WO2003092797A1

WO2003092797A1 - Epicardial pacing lead arrangement

Info

Publication number: WO2003092797A1
Application number: PCT/SE2003/000268
Authority: WO
Inventors: Rolf Hill
Original assignee: St Jude Medical Ab
Priority date: 2002-04-30
Filing date: 2003-02-18
Publication date: 2003-11-13
Also published as: SE0201320D0

Abstract

The present invention relates to an epicardial pacing lead arrangement, comprising an electrode support which holds at least one electrode. Fixation means are arranged on a portion of the electrode support for fixating it to the cardiac tissue. Said portion of the electrode support is controllable between a preformed shape and a deformed shape for causing a change between a locking position and a release position of the fixation means. The invention also relates to a tool for an epicardial pacing lead arrangement.

Description

EPICARDIAL PACING LEAD ARRANGEMENT

Technical Field of the Invention

The present invention relates to an epicardial pacing lead arrangement and a tool for an epicardial pacing lead arrangement.

Description of Prior Art

An epicardial pacing lead may be a bipolar (or unipolar or multipolar) electrode lead used for providing epicardial stimulation of cardiac tissue, and/or for sensing heart signals, by means of a pulse generator or some other type of heart stimulation apparatus. The pacing lead carries the stimulus from the pulse generator to the cardiac tissue, or relays intrinsic cardiac signals back to a sense amplifier of such pulse generator. The electrode of the epicardial pacing lead is placed on the exterior surface of the heart. The use of epicardial pacing leads may in some cases be preferred to the use of coronary sine pacing leads, since the latter involves difficult access and fixation in the coronary sine.

However, a physician will often open the chest of the patient in order to place the electrode on the exterior surface of the heart. This means that the patient should previously be heavily anaesthetized. The electrode, being commonly provided on a flat support. To hold the electrode in place, the support is sutured to the epicardial surface of the heart. A sutureless alternative is a screw-in electrode, wherein the electrode is screwed into the epicardial surface of the heart. Another alternative arrangement is disclosed in US 4,177,818, in which a number of teeth are driven into the epicardial surface of the heart in order to hold the electrode in place. Just like the previous alternatives this arrangement requires the chest of the patient to be opened. Instead of thoracotomy, opening the chest, thoracoscopy may be utilized, wherein small penetrations in the chest provide openings for an introducer through which the pacing lead is introducible. However, with such an approach it may be difficult to obtain good positioning, or subsequent repositioning, and fixation. An epicardial lead disclosed in US 5,871,532 aims at providing an improved pacing lead which is suitable for being introduced by means of thoracoscopy. The electrode of the pacing lead is fixed to the heart by means of a fixation mechanism including a pivotable hook that is manipulated by a stylet. The possibilities of manipulating and controlling the fixation mechanism are quite limited. Furthermore, there may be difficulties in enabling satisfactory contact of the electrode with the epicardium. Objects of the Invention

An object of the present invention is to provide an epicardial pacing lead arrangement and a tool therefore which alleviate the drawbacks of the prior art.

Another object of the invention is to provide an efficient controllability of the pacing lead arrangement, facilitating implantation, repositioning and explantation.

A further object of the present invention is to provide an epicardial pacing lead arrangement and a tool therefore which are usable in connection with thoracoscopic surgery.

Summary of the Invention

The above mentioned and other objects, which will become apparent in the following, are achieved with an epicardial pacing lead arrangement as defined in claim 1 and a tool as defined in claim 15. In the dependent claims 2-14 and 16-20 there are stated additional features developing the invention further, and being characteristic of various preferred embodiments thereof.

The invention is based on the insight that the actual electrode support (i.e. the support that holds at least one electrode), or a portion thereof on which fixation means are arranged, can be made controllable in order to accomplish a fixation of the electrode support, even if only small spaces are available. By controlling said portion of the electrode support between a preformed shape and a deformed shape the fixation means thereon may indirectly also be controlled. Furthermore, by making it possible to perform such a shape deformation in a plane in which the electrode support has its largest plane of extension the electrode support need not be lifted unnecessarily from the epicardial tissue of the heart, which is advantageous in view of the limited space available during thoracoscopy. Thus, the present invention takes into consideration the environment in which it is applied by making use of the electrode support as described above. Consequently, according to one aspect of the present invention an epicardial pacing lead arrangement is provided. The arrangement comprises at least a lead body, an electrode support and fixation means. The lead body has a proximal end and a distal end. It should be understood that in this disclosure the terms "distal" and "proximal" are from an operator point of view and not from a patient point of view. The electrode support is coupled to said distal end of the pacing lead and holds at least one electrode for carrying electrical signals to or from cardiac tissue. Fixation means are arranged on a portion of the electrode support for fixating it to the cardiac tissue. Said portion of the electrode support is controllable between a preformed shape and a deformed shape for causing a change between a locking position and a release position of the fixation means. Said portion of the electrode support is deformable predominantly in a plane in which the electrode support has its largest plane of extension, i.e. the change of shape will occur mainly in the largest plane of the electrode support.

