Abstract:
A medical device and a method for providing a change of shape in a part of the body of an organism. The device is insertable into the body of the organism and comprises a member having a preferred state of shape and having a tendency to transfer its shape towards said preferred state of shape when being in a non-preferred state of shape. The device further comprises a resorbable means which is arranged to hold the member in the non-preferred state of shape and to delay the transfer when the device is inserted into the body of the organism by counteracting said transfer during resorption of the resorbable means by the surrounding body of the organism.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    The present invention relates to a medical device for providing a change of shape in a part of the body of an organism. The invention further relates to a device and a method for reshaping a body vessel, and a device and a method for restraining growth of a body organ of an organism.  
         BACKGROUND OF THE INVENTION  
         [0002]    At present the treatment of mitral annulus dilatation and other mitral insufficiencies consists of either repair or mitral valve replacements. Both methods require open-heart surgery, by the use of total cardiopulmonary by-pass, aortic cross-clamping and cardioplegic arrest. To certain groups of patients, open-heart surgery is particularly hazardous and therefore a less invasive method for repair of mitral insufficiency is desired.  
           [0003]    Such a less invasive method is proposed in U.S. Pat. No. 6,210,432, which describes a method for treatment of mitral insufficiency without the need for cardiopulmonary by-pass and opening of the chest and heart. The method uses a device comprising an elongate body having such dimensions as to be insertable into the coronary sinus, which is a vein that substantially encircles the mitral orifice and annulus and drains blood from the myocardium to the right atrium. The elongate body has two states, in a first of which the elongate body has a shape that is adaptable to the shape of the coronary sinus, and to the second of which the elongate body is transferable from said first state assuming a reduced radius of curvature. Consequently, the radius of curvature of the coronary sinus is reduced. Due to the coronary sinus encircling the mitral annulus, the radius of curvature as well as the circumference of the mitral annulus are reduced. Thus, the described method takes advantage of the position of the coronary sinus being close to the mitral annulus, which makes repair possible by the use of current catheter-guided techniques.  
           [0004]    According to one method described in U.S. Pat. No. 6,210,432, a device comprising an elongate stent is used. The elongate stent includes hooks which are arranged to dig into the walls of the coronary sinus, by means of the surgeon retracting a cover sheet from the stent, in order to fix the position of the stent in the coronary sinus. A stabilizing instrument is used for keeping the elongate stent in its first state and then, after the hooks have dug into the walls, releasing it to its second state assuming a reduced radius of curvature. However, the position fixation of the elongate stent in the coronary sinus by means of the hooks might be insufficient, so that the sudden release of the contraction of the elongate stent dislocates it. This dislocation of the device might result in unsatisfactory reduction of the circumference of the mitral annulus.  
           [0005]    According to an alternative method described in U.S. Pat. No. 6,210,432 the device comprises three stent sections that are positioned in the coronary sinus and connected by wires. The wires may be manoeuvred from outside the vein system such that the distances between the adjacent stent sections are reduced. Also with this method there is a risk of dislocation of the device, since the surgeon might accidentally move insufficiently fixed stent sections out of their proper position while manipulating them from outside the vein system.  
         SUMMARY OF THE INVENTION  
         [0006]    An object of the present invention is to provide a more secure fixation of a medical device for providing a change of shape in a part of the body of an organism.  
           [0007]    A particular object of the invention is to provide a more secure fixation of a device for reshaping a body vessel, as described above.  
           [0008]    These and other objects are achieved by a device as defined in any one of claims 1, 17, 26, and 31 and by a method as defined in claim 42.  
           [0009]    More particularly, according to one aspect of the present invention, a medical device being insertable into the body of an organism comprises a member having a preferred state of shape, towards which the member by means of inherent forces strives when being in a non-preferred state of shape, and a delay means having a weakenable inherent stiffness to hold the member in the non-preferred state of shape for a period of time after the device is inserted into the body of the organism. The member is by means of said inherent forces arranged to provide a change of shape in a part of the body of an organism, whereas the delay means is arranged to delay the change of shape for a period of time. The time period is determined by how fast the weakening of said inherent stiffness proceeds. By delaying the change of shape this way, the device is allowed to heal on to body tissue of the organism before a change of shape of the device occurs. Which parts of the device that become fixed by the healing process can be determined by means of the design of the device. The normal healing process that occurs in every living organism is thus allowed to provide a well-established fixation of the device. Hence, the present invention provides a more secure fixation of a medical device for providing a change of shape in a part of the body of an organism.  
           [0010]    In a preferred embodiment of the invention, said delay means holds said member in a non-preferred state of shape by counteracting the inherent forces of the member. Thus, the delay means is arranged to apply force to the member by means of the inherent stiffness, in order to counteract the inherent shape-changing forces of the member and thereby restrain the member from changing its shape.  
           [0011]    Preferably, said delay means holds said member in a non-preferred state of shape while the inherent stiffness of the delay means overcomes the inherent forces of the member. That is, there is an equilibrium between the inherent forces of the member and the inherent stiffness of the delay means, and when the stiffness of the delay means no longer is strong enough to balance the inherent forces of the member, the change of shape will occur.  
           [0012]    In another preferred embodiment of the invention, said delay means comprises a decomposable material. In this way, the inherent stiffness of the delay means is allowed to weaken simply as a result of the decomposable material of the delay means being decomposed.  
           [0013]    Preferably, said delay means comprises a resorbable material. A resorbable material is a material that when it is inserted into the body of an organism, it will be resorbed by the body by means of enzymatic processes, by active absorption by the cells in the blood and tissue cells of the body, and/or by hydrolysis. Thus, the resorbable material of the delay means will advantageously be decomposed and vanish from the device by time, without leaving any major waste products in the body.  
           [0014]    In another preferred embodiment, said member comprises an elastic material. An elastic material can in a simple way be forced to adopt a non-preferred shape.  
           [0015]    In yet another preferred embodiment, said member comprises a material having superelasticity properties. Superelasticity properties means that the material may be deformed and in the deformed state the material will use its superelasticity forces to return to its preferred shape. These superelasticity forces thus constitute advantageously at least part of said inherent forces providing said strive towards said preferred state of shape of the member.  
