Patent Publication Number: US-2004049210-A1

Title: Filter apparatus for ostium of left atrial appendage

Description:
[0001] This application is a divisional of application Ser. No. 09/642,291, filed Aug. 18, 2000, which is a continuation-in-part of application Ser. No. 09/614,091, filed Jul. 11, 2000, which is a continuation-in-part of application Ser. No. 09/428,008, filed Oct. 27, 1999, (now U.S. Pat. No. 6,551,303) all of which are incorporated by reference in their entirety herein. The application Ser. No. 09/614,091, filed Jul. 11, 2000 also claims the benefit of U.S. provisional application No. 60/196,454, filed Apr. 11, 2000, U.S. provisional application No. 60/206,967, filed May 25, 2000, U.S. provisional application No. 60/209,511, filed Jun. 5, 2000, and U.S. provisional application No. 60/211,896, filed Jun. 16, 2000. The application Ser. No. 09/642,291, filed Aug. 18, 2000 also claims the benefit of U.S. provisional application No. 60/196,454, filed Apr. 11, 2000, U.S. provisional application No. 60/206,967, filed May 25, 2000, U.S. provisional application No. 60/209,511, filed Jun. 5, 2000, U.S. provisional application No. 60/211,896, filed Jun. 16, 2000, and U.S. provisional application No. 60/217,125, filed Jul. 10, 2000, all of which are incorporated by reference in their entirety herein. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The invention relates to a membrane structure applied to or across the ostium of an atrial appendage to prevent a thrombus from leaving the atrial appendage.  
       [0004] 2. Description of the Related Art  
       [0005] There are a number of heart diseases (e.g., coronary artery disease, mitral valve disease) that have various adverse effects on the heart. An adverse effect of certain cardiac diseases, such as mitral valve disease, is atrial (or auricular) fibrillation. Atrial fibrillation may result in pooling of blood in the left atrial appendage. Blood pooling may also be spontaneous. When blood pools in the atrial appendage, blood clots can form and accumulate therein, build upon themselves, and propagate out from the atrial appendage into the atrium. These blood clots can then enter the systemic or pulmonary circulations and cause serious problems if they migrate from the atrial appendage and become free in the blood stream and embolize distally into the arterial system. Similar problems also occur when a blood clot extending from an atrial appendage into an atrium breaks off and enters the blood supply. Since blood from the left atrium and ventricle supply the heart and brain, blood clots from the atrial appendages can obstruct blood flow therein causing heart attacks, strokes or other organ ischemia. It is therefore necessary to find a means of preventing blood clots from forming in the atrial appendages and to prevent these blood clots, once formed, from leaving the atrial appendages to the heart, lungs, brain or other circulations of the patient which can cause heart attacks or strokes or other organ ischemia.  
       [0006] U.S. Pat. No. 5,865,791 relates to the reduction of regions of blood stasis and ultimately thrombus formation in such regions, particularly in the atrial appendages of patients with atrial fibrillation. More specifically, the &#39;791 patent relates to procedures and devices for affixing the atrial appendages in an orientation that prevents subsequent formation of thrombus. In the &#39;791 patent, the appendage is removed from the atrium by pulling on it and by putting a loop around it to form a sack of the atrial appendage and then cutting it off from the rest of the heart.  
       [0007] U.S. Pat. No. 5,306,234 relates to a method for surgically closing the passage between the atrium and the atrial appendage or severing the atrial appendage.  
       [0008] Other methods of treatment include surgically removing the atrial appendages to prevent blood stasis in the atrial appendages.  
       SUMMARY OF THE INVENTION  
       [0009] The invention provides a membrane that substantially prevents blood clots formed in the atrial appendages from exiting therefrom. Such clots may cause heart attacks, strokes and other embolic events if allowed to leave the atrial appendage and enter the bloodstream. The membrane is permanently positioned across the ostium of the atrial appendage by direct securement means to the ostium or the atrial wall adjacent the ostium.  
       [0010] The membrane effectively isolates blood clots inside the left atrial appendage from leaving and entering the atrium. It may be larger than the ostium of the appendage, and extend over an area larger than the ostium. The membrane may be percutaneously delivered to the ostium of the atrial appendage by a catheter and then may be expanded for positioning across or over the ostium.  
       [0011] According to one embodiment, the membrane is impermeable to blood flow. This membrane inhibits thrombus in the left atrial appendage from exiting and entering the bloodstream. The membrane also prevents blood from flowing into or out of the left atrial appendage.  
       [0012] According to another embodiment, the membrane itself is permeable to permit blood flow across the membrane. By allowing the such blood flow across the membrane, the permeable structure minimizes any pressure gradient between the atrial appendage and the atrium in a controlled manner. Moreover, the permeable membrane acts as a filter in allowing blood to flow across, but substantially inhibits the passage of thrombus therethrough.  
       [0013] The permeable filtering membrane may eventually become infiltrated with cells. The permeable filtering membrane allows such tissue growth which may begin along the outer periphery of the structure. Such tissue growth minimizes uncontrolled leakage about the periphery of the filtering membrane and may assist in attachment of the filtering membrane across the ostium to tissue surrounding the ostium. The filtering membrane may be coated or covered with an anticoagulant or other compounds, such as, for example, heparin, or it may be treated to prevent thrombus from forming on the filtering membrane surface, to extend its patency or until it is infiltrated with cells and/or develops an endothelial covering.  