Preformed shape is herein meant to be a given shape of said portion of the electrode support, i.e. a biased condition when essentially no external forces affect it. Deformed shape is herein meant to be a shape having a different geometrical configuration than the preformed shape.

As will be described in more detail further on the fixation means may comprise hooks, clamps or the like which enable fixation and repositioning of the electrode support.

The portion of the electrode support on which the fixation means are arranged is suitably resilient and bendable in at least one bending direction. Such a flexibility enables said portion to be easily controllable between the preformed shape and the deformed shape. This flexibility may also contribute in conforming the electrode support with the outer structure of the heart, whereby a good mechanical match is attainable between the electrode and the heart wall. The portion of the electrode support on which the fixation means are arranged is preferably flat, such as in the form of a pad or plate. A flat pad may be described as having a general length, width and thickness, wherein the plane defined by the length and the width is the largest plane of extension. As the pad is bent in a bending direction its overall configuration will be changed, and each fixation means will consequently be subject to a relative movement from its original location in space and/or in respect of another fixation means.

The above described portion may, according to at least one embodiment of the invention, be a distinct portion that is controllable between the preformed and deformed shapes, while the rest of the electrode support does not have to follow the same movement pattern. The rest of the electrode portion may even be kept still.

While the fixation means are arranged on said portion to be controlled, the electrode may be held on a different portion of the electrode support.

According to at least one other embodiment of the invention said portion essentially constitutes the electrode support. This means that the electrode support per se is controllable between a preformed shape and a deformed shape. In other words, the electrode and the fixation means are provided on one and the same bendable element. As can be noted, different alternatives are possible. However, they all have in common that it is the actual electrode support (the entire or a part thereof) which is controlled and thereby affecting the motion of the fixation means. If several fixation means are arranged on the electrode support, it is possible to affect them simultaneously by changing the shape of the electrode support. In other words, a single unit (the electrode support), which may be relatively large, is controlled in order to provide fixation of the same. This is clearly different from prior art thoracoscopy epicardial leads in which the fixation means have traditionally been directly controlled in order to fixate the electrode support. Preferably, the fixation means are arranged to be in the locking position when the electrode support (entire or a part thereof) is in its preformed shape, and hence, in the release position when the electrode support is in its deformed shape. Therefore, in order to fixate the electrode support to the heart wall it should typically be changed from the deformed shape to the preformed shape so that the fixation means will assume the locking position. Prior to that change, the electrode support would normally be inserted and placed at the heart wall in its preformed shape, meaning that two changes will be made - first to deformed and than back to preformed shape. It is the actual motion or change from the deformed shape to the preformed shape that causes the fixation means to lock the electrode support to the tissue. Conversely, once the electrode support is fixated to the heart wall, the change from preformed shape to the deformed shape causes the fixation means to release the electrode support from the tissue.

Suitably, the electrode support is designed in the form of a housing comprising one or more electrode aperture through which an electrode is exposed. The fixation means may protrude from the housing, such as from the surface of the housing. In this design, the housing is controllable between its preformed shape and its deformed shape. The housing may then further be designed so that the distal end of the conductor(s) of the epicardial pacing lead is enclosed by the housing. If the bipolar pacing lead is of bipolar type, the electrodes, i.e. the cathode and anode, are suitably exposed through different and spaced apertures of the housing. Suitably, they are arranged along a common geometrical axis, when the housing is in its preformed shape. In such case, the two conductors would extend different distances inside the housing shorter to contacting the respective electrode. The conductors suitably extend concentrically along said geometrical axis inside the housing. The change of shape of the electrode support (entire or a part thereof) is preferably achieved by designing it so that an area will have a smaller extension in the bending direction than neighbouring areas. For instance, if the electrode support would have the form of an elongate pad which is bendable in its transverse (width) direction, a first area would have a first transverse dimension and one or more neighbouring second areas would have a second transverse dimension, the first transverse dimension being smaller than the second transverse dimension. A desired bending stress of the electrode support may be obtained selecting the dimensions of the areas, since the bending stress is, inter alia, dependent on the difference or ratio between the smaller and larger areas' length in the bending direction.

According to at least one embodiment of the present invention, the electrode support (entire or a part thereof) is designed so that said area having a smaller extension is located intermediate to two end areas. Hence, the intermediate area is a waist area located adjacent the two end areas, one on each side of the waist area. In its preformed shape the electrode support is generally straight. The waist area has the function similar to a hinge around which the end areas are turnable. The deformed shape, will therefore be a C-shape if both end areas are actuated upon or possibly a J- shape if only one end area is actuated upon.

