Multi-electrode lead with backing for mecho/baroreceptor stimulation

An electrode structure for an implantable stimulation lead for use in stimulating a target nerve structure within a patient includes a flexible backing defined by a major dimension extending in a direction of a first axis, and a minor dimension extending generally orthogonal to the first axis. The electrode structure also includes a plurality of electrodes coupled to the backing.

TECHNICAL FIELD

The disclosure relates to systems and methods for stimulating nerves. More particularly, the disclosure relates to systems and corresponding methods for stimulating the baroreceptors of the carotid sinus.

BACKGROUND

The use of nerve stimulation for treating and controlling a variety of medical, psychiatric, and neurological disorders has seen significant growth over the last several decades, including for treatment of heart conditions (e.g., hypertension), epilepsy, obesity, and breathing disorders, among others.

SUMMARY

Disclosed herein are various embodiments of electrode structures for neurostimulation leads.

In Example 1, an electrode structure for an implantable stimulation lead for use in stimulating a target nerve structure within a patient includes a flexible backing defined by a major dimension extending in a direction of a first axis, and a minor dimension extending generally orthogonal to the first axis. The electrode also includes a plurality of electrodes coupled to the backing.

In Example 2, the electrode structure according to Example 1, wherein the backing is adapted to be coupled to a distal end of an implantable lead in situ.

In Example 3, the electrode structure according to Example 1 or 2, wherein the backing is configured to resist suture tearing.

In Example 4, the electrode structure according to any of Examples 1-3, wherein at least a portion of the backing element includes an embedded mesh.

In Example 5, the electrode structure according to any of Examples 1-4, wherein at least a portion of a first surface of the backing element comprises one or more grooves adapted to hold at least a portion of a suture.

In Example 6, the electrode structure according to any of Examples 1-5, wherein the backing has a curved shape adapted to conform to a curvature of a blood vessel.

In Example 7, a neurostimulation lead includes a lead body having a proximal portion and a distal portion, a first conductor extending through the lead body and an electrode structure secured to the distal portion of the lead body. The electrode structure includes a backing defined by a major dimension generally in a direction of a longitudinal axis defined by the distal portion of the lead body and a minor dimension generally in a same plane and orthogonal to the longitudinal axis and a plurality of electrodes coupled to at least a portion of the backing.

In Example 8, the neurostimulation lead according to Example 7, wherein the backing is generally rectangular in shape.

In Example 9, the neurostimulation lead according to Example 7 or 8, wherein the backing has peripheral edges that are generally rounded.

In Example 10, the neurostimulation lead according to any of Examples 7-9, wherein the backing is generally oval-shaped.

In Example 11, the neurostimulation lead according to any of Examples 7-10, wherein the backing is curved about a central axis generally parallel to a longitudinal axis.

In Example 12, a neurostimulation system includes a pulse generator comprising a power source and a lead that includes a lead body having a proximal portion and a distal portion, the proximal portion of the lead secured to the pulse generator. The lead also includes a first conductor extending through the lead body and an electrode structure secured to the distal portion of the lead body. The electrode structure includes a backing defined by a major dimension generally in a direction of a longitudinal axis defined by the distal portion of the lead and a minor dimension generally in a same plane and orthogonal to the longitudinal axis, and a plurality of electrodes coupled to at least a portion of the backing.

In Example 13, the neurostimulation system according to Example 12, wherein the backing includes a flexible material that includes a mesh.

In Example 14, the neurostimulation system according to Example 12 or 13, wherein the mesh is disposed in an area proximate to an outer perimeter.

In Example 15, the neurostimulation system according to any of Examples 12-14, wherein the mesh is disposed uniformly over an entire portion of the backing.

In Example 16, the neurostimulation system according to any of Examples 12-15, wherein the mesh comprises polyester.

In Example 17, the neurostimulation system according to any of Examples 12-16, wherein the backing includes grooves or holes adapted to guide suture placement.

In Example 18, the neurostimulation system according to any of Examples 12-17, wherein the grooves or holes extend across at least a portion of the backing.

In Example 19, the neurostimulation system according to any of Examples 12-18, wherein the grooves or holes extend across one of a proximal portion, a distal portion of the backing or a combination thereof.

