Patent Publication Number: US-2005119675-A1

Title: Patent foramen ovale closure system

Description:
RELATED APPLICATION  
      This application claims priority from U.S. Provisional Application No. 60/514,390, filed Oct. 24, 2003, entitled “PATENT FORAMEN OVALE CLOSURE SYSTEM,” the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates in certain embodiments to methods and devices for closing a body lumen or cavity and, in particular, for closing a patent foramen ovale.  
      2. Description of the Related Art  
      Embolic stroke is the nation&#39;s third leading killer for adults, and is a major cause of disability. There are over 700,000 strokes per year in the United States alone. Of these, roughly 100,000 are hemorrhagic, and 600,000 are ischemic (either due to vessel narrowing or to embolism). About 50,000 of the ischemic strokes are believed to be caused by a patent foramen ovale. However, the risk of recurrent stroke is higher in patients whose strokes are caused by a patent foramen ovale.  
      Pharmacological therapies for stroke prevention such as oral or systemic administration of warfarin or the like have been inadequate due to serious side effects of the medications and lack of patient compliance in taking the medication.  
      In general, the heart is divided into four chambers, the two upper being the left and right atria and the two lower being the left and right ventricles. The atria are separated from each other by a muscular wall, the interatrial septum, and the ventricles by the interventricular septum.  
      Either congenitally or by acquisition, abnormal openings, holes or shunts can occur between the chambers of the heart or the great vessels (interatrial and interventricular septal defects or patent ductus arteriosus and aortico-pulmonary window respectively), causing shunting of blood through the opening. During fetal life, most of the circulating blood is shunted away from the lungs to the peripheral tissues through specialized vessels and foramens that are open (“patent”). In most people these specialized structures quickly close after birth, but sometimes they fail to close. A patent foramen ovale is a condition wherein an abnormal opening is present in the septal wall between the two atria of the heart. An atrial septal defect is a condition wherein a hole is present in the septal wall between the two atria of the heart.  
      In contrast to other septal defects which tend to have a generally longitudinal axis, a patent foramen ovale tends to behave like a flap valve. Accordingly, the axis of the patent foramen ovale tends to be at an angle, and almost parallel to the septal wall. The patent foramen ovale is a virtual tunnel, long and wide, but not very tall. It is normally closed because the roof and floor of the tunnel are in contact, but it can open when the pressure in the right side of the heart becomes elevated relative to the pressure in the left side of the heart, such as while coughing.  
      Studies have shown that adults with strokes of unknown origin (cryptogenic strokes) have about-twice the normal rate of patent foramen ovales than the normal population. Although there is a correlation between strokes and patent foramen ovales, it is currently unknown why this correlation exists. Many people theorize that blood clots and plaque that have formed in the peripheral venous circulation (in the legs for example) break off and travel to the heart. Normally, the clots and plaque get delivered to the lungs where it is trapped and usually cause no harm to the patient. Patients with a patent foramen ovale, however, have a potential opening through which the clots or plaque can pass from the venous circulation and to the arterial circulation. The clots or plaque can then travel to the brain or other tissues to cause a thromboembolic event like a stroke. The clots may pass to the arterial side when there is an increase in the pressure in the right atrium. Then the clots travel through the left side of the heart, to the aorta, and then to the brain via the carotid arteries where they cause a stroke.  
      Previously, patent foramen ovale have required relatively extensive surgical techniques for correction. To date the most common method of closing intracardiac shunts, such as a patent foramen ovale, entails the relatively drastic technique of open-heart surgery, requiring opening the chest or sternum and diverting the blood from the heart with the use of a cardiopulmonary bypass. The heart is then opened, the defect is sewn shut by direct suturing with or without a patch of synthetic material (usually of Dacron, Teflon, silk, nylon or pericardium), and then the heart is closed. The patient is then taken off the cardiopulmonary bypass machine, and then the chest is closed.  
      In place of direct suturing, closure of a patent foramen ovale by means of a mechanical prosthesis has also been disclosed. A number of devices designed for closure of interauricular septal defects have been used to correct patent foramen ovale.  
      Although these devices have been known to effectively close other septal defects, there are few occlusion devices developed specifically for closing patent foramen ovale.  
     SUMMARY OF THE INVENTION  
      Although the aforementioned devices have been effective in some cases, there is still much room for improvement, and there remains a need for a transluminal method and apparatus for correcting patent foramen ovale. Accordingly, disclosed herein are embodiments of various minimally invasive occlusion devices for closing a patent foramen ovale and methods for their use and operation. Also disclosed is a delivery and positioning system.  
      In one embodiment, a method of closing a patent foramen ovale is provided. The method includes positioning a closure device at a patent foramen ovale and deploying the closure device, such that the septum secundum and septum primum are secured together by the closure device.  
      In some embodiments, a method of closing a patent foramen ovale includes positioning a closure device at a patent foramen ovale and deploying the closure device through a piercing in the septum secundum and septum primum. In various embodiments, the piercing may be created by the closure device, a delivery system, or other instruments prior to or during deployment of the closure device.  
      Another method is disclosed for closing a patent foramen ovale having a septum secundum and a septum primum. The method comprises advancing, with a delivery catheter, a closure device proximate the patent foramen ovale. The closure device may comprise an elongate body coupled to an expandable distal retaining portion. The method further comprises advancing the closure device through a piercing in the septum secundum and septum primum at least until the expandable distal retaining portion extends through the piercing. The expandable distal retaining portion may be expanded, and the distal retaining portion may be retracted to engage one of the septum secundum and septum primum. The method may also comprise advancing a proximal retainer axially relative to the elongate body to engage the elongate body. The advancement of the proximal retaining portion may cause the proximal retaining portion to engage the other of the septum secundum and septum primum and secure portions of the septum secundum and septum primum together.  
      In another method disclosed herein for closing a patent foramen ovale having a septum secundum and a septum primum, the method may comprise advancing with a delivery catheter a closure device proximate the patent foramen ovale. The closure device may comprise an elongate body with a proximal and a distal portion. The distal portion of the elongate body may be coupled to an expandable distal retaining portion. The closure device may further comprise an expandable proximal retaining portion that is configured to be in a substantially unexpanded condition when the closure device is within the delivery catheter. The method may further comprise advancing the closure device at least partially through a piercing in the septum secundum and septum primum at least until the expandable distal retaining portion extends through the piercing and expanding the distal retaining portion and engaging the distal retaining portion against one of the septum secundum and septum primum. The method may additionally comprise expanding the proximal retaining portion and engaging the proximal retaining portion against the other of the septum secundum and septum primum.  
      Another method disclosed herein for closing a patent foramen ovale comprises piercing the septum secundum and septum primum such that a lumen extends between the left and right atria through a portion of the septum secundum and septum primum. The method may also comprise clamping the septum secundum and septum primum together by engaging a portion of the piercing adjacent the septum secundum and engaging a portion of the piercing adjacent the septum primum. When the portions of the piercing adjacent the septum secundum and septum primum are engaged, the patent foramen ovale may be in a substantially closed position.  
      In another method of closing a patent foramen ovale of a patient disclosed herein, the method may comprise advancing a delivery catheter transluminally to the patent foramen ovale, the delivery catheter once advanced may have a distal end positioned adjacent to the septum secundum. The method may also comprise advancing a tissue piercing structure distally relative to the distal end of the delivery catheter. The tissue piercing structure may be provided within a passageway of the delivery catheter and may be connected to a first actuator that has a proximal end extending outside of the patient. Advancing the tissue piercing structure may pierce the septum secundum and the septum primum. The method may also comprise advancing at least partially a closure device relative to a distal end of the tissue piercing structure. The closure device may be provided within an opening of the tissue piercing structure and may be releasably connected to a second actuator extending outside of the patient. The closure device may have an elongate body with an expandable distal retaining portion, and the distal retaining portion once advanced may expand to a dimension larger than a transverse dimension of the tissue piercing structure. The tissue piercing structure may be retracted proximally while the distal retaining portion remains on a distal side of the septum primum, and the distal retaining portion may be retracted proximally to engage the septum primum. The method may further comprise advancing a proximal retaining portion relatively distally from within the opening of the tissue piercing structure, and the proximal retaining portion may have an aperture that engages the elongate body. The proximal retaining portion may be advanced distally while the distal retaining portion is pulled proximally against the septum primum to advance the proximal retaining portion relative to the elongate body and to engage the septum secundum. The second actuator may be released from the elongate body. The method may also comprise withdrawing the delivery catheter, tissue piercing structure, first actuator and second actuator from the patient.  
      A system for closing a patent foramen ovale is also disclosed as comprising a delivery catheter with a proximal end and a distal end and a passageway extending therethrough. A tissue piercing structure may also be provided, having an opening and coupled to a first actuator. The tissue piercing structure may be slideable within the passageway of the delivery catheter and may be configured to pierce through tissue at the patent foramen ovale. The system may also comprise a closure device that is configured to be received within the opening of the tissue piercing structure. The closure device may comprise an elongate body that has proximal end and a distal end. The closure device may also comprise an expandable distal retaining portion at the distal end of the elongate body. The expandable distal retaining portion may have a portion thereof with a dimension that, when expanded, exceeds that of a portion of the tissue piercing structure and is configured to engage tissue on one side of the patent foramen ovale. The closure device may further comprise a proximal retaining portion that has an aperture that extends at least partially therethrough and is configured to engage the elongate body at its proximal end and is configured to engage tissue on another side of the patent foramen ovale. The system may further comprise a second actuator releasably engaged with the proximal end of the elongate body and adapted to move at least the elongate body and the distal retaining portion relative to the tissue piercing structure. Further, the proximal retaining portion may be configured to slide axially at least partially along the elongate body to engage the elongate body.  
      A device is also disclosed for closing a patent foramen ovale. The device may comprise an expandable distal retaining portion that is configured to be deliverable with a delivery catheter. At least a portion of the expandable distal retaining portion may have a width that, when expanded, exceeds that of a portion of the delivery catheter. The device may also comprise an elongate body having a distal and a proximal portion, and either the distal portion or the proximal portion of the elongate body may be configured to be coupled to the expandable distal retaining portion. The elongate body may comprise an elongate expandable portion that is configured to be in an unexpanded condition when placed within the delivery catheter. The expandable portion of the elongate member may be configured to expand when the distal and proximal portions of the elongate member are axially displaced toward each other.  