The thickness and the width of the waist is chosen so that a desired flexibility is achieved. The electrode support may therefore be designed to be bendable in both the thickness direction and the width direction of the waist. However, in view of the small spaces available during thoracoscopy it is advantageous if the electrode support can be held as close to the epicardial tissue as possible during deformation of the electrode support. Therefore, in accordance with the invention, even though the electrode support may be bendable also in the thickness direction of the waste, the main bending will be performed in the width direction. It is to be understood that the electrode support may be controllable so that essentially no deformation takes place in the thickness direction, i.e. transversely to the largest plane of extension. As an alternative to bending, the deformed shape may be achieved by compressing the electrode support (entire or apart thereof). Such a compressing action would be possible for any electrode support according to the invention. Likewise, the deformed shape could be accomplished by a stretching action instead of a compressing action. Furthermore, a partial twisting of the electrode support around its axis would be an alternative deformed shape.

If the epicardial pacing lead is implemented as a bipolar pacing lead comprising a waist designed electrode support as described above, the cathode is suitably arranged in one of said end areas and the anode in the other one of said end areas. The distance between the cathode and the anode could suitably be up to 20 mm, for example 10 mm. A steroid plug is suitably arranged in the vicinity of the tissue stimulating cathode. This may be adapted for practically any design of the electrode support. For a waist designed electrode support, the steroid plug would be located in the same end area as the cathode. The steroid, such as e.g. sodium phosphate, is mixed with a carrier or dispenser, such as e.g. silicone glue, which is moulded to a plug having a typical diameter of about 1 mm. Inside the patient the steroid will leak out from the plug and serve as medication preventing or at least mitigating, inter alia, irritation of the tissue around the cathode.

The fixation means arranged on the electrode support may comprise hooks, clamps or the like which may be brought in engagement with the heart tissue as the entire electrode support, or a part on which the fixation means are arranged, is controlled between the deformed shape and the preformed shape. Also, the fixation means have the ability to disengage the heart tissue, enabling repositioning of the pacing lead arrangement or explanation thereof. Clearly, repositioning is considerably easier in this manner than what has been possible with e.g. prior art sutured electrode supports. The fixation means comprise, according to at least one embodiment of the invention, a first hook (or clamp element or pinch element, etc.) which extends in a first direction and a second hook (or clamp element or pinch element, etc.) which extends in a second direction, the second direction being opposite to the first direction. When the configuration of the electrode support is changed as described above from the preformed to the deformed shape, the first and second hook becomes distanced from each other, thereby changing from said locking position to said release position. When the electrode support is allowed to recover its preformed shape, the hooks will approach each other and assume the locking position. The function of the electrode support with the fixation means can be compared to a gripping or grasping action. If hooks are used as fixation means they will suitably penetrate the heart tissue for providing fixation of the electrode support. However, fixation means that merely clamp the tissue, without penetrating it, is also conceivable. Furthermore, there may be more than just two fixation means as described above. For instance, if a an electrode support having the appearance of a waist area with two neighbouring end areas, the waist area may be provided with a fixation means projecting in one direction, while the end areas each have a fixation means projecting in the opposite direction.

Suitably, the hooks are arranged on a plane or planes being the same as or at least parallel to the main plane, i.e. the largest plane of extension of the electrode support. Preferably, in the case of two hooks being provided as described above, the first and second hooks are arranged at different locations along the geometrical longitudinal axis of the electrode support. This type of axial displacement of the hooks makes it easy to secure the electrode support to the heart tissue when the electrode support is deformed in said largest plane of extension. For, instance if the length of the electrode support comprises three consecutive areas together constituting the largest plane of extension, such as two wide end areas and a thinner waist area, first hooks may be arranged on the end area and extend in a first transverse direction while a second hook may be arranged on the waist area and extend in the opposite transverse direction.

The geometrical change between the preformed shape and the deformed shape of said portion of the electrode support is suitably enabled by means of a tool in accordance with a second aspect of the present invention.

The tool for the epicardial pacing lead arrangement comprises a movable actuator. The actuator is connectable to an electrode support (e.g. as previously described) which holds at least one electrode. The movable actuator has a direction of motion in the plane in which the electrode support has its largest plane of extension. The movable actuator is arrangeable to affect a fixation means holding portion of said electrode support in said direction of motion so as to cause a change, predominantly in said plane, between a preformed shape and a deformed shape of said portion of the electrode support. As a result of that change, a change between a locking position and a release position of the fixation means is obtained. Said portion of the electrode, when affected by the actuator in said direction of motion, may e.g. be subjected to bending, wherein said portion is suitably straight in its preformed shape and is bent by the tool to a deformed shape, such as J-shape, C- shape, or S-shape, or any other suitable shape. Alternatively the actuator of the tool may be so arranged as to compress said portion of the electrode, thereby obtaining a deformed and compressed shape. Similarly, the deformed actuator may cause said portion to be stretched to a deformed shape. If said direction of motion is an angular direction, the actuator may, as a further alternative, cause said piece of the electrode support to be at least partially turned around an axis thereof (or one area of said pieced turned around the axis in one direction and another area in the reversed direction), thereby obtaining a twisted and deformed shape. Such a twisting motion can in accordance with the invention be made in the main plane of the electrode support.

