The present invention relates generally to a medical implant and a medical arrangement comprising such an implant. In addition to implantable electrode leads (also referred to in the following description as “electrode leads”) or sensor leads of the type used in cardiac pacemakers or implantable cardioverters, for example, the term “implant” also relates—within the scope of this patent application—to so-called “leadless pacers” (e.g., leadless cardiac pacemakers), of the type described in European Patent No. EP 1 714 670, for example, or “leadless sensors” which are sensors comprising a transmitter/receiver unit and which can be implanted into the vascular system of a living organism or subcutanteously.
The explantation of adhered electrode leads presents great difficulties to a physician. Previously, an electrode lead has been “cut out” for explantation, e.g., using laser cutting or conventional knives. At the same time, a tensile force must be applied to the electrode lead, although it must not cause the lead to tear. Special systems for achieving this difficult objective have been developed, such as, for example, an electrode extraction system from the company VascoMed GmbH.
Various coatings (e.g., polymer-based) have also been known for a long time, which are intended to impede the adhesion of electrode leads or other medical implants in the body, or coatings that release active agents (e.g., drug-eluting coatings) which are intended to prevent adhesion via this release of active agent.
A coating of an implant is achieved, for example, by embedding a hydrophilic interface between the implant surface and the bodily fluid. As a result, inflammatory reactions of the surrounding tissue and adhesions are minimized. A plurality of natural, synthetic and semi-synthetic materials are currently in use for implant coatings. Naturally occurring materials containing, for example, alginate, chitosan, collagen, dextrane and hyaluronan, synthetic polymer materials as coating materials are, e.g., poly(lactic acid) and poly(lactic co-glycolic acid) (PLGA), 2-hydroxyethyl methacrylate, poly(ethylene glycol) (PEG), and poly(vinyl alcohol) (PVA). However, not all of these materials exhibit the desired properties over the long term. Many do not provide adequate mechanical loadability, chemical stability or biocompatibility for all applications and, therefore, adhesion cannot be fully prevented.
The foreign-body reaction to an implant can be minimized or even controlled by the use of steroidal and non-steroidal anti-inflammatory drugs. Glucocorticoids have been used, for example.
Over the long term, most electrode leads adhere to the points at which they rest against the wall of the blood vessel, and therefore cannot be explanted, or only explanted with great difficulty. Many of the above-mentioned materials are suitable only for a limited period of time and cannot permanently prevent the foreign-body reaction and, therefore, adhesion of implants, in particular electrode leads, sensors (connected to leads, or leadless) or leadless pacers. So far, no coatings—either pure polymers or drug-eluting polymers—have been known that solve the problem over periods of time longer than several months.
Explantation of electrode leads in the vicinity of the heart, in particular, is associated with a high risk that important blood vessels or the heart will be injured, in particular, if the electrode leads have adhered, even when specially developed systems are used and the operating surgeon is highly experienced. For this reason, they often remain in the body when they should be replaced.
Although the risks associated with an electrode lead remaining in the body are difficult to assess, they are tolerated at the moment in order to avoid the considerably higher risks associated with explantation, especially in the vicinity of the heart.
The present invention is directed toward overcoming one or more of the above-identified problems. A problem addressed by the present invention is that of providing a medical implant that is more suitable with regard to potential explantation.
A problem is solved by an implant having the features of the independent claim(s). Advantageous developments of the inventive idea are the subject matter of the dependent claims. Moreover, a medical arrangement having the features of claim 14 is provided.
The present invention is based on the premise of avoiding the previously common application of high tensile forces for the explantation of medical implants according to the initially stated definition for removal from the tissue environment into which they have adhered. It is further based on the premise, instead, of causing the implant to vibrate, e.g., to more or less “shake”, in order to release it from the tissue environment. Finally, the present invention incorporates the idea of not generating the mechanical vibrations outside of the body and transferring them to the implant by way of a mechanical transmission element but, rather, to generate them directly in the implant by way of suitable energy conversion. For this purpose, a transducer element is provided in the implant, which induces mechanical vibration of the implant when electrically and/or magnetically controlled, to thereby bring about a release from the tissue environment or at least a loosening therefrom. It should be pointed out that this release or loosening does not necessarily have to take place only for the purpose of and at the moment of explantation but, rather, could also be carried out for the purpose of prevention, to prevent fixed adhesion, e.g., at greater intervals during the service life of a long-term implant.
A transducer element in the tip of an electrode or sensor lead, or in a leadless pacer/sensor or a similar implant, will greatly simplify the development of future implant coatings, since it thereby becomes less necessary to keep endogenous cells and adhesions away. A low grade of adhesion can be tolerated because the present invention makes explantation possible despite adhesion in and to bodily tissue.
In addition, drug-eluting coatings which can harm the body are avoided. It is possible to control the point of time at which the implant should be released by the tissue upon explantation.
A further advantage is provided since the endogenous adhesions additionally stabilize the position of the implant. This is of particular significance for lead-connected or leadless sensors located in the pulmonary artery or the vena cava before the heart. If the sensors would slip, serious complications could result.