      For purposes of summarizing the invention, certain embodiments, advantages, and features of the invention have been described herein. It is to be understood that not necessarily all such embodiments, advantages, or features are required in any particular embodiment of the invention, and not all embodiments, advantages, or features are summarized above. Additionally, it is to be understood that this summary is not intended to limit in any way the embodiments, advantages, or features described below in the Detailed Description of the Preferred Embodiments or the Claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an anterior illustration of a heart, with the proximal parts of the great vessels.  
       FIG. 2A  is a side view of an occlusion device in accordance with one embodiment of the present invention.  
      FIGS.  2 B-E are detailed views of the components of the occlusion device of  FIG. 2A .  
       FIG. 3  is a schematic view of an occlusion device delivery catheter.  
       FIG. 4  is a schematic cross-sectional view of one embodiment of the distal end of the delivery catheter.  
       FIG. 5  is a detailed cross-sectional view of the proximal end of a delivery catheter.  
       FIGS. 6-11  are schematic views showing a method of delivery of the occlusion device of  FIG. 2 .  
       FIG. 12  is a schematic view of one embodiment of an anchor element coupled to an actuator.  
       FIG. 13  is a detailed cross-sectional view of one embodiment of the distal end of a delivery catheter.  
       FIG. 14  is a detailed cross-sectional view of another embodiment of the distal end of a delivery catheter.  
       FIG. 14A  is a detailed cross-sectional view of another embodiment of the anchor element.  
       FIG. 15  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIG. 16  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIG. 17  is a schematic view of the occlusion device of  FIG. 16  delivered at a treatment site.  
       FIG. 18  is a schematic view of an occlusion device delivered to a treatment site through the right atrium.  
       FIG. 19A  is a schematic view of an occlusion device in accordance with another embodiment of the present invention in a compressed state.  
       FIG. 19B  is a schematic view of the occlusion device of  FIG. 19A  in an expanded state.  
       FIG. 19C  is a schematic view of an occlusion device in accordance with another embodiment of the present invention in a compressed state.  
       FIG. 19D  is a schematic view of the occlusion device of  FIG. 19C  in an expanded state.  
       FIG. 19E  is a schematic view of an occlusion device in accordance with another embodiment of the present invention in a compressed state.  
       FIG. 19F  is a schematic view of the occlusion device of  FIG. 19E  in an expanded state.  
       FIG. 19G  is a schematic view of an occlusion device in accordance with another embodiment of the invention.  
       FIG. 19H  is a schematic view of an occlusion device in accordance with another embodiment of the invention.  
       FIGS. 19I and 19J  are cross-sections of the occlusion device of  FIG. 19G .  
       FIGS. 19K and 19L  are cross-sections of the occlusion device of  FIG. 19H .  
       FIG. 20  is a perspective view of an embodiment of the tubular element of the device of  FIG. 19A  in an expanded state.  
       FIG. 21  is a schematic view of the occlusion device of  FIG. 19A  delivered at a treatment site.  
       FIG. 22A  is a schematic view of an occlusion device in accordance with another embodiment of the present invention in a compressed state.  
       FIG. 22B  is a schematic view of the occlusion device of  FIG. 22A  in an expanded state.  
       FIG. 23A  is a schematic side view of a delivery device in accordance with another embodiment of the present invention.  
       FIG. 23B  is a schematic end view of the delivery device of  FIG. 23A .  
       FIG. 23C  is a schematic end view of an alternative embodiment of the delivery device of  FIG. 23A .  
       FIG. 24  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIGS. 24A and 24B  are schematic views of the occlusion device of  FIG. 24  attached to a push rod within a delivery catheter.  
       FIG. 25  is a schematic view of the occlusion device of  FIG. 24  in an expanded state.  
       FIG. 26  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIG. 27  is a side view of the occlusion device of  FIG. 26 .  
       FIG. 28  is a schematic view of a delivery system for the occlusion device of  FIG. 26 .  
       FIGS. 29A and 29B  are schematic views of the occlusion device of  FIG. 26  delivered at a treatment site.  
       FIGS. 29C and 29D  are schematic views of the occlusion device of  FIG. 26  being delivered at a treatment site.  
      FIGS.  30  is a schematic view showing a method of delivery of the occlusion device of  FIG. 24 .  
       FIG. 31  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIG. 32  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIG. 33  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIGS. 34A  and B are schematic views of the occlusion devices of  FIGS. 32 and 33  delivered at a treatment site.  
       FIG. 35A  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIG. 35B  is a cross-sectional schematic view of a delivery device for delivering the occlusion device of  FIG. 35A   
       FIG. 35C  is a cross-sectional view of the delivery device of  FIG. 35B .  
      FIGS.  36 A-B are schematic views of an occlusion device being delivered to a treatment site in accordance with an alternative embodiment.  
       FIG. 37A  is a schematic view of an occlusion device in accordance with another embodiment of the present invention.  
       FIG. 37B  is a cross-sectional view of the device of  FIG. 37A .  
       FIG. 37C  is a schematic view of a delivery device for delivering the device of  FIG. 37A .  
      FIGS.  37 D-F are schematic views of a method of delivering the device of  FIG. 37A . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      For simplicity, the embodiments of the present invention will be described primarily in the context of a patent foramen ovale closure procedure. However, the device and methods herein are readily applicable to a wider variety of closure or attachment procedures, and all such applications are contemplated by the present inventors. For example, additional cardiac procedures such as atrial septal defect closure, ventricular septal defect closure, and atrial appendage closure are contemplated. Vascular procedures such as patent ductus arteriosis closure, isolation or repair of aneurysms, anastamosis of vessel to vessel or vessel to prosthetic tubular graft joints may also be accomplished using the devices as described herein. Attachment of implantable prostheses, such as attachment of the annulus of a prosthetic tissue, mechanical heart valve or an annuloplasty ring may be accomplished. A variety of other tissue openings, lumens, hollow organs and surgically created passageways may be closed in accordance with the preferred embodiments. Closures and repairs described herein may be accomplished using catheter based interventional methods or minimally invasive surgical methods. Adaptation of the devices and methods disclosed herein to accomplish procedures such as the foregoing will be apparent to those of skill in the art in view of the disclosure herein.  
      Referring to  FIG. 1 , a heart  100  is illustrated to show certain portions including the left ventricle  102 , the left atrium  104 , the left atrial appendage  106 , the pulmonary artery  108 , the aorta  110 , the right ventricle  112 , the right atrium  114 , and the right atrial appendage  116 . As is understood in the art, the left atrium  104  is located above the left ventricle  102  and the two are separated by the mitral valve (not illustrated).  
      Referring to  FIG. 2A , there is illustrated one embodiment of an occlusion device  200  in accordance with the present invention. It will be appreciated that the term “occlusion” should not be limited to mean full occlusion, as partial occlusion can also satisfactorily accomplish occlusion. The term “occlusion” as used herein is a broad term and is intended to encompass any structure capable of providing an effective barrier within a patent foramen ovale or other opening to be closed or at least partially blocked. The occlusion device  200  includes an anchor element  202  and a retention element  204 . The occlusion device  200  is shown as being generally “I”-shaped. Although the device is shown having an “I”-shape, it is envisioned that a number of variations of this shape can be utilized to provide the same results.  
      In one embodiment, the occlusion device  200  may be made from a medical plastic or a metal, such as stainless steel, Nitinol, Elgiloy®, polyester, PEEK™ or others which can be determined through routine experimentation by those of skill in the art. In another embodiment, the occlusion member  200  may be made of a dissolvable suture material. The occlusion device  200  may also be biodegradable. It is also envisioned that other metallic or non-metallic biocompatible materials may be used to form occlusion device  200 .  
      The occlusion device  200  may have a circular, rectangular, or other shaped cross-section, depending upon the manufacturing technique. In one embodiment, a circular cross section is molded from a biocompatible polymer, such as polyethylene terephthalate (PET).  
      For use in a patent foramen ovale, in one embodiment, the overall width W of the occlusion device  200  may be any value or range of values from about 1 cm to about 5 cm, and, in one more preferred embodiment, is about 1.0 cm. In some embodiments, the overall width of the device  200  may be significantly less than about 1 cm or significantly greater than about 5 cm. The overall length L of the occlusion device  200  from the distal end to the proximal end in one embodiment may be any value or range of values from about 4 mm to about 20 mm and, in one more preferred embodiment, is about 12 mm. In some embodiments, the overall length L of the device  200  may be significantly less than about 4 mm or significantly greater than about 20 mm.  
      As shown in  FIG. 2B , the anchor element  202  has an elongate body portion  206  and a retaining portion  208 . In one embodiment, the longitudinal axis x of the elongate body portion  206  is perpendicular to the longitudinal axis y of the retaining portion  208 . In some embodiments, the angle between the longitudinal axis x of the elongate body portion  206  and the longitudinal axis y of the retaining portion  208  may vary. In some embodiments, the angle between the axis x and the axis y may be any value or range of values between about 15 and 165 degrees. In other embodiments, the angle value or range of values can vary below about 15 degrees and above about 165 degrees. The anchor element  202  may have a circular, rectangular, or other shaped cross-section, depending upon the manufacturing technique.  
      Referring to  FIGS. 2C-2E , the retention element  204  includes a retaining portion  210  and a receiving portion  212  which, in some embodiments, extends outwardly from the retaining portion  210 . The receiving portion  212  may include a lumen or opening  214  for receiving the anchor element  202 . The opening  214  may also include imbedded tines  216  which allow motion distally over the elongate body portion  206  of the anchor element  202 , but grab and hold the elongate body portion  206  if proximal motion is attempted. Alternatively or additionally, the receiving portion  212  may include a plurality of teeth (not shown) within the lumen or opening  214  to prevent movement. In some embodiments, the anchor element  202  may have notches or indentations (not shown) to facilitate engagement of the tines  216 , teeth, or other engaging devices on the retaining portion  210 .  
      The occlusion device  200  is designed in one embodiment to be implanted using a delivery catheter. The device is designed to remain in a collapsed state while in the catheter, as described hereinbelow. Upon delivery to the patent foramen ovale, the device  200  is positioned and expanded to occlude the patent foramen ovale, as described hereinbelow. The device is preferably loaded into or onto the catheter prior to deployment, and is then deployed when properly positioned. The procedure for placing the occlusion device and delivery device will be described in further detail hereinafter.  
      In accordance with one embodiment of the present invention, an occlusion device delivery system may be provided for delivery of an occlusion device to a patent foramen ovale or other septal defect.  