Thus, in all of the above examples, the movable actuator is adapted to affect the fixation means holding portion of the electrode support in order to merely indirectly affect the fixation means so as to achieve a fixation or release of the electrode support to or from the heart tissue. According to at least one embodiment of the invention said actuator comprises an actuator driving unit. The actuator driving unit is connectable either directly or indirectly to the actuator and is adapted to cause the actuator to move in its forward and backward (reverse) direction of motion. In case the actuator driving unit is indirectly comiected to the actuator, this could be e.g. via an arm. The driving unit may thus pull or push the arm so as to provide the motion of the actuator.

Suitably, the ami is provided with grooves with which the driving unit is engageable. The actuator driving unit may be in the form of a sprocket wheel having projections that come into engagement with the grooved arm, wherein the turning of the sprocket wheel causes the actuator to move forwards or backwards. The sprocket wheel is turnable by means of a rotatable axle which may be manipulated from outside the patients body.

Instead of a sprocket wheel, the actuator driving unit may comprise a straight moving wedge which pulls or pushes the grooved arm. Obviously, other alternatives are conceivable for obtaining the desired result.

According to at least one embodiment of the invention the tool comprises a tool housing. The tool housing has a geometrical axis parallel to the electrode support, which it is intended to control, said axis being perpendicular to the direction of motion of the actuator. The tool housing is suitably provided with at least one abutment, which is axially spaced from the actuator, for contacting the electrode support and preventing the area or areas of contact from being moved in the same direction of motion and simultaneously with the area of contact affected by the actuator. For instance, the actuator may affect an area of contact on one side of the actuator, while said abutment affects an area of contact on the other side. In case of a waist designed electrode support the actuator could be adapted to affect the waist area in its direction of motion, while the end areas of the electrode support are each contacted by an abutment keeping the end areas still, or alternatively, forcing the end areas in the reverse direction of motion. The actuator may comprise an arm as described above which may be pulled into or pushed out from the tool housing. When the arm is pulled into the tool housing the actuator will also force the waist area to be displaced in the same direction. As the abutments on the other side hold the end areas still a C-shaped deformation will occur in respect of the electrode support. The electrode support may be provided with cavities, and the abutments may be matching tongues. Also the actuator may comprise a tongue that matches with a cavity in the electrode support.

According to at least one embodiment of the invention, the epicardial pacing lead arrangement comprises a thoracoscopic or laparoscopic tube through which an electrode support connected to a distal end of a lead body, and a tool as described above, are guidable. The tool is suitably fitted to the electrode support before they assembled are introduced at the proximal end of the thoracoscopic tube and guided to exit through the distal end of the tube. After mapping, i.e., passing the electrode support along the heart wall in order to establish a location for the electrode support where good operational values are obtained, the electrode support is fixated at that location, by the following procedure. The tool is manipulated so as to deform the electrode support, and consequently bring the fixation means into the release position. Next, the tool is allowed to recover its preformed shape, either by itself or with the aid of the tool. This recovery causes the fixation means to assume the locking position, thereby fixating the electrode support to the tissue. If repositioning is desirable, the electrode support is once again deformed so as to release it, and after change of location it may be once more be fixated. Because of the possibility to keep the deformation in the main plane, e.g. in the x-,y-plane in an orthogonal x-,y, z- coordinate system, the repositioning can be made in close relationship with the heart tissue. In other words deformation in the z-direction may substantially be avoided.

When the electrode support has been fixated to the desired location of the epicardium, the tool may be released or disengaged from the from the electrode support and retracted towards and out through the proximal end of the thoracoscopic tube. Conversely, if a later repositioning is to be done, the tool may be advanced through the tube for reconnection to the electrode support.

The tool can be viewed as having three stages: a connected stage, a positioned stage and a released stage. In the connected stage the tool is merely connected to the electrode support, without affecting its shape. In the positioned stage the tool has been manipulated so that the electrode support is deformed. In the release stage the tool is disconnected from the electrode support. A tool according to the invention may be quite simple, with few moving parts. One and the same tool may be used during mapping and fixation.

When guiding the electrode support to the heart tissue, it may be desirable to be able to bend or change the angle of the guiding mechanism and the axle connected to the sprocket wheel, or any other elongate controlling means which is attached to the tool housing and which is manipulated from outside the patient's body by an operator. This may be particularly convenient if the heart tissue is accessed from below the sternum, wherein the arrangement with the tool and the electrode support is to be guided up to the heart and be bent up to an angle of 90°. This may be accomplished by means of a guiding mechanism which is attached to the housing and which includes two flexible elongate guiding elements contacting and extending in parallel with each other. The guiding elements are axially, i.e. proximally or distally, displaceable relative each other at least at a proximal portion thereof, i.e. near the operator. On the other hand, at a distal portion the guiding elements are fixed to and immovable relative each other. This means that when the operator pushes or pulls one of the guiding elements they can become bent. Suitably, a thin flexible tube is arranged around the guiding elements so as to prevent them from being radially separated.

