Patent Application
20090030450
The present invention relates generally to a medical device for closing an opening or defect in an organ within a living body, e.g. a septal defect in a heart or a percutaneous puncture in a vessel wall (such as walls in arteries or other blood vessels), and in particular to an expandable and repositionable closure device, which can be remotely maneuvered from an initial positioning configuration to a final configuration in which the opening or defect is closed.
The closing of an opening in an organ of a patient is a medical procedure that frequently has to be practiced by doctors or other trained medical personnel. The opening may be a hole created by the doctor for a specific and usually temporary purpose, or the opening can be a congenital or acquired defect. An example of the former would be a puncture hole created in a patient's femoral artery to obtain access to the coronary system, while an example of the latter is a septal defect in a patient's heart. For descriptive and illustrative purposes the present invention will be described with reference to such a septal defect, although such techniques can be applied to other fields of application, such as walls in arteries or other blood vessels.
As is well-known, the human heart is divided into four chambers: the left atrium, the right atrium, the left ventricle, and the right ventricle. The atria are separated from each other by the interatrial septum, and the ventricles are separated by the interventricular septum.
Either congenitally or by acquisition, abnormal openings or holes can form between the chambers of the heart, causing shunting of blood through the opening or hole. For example, with an atrial septal defect, blood is shunted from the left atrium to the right atrium, which produces an over-load of the right side of the heart. In addition to left-to-right shunts such as occur in patent ductus arteriosus from the aorta to the pulmonary artery, the left side of the heart has to work harder because some of the blood will recirculate through the lungs instead of going to the rest of the body. The ill effects of such lesions usually cause added strain to the heart with ultimate failure if not corrected.
One way to cure a septal defect in the septum of a heart is to position and anchor a specially designed closure device at the septum such that both sides of the septal defect are spanned by the closure device to thereby close the defect. Examples of such septal defect closure devices are known from the U.S. Pat. Nos. 5,853,422; 6,024,756; 6,117,159 and 6,312,446 to Huebsch et al., which disclose a closure device comprising a cylindrical shaft of metal or polymeric material with concentric parallel cuts through the wall of the device to thereby create flattened support struts. The centers of the support struts are intended to move radially away from the longitudinal axis of the device in a hinge-like fashion in response to movements of the proximal and distal ends of the device towards the center thereof.
A similar septal defect closure device is also disclosed in European patent application EP1651116 to Chanduszko.
The general object of the present invention is to improve a closure device of the aforementioned type in such a way that a more reliable and versatile device is obtained, which more easily can be adapted to the special characteristics of individual patients as well as individual openings, e.g. septal defects or puncture holes.
According to the present invention, a septal defect closure device comprises an elongated tubular member in which a first set of longitudinal slits or cuts have been made on a first side of an uncut central portion and a second set of longitudinal slits or cuts have been made on the opposite side of the central portion. On each side of the central portion, the slits extend towards the ends of the tubular member to terminate a short distance before the respective end, such that uncut proximal and distal end portions are formed. The tubular member, which is made from a flexible and preferably resorbable material, has thereby been provided with proximal and distal sets of struts or ribs. The distal ends of the distal struts are flexibly connected to the distal end portion of the tubular member, while the proximal ends of the distal struts are flexibly connected to the central portion. Similarly, the proximal ends of the proximal struts are flexibly connected to the proximal end portion of the tubular member, while the distal ends of the proximal struts are flexibly connected to the central portion. The struts are further each provided with a weakened section, which can act as a hinge, such that each strut in effect is divided into two articulated arms.