In one embodiment of the present invention, the implant comprises a transducer element that couples inductively to an alternating magnetic field. In an embodiment that is preferred from a current perspective, however, it is an electrically controllable transducer element, such as, for example, a piezoceramic vibration element.
In a further embodiment, the transducer element is in the form of a separate transducer element inserted into the implant. In another embodiment, the transducer element is disposed in the wall region, in particular, being embedded in the wall over a large surface area. If the latter embodiment is combined with the embodiment as an electrically controllable piezo element, an advantageous embodiment results in which the transducer element comprises a piezoceramic foil or a piezoelectric polymer foil.
The above-mentioned piezo foils are a few μm thick and do not substantially increase the diameter of an implant. They can be produced in a tube shape, for example, which results in a few advantages in production. It should also be provided that the piezo foils extend along the entire longitudinal axis of the implant, if possible, because it is impossible to determine exactly where an implant will adhere into the tissue.
In a further embodiment of the present invention, the proposed implant comprises an electrical connection for contacting the transducer element by way of a temporary control line serving as an explantation tool. In another embodiment, an integrated control line is provided for connection to an internal control device, a control device disposed in a further implant, or an extracorporeal control device.
In yet another embodiment, the transducer element is designed, or additional energy-supply means are provided, such that wireless control can take place by way of an extracorporeally generated, alternating magnetic field (generated by an excitation coil held at the body in the vicinity of the implant, for example). An advantage of the wireless energy supply of the transducer element would be that no additional technology would be required in the main implant, and no additional electrode leads would be required.
In an application of the present invention that is particularly important from a current perspective, the implant is designed as an implantable electrode lead or sensor lead. In a further embodiment that is interesting with regard to perspective, the implant is a leadless cardiac stimulation device or cardioversion device, or a lead-connected or leadless sensor for intracorporeal, physical, physiological or biochemical measured quantities, which is known per se having a cylindrical basic shape. In both application forms, a piezoceramic foil or a piezoelectric polymer foil, in particular, in sleeve form or annular segment form, can be disposed, advantageously, in or on the wall of a distal section.
The proposed medical arrangement which comprises an implant of the above-described type furthermore comprises a control device for the electrical and/or magnetic control of the transducer element and coupling means for coupling energy therein. It can be an arrangement (comprising, for example, a pacemaker electrode lead and a specially equipped cardiac pacemaker) which is implantable in its entirety. From a current perspective, however, an arrangement in which the control device is in the form of an extracorporeal explantation support device is clinically more interesting.
Further features, aspects, objects, advantages, and possible applications of the present invention will become apparent from a study of the exemplary embodiments and examples described below, in combination with the figures, and the appended claims.
Advantages and useful features of the present invention will also become apparent from the basic description that follows of exemplary embodiments, with reference to the figures. In the figures:
If an alternating voltage having a suitable frequency and voltage is applied to the piezoceramic foil 102, it radiates acoustic waves. The radiated acoustic waves induce the separation or loosening of the adhesion from the surface of the electrode. The frequency of the impressed alternating voltage can be, for example, in the range of 20 kHz to 20 MHz, and preferably, a frequency between 50 kHz and 100 kHz is used. The alternating voltage can be impressed as a continuous alternating voltage having an arbitrary curve shape, or in the form of bursts or pulses.
In a variant of the embodiment depicted, the transducer element can be designed with annular segments which are electrically interconnected, and it can be made of a piezoelectric material, e.g., lead zirconate titante (PZT), barium titanate or lithium niobate. The flexibility of the electrode in this region is increased by way of the annular segments. Alternatively to the piezoceramic foil, it is also possible to use a foil made of a piezoelectric polymer (e.g., PVDF; polyvinylidene fluoride).
By way of this coil 205, the energy for generating the acoustic wave is supplied wirelessly using magnetic-inductive coupling. In explantation, this takes place by way of a suitable (not depicted) transmit coil which is held at the body on the outside. This solution has the advantage that the electrode does not require any additional connectors and no additional special devices are required in the IMD for generating and supplying the alternating voltage. This electrode is therefore fully compatible with conventional electrode connectors and IMDs.
A further possibility for generating the required acoustic waves is therefore utilized. Capacitive pressure sensors can be used to generate acoustic waves by applying an alternating voltage to the pressure-measuring capacitor. They then function (quasi inversely) as CMUTs (capacitive micromachined ultrasonic transducers). The device for generating the alternating voltage can be included, for example, in the devices for determining the pressure signal on the basis of the capacitance of the capacitive pressure sensor. Alternatively, this alternating voltage can likewise be coupled wirelessly magnetically-inductively by way of a suitable coil.
As an alternative embodiment,
The embodiments of the present invention are not limited to the above-described examples and emphasized aspects but, rather, are possible in a large number of modifications that lie within the scope of handling by a person skilled in the art.
It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range.
This patent application claims the benefit of co-pending U.S. Provisional Patent Application No. 61/568,176, filed on Dec. 8, 2011, which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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61568176 | Dec 2011 | US |