The bending action may be accomplished with different types of elongate elements and the axle connected to the sprocket wheel is suitably flexible and is arranged to follow or conform with the bending or curving changes of the elongate elements. For instance, it may be provided adjacent and along one of the elements or on the flexible tube. However, according to at least one preferred embodiment, the two guiding elements are two pipe halves defining a hollow pipe through which axle extends. Furthermore, a tubular member may be arranged around the guiding elements or pipe halves. Such a tubular member serves to prevent those portion of the guiding elements that are enclosed by the tubular member from being bent. The tubular member is shorter than the guiding elements and therefore some portions will not be covered. Thus, by displacing the tubular member along the guiding elements, the bending radius of the distal portion of the guiding elements is controllable, both as regards position and size. A typical bending radius of 30 mm may be obtained.

From the above, it is clear that the tool has at least three main functions: (1) to bend the electrode support; (2) to bend the guiding elements (pipe including two pipe halves) for guiding the arrangement inside the body; (3) to adjust the bending radius.

Description of the drawings

Fig. 1 is a perspective view of a distal portion of an epicardial pacing lead arrangement according to one embodiment of the present invention.

Fig. 2 is another perspective view of the arrangement shown in Fig. 1. Fig. 3 is a plan view of the arrangement shown in Fig. 1.

Fig. 4 is an exploded view of the arrangement shown in Fig. 1. Fig. 5 is a plan view of an electrode support holding electrodes, the electrode support being shown in a deformed shape.

Fig. 6 is a perspective view of the electrode support in the deformed shape as in Fig. 5.

Fig. 7 is a perspective view of a tool according to one embodiment of the present invention attached to an electrode support. Fig. 8 is a perspective view of a tool according to one embodiment of the present invention detached from an electrode support.

Fig. 9 is a partly exploded view of the tool connected to an electrode support. Fig. 10 illustrates in a perspective view a control mechanism of the tool. Fig. 11 is en enlarged view of a portion of Fig. 10.

Description of preferred embodiments

With reference to Figs. 1-4, a distal portion of an epicardial pacing lead arrangement according to one embodiment of the invention is shown. The pacing lead arrangement comprises a tubular lead body 10 (shown stripped for the sake of clarity) in which two concentric coiled conductors 12,14 are arranged. The conductors are separated by means an insulation 16 around the inner conductor 12. The conductors 12,14 are at their distal ends connected to a respective electrode 18,20. The outer conductor 14 is connected to an anode 20, while the inner conductor 12 has a distal portion which extends past the anode 20 and is instead connected to a cathode 18 (see Fig. 4).

The electrodes 18,20 are housed in an elongate pad-shaped electrode support 22, e.g. having a length of 17 mm, a width of 5 mm and a thickness of 2.5 mm. The material of the electrode support 22 may suitably include silicone or some other flexible material. The electrode support 22 is on a tissue contacting side 24 provided with apertures through which the electrodes 18,20 are exposed and protrude. The electrodes 18,20 and the tissue contacting side 24 of the electrode support 22 are to be placed against the epicardium of a patients heart. The coiled conductors 12,14 enter the electrode support 22 through a proximal opening 26 thereof. The electrode support 22 comprises a proximal portion 28 and a distal portion

30. In between said portions 28,30, the electrode support 22 comprises a central waist portion 32. The lateral sides 34,36 of the waist portion 32 are concave, and suitably also the tissue contacting side 24 and the thereto opposite side of the waist portion 32 are also concave (see e.g. Fig. 2). In other words the waist portion 32 has a reduced dimension, compared to the proximal portion 28 and the distal portion 30, as regards thickness and transverse extension. In the longitudinal direction, i.e., the proximal-to- distal direction, it may be of any suitable length.

The electrode support 22 is provided with three locking hooks 40,42,44. The hooks 40,42,44 are arranged at the periphery of the electrode support. One of the hooks 44 is located on the waist portion 32 and projects upwards (see Fig. 2) from a lateral point (near lateral side 34) on the tissue contacting side 24 towards the central longitudinal axis of the electrode support 22. The other two hooks 40,42 are placed on the proximal portion 28 and the distal portion 30, respectively, of the electrode support 22. They too project from lateral points on the tissue contacting side 24 towards the central longitudinal axis. However, these lateral points are located on the other side of the central longitudinal axis (i.e. nearer to the lateral side 36). The hook 44 located on the waste portion 32 extends in a transverse direction and the longitudinally displaced other two hooks 40, 42 extend in a reversed transverse direction. The latter two hooks 40, 42 are located on a common plane, while the waste portion hook 44 is located on another and lower plane. However, both these planes are parallel to the plane in which the electrode support 22 is mainly deformable. The distal portion 30 of the electrode support 22 comprises an additional aperture 46 in which a steroid plug 48 is exposed. When the electrode support 22 is placed against the epicardium of the patient, the steroid will leak out from the plug 48 and serve as medication preventing or at least mitigating, inter alia, irritation of the tissue around the cathode 18. The electrode support 22 is also provided with three tool fixation cavities