       [0014] There are many means for securing the membrane in position across the ostium of the atrial appendage. Direct securement means for the membrane may be provided by a biocompatible adhesive applied between the membrane and the ostium or the atrial wall. In this manner, the membrane can be adhered directly to the tissue. In another embodiment, direct securement is made by the use of staples, clips, sutures, wires, barbs, prongs or other methods of fixation which pass through the tissue of the ostium or atrial wall. In yet another embodiment, direct securement is achieved by the use of structure connected to the membrane which extends through the ostium and into the interior of the atrial appendage and engages the interior of the atrial appendage, wherein the interior wall of the atrial appendage may also include any portion of the ostium extending within the atrial appendage. The direct securement means may provide a self-centering feature for the membrane about the appendage ostium.  
       OBJECTS OF THE INVENTION  
       [0015] It is an object of the invention to provide a membrane between the atrium and atrial appendage to prevent blood clots from flowing therebetween.  
       [0016] It is an object of the invention to provide a membrane which is permanently implanted between the atrium and the atrial appendage by direct securement to the ostium or the atrial wall adjacent the ostium.  
       [0017] It is an object of the invention to provide a membrane between the atrium and the atrial appendage which is impermeable to blood flow or the passage of thrombus.  
       [0018] It is an object of the invention to provide a filtering membrane between the atrium and atrial appendage to allow blood flow across the filter, e.g., to reduce any hemodynamic pressure differential therebetween.  
       [0019] It is an object of the invention to prevent blood clots from forming in the atrial appendage.  
       [0020] It is an object of the invention to position across the ostium of the atrial appendage a non-thrombogenic, biocompatible surface that prevents blood clots from forming.  
       [0021] It is an object of the invention to provide a permeable filtering membrane surface which may eventually become lined with endothelial or endocardial cells.  
       [0022] It is an object of the invention to isolate the atrial appendage from the atrium proper with respect to the passage of thrombus with a filtering membrane, while allowing communication through which blood may flow.  
       [0023] It is an object of the invention to minimally invasively prevent blood clots from forming in the atrial appendages and escaping therefrom.  
       [0024] It is an object of the invention to prevent thrombus by use of heparin, other antithrombogenic substances, or other compounds on or eluted from the membrane.  
       [0025] It is an object of the invention to ensure the membrane is centered across or over the ostium of the atrial appendage.  
       [0026] It is an object of the invention to accurately place the membrane across or over the ostium of the atrial appendage.  
       [0027] Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0028]FIG. 1 is a partial cross sectional view of a heart showing a catheter entering the left atrial appendage using a retrograde procedure from the aorta in accordance with the invention.  
     [0029]FIG. 2 is a partial cross sectional view of a heart showing a catheter entering the left atrial appendage using a transeptal procedure from the femoral vein or superior vena cava in accordance with the invention.  
     [0030]FIG. 3 is a partial cross sectional view of a heart showing a catheter entering the right atrial appendage from the jugular vein or optionally from the femoral vein in accordance with the invention.  
     [0031]FIG. 4 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage.  
     [0032]FIG. 5 is a partial cross sectional view of a delivery catheter having a disk, a spring and membrane therein in accordance with the invention.  
     [0033]FIG. 6 is a schematic view of a disk, spring and membrane after being expanded out of the delivery catheter of FIG. 5 in accordance with the invention.  
     [0034]FIG. 7 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage having a disk, a membrane and a spring therebetween in accordance with the invention.  
     [0035]FIG. 8 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage shown in a collapsed position in accordance with the invention.  
     [0036]FIG. 9 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage having a disk, a spring, a membrane and vacuum in the catheter in accordance with the invention.  
     [0037]FIG. 10 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage showing an umbrella folded for entering the atrial appendage in accordance with the invention.  
     [0038]FIG. 11 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage showing the umbrella opened in the atrial appendage to secure the umbrella into the wall of the atrial appendage in accordance with the invention.  
     [0039]FIG. 12 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage showing the umbrella and membrane positioned across the ostium of the atrial appendage in accordance with the invention.  
     [0040]FIG. 13 is a partial cross sectional view of a portion of a heart showing an atrium and its associated atrial appendage showing the atrial appendage reduced to a minimum volume by a disk and spring squeezing the appendage against a membrane in accordance with the invention.  
     [0041]FIG. 14 is a perspective view of another embodiment of a filtering membrane and apparatus for installing the filtering membrane in accordance with the invention.  
     [0042]FIG. 15 is a sectional view of the filtering membrane and apparatus illustrated in FIG. 14, in accordance with the invention.  
     [0043]FIG. 16 is an enlarged view of a portion of the apparatus of FIG. 15 in accordance with the invention.  
     [0044]FIG. 17 is a partial cross-sectional view illustrating an early stage in the installation of the apparatus of FIG. 14, in accordance with the invention.  
     [0045]FIG. 18 is a partial cross-sectional view similar to FIG. 17, illustrating a later stage in the procedure in accordance with the invention.  
     [0046]FIG. 19 illustrates another embodiment of the filtering membrane and apparatus for installing the filtering membrane in accordance with the invention.  
     [0047]FIG. 20 is an enlarged view of the filtering membrane and apparatus illustrated in FIG. 19 in accordance with the invention.  
     [0048]FIG. 21 is a planar development of the apparatus for attaching the filtering membrane illustrated in FIGS.  19 - 20  in accordance with the invention.  
     [0049]FIG. 22 is an enlarged perspective view of a portion of the apparatus of FIG. 21, in accordance with the invention.  
