Abstract:
This invention relates to an occlusion device for the heart, having an articulated center post which allows the device to better conform to the contours of the heart to increase sealing abilities and reduce breakage resulting from conformation pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
   This application is related to U.S. patent application entitled Hoop Design for Occlusion Device, Ser. No. 10/349,118, Occlusion Device Having Five or More Arms, Ser. No. 10/348,701, Septal Stabilization Device, Ser. No. 10/349,744, and U.S. patent application entitled Laminated Sheets for use in a Fully Retrievable Occlusion Device, Ser. No. 10/348,864, all filed on even date herewith. 
   BACKGROUND OF THE INVENTION 
   This invention relates to an occlusion device for the closure of physical apertures, such as vascular or septal apertures. More specifically, this invention relates to an occlusion device for the heart, having an articulated center post which allows the device to better conform to the contours of the heart. 
   Normally, permanently repairing certain cardiac defects in adults and children requires open heart surgery, a risky, expensive, and painful procedure. To avoid the risks and discomfort associated with open heart surgery, modern occlusion devices have been developed that are small, implantable devices capable of being delivered to the heart through a catheter. Rather than surgery, a catheter inserted into a major blood vessel allows an occlusion device to be deployed by moving the device through the catheter. This procedure is performed in a cardiac cathlab and avoids the risks and pain associated with open heart surgery. These modern occlusion devices can repair a wide range of cardiac defects, including patent foramen ovale, patent ductus arteriosus, atrial septal defects, ventricular septal defects, and may occlude other cardiac and non-cardiac apertures. 
   There are currently several types of occlusion devices capable of being inserted via a catheter including button devices, collapsible umbrella-like structures, and plug-like devices. A potential draw back to these devices is the difficulty in ensuring that the occluder conforms to the contours of the defect. Poor conformation to the defect results in poor seating of the device which decreases the ability of the device to occlude the defect. Ensuring the proper seating of an occlusion device once it has been deployed poses a continuing challenge given the uneven topography of the vascular and septal walls of each patient&#39;s heart. The challenge in designing an occluder which conforms to the uneven topography is compounded by the fact that the contours of each defect in each individual patient are unique. 
   Lack of conformation to the walls of the heart can place significant amounts of stress on the occlusion device and decrease fatigue life. Once deployed, different parts of the occluder may experience more or less stress as a result of the uneven topography. At some point, stressed parts of the occluder may break. Broken parts increase the likelihood of damage to the surrounding tissue and lead to patient anxiety. 
   Thus, there is a need in the art for an occlusion device that will occlude cardiac defects and will match the contours of the heart thereby increasing the life of the device and sealing ability while reducing damage the surrounding tissue. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention allows occlusion devices to more effectively close a physical anomaly. The present invention is an occlusion device having an articulated center section. The articulated center section increases the ability of the occlusion device to more accurately conform to the defect. The center section may consist of a post having left and right parts and a joint which links the left and right parts and provides articulation. Any joint or hinge could be used to join the left and right sides. One suitable joint is a ball joint. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an occlusion device with an articulated center post. 
       FIG. 2A  is a diagram of the heart. 
       FIG. 2B  is a diagram of an occlusion device being inserted into a defect. 
       FIG. 2C  is a diagram of an occlusion device with an articulated center section being inserted into a defect. 
       FIG. 2D  is a diagram demonstrating the conformation capabilities of an occlusion device with an articulated center. 
       FIG. 3A  is a side view of an articulated center section having two joints. 
       FIG. 3B  is a side view of an articulated center section having three joints. 
       FIG. 4  is a side view of an articulated center section. 
       FIG. 5  is a side view of a left part of an articulated center section. 
       FIG. 6  is a side view of a right part of an articulated center section. 
       FIG. 7  is a side view of left and right sleeves. 
