, the stylet lumen 26
may be a ribbon wire and/or the coil of the lead 14 may be a ribbon
wire. The ribbon wire shape provides more efficient torque transfer
than conventional circular systems.
[0034] FIG. 4 is a side view of a bullet-nose distal tip assembly
100 for inclusion in a lead 102 configured for use with the His
bundle system 10 according to another embodiment of the present
invention. The distal tip assembly 100 includes a helix 104, a
proximal electrode 106 and a shank portion 108. The lead 102
includes a lead body 110 having a distal end 112 and a proximal end
114 (not shown) with a conductor lumen 116 extending between the
distal end 112 and the proximal end 114. The shank portion 108 of
the distal tip assembly 100 is configured to be coupled to the
distal end 112 of a lead body 110 with the shank portion 108
received by the conductor lumen 116 of the lead body 110. The
proximal electrode 106 is spaced from the distal end 112 of the
lead body 110 and the helix 104 extends distally of the proximal
electrode 106. The bullet-nose distal tip assembly 100 is
substantially the same as the blunt tip distal tip assembly 48
(shown in FIG. 3) except that the distal end 112 of the lead 102 is
bullet-nosed rather than blunt tipped. When the transition area
between the lead body 110 and the helix 104 is bullet shaped, the
helix 104 can function as the cathode and a tapered tip 118 of the
distal end 112 formed by the bullet-nose can function as the anode.
In one embodiment, the bullet-nosed tip is electrically active to
form the proximal electrode 106. The coil conductors are coupled to
the helix 104 and the proximal electrode 106, for example, by
welding or crimping. With this configuration, if SHBP cannot be
obtained, the tapered tip 118 can be switched to be the cathode,
enabling ventricular pacing. The bullet-nose design illustrated in
FIG. 4 enables deeper penetration of the distal end 112 into the
heart tissue. This configuration may be particularly applicable
with a double wire helix with programmable polarity to either
enable a very discrete His potential or to enable electronic
repositioning to find a better His potential without having to
actually reposition the lead 102. For a double wire helix, the two
wires are insulated through a fitting before connecting the wires
to the coil conductor.
[0035] FIG. 5 is an enlarged view of a double wire, bipolar
fixation helix assembly 200 for use in a lead 202 configured to be
incorporated into the His bundle system 10 according to another
embodiment of the present invention. In this embodiment, the
fixation helix assembly 200 includes a distal wire 204 and a
proximal wire 206 close wound together. In an exemplary embodiment,
the distal wire 204 and the proximal wire 206 are fixedly coupled
together. The distal wire 204 operates as a distal electrode for
His bundle pacing, while the proximal wire 206 operates as a
proximal electrode for ventricular pacing. However, if the His
bundle cannot be found and the lead 202 must be repositioned, the
distal wire 204 and the proximal wire 206 can temporarily switch
functions. The distal wire 204 includes a sharpened tip 208 for
easy and atraumatic tissue penetration of the heart. The proximal
wire 206 is spaced from the distal tip 208 of the distal wire 204
but still includes a sharpened distal tip 208 to allow for further
penetration of the lead 202. In this configuration, the cathode and
the anode are both in the distal wire 204. The distal wire 204 and
the proximal wire 206 are conductors and are optionally selectively
coated with an insulator to give separate conductor paths. Although
FIG. 5 depicts the conductors 204 and 206 as being close wound for
part of their length, both conductors 204 and 206 may optionally
not be close-wound for part of their length.