           [0016]    Preferably, said member comprises a shape memory material. A shape memory material is a material that has two different forms, one at lower temperatures and another at higher temperatures. At the lower temperatures, e.g. below 30° C., the material is elastic and may be introduced into the body. At the higher temperatures, the material is still elastic but becomes also superelastic and assumes its preferred original shape unless the transformation to this original shape is obstructed by external stress to the material. The use of a shape memory material in the member is advantageous inter alia because then one can easily provide the device with said delay means while the member, at a lower temperature outside the body, more easily remains in a shape corresponding to said non-preferred state of shape inside the body.  
           [0017]    According to another aspect of the present invention, a medical device for providing a change of shape in a part of the body of an organism comprises a first set of forces working towards a change of shape of the device, and a second set of forces working for preserving a present shape of the device and thereby counteracting said first set of forces. Said first and said second sets of forces are each inherent in a solid material of the device, and the forces of said second set of forces are arranged to decrease as a result of said solid material interacting chemically with said part of the body. As a result of the chemical interaction between the solid material of the device and the surrounding body, the forces of the second set of forces decrease and thus allow the device to provide said change of shape after a while, when parts of the device have become fixed in the body by a healing process. An advantage of the present invention, except that it provides a more secure fixation, is that there is no need for a stabilizing surgical instrument for keeping a present shape of the device during operation, since the shape is preserved by means of said second set of forces being inherent in the device itself.  
           [0018]    Preferably said second set of forces is inherent in a decomposable material as mentioned above.  
           [0019]    Said forces of said second set of forces are preferably arranged to decrease as a result of said solid material being decomposed by said part of the body.  
           [0020]    In a preferred embodiment of the invention, said second set of forces is inherent in a resorbable material as described above.  
           [0021]    Preferably, said forces of said second set of forces are arranged to decrease as a result of said solid material being resorbed by said part of the body.  
           [0022]    In another preferred embodiment, said first set of forces is inherent in an elastic material.  
           [0023]    Preferably, said first set of forces is inherent in a material having superelasticity properties as described above.  
           [0024]    Said first set of forces is preferably inherent in a shape memory material as also described above.  
           [0025]    In one embodiment of the invention, said first set of forces is inherent in a shape memory metal.  
           [0026]    In an alternative embodiment of the invention, said first set of forces is inherent in a shape memory polymer.  
           [0027]    The device is in one embodiment arranged to contract into a new shape as a result of said second set of forces being decreased.  
           [0028]    In an alternative embodiment, the device is arranged to expand into a new shape as a result of said second set of forces being decreased.  
           [0029]    The device could be arranged to change its shape in one dimension only, but it could also be arranged to change its shape in two dimensions, or even in three dimensions.  
           [0030]    According to yet another aspect of the present invention, a medical device being insertable into the body of an organism comprises a member having a preferred state of shape and having a tendency to transfer its shape towards said preferred state of shape when being in a non-preferred state of shape. The device further comprises a resorbable means being arranged to hold the member in the non-preferred state of shape and to delay the transfer when the device is inserted into the body of the organism by counteracting said transfer during resorption of the resorbable means by the surrounding body of the organism. The resorption of the resorbable means by the surrounding body makes the resorbable means gradually vanish. Thus, after some period of time when parts of the device have grown on to body tissue, there is nothing left to hold the member in the non-preferred state of shape, whereby said transfer is released.  
           [0031]    Also according to this aspect of the invention, said member preferably comprises an elastic material.  
           [0032]    Preferably, said member comprises a material having superelasticity properties.  
           [0033]    It is also preferred that said member comprises a shape memory material.  
           [0034]    According to a particular aspect of the present invention, a device for reshaping a body vessel is elongate and has such dimensions as to be insertable into the vessel and has two states, in a first of which the device has a shape that is adaptable to the shape of the vessel, and to the second of which the device is transferable from said first state. The device further comprises a fixing means for fixing the ends of the device within the vessel, when the device is first positioned therein, a member for transferring the device to the second state by reshaping it, and a resorbable means for delaying said reshaping until the ends of the device are fixed by keeping said device in said first state until the resorbable means is resorbed. By allowing the ends of the device to heal on to the walls of the vessel, e.g. the coronary sinus, by means of said fixing means, before said reshaping of the device occurs, the present invention provides a more secure fixation of a device for reshaping a body vessel.  
           [0035]    Preferably, said resorbable means comprises a resorbable sheath being arranged to enclose said member. This is advantageous since with the shape of a sheath the resorbable means is both easy to manufacture and easy to arrange on the member.  
           [0036]    In another preferred embodiment of the invention, said fixing means is arranged to expand against the wall of the vessel when first positioned therein. This expansion against the wall of the vessel initiates and contributes to the fixing of the ends of the device, thus enabling a rigid fixing.  
           [0037]    In yet another preferred embodiment of the invention, said fixing means is arranged to grow into the wall of the vessel. By taking advantage of the healing process in the tissue of the vessel wall, the fixing means can be fixed effectively. This can be facilitated by an expansion against the wall of the vessel as mentioned above.  
           [0038]    In a preferred embodiment, said fixing means comprises a self-expandable stent at each end of the device.  
           [0039]    According to another preferred embodiment, said member comprises a shape memory material providing said reshaping of the device.  
           [0040]    Preferably, said reshaping of said device comprises shortening of said device.  
           [0041]    In another preferred embodiment, said device is used for treatment of mitral annulus dilatation. Since the device can be inserted into a body vessel using catheter-guided techniques, the use of this device for treatment of mitral annulus dilatation is advantageous compared to open-heart surgery, which is the present procedure for repairing or replacing the mitral valve.  
           [0042]    In yet another preferred embodiment, said vessel is the coronary sinus. The coronary sinus encircles the mitral orifice and annulus. Therefore, a reshaping of this vein also has a compressing effect on the mitral annulus.  