      Referring to  FIG. 3 , a delivery device  300  delivers the occlusion device to the patent foramen ovale  302 . The patent foramen ovale  302  generally includes a septum secundum  304  and a septum primum  306 . The delivery device  300  comprises a catheter  308  having an elongate flexible tubular body  309  extending between a proximal end  310  and a distal end  312 . The catheter is shown in a highly schematic form, for the purpose of illustrating the functional aspects thereof. The catheter body will have a sufficient length and diameter to permit percutaneous entry into the vascular system, and transluminal advancement through the vascular system to the desired deployment site. For example, in an embodiment intended for access at the femoral artery and deployment within the left atrium, the catheter  308  will have a length within the range of from about 50 cm to about 150 cm, and a diameter of generally about or less than about 15 French. In some embodiments, the length of the catheter  308  may be less than about 50 cm or greater than about 150 cm, and the diameter of the catheter may be more than about 15 French. Further dimensions and physical characteristics of catheters for navigation to particular sites within the body are well understood in the art and will not be further described herein.  
      The flexible body can be manufactured in accordance with any of a variety of known techniques. In one embodiment, the flexible body  309  is extruded from any of a variety of materials such as HDPE, PEBAX®, nylon, and PEEK™. Alternatively, at least a portion of or all of the length of the tubular body may comprise a spring coil, solid walled hypodermic needle or other metal tubing, or a braided reinforced wall, as are known in the art. The spring coil, tubing, braided reinforcement, or other structures may be encapsulated with thermoset polymers such as polyimide or with thermoplastic polymers such as PEBAX®, and the like.  
      The tubular body  309  may be provided with a handle  314  generally on the proximal end  310  of the catheter  308 . The handle  314  may be provided with a plurality of access ports. The handle  314  may be provided with an access port which may be used as a guidewire port in an over the wire embodiment, and a deployment wire port. Additional access ports, such as a contrast media introduction port, or others may be provided as needed, depending upon the functional requirements of the catheter. The catheter  308  may be constructed to contain the same number of ports as the handle  314 . The handle  314  permits manipulation of the various aspects of the occlusion device delivery system  300 , as will be discussed below. Handle  314  may be manufactured in any of a variety of ways, typically by injection molding, machining or otherwise forming a handpiece for single-hand operation, using materials and construction techniques well known in the medical device arts.  
       FIG. 4  is a schematic cross-sectional view of one embodiment of the distal end  312  of the delivery device  300 . The catheter  308  may include a passageway  316  for delivery of the occlusion device  200  to the patent foramen ovale. The distal end  312  of the delivery device  300  may include a tissue piercing structure  320 , such as a needle, provided therein. The tissue piercing structure  320  may have a tubular body, such that an opening  326  is formed in which the anchor element  202  and retention element  204  are provided. The tissue piercing structure  320  may have a pointed end  322  for accessing the patent foramen ovale, as will be described below. The tissue piercing structure  320  may be attached to or integral with a first actuator  328 , as will be described below.  
      A second actuator  329 , coupled to the anchor element  202 , and optionally a third actuator  325 , coupled to or engagable with the retention element  204  or optional lock  290 , may be used to deliver and deploy the occlusion device  200  at a treatment site, as described further below. When in the delivery configuration the retention element  204  and lock  290  may be provided over the actuator  329  (see  FIG. 10 ) and be slideable relative thereto. Alternatively, the retention element  204  and lock  290  may in the delivery configuration be provided over the elongate body  206  (see  FIG. 4 ) and be slideable relative thereto. Any of a variety of structures such as polymeric or metal single or multiple strand wires, ribbons, or tubes can be used for the actuators  328 ,  329 ,  325 . The actuators  328 ,  329 ,  325  may be retracted as with a pull wire design and/or rotated as with a torque rod design, and the like, as will be described herein.  
      In one embodiment, the anchor element  202  is bent so that the retaining portion  208  is compressed and substantially parallel to the elongate body portion  206  or longitudinal axis x, and then placed within the tissue piercing structure  320 , which may have an end opening as shown, or a side opening (not shown). The anchor element  202 , in other embodiments, may be at an acute angle with respect to the longitudinal axis x. The catheter  308  also desirably includes a central lumen  316  through which the anchor element  202  and retention element  204  are delivered to the septum, preferably when within the tissue piercing structure  320  which is provided in the central lumen  316 . The anchor element may be locked or wedged or otherwise attached near the base of the tissue piercing structure. In a preferred embodiment, the anchor element  202  comprises a release as described in connection with  FIG. 12  below. In one embodiment, the anchor element  202  may be side-loaded.  
       FIG. 4  also shows the retention element  204  having an aperture or opening  216  through which the elongate body  206  of the anchor element  202  passes through. The retention element  204  is bent to a compressed state when placed within the tissue piercing structure  320 . The retention element  204  is configured to self expand when deployed at a treatment site. Although the retention element  204  is shown as elliptically-shaped, it is contemplated that the retention element  204  may be circular, rectangular, pentagonal, or other shapes. In some embodiments, the retention element  204  may be adjustable, such that the distance between the retention element  204  and the retaining portion  208  of the occlusion element  202  can vary. In some embodiments, a locking element  290  may be provided to lock the retention element  204  in place. The locking element  290  may be provided with tines  292  for locking the retention element  204  and anchor element  202  at a desired location.  
      The tissue piercing structure  320  may be spring loaded, but may also be advanced through the septum manually. In one embodiment, shown in  FIG. 4 , the proximal end of the tissue piercing structure  320  may be connected to actuator  328  contained within lumen  316 . The actuators  328 ,  329 ,  325  may be stainless steel or nitinol or a polymer, such as high-density polyethylene (HDPE) or metal braid reinforced polyimide. The actuator  328  may be welded or bonded or crimped or otherwise affixed to the tissue piercing structure  320 .  
      Actuators  328 ,  329 ,  325  may be a solid wire or a hypotube. In a preferred construction, shown in  FIG. 4 , actuator  328  may be integrally attached to the distal end or other distal point of attachment of the tissue piercing structure  320 . Actuator  329  may be removably attached to the proximal end of the anchor element  202 , and actuator  325  may or may not be attached to lock  290  or retention element  204 . First actuator  328  may be attached to the tissue piercing structure by any technique such as welding, brazing, interference fit such as threaded fit or snap fit, adhesives, crimping, and the like. The actuators  328 ,  329  may comprise a variety of structures which have sufficient lateral flexibility to permit navigation of the vascular system, and sufficient axial column strength to manipulate the tissue piercing structure  320 , and occlusion element  202 , respectively. Any of a variety of structures such as hypotube, solid core wire, “bottomed out” coil spring structures, or combinations thereof may be used, depending upon the desired performance of the finished device. In one embodiment, the actuators  328 ,  329 ,  325  comprise stainless steel tubing. In some embodiments, actuator  325  may comprise a solid wire.  
      As used herein, the term “actuator” is a broad term and is intended to include any of a wide variety of structures that are capable of transmitting axial tension or compression such as a pushing or pulling force with or without rotation from the proximal end  310  to the distal end  312  of the catheter  308 . Thus, monofilament or multifilament metal or polymeric rods or wires, woven or braided structures may be utilized. The actuator may also be reinforced with polymers. The actuator may also be formed with composite materials. Alternatively, tubular elements such as a concentric tube positioned within the outer tubular body  309  may be used, as will be apparent to those of skill in the art.  
      In the illustrated embodiment, the first actuator  328  is integral with or connected to the proximal end of the tissue piercing structure  320 , while the second actuator  329  is releasably connected to the proximal end of the anchor element  202 , and actuator  325  is provided near the proximal end of the retention element  204  (or optional lock  290 ). This permits axial movement of the anchor element  202  and retention element  204  relative to the tissue piercing structure  320 . In particular, second actuator  329  is used to advance the anchor element  202  relative to the tissue piercing structure  320 , and third actuator  325  is used to advance the retention element  204  relative to the tissue piercing structure  320 . In some embodiments, the second actuator  329  may be used to advance the optional lock  290  as well. In other embodiments, the second actuator  329  may be used to advance only the optional lock  290 .  
       FIG. 5  shows a detailed cross-sectional view of one embodiment of the proximal end  310  of the delivery device  300  which will be provided outside of the patient, with actuators  328 ,  329 , and  325  illustrated. In some embodiments, actuator  328  comprises an actuator flange  315 . The delivery device  300  may include a trip lever  335  that holds a spring  330  in a compressed state. The spring  330  is long at rest, and axially compressing the spring stores energy. In some embodiments, the distal end of spring  330  is attached to the proximal end of actuator  328 . In some embodiments, the distal end of spring  330  abuts the proximal end of actuator flange  315 . The trip lever  335  may be attached to the proximal end  310  of the delivery device  300  at pivot  336 . The pivot  336  may be attached to the handle body  313 . The handle body may be made of a metal or polymer, such as stainless steel, nylon, Delrin, and the like. The handle body may be manufactured in any of a variety of ways, such as machining, molding, and the like.  
      The trip lever  335  has a distal end  338  and a proximal end  339 . The proximal end  339  of the lever  335  may extend inside the handle body  313 . The proximal end  339  of the lever  335  contacts the actuator flange  315 . Pushing on the distal end  338  of the trip lever  335  results in a clockwise rotation (when viewed from the perspective of  FIG. 5 ) of the proximal end  339 , thereby disengaging the trip lever  335  from the actuator flange  315 , allowing the spring to advance actuator  328  and tissue piercing structure  320  distally. Nubs  311  may be provided on the interior surface of the catheter  308  to limit the motion of the spring  330  in a proximal direction, allowing the spring to be axially compressed.  
      A handle  332  having openings  334  is attached to actuator  328 . The handle  332  is provided to retract the actuator  328  and tissue piercing structure  320 . Proximally drawing handle  332  relative to handle body  313  proximally draws actuator  328 , thereby compressing the spring  330  and allowing the proximal end  339  to return to the resting position via the trip lever spring  337  and pivot  336 , wherein the spring  330  is compressed. Openings  334  in handle  332  may limit the advancement of actuator  328  and tissue piercing structure  320 , by contacting the proximal end of handle body  313  with handle  332 . The depth of openings  334  may be adjustable to vary the distance the tissue piercing structure  320  may be advanced. In an adjustable embodiment, the handle  332  may comprise a proximal component and distal component (not shown), which have a threaded connection (not shown) to vary the depth of the openings  334 .  
      Actuator  329  extends through handle  310  within actuator  328  and within optional actuator  325  and terminates in an optional handle  392 . Optional actuator  325  extends through handle  310  within actuator  328  and terminates in an optional handle  390 . The proximal end of actuator  329  and/or actuator  325  may be connected to any of a variety of actuator controls including rotational knobs, levers and sliders switches, and the like. In some embodiments, the actuator controls may be attached to handle body  313 .  