[0036] FIG. 6 is a schematic view of an alternative helix/electrode
assembly 300 for a His bundle pacing lead, such as the lead 14,
having a helix 302 and an electrode 304, whereby the helix 302 is a
fixed helix 302 and the electrode 304 is an extendable-retractable
conductor needle. The helix 302 and the needle 304 of the assembly
300 have different conduction paths. The helix 302 functions
similarly to the fixation helix 38 described in FIG. 2 and fixates
the lead 306 to the heart 16 (shown in FIG. 1), providing anchoring
stability to the lead 306. The needle 304 is operable to map the
His bundle potential and is longitudinally extendable past the
helix 302. Because the needle 304 is positioned within the helix
302, the needle 304 has an outer diameter sufficiently smaller than
the inner diameter of the helix 302 to permit the needle 304 to
translate longitudinally through the helix 302. The
extendable-retractable needle 304 drives through the helix 302 upon
rotating the terminal pin (shown in FIG. 2A) to provide accurate
placement of the electrode/needle 304 near the His bundle (shown in
FIG. 1). The needle 304 is pushed into the central fibrous body
until it reaches the His bundle. The helix 302 is then screwed into
the central fibrous body so as to anchor the lead 306 to the heart
16. Although FIG. 6 depicts the needle 304 as having a
substantially tubular body and an angled tip, the needle 304 can
have any variety of shapes for penetrating into the cardiac central
fibrous body.
[0037] FIG. 7 is a schematic view of a lead delivery catheter 72
configured for locating the His bundle and delivering the His
bundle pacing lead 14 to the desired implantation location. In the
illustrated embodiment, the delivery catheter 72 is a fixed shape
catheter having a preformed shape to enable orientation of the
delivery catheter 72 proximate the coronary sinus at the apex of
the triangle of Koch. The delivery catheter 72 includes a proximal
shaft 74, a curved distal portion 76 having a distal end 78, an
open lumen 80, an electrode 82 located at the distal end 78, and an
electrically conductive member 84 extending within the catheter
wall. The curved distal portion 76 includes a plurality of curved
segments 86 and extends distally from the proximal shaft 74 and
terminates at the distal tip 78. Each of the curved segments 86 has
a radius of curvature and extends along an arc length. Generally,
the radius of curvature and arc length of adjacent segments 86 are
different from one another. The curved distal portion 76 is
configured such that the distal end 78 can be positioned proximate
an atrial wall of the heart 16 adjacent the bundle of His when the
proximal shaft 74 is positioned within the superior vena cava 18 of
the heart 16.
[0038] Because the apex of the triangle of Koch is proximate to the
coronary sinus, the delivery catheter 72 is, in various
embodiments, shaped in a manner similar to catheters configured for
accessing the coronary sinus for left ventricular lead delivery.
Embodiments of such catheters are described in co-pending and
commonly assigned U.S. patent application Ser. No. 10/916,353 filed
Aug. 11, 2004 and titled "Coronary Sinus Lead Delivery Catheter,"
which is incorporated herein by reference in its entirety. Of
course, in other embodiments, other catheter shapes may be employed
to locate the apex of the triangle of Koch and in turn, the His
bundle.
[0039] In one embodiment, the electrode 82 of the delivery catheter
72 is located proximate the distal end 78 and facilitates direct
His bundle mapping. The electrically conductive member 84 extends
from at least a proximal end 88 of the proximal shaft 74 to the
electrode 82 and electrically couples the electrode 82 to an
external device for mapping electrical activity of the heart 16.
Alternatively, the lead 14 could be used to map the His potential
if connected to a 12-lead ECG.
[0040] The open lumen 80 of the delivery catheter 72 extends
longitudinally from the proximal end 88 of the proximal shaft 74 to
the distal end 78 of the curved distal portion 76. In practice, the
lead 14 is passed through the lumen 80 of the delivery catheter 72
to the desired location. In one embodiment, the distal tip 78 of
the delivery catheter 72 is generally more stiff than catheters
used to deliver left ventricular leads so that once the distal end
78 of the delivery catheter 72 is oriented at the desired location,
the lead 14 will not deflect the distal end 78 of the delivery
catheter 72 away from the desired location as it is being passed
through the delivery catheter 72. The inner diameter of the
delivery catheter 72 in one embodiment includes a lubricious
surface to facilitate passing the lead 14 through the delivery
catheter 72 to allow rotation of the lead 14 to enable fixation of
the lead 14.