           [0043]    Preferably, said reshaping of said device is used for reducing the radius of curvature of the coronary sinus. Hence, the radius of curvature as well as the circumference of the mitral annulus are also reduced. According to the invention, a method for reshaping a body vessel comprises the steps of inserting a device into the vessel, fixing the ends of the device within the vessel, reshaping the device, and delaying said reshaping by a resorbable means so that the step of fixing the ends of the device is performed before the step of reshaping the device.  
           [0044]    According to a preferred embodiment, said step of fixing the ends of the device comprises providing a growth of the ends into the wall of the vessel.  
           [0045]    According to another preferred embodiment, a shape memory material is used in the device for said step of reshaping the device.  
           [0046]    Preferably, Nitinol is used in the device for said step of reshaping the device.  
           [0047]    In a preferred embodiment, said step of reshaping the device comprises the step of shortening the device.  
           [0048]    In another preferred embodiment, the method is used for treatment of mitral annulus dilatation.  
           [0049]    In yet another preferred embodiment, said device is inserted into the coronary sinus in the vicinity of the posterior leaflet of the mitral valve.  
           [0050]    Preferably, said reshaping is used for reducing the curvature of the coronary sinus and thereby reducing the radius of circumference of the mitral valve annulus.  
           [0051]    The basic inventive idea, that reshaping of an implantable device may be delayed by means of a delay means being comprised in the device itself, opens up for new possibilities within many medical applications.  
           [0052]    The present invention could be used for instance when a delayed expansion of a stent is desired. The stent could then preferably be crimped to a small diameter by means of a resorbable suture or, alternatively, a resorbable film. The film or thread would slowly be eaten away and the shape-changing forces may be released after the desired delay which is programmed in the properties of the resorbable restraining material. Such a stent might be used inside vessels, the trachea, the biliary tract or any other hollow structure in the human or animal body.  
           [0053]    The invention would also be useful where openings of human, or animal, organs or other structures need to be opened or closed slowly. For instance, when an opening between the left and right side of the heart is present, an immediate closure of the opening could be dangerous, whereas a slower closure would be tolerated.  
           [0054]    Within many medical areas, the present invention would be useful when a continuous long-term effect of shape-changing forces is desired. One such application would be a device designed to shorten or lengthen a human or animal structure in one or more dimensions. The device according to the invention would then have time to heal into the body structure before shape-changing forces are released and force the body structure to slowly change its shape.  
           [0055]    This could for example be useful in the area of orthopaedics for lengthening of a bone structure.  
           [0056]    For orthodontic treatment, the described invention would be useful when it comes to tooth-regulation and lengthening of the maxilla and/or mandibula, i.e. the upper and lower jaws.  
           [0057]    In plastic surgery an extra growth of skin area is often used to cover skin defects. Using the present invention a slow growth of skin area would be augmented.  
           [0058]    An example within the area of urology surgery is lengthening of a penis. In this case a device made of three segments could be designed, where the distal ends of the device first are allowed to grow into the tissue. After fixation of the two ends of the device in the penis tissue, the mid portion which temporarily has been restrained by means of a resorbable material as described above will be released and the mid portion of the device will grow in length. One specific capacity of a human or animal body is to allow slow deformation of organs or tissues by compensatory tissue adaptation. A penis would therefore grow slowly to a predetermined length.  
           [0059]    By means of the present invention, a sequential effect of shape-changing forces could also be provided, i.e. change of shape could occur in two or several steps as a result of resorbable material releasing the shape-changing forces in predetermined steps. In each step, a part or parts of a device could first heal into a body structure and secondly the desired shape-changing effects could be released.  
           [0060]    As seen from the examples above, a substantial advantage of the present invention is that a change of shape is allowed to be made slowly so that body tissues have time to adapt.  
           [0061]    Other medical applications of particular interest, which could be improved by using the present invention, are treatment of pathological heart growth and treatment of pathological alveolar sac growth. Some background of these two diseases will be given next.  
           [0062]    Dilated cardiomyopathy (DCM) and ischemic heart disease (IHD) are common reasons for heart failure (HF). Heart failure in its terminal status is a deadly disease, and it is by far the most common cause of death in most countries, developed and undeveloped. Progressive HF, when it is deteriorating, results in a growth in the diameters of the heart ventricles, thus resulting in a general heart growth. The growth in heart size by dilatation initiated by myocardial pathology creates itself by its increase in heart diameter a pathology of its own, in the way of functional disorders.  
           [0063]    Dr. Randas Batista implemented a surgical treatment for this disease by resecting big parts of the left ventricle (LV) with or without repair of the mitral valve. The long time results were, however, dismal since the LV tends to dilate again a second time despite of having been reduced in size by surgery (see Kawaguchi, A. T. et al. “Mitral Regurgitation Redilates the Left Ventricle After Partial Left Ventriculectomy (Batista Operation).” Journal of the American College of Cardiology, February 1998, Vol.31, No.2, Suppl.A, page 376A, ISSN: 0735-1097; see also Kawaguchi, A. T. et al. “Intraoperative Left Ventricular Pressure-Volume Relationship in Patients Undergoing Left Ventricular Diameter Reduction.” Circulation, 1997, Vol.96, No.8, Suppl., page 1198, ISSN: 0009-7322; and Pérez de la Sota, E. et al. “Early Results with Partial Left Ventriculectomy (the Batista Operation).” Revista Espanola de Cardiologia, August 2000, Vol.53, No.8, pages 1022-1027, ISSN: 0300-8932).  
           [0064]    Supporting the LV and preventing progressive LV dilatation in HF actively by means of wrapping the heart with living skeletal muscle from the back of the patient, stimulated by pacemaker, was introduced by Dr. Carpentier in the eighties (Chachques, J. C. et al. “Dynamic Cardiomyoplasty: clinical follow-up at 12 years.” European Journal of Cardio-Thoracic Surgery: Official Journal of the European Association for Cardio-Thoracic Surgery, October 1997, Vol.12, No.4, pages 560-568, ISSN: 1010-7940). The method has been rarely used and its effectiveness has been questioned.  