      In some embodiments, the exterior surface of handle body  313  may be provided with a system for indicating the axial position of the tissue penetrating structure. In one embodiment, the system comprises a color coded system. In such an embodiment, the exterior surface may be provided with a red colored section and a green colored section. In one embodiment, the green colored section may be visible when the tissue piercing structure is entirely within the catheter  308 , while the red colored section may be visible when the tissue piercing structure at least partially extends outside the catheter  308 .  
      A method of delivering the occlusion device  200  to a treatment site is shown in  FIGS. 6-11 . In use, the deployment catheter  308  is percutaneously introduced into the vascular system and transluminally advanced into the heart and, subsequently, to the patent foramen ovale using techniques which are known in the art.  
      In accordance with some embodiments of the present invention, the delivery catheter  308  with modifications apparent to those of skill in the art in view of the intended application, may be utilized to close any of a variety of tissue apertures using the occlusion devices as described herein. These include, for example, atrial septal defects, ventricular septal defects, patent ductus arteriosis, and others which will be apparent to those of skill in the art.  
      The patent foramen ovale may be accessed via catheter through a variety of pathways. In one embodiment, the patent foramen ovale may be accessed from the venous circuit. The catheter may be introduced into the venous system, advanced into the inferior vena cava or superior vena cava and guided into the right atrium. The catheter may then be directed to the patent foramen ovale. Alternatively, once in the right atrium, the catheter may be advanced through the tricuspid valve and into the right ventricle and directed to a ventricular septal defect and the occlusion device deployed.  
      Alternatively, the patent foramen ovale may be accessed from the arterial circuit. The catheter is introduced into the arterial vascular system and guided up the descending thoracic and/or abdominal aorta. The catheter may then be advanced into the left ventricle through the aortic outflow tract. Once in the left ventricle, the catheter may be directed up through the mitral valve and into the left atrium. When the catheter is in the left atrium, it may be directed into the patent foramen ovale and the occlusion device deployed.  
      The occlusion device is preferably positioned within a septal defect to be occluded, such as a patent foramen ovale. Initially, the device is collapsed inside a delivery catheter  308 , as shown in  FIGS. 3-5 , preferably within a tissue piercing structure  320  within the distal end of the catheter  308 . The delivery system  300  is positioned at or near the patent foramen ovale, as shown in  FIG. 3 .  
      The delivery device  300  is delivered to the patent foramen ovale  302  and the tissue piercing structure  320  is advanced distally through the septum secundum  304  and septum primum  306  by actuating first actuator  328 , as shown in  FIG. 6 . In some embodiments, tissue piercing structure  320  may be advanced across the septa manually. In other embodiments, tissue piercing structure  320  may be advanced across the septa using a spring loaded handle, as shown in  FIG. 5 . Crossing the septa quickly using a spring loaded handle may facilitate crossing of the septum primum  306 . Septum primum  306  may be thin and may tent when the tissue piercing structure  320  contacts the septum primum  306  through manual advancement. This problem occurs especially with aneurismal septa primum.  
      Referring to  FIG. 7 , the anchor element  202  is advanced distally from the tissue piercing structure  320  by actuating second actuator  329 .  
      Once the anchor element  202  exits the tissue piercing structure  320 , the anchor element  202  self-expands into its expanded state from the compressed state, as shown in  FIGS. 8 and 9 . The occlusion device deployment system  300  permits the anchor element  202  to be maintained in a low crossing profile configuration, to enable transluminal navigation to a deployment site. Alternatively, certain embodiments of the anchor element  202  can be enlarged under positive force, such as by a mechanical mechanism.  
      In one embodiment, prior to deployment, the retaining portion  208  is configured inside the delivery system  300  parallel with or at an acute angle with respect to the anchor element  202 . As the retaining portion  208  exits the delivery system  300 , the retaining portion  208  is permitted to assume an unconstrained orientation that is substantially perpendicular to axis x or at an acute angle with respect to axis y. In this embodiment, the retaining portion  208  may assume an unconstrained orientation that increases its width W and may assume a constrained orientation that decreases its width W for deployment by the delivery system  300 .  
      With reference to  FIG. 10 , the tissue piercing structure  320  may be retracted and the anchor element  202  manipulated to draw the septum secundum  304  and septum primum  306  toward one another. By withdrawing the tissue piercing structure  320  proximal to the septum secundum  304  and by pulling proximally on actuator  329  attached to the anchor element  202  while pushing distally on the catheter shaft  308  and/or handle body  313  against the septum secundum  304 , the anchor element  202  moves proximally to compress the septum secundum  304  and septum primum  306 , thereby closing the patent foramen ovale and stopping unintended blood flow. The retention element  204  is secured in position with the anchor element  202  of the occlusion device  200  by distally advancing actuator  325 . This moves the retention element  204  distally over the elongate body  206  until the retention element  204  engages the septum secundum  304 . Depending on the starting location of the retention element  204  ( FIG. 4 ), in some embodiments, the retention element  204  may slide first over actuator  329  before engaging the elongate body  206 . As discussed above, the retention element  204  may have teeth or other structure that permit distal movement but prevent proximal movement. Alternatively, in some embodiments, optional lock  290  ( FIG. 4 ) as discussed above may be used in combination with the retention element  204  to secure the occlusion device  200  in position. In some embodiments, wherein actuator  325  is omitted, actuator  328  may be attached to the tissue piercing structure  320 , and advanced distally to secure the retention element  204  and optional lock  290  in position.  
      The retention element  204  may be delivered to seal the foramen ovale by sliding distally along the elongate body  206  to pinch or compress the septum secundum  304  and septum primum  306  together, in combination with the anchor element  202 . In one embodiment, retention element  204  is also desirably delivered in a compressed state and self-expands into an expanded state upon placement at the patent foramen ovale. Actuator  329  carrying the anchor element  202  may be tensioned while actuator  325  and retention element  204  may be delivered to the treatment site. In some embodiments, anchor element  202  also carries a lock  290 , as described above.  
      After optimal positioning and sealing is achieved, anchor element  202  can be released from the actuator  329  and the delivery device  300  can be removed, as shown in  FIG. 11 . Any excess length of the anchor element  202  proximal to the retention element  204  may be removed, such as by cutting.  
       FIG. 12  shows one embodiment of the distal connection of the actuator  329  to the anchor element  202 . The proximal end of the anchor element  202  may be provided with an opening  350  that is configured to receive a corresponding attachment element  346 . The anchor element  202  and attachment element  346  include an opening  348  through which a small diameter wire or string member  352  can pass through to connect the anchor element  202  and the attachment element  346 . If the attachment element  346  is located distal of the retention element  204  before deployment, the string member  352  may pass through the lumen or opening  214  of the retention element  204 . The string member  352  axially extends through the catheter body  308  to a control means at the proximal end of the catheter body. By manipulating the string member  352 , the string member  352  can be withdrawn from the opening  348 , thereby releasing anchor element  202 .  
       FIG. 13  shows one embodiment of the distal end of the delivery device  300 , illustrating an alternate method of releasing anchor element  202  from actuator  329 . The second actuator  329  is shown attached to the anchor element  202  with attachment element  344 . The attachment element  344  may include a threaded aperture through which the occlusion element  202  is threadably engaged. Any means known may be used for attaching the occlusion element  202  to actuator  329 . For example, any of a variety of bonding techniques for dissimilar materials may be utilized, such as adhesives and various molding techniques. In one embodiment, heat is applied to the attachment element  344  to detach anchor element  202 .  
      In an alternate construction, the anchor element  202  may be delivered and manipulated by rotating a torque element extending throughout the deployment catheter  308 . Referring to  FIG. 14 , the elongate flexible tubular body  308  includes an actuator  360  extending axially therethrough. A rotatable torque rod  362  extends axially through the actuator  360 . The actuator  360  may be integrally formed with or otherwise attached to the tissue piercing element  320 . The rotatable torque rod  362  is releasably attached to the anchor element  202 , such as with screw threading.  
      The proximal end of the torque rod  362  may be connected at a proximal handle to a manual rotation device, such as a hand crank, thumb wheel, rotatable knob or the like. Alternatively, the torque rod may be connected to a power driven source of rotational energy such as a motor drive or air turbine.  
      The distal end of the torque rod may be integral with or connected to a rotatable core, which may extend axially into the elongate body portion  206  of the anchor element  202 . The terms “torque rod” or “torque element” as used herein are broad terms and are intended to include any of a wide variety of structures which are capable of transmitting a rotational torque throughout the length of a catheter body. For example, solid core elements such as stainless steel, nitinol or other nickel titanium alloys, or polymeric materials may be utilized. The actuator  360  may be provided with an axially extending central lumen for receiving the torque rod  362 . In an embodiment intended for implantation over a guide wire, the torque rod  362  may be provided with an axially extending central guidewire lumen. This may be accomplished by constructing the torque rod from a section of hypodermic needle tubing, having an inner diameter greater than the outside diameter of the intended guidewire. Tubular torque rods may also be fabricated or constructed utilizing any of a wide variety of polymeric constructions which include woven or braided reinforcing layers in the wall. Torque transmitting tubes and their methods of construction are well understood in the intracranial access and rotational atherectomy catheter arts, among others, and are not described in greater detail herein.  
      Upon placement of the anchor element  202  at the desired implantation site, the torque rod is rotated in a direction that produces an axial proximal retraction of torque rod  362  relative to anchor  202 . Continued rotation of the torque rod will cause the threaded core to exit proximally through a threaded aperture which may be provided in the anchor element  202 . At that point, the deployment catheter  308  may be proximally retracted from the patient, leaving the occlusion element  202  in place.  
      The actuator  360  may be provided with an antirotation lock (not shown) between a distal end of the actuator  360  and the proximal end of the occlusion element  202 . In general, the anti-rotational lock may be conveniently provided by cooperation between a first surface on the distal end of the actuator  360 , which engages a second surface on the proximal end of the anchor element  202 , to rotationally link the actuator  360  and the anchor element  202 . Any of a variety of complementary surface structures may be provided, such as an axial extension on one of the first and second surfaces. Such extensions and recesses may be positioned laterally offset from the axis of the catheter. Alternatively, they may be provided on the longitudinal axis with any of a variety of axially releasable anti-rotational couplings having at least one flat such as a hexagonal or other multifaceted cross sectional configuration.  
      The proximal end of the anchor element  202  may be provided with a threaded aperture through which the torque rod is threadably engaged. Alternatively, the torque rod may be provided with a threadable aperture through which the occlusion element  202  is threadably engaged.  
      With reference to  FIG. 14A , the anchor element  202  may be provided with a guide wire lumen  396 . In an embodiment as shown in  FIG. 14A , the occlusion device may be delivered over a guide wire.  