When the septal defect closure device during use is compressed such that the distal and proximal end portions are forced towards each other, the weakened sections of the struts move radially out from the longitudinal central axis of the closure device, and the respective arms of the struts assume an essentially perpendicular angle to the central axis of the closure device. According to the invention, the septal defect closure device further comprises a central elongated locking member, which is separate from the tubular member. In use, the elongated locking member is inserted into the tubular member such that the distal end portion of the tubular member abuts one or several radially protruding portions of a distal end of the locking member, and the proximal end portion of the tubular member is then pushed over one or several radially protruding portions of a proximal end of the locking member. In the compressed state, the central, proximal and distal portions of the tubular member fit snugly along the central locking member, and the closure device is held in the compressed state by the enlarged distal and proximal rims or other radially protruding portions of the locking member, which prevents the closure device from resuming its original elongated shape. The device further comprises a keying feature, which prevents rotational movement of the locking member in relation to the tubular member.
In an alternative embodiment of the invention, the septal defect closure device comprises two separate slit tubular members, which can slide on a common, separate locking member. In practice, these two separately slit tubular members thereby correspond to a closure device as already described above, in which the central portion is cut into two separate halves. A closure device consisting of two separate tubular members and a common, separate locking member will give a doctor enhanced possibilities to adapt a closure device to a patient's specific requirements.
By providing a locking member which is separate from the slit elongated tubular members, a doctor can easily adapt a septal defect closure device to different septa having different thicknesses by simply selecting a locking member of a suitable length. With a separate locking member a closure device can be easier and cheaper to manufacture. A separate locking member can also be made from a different material than the rest of the closure device, to thereby, for example, match the resorption time of a locking member to the resorption time of a tubular member despite their different dimensions and shapes. In other words, a separate locking member can be regarded as a prerequisite for a more reliable and versatile closure device, which also is easier and cheaper to manufacture and which furthermore allows separate modifications of the tubular member without changing the design of the locking member, and vice versa.
A schematic cross-sectional view of a human heart 1 is shown in
In conjunction with
To ascertain correct positioning of the closure device 10 with respect to the septal defect 12, the distal set of struts can be moved radially outwards from the central axis of the closure device 10, such that a partly expanded configuration is obtained. The radial movements of the distal struts are effectuated by partially compressing the closure device 10 through the maneuvering of a mechanical actuator (not shown in the figures). In this semi-expanded locating configuration, the closure device 10 is retracted until the distal struts abut the distal side of the atrial septum 13 surrounding the septal defect 12. The septal defect 12 can thereby be located by a doctor, who in this phase of the medical procedure will feel a marked increase in resistance against further retraction. This intermediate step of the medical procedure is depicted in
As an alternative or complement, the proximal set of struts can be moved radially outwards from the central axis of the closure device 10, such that another partly expanded configuration is obtained. As before, the radial movements of the proximal struts are accomplished by partially compressing the closure device 10 through the maneuvering of the mechanical actuator mentioned above. In this second semi-expanded locating configuration, either the closure device 10 is advanced out of the catheter 11, or the entire assembly is advanced, until the proximal struts abut the proximal side of the atrial septum 13 surrounding the septal defect 12. The septal defect 12 can thereby be located by a doctor who in this phase of the medical procedure will feel a marked increase in resistance against further advancement. This intermediate step of the medical procedure is depicted in
When the atrial septum 13 and thereby the septal defect 12 have been correctly located, either by the step shown in
An embodiment of a septal defect closure device 20 according to the present invention is illustrated in
Here it should further be emphasized that the term “tubular” is merely intended to indicate the general shape of an elongated, hollow member, which comprises a number of struts, the ends of which are connected to ring-shaped or essentially cylindrical members, and which in a first positioning configuration assumes an essentially tubular shape. In other words, a tubular member, like tubular member 21, does not actually have to be cut or slit in order to create distal and proximal struts. On the contrary, a tubular member, having struts with weakened hinge-sections as well as ring-shaped central, distal and proximal end portions, can advantageously be directly produced in this form, e.g. by injection molding or die casting. It can therefore be appreciated that a separate locking member simplifies the manufacture of a closure device of the present type, because, for example, the injection mold can be given a much less elaborated shape.