           [0065]    More recently, methods of restraining the heart from growing have been introduced by Acorn Cardiovascular, Inc, St. Paul, Minn., USA. They are supporting the heart by means of a polyester mesh sutured to the surface of the heart after exposing the heart by splitting the sternum and opening the pericardium.  
           [0066]    Even reducing the LV diameter by force, using wires that transverse the LV cavity and subsequent fixation, has been introduced by Myocor, Maple Grove, Minn. 55311, USA.  
           [0067]    Chronic obstructive pulmonary disease (COPD) is an umbrella term used to describe airflow obstruction that is associated mainly with emphysema and chronic bronchitis. COPD is the fourth leading cause of death in the U.S. in 1998, according to the National Center for Health Statistics, Report of Final Morbidity Statistics, 1998. Emphysema causes irreversible lung damage by weakening and breaking the air sacs within the lungs. Further, sick air sacs sometimes grow unrestrainedly and repress smaller air sacs, resulting in lack of oxygen and by time death. This disease is hard to treat. At present, surgical treatment of dilated air sacs involves cutting them away, but this treatment gives no long-term effect since a new air sac will soon start to grow.  
           [0068]    All these known methods for treatment of pathological heart growth and said known method for treatment of alveolar sac growth require, whether they are effective or not, major heart or lung surgery which, as mentioned before, is particularly hazardous to certain groups of patients. Therefore less invasive methods for treatment of pathological heart growth and alveolar sac growth are desired as well.  
           [0069]    It is an object of the present invention to also provide less invasive treatments of pathological growth of body organs, by which treatments more long-term effects can be achieved.  
           [0070]    A particular object of the invention is to provide less invasive treatments of pathological heart growth and alveolar sac growth.  
           [0071]    These further objects are achieved by a device as defined in claim 50 and by a method as defined in claim 53.  
           [0072]    More particularly, according to a further aspect of the present invention, a device for restraining growth of a body organ of an organism is implantable into the body of the organism and comprises an elastic contractable member being arranged to enclose said body organ, and a resorbable means being arranged to delay contraction of the contractable member when the device is implanted in the body of the organism by counteracting the contraction during resorption of the resorbable means by the surrounding body of the organism.  
           [0073]    A basic advantage of the device according to the invention is that the device, since said contractable member is elastic, can be inserted into the body using catheter-guided techniques. Hence, less invasive treatments can be provided.  
           [0074]    Another advantage, which comes both from the elasticity and the delayed contraction, is that the device can be inserted by means of catheter-guided techniques even if said contractable member comprises a large area. This is due to the fact that the substantially elastic device at the insertion can be rolled up on a catheter and then be unfolded to enclose said organ.  
           [0075]    After a period of time after the surgical or percutaneous insertion, the device will start to contract as a result of the resorbable means being resorbed. The contraction will then make the device enclose the organ tight and apply a restraining force which holds back the growth of the organ. Since the implanted device applies a continuous restraining force to the organ, more long-term effects can be achieved in treatment of growing body organs. It is to be noted that if the contraction of the device would not have been delayed, it would have been very difficult to roll up the device on a catheter and then unfold it round the organ.  
           [0076]    Preferably, said contractable member comprises a shape memory material.  
           [0077]    According to the invention, a method for restraining growth of a body organ of an organism comprises the steps of inserting a restraining device into the body of the organism, enclosing at least partly the body organ with the restraining device, compressing said restraining device by means of a contractable member of said restraining device, and delaying said compression by a resorbable means.  
           [0078]    This inventive method could be used not only for treatment of pathological heart growth and alveolar sac growth, but also for treatment of bullous emphysema and for treatment of other body organs growing pathologically.  
           [0079]    A device according to the present invention may be fixed in body tissue by other means in combination with or instead of the healing process allowed by the delaying of the change of shape. Hence, fixing of a device according to the invention may as well be accomplished for example by means of suturing, gluing, clipping or using hooks. These means of fixation would permit a better healing in of the device in the tissue and also prohibit dislocation while healing in.  
           [0080]    As already seen, the number of advantages of the inventive device is large, of which a few are mentioned next. The present invention allows:  
           [0081]    1. less invasive surgical treatments;  
           [0082]    2. devices that are properly fixed inside the body by means of parts healing into the body tissue;  
           [0083]    3. devices to be designed that have multiple purposes;  
           [0084]    4. eliminating stabilizing surgical instruments for keeping a present shape of the device during operation;  
           [0085]    5. engineering to decide when a shape-changing action by the device is to take place in the body;  
           [0086]    6. a change of shape to be made slowly so that body tissue has time to adapt.  
           [0087]    It should be understood that many modifications are possible within the spirit and scope of the invention, which is only limited by the appended claims. A few applications of the invention are mentioned above, of which some will be further described by way of illustration only in the detailed description. However, many other medical areas where the invention might be used will become apparent to those skilled in the art. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0088]    The invention will now be described in more detail with reference to the accompanying drawings, in which  
         [0089]    FIGS.  1 - 4  are schematic views of the structure and the operation of an embodiment of a device according to the invention, illustrating the principle of delayed shortening;  
         [0090]    FIGS.  5 - 8  are schematic views of the structure and the operation of another embodiment of a device according to the invention, illustrating the principle of delayed elongation;  
         [0091]    [0091]FIG. 9 is a schematic view of another embodiment of a device according to the invention being an alternative to the embodiment shown in FIG. 7;  
         [0092]    [0092]FIGS. 10 and 11 schematically illustrate another embodiment of a device according to the invention, shown in a first state and a second shortened state, respectively;  
         [0093]    [0093]FIGS. 12 and 13 schematically illustrate another embodiment of a device according to the invention, shown in a first state and a second elongated state, respectively;  
         [0094]    [0094]FIG. 14 is a schematic view of yet another embodiment of a device according to the invention, shown in a first state;  
         [0095]    [0095]FIG. 15 a  is a schematic view of another embodiment of a device according to the invention being an alternative to the embodiment shown in FIG. 14 and being shown in a first state;  
         [0096]    [0096]FIG. 15 b  is a schematic view of a device according to FIG. 15 a , illustrating the structure of a part of the device;  
         [0097]    [0097]FIG. 16 is a schematic view illustrating the second state of a device according to FIG. 14 or  15   a;    
         [0098]    [0098]FIGS. 17 and 18 are schematic views illustrating another embodiment of a device according to the invention, shown in a first state and a second state, respectively;  
         [0099]    [0099]FIG. 19 is a schematic perspective view of a device for two-dimensional contraction according to the invention;  
         [0100]    [0100]FIG. 20 is a schematic perspective view of another device for two-dimensional contraction according to the invention;  
         [0101]    [0101]FIGS. 21 and 22 schematically illustrate an embodiment of a device according to the invention for treatment of mitral annulus dilatation, shown in a first state and a second shortened state, respectively;  
         [0102]    [0102]FIGS. 23, 24 and  25  are schematic views illustrating the positioning, the fixing and the shortening respectively, of a device according to FIG. 21 when used in the coronary sinus;  
         [0103]    [0103]FIG. 26 is a schematic perspective view illustrating a part of one possible arrangement of a device according to the invention presenting a reshapable area;  
         [0104]    FIGS.  27 - 30  are schematic views illustrating the positioning and the contraction of an embodiment of the device according to the invention for treatment of pathological heart growth;  
         [0105]    [0105]FIGS. 31 and 32 are schematic views illustrating the positioning of an embodiment of the device according to the invention for treatment of chronic obstructive pulmonary disease. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0106]    FIGS.  1  to  4  show the principle of delayed shortening according to the invention.  
