1. Field of the Invention
The invention relates to a medical implantable lead, which is adapted to be attached with a distal end to tissue inside a human or animal body and that has a flexible sleeve in the distal end that protrudes a distance in an axial direction from the rest of the lead, of the type wherein, when in a desired position, a force acting in an axial direction on the flexible sleeve will bring the sleeve to be compressed in the axial direction such that the surface area of the distal end will be enlarged.
2. Description of the Prior Art
Medical implantable leads of various kinds and for various applications, e.g. for monitoring and controlling the heart in a human or animal body by means of a pacemaker, tend to become smaller and smaller in cross section. A medical implantable lead for pacemaker applications, for example, can have a diameter of less than 2 mm. This is advantageous in one aspect, since then the lead will be more flexible and take up less space. However, there are also risks with leads having a too small cross sectional dimension. In many cases the leads are namely adapted to be mounted to an organ inside the body, e.g. a heart wall, with its end surface abutting the organ and held by means of for example a helix, which is screwed into the organ. If the cross sectional dimension of the lead is too small in relation to its stiffness, it is a risk that the lead tip will perforate the organ during mounting of the lead and cause bleeding. This risk exists on the one hand when the distal end is pressed against the organ but before the lead is actually attached to it. In case the lead is provided with a rotatable helix for attaching to the organ, this risk also exists when the helix is screwed into the organ such that the distal end is drawn into the tissue by means of the rotating action of the helix. When the lead is attached to e.g. a heart, which performs large movements during function, there is also a risk that the heart wall will be perforated or injured during the course of a longer period of time when the lead is attached, due to abrasion or the like, if the lead is made with a too small cross sectional dimension in relation to its stiffness.
From United States Patent Application Publication No. 2007/0050003 A1, a medical implantable lead is known, which in one embodiment (
It is an object of the invention to provide an improved medical implantable lead by which the risk of perforation into tissue is eliminated or reduced and yet can ensure secure attachment to tissue.
The basis of the invention is the insight that the above object may be achieved by providing the medical implantable lead with means for varying the surface area of the distal end of the lead, such that the surface area has a minimum when introducing the lead into the body. Once the lead is localised inside the body, the surface area of the distal end can be enlarged when abutting the distal end against an organ or other tissue.
According to the invention, the enlargement of the surface area is accomplished by mechanically folding material portions at the distal end. More precisely, the distal end of the lead has a flexible sleeve, of e.g. silicone plastics, which protrudes a distance beyond the rest of the medical implantable lead. The outermost, distal end of the flexible sleeve is unbroken and hold together as a ring segment, whereas it is provided with slots in the axial direction of the lead, from the unbroken ring segment and a distance in the proximal direction, such that flexible segments are formed in the sleeve. When applying an axial force on the sleeve in the axial direction towards the proximal end, the flexible segments will be folded outwards and increases in this way the surface area of the lead end. The axial force can be applied in different ways, e.g. by pressing the distal end against tissue or by letting a rotatable helix engage with some kind of engagement formation on the ring segment, such as an engagement post on the inside of the ring segment or an aperture in a disk positioned over the distal end of the ring segment. The latter requires, as in the embodiment described and illustrated below, that the helix is rotatable from the proximal end of the lead, by any suitable means known in the art, but is not displaceable in the axial direction of the lead during rotation. The displaceable arrangement of the helix is normally done to withdraw the helix into a tubular header such that the helix is accommodated in the header to prevent it from penetrating and causing damage during introduction into the body. In this case this is not necessary since the flexible sleeve will cover the helix during introduction.
Normally, at least four flexible segments are required for performing the folding of the flexible segments without having to use an excessive force to accomplish the folding of the sleeve. The length of the slotted portion of the sleeve is preferably from the ring segment to the position of the distal end of the rest of the lead and can suitably have a length of about 1,5-2 mm.
To facilitate folding of the sleeve segments, they can, as in a hereinafter described and illustrated embodiment, be provided with one or more grooves around the circumference of the sleeve on the side of the sleeve towards which the sleeve segments will be folded. More precisely, on the inside of the sleeve in the middle of each sleeve segment and preferably also on the outside in the respective ends of the segments, wherein the innermost groove is located at the position of the distal end of the rest of the lead.
It is preferred for the sleeve in the folded and mounted state, not to press outwardly in the axial direction with a force against the tissue, which might lead to that the attachment to the organ in the course of time might become disconnected. This may be achieved in different ways, e.g. by a helix being in engagement with an engagement formation on the ring segment, such as a post on the inside of the unbroken ring or an aperture in a disk, or by means of a circumferential groove, which does not divide each segment into two equal parts but one part is longer than the other such that a dead centre locking is achieved of the flexible segments in the folded position. It is also possible to make the sleeve in a preformed folded position and let the helix stretch out the sleeve during insertion by means of engagement with an engagement formation. When attaching the lead to tissue by rotating the helix, the sleeve will be folded to the preformed shape.
In the drawings is illustrated one embodiment of the invention in form of a medical implantable lead adapted to be used in connection with a pacemaker or with an implantable cardioverter defibrillator. Accordingly, the lead comprises a considerably long electrical lead 1, of which only a distal end is shown in the drawings. A pacemaker is adapted to be connected to a proximal end of the lead, whereas a distal end 2 is adapted to be attached to a heart wall 3. As is best seen in
The sleeve is formed with an unbroken ring segment 7 in its distal end and axial slots 8, which extends from the unbroken ring segment 7 and a distance inwards, preferably to the distal end of the rest of the lead. In this way flexible segments 9 are formed between adjacent slots 8. On the inner side, the unbroken ring segment 7 is provided with an engagement means in form of a post 10, which is in engagement with the helix winding 5.
When implanting the lead into a human or animal body, e.g. by introducing it through a vein 11, as is illustrated in
To facilitate folding of the flexible segments, these are provided with grooves 12 in a circumferential direction of the lead in the areas where the segments 9 are folded, i.e. in each end of the segments 9 as well as in the middle of each segment. The grooves 12 are best seen in
In
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 |
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PCT/SE2007/000470 | 5/15/2007 | WO | 00 | 11/10/2009 |