In Example 20, the neurostimulation system according to any of Examples 12-19, wherein the major dimension of the backing ranges from about 12 mm to about 16 mm.

DETAILED DESCRIPTION

FIG. 1is a schematic illustration showing a system2for stimulating a region of a patient's nervous system. In one embodiment, the system2can be particularly effective in stimulating the baroreceptors of the carotid sinus for treatment of heart conditions such as hypertension.

As shown, the system2includes a neurostimulation lead18and an implantable pulse generator22. As further shown, the neurostimulation lead18includes an electrode structure26and a lead body34. In various embodiments, and as explained in greater detail herein, the neurostimulation lead18and the electrode structure26cooperate to form a stimulation electrode assembly. In the illustrated embodiment, the neurostimulation lead18is coupled to the pulse generator22, which includes a power source or battery28. Additionally, the electrode structure26is disposed at an implantation location within the patient. In one embodiment, the implantation location is a location on or adjacent to the carotid sinus for selective stimulation of the carotid sinus baroreceptors.

As will be further explained herein, in various embodiments, the neurostimulation lead18and the electrode structure26can be provided as separate elements that are coupled together in situ during the implantation process. Alternatively, in various embodiments, the neurostimulation lead18and the electrode structure26can be a unitary element, with the neurostimulation lead18housing electrical conductors that are electrically connected to electrodes on the electrode structure26.

In various embodiments, the lead body34is elongate and flexible and is made of a biocompatible electrically insulative material, and includes a proximal end38coupled to the pulse generator22via a connector (not shown). In various embodiments, the lead body34is generally flexible to allow for patient movement. In some embodiments, the lead body34can include one or more guide lumens to receive a guide member such as a guidewire or stylet in order to stiffen the lead body34for surgical implantation.

According to various embodiments, the neurostimulation lead18can include a plurality of conductors (not shown) including individual wires, coils, or cables extending within the lead body34from the proximal end38in a direction to the electrode structure26. The conductors can be insulated with an insulator such as silicone, polyurethane, ethylene tetrafluoroethylene, or another biocompatible, insulative polymer. In one exemplary embodiment, the conductors have a co-radial design. In some embodiments, each individual conductor is separately insulated and then wound together in parallel to form a single coil. In another exemplary embodiment, the conductors have a co-axial, non-co-radial configuration. In various embodiments, the individual conductors may be single or multi-filar coil conductors. In still other embodiments, one or more of the conductors is a stranded cable conductor each routed through one of the aforementioned lumens in the lead body34. In short, the various embodiments are not limited to any particular conductor configuration within the neurostimulation lead18.

In various embodiments, the electrode structure26can have a number of suitable configurations that are able to effectively stimulate the target nerves such as the carotid sinus baroreceptors. In the embodiment illustrated inFIG. 1, after being implanted in the patient and assembled, the electrode structure26has a generally curved shape that can surround or encircle a portion or the entire implantation site. In the illustrated embodiment, the electrode structure26may be configured to be wrapped fully around the implantation site, but in alternative embodiments the electrode structure26can be configured to wrap around only a portion of the circumference of the implantation site.

FIGS. 2A-Care schematic front, side and rear views, respectively, of the electrode structure26according to various embodiments. As shown inFIG. 2A, the electrode structure includes a backing44and a pair of electrodes50,51. In some embodiments, the electrode structure26may include more than two electrodes50,51. As further shown, in various embodiments, the electrode structure26extends from or is integrally coupled to a distal end42of the lead body34(seeFIG. 1).

As shown inFIGS. 2A-C, the backing44has a first surface52, a second opposite surface54and sides56extending between the first surface52and the second surface54. The electrode structure26also has a distal portion45and a proximal portion46.

In various embodiments, the electrodes50,51are disposed onto the first surface52of the backing44and/or disposed within at least a portion of the backing44. In various embodiments, the electrodes50,51may be positioned flush against the first surface52of the backing44. In other embodiments, the electrodes50,51may protrude from the first surface52of the backing44. In some embodiments, the electrodes50,51may be recessed from the first surface52and into the backing44.