       FIG. 8  is a cross sectional side view of an assembled articulated center section. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a top perspective view of an occlusion device  10 . As viewed in  FIG. 1 , the device  10  comprises a center section  12 , proximal and distal fixation devices  14 ,  30  (each comprised of six arms  16 ), atraumatic tips  18 , an proximal sheet  20 , and a distal sheet  22 . The proximal and distal fixation devices  14 ,  30  are attached to the sheets  20 ,  22  using sutures  28 . The proximal and distal fixation devices  14 ,  30  are connected to the center post  12 . One method of connecting the arms  16  to the post  12  is to provide the center post  12  with drill holes through which the arms  16  extend. The atraumatic tips  18  are located at the distal end of each arm  16  and serve to minimize damage to the surrounding tissue. The atraumatic tips  18  provide a place for the sutures  28  to attach the sheets  20 ,  22  to the proximal and distal fixation devices  14 ,  30 . One method of suturing the sheets  20 ,  22  to the proximal and distal fixation devices  14 ,  30  is to provide the atraumatic tips  18  with drill holes through which the sutures  28  pass. In this way, the sheets  20 ,  22  are sewn to the fixation devices  14 ,  30  at the atraumatic tips  18 . More specifically, the occlusion device  10  is constructed so that the proximal and distal fixation devices  14 ,  30  are easily collapsible about the center section  12 . Due to this construction, the occlusion device  10  can be folded so that the fixation devices  14 ,  30  are folded in the axial direction. The proximal and distal sheets  20 ,  22  attached to the proximal and distal fixation devices  14 ,  30  are flexible, and can likewise collapse as the proximal and distal devices  14 ,  30  are folded. In addition, the center post  12  further comprises a knob  24 . The knob  24  allows for the device  10  to be grasped as it is inserted into the body through the catheter. 
   Once the device  10  is deployed, the fixation devices  14 ,  30  serve to hold the proximal and distal sheets  20 ,  22  in place to seal the defect. To ensure there is sufficient tension to hold the sheets  20 ,  22  in place, the fixation devices  14 ,  30  are made of a suitable material capable of shape memory, such as nickel-titanium alloy, commonly called Nitinol. Nitinol is preferably used because it is commercially available, very elastic, non-corrosive and has a fatigue life greater than that of stainless steel. To further ensure that the fixation devices  14 ,  30  do not suffer from fatigue failures, one embodiment of the present invention relies on making the wire fixation devices  14 ,  30  of stranded wire or cables. 
   The center section  12  shown in the device  10  is articulated. The articulation can be accomplished by a variety of methods. The articulation could comprise one or more joints, or hinges. It could also be a spring or a coil. Additionally, a spot specific reduction in the amount of material used to create the center section  12  could render portions of the section  12  sufficiently flexible. 
   The center section  12  is preferably formed to have a diameter of between about 8 millimeters and about 0.1 millimeters. In addition, the length of the center section is preferably less than about 20 millimeters. 
   The sheets  20 ,  22  are comprised of a medical grade polymer in the form of film, foam, gel, or a combination thereof. One suitable material is DACRON®. Preferably, a high density polyvinyl alcohol (PVA) foam is used, such as that offered under the trademark IVALON®. To minimize the chance of the occlusion device  10  causing a blood clot, the foam sheets  20 ,  22  may be treated with a thrombosis inhibiting material. One such suitable material is heparin. 
   The size of the sheets  20 ,  22  may vary to accommodate various sizes of defects. When measured diagonally, the size of the sheets  20 ,  22  may range from about 15 millimeters to about 45 millimeters. In some instances, it may be desirable to form the sheets  20 ,  22  so that they are not both the same size. For instance, one sheet and its associated fixation device can be made smaller (25 millimeters) than the corresponding sheet and its associated fixation device (30 millimeters). This is particularly useful in situations where the occlusion device  10  is to be placed at a location in the heart which is close to other nearby cardiac structures. Making the sails  20 ,  22  different sizes may assist in providing optimal occlusion of a defect, without affecting other structures of the heart which may be nearby. 