      In accordance with another embodiment of the present invention, as shown in  FIG. 15 , an occlusion device comprising an anchor element  402  may be provided. The anchor element  402  includes a plurality of occlusion retention portions  408  and an elongate body  406 . In some embodiments, the retention portions  408  may be wire loops comprised of metal or polymer or other generally planar structures. The retention portions  408  may be attached to the elongate body by any of a variety of ways, such as soldering, welding, adhesively bonding, mechanically crimping or swaging, and the like. In some embodiments, the distal end of elongate body  406  may be provided with an opening (not shown) to facilitate attachment of retention portions  408  to the elongate body  406 . In one embodiment, the anchor element  402  may be used with occlusion device  200  in place of the anchor element  202 . Alternatively, anchor element  402  may be used alone as the occlusion device. In one embodiment, the retention portions  408  may be a plurality of petals. The actual number of retention portions  408  can vary. In one embodiment, the number of retention elements may be any value between about 2 and about 10. The actual number of retention elements may also vary significantly below 2 or above 10. The retention portions  408  provide additional retentional support, thereby preventing migration of the septum primum  306  away from the septum secundum  304 .  
      Alternatively, an occlusion device comprises an anchor element  502  having one or more retention structures  507  provided for retaining the device at the septal defect or other body region is shown in  FIG. 16 . The anchor element  502  includes an elongate body  506  and a retaining portion  508 . As shown, the anchor element  502  may be generally “T”-shaped. Although the anchor element  502  has been described as being “T”-shaped, it is also envisioned that the anchor element  502  may be other shapes, such as “I”-shaped, and the like.  
      In the illustrated embodiment, a plurality of barbs  507  or other retention structures are provided, for engaging adjacent tissue to retain the occlusion device  500  in its implanted position and to limit relative movement between the tissue and the occlusion device. Each of the barbs  507  is shown projecting generally radially outwardly from the longitudinal axis, toward the retaining portion  508 .  
      The barbs  507  and corresponding anchor element  502  may be cut from a single ribbon, sheet or tube stock. Barbs  507  may be cut from elongate body  506 , formed of tube stock. Retaining portion  508  may be attached to the elongate body  506  by any means, such as welding, adhesives, mechanical interlock and the like. Alternatively, each barb  507  may be laser cut from the anchor element  502 . In some embodiments, the anchor element  502  may be molded from an engineering polymer. The anchor element  502  which carries the barbs  507  may be advanced from a low profile orientation in which each of the barbs  507  is generally parallel to the longitudinal axis, to an implanted orientation as illustrated, in which the barbs  507  are positioned radially outwardly from the longitudinal axis. In such an embodiment, the barbs  507  may be biased towards the enlarged orientation.  
      As described above, the illustrated retention structures  507  are in the form of barbs. Depending upon the embodiment, three or four or more barbs may be desired on the occlusion device. The barbs may be inclined in a proximal direction, a distal direction, or both to prevent distal movement, proximal movement, or both distal and proximal movement.  
      Any of a wide variety of structures may be utilized for retention structure  507 , such as hooks, barbs, pins, sutures, adhesives, ingrowth surfaces and others which will be apparent to those of skill in the art in view of the disclosure herein. In one embodiment, the anchor element  502  may be used alone, while in other embodiments a retention element, such as retention element  204  shown in FIGS.  2 C-E, may be used with anchor element  502 . In some embodiments, where a retention element is used with the anchor element  502 , the retention structures  507  can be configured to securely interlock with the retainer element in the vicinity of retainer element. For example, retention structures  507  may be positioned along elongate body  506  such that the axial thickness of the retention element  204  is slightly less than the axial separation of the retention structures  507 . Alternatively, the retention structures  507  may mechanically interlock with the imbedded tines  216  of the retention element  204 .  
       FIG. 17  shows anchor element  502  deployed at a treatment site. The anchor element  502  may be delivered to the foramen ovale as shown in  FIGS. 6-11 . However, the actual method of delivery may vary. For example, the tissue retention structures  507  may eliminate the need for the retaining element  204  disclosed with reference to the occlusion device  200 , because the barb orientation prevents movement of the anchor element  502  from the treatment site. Furthermore, anchor element  502  may be configured to penetrate the septum, thereby eliminating the need for a tissue piercing structure, as described with reference to the delivery system  300 . For example, the elongate body  506  or anchor  508  may include a sharp or pointed end for piercing tissue at the treatment site.  
       FIG. 18  shows an alternative delivery method, wherein an occlusion device may be delivered from the right atrium to the left atrium. The tissue piercing structure  320  is delivered to and passes through the septum primum  306 . The actuator  329  may be actuated to deliver the occlusion device  500  to septum primum  306 . The anchor element  502  is configured to puncture the septum primum  306  and the septum secundum  304 . In one embodiment, the distal end of elongate member  506  is sharpened to puncture the septa. The tissue retention structures  507  desirably draw and retain the septum secundum  304  and septum primum  306  toward one another. By approaching the treatment site through the left atrium, it may be possible to better locate the treatment site. The actuator  329  may be a steerable catheter for anchor delivery. Alternatively, the actuator  329  may be made from a shape memory material having a preset curve. Alternatively, a steerable catheter or a catheter having a preset curve (not shown) may be delivered through the tissue piercing structure  320 , while an actuator  329  is delivered through the catheter.  
      In another embodiment, as shown in  FIGS. 19A and 19B , an occlusion device  600  having an anchor element  602  and a retention element  604  may be provided. The anchor element  602  has an elongate body portion  606  and a retaining portion  608 . In one embodiment, the longitudinal axis x of the elongate body portion  606  is perpendicular to the longitudinal axis y of the retaining portion  608 . In some embodiments, the angle between the longitudinal axis x of the elongate body portion  606  and the longitudinal axis y of the retaining portion  608  may vary. In some embodiments, the angle between the axis x and the axis y may be any value or range of values between about 15 and 165 degrees. In another embodiment, the angle value or range of values can vary below about 15 degrees and above about 165 degrees. The anchor element  602  may have a circular, rectangular or other-shaped cross-section, depending upon the manufacturing technique.  
      The retention element  604  has a tubular body  609  having at least two longitudinal openings  611 , as shown in  FIG. 19A  (only one opening is shown). When the tubular body  609  is axially compressed, the region of the tubular body having the at least two longitudinal openings  611  expands radially, as shown in  FIG. 19B . The retention element  604  may also include an attachment element  613  for releasably attaching the occlusion device  600  to a delivery device (not shown). In one embodiment, the attachment element  613  may be similar to the releasable attachment system described in  FIG. 12 .  FIG. 20  shows a detailed perspective view of one embodiment of the retention element in an expanded state.  
      The anchor element  602  may be connected to the retention element  604  by any technique such as welding, brazing, interference fit, threaded connection, snap fit, crimping, and the like.  
      In one embodiment, the occlusion device  600  may be made from a medical plastic or a metal, such as stainless steel, Nitinol, Elgiloy®, or others which can be determined through routine experimentation by those of skill in the art. In another embodiment, the occlusion member  600  may be made of a dissolvable suture material. The occlusion device  600  may also be biodegradable. It is also envisioned that other metallic or non-metallic biocompatible materials may be used to form occlusion device  600 . The occlusion device  600  may be made from a shape memory material preset to its expanded shape, such that the occlusion device  600  self-expands. In one particularly preferred embodiment, the occlusion device  600  is made from Nitinol, a nickel-titanium alloy commonly used for shape memory and super-elastic medical device applications.  
      The elongate body portion  609  may have a circular, rectangular or other-shaped cross-section, depending upon the manufacturing technique. In one embodiment, a circular cross section is cut such as by known laser cutting techniques from tube stock. In one embodiment, the occlusion device  600  may be an integral structure, such as a single ribbon or wire, or an element cut from a tube stock.  
       FIG. 19C  shows another embodiment of occlusion device  600  having two radially enlargeable sections. The occlusion device includes an elongate body portion  609  having at least two longitudinal openings  611 , each at or near the distal end and proximal end of the elongate body portion  609 .  FIG. 19C  shows an integral structure laser cut from Nitinol tube stock, and  FIG. 19D  shows the structure of  FIG. 19C  in an expanded state. When the tubular body  609  is axially compressed, the regions of the tubular body having the at least two longitudinal openings  611  expand radially. The septum secundum  304  and septum primum  306  may be positioned between the two radially enlargeable sections to secure the septum secundum  304  and septum primum  306  together.  
       FIG. 19E  shows an occlusion device  600  having a retention element  604  and an anchor element  602  having an elongate body portion  642 , a distal segment  644 , and an intermediate portion  646  provided between the elongate body portion  642  and the distal segment  644 . The intermediate segment  646  and distal segment  644  form a bend or hook element for securing the septum primum  306 , as described below. The anchor element  602  is attached to tubular body  609  of retention element  604 , the retention element  604  having at least two longitudinal slits  611 . The angle between intermediate segment  646  and distal segment  644  may vary. In one embodiment, the angle between the intermediate segment  646  and distal segment  644  is about zero, such that the two segments together form a structure that approximates the crossbar of a “T”-shape. In one embodiment, the retention element  604  is a member laser cut from Nitinol tube stock, and crimped to the elongate body portion  642  of anchor element  602  at attachment point  648 . The assembly may be heat set into the expanded shape shown in  FIG. 19F  with the retention element  604  being normally expanded. The retention element, when drawn into a delivery device, may temporarily straighten out if engineered to not plastically deform when in the delivery configuration. The retention element self expands to the shape shown in  FIG. 19F , which may be characterized as a “T”-shape, when removed from the delivery configuration. When deployed, the occlusion device shown in  FIG. 19F  is positioned such that the septum secundum  304  and septum primum  306  are secured between the radially expanded section  611  and the anchor element  602 , as described below.  
       FIG. 19G  illustrates another embodiment of an occlusion device  600  formed from a sheet of Nitinol having been electroformed or electroetched to form an unexpanded retention element  604 , an anchor element  602 , with an elongate body portion  642  therebetween. Cross-sections of this device are shown in  FIGS. 19I and 19J . In  FIG. 19H , the sheet of Nitinol has been shape set to assume a substantially tubular configuration in the vicinity of the retention element  604 . Cross-sections of this device are shown in  FIGS. 19K and 19L . Further shape setting can establish an expanded retention element with self-expanding characteristics.  