50,52,54 for connecting a tool to the electrode support 22. Such a tool will be further described later in connection with Figs. 7-11. The tool fixation cavities 50,52,54 are located on the lateral sides of the electrode support 22 and are spaced along the longitudinal axis similarly to the fixation hooks 40,42,44. Thus, the proximal portion 28, the waist portion 32 and the distal portion 30 are each provided with a tool fixation cavity. Each tool fixation cavity is located on a lateral side being furthest spaced from the respective hook, i.e. on the other side of the longitudinal axis, or in other words, each hook 40,42,44 projects in a direction towards a tool fixation cavity 50, 52 and 54, respectively. Figs. 1-4 have all been drawn as illustrating the electrode support in the preformed shape. In the plan view of Fig. 3 the double arrow indicates how the electrode support, having the shown placement of hooks, is suitably bent to obtain a deformed shape. As indicated, the bending takes place in the main plane of the electrode support. Turning now to the plan view in Fig. 5 and the corresponding perspective view in Fig. 6, an electrode support of the previous kind is shown schematically in a deformed shape, The same reference numerals are used for elements corresponding to those shown in Figs. 1-4.

The electrode support 22 has been curved in the plane the electrode support, i.e. in the plane of the paper on which Fig. 5 is drawn. This curving or bending towards a C-shape may be accomplished by keeping the proximal portion 28 and the distal portion 30 of the electrode support 22 fixed in space, while the waist portion 32 is laterally displaced. The hooks 40,42,44 are more distanced from each other in this deformed shape than in the preformed shape. As the electrode pad 22 is returned to its preformed shape the hooks 40,42,44 will come closer to each other, similar to a griping action. The hooks 40,42,44 may be regarded as being in an inactive state when the electrode support 22 has the deformed shape, and being in an active state when the electrode support has the preformed shape.

Instead of the placement of hooks 40,42,44 as shown in Figs. 1-6, many alternatives are possible. The three-hook arrangement provides good stability and prevents the electrode support from rotating when fixated to the heart tissue.

With reference to Figs. 7-9, a tool 60 according to one embodiment of the present invention is illustrated. Furthermore, in this Figures an electrode support 22 is also illustrated, however, for the sake of clarity the lead body comprising the coiled conductors has been omitted. The tool 60 comprises an elongate housing 62 having an upper side 64, an electrode support facing lower side 66 and two elongate lateral sides 68,70. Three legs 72,74,76 project from the lateral sides 68,70 downwards past the lower side 66. Each leg 72,74,76 is at its lower end provide with attachment or abutment means in the form of a transverse protrusion 78, 80 and 82, respectively, extending towards the central longitudinal axis of the elongate housing 62. Two of the legs 72,74 are integrated with the housing 62 and are located at the same lateral side 68, one leg 72 being at the distal end and the other leg 74 at the proximal end of said lateral side 68 of the housing 62. The third leg 76 is located centrally on the other lateral side 70 and is a perpendicular elongation of a ribbed or grooved arm 84 (see Figs. 7 and 9). The protrusion 78,80,82 of the legs are arranged to fit into tool fixation cavities 50, 52 and 54, respectively, of the electrode support 22.

The grooved arm 84 is movable forwards an backwards in the transverse direction of the housing 62, i.e. from one lateral side towards the other. The housing

62 is provided with a transverse through hole 86, in which the movable grooved arm 84 is displaceable. The grooved arm 84 is brought in motion by means of a rotating toothed wheel or sprocket wheel 88 (see Fig. 9). The ridges of the sprocket wheel 88 mate with the grooves between the ridges of the grooved arm 84, wherein rotation of the sprocket wheel 88 causes a transverse motion of the grooved arm 84.

The sprocket wheel 88 is attached to a distal portion of an axle 90 which is introduced through an opening 92 in the proximal end face of the housing and which extends through an adjustable tube, which will be described in more detail in connection with Figs. 10 and 11. As the axel 90 is rotated, and consequently also the sprocket wheel 88, anticlockwise according to Fig. 9, the grooved arm 84 will move so that the third leg protrusion 82, which is inserted in the tool fixation cavity 54 at the waist portion of the electrode support 22, will affect the waist portion with a force towards the other lateral side 68. At the same time, the two other protrusions 78,80 being inserted in the cavities 50,52 at the proximal portion and the distal portion, respectively, of the electrode support 22 keep these portions from being transversely displaces. Thus, since only the waist portion is allowed to be displaced relative to the tool housing 62, the electrode support 22 will become bent and somewhat C-shaped, as previously shown in Figs. 5 and 6. This maneuver may be performed when, after mapping, a suitable tissue location has been found at which the electrode support 22 is to be locked to the tissue. Alternatively, the electrode support may already be in the deformed C-shape during mapping. Subsequently, the operator rotates the axle 90 the other way in order to bring the electrode support back to its preformed shape, causing the projecting hooks to engage with the tissue. The tool 60 may be detached from the electrode support 22 and retrieved through a thoracoscopic introducer, which is suitably also used for introducing the pacing lead arrangement into the patient. For later explantation or repositioning, the tool may be introduced again and be connected to the electrode support, deformation thereof causing the hooks to release the tissue.