     FIGS. 2A through 2D  illustrate the method by which the occlusion device  10  is deployed.  FIG. 2A  is a diagrammatic view of a human heart  31 . Visible in  FIG. 2A  is the right atrium  32 , the left atrium  34 , the right ventricle  36 , the left ventricle  38 . The right atrium  32  is separated from the left atrium  34  by a atrial septal wall  40 . The right ventricle  36  is separated from the left ventricle  38  by a ventricular septal wall  42 . Also visible in  FIG. 2A  is an atrial septal defect  44  located in the atrial septal wall  40 , between the right atrium  32  and left atrium  34  of the heart  31 . An atrial septal defect  44  is one example of a cardiac defect that may be occluded using the occlusion device  10 . 
     FIG. 2B  is a more detailed view of the septal wall  40  and the defect  44 , shown between the right atrium  32  and the left atrium  34 . Also shown is the occlusion device  10  of  FIG. 1 , a catheter  50 , and a delivery forceps  52 . As viewed in  FIG. 2B , the occlusion device  10  comprises a distal side  54 , a proximal side  56 , and a center section  12 . The occlusion device  10  is being inserted into the septal defect  44  from the catheter  50 . The device  10  is tethered to the delivery forceps  52 . 
   To insert the occlusion device  10 , the catheter  50  is positioned proximate the septal defect  44 . Next, the delivery forceps  52  is used to push the occlusion device  10  through the catheter  50  so that the distal side  54  of the device  10  unfolds in the left atrium  34 . Although the distal side  54  has been deployed, the proximal side  56  is still folded in the catheter  50 . 
   The placement of the catheter  50 , or other means that guides the device  10  to the defect  44 , determines the location of and angle at which the occlusion device  10  is deployed. Once the catheter  50  is properly positioned at the defect, the delivery forceps  52  is used to push the device  10  through the defect  44 . The distal side  54  of the device  10  is then allowed to expand against septal walls  40  surrounding the defect  44 . 
   In  FIG. 2B , the center section  12  is articulated but the articulation remains inside the catheter  50  and is therefore immobilized. If the center section  12  of the occlusion device  10  is not articulated (or articulated but immobilized), the device&#39;s center section  12  must enter the defect  44  following the same angle of insertion as the catheter  50  or other delivery device. As a result, the insertion angle is limited by the catheter&#39;s angle of insertion  FIG. 2B . 
   Often, due to limited space, the catheter  50  enters the heart at an angle that is not perpendicular to the defective wall  FIG. 2B . In this situation, the device  10  cannot enter the defect  44  properly because the line of the center section  12  must follow the same line as the catheter  50 . The device  10  must be forced into the defect  44  at an angle, which may cause the tissue surrounding the defect  44  to become distorted. If the surrounding cardiac tissue is distorted by the catheter  50 , it is difficult to determine whether the device  10  will be properly seated once the catheter  50  is removed and the tissue returns to its normal state. If the device  10  is not seated properly, blood will continue to flow through the defect  44  and the device  10  may have to be retrieved and re-deployed. Both doctors and patients prefer to avoid retrieval and re-deployment because it causes additional expense and longer procedure time. 
     FIG. 2C  shows an occlusion device  10  with an articulated center section  12  being inserted into a cardiac defect  44 . Shown once again are the defect  44 , septal walls  40 , catheter  50 , and occlusion device  10  comprising a distal side  54 , and a proximal side  56 . In  FIG. 2C , the occlusion device  10  has been further advanced through the catheter  50  to expose the articulated center section  12  comprising a joint  62 . 
   When the center section  12  is articulated or flexible, the insertion angle of the device  10  is not restricted to that of the catheter  50 . The device  10  can be more easily inserted, because once the joint  62  is outside the catheter  50 , the angle of insertion can be changed by allowing the joint  62  to move. This variable insertion angle allows the device  10  to enter the defect  44  at an optimum angle, minimizing distortion of surrounding cardiac tissue. If the tissue is not distorted when the device  10  is deployed, the seating of the device  10  should not change drastically once the catheter  50  is removed. Because the device  10  can be properly seated at the first insertion, the number of cases that require retrieval and redeployment should decrease. 