Each electrode50,51may be of any suitable dimension that is capable of delivering energy to a desired site to stimulate tissue. In some embodiments, the electrodes50,51can be a disc shape that includes a disc-like cap-and-stem form. For example, the head of each of the electrodes50,51may have a circular diameter ranging from between about 0.5 mm to 3 mm. A suitable diameter of the disc-shaped electrodes50,51may be 2 mm, for example. In other embodiments, the electrodes50,51can be helically shaped, a flexible ribbon, or cylindrical shaped. In other embodiments, the electrodes50,51may be spherically shaped (ball) tip mounted to a rod.

In various embodiments, the backing44of the electrode structure26can be formed from a flexible, electrically insulative material. Suitable polymers that may be used for the backing44can include, for example, silicone, polyurethane, polysiloxane urethane, ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE), and expanded ultra-high-molecular-weight polyethylene (eUHMWPE), polyisobutylene-based polyurethanes (PIB PU), although others are also contemplated.

Suitable materials for the electrodes50,51include conductive materials such as platinum, titanium, or a platinum-based alloy, for example, platinum-iridium. In some embodiments, the electrodes50,51may also include a coating disposed over the conductive material. Suitable coatings may include, for example, iridium, iridium oxide, platinum gray, titanium nitride, and platinum black.

In some embodiments, at least a portion of the exposed surfaces of the electrodes50,51may include features to increase the surface area of the electrodes50,51. Examples of features that increase the surface area include grooves, dimples, texturing or other similar features.

FIGS. 3A-Care schematic front views showing various exemplary configurations of the electrode structure26. As shown inFIGS. 2A-C, respectively, the electrode structure26can be generally rectangular-shaped, oval-shaped or circular. In some embodiments, the backing44of the electrode structure26may have a flat, rectangular shape or an oval shape defined by a thickness T, width W, and an overall length L1(seeFIGS. 2A-C). In other embodiments, the electrode structure26may have a different form, for example, a circular shape, as shown inFIG. 3C, defined by a diameter and the thickness. It may be contemplated by those skilled in the art that the backing44may have various other forms suitable for neurostimulation implantation. In various embodiments, the material forming the electrode structure26may have a uniform or non-uniform cross-sectional thickness.

FIG. 4shows an exemplary electrode structure26having a flat, oval shape defined by a width W and an overall length L1. Suitable dimensions of the electrode structure26may allow a physician to more easily suture, or otherwise couple, the electrode structure26to the carotid sinus. In some embodiments, the dimensions of the electrode structure26may include an overall length (L1) range of about 13 mm to 18 mm, a width range of about 8 mm to 10 mm, and a thickness range of about 0.01 mm to 1 mm. For example, the electrode structure26may have a length L1of 13 mm, a width W of 8 mm and a thickness T of 0.5 mm.

The overall length L1and width W of the electrode structure26may affect the area available on the electrode structure26that may be used for placing a suture. For example, an electrode structure26having a length L1of 13 mm and a width W of 8 mm would likely be sutured within about 3 mm or less from the outer perimeter of the electrode structure26. In other examples, an electrode structure26having a length of 15 mm and a width of 10 mm would likely be sutured within about 4 mm or less from the outer perimeter of the electrode structure26.

FIG. 5is a schematic view of the electrode structure26showing an interior65of the backing44adapted to couple to a pair of electrodes50,51to a pair of conductors (not shown). The interior65may also couple the pair of conductors to the distal end of the lead body42(not shown), in some embodiments. As shown, the interior65may include a pair of apertures58,59, a cavity62, and a pair of channels60,61connecting each aperture58,59to the cavity62.

As shown inFIGS. 4 and 5, the first surface52of the backing44may include the pair of apertures58,59adapted to couple with the electrodes50,51, according to some embodiments. In some embodiments, the aperture58may be sized to partially or fully receive an electrode50. For example, each aperture58,59may have a diameter D2, or be otherwise sized, to receive at least a portion of the electrode50, for example, a stem portion of an electrode50.

The electrodes50,51may be spaced a suitable distance apart from each other such that the sensing capability of each electrode50is unaffected by an adjacent electrode51. In some embodiments, the edge-to-edge spacing L2between the first electrode50to the second electrode51(seeFIG. 4), e.g. the electrode-to-electrode spacing, may range from about 1 mm to 5 mm. For example, a suitable electrode-to-electrode spacing L2may be 3 mm, in some embodiments.