      As shown in  FIG. 19A , the overall width W of the occlusion device  600  may be any value or range of values from about 10 mm to about 50 mm and, in one more preferred embodiment, is about 2.5 cm in its expanded state. In other embodiments, the overall width W of the occlusion device  600  may be significantly less than about 10 mm or greater than about 50 mm. The overall length L of the occlusion device  600  from the distal end to the proximal end in one embodiment may be any value or range of values from about 4 mm to about 20 mm and, in one more preferred embodiment, is about 8 mm in its expanded state. In other embodiments, the overall length L of the occlusion device  600  may be significantly less than about 4 mm or greater than about 20 mm. The occlusion device  600  is preferably small enough to fit into a percutaneous catheter in its compressed state. In one embodiment, the occlusion device in its compressed state is small enough to fit in a percutaneous catheter having a diameter from about 5 to about 12 Fr. In other embodiments, catheter having diameters of other sizes may be used. For example, catheters may be used having diameters of less than about 5 Fr. and greater than about 12 Fr.  
      In use, a delivery device, such as delivery device  300  described herein, may be used to deliver the occlusion device  600  to a treatment site. The method of delivery of the delivery catheter described in  FIGS. 6-11  may be generally used to deliver occlusion device  600  such as shown in  FIG. 19A . Once the anchor element  602  is delivered to the treatment site, the retention element  604  may be expanded. In one embodiment, the retention element  604  self-expands to its expanded state when the retention element  604  is pushed out of the delivery catheter (or a tissue piercing structure as described above, if used). In one embodiment, the retention element  604  is delivered by compressing the distal and proximal ends of the retention element toward one another. The compression may be accomplished with a pull wire, push wire, torque rod, and the like.  FIG. 21  shows the occlusion device  600  delivered at a treatment site.  
      Occlusion device  600  is particularly advantageous because the self-expanding retention element  604  allows the device to be engineered to accommodate a wide range of septal wall thicknesses, thus reducing the need to pre-measure wall thickness and choose an appropriately sized occluder. Also, retention element  604  provides a long-acting clamping force between the retaining portion  608  and retaining elements  604 . The long-acting force assists with tissue growth and/or scarring between the septum secundum  304  and septum primum  306  by maintaining close apposition between the surfaces, particularly in the vicinity of elongate body portion  642  where tissue penetration has occurred and a healing response is expected.  
      In another embodiment, as shown in  FIGS. 22A and 22B , an occlusion device  700  having an anchor element  702  and a retention element  704  may be provided. The anchor element  702  has an elongate body portion  706  and a retaining portion  708 . In one embodiment, the longitudinal axis x of the elongate body portion  706  is perpendicular to the longitudinal axis y of the retaining portion  708 . In some embodiments, the angle between the longitudinal axis x of the elongate body portion  706  and the longitudinal axis y of the retaining portion  708  may vary. In some embodiments, the angle between the axis x and the axis y may be any value or range of values between about 15 and 165 degrees. In another embodiment, the angle value or range of values can vary below about 15 degrees and above about 165 degrees. The anchor element  702  may have a circular, rectangular, or other shaped cross-section, depending upon the manufacturing technique.  
      The retention element  704  has tubular body  709  having at least two longitudinal openings  711 , as shown in  FIG. 22A . In an embodiment having two openings as shown in  FIG. 22A , a second opening is provided at approximately 180 degrees from the opening shown. However, it is envisioned that more than two openings may be used. In some embodiments, each of the at least two openings are positioned equiangularly. When the tubular body  709  is axially compressed, the region of the tubular body having the at least two longitudinal openings  711  expands radially, as shown in  FIG. 22B . The retention element  704  may also include an attachment element  713  for releasably attaching the occlusion device  700  to a delivery device (not shown). The retention element  704  also includes a tissue ingrowth element  715 .  
      It may be desirable to enable tissue ingrowth in the vicinity of the occlusion device  700 , such that the device can be scarred over or incorporated into the surrounding tissue. Furthermore, it may be desirable to stimulate scarring of the septum secundum  304  and septum primum  306  such that they become grown into permanent attachment with one another, thereby reducing the risk of emboli passing through the PFO into the arterial circulation.  
      A Dacron, polyester, or other tissue growth prompting material may be used with the implant. In one embodiment, the tissue ingrowth element  715  may be a thread, a strip, a series of stands or the like, such that the tissue ingrowth element  715  fits within or near the vicinity of occlusion device  700  but does not interfere with delivery or implantation of the device.  
      As an alternative to or in combination with the tissue ingrowth element, the occlusion device  700  may be coated with a thin layer of a tissue ingrowth material, such as collagen, polyester, ceramic, and the like. In one embodiment, at least a portion of occlusion device  700  may be coated with a fabric comprising the tissue ingrowth material. In one embodiment, the occlusion device  700  may comprise a coating over at least a portion of the anchor element  702 , the elongate body portion  706  and/or the retention element  704 .  
      In one embodiment, the occlusion device may be made of polyester, having a roughened surface, thereby achieving tissue ingrowth post-implant.  
      In one embodiment, the occlusion device  700  may be made from a medical plastic or a metal, such as stainless steel, Nitinol, Elgiloy®, or others which can be determined through routine experimentation by those of skill in the art. In another embodiment, the occlusion member  700  may be made of a dissolvable suture material. The occlusion device  700  may also be biodegradable. It is also envisioned that other metallic or non-metallic biocompatible materials may be used to form occlusion device  700 .  
      In another embodiment, as shown in  FIGS. 23A and 23B , a delivery device  800  having a stabilization element  821  may be provided for stabilizing a delivery catheter in the left or right atrium. Stabilization of the delivery catheter may improve location of a treatment site. The stabilization element  821  may be collapsed to a transluminal delivery configuration and expanded to a stabilizing configuration. In one embodiment, the stabilization elements  821  may be expanded to a stabilizing configuration in the right atrium of the heart. In another embodiment, the stabilization elements  821  may be expanded to a stabilizing configuration in the left atrium of the heart. In still other embodiments, the stabilization elements  821  may be expanded in another chamber of the heart or passageway, such as a ventrical or vessel. In some embodiments, the stabilization elements  821  are expanded to contact the inner wall of the left atrium and the distal end of the sheath  827  is relatively constantly positioned in relation to a treatment location, such as a patent foramen ovale.  
      In one embodiment, the stabilization element  821  comprises a plurality of self-expanding struts  823 . Any number of struts may be used. In some embodiments, at least three struts are used. Struts  823  may be attached at a proximal end to catheter body  831  and at a distal end to sheath  827 . The struts  823  may be symmetrically arranged around sheath  827  as shown in  FIG. 23B . In another embodiment, the struts may be asymmetrically arranged around sheath  827 , as shown in  FIG. 23C . The particular asymmetrical orientation may vary from the embodiment shown in  FIG. 23C . In some embodiments, the stabilization element  821  may be made from braided strands. In other embodiments, the stabilization element  821  may be a balloon with an inflation tube affixed thereto, as known to those of skill in the art.  
      Sheath  827  may also include at least one radiopaque marker band  828 . Radiopaque marker  828  may be made from platinum, gold, iridium or the like. In some embodiments, the radiopaque marker may include a region of radiopaque filler in the sheath material. The filler may be made from barium sulfate, bismuth subcarbonate, tungsten powder, or other materials as are commonly employed in the art. Sheath  827  and/or catheter body  831  may also be reinforced with metallic braids or other materials as is commonly known in the art for improving torsional stiffness to the tubular shafts.  
      In one embodiment, the stabilization element  821  may be made from a medical plastic or a metal, such as stainless steel, Nitinol, Elgiloy®, or others which can be determined through routine experimentation by those of skill in the art. In another embodiment, the stabilization element  821  may be made of a dissolvable suture material. The stabilization element  821  may also be biodegradable. It is also envisioned that other metallic or non-metallic biocompatible materials may be used to form stabilization element  821 .  
      In some embodiments, the inner diameter of the delivery device  300 , described above, is sized to permit passage of the delivery device  800 . In one embodiment, the device may delivered from the left atrium to the right atrium, and used with the delivery catheter as discussed with reference to  FIG. 18 .  
      In use, the stabilization element  821  may self-expand. In another embodiment, the stabilization element  821  may expand by compressing the ends of the stabilization element  821 . For example, the distal end  825  of the stabilization element  821  may be attached to a sheath  827  at the distal end of the delivery device  800 . The distal end  825  may be welded or bonded or crimped or otherwise affixed to the sheath  827 . The proximal end  829  of the stabilization element  821  may similarly be attached to the catheter body  831 . By moving the sheath or catheter relative to one other, the stabilization element  821  expands. In an alternative embodiment, self-expanding stabilization elements  821  are attached at both ends to the distal portion of a catheter body, and an outer sleeve slideably receives the catheter body. Proximally retracting the sleeve will allow the stabilizer elements to self-expand. Stabilization elements of this type can also be incorporated onto the device shown in  FIG. 18 .  
      After the stabilization element  821  is expanded, a delivery device, such as delivery device  300 , may be passed through the delivery device  800  for delivering an occlusion device to a treatment site. In some embodiments, sheath  827  is sized to at least partially, slideably receive delivery system  300  or the delivery system as disclosed with reference to  FIG. 18 .  
      In some embodiments, the delivery device  800  may be percutaneously delivered to the right atrium using the catheter techniques described herein. Stabilization element may be expanded and collapsed, rotated, and re-expanded until the tip of the delivery device  800  is suitably located near to the treatment site. A radiopaque marker or radiopaque dye injection may be used to visualize the delivery device  800  at the treatment site. An occlusion device delivery system, such as device  300 , may slideably pass through the delivery device  800  for delivering an occlusion device to a treatment site.  
      In accordance with another embodiment of the present invention, as shown in  FIGS. 24-31 , an occlusion device comprising a spring clip may be provided to secure the defect. The occlusion device preferably comprises a wire shaped to form a clip. In some embodiments, the wire may be Nitinol. Although the device is shown having a clip shape, it is envisioned that a number of variations of this shape can be utilized to provide the same results. For example, a bend may be provided in the device to aid in closure. Also, annular, non-circular or round shapes may be used.  
      As shown in  FIG. 25 , the occlusion device  900  has a proximal end  902  and a distal end  904 . The designation “proximal” indicates the position of the device closest to the operator when the device is within the deployment catheter and is used for description purposes only and is not intended to designate a preferred or required orientation or arrangement.  
      As shown in  FIGS. 24 and 25 , the occlusion device  900  generally has three sections: a proximal segment  906 , a distal segment  908 , and an intermediate segment or occlusion segment  910 . The segments,  906 ,  908 ,  910  are formed from wire  912 . The segments  906 ,  908 ,  910  form an integral structure for occluding a patent foramen ovale. The occlusion device  900  is also preferably provided with a detachment element  914  at its proximal end  902 . Alternatively, the proximal end  902  of the device  900  may be provided with a threaded aperture through which a delivery core is threadably engaged, as described with respect to  FIG. 17 .  