     FIG. 2D  shows an occlusion device  10  having an articulated center section  12  that is fully deployed and is occluding a cardiac defect  44 . Shown in  FIG. 2D  is a distal side  54 , a proximal side  56 , a center post  12 , a joint  62 , septal walls  40 , and a defect  44 . The distal side  54  has been properly positioned, the proximal side  56  has been deployed and the device  10  has been released.  FIG. 2D  demonstrates the ability of an occlusion device  10  having an articulated center section  12  to conform to an irregularly shaped defect  44 . 
   Another important advantage of the present invention is that the articulated center section  12  allows the distal and proximal sides  54 ,  56  to conform more readily to the contours of the heart  31  after it is deployed, providing a custom fit to a variety of defects. Often, when implanted, an occlusion device  10  is located in an irregularly shaped defect  44 . Having an articulated center section  12  allows the occlusion device  12  to fit in a wider variety of defects, despite the shape or size of the defect. 
   For instance, as viewed in  FIG. 2D , the septal wall  40  on the bottom of the defect may be only a few millimeters thick, but on the top may be many more millimeters thick  FIG. 2D . In such cases, one side of the occluding device  10  may be bent open further than the other side. The side that is more distorted carries a high static load which both increases pressure on the surrounding tissue and increases the possibility of breakage of the device  10 . If the center section  12  is articulated, it can bend such that the upper or lower fixation devices  14 ,  30  need not be the only the only parts which adjust to fit the defect  44 . The ability to conform to a variety of heart contours provides better seating, reduces tension (increasing fatigue life), and decreases the likelihood of damage to tissue resulting from breakage and from pressure the device places on surrounding tissue. 
   Another feature of the occlusion device  10  is that it is fully retrievable. To allow the device  10  to be retrievable, as well as ensure that the device  10  fits into as small a diameter catheter as possible, it is important to ensure that the arms  16  are not of a length that results in the tips  18  clustering at the same location. If the tips  18  all occur at the same location when the device  10  is inside the catheter  50 , the device will become too bulky to allow it to be easily moved through the catheter. 
   In situations where the occlusion device  10  is not properly deployed and must be retrieved into the catheter  50 , it is possible to withdraw the occlusion device  10  back into the catheter  50  by grasping either the center section  12  or by grasping any one of the arms  16 . When the device  10  is retrieved into the catheter  50 , both the upper and lower arms  16  will be folded in the same direction. In such an instance, it is likewise important to vary the length of the upper arms from the length of the lower arms  16  so that when the device  10  is retrieved, the tips  18  on both the upper arms  16  do not cluster at the same location as the tips  18  on the lower arms  16 . 
     FIG. 3A  is a perspective view of an example of an articulated center section  70  with double articulation. As viewed in  FIG. 3A , the center section  70  comprises a right part  72 , left part  74 , and a center part  76 . The left part  74  has a knob  24  located on one end. Both right and left parts  72 ,  74  have three holes  80  drilled through them. The center section  70  further comprise two joints or hinges  78  on each end of the center part  76 . The joints or hinges  78  connect the right and left parts  72 ,  74  to the center  76  and allow for the right and left parts  72 ,  74  to rotate relative to the center part  76 . The wire arms  16  ( FIG. 1 ) attach to the center section by passing through the holes  80  drilled through the left and right parts  72 ,  74 . 
   In this example, a joint  78  provides the articulation. Though shown with a double articulation, the articulated center section  70  is not so limited. The number of joints or hinges  78  may be varied to accommodate a particular defect or a particular type of defect. For example, one joint or hinge may be best for an atrial septal defect while two or three articulations may be best for a larger defect such as patent foramen ovale or a long defect such as patent ductus arteriosus. 
   The articulation may be achieved in a variety of ways. Ball joints or hinges may create the articulation. The articulation may also be created by the addition of a spring like coil to the center, a reduction of the amount of material used in a portion the center, or use of material that has ample flexibility when constructing the center. 
   In addition, it is possible to provide the center section with more or less articulations.  FIG. 3B  is a side view of an articulated center section  90  with triple articulation, which demonstrates the range of flexibility of the joints  100 . Shown is a right part  92 , a left part  94  with a knob  24 , two center parts  96 , a joining part  98 , and four joints  100 . The large amount of flexibility allows the occlusion device to conform to a wide variety of defects. If less flexibility is needed, an center section  90  with one or two joints may be preferred. 
     FIG. 4  is an enlarged side view of one example of an articulated center section  70 , showing the section  70  in more detail. The articulated center section  70  is comprised of a right part  72 , a left part  74  which has a knob  24 , a center part  76 , and two joints  116 ,  118 . The center part  76  is comprised of a left sleeve  112  and a right sleeve  114 . The left part  74  connects to center section  76  at the left joint  116 . The right part  72  connects to the center part  76  at the right joint  118 . 
   The joints or hinges  116 ,  118  allow the right and left parts  72 ,  74  to rotate relative to the center part  76 , giving them a full 360° of motion relative to the center part  76 . Preferably, the joints or hinges  116 ,  118  are designed to allow for maximum three dimensional movement of both the right and left parts  72 ,  74  relative to the center part  76 . However, the joints  116 ,  118  may also be configured to provide two dimensional movement of the right and left parts  72 ,  74  relative to the center part  76 . The range of motion need not be a full 360° to be an improvement. Other ranges of motion, such as two dimensional rotation may work also, depending on the type of defect. 
     FIG. 5  is an enlarged side view of the left part  74 . The left part  74  comprises a ball  120 , a first neck  122 , a cylindrical body  124 , a second neck  126 , a knob  24 , and three holes  80 . As described above, three holes  80  are drilled through the part  74  to allow for attachment of the wire arms  16 . 
   The end ball  120  on one end of the left part  74  is connected to the cylindrical body  124  of the left part  74  at the first neck  122 . The knob  24  is located on the other end of the cylindrical body  124  and is connected to the body  124  by a second neck  126 . To assist in assembly, discussed in more detail below, the cylindrical body  124  of the left part  74  is preferably smaller in diameter than the ball  120 . The knob  24  has a smaller diameter than both the body  124  and the ball  120 . For example, the end ball  120  may have a diameter A of about 1.35 millimeters, the cylindrical body  124  may have a diameter B of about 1.2 millimeters, and the knob  24  may have a diameter C of about 1.0 millimeter. 
   The knob  24  is configured to allow a delivery forceps  52  to attach to the occlusion device  10  as it is pushed through the catheter  50  and allows the forceps to manipulate the device  10  as it is delivered. Likewise, a guide forceps can be used to position the occlusion device  10  once it reaches the desired location or to retrieve the device  10  should it not be seated properly. The knob  24  may additionally have a cross sectional area which allows the forceps to rotatably move the device while the device is inserted into a defect  44 . The second neck  126  is grasped by a forceps so that there is at least some play between the forceps and the second neck  126  when pushing the device through a catheter. For example, the guide forceps may engage the second neck  126  by means of a claw-like or hook-like end. In an alternate embodiment, the knob  24  is threaded to allow for attachment to a threaded guide forceps. 
     FIG. 6  is a side view of a right part  72 . The right part  72  comprises a ball  130 , a first neck  132 , a cylindrical body  134 , and three holes  80 . Once again, three holes  80  are drilled through the part  72  to allow for attachment of the wire arms  16 . 
   The right part  72  is nearly identical to the left part  74  except that it does not require a knob  24  or second neck  126 . Because the occlusion device  10  only needs to be graspable at one end, a second knob is unnecessary. To assist in assembly, the cylindrical body  134  of the right part  72  is preferably smaller in diameter than the ball  130 . For example, the end ball  130  may have a diameter D of about 1.35 millimeters, and the cylindrical body  134  may have a diameter E of about 1.2 millimeters. 
     FIG. 7  is an exploded view of the center section. Shown is a right sleeve  112  and a left sleeve  114 . The right sleeve  112  comprises a cuff  140 . The cuff  140  is configured to fit inside the left sleeve  114  when the two sleeves are assembled. As shown more clearly on  FIG. 8 , the two sleeves  112 ,  114 , once assembled, the two sleeves  112 ,  114  can be permanently attached at the cuff  140 , and secured by welding. 
     FIG. 8  shows a cross sectional view of an assembled articulated center post. Shown is the left part  74 , the right part  72 , and the center part  76 , which comprises the left sleeve  114 , and the right sleeve  112  having a cuff  140 . Also shown is a washer  150 . Each sleeve has a sleeve opening  152 . Also shown are the details of the left and right parts: a knob  24 , a second neck  126 , first necks  122 ,  132 , cylindrical bodies  124 ,  134 , end balls  120 , 130 , and holes  80 . The sleeves  112 ,  114  have been welded together. 
   To assemble the center post, the left and right parts  74 ,  72  are slipped into the corresponding left and right sleeves  114 ,  112 . As described above, the diameter of balls  120 ,  130  is less than the diameter of bodies  124 ,  134 . As a result, the cylindrical bodies  124 ,  134  are small enough to fit through the sleeve openings  152 ,  154  but the end balls  120 ,  130  are too large to fit through the sleeve openings  152 ,  154 . Once, the left part  74  is placed through the left sleeve  114 , the cylindrical body  124  extends out the sleeve opening  152  but the end ball  120  remains inside the sleeve  114 . Similarly, once the right part  72  is slipped through the right sleeve opening  154 , the body extends out the sleeve  112  but the end ball  120  remains inside the sleeve  112 . The washer  150  may be inserted at the end of the cuff  140  of the right sleeve  112 . Next, the left sleeve  114  and the right sleeve  112  are joined by inserting the cuff  140  into the left sleeve  114 . Once assembled, the sleeves  112 ,  114  are welded together. 
   The resulting assembly forms two ball joints which are able to rotate independently of each other relative to the center part  76 . The first necks  122 ,  132  sit at the sleeve opening  152 , 154  after the cylindrical bodies  124 ,  134  have been pushed through the corresponding sleeve openings  152 ,  154 . The diameters of the necks  122 ,  132  are smaller than the diameter of the sleeve openings  152 ,  154  so the necks  122 ,  132  have ample space to rotate freely in the sleeve openings  152 ,  154 . The end balls  120 ,  130  are separated by the washer  150  so that they do not come in contact with each other and restrict each other&#39;s movement. The washer  150  also prevents the end balls  120 ,  130  from moving too far into the center of the sleeves  112 ,  114 . If the end balls  120  were allowed to move too far back into the sleeves  112 ,  114 , the left and right parts  74 ,  72  could also move into the sleeves  112 ,  114 , thereby restricting the movement of the joints  116 ,  118 . Preferably, a hard metal, such as titanium, is used to construct the parts of the center post because use of a hard material prevents binding within the ball joints. 
   There may be occasions where an occlusion device with single articulation or one joint is preferred. In one embodiment a neck  122 ,  132  is welded in place in the sleeve opening  152 , or formed integrally, to immobilize one joint if only a single movable joint is desired. Alternatively, one of the end balls  120 ,  130  could be welded to the washer  150  to immobilize one of the joints. 
   Though shown in a patent foramen ovale occlusion device, an articulated center post can be adapted for use in any occluding device, including those designed for atrial septal defects, patent ductus arteriosus, and ventricular septal defects. The center post can also be adapted for use in an septal stabilization device. 
   Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. In particular, any of the applicable features disclosed in related applications U.S. patent application entitled Septal Stabilization Device, Ser. No. 10/349,744, U.S. patent application entitled Hoop Design for Occlusion Device, Ser. No. 10/349,118, Occlusion Device Having Five or More Arms, Ser. No. 10/348,701, and U.S. patent application entitled Laminated Sheets for Use in a Fully Retrievable Occlusion Device, Ser. No. 10/348,864, filed on even date herewith, may be of use in the present invention. Each of these applications is hereby incorporated by reference.