The interior65of the backing44may also include multiple channels60,61adapted to allow cables (not shown), and/or coils, to be disposed within the backing44and to couple to the electrodes50,51according to some embodiments. In some embodiments, at least a portion of the interior65, for example, the pair of channels60,61, may be enclosed between the first and second surfaces52,54and the sides56(FIG. 2B) of the backing44. In other embodiments, at least a portion of the interior65connects to one or more exterior surfaces of the backing44, for example, the cavity62may connect to and form an opening at the sides56of the backing44.

The channels60,61may be spaced a suitable distance apart from each other such that the cables within the first and second channel60,61do not interfere with one another and may be coupled to the appropriate electrodes50,51. In some embodiments, the first channel60may be spaced apart from the second channel61by a distance of at least 0.25 mm. For example, in some embodiments, the first channel60may be spaced apart from the second channel61by a distance ranging between about 0.5 mm and 1 mm.

The interior65of the backing44may also include the cavity62adapted to receive conductors and/or the distal end of the lead body42, in various embodiments. The cavity62may be a generally tubular-shaped area adapted to receive conductors and/or at least a portion of tubing, such as a bi-lumen sheath, covering the lead conductors. As shown inFIG. 5, the cavity62allows a portion of the tubing covering the cables to be disposed within the backing44.

In some embodiments, adhesive may be dispensed within the cavity62to bond the cables and sheath to the backing44of the electrode structure26. Also, the cables and/or coils may be soldered, adhesively bonded, or joined by another commonly known bonding technique, to the electrodes50,51.

As shown inFIG. 6, at least a portion of the backing44may include a flexible material that includes an embedded mesh64, in some embodiments. For example, the backing44may comprise a silicone material including an embedded mesh64. In some embodiments, the mesh64may be disposed within a portion of the backing44, such as the area proximate the outer perimeter, as shown inFIG. 6. In other embodiments, the mesh64may be disposed uniformly over the entire portion of the backing44. Suitable materials for the embedded mesh64may include polyester or other commonly used materials in implantable products, in some embodiments. The mesh may minimize or aid in preventing the tearing of the backing when the backing is sutured onto an anatomical structure, such as a blood vessel.

In various embodiments, the embedded mesh64includes a fiber configuration that accommodates suturing while minimizing potential tearing of the backing44. In some embodiments, the mesh64may comprise a plurality of randomly aligned fibers. In other embodiments, the mesh64may comprise fibers oriented in a repeating pattern or configuration. In some embodiments, the embedded mesh64may comprise tightly woven fibers. In other embodiments, the mesh64may comprise spaced-apart fibers such that a given fiber is spaced a suitable length from one or more neighboring fibers.

In some embodiments, the outer perimeter of the backing44may be structurally adapted to minimize the propagation of tears should any form in the backing44. As shown inFIG. 7, an alternative embodiment of the electrode structure27may be formed with the backing44having a raised outer rim66, also described as a ridge or a lip structure. The outer rim66may increases the thickness of the backing44along the outer perimeter to minimize tearing during suturing, in some embodiments.

FIGS. 8-11show various embodiments of grooves or through holes68of the backing44adapted to guide suture placement during device implantation. In some embodiments, the backing44of the electrode structure26may include one or more grooves68, also described as indentations or depressions, extending along at least a portion of the first surface52. The one or more grooves68are adapted to allow a suture to partially or fully seat within each groove68, according to some embodiments.

Alternatively, in some embodiments, the backing44may include through holes68within the backing44that are adapted to receive a suture. For example, one or more through holes68may extend across at least a portion of the backing44from a first side56to a second opposite side56and within an area between the first surface52and the second surface54.