      The intermediate segment  910  is positioned between the septum secundum  304  and the septum primum  306  to close the patent foramen ovale  302 , as shown in  FIGS. 29A and 29B . The proximal segment  906  is positioned in the right atrium, while the distal segment  908  is positioned in the left atrium.  
      In one embodiment, occlusion device  900  may be delivered to the patent foramen ovale  302  in its expanded state (see  FIG. 29A ), and then compressed to secure the patent foramen ovale  302  in a closed position (see  FIG. 29B ). In one embodiment, the occlusion device  900  may be biased to spring to the closed position upon delivery. In one embodiment, the occlusion device  900  may be compressed under positive force to close the occlusion device  900 .  
      The occlusion device  900  is designed to be implanted using a delivery catheter. The device may be designed to be delivered in an elongated state or remain in a collapsed state while in the catheter. As shown in  FIGS. 24A, 24B , all or a portion of the Nitinol wire clip may be straightened for delivering through a catheter  922 . In this embodiment, the Nitinol wire clip has preferably been heat treated to its clip shape such that this shape is remembered after exiting the delivery catheter. The detachment element  914  on the occlusion device can be releasably attached to a push rod  918 , which is adapted to push the occlusion device out of the end of the catheter. Upon delivery to the patent foramen ovale, the device  900  is positioned and expanded to occlude the patent foramen ovale.  FIG. 25  shows the device in a partially expanded state. The procedure for placing the occlusion device and delivery device will be described in further detail hereinafter.  
       FIGS. 26 and 27  show an alternative embodiment of a clip-like occlusion device.  FIG. 26  is a schematic view of occlusion device  950 .  FIG. 27  is a side view showing occlusion device  950 . Occlusion device  950  generally has three sections: proximal segments  956 , a distal segment  960 , and intermediate segments or occlusion segments  958 . The segments,  956 ,  958 ,  960  are formed from wire  912 . The segments  956 ,  958 ,  960  form an integral structure for occluding a patent foramen ovale. The occlusion device  950  is also preferably provided with detachment elements provided at the proximal end of the proximal segments  956 , as previously discussed with respect to other embodiments. Alternatively, the device  950  is provided with at least one threaded aperture through which a delivery core is threadably engaged. The distal segments  958  are joined at an apex  959 .  
       FIG. 28  shows a delivery device  922  for delivering the occlusion device  950 . Occlusion device  950  is elongated and positioned in catheter  922 , such that apex  959  is distal to proximal segments  956 , intermediate segments  958 , and distal segment  960 . In some embodiments, the device may be biased to self-expand upon delivery at the patent foramen ovale. In other embodiments, the device may be compressed upon delivery at the patent foramen ovale. The occlusion device  950  may be releasably attached to the push rod  918  using any suitable mechanism, such as a suture line, threading, etc. In some embodiments, occlusion device  950  may be attached to a push rod  918 , using detachment elements similar to those described with reference to  FIGS. 12 and 13 .  
      As shown in  FIG. 29A , the intermediate segments  958  are positioned between the septum secundum  304  and septum primum  306 , the distal segment  960  is positioned against the septum primum  306 , and the proximal segments are positioned against the septum secundum  304  to close the patent foramen ovale  302 , as shown in  FIG. 29B .  
      In one embodiment, occlusion device  950  may be delivered to the patent foramen ovale  302  in an elongated state (see  FIG. 29C ), wherein the occlusion device  950  is essentially elongated. The occlusion device  950  is then manipulated to secure the patent foramen ovale  302  in a closed position as the wire is advanced from the delivery device  922  (see  FIG. 29D ). In one embodiment, the occlusion device  950  may be biased to spring to the closed position upon delivery. Alternatively, the occlusion device  950  may be compressed under positive force to close the occlusion device  950 .  
      Preferably, the wire  912  comprises a metal such as stainless steel, Nitinol, Elgiloy®, or others which can be determined through routine experimentation by those of skill in the art. The wire may also be biodegradable. Wires having a circular, rectangular or other cross-section may be utilized depending upon the manufacturing technique. In one embodiment, a circular cross section wire is cut such as by known laser cutting techniques from tube stock. The occlusion device is preferably an integral structure, such as a single ribbon or wire, or element cut from a tube or sheet stock. It is also envisioned that other metallic or non-metallic biocompatible materials may be used to form wire  912 . In one embodiment, the wire  912  may be a shape memory material.  
      With reference to  FIG. 26 , the device  900 ,  950  has an expanded width W having any value or range of values from about 0.005 in to about 0.375 in, and, in one more preferred embodiment, about 0.25 in. In some embodiments, the device  900 ,  950  may have an expanded width W of significantly less than about 0.005 in or greater than about 0.375 in. The overall length L of the occlusion device  900 ,  950  from the distal end  904  to the proximal end  902  (when straightened) in one embodiment is any value or range of values from about 0.6 to 2.5 inches, and the folded (as implanted length) is about 0.2 to 0.75 inches. In some embodiments, the overall length L when straightened may be significantly less than about 0.6 in or greater than about 2.5 inches, and the implanted length may be significantly less than about 0.2 in or greater than about 0.75 in. In some embodiments, the wire has a diameter of any value or range of values between 0.005-0.040 in, and, in one some preferred embodiments, any value or range of values between 0.008-0.020 in. In some embodiments, the wire diameter may be significantly less than about 0.005 in or greater than about 0.020 in.  
      In some embodiments, radiopaque markers may be provided on the occlusion device  900 ,  950  to aid in placement at the treatment site. In some embodiments, the radiopaque markers are crimped on to the occlusion device. In one embodiment, the radiopaque markers are tubular bands crimped on to the occlusion device. In some embodiments, the radiopaque markers are coatings applied to the device or core wires within the wire  912 . In some embodiments, the radiopaque markers may be platinum or iridium, and the like.  
      With reference to  FIG. 30 , a guide wire  920  may be delivered between the septum secundum  304  and septum primum  306 . A delivery device  922  is then delivered over the guide wire  920  to a septal defect  302 . The delivery device  922  is preferably advanced between the septum secundum  304  and septum primum  306 . The guide wire  920  may be removed. The occlusion device  900 ,  950  is delivered to the patent foramen ovale, by advancing at least a portion of the occlusion device  900 ,  950  out of the delivery device  922 , as shown in  FIG. 29C . Alternatively, occlusion device  900 ,  950  may be delivered such that a portion  908 ,  958 ,  959 , and/or  960  of the occlusion device extends out of the delivery device  922 , thereby eliminating or reducing advancement of the occlusion device out of the delivery device  922 . Further advancement of occlusion device  900 ,  950  out of catheter  922  causes distal segment  908 ,  960  to return to a shape set shape in contact with septum primum  306 , as shown in  FIG. 29D . In one embodiment, by pulling the occlusion device  900 ,  950  and delivery device  922  proximally, the distal segment  908 ,  960  of the occlusion device  900  is secured over the septum primum  306 , as shown in  FIGS. 29A, 29B , and  29 D. The occlusion device  900 ,  950  is released from the delivery device  922  by retracting the delivery catheter while holding the push rod  918  stationary and releasing push rod  918  from detachable element  914 , such that proximal segment  906 ,  956  returns to a pre-set shape and becomes secured over the septum secundum  304 . Alternatively, the delivery device  922  is removed from occlusion device  900  after delivery of the occlusion device  900  to a final position wherein proximal segment  906 ,  956  is in contact with the septum secundum  304  by detachment of pull rod  918  from detachment element  914 .  
      An adjustable occlusion device  1000  may be provided for adjusting to the specific anatomy at the treatment site, as shown in  FIG. 31 . The adjustable occlusion device  1000  may include a first element  1002  and a second element  1004  which may be adjustable relative to one another. The first element  1002  and the second element  1004  combine to form three sections: a proximal segment  1006 , a distal segment  1008 , and an intermediate segment or occlusion segment  1010 . As shown in  FIG. 31 , the adjustable aspects of the device are preferably provided at the occlusion segment  1010 , where the first element  1002  and second element  1004  join together. In one embodiment, the first element  1002  and second element  1004  may be telescoping. In one embodiment, the adjustable elements may include locking elements or tines (not shown) to lock the first element and second element in place at a desired adjusted location.  
      In accordance with another embodiment of the present invention, an occlusion device  1100  comprising a rotatable retention element may be provided. In one embodiment, rotatable retention element  1102  may have a left-handed threading, as shown in  FIG. 32 . In one embodiment, rotatable retention element  1104  may have a right-handed threading, as shown in  FIG. 33 . In some embodiments, the rotatable retention elements  1102 ,  1104  may be a coil  1106  having a pointed or sharpened end  1108  to penetrate tissue. The device  1100  may have a detachable element  1114  provided at the proximal end of the coil  1106 . In some embodiments, the coil  1106  may have a variable pitch or more than one pitch.  
      In one embodiment, the occlusion device  1100  may be made from a medical plastic or a metal, such as stainless steel, Nitinol, Elgiloy®, or others which can be determined through routine experimentation by those of skill in the art. In another embodiment, the occlusion member  1100  may be made of a dissolvable suture material. The occlusion device  1100  may also be biodegradable. It is also envisioned that other metallic or non-metallic biocompatible materials may be used to form occlusion device  1100 .  
       FIGS. 34A and 34B  show occlusion device  1100  implanted at the foramen ovale. The occlusion device  1100  may be delivered to the foramen ovale using an occlusion device delivery system  1122  comprising a catheter having a rotatable actuator. The occlusion device  1100  may be rotated through the septum secundum  304  and septum primum  306 , drawing the septum together to close the patent foramen ovale  302 , as shown in  FIG. 34A . In some embodiments, occlusion device  1100  may have a coil  1106  with closer coil spacing near the proximal end of the device than near the distal end of the device (not shown), so that rotation of the coil  1106  tends to draw the septa together. Although the occlusion device  1100  is shown delivered from the right atrium, it may alternatively be delivered from the left atrium. In one embodiment, the occlusion device  1100  may be rotated through the septum secundum  304  and septum primum  306  from between the septum  304 ,  306 , as shown in  FIG. 34B .  
      In another embodiment, an occlusion device may be delivered from between the septum secundum  304  and septum primum  306 , and pull the septa together. In some embodiments, the occlusion device may include a single loop having sharp ends and retention elements, as described below. The loop may be pushed axially through a catheter to transversely engage the septa.  