     [0050]FIG. 23 is a planar development of the apparatus depicted in FIG. 21 in an expanded configuration, in accordance with the invention.  
     [0051]FIG. 24 is a perspective view of the filtering membrane and apparatus for attaching the filtering membrane of FIG. 20, illustrated in an expanded configuration in accordance with the invention.  
     [0052]FIG. 25 is an elevational view of an embodiment of the filtering membrane in accordance with the invention.  
     [0053]FIG. 26 is an elevational view of another embodiment of the filtering membrane in accordance with the invention.  
     [0054]FIG. 27 is an elevational view of yet another embodiment of the filtering membrane in accordance with the invention.  
     [0055]FIG. 28 is an elevational view of a further embodiment of the filtering membrane in accordance with the invention.  
     [0056]FIG. 29 is a partial cross-sectional view illustrating an early stage in the procedure of installing of the filtering membrane of FIGS.  19 - 28  in accordance with the invention.  
     [0057]FIG. 30 is a partial cross-sectional view similar to FIG. 29 illustrating a later stage in the procedure in accordance with the invention.  
     [0058]FIG. 31 is a partial cross-sectional view similar to FIG. 30 illustrating a still later stage in the procedure in accordance with the invention.  
     [0059]FIG. 32 is a view similar to FIG. 31 illustrating an alternative embodiment of the apparatus illustrated in FIGS.  19 - 23 .  
     [0060]FIG. 33 is a partial cross-sectional view similar to FIG. 32 illustrating a later stage in the procedure in accordance with the invention.  
     [0061]FIG. 34 is a partial cross-sectional view similar to FIG. 33 illustrating a still later stage in the procedure in accordance with the invention.  
     [0062]FIG. 35( a ) illustrates an alternative embodiment of the apparatus illustrated in FIGS.  19 - 20  in accordance with the invention.  
     [0063]FIG. 35( b ) illustrates the apparatus illustrated in FIG. 35( a ) in an expanded configuration in accordance with the invention.  
     [0064]FIG. 36 is a view similar to FIG. 35( b ) illustrating another embodiment in accordance with the invention  
     [0065]FIG. 37 illustrates yet another embodiment of the filtering membrane and apparatus for attaching the filtering membrane in accordance with the invention.  
     [0066]FIG. 38 is an elevational view taken from direction  38  of FIG. 37 in accordance with the invention.  
     [0067]FIG. 39 is elevational view taken from direction  39  of FIG. 37 in accordance with the invention.  
     [0068]FIG. 40 is a sectional view illustrating the apparatus of FIGS.  37 - 39  along with additional apparatus in accordance with the invention.  
     [0069]FIG. 41 is a partial cross-sectional view illustrating a first installed configuration of the apparatus of FIGS.  37 - 39  in accordance with the invention.  
     [0070]FIG. 42 is a partial cross-sectional view similar to FIG. 41 illustrating a second installed configuration of the apparatus of FIGS.  37 - 39  in accordance with the invention.  
     [0071]FIG. 43 is a partial cross-sectional view illustrating another embodiment of the apparatus in accordance with the invention.  
     [0072]FIG. 44 illustrates a further embodiment of the apparatus in accordance with the invention.  
     [0073]FIG. 45 is an end view of the apparatus of FIG. 44 in accordance with the invention.  
     [0074]FIG. 46 illustrates a still further embodiment of the apparatus in accordance with the invention.  
     [0075]FIG. 47 illustrates additional apparatus for use with the apparatus of FIGS.  44 - 46  in accordance with the invention.  
     [0076]FIG. 48 is an enlarged sectional view of the apparatus of FIG. 47 in accordance with the invention.  
     [0077]FIG. 49 is a partial cross-sectional view of the apparatus of FIGS.  44 - 45  illustrating an early stage in the procedure in accordance with the invention.  
     [0078]FIG. 50 is a partial cross-sectional view similar to FIG. 49 illustrating a later stage in the procedure in accordance with the invention.  
     [0079]FIG. 51 illustrates yet another embodiment of the apparatus in accordance with the invention.  
     [0080]FIG. 52 is an end view of the apparatus of FIG. 51 in accordance with the invention.  
     [0081]FIG. 53 illustrates additional apparatus for use with the apparatus of FIGS.  51 - 52  in accordance with the invention.  
     [0082]FIG. 54 is an enlarged sectional view of the apparatus of FIGS. 51 and 53 in accordance with the invention.  
     [0083]FIG. 55 is a partial cross-sectional view of the apparatus of FIG. 51 illustrating an early stage in the procedure in accordance with the invention.  
     [0084]FIG. 56 is a partial cross-sectional view similar to FIG. 55 illustrating a later stage in the procedure in accordance with the invention.  
     [0085]FIG. 57 illustrates another embodiment of the apparatus in accordance with the invention.  
     [0086]FIG. 58 illustrates yet another embodiment of the apparatus in accordance with the invention.  
     [0087]FIG. 59 is a partial cross-sectional view of the apparatus of FIG. 57 illustrating an early stage in the procedure in accordance with the invention.  
     [0088]FIG. 60 is a partial cross-sectional view similar to FIG. 59 illustrating a later stage in the procedure in accordance with the invention.  
     [0089]FIG. 61 is a simplified elevational view of another embodiment of the membrane in accordance with the invention.  
     [0090]FIG. 62 is a side view of the membrane taken from direction  62  of FIG. 61, in accordance with the invention.  
     [0091]FIG. 63 is view in partial section of the membrane of FIGS.  61 - 62  illustrating a typical use in accordance with the invention.  