In
As can be seen in
Similarly to the inner diameter of distal end portion 24, the inner diameters of the central portion 25 and the proximal end portion 26 of the tubular member 21 are marginally larger than the outer diameter of the intermediate portion 31 of the locking member 30. Additionally, the outer diameter of the proximal end rim 34 is slightly larger than the inner diameter of the proximal end portion 26. During use, the proximal end portion 26 of the tubular member 21, which is made from a somewhat elastic material, must therefore be forced over the proximal end rim 34 and can then slide on the intermediate portion 31. As can be seen in
In the embodiment of the locking member shown in
In
In
Another way to facilitate the adaptation of a septal defect closure device to septa having different thicknesses is to arrange the distal set of struts and the proximal set of struts as two separate members. Such an arrangement would effectively correspond to cutting a tubular member like the tubular member 21 of
The septal defect closure device has been shown with proximal and distal struts having equal lengths. It is, however, possible to provide a closure device having proximal struts with one length and distal struts with a different length. It may, for example, be desirable to arrange a closure device in such a way that the left part of the closure device, i.e. the part that is implanted into the left atrium of a heart, is smaller than the right part of the closure device, to thereby reduce the amount of artificial material introduced into the left atrium, which in turn may reduce the formation of thrombogenic material therein. In this context, it should be recognized that it is not mandatory that a heart is accessed via the venous system, as is shown in
As mentioned earlier, it is conceivable that the distal and/or proximal struts at least partly are covered by a thin membrane or formed integrally with a thin membrane, which preferably is made from a resorbable material. This membrane can be e.g. a thin film made from resorbable polymers or a mesh made from electrospun polymers, which are, for example, woven or braided together. Similarly to the situation discussed above with a smaller part of the device placed in the left atrium of the heart, the membrane is preferably provided on the right side of the septal defect, to minimize the amount of material introduced into the left side of the heart. A thin membrane is also particularly beneficial when used for the repair of a vessel wall, where the membrane is preferably placed inside the vessel in order to take advantage of the blood pressure in keeping the device in place.
It has already been mentioned that the length of the distal struts can differ from the length of the proximal struts; and it is also possible to have different lengths of the articulated arms within a strut set, such that, for example, the distal arms are longer than the proximal arms, or vice versa. The arms that actually contact a septum or a vessel wall can, for example, be shorter than the arms that do not contact the septum or the vessel wall, to thereby ensure a reliable closing of a septal defect in the septum or a puncture hole in the vessel wall.
In the embodiment shown in
As already has been stated, a closure device comprising a central locking member that is separate from a tubular member can be regarded as a prerequisite for other advantageous effects. A two-piece closure device is generally easier and thereby cheaper to manufacture. If, for example, the closure device is produced by injection molding, the molds—i.e. one mold for the locking member and one mold for the tubular member—can be given comparatively less complicated shapes than if the closure device was to be molded in a single mold.
It is in particular anticipated that a locking member is made from a first material and that a tubular member is made from a second material, something which in practice may require that the locking member is separate from the tubular member. With different materials some specific advantages can be achieved. If, for example, the closure device is a resorbable closure device, then the resorption time of the material in the locking member can be different from the resorption time of the material in the tubular member, such that the mechanical properties of the closure device are maintained until the surrounding tissue has healed to the point where the support of the closure device is not necessary anymore. Further, whether or not the materials are resorbable materials, different requirements are put on the different pieces. For example, the material in the hinge portions of a tubular member must be ductile and have a high durability, whereas the locking member must have a rather high stiffness. Furthermore, it may be necessary to have one material in a locking member and another material in a tubular member in order to match the resorption times due to different dimensions of the members involved in a resorbable closure device.
