This patent document pertains generally to implantable defibrillator leads. More particularly, but not by way of limitation, this patent document pertains to the attachment of fibrosis-limiting material to one or more portions of an implantable defibrillator lead.
Cardiac and other defibrillation systems typically include an implantable medical device (IMD), such as a pulse generator, electrically connected to the heart by at least one implantable defibrillator lead. More specifically, an implantable defibrillator lead provides an electrical pathway between the IMD, connected to a proximal end of the lead, and cardiac tissue, in contact with a distal end of the lead. In such a manner, electrical stimulation (e.g., in the form of one or more shocks or countershocks) emitted by the IMD may travel through the implantable defibrillator lead and stimulate the heart via one or more exposed, helically wound shocking coil electrodes located at or near the lead distal end portion. Once implanted, the exposed shocking coil electrodes often become entangled with fibrosis (i.e., a capsule of inactive tissue which grows into the exposed coils) with the end result being that a chronically implanted lead can be extremely difficult to remove by the application of tensile force to the lead proximal end.
Over time, situations may arise which require the removal and replacement of an implanted defibrillator lead. As one example, an implanted defibrillator lead may need to be replaced when it has failed, or if a new type of cardiac device is being implanted which requires a different type of lead system. As another example, bodily infection or shocking coil electrode dislodgement may require the replacement of an implanted defibrillator lead. In such situations, the implanted defibrillator lead may be removed and replaced with one or more different implantable leads.
To allow for easier removal, some implantable defibrillator leads include a fibrosis-limiting material covering a portion of the one or more otherwise exposed shocking coil electrodes thereon. Unfortunately, current fibrosis-limiting materials are applied to the shocking coil electrodes in ways that lack sufficient attachment strength. As a result, when subjected to shear loads, such as during lead implantation procedures, the fibrosis-limiting material may separate from the associated shocking coil electrode or the shocking coil electrodes themselves may separate from the lead body or deform, thereby leaving uncovered coils that are subject to future fibrotic entanglement.
Certain examples of the present subject matter include a lead comprising a lead body, at least one shocking coil electrode, and a fibrosis-limiting material. The lead body extends from a lead proximal end portion to a lead distal end portion and may optionally include an inner insulating layer and an outer insulating layer. At least one shocking coil electrode is disposed at one or both of the lead intermediate portion or the lead distal end portion. The fibrosis-limiting material coaxially surrounds, at least in part, the at least one shocking coil electrode and a portion thereof extends proximal or distal to a shocking coil electrode end. This extending portion of the fibrosis-limiting material can be disposed between a first lead component and a second lead component, such as the inner insulating layer and the outer insulating layer of the lead body, for example.
Certain examples of the present subject matter include a lead comprising a lead body, at least one shocking coil electrode, a fibrosis-limiting material, and a length of compression tubing. The lead body optionally includes an inner insulating layer and an outer insulating layer. The at least one shocking coil electrode is disposed on the lead body and is surrounded, at least in part, by the fibrosis-limiting material. The length of compression tubing extends from a tubing first portion to a tubing second portion. The tubing first portion is disposed over a shocking coil electrode end and the tubing second portion is disposed between a first lead component and a second lead component.
Certain examples of the present subject matter include a method comprising coaxially fitting a fibrosis-limiting material over at least one shocking coil electrode, forming the fibrosis-limiting material onto an outer surface of the at least one shocking coil electrode, coupling one or more portions of the at least one shocking coil electrode to a lead body or component, and disposing an extending portion of the fibrosis-limiting material between a first lead component and a second lead component. The coaxial fitting of the fibrosis-limiting material over the at least one shocking coil electrode includes positioning the extending portion of the fibrosis-limiting material proximal or distal to a shocking coil electrode end.
Advantageously, the present leads and methods decrease the likelihood of moving or shifting between a shocking coil electrode and a fibrosis-limiting material covering thereon or between the shocking coil electrode and adjacent portions of a lead body, such as during the lead implantation process. In this way, there is a reduction or elimination of uncovered, implanted shocking coil electrodes that are subject to future fibrotic entanglement, thereby improving the ease of chronic lead extraction should it become necessary. Additionally, the present leads and methods provide smooth transitions at the lead body-shocking coil electrode interface, which also facilitate lead implantation and extractability. These and other examples, advantages, and features of the present leads and methods will be set forth in part in the detailed description, which follows, and in part will become apparent to those skilled in the art by reference to the following description of the present leads, methods, and drawings or by practice of the same.
In the drawings, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the present leads and methods may be practiced. These embodiments, which are also referred to herein as “examples,” are described in enough detail to enable those skilled in the art to practice the present leads and methods. The embodiments may be combined, other embodiments may be utilized or structural or logical changes may be made without departing from the scope of the present leads and methods. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present leads and methods is defined by the appended claims and their legal equivalents.
In this document, the terms “a” or “an” are used to include one or more than one, and the term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation.
Fibrosis-limiting material coverings for shocking coil electrodes facilitate the extractability ease of chronically implanted defibrillator leads. Unfortunately, the nature of fibrosis-limiting materials and previous manufacturing methods to attach such materials to the shocking coil electrodes lack in physical strength. As one example, certain fibrosis-limiting materials, such as expanded polytetrafluoroethylene (ePTFE), resist adhesion due to their chemical nature and require extremely high heat to sinter to a shocking coil electrode. This high heat exceeds temperatures that many lead body materials can withstand. For at least this reason, previous shocking coil electrodes that are partially surrounded by a fibrosis-limiting material are typically attached to a lead body solely at their very ends using, for example, a medical adhesive.