     [0092]FIG. 64 is view in partial section of the yet another embodiment of the membrane, illustrating a typical use in accordance with the invention.  
     [0093]FIG. 65 is a simplified elevational view of still another embodiment of the membrane in accordance with the invention.  
     [0094]FIG. 66 is a side view of the membrane taken from direction  66  of FIG. 65, in accordance with the invention.  
     [0095]FIG. 67 is view in partial section of the membrane of FIGS.  65 - 66  illustrating a typical use in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0096] Although atrial fibrillation may result in the pooling of blood in the left atrial appendage and the majority of use of the invention is anticipated to be for the left atrial appendage, the invention may also be used on the right atrial appendage and in general for placement across any aperture in the body in which blood clots are substantially prevented from escaping from the cavity and entering into the bloodstream.  
     [0097] As shown in FIG. 4, a thrombus, blood clot, or emboli  30  (collectively referred to as a thrombus) may occur from pooling of blood in the left atrial appendage  13  due to poor circulation of blood therein when the patient experiences atrial fibrillation. When blood pools in the left atrial appendage  13 , thrombus  30  can accumulate therein, build upon itself, and propagate out from the left atrial appendage  13  into the left atrium  11 , thus leaving the heart and entering the blood stream. Once in the bloodstream, such thrombus can block blood flow to the heart, brain, other organs, or peripheral vessels if it becomes lodged in the arteries thereof. Heart attack, a stroke, or ischemia may result.  
     [0098] To prevent thrombus  30  from forming in the left atrial appendage  13 , or to prevent thrombus formed therein from leaving and entering the blood stream which may cause a heart attack, a stroke or ischemia, a membrane  40  is permanently attached over or across the ostium  20  of the atrial appendage  13 . The membrane  40  can be made of bicompatible materials, such as, for example, ePFTE (e.g., Gortex®), polyester (e.g., Dacron®), PTFE (e.g., Teflon®), silicone, urethane, metal fibers, or other biocompatible polymers.  
     [0099] For each of the embodiments described hereinbelow, the membrane  40  may be substantially impermeable with respect to the flow of blood. For an impermeable membrane, neither blood nor thrombus is permitted to flow through the membrane. As described hereinabove, this structure prevents thrombus inside the atrial appendage from entering the bloodstream and causing heart attack, stroke, or ischemia. The impermeable membrane may be fabricated from materials described above, such as polyurethane, polyester (e.g., Dacron®), ePFTE (e.g., Gortex®) in textile, braid, or substrate form. The impermeable membrane could also be comprised of a combination of two or more materials. In some cases, the outer periphery of the membrane may be supported by struts fabricated from metal (e.g., stainless steel or nitinol) or plastic, or by cells or braid. (See, e.g., FIGS. 20, 22,  24 ,  50 ,  56 ). This additional structure may provide additional securement of the outer periphery of the membrane against the atrial wall surrounding the ostium in order to provide a leakproof seal.  
     [0100] According to another embodiment, each of the membrane structures  40  described herein may alternatively be substantially permeable with respect to the flow of blood therethrough. The permeable membrane may also act as a filtering membrane in that it will substantially inhibit thrombus from passing therethrough. The permeable filtering membrane may have pore sizes ranging from about 50 to about 400 microns. It is also contemplated that the pores may also be larger or smaller as indicated by the circumstances, provided such pores substantially inhibit thrombus from passing therethrough. The open area of the filtering membrane is preferably at least 20% of the overall surface area, although a range of about 25-60% may be preferred. The structure of the filtering membrane is preferably a two-dimensional screen, a cellular matrix, a woven or non-woven mesh, or the like. The filtering membrane may also be a permeable metal or a metal mesh of fine fibers. The filtering membrane may be coated or covered with an anticoagulant, such as heparin, or another compound, or treated to provide antithromogenic properties.  
     [0101] The permeability of the filtering membrane, described above, allows blood to flow therethrough while blocking or inhibiting the passage of thrombus, clots, or emboli formed within the atrial appendage from entering the atrium of the heart and, eventually, the patient&#39;s bloodstream.  
     [0102] The characteristic of allowing the flow of blood through the filtering membrane provides several advantages. For example, the left atrial appendage inherently contracts during normal cardiac function to force blood through the heart. These contractions result in blood flow through the ostium of the left atrial appendage. Allowing blood flow through the filtering membrane substantially reduces any pressure gradient that may exist between the appendage and the atrium.  
     [0103] The reduction of the pressure gradient may be helpful to the patient during recovery from the implantation of the filtering membrane structure in the atrial appendage. More particularly, the heart is able to more gradually adapt to the presence of the filtering membrane when blood is permitted to flow through the membrane, and consequently through the ostium of the left atrial appendage.  
     [0104] The filtering function may also reduce the risk of leakage about the periphery of the filtering membrane, or of dislodgement of the filtering membrane that may result from the exertion of pressure against the surface of the filtering membrane. Allowing the blood flow across the filtering membrane may relieve this pressure, sufficiently and in a controlled manner, to reduce such leakage or dislodgement.  
     [0105] Tissue ingrowth may provide additional securement of the filtering membrane to the ostium. More particularly, the growth of tissue may occur along the outer periphery of the filtering membrane or supporting structure adjacent the ostium This tissue growth, in cooperation with the pressure relief provided by the permeable structure, may provide additional means of reducing leakage about the periphery of the filtering membrane. Tissue growth may eventually cover additional surface area of the filtering membrane.  