Examples of resorbable materials for the tubular member and the locking member may include, but are not limited to, those materials made from aliphatic polyesters, polyether esters, and polycarbonates. More specifically, synthetic resorbable polymers such as homopolymers and copolymers made from any of the monomers lactide, glycolide, epsilon-caprolactone, trimethylene carbonate, and paradioxanone are advantageous because of their long clinical use. Other lactones that may be used together with any of the abovementioned monomers to make copolymers of various properties are valerolactone, b-butyrolactone and dioxepanone, however also other 4, 5, 6 and 7 member lactones may be of interest to obtain the characteristic material properties needed to fulfill a smooth operation of the invented closure device.
The tubular member could preferably be made from a semi-crystalline material with a lower modulus than the locking member. As previously stated, the device could, e.g. because of the hinge portions, have a more flexible material in the tubular member. Such material is preferably made from a block copolymer characterized by having a soft middle part distinguished by having a glass transition temperature below body temperature and a semi-crystalline part at each end of the soft middle part. The semi-crystalline part could be polymerized from any of the monomers glycolide, lactide, or paradioxanone. Since polyparadioxanone is a relatively soft and pliable material compared to polyglycolide and polylactide, the tubular member can be made from pure polyparadioxanone itself.
The locking member can be made from any of the above materials, but to secure the locking mechanism it is advantageous if the material is stiffer than the material used in the tubular member. The material should also preferably resorb at a somewhat slower pace than the tubular member. The locking member could also be made from amorphous or semi-crystalline material, and preferably from homopolymers or copolymers where the main monomer component is lactide, caprolactone, or paradioxanone.
Further examples of synthetic resorbable polymers that may be used in the tubular or locking member of the invented closure device are resorbable polymers made from dicarboxylic acids such as succinic, glutaric, adipic or pimelic acids with various forms of diols, polymers composed of segmented blocks of polyethyleneglycol and butyleneterephthalate, various forms of tyrosine carbonate polymers, phosphazene polymers, orthoester polymers or resorbable polyurethanes.
A particular advantage of the groups of synthetic resorbable polymers mentioned above is that various mechanical properties can be accomplished by simply changing the monomer composition in the homopolymer or copolymer. Further, in contrast to natural biopolymers, these materials can be molded and machined into complex structures, and by varying the monomer composition large time spans can be achieved for their resorption times.
It may be appreciated that it can be advantageous to provide a radiopaque closure device which is visible in an X-ray machine. When the closure device is made from a synthetic resorbable polymer, a radiopaque closure device can conveniently be produced by mixing the polymer with a suitable radiopaque agent. A suitable radiopaque agent is barium sulfate, which can be blended into the polymer or copolymer in an amount between 5% and 50%, and more preferably in an amount of 15% to 30%, to obtain the opacity needed in order to locate the closure device during an X-ray observation. Radiopaque materials can be used in a tubular member of the closure device, but is preferably used in the locking member, which marks the center of the device. The radiopaque agent, e.g. barium sulfate, can be—instead of being mixed with the polymer—introduced into preformed holes in the closure device, which are then sealed by a synthetic resorbable material. As an alternative, preformed holes can be plugged with a resorbable material containing a large amount of a radiopaque agent, e.g. barium sulfate.
Although the present invention has been described with reference to specific embodiments, also shown in the appended drawings, it will be apparent for those skilled in the art that many variations and modifications can be done within the scope of the invention as described in the specification and defined with reference to the claims below. It is possible to have different lengths of the articulated arms within a strut set, such that, for example, the distal arms are longer than the proximal arms, or vice versa. The weakened strut sections discussed above can be replaced with other designs that provide the desired hinge-like action. The hinge action could, for example, be accomplished by real hinges arranged along the struts. In addition, as mentioned earlier, it should be apparent that the present invention can be used in other applications than the repair of a septal defect, e.g. the repair of a puncture of a vessel wall after an intervention that requires the insertion of a guide wire into the blood vessel, or the promotion of healing of other punctures or openings within the vascular system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 071041529 | Mar 2007 | EP | regional |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11386098 | Mar 2006 | US |
| Child | 12020860 | US |
