1. Field of the Invention
The present invention relates to a connecting device for connection of a medical implantable lead to tissue inside a body, of the type having a helix adapted to be screwed out from a header sleeve at a distal end of the lead and into the tissue, and a shaft which carries the helix and is rotatably journalled in the lead and at the same time displaceable to extend the helix into the tissue.
The invention also relates to a method for manufacturing such a connecting device.
2. Description of the Prior Art
For controlling and/or monitoring of an arbitrary organ inside a human or animal body, e.g. a heart by means of a pacemaker, it is common practice to attach an electrical lead to the organ for transmitting and receiving electrical signals to or from the organ. A common way to accomplish the attachment of the lead to the tissue, is to screw out a helix from a so called header sleeve at a distal end of the lead and into the tissue. The helix will then normally function both as the attachment and as an electrode to transmit and receive the electrical signals.
To accomplish this, the helix is attached to a shaft inside the lead which is rotatably journalled in the lead and displaceable in the longitudinal direction. Such an arrangement will allow rotation and extending of the helix out from the tip of the lead.
One example of a prior art connecting device is disclosed in United States Patent Application Publication No. 2005/0251240 A1. Here, the helix is attached to a shaft by being screwed onto windings formed in the shaft. By rotating the shaft by means of for example a stylet inserted through the lead, the helix as well as the shaft will be screwed in the outward direction from the lead by engagement of the helix windings with a knob on the inside of a header sleeve where the helix is accommodated.
Another example of a prior art connecting device is disclosed in U.S. Pat. No. 5,837,006, where a coiled wire conductor together with a movable stop member functions as a shaft. The helix is attached on the distal end of the stop member and thread around a guide mechanism, such when rotating the wire conductor, the helix together with the stop member and the wire conductor, will be screwed out and advanced forward through the sleeve.
However, there are several disadvantages associated with prior art connecting devices of the above designated kind. The connecting devices used today are composed of at least two components, i.e. a shaft and a helix, that needs to be aligned with each other within tight tolerances and both are complex and expensive to manufacture and a separate assembling process is necessary to accomplish the assembling. The components need also be electrical as well as mechanical connected to each other in a secure and reliable way. In the assembling process of the shaft and the helix it is always a risk that the two components will become misaligned, which is a common reason for rejection with increased costs as a consequence. It is also a risk for poor mechanical and/or electrical contact between the helix and the shaft when assembling them together.
An object of the invention is to reduce the disadvantages with prior art connecting devices. More precisely it is an object of the invention to facilitate and reduce costs for manufacture of the connecting device as well as facilitate assembling of the medical implantable lead.
The invention also relates to a method for manufacturing of a connecting device having essentially the same object as above.
The invention is based on the recognition that the above object may be achieved by making the connecting device in one piece, i.e. the helix and the shaft being integrated and manufactured in the same manufacturing process. In this way it is possible to completely eliminate any misalignment problems between the shaft and the helix. The complexity of the manufacture will also be reduced since any attachment area between the shaft and the helix can be dispensed with as well as the assembly process. Moreover, there is no risk of insufficient mechanical or electrical contact between the helix and the shaft.
Within this general idea, the invention may be modified in many different ways. In one embodiment the combined shaft and helix is manufactured originating from a blank, being a little longer in comparison with prior art shafts, which is formed in accordance with the outer shape of the finished connecting device and then to form a hole or bore a distance along the centre line from the distal end of the connecting device. Subsequently, the helix windings are formed by any suitable material removing process from the outer surface into the bore. The material removing process could preferably be performed by electro erosion or laser cutting, but it can also be done by e.g. milling, water jet cutting or etching. However, it is also possible to manufacture the connecting device by for example moulding or sintering, possible in combination with suitably finishing for obtaining surfaces with high quality.
One advantage with forming the helix windings by a material removing process, is that the form of the helix easily can be altered according to special desires or requirements. For example, the helix can be made with a variable cross section over its length, with projections or the like. On the whole, the invention makes it easier to perform modifications of the shape of the helix windings since it will be only one component that has to be altered instead of at least two in case of a prior art connecting device, assembled from a separate shaft and helix, in which also the mating part of the shaft has to be altered.
Sometimes it is desirable to improve and/or adjust the impedance of the helix surface by coating at least some portions of the surface with an electrical insulating material. By means of the material removing process according to the invention, this selective coating can be facilitated. E.g. when forming the helix of an electrically conducting material, the outer surface of the blank as well as, if desirable, also the inner surface of the bore, can easily be coated with an electrically insulating material, such that when the helix windings are formed by a material removing process, the cut edge surfaces of the helix windings will be electrically conductive. On the other hand, when forming the helix of an electrically insulating material, the outer surface of the blank as well as, if desirable, also the inner surface of the bore, can easily be coated with an electrically conducting material, such that when the helix windings are formed by a material removing process, the cut edge surfaces of the helix winding will be electrically insulated.
Reference is first made to
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In
In
Subsequently, the outer contour of the connecting device is formed in the blank according to
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In a last step, according to
Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/SE06/01204 | 10/24/2006 | WO | 00 | 4/9/2009 |