     [0106] The membrane  40  placed across or over the ostium  20  should be antithrombotic. In order to make the membrane antithrombotic, heparin or other anticoagulants or antiplatelet agents may be used on the membrane  40 .  
     [0107] When permeable filtering membranes  40  are used, an ingrowth of cells may eventually cover the membrane with endothelial cells. The endothelial cells present a smooth cellular wall covering the membrane which prevents thrombosis from occurring at the membrane.  
     [0108]FIGS. 1 and 2 show a cross section of a human heart showing a thrombus  30  in the left atrial appendage  13 . The figures also show the atrial appendage ostium  20  which is to have a membrane  40  placed over it to prevent the thrombus  30  from escaping out of the atrial appendage  13  into the left atrium  11  and thus into the blood stream, which could cause a stroke, a heart attack or ischemia.  
     [0109]FIG. 3 shows a cross section of a human heart showing a thrombus  30  in the right atrial appendage  23 . The right atrial appendage  23  can be treated in the same manner as the left atrial appendage  13 .  
     [0110]FIG. 4 shows a cross section of the left atrium  11 , the ostium  20  and the left atrial appendage  13  having a thrombus  30  therein  
     [0111]FIG. 5 shows a delivery catheter  125  containing a collapsed membrane  40  and a collapsed disk  130  connected to the membrane  40  by a spring  90  on catheter  21 . The disk  130  may be made of a flexible woven metal or a flexible woven metal with a thin permeable polymer sandwiched inside. Disk  130  may also be a polymer weave. The disk  130  is flexible and compresses or folds so it fits into the delivery catheter  125  and expands to its desired shape after release from the delivery catheter  125 . Similarly, membrane  40  compresses or folds to fit into the delivery catheter  125  and expands to its desired shape after release. Membrane  40  is larger than the ostium  20 . FIG. 6 shows the membrane  40 , disk  130  and spring  90  from FIG. 5 in an expanded configuration outside of the delivery catheter  125 .  
     [0112]FIG. 6 shows the spring  90  connecting the membrane  40  and the disk  130  for urging them together. In other embodiments an elastic tether or a tether with teeth and a pawl on the membrane  40  to form a ratchet can also be used to pull the membrane  40  and the disk  130  together. Since membrane  40  is larger than the ostium  20 , the outer periphery of membrane  40  is in contact with the atrial wall surrounding the ostium.  
     [0113]FIG. 7 shows the device of FIG. 5 applied to the left atrial appendage  13  having thrombus  30 . After the device is applied, the spring  90  pulls the disk  130  toward the membrane  40 , collapsing the left atrial appendage  13  and trapping the thrombus  30  therein as shown in FIG. 8. The spring  90  secures the outer periphery of the membrane  40  in direct engagement with the atrial wall surrounding the ostium  20 .  
     [0114]FIG. 9 shows an alternate embodiment of the device in FIGS. 7 and 8 wherein the catheter  21  is equipped with a vacuum  140  for sucking out blood and thrombosis  30  found in the left atrial appendage  13 . The vacuum  140  will help collapse the left atrial appendage  13  such that spring  90  need not be as large as in FIG. 7.  
     [0115] FIGS.  10 - 12  show another embodiment of the invention using an umbrella principle for securing the membrane  40  against the ostium  20 . FIG. 10 shows closed umbrella struts  160  entering the ostium  20  of left atrial appendage  13 . The membrane  40  is some distance back from the umbrella struts  160  at the bottom of the range of teeth  195  on pole  170 . FIG. 11 shows the umbrella struts inside of the left atrial appendage  13  with the struts  160  open. Umbrella opening structure  175  on pole  170  pushes the struts out to the umbrella open position. The umbrella opening structure  175  can be pushed to the open position or have a spring loaded mechanism to push the struts  160  to the open position. The ends of the umbrella struts  160  engage the left atrial appendage wall around the ostium  20  and prevent the umbrella from being withdrawn from the left atrial appendage  13 . The ends of the umbrella struts  160  that engage the atrial appendage wall may be blunted or have bulbs on the tips or have padding so as not to puncture the left atrial appendage  13 . FIG. 12 shows the outer periphery of membrane  40  drawn up against the atrial wall surrounding the ostium  20  by ratcheting the membrane along pole  170 . The pawl mechanism  200  engages teeth  195  on pole  170  and is moved forward to snugly position the membrane  40  across the ostium  20  such that the outer periphery of the membrane  40  is in direct engagement with the atrial wall surrounding the ostium.  
     [0116]FIG. 13 shows the left atrial appendage  13  compressed such that the volume of the atrial appendage is reduced to almost nothing. With the volume reduced the atrial appendage will not have a large volume of blood which can produce a thrombus. In the embodiment shown disk  130  and spring  90  pull the left atrial appendage  13  toward membrane  40 . Although FIG. 13 shows the use of a disk  130  and spring  90  to act on the left appendage, any method to reduce the volume of the atrial appendage as much as possible may be used.  
     [0117] As shown in FIG. 13 the membrane  40  is much larger than the ostium  20 . The oversized membrane  40  may alternatively be used in all embodiments to ensure that the ostium  20  is completely covered. The spring  90  secures the outer periphery of the membrane  40  in direct engagement with the atrial wall surrounding the ostium  20 . The membrane  40  has a structure which blocks or substantially inhibits thrombus, clots or emboli from entering the atrium, and eventually, the bloodstream of the patient.  