Fig. 10 illustrates in a perspective view a guiding or control mechanism of the tool. Fig. 11 is en enlarged view of a portion of Fig. 10. As seen best in Fig. 11, the rotatable axle 90 connected to the sprocket wheel 88 exits through a flexible pipe 100 which comprises two pipe halves 102,104. Also, at the proximal end (see Fig. 10) the axle 90 extends past or out from the pipe 100. At the proximal end, each pipe half 102,104 is connected to a half-moon shaped element 106 and 108, respectively. A tubular member 110 encloses the pipe halves 102,104.

The pipe halves 102,104 are fixed to each other at their distal portion or distal end, i.e. nearest the sprocket wheel 88, and are therefore at that portion immovable in relation to each other. The remaining portion of the pipe halves are axially, i.e. distally or proximally, displaceable with respect to one another. A thin, flexible tube (not shown) is arranged around the pipe halves 102,104 for keeping them together and preventing them from being separated. One of the half-moon shaped elements 106 is threaded. An operator handle including a threaded nut (not shown) is fitted to the threaded element 106. As the operator causes the nut of the handle to turn it will make the threaded half-moon shaped element 106 to move axially forwards (or optionally backwards) in relation to the other half-moon shaped element 108. Accordingly, the pipe half 102 connected to threaded half-moon shaped element 106 will be displaced relative to the other pipe half 104, and since they are fixed to each other at their distal portion, the pipe halves 102,104 will become bent and obtain an angle (up to 90°) as illustrated in Fig. 10. The previously mentioned tubular member 110 controls how large portion of the pipe halves 102,104 that are to be bent. If the tubular member 110 is displaced distally, a smaller portion will be bendable.

Thus, an operator may manipulate the pipe halves 102,104 in order to bend the assembly and facilitate guiding past curved passages in the body of the patient. The bending radius is controlled by manipulating the position of the enclosing tubular member 110 and the threaded half-moon shaped element 106. The change between the preformed and deformed shape of the electrode support, when having been guided to the desired location at the heart, is controlled by turning the rotatable axle 90. Even though the drawings show a specific design of a tool and an electrode support other alternatives are also possible. For instance, the hooks may be arranged on an electrode support part being deformable while another part actually holding the electrodes is not deformable. Also, other types of deformation than bending is possible, such as compression or twisting. Instead of hooks other fastening means may be provided. Furthermore, pacing lead may be unipolar with a single electrode. Another variant is to allow the fixation means to act as electrodes. Likewise, the tool may be designed in different ways for providing the desired effect. For instance, the grooved arm and its integrated leg with the protrusion may be replaced by some other type of actuator. Furthermore, instead of tool fixation cavities and protrusions other types of areas of contact may be provided on booth the tool and the electrode support. Thus, in this patent application any technical design is accounted for that provides an electrode support comprising a fixation means holder portion which is predominantly deformable in the largest plane of extension of the electrode support, and which is controllable between a preformed shape and a deformed shape for causing a change between a locking position and a release position of the fixation means, and that provides a tool for such control.

Claims

1. An epicardial pacing lead arrangement, comprising a lead body (10) having a proximal end and a distal end; an electrode support (22) which is coupled to said distal end and which holds at least one electrode (18, 20) for carrying electrical signals to or from cardiac tissue; fixation means (40, 42, 44) arranged on a portion of the electrode support for fixating it to the cardiac tissue, wherein said portion of the electrode support is controllable between a preformed shape and a deformed shape for causing a change between a locking position and a release position of the fixation means; c h r a c t e r i z e d in that said portion of the electrode support is deformable predominantly in a plane in which the electrode support has its largest plane of extension.

2. The epicardial pacing lead arrangement as claimed in claim 1, wherein said portion of the electrode support is resilient and bendable in at least one bending direction, said portion preferably being in the from of a flat pad.

3. The epicardial pacing lead arrangement as claimed in claim 1 or 2, wherein said portion essentially constitutes the electrode support, wherein the electrode support per se is controllable between a preformed shape and a deformed shape.

4. The epicardial pacing lead arrangement as claimed in claim 3, wherein the electrode support is in the form of a housing comprising an electrode aperture through which the electrode is exposed, the fixation means protruding from the housing, such as from the housing surface (24).