         [0107]    In FIG. 1, a shape-changing member  1 , here in the form of a thread  1 , made of or at least in part including a shape memory material is shown having a curved shape. This shape is the original shape that the shape-changing member  1  “remembers” and will assume when the temperature thereof passes a certain threshold, e.g. exceeds  30 ° C.  
         [0108]    [0108]FIG. 2 shows the shape-changing member  1  of FIG. 1 having been straightened by stretching to a substantially straight shape.  
         [0109]    [0109]FIG. 3 illustrates an embodiment of a device according to the invention, where the device is in its non-activated state of shape A. More specifically, by covering the stretched and straight shape-changing member  1  in FIG. 2 with a delay means  2 , here in the form of a tube  2  having a sufficiently small inner cross-section, the stretched shape of the shape-changing member  1  can be maintained even when the device is implanted into a human body and the temperature of the shape-changing member  1  thus exceeds the threshold, e.g. 30° C.  
         [0110]    The delay means  2  may be flexible enough to follow the curves in e.g. vessels, but has a stiffness, here especially in its radial direction, which withstands the shape-changing force of the shape-changing member  1 . Thus, having been implanted into the human body, the shape-changing member  1  of the device will strive towards its original, here curved, shape according to FIG. 1, but is restrained by the delay means  2 .  
         [0111]    However, by manufacturing the delay means  2  from a resorbable material, the delay means  2  will be resorbed by time and the shape-changing member  1  will resume its original shape when the delay means  2  has been resorbed to such a degree or extent that it cannot restrain the shape-changing member  1  any longer, as schematically illustrated in FIG. 4. Thus, the device has now “been transformed” from its non-activated long state of shape A (FIG. 3), to an activated, shortened state of shape A′ (FIG. 4), where the device consists essentially of the shape-changing member  1  only.  
         [0112]    The device in FIG. 3 may be manufactured in the following way. The thread  1  of a shape memory material, e.g. with the shape illustrated in FIG. 2, is programmed to remember the shape illustrated in FIG. 1 by being held in that shape while at the same time being heated to a temperature above said threshold. Upon cooling, beneath the threshold temperature, e.g. down to room temperature, the thread  1  will become more flexible and may more easily be deformed into its previous shape shown in FIG. 2. In this cooled state, the thread  1  is covered by the resorbable tube  2 , e.g. by threading the tube  2  onto the thread  1  or by forming the tube  2  around the thread  1 . Other embodiments of a device according to the invention may operate and may be manufactured in a corresponding manner. Thus, a shape-changing member of a memory material is first held in a “preferred” state of shape while being heated above a threshold temperature, and then cooled beneath the threshold temperature so that it can easily be deformed into its previous “non-preferred” state of shape. Thereafter, the now “programmed” shape-changing member is “locked” in said non-preferred state of shape by a delay means in such a way that the delay means will obstruct the shape-changing member from resuming its preferred state of shape when being heated again, e.g. in a human body. Referring again to FIG. 3, the inner radius of the tube  2  must not necessarily be so small that the shape-changing member in the form of the thread  1  cannot move at all in the radial direction. Hence, there may be a small radial play in which the shape-changing member  1  can move without consequently being able to change the length of the device to any larger extent. However, the device in FIG. 3 may also be manufactured with essentially no play between the shape-changing member  1  and the inner side of the delay means  2 , possibly also with a pretension or bias force from the delay means  2  acting on the shape-changing member  1 .  
         [0113]    In order to clearly illustrate the shortening of the device, the curved thread  1  is located to the left in FIG. 4, but, after its transformation, the thread  1  may just as well be located anywhere along the remaining parts of the tube  2 .  
         [0114]    FIGS.  5  to  8  show the principle of delayed elongation according to the invention.  
         [0115]    In FIG. 5, a shape-changing member  3 , here in the form of a thread  3  of a shape-memory material, is shown having a straight original shape.  
         [0116]    [0116]FIG. 6 shows the shape-changing thread member  3  of FIG. 5 when having been folded to a curved shape.  
         [0117]    [0117]FIG. 7 illustrates an embodiment of a device according to the invention comprising a thread as illustrated in FIG. 6, where the device is in its non-activated state of shape B. By covering the curved shape-changing member  3  with a delay means  4  in the form of a tube  4  of a resorbable material, the curved shape B can be maintained even when the device is implanted into a human body and strives towards its original straight shape.  
         [0118]    As schematically illustrated in FIG. 8, after implantation into the human body, the delay means  4  is resorbed by time and consequently the shape-changing member  3  will be released to resume its original straight shape B′. Thus, the device has now been transformed from its non-activated short state of shape B (FIG. 7) to an activated, elongated state of shape B′ (FIG. 8).  