     [0118] FIGS.  14 - 18  show another embodiment of the invention wherein the outer periphery of the membrane  40  is secured in direct engagement with the atrial wall surrounding the ostium  20  by an expandable structure, such as balloon structure  402 . As illustrated in FIG. 15, balloon structure  402  may be manufactured from polymeric materials or similar materials known in the art. Tube  404  communicates with the internal cavity of balloon structure  402  for introducing saline or other appropriate fluid into the balloon structure  402 . Membrane  40  is attached to tube  404  in any appropriate manner, such as adhesive, sutures, or other means, and is provided with an aperture  406  which permits access to an end portion of tube  404 , which acts as a balloon introduction port  408  to allow the introduction of fluid into the balloon structure  402 .  
     [0119]FIG. 14 also illustrates a structure for introducing fluid into the balloon structure  402 , such as catheter apparatus  410 . Catheter apparatus  410  includes an outlet port  412  at its distal end portion for ejecting fluid from the catheter apparatus  410 . Outlet port  412  may be connected to the balloon introduction port  408 , which in turn communicates with the internal lumen of tube  404  and the interior of balloon structure  402 .  
     [0120]FIG. 15 illustrates the membrane  40 , the balloon structure  402 , the tube  404 , together with the catheter  410  attached to the tube  404 , in a compacted configuration within a delivery tube  422 . More particularly, balloon structure  402  is in its collapsed state and membrane  40  is flexible and compressed or folded to fit into the delivery tube  422 . Membrane  40  is designed to expand into a disc-like shape after release from tube  422 . FIG. 16 illustrates the certain structures pertinent to the interconnection of catheter  410  with tube  404 . More particularly, outlet port  412  of catheter  410  may be provided with narrow tube  424  which is received within balloon introduction port  408  and maintains a valve  426  in an open position when outlet port  412  is connected to inlet port  408 . When outlet port  412  is removed from balloon introduction port  408 , valve  426  may close to prevent fluid from leaving balloon structure  402 , as shown in FIG. 16.  
     [0121] Delivery tube  422  may be introduced into the venous or arterial system at an appropriate location, and advanced to into the atrium of the heart with appropriate steering and visualization apparatus (not shown).  
     [0122]FIG. 17 illustrates a later stage in the installation procedure wherein the membrane  40 , the balloon structure  402 , the tube  404 , and the catheter  410  have been advanced from the delivery tube  422  (not shown in FIG. 17). The balloon structure  402  is positioned within the left atrial appendage  13  such that the outer periphery of membrane  40  is positioned adjacent the atrial wall surrounding the ostium  20 . Fluid is subsequently introduced into the catheter  410  which passes through tube  404  to expand the balloon structure  402 , as illustrated in FIG. 18. The balloon structure  402  expands within the atrial appendage  13  and secures the membrane  40  in position. The valve mechanism  426  (not shown in FIG. 18) of balloon introduction port  408  prevents the fluid from passing out of the balloon structure  402  when the catheter  410  is detached from the balloon port  408  and subsequently removed from the atrium. As described above, membrane  40  may have an impermeable structure which prevents thrombus for exiting the atrial appendage  13 , but which also prevents blood flow through the membrane  40 . Membrane  40  may alternatively be a permeable structure which allows blood to flow therethrough but which blocks or substantially inhibits thrombi, clots or emboli from exiting the atrial appendage  13 ; and entering the bloodstream of the patient.  
     [0123] FIGS.  19 - 31  illustrate yet another embodiment for attaching the membrane across the ostium  20  of the left atrial appendage  13 . FIG. 19 illustrates the membrane  40 , the attachment apparatus  440  for securing the membrane  40  across the ostium  20  of the atrial appendage  13 , and catheter apparatus  442  for installing the attachment apparatus  440  and membrane  40 . As FIG. 20 illustrates, attachment apparatus  440  and membrane  40  may be initially in a compacted configuration. Attachment apparatus  440  is preferably an expandable tubular apparatus having an initial diameter  444  of about 1-3 mm and an initial length  446  of about 0.5-6 cm. Attachment apparatus is preferably manufactured from a flexible material such as stainless steel, nitinol, nylon, polyester, PET, or polyethylene. Attachment apparatus  440  may be expanded by an expansion structure, such as balloon structure  452  or mechanical expansion structures  472  or  482 . Alternatively, attachment apparatus  440  may be self-expanding, such that it is normally biased in an expanded position, such as that described with respect to FIG. 24, and deployed in a constrained position such as that described with respect to FIG. 20. Apparatus for constraining the self-expanding apparatus is typically a tube.  
     [0124] Membrane  40  is attached to attachment apparatus  440  at the proximal end thereof, in a loosely fitted, somewhat conical configuration and defines a central opening  448 , which allows the catheter  450  of catheter apparatus  442  to pass through membrane  40 , as will be described in greater detail herein. Alternatively, membrane  40  may also cover a greater portion of the length  446  of the attachment apparatus  440 , or membrane  40  may cover the entire attachment apparatus  440  in a substantially sock-like fashion. Membrane  40  may be fabricated from a material that also has elastic characteristics which may expand from a first size to a second size.  
     [0125] Catheter  450  supplies expansion fluid, such as saline or contrast medium, into expandable structure, such as balloon structure  452 , which is positioned within the interior lumen of attachment apparatus  440  in order to radially expand attachment apparatus  440  when it is positioned within the atrial appendage  13 . Balloon structure  452  may include a distal, atraumatic tip portion  454 , e.g., a flexible helical coil or soft plastic tip.  