It has been found that when implanting such previously manufactured defibrillator leads, high drag forces are created along the lead body (e.g., due to an introducer seal of a hemostatic introducer). As a result, several lead component interfaces, including the fibrosis-limiting material to shocking coil electrode and the shocking coil electrode to lead body, have a tendency to separate or shift relative to one another leaving one or more uncovered coils. Advantageously, the present leads and methods provide improved attachment strength between the fibrosis-limiting material, the shocking coil electrodes, and the lead body, and as a result, reduce or eliminate the presence of uncovered, implanted shocking coil electrodes which are subject to future fibrotic entanglement.
The implantable defibrillator lead 104 transmits electrical signals between a selected location within, on, or about the heart 114 and the IMD 102, such as to monitor the heart's 114 electrical activity at the selected location or to carry stimulation signals (e.g., one or more shocks or countershocks) to the selected location from the IMD 102. The implantable defibrillator lead 104 may include a fixation assembly, such as one or more tines 118 or a helical coil, to anchor the lead distal end portion 118 at the selected located. The one or more tines 118 may be formed as part of the lead body 120, and thus may include a biocompatible lead body material, such as silicone rubber, polyurethane, polyimide, or a non-porous fluoropolymer.
In this example, the lead intermediate portion 116 and the lead distal end portion 108 include a first and a second shocking coil electrode 110. The first and second shocking coil electrodes 110 comprise an uninsulated, helically wound shocking coil formed of a non-corrosive, bio-compatible metal, such as platinum, titanium, or alloys (e.g., platinum/iridium). The shocking coil electrodes 110 are covered by a pliable fibrosis-limiting material 112 (e.g., polytetrafluoroethylene (PTFE) or expanded PTFE (ePTFE)) in direct contact with an outer surface 370 (
As shown, but as may vary, the lead proximal end portion 106 includes three terminal leg connections 206 each of which is sized and shaped to couple to respective connector cavities incorporated into a header of the IMD 102 (
Options for the fibrosis-limiting material 112 are numerous. For instance, the fibrosis-limiting material 112 may include PTFE, ePTFE, or other non-biodegradable and biocompatible materials, such as expanded ultra-high molecular weight polyethylene (eUHMWPE); may either be porous or non-porous; or may be inherently conductive or rely on porosity in conjunction with bodily fluids to be conductive. In various porous examples, the pore size is adequately small to allow penetration of conductive bodily fluids while substantially precluding tissue ingrowth, thus allowing a less traumatic removal of the defibrillator lead 104 after implantation should extraction become necessary. In various other examples, electrical conductivity through the fibrosis-limiting material 112 is not based on porosity, but rather is inherent in the material 112 as described in commonly-assigned Krishnan, U.S. Pat. No. 7,013,182 titled “CONDUCTIVE POLYMER SHEATH ON DEFIBRILLATOR SHOCKING COIL,” which is hereby incorporated by reference in its entirety.
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Implantable defibrillator leads 104 are often placed in contact with cardiac tissue by passage through a venous access, such as the subclavian vein, the cephalic vein, or one of its tributaries. In such a manner, an implantable defibrillator lead 104 may advantageously be placed in contact with the heart 114 (
When a physician implants a defibrillator lead 104, such as through the introducer sheath 600 and specifically an introducer seal 604, high drag forces may be created along the lead body 120. As a result of these high drag forces, previous lead component interfaces including the fibrosis-limiting material 112 to shocking coil electrode 110 and the shocking coil electrode 110 to the lead body 120 tended to separate or shift relative to one another leaving uncovered coil portions subjected to future fibrotic entanglement (e.g., the shocking coil electrode 110 became stretched, which in turn pulled the fibrosis-limiting material 112 away from the coil 110 and exposed a portion of the coil to fibrotic growth). Using the present attachment techniques, it has been found that such separating or shifting between the fibrosis-limiting material 112, the shocking coil electrode 110, and the lead body 120 is reduced or eliminated, thereby preventing fibrotic entanglement and facilitating lead extraction should it become necessary.
At 808, the proximal or distal portion of the fibrosis-limiting material is disposed between a first lead component and a second lead component. In one example, this disposition between the first and the second lead component includes disposing the fibrosis-limiting material between a lead body inner insulating layer and a lead body outer insulating layer. In another example, the disposition between the first and the second lead component includes disposing the fibrosis-limiting material between a rigid or semi-rigid core member and a rigid partial band or ring member sized and shaped to couple around the rigid core member. Optionally, at 810, a length of compression tubing is disposed between the at least one shocking coil electrode and the fibrosis-limiting material on a tubing first portion and between a lead body inner insulating layer and the fibrosis-limiting material on a tubing second portion.
Leads and methods for improved attachment strength between a fibrosis-limiting material, a shocking coil electrode, and a lead body are discussed. Advantageously, the present leads and methods decrease the likelihood of moving or shifting between such components and, in this way, reduces or eliminates the presence of uncovered, implanted shocking coil electrodes subjected to future fibrotic entanglement. Additionally, the present leads and methods provide smooth transitions at the lead body-shocking coil electrode interface, which facilitate lead implantation and extractability.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For instance, any of the aforementioned examples may be used individually or with any of the other examples. In addition, the aforementioned examples may or may not include the use of adhesives (e.g., medical adhesives) for selected component attachment. Many other embodiments may be apparent to those of skill in the art upon reviewing the above description. The scope of the present leads and methods should, therefore, be determined with reference to the appended claims, along with the full scope of legal equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, assembly, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of such claim.
The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together to streamline the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may lie in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.