5. The epicardial pacing lead arrangement as claimed in claim 2 or any one of claims 3-4 in combination with claim 2, wherein said portion of the electrode support comprises an area (32) having a smaller extension in the bending direction than neighbouring areas (28, 30) of said portion of the electrode support.

6. The epicardial pacing lead arrangement as claimed in claim 5, wherein said area having a smaller extension is a waist area (32) which is located adjacent two end areas (28, 30), one on each side of the waist area, wherein said preformed shape is generally straight and said deformed shape is a C-shape.

7. The epicardial pacing lead arrangement as claimed in claim 6, wherein the pacing lead is a bipolar pacing lead, a cathode (18) being arranged in one of said end areas (30) and an anode (20) being arranged in the other one of said end areas (28).

8. The epicardial pacing lead arrangement as claimed in claim 7, wherein a steroid plug (48) is provided in the same area as the cathode for leaking steroid to the tissue contacted by the cathode so as to mitigate any adverse effects, such as irritation of the tissue.

9. The epicardial pacing lead arrangement as claimed in any one of claims 1-8, wherein said fixation means comprises at least a first hook extending in a first direction and at least a second hook extending in a second direction being opposite to said first direction, said first and second hook becoming distanced from each other when changing from said locking position to said release position.

10. The epicardial pacing lead arrangement as claimed in claim 9, wherein said portion of the electrode support has a geometrical longitudinal axis, wherein said first and second hooks are arranged at different locations along said longitudinal axis.

11. The epicardial pacing lead arrangement as claimed in any one of claims 1 -

10, further comprising a tool (60) which includes a movable actuator (76, 82, 84) connectable to the electrode support for providing a bending of said portion of the electrode support in a direction of motion of the movable actuator, thereby enabling a change between the preformed shape and the deformed shape of said portion of the electrode support.

12. The epicardial pacing lead arrangement as claimed in claim 11, wherein the tool comprises a sprocket wheel (88) which is engageable with a grooved arm (84) of said movable actuator such that the turning of the sprocket wheel causes the actuator to move in its forward and backward direction of motion.

13. The epicardial pacing lead arrangement as claimed in claim 12, wherein the tool comprises a tool housing (62) having a geometrical axis parallel to the electrode support and perpendicular to said direction of motion of the actuator, the tool housing being provided with at least one abutment (78, 80), axially spaced from said actuator, for contacting the electrode support and preventing the area or areas of contact (50, 52) from being moved in the same direction of motion as and simultaneously with the area of contact (54) affected by the actuator.

14. The epicardial pacing lead arrangement as claimed in any one of claims 11-13, further comprising a thoracoscopic tube through which the tool and the electrode support with its lead body are guidable, the tool being releasable from the electrode support for proximal retraction through the thoracoscopic tube and also being distally advanceable through the thoracoscopic tube for re-connection to the electrode support.

15. A tool (60) for an epicardial pacing lead arrangement, comprising a movable actuator (76, 82, 84) which is connectable to an electrode support (22) that holds at least one electrode (18, 20) for carrying electrical signals to or from cardiac tissue, said movable actuator having a direction of motion in a plane in which the electrode support has its largest plane of extension and being arrangeable to affect a fixation means holding portion of said electrode support in said direction of motion so as to cause a change, predominantly in said plane, between a preformed shape and a deformed shape of said portion of the electrode support, and as a result thereof, a change between a locking position and a release position of fixation means (40, 42, 44) provided in said portion of the electrode support.

16. The tool as claimed in claim 15, further comprising a sprocket wheel (88) which is engageable with a grooved arm (84) of said movable actuator such that the turning of the sprocket wheel causes the actuator to move in its forward and baclcward direction of motion.

17. The tool as claimed in claim 16, wherein the tool comprises a tool housing (62) having a geometrical axis parallel to the electrode support and perpendicular to said direction of motion of the actuator, the tool housing being provided with at least one abutment (78, 80), axially spaced from said actuator, for contacting the electrode support and preventing the area or areas of contact (50, 52) from being moved in the same direction of motion as and simultaneously with the area of contact (54) affected by the actuator.

18. The tool as claimed in claim 17, further comprising a guiding mechanism which is attached to the housing and which includes two flexible elongate guiding elements (102, 104) contacting and extending in parallel with each other, said guiding elements being axially displaceable relative each other at least at a proximal portion thereof, but at a distal portion they are fixed to and immovable relative each other, thereby enabling a bending motion of the guiding elements.

19. The tool as claimed in claim 18, wherein said guiding mechanism further comprises a tubular member (110) enclosing and extending in parallel with, but being shorter than, the guiding elements, said tubular member being axially, i.e. distally and proximally, displaceable, thereby enabling control of the bending radius of the guiding elements.

20. The tool as claimed in claim 18 or 19, wherein said two guiding elements are two pipe halves (102, 104) defining a hollow pipe (100) through which a rotatable axle (90) extends, said axle being, at a distal portion, connected to the sprocket wheel, wherein rotation of the axle causes rotation of the sprocket wheel.