         [0119]    In the illustrated embodiments, the length of the shape-changing member  1 ; 3  is substantially unchanged by the transformation, whereas the shape of the shape-changing member  1 ; 3  is changed so that the length of the device is changed.  
         [0120]    According to the invention, the material from which the shape-changing member is made may consist of or at least include Nitinol, which is an alloy composed of nickel (54-60%) and titanium. Small traces of chromium, cobalt, magnesium and iron may also be present in Nitinol. Alternatively, other materials such as Shape Memory Polymers (SMP) could be used as the shape memory material.  
         [0121]    Actually, as far as the present invention concerns, the shape-changing material does not have to be a shape memory material. Any superelastic material would function in most applications. For example stainless steel (and other metals) may also be forced into a non-preferred state of shape by means of a resorbable restraining means.  
         [0122]    Examples of usable resorbable materials from which the delay means may be made, or that are at least included, are PDS (polydioxanon), Pronova (polyhexaflouropropylen-VDF), Maxon (polyglyconat), Dexon (PGA, polyglycolic acid), Vicryl (polyglactin), PLA (polylactic acid), PDLLA (polydexolactic acid), PLLA (pololevolactic acid), starch, different kinds of sugar, butyric acid, collagen, and collatamp.  
         [0123]    Depending on the choice of material, the release of the shape-changing forces may be delayed for a desired period of time. Also design parameters such as the thickness of the resorbable material may be set so that the shape-changing forces are delayed as long as desired. The delay time may vary from e.g. a few days up to several years depending on the application.  
         [0124]    The thickness of the delay means may vary along the device, so that the order in which different parts of the device are released by the delay means may be controlled.  
         [0125]    FIGS.  9  to  20  show some different embodiments of a device according to the invention.  
         [0126]    [0126]FIG. 9 shows an embodiment of a device according to the invention being an alternative arrangement of a device for delayed elongation as compared to the device shown in FIG. 7. Instead of a resorbable tube  4  as in FIG. 7, the resorbable means comprises resorbable crosslinks  6  which hold the shape-changing member  5  in its curved state of shape and thus the device in its non-activated short state of shape C.  
         [0127]    Resorbable crosslinks  6  (FIG. 9) may also be combined with a tube  4  (FIG. 7).  
         [0128]    [0128]FIG. 10 shows an embodiment of a device according to the invention in its non-activated elongate state of shape D. Here, the shape-changing member  7  is scissors-shaped. A delay means  8  in the form of a tube  8  of resorbable material holds the shape-changing member  7  in a stretched, elongated state of shape and, thus, also the device in its elongate state of shape D. When the delay means  8  has been sufficiently resorbed, the scissors-shaped shape-changing member  7  will resume its original non-stretched shape and the device is transformed to its activated short state of shape D′ (FIG. 11).  
         [0129]    [0129]FIG. 10 a  shows an alternative embodiment of a device according to the invention, where the tube  8  in FIG. 10 is replaced by a delay means in the form of resorbable threads  8   a . The delay means  8   a  holds the scissors-shaped shape-changing member  7   a  in a stretched, elongate state of shape and, thus, the device in a state of shape corresponding to D in FIG. 10. Referring to FIG. 11 a , when the delay means  8   a  is cut off by means of resorption, the shape-changing member  7   a  will resume its original non-stretched shape and the device is transformed to its activated short state of shape corresponding to D′ in FIG. 11.  
         [0130]    [0130]FIG. 12 shows an embodiment of a device according to the invention in its non-activated short state of shape E. A scissors-shaped shape-changing member  9  of the device is held in a short state of shape by means of a delay means in the form of a resorbable thread  10 , and, thereby, the whole device is held in its short state of shape E. When the delay means  10  is cut off by means of resorption, the shape-changing member  9  will resume its original elongate shape so that the device is transformed to its activated state of shape E′ (FIG. 13).  
         [0131]    [0131]FIG. 14 shows an embodiment of a device according to the invention comprising a shape-changing member in the form of a coil  11  of a shape-memory material having been stretched and arranged in a delay means in the form of a tube  12  of resorbable material. The device is then in its non-activated state of shape F. When the delay means  12  has been sufficiently resorbed, the shape-changing member  11  will resume its original shorter and wider shape as shown in FIG. 16, and the device is transformed to its activated state of shape F′.  
         [0132]    In an alternative embodiment shown in FIGS. 15 a  and  15   b  of a device according to the invention, the tube  12  in FIG. 14 is replaced by a resorbable rod  13  provided with grooves  13   a  in which a coil  11  is initially wound. The winding of the coil  11  in the grooves  13   a  obstructs the coil  11  from resuming its original shape (FIG. 16) and, hence, the device is held in its non-activated state of shape G by the rod  13 , as illustrated in FIG. 15 a . By resorption of the rod  13  in e.g. a human body, the shape-changing force of the coil  11  is released and the device is transformed to its activated state of shape G′ as shown in FIG. 16.  
         [0133]    In another embodiment shown in FIG. 17 of a device according to the invention, a coil  14  is wound around a resorbable rod  15 . When the rod  15  is resorbed, the shape-changing forces of the coil  14  will be released so that the coil  14  resumes an original elongate shape, as shown in FIG. 18, whereby the device is transformed from its non-activated state of shape H to its activated state of shape H′.  
         [0134]    [0134]FIG. 19 shows an embodiment of a device according to the invention in the form of a patch for closing or obstructing openings, e.g. in the heart of a human or animal body. The patch has a shape-changing member  16  comprising a grid matrix formed by threads made of memory material such as Nitinol or SMP. The threads may be covered individually by biocompatible material such as PTFE or dacron to fill in the gaps between the threads, e.g. in the way shown in FIG. 26 with threads  28  and biocompatible material  29 .  