     [0126]FIGS. 21 and 23 illustrate planar developments of attachment apparatus  440 . The structure of attachment apparatus  440  preferably allows the length  446  of the apparatus in its initial configuration (FIG. 21) to remain substantially constant with respect to the length  456  in its expanded configuration (FIG. 23). In order to achieve this expansion while maintaining substantially constant length, attachment apparatus  440  is provided with a configuration having several serpentine segments  458 ,  460 , and  462 . Adjacent serpentine segments are interconnected by a plurality of longitudinal struts, e.g., rings  457  and  460  are interconnected by struts  464  and rings  460  and  462  are interconnected by struts  466 . A plurality of members  470  at the distal end portion of apparatus  440  may provide an attachment point for the membrane  40 . More particularly, radial members  471  are configured to extend radially outward (FIG. 22) to provide a location for attachment of the outer periphery of membrane  40  and to provide a surface for attachment to the atrial wall. As will be described herein, radial members  471  may be expanded to the radially outward configuration by an expansion member such as a balloon. In one embodiment, the materials or thickness of members  471  may be selected in order to allow members  471  to expand to a greater extent than the rest of the attachment member  440 . Alternatively, members  471  may be fabricated from a self-expanding material, such as, e.g., nitinol, wherein members are normally biased in the radially outward configuration.  
     [0127]FIG. 24 illustrates attachment member  440  in an expanded configuration, wherein length  456  remains substantially constant with respect to the length  446  of the configuration illustrated in FIG. 30. Diameter  472  is substantially larger than diameter  444  (FIG. 20) in order to secure itself against the interior of the atrial appendage  13  and to secure membrane  40  in direct engagement with the atrial wall surrounding the ostium  20 , as will be described herein. Members  471  extend radially outward, and provide structure to the outer periphery of membrane  40 .  
     [0128] FIGS.  25 - 28  illustrate several embodiments of the membrane  40 . As described above, catheter  450  passes through opening  458  in membrane  40  in order to supply expansion fluid to expandable balloon structure  452 . After balloon structure  452  has expanded the attachment apparatus  440  to the expanded configuration illustrated in FIG. 24, it may be necessary to remove balloon structure  452  by passing the balloon structure  452  proximally through membrane  40 , and more particularly, through opening  458 . The embodiments of membrane  40  illustrated in FIGS.  25 - 28  may facilitate the passage of balloon structure  452 , or other interventional devices therethrough.  
     [0129]FIG. 25 illustrates membrane  40   a  having a composite construction comprising filtering section  474   a  and elastic section  476   a . The filtering section  474   a  is fabricated from a filtering material that provides the function of filtering the blood to allow the blood to pass therethrough while blocking or substantially inhibiting the passage of clots, thrombus or emboli therethrough, as described above. The elastic section  476   a  is fabricated from an elastic material, e.g., silicone, urethane or other similar material, that stretches to enlarge opening  458   a  to allow the balloon structure  452  or other intervention devices, such as, e.g., wires, catheters or the like, to pass therethrough and to subsequently return to its initial size. The initial size of aperture  458   a  provides similar characteristic to inhibit clots, thrombus or emboli from passing through  458   a  as filtering material of filtering section  474   a . In this configuration, elastic material  476   a  extends substantially across the entire diameter  472   a  of the membrane  40   a.    
     [0130] Membrane  40   b  (FIG. 26) is constructed with a filtering section  474   b  (i.e., the same material as filtering section  474   a ) and an elastic section  476   b  (i.e., the same elastic material as elastic section  476   a ). In membrane  40   b , the filtering section  474   b  substantially concentrically surrounds the elastic section  476   b . The elastic section  476   b  is provided with an opening  458   b  that expands to allow the balloon structure  452  or other interventional devices to pass therethrough and to return to initial size in order to provide substantially the same characteristic of inhibiting the passage of thrombus, clots and emboli from passing therethrough as the filtering material of the filtering section  474   b.    
     [0131] Membrane  40   c  (FIG. 27) is constructed with a filtering section  474   c  (i.e., the same material as filtering section  474   a ) and an elastic section  476   c  (i.e., the same elastic material as elastic section  476   a ). In membrane  40   c , the filtering section  474   c  substantially concentrically surrounds an elastic section, such as substantially elliptical section  476   c . The elastic section  476   c  is provided with an aperture, such as a slit  458   c  that expands to allow the balloon structure  452  or other interventional devices to pass therethrough and to return to initial size to provide substantially the same characteristic of inhibiting the passage of thrombus, clots and emboli from passing therethrough as the filtering material of the faltering section  474   b.    
     [0132] Membrane  40   d  (FIG. 28) may be fabricated from the same material as filtering section  474   a , above, in several sections, such as sections  475   d  and  477   d , which overlap at region  479   d  to form an opening therethrough for balloon structure  452  or other interventional devices. It is further contemplated that three or more sections of filtering material may be used in an overlapping configuration, in a manner similar to, for example, the “aperture” configuration of an optical device. The balloon structure  452  may be passed through the opening between sections  475   d  and  477   d . After the balloon structure  452  is removed, the overlapping structure substantially closes the opening and provides substantially the same characteristic of inhibiting the passage of thrombus, clots and emboli from passing therethrough as the filtering material of the filtering sections  475   d  and  477   d.    