[0041] The delivery catheter 72 has a separable, splittable or
slittable configuration such that once the lead 14 has been
properly placed and fixated, the delivery catheter 72 can be easily
removed from the heart 16. For example, the delivery catheter 72
may have a peel-away configuration such that after the lead 14 has
been placed within the cardiac tissue of the heart 16, the delivery
catheter 72 can be easily split apart and removed from around the
lead body 24 as it is being pulled from the heart 16. In the case
that the delivery catheter 72 is braided, the delivery catheter 72
may have a cut-away configuration for use with a cutter. As the
delivery catheter 72 is pulled back from the lead body 24, the
cutter creates a slit through the delivery catheter 72 and allows
the delivery catheter 72 to be separated from the lead body 24.
[0042] In another embodiment, a dual catheter system is used to
place the lead 14 at the desired location. In a dual catheter
system, an outer shaped catheter is introduced into the heart 16
and an inner catheter is passed through the outer catheter. This
configuration allows a measure of deflectability and the inner
catheter may have another shape enabling additional positioning of
the lead 14 at the apex of the triangle of Koch. The lead 14 is
then passed through the inner catheter to map the His bundle
potential and to fixate in the heart.
[0043] In yet another embodiment, a deflectable catheter is used to
place the lead 14 at the His bundle. A deflectable catheter allows
the distal end 78 of the catheter to be manipulated when positioned
within the heart 16. To manipulate the distal end 78, the proximal
end 88 of the proximal shaft 74 includes a steering or deflection
mechanism, such as pull wires. The steering mechanism allows the
distal end 78 of the catheter to be maneuvered until properly
positioned at the bundle of His.
[0044] In an embodiment where the delivery catheter 72 does not
include electrodes, to properly orient the delivery catheter 72
within the heart 16, the His bundle may first be mapped via an EP
deflectable catheter to locate a high amplitude His potential. Once
the EP catheter has mapped the His bundle, the delivery catheter 72
is passed into the heart 16 and manipulated such that the distal
end 78 of the delivery catheter 72 touches, or is proximate to, the
tip of the EP deflectable catheter. The lead 14 is then passed
through the delivery catheter 72 with a support wire or a torque
transfer wire. When the distal end 34 (shown in FIG. 2) of the lead
14 is in place, the lead 14 is fixated by applying torque to the
lead body 24 and the stiffening stylet wire 46 while continuing to
map the His bundle. The handle 64 of the stiffening stylet wire 46
is rotated to control the deflection of the lead body 24. Fixation
is accomplished by turning the entire lead body 24 while continuing
to map in real-time. Application of torque continues until the
highest amplitude His potential is found. If the resulting location
of the distal end 34 of the lead 14 is accurately placed, the
stiffening stylet wire 46 is removed. The delivery catheter 72 is
then either cut or peeled away, depending on the configuration of
the delivery catheter 72. After the lead 14 is fixated, the
location of the lead 14 is optionally reassessed to ensure proper
fixation of the lead 14.
[0045] The His bundle mapping and stimulation system of the present
invention provides a time efficient system for locating and
directly stimulating the His bundle. The His bundle system includes
a lead that is introduced into the right atrium of the heart
through a delivery catheter. Before the lead is passed through the
delivery catheter, the location of the His bundle is mapped either
by an EP catheter or some other means. In order to facilitate
fixation into the bundle of His, which is formed of a central
fibrous body, a distal end of the lead is a fixed helix and a
proximal end of the lead includes a slot. To provide enough torque
to rotate the entire lead body, a tool having an end sized to
engage the slot is affixed to the proximal end of the lead and
together the tool and the lead body are rotated. As a result of the
rotation of the lead body, the fixed helix at the distal end of the
lead is implanted into the bundle of His.
[0046] Various modifications and additions can be made to the
exemplary embodiments discussed without departing from the scope of
the present invention. For example, while the embodiments described
above refer to particular features, the scope of this invention
also includes embodiments having different combinations of features
and embodiments that do not include all of the described features.
Accordingly, the scope of the present invention is intended to
embrace all such alternatives, modifications, and variations as
fall within the scope of the claims, together with all equivalents
thereof.
* * * * *