         [0135]    The patch in FIG. 19 further comprises a frame  17  for anchoring the patch in the body, e.g. by means of sutures. The frame may be made of any biocompatible material, such as PTFE or dacron. By the use of a cone (not shown), the threads may be spread apart, creating a central opening  16   a  in the patch. The cone is advanced until a delay means  18  in the form of a separate ring  18  of a resorbable material, initially positioned on the cone, is positioned in the opening  16   a . The cone is then drawn back and the ring  18  is left in the opening  16   a , restraining the elastic threads in such a way that the central opening  16   a  in the patch is maintained. FIG. 19 shows the patch in its non-activated state of shape I with the ring  18  positioned centrally. After implant and sufficient resorption of the restraining ring  18  and after a specified period of time, the central opening in the patch is closed and the patch is activated.  
         [0136]    [0136]FIG. 20 shows an alternative embodiment of a device according to the invention in the form of a patch for closing openings. The patch may be constructed by attaching delay means  19  in the form of resorbable threads or bands  19  to the top of a sharp cone and down along the sides of the cone, advancing the cone through the middle of the patch so that the elastic threads  16  are spread out and thus an opening  16   a  in the patch is created, and fastening one end of each band to the frame  17  on one side of the patch and the other end of each band  19  to the frame  17  on the other side of the patch, so that each band  19  encircles the opening. The bands  19  could be placed at regular intervals along the circumference of the opening so that they expand a substantially circular hole in the middle of the patch. By means of the resorbable bands  19 , the patch is held in its non-activated state of shape J.  
         [0137]    It is to be noted that the above-described different embodiments are examples only. There are many possible different forms of a device according to the present invention. For example, the single shape-changing thread in FIGS.  1  to  9  may be replaced by several threads or by one or more bands. The scissors-shaped members  7  and  9  in FIGS.  10  to  13  may be multiplied so as to form a scissor-shaped area, which in turn may be shaped into different forms. The single tube in FIGS. 3, 7,  10  and  14  may be slotted or may be divided into several tube segments. A delay means may also be provided in the form of resorbable glue, which holds parts of the shape-changing member together and in that way delay the change of shape of the device. The number of possible designs of a device according to the invention is, in fact, infinitely great.  
         [0138]    Next, an embodiment according to the invention of a device for treatment of mitral annulus dilatation will be described.  
         [0139]    The device shown in FIG. 21, being in an elongate and non-activated state of shape K, comprises a shapechanging member  20  in the form of a shape memory metal thread  20 , a delay means  21  in the form of a resorbable sheath  21  enclosing the shape memory metal thread  20  for holding it in a straightened state of shape, and preferably self-expandable stents  22  and  23  located at the opposite ends of the device.  
         [0140]    The device may include one or more additional shape memory metal threads, e.g. if a stronger shortening force is desired.  
         [0141]    The shape memory metal thread  20  may be made of Nitinol, or other similar material which has a memory of an original shape as illustrated in FIG. 22, and can be temporarily forced into another shape, e.g. as illustrated in FIG. 21.  
         [0142]    The resorbable sheath  21  is made of PDS, but it may also be made of any other material which is resorbable by the surrounding blood and tissue when applied in a human body and has the required stability and bending properties. The thickness of the resorbable sheath  21  is chosen so that the time needed for the surrounding blood and tissue in the coronary sinus  24  to resorb the resorbable sheath  21  enough for the device to enter its second shorter state of shape K′ is adapted to the time needed for the ends of the device to be fixed within the coronary sinus  24 .  
         [0143]    The self-expandable stents  22  and  23  may be of conventional type with an elastic cylindrical unit, made of e.g. Nitinol, in an opened zigzag configuration. FIG. 21 a  shows an alternative embodiment according to the invention of a device for treatment of mitral annulus dilatation. Here, the shape memory metal thread  20  is replaced by a scissors-shaped shape-changing member  20   a . The resorbable sheath  21  may then be replaced by resorbable threads  21   a , like in FIG. 10 a . Preferably, self-expandable stents  22   a  and  23   a  are located at the opposite ends of the device. The state of shape corresponding to K′ in FIG. 22 of the device shown in FIG. 21 a  is shown in FIG. 22 a.    
         [0144]    The above-described device as seen in FIG. 21 (or the device as seen in FIG. 21 a ), is positioned in the coronary sinus  24 , shown in FIGS.  23  to  25 , in the following way:  
         [0145]    An introduction sheath (not shown) of synthetic material may be used to get access to the venous system. Having reached the venous system, a long guiding metal wire (not shown) is advanced through the introduction sheath and via the venous system to the coronary sinus  24 . This guiding wire and/or a delivery catheter is provided with X-ray distance markers so that the position of the device in the coronary sinus  24  may be monitored.  
         [0146]    The elongate device in FIG. 21 (or the one in FIG. 21 a ) is locked onto a stent insertion device (not shown) so that the self-expandable stents  22  and  23  (or  22   a  and  23   a ) are held in a crimped, non-expanded state. Thereafter, the stent insertion device with the elongate device locked thereon is pushed through the introduction sheath and the venous system to the coronary sinus  24  riding on the guiding wire. After having obtained an exact positioning of the elongate device in the coronary sinus  24 , as illustrated in FIG. 23 where the mitral valve annulus  25  and the mitral valve  26  having a central gap  27  are shown, the stent insertion device is removed. This will release the self-expandable stents  22  and  23  (or  22   a  and  23   a ) so that they expand and contact the inner wall of the coronary sinus  24  and thereby provide for a temporary fixation of the elongate device in the coronary sinus  24 . Then, the guiding wire and the introduction sheath are removed.  
         [0147]    After the insertion, the self-expandable stents  22  and  23  (or  22   a  and  23   a ) will grow into the wall of the coronary sinus  24  while at the same time the resorbable sheath  21  (or restraining threads  21   a ) will be resorbed by the surrounding blood and tissue in the coronary sinus  24 , as schematically illustrated in FIG. 24. When the resorbable sheath  21  (or resorbable threads  21   a ) has been resorbed to such a degree that it cannot hold the shape memory metal thread  20  (or the scissors-shaped member  20   a ) in its straightened state of shape any longer, the self-expandable stents  22  and  23  (or  22   a  and  23   a ) will be properly fixed into the wall of the coronary sinus  24  as a result of the normal healing process which always occurs after positioning a stent in a blood vessel. Then the shape memory metal thread  20  (or the scissors-shaped member  20   a ) retracts and the device is transformed to its activated shorter state of shape K′, as illustrated in FIGS. 22 and 25 (corresponding to FIG. 22 a ). This shortening of the device makes it bend towards the mitral valve annulus  25 , moving the posterior part thereof forward. This movement reduces the circumference of the mitral valve annulus  25  and thereby closes the central gap  27 .  