As shown inFIGS. 8-10, in some embodiments, the one or more grooves or through holes68may extend across at least a portion of the backing44adjacent to the interior cavities, e.g. the channels60,61and the cavity62. The grooves or through holes68may extend across portions of the backing as shown inFIG. 2A, e.g., the proximal portion46, the distal portion45, or both portions of the backing44, according to some embodiments. Alternatively, as shown inFIG. 11, the grooves or through holes68may extend across portions of the backing44that overlap with the interior cavities, in certain embodiments. Such grooves or through holes68are adapted to extend in a plane superficial to the interior cavities, e.g. extend on a different plane, such that grooves or through holes68do not connect with the interior cavities of the backing44. Adequate suture placement may allow electrodes50,51(FIGS. 2A, 3A-C,4,6and7) to be placed closer to the vessel wall or an anatomical target, for example, the carotid sinus baroreceptors.

FIGS. 12 and 13are top views of the electrode structure26, according to some embodiments, showing the electrode structure in a straight configuration and a curved configuration, respectively. As shown by these figures, the backing44of the electrode structure26may be adapted to include a curved profile that complements the curved profile of a vessel wall. For example, the backing44may be formed into a C-shape, as shown inFIG. 13. In some embodiments, the curvature diameter of the backing44may range from about 5 mm to 15 mm. For example, when coupling the electrode structure26to the internal carotid having a diameter of approximately 10 mm, the curvature of the electrode structure26may range from about 8 mm to 12 mm.

The electrode structure26may serve as a coupling means for positioning two or more electrodes50,51(FIGS. 2A, 3A-C,4,6and7) proximate to a blood vessel, for example, the carotid sinus. A carotid sinus stimulation system including a neurostimulation lead18coupled to the electrode structure26having two or more electrodes50,51may provide improved identification of the area to be simulated. The electrode structure26having at least two electrodes50,51may allow for more than one vector for stimulation. The electrode structure26having at least two or more electrodes50,51may also allow greater energy delivery by increasing the threshold for unwanted extraneous stimulation.

The present invention is more particularly described in the following example, which is intended as illustration only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art.

Sample prototypes of an electrode structure were evaluated to determine a suitable length L1based on a preclinical study using carotid sinus vessels of human models and cadavers.

Sample prototypes of the electrode structure for four test groups were constructed with varying overall lengths L1. Each test group had a sample size of three. The prototypes of this study were constructed using a 3D printer and were made of a standard 3D printing material.

The four test groups, including Groups A1through A4, were constructed with varying body lengths L1. As shown in Table 1 below, the overall length of the samples of each test group was adjusted by varying the edge-to-edge distance between the first and second electrode L2and the edge-to-edge distance between each electrode and the outer perimeter of the body L3along a longitudinal axis X1(seeFIG. 4). The dimensions of all samples assumed a constant electrode diameter D1of 2 mm.

Each sample was sutured to a carotid sinus of a human cadaver by a veterinarian (seeFIG. 14) and subjectively assessed by engineers. Groups A1and A3were assessed as having a suitable length L1that would be likely compatible for suturing to the carotid sinus in humans. In contrast, Groups A2and A4were assessed as likely having too large a length L1and likely being incompatible for carotid sinus suturing. The results of this study suggest that a suitable length for the electrode structure ranges from about 12 mm to 13 mm.

The present invention is more particularly described in the following example, which is intended as illustration only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art.

Sample prototypes of electrode structure bodies were evaluated to determine suitable dimensions based on a preclinical study using carotid sinus vessels of human models and cadavers.

The samples for three test groups, including Groups B1through B3, were constructed using a silicone material. A sample size of three was used for each test group.

As shown in Table 2 andFIG. 15, the test groups B1-B3were constructed with varying body lengths L1and widths W. The overall length of samples in each test group was adjusted by varying the edge-to-edge distance between the first and second electrode L2and the edge-to-edge distance between each electrode and the outer perimeter of the body L3along a longitudinal axis X1(seeFIG. 4). The samples of all test groups assumed a constant electrode diameter D1of 2 mm.

Each sample was sutured to a carotid sinus of a cadaver by a surgeon and subjectively assessed by surgeons and engineers. Group B1was assessed as being likely suitable for vessel suturing to the carotid sinus of a human. Groups B2and B3, however, were assessed as likely being too large and therefore likely unsuitable for carotid sinus suturing. Based on these results, the electrode structure body having a length of about 12 mm and a width of about 8 mm would likely be a suitable dimension for an electrode structure body targeting the human carotid sinus.