      Referring to  FIG. 35A , an occlusion device  1300  having an apex  1302  and at least two loops  1304  is provided. The distal end of loop  1304  may be sharpened to penetrate tissue. The loop  1304  may include a retention element  1306 . In some embodiments, the retention element  1306  is a barb configured to resist withdrawal from a septum once the barb has engaged the septum.  
      The occlusion device  1300  may be made from a medical plastic or a metal, such as stainless steel, Nitinol, Elgiloy®, or others which can be determined through routine experimentation by those of skill in the art. In some embodiments, the device may be biased to self-expand upon delivery at the patent foramen ovale. In another embodiment, the occlusion device  1300  may be made of a dissolvable suture material. In some embodiments, the occlusion device  1300  may also be biodegradable. It is also envisioned that other metallic or non-metallic materials may be used to form occlusion device  1300 .  
      In some embodiments, the occlusion device  1300  may be heat-treated to its “clip” shape, such that the occlusion device is biased to expand to the “clip” shape when it exits the delivery catheter.  
      As shown in  FIG. 35B , all or a portion of the occlusion device  1300  may be generally straightened for delivering the device through a catheter  1325 . The delivery system  1325  may be used to deliver occlusion device  1300  to a treatment location such as a patent foramen ovale. The delivery system  1325  contains an outer catheter  1327 , an inner push tube  1329 , and a thread  1331 . The delivery system  1325  may also contain channels  1333  that can be used to guide loops  1304  in a direction transverse to the longitudinal axis of catheter  1327 .  
      The occlusion device  1300  may be releasably attached to the push rod  1329  using any suitable mechanism, such as a suture line, threading, and the like. In some embodiments, the occlusion device  1300  may be attached to push rod  1329  using detachment elements similar to those described with reference to  FIGS. 12 and 13 . Upon delivery to the patent foramen ovale, the occlusion device  1300  is advanced out of catheter  1325  to draw the septum secundum  304  and septum primum  306  in close apposition.  
      Catheter  1327  may be manufactured in accordance with any of a variety of techniques. In one embodiment, the catheter  1327  may be extruded from any of a variety of materials, such as HDPE, PEBAX®, nylon and PEEK™. In some embodiments, at least a portion of or all of the length of the catheter body may comprise a spring coil, solid walled hypodermic needle or other metal tubing, or a braided reinforced wall, as are known in the art. The spring coil, tubing, braided reinforcement, or other structures may be encapsulated with thermoset polymers such as polyimide and the like or with thermoplastic polymers such as PEBAX® and the like.  
      The push tube  1329  desirably has good column strength. Push tube  1329  may be formed from any of a variety of ways, such as a spring coil, solid walled hypodermic needle or other metal tubing, or a braided reinforced wall, as are known in the art. The spring coil, tubing, braided reinforcement, or other structures may be encapsulated with thermoset polymers such as polyimide or thermoplastic polymers such as PEEK™, and the like.  
      The thread  1331  may be manufactured from a variety of high strength flexible materials such as metal wire or cable, Kevlar, polyester thread, oriented ultra-high molecular weight polyethylene, and the like.  
       FIG. 35C  shows a cross-section of catheter  1327 . Catheter  1327  includes a first half  1335  and second half  1337 . First half  1335  slides axially relative to second half  1337 . Second half  1337  may contain channels  1333  and a lumen  1339  for push tube  1329 . First half  1335  and second half  1337  may be held together by one or more collars  1341  (see  FIG. 36B ) that can be used to guide loops  1304  in a direction transverse to the longitudinal axis of catheter  1327 .  
      The occlusion device  1300  may be loaded into the catheter  1325  by axially sliding the first half  1335  relative to the second half  1337 , exposing channels  1333 . Thread  1331  may be looped through apex  1302  and tensioned to secure the occlusion device  1300  to push tube  1329 . Thread  1331  and push tube  1329  are proximally withdrawn to load occlusion device  1300  into catheter  1325 . When the occlusion device is loaded, the retention elements  1306  are contained within channels  1333 . First half  1335  axially slides relative to second half  1337  to secure occlusion device  1300  in channels  1333 .  
       FIG. 36A  shows the delivery of occlusion device  1300  into septum secundum  304  and septum primum  306 . Catheter  1327  is advanced into a foramen ovale such that channels  1333  are located adjacent to the septum secundum  304  and septum primum  306 . Push rod  1329  is distally advanced to cause retention elements  1306  to penetrate the septa. Thread  1331  may be proximally withdrawn to disengage apex  1302  from push tube  1329 . Delivery device  1325  may be proximally withdrawn to allow occlusion device  1300  to draw the septum secundum  304  and septum primum  306  together, thereby closing and sealing the patent foramen ovale  302 . See  FIG. 36B .  
      In another embodiment, an occlusion device may be delivered between the septum secundum  304  and septum primum  306 , preventing the septa from separating, thereby preventing a blood clot or other emboli from traversing a patent foramen ovale and entering the patients arterial circulation. An occlusion device having sharp ends and retention elements is provided. The device may be pushed axially through a catheter and delivered such that the device transversely engages the septa.  
      Referring to  FIGS. 37A and 37B , an occlusion device  1400  comprises an elongate body  1402 , an opening  1404 , and retention elements  1406  and  1410 . First end  1408  and second end  1409  may be sharpened to penetrate tissue. The elongate body may include retention elements  1406 . In some embodiments, the retention element  1406  is a barb configured to resist withdrawal from a septum once the barb has engaged the septum. Occlusion device  1400  may also include retention elements  1410 . Retention elements  1410  may be configured to engage the septa and resist withdrawal from a septum once the barb has engaged the septum. In some embodiments, retention elements  1410  are barbs, and may be biased to spring out from the surface of elongate body  1402  to engage the septum. Occlusion device  1400  may also include a pivot or pin  1412 , as will be described hereinafter.  
      Occlusion device  1400  may be made from any of a variety of materials, such as a medical plastic or a metal, such as stainless steel, Nitinol, Elgiloy®, or other materials that can be determined through routine experimentation by those of skill in the art. In one embodiment, the occlusion device is laser cut from a Nitinol tube. In some embodiments, the device may be biased to self-expand upon delivery at the patent foramen ovale. In another embodiment, the occlusion device may also be biodegradable. In some embodiments, other metallic or non-metallic biocompatible materials may be used to form occlusion device  1400 .  
      Referring to  FIG. 37C , a delivery system  1425  may be used to deliver occlusion device  1400  to a treatment site such as a patent foramen ovale. Delivery system  1425  includes a catheter  1427 , a push tube  1429 , and thread  1431 . The occlusion device  1400  may be delivered through a catheter  1427 . The occlusion device  1400  may be releasably attached to a push tube  1429  using any suitable mechanism, such as thread  1431  looped around a pivot  1412 . Upon delivery to the patent foramen ovale, the occlusion device  1400  is pushed out of catheter  1427  to engage the septum secundum  304  and septum primum  306 .  
      To load the occlusion device  1400  into delivery device  1425 , thread  1431  may be looped around pivot  1412  of occlusion device  1400  and both ends of thread  1431  may be drawn through the interior of push tube  1429 . The proximal end of push tube  1429  is loaded into the distal end of catheter  1427 , and the slotted end of elongate body  1402  is advanced into the distal end of catheter  1427  while applying tension to thread  1431  to secure the occlusion device  1400  adjacent to push tube  1429 . Optional retention elements  1429  at the non-slotted end of the elongate body  1402  may be radially compressed to facilitate their introduction into catheter  1427 . Thread  1431  and push tube  1429  are drawn proximally together to fully load occlusion device  1400  into catheter  1427 . When loaded, retention elements  1410  may be elastically compressed within the lumen of catheter  1427 .  
      Catheter  1427  may be manufactured in accordance with any of a variety of techniques. In one embodiment, the catheter  1427  may be extruded from any of a variety of materials, such as HDPE, PEBAX®, nylon and PEEK™. In some embodiments, at least a portion of or all of the length of the catheter body may comprise a spring coil, solid walled hypodermic needle or other metal tubing, or a braided reinforced wall, as are known in the art. The spring coil, tubing, braided reinforcement, or other structures may be encapsulated with thermoset polymers such as polyimide and the like or with thermoplastic polymers such as PEBAX® and the like.  
      The push tube  1429  desirably has good column strength. Push tube  1429  may be formed from any of a variety of ways, such as a spring coil, solid walled hypodermic needle or other metal tubing, or a braided reinforced wall, as are known in the art. The spring coil, tubing, braided reinforcement, or other structures may be encapsulated with thermoset polymers such as polyimide or thermoplastic polymers such as PEEK™, and the like.  
      The thread  1431  may be manufactured from a variety of high strength flexible materials such as metal wire or cable, Kevlar, polyester thread, oriented ultra-high molecular weight polyethylene, and the like.  
      FIGS.  37 C-F show a method of delivering occlusion device  1400  to the septum secundum  304  and septum primum  306 . Delivery device  1425  is advanced to a patent foramen ovale, such that occlusion device  1400  is located adjacent the septum secundum  304  and septum primum  306 . Catheter  1427  is proximally withdrawn while holding push tube  1429  and thread  1431  stationary to fully expose occlusion device  1400 .  
      Thread  1431  passes through slot  1404  to allow full exposure of occlusion device  1400 . Both ends of thread  1431  are withdrawn proximally while holding push tube  1429  stationary to cause the proximally sloped end  1440  of the elongate body  1402  to slide against the distally sloped end  1442  of the push tube  1429 , thereby causing the occlusion device  1400  to pivot relative to catheter  1427  and push tube  1429 . Further proximal retraction of both ends of thread  1431  causes occlusion device to continue to rotate relative to axis of catheter  1427  until retention element  1406  penetrates into the septum secundum  304 . Delivery device  1425  may be partially proximally withdrawn to assist in engaging retention element  1406  with septum secundum  304 . Distal retention element  1406  engages with the septum primum  306  when the distal retention element  1406  is exposed. Delivery device  1425  may be partially proximally withdrawn to assist in engaging distal retention element  1406  with the septum primum  306 , using the elasticity of the septa to advancing in engaging the retention elements. Improved engagement of optional retention elements  1420  may be achieved by proximally and distally moving the delivery device  1425 . Thread  1431  may be proximally withdrawn to disengage from pivot  1412  by proximally pulling one end of thread  1431  from push tube  1429 . Delivery device  1425  may be proximally withdrawn from the patient, leaving occlusion device  1400  in place to prevent separation of the septum secundum  304  and septum primum  306 .  
      Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while a number of variations of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed invention. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.