         [0148]    The device may be positioned by catheter technique or by any other adequate technique. It may be heparin-coated so as to avoid thrombosis in the coronary sinus  24 , thus reducing the need for aspirin, ticlopedine or anticoagulant therapy. At least parts of the device may contain or be covered with drugs like Tacrolimus, Rappamycin or Taxiferol to be delivered into the tissue to prohibit excessive reaction from surrounding tissue. At least parts of the device may be covered with or contain VEGF (Vascular Endothelial Growth Factor) to ensure smooth coverage with endothelial cells.  
         [0149]    [0149]FIG. 26 shows one possible arrangement of a part of a contractable area according to the invention. The contractable area comprises a shape-changing member in the form of a grid matrix of shape memory metal threads  28  covered by a delay means in the form of a fabric of a resorbable material (it should be noted that FIG. 26 was previously used to illustrate how the threads of the patches of FIGS. 19 and 20 may be covered with biocompatible material). The fabric comprises resorbable bands  29  which have been weaved together to form an area. Each of the resorbable bands  29  is solid except for a cylindrical hollow space in which a thread  28  is located, just like the thread  1  is located inside the tube  2  in FIG. 3.  
         [0150]    The bands  29  restrain the threads  28  from being folded to their original curved shapes as long as the fabric  29  is not resorbed.  
         [0151]    Analogously to the device in FIG. 3, there may be a radial play between the inner wall of each band  29  and the thread  28  being located inside it, in which play the thread  28  can move without consequently being able to change the size of the area of the device to any larger extent.  
         [0152]    Further, the hollow space in each band  29  must not necessarily be cylindrical. In fact, if the width of each band  29  is small enough as compared to the curves that the threads  28  will assume when being “activated” as a result of the bands  29  being resorbed, the bands  29  may be hollow.  
         [0153]    The contractable area in FIG. 26 may be manufactured by threading a thread  28  of a memory material into each resorbable band  29  and then weaving the bands  29  with threads  28  together to form the fabric as illustrated in FIG. 26.  
         [0154]    Another possible way of making a contractable area according to the invention would be to arrange threads or bands of a memory material in a grid matrix and to fix the threads or bands together with resorbable crosslinks. The resorbable crosslinks would then restrain the threads or bands from being folded as long as enough resorbable material in the crosslinks is left unresorbed.  
         [0155]    A contractable area according to the invention, as the one previously mentioned or as the one shown in FIG. 26, may be formed into a contractable sac as shown in FIGS.  27  to  30 , which sac may be used to support a body organ or to restrain a pathologically growing body organ.  
         [0156]    FIGS.  27  to  30  illustrate the use of a contractable sac  30  for treatment of pathological heart growth, according to another embodiment of the invention.  
         [0157]    Referring to FIG. 27, the sac  30  in its non-activated state of shape L is threaded inside out on a catheter  31  with an anchoring means  32 , here in the form of a suction cup  32 , and the catheter  31  with the sac  30  is introduced to the apex cordis  33   a  of the heart  33  in known manner.  
         [0158]    Now referring to FIG. 28, the suction cup  32  is put on the apex cordis  33   a  and the sac  30  is pushed off the catheter  31 , by means of a catheter instrument (not shown), over the suction cup  32  and up over the heart  33 .  
         [0159]    Now referring to FIG. 29, when the sac  30  is positioned round the heart  33 , the suction cup  32  is pulled out through the bottom of the sac  30  and the catheter  31  is removed from the body.  
         [0160]    After a period of time, the resorbable material of the sac  30  will be resorbed and a restraining force by the shape memory metal threads against the heart  33  is released, and hence, the sac  30  is transformed to its activated state of shape L′, as illustrated in FIG. 30. The sac  30  will then press itself tight round the heart  33  and apply a continuous restraining force on the heart  33 , thus decreasing the heart size, or at least preventing the heart  33  from growing further.  
         [0161]    A contractable area according to the invention can also be used as a contractable sheet for treatment of alveolar sac growth, e.g. in emphysematic pulmonary diseases.  
         [0162]    [0162]FIGS. 31 and 32 show the use of an embodiment of a device according to the invention for treatment of alveolar sac growth.  
         [0163]    Referring to FIG. 31 a contractable sheet  34  in its non-activated state of shape M is rolled up on a catheter  35 , introduced between ribs  36  into the pleural cavity (the space between the pleura of the lung and the pleura of the chest wall), and placed upon the lung  38  surface to be treated.  
         [0164]    The contractable sheet  34  may also be inserted into the body by means of open surgery or by means of endoscopic surgery and positioned on an organ surface.  
         [0165]    Now referring to FIG. 32, the sheet  34  is then rolled out over the lung  38  and the catheter  35  is removed.  
         [0166]    The sheet  34  is arranged to grow fixed to the lung surface so that subsequent contraction of the sheet  34 , as a result of the resorbable material of the sheet  34  being resorbed, causes the sheet  34  to compress the lung  38  by means of a force of the shape memory metal threads in the sheet  34 . Hence, bullae and areas of enlarged alveolar sacs may be shrunk or eliminated and further pathological growth of alveolar sacs may be prevented.  
         [0167]    In this embodiment the contractable sheet  34  contracts in two directions, one approximately vertical and one approximately horizontal. The sheet  34  could also be designed to contract in one direction only, e.g. the most horizontal one, or contract in a circular mode, and still be able to shrink bullous areas and prevent alveolar sacs from growing.  
         [0168]    It is to be understood that modifications of the above described devices and methods can be made by people skilled in the art without departing from the spirit and scope of the invention.