     [0133] FIGS.  29 - 31  illustrate the procedure for installing attachment apparatus  440  and membrane  40  in the atrial appendage  13 . In an initial step (FIG. 29), balloon structure  452 , along with attachment apparatus  440  are inserted into the atrial appendage  13  in its initial, compact configuration. In FIG. 30, expansion fluid is passed through catheter  450  and exits through port  453  to fill the interior of balloon structure  452 . Balloon structure  452  expands, thereby radially enlarging attachment apparatus  440 , as described with respect to FIGS.  21 - 24 , above. In a preferred embodiment, proximal portion  455  of balloon  452  is constructed to expand to a greater extent in order to deflect members  471  radially outward. Alternatively, members  471  may be constructed to expand to a greater extent than the rest of the attachment member  440  when expanded by balloon  452 . In another embodiment, members  471  may be fabricated from a self-expanding material, such as, e.g., nitinol, wherein members  471  are normally biased in the radially outward configuration. Consequently, the outer periphery of membrane  40  is expanded to be in direct contact with the atrial wall surrounding the ostium  20 . Members  471  provide additional support to provide a good seal with the edge of the membrane  40 .  
     [0134] As illustrated in FIG. 31, attachment apparatus  440  engages the interior of the atrial appendage  13 , thereby securing the membrane  40  in position across the ostium  20 , such that the outer periphery of membrane  40  is in direct engagement with the atrial wall surrounding the ostium  20 . Balloon structure  452  may be removed from the atrial appendage  13  by returning the balloon structure  452  to its initial compact configuration (e.g., by draining the expansion fluid therefrom) and withdrawing the balloon structure proximally through opening  458 . As described above with respect to FIGS.  25 - 28 , the membrane may be fabricated with an elastic portion which expands to permit the withdrawal of the balloon structure therethrough, and which subsequently reduces in size to inhibit the passage of thrombi, clots and emboli therethrough into the atrium. The catheter structure  442  may be subsequently removed from the patient. Alternatively, the balloon structure  452  may remain within the atrial appendage  13  following expansion of attachment apparatus  440  and subsequent return of the balloon structure  452  to its initial compact configuration. For example, catheter  450  may be detachable from balloon structure  452  in a manner similar to the configuration of catheter  410  and tube  404  (FIG. 16). Alternatively, attachment structure  440  may be manufactured from a self-expanding material, such as nitinol, wherein attachment structure is normally biased in a configuration such as that shown in FIG. 24. In order to install the attachment structure  440  within the atrial appendage  13 , the attachment structure  440  may be constrained in a tube. The attachment structure  440  may subsequently be deployed from the tube and permitted to self-expand to a configuration similar to that shown in FIG. 31.  
     [0135] FIGS.  32 - 34  illustrate another embodiment of the invention. Attachment apparatus  460  and balloon apparatus  462  are substantially the same as attachment apparatus  440  and balloon apparatus  452 , described hereinabove, with the differences noted below. Attachment apparatus  460  may be provided with a plurality of engagement members  464 , such as prongs, hooks, or the like, in order to engage and/or pierce the wall of the atrial appendage to provide additional securement of the attachment apparatus  460 . Balloon structure  452  may be used in connection with attachment apparatus  460 . Alternatively, balloon structure  462  may be provided having a distal end portion which is configured to expand to a greater extent than the proximal portion thereof (FIG. 33). This greater expansion of the balloon structure  462  provides additional force in the area of the engagement members  464  to drive them into the wall of the atrial appendage  13  (FIG. 34).  
     [0136] FIGS.  35 - 36  illustrate additional embodiments of expandable structures for radially enlarging the attachment apparatus  440  (or  460 ) within the atrial appendage. Instead of, or in addition to balloon structures (such as balloon structure  452 ), it is also contemplated that mechanical expansion structures may be particularly useful. FIGS.  35 ( a )-( b ) illustrate a mechanical expansion structure  472  which may be used to radially expand attachment apparatus  440 . As shown in FIG. 35( a ), mechanical expansion structure  472  may have a compact configuration wherein a plurality of contact members  474  define a diameter  476  that enables the structure to be inserted within the attachment apparatus  440 . As illustrated in FIG. 35( b ), mechanical expansion structure  472  also has an expanded configuration, wherein contact members  474  are further spaced apart to define a larger diameter  477  which radially enlarges the attachment apparatus to the configuration illustrated in FIGS.  21 - 24  and  30 - 31 . A linkage configuration may include linkage members  478  and sleeve  479 . Sleeve  479  is provided with internal threading (not shown) which engages external threading  480  on a portion of drive screw  481 . Angular rotation of drive screw  481  (as indicated by the arrow) provides longitudinal movement of sleeve  479  which cooperates with linkage members  478  to controllably move the contact members  474  between the compact and expanded configurations.  
     [0137]FIG. 36 illustrates mechanical expansion structure  482 , which is substantially identical to mechanical expansion structure  472 . Sleeve  489  interacts with linkage members  478  to controllably move contact members  474 , as described above with respect to sleeve  479 . Sleeve  489  is longitudinally slidable with respect to elongated member  491 . A locking structure (not shown) may also be provided to fix the position of sleeve  489  (and thus contact members  474 ) with respect to elongated member  491 .  
     [0138] Mechanical expansion structures  472  and  482  may remain in the atrial appendage  13  following the expansion of attachment apparatus  440  (or  460 ). A portion of the drive screw  481  or elongated member  491  may be detachable from the expansion structures  472  or  482 , respectively (not shown). Alternatively, apparatus substantially similar to mechanical expansion structures  472 / 482  may be