Patent Application
20080167682
This invention relates to an occlusion device for repairing cardiovascular defects. More specifically, this invention relates to an occlusion device comprising a bioabsorbable material, which allows the occlusion device to effectively close a defect in the heart while eliminating or limiting components which permanently remain in the body.
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, 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 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.
Although tissue growth occurs over the defect site, once implanted, these occlusion devices remain in position throughout the life of the patient. Therefore, there is some concern that the components of the occlusion device which are under stress may break. Broken components increase the likelihood of damage to the surrounding tissue. In addition, since current occlusion devices are often formed of metallic components there is a possibility that corrosion will occur over a period of time.
Thus, there is a need in the art for an occlusion device that will occlude cardiac defects for a period during which tissue growth occurs and is then capable of being absorbed into the body after a sufficient amount of time.
The present invention allows effective closure of a cardiac defect, while eliminating or minimizing components which remain in the body permanently. The present invention is an occlusion device having first and second support frames comprising a plurality of arms, a center post extending between the first and second support frames, and first and second sheets attached to the first and second support frames, respectively. The components of the occlusion device are comprised of a bioabsorbable material.
Proximal and distal support frames 12, 14 are comprised of arms 16, 18, respectively, and are attached to proximal and distal sheets 26, 28. Center post 22 extends between proximal and distal support frames 12, 14. Although in the exemplary embodiment shown in
One method of connecting proximal and distal support frames 12, 14 to center post 22 is to provide center post 22 with holes through which arms 16, 18 extend. In the exemplary embodiment shown in
Center post 22 is preferably formed to have a diameter of less than about 10 millimeters and a length of preferably less than about 20 millimeters. The size of proximal and distal sheets 26, 28 may vary to accommodate various defect sizes. When measured diagonally, the size of proximal and distal sheets 26, 28 may range from about 15 millimeters to about 45 millimeters. In some instances, it may be desirable to form sheets 26, 28 so that they are not both the same size. For instance, one sheet and its associated support frame can be made smaller (25 millimeters, for example) than the opposing sheet and its associated fixation device (30 millimeters, for example). This is particularly useful in situations where occlusion device 10 is to be placed at a location in the heart, which is close to other nearby cardiac structures. Making sheets 26, 28 different sizes may assist in providing optimal occlusion of a defect, without affecting other structures of the heart, which may be nearby.
Occlusion device 10 is constructed so that proximal and distal support frames 12, 14 are easily collapsible about center post 22. Due to this construction, occlusion device 10 can be folded so that proximal and distal support frames 12, 14 are folded in an axial direction. Proximal and distal sheets 26, 28, which are attached to proximal and distal support frames 12, 14, are flexible, and can likewise collapse as proximal and distal support frames 12, 14 are folded. Once occlusion device 10 is deployed, proximal and distal support frames 12, 14 must serve to hold proximal and distal sheets 26, 28 in place to seal a defect. In addition, center post 22 further comprises knob 24, which allows for occlusion device 10 to be grasped by a delivery forceps as it is inserted into the body through a catheter.
To insert occlusion device 10, a catheter is positioned proximate the septal defect to be occluded. Next, a delivery forceps is used to push occlusion device 10 through the catheter so that distal sheet 26 attached to distal support frame 12 unfolds in the left atrium. Although the distal portion of occlusion device 10 has been deployed, proximal sheet 28 attached to proximal support frame 14 is still folded in the catheter. The proximal portion of occlusion device 10 unfolds as the catheter is withdrawn.
Another feature of occlusion device 10 is that it is fully retrievable. To allow occlusion device 10 to be retrievable, as well as ensure that occlusion device 10 fits into a small diameter catheter, it is preferable to ensure that the proximal and distal arms 16, 18 of proximal and distal support frames 12, 14 are not of a length that results in atraumatic tips 20 clustering at the same location. If atraumatic tips 20 all cluster at the same location when occlusion device 10 is inside a catheter, occlusion device 10 may be too bulky to allow it to be easily maneuvered through the catheter.
In the exemplary embodiment shown in
Proximal and distal support frames 12, 14, proximal and distal sheets 26, 28, and center post 22 may all be formed of the same bioabsorbable material or a combination thereof. For example, if it is desired that specific components of occlusion device 10 remain in the heart longer than others then occlusion device 10 may be formed of materials having varying resorption rates.
Center post 22 and proximal and distal support frames 12, 14 may be formed by any suitable method such as injection molding or machining. Proximal and distal sheets 26, 28 may be formed by a foaming method. It is also possible to mechanically process proximal and distal sheets 26, 28 by slicing a suitable bioabsorbable material in the desired shape. To minimize the chance of occlusion device 10 causing a blood clot, foam proximal and distal sheets 26, 28 may be treated with a thrombosis inhibiting material, such as heparin.
Forming occlusion device 10 entirely of bioabsorbable materials eliminates many of the concerns associated with conventional devices. For example, since the concern that that components of the occlusion device under pressure, such as proximal and distal arms 16, 18, may break increases over time, it is preferably to limit the amount of time these components remain in the heart. As a result, the likelihood of damage to the surrounding tissue is decreased. In addition, eliminating or limiting the use of metallic components nullifies or at least reduces the possibility that corrosion will occur over a period of time.
The bioabsorbable material used to form occlusion device 10 may also include a radiopaque component so it is possible for occlusion device 10 to be detected on an x-ray. In the alternative, occlusion device 10 may also be coated with a radiopaque material. It is important for occlusion device 10 to be visible so its position in the heart can be monitored during insertion.
In addition, the bioabsorbable material used to form occlusion device 10 may also be invested with drugs or other biologically active therapeutic agents. In that case, occlusion device 10 can be capable of controlled release of these drugs or agents for sustained or local delivery.
In the exemplary embodiment shown in
As described with reference to
In the exemplary embodiment shown in
Often occlusion device 210 must occlude an irregularly shaped defect. For example, the septal wall on the bottom of septal defect may be only a few millimeters thick, but the septal wall on the top of septal defect may be much thicker. In such cases, one side of occlusion device 210 may be bent open further than the other side. The side that is more distorted carries a high static load, which increases pressure on the surrounding tissue and also increases the possibility of device fracture or septal tissue perforation. Forming proximal and distal arms 216, 218 of proximal and distal support frames 212, 214, in addition to proximal and distal sheets 226, 228, out of a bioabsorbable material decreases the likelihood of damage to tissue resulting from device fracture. Because occlusion device 210 remains in place for such a short amount of time, the fatigue life of occlusion device 210 is not an issue. Also, since proximal and distal support frames 212, 214 are formed of a bioabsorbable material, if device fracture does occur, broken fragments will be absorbed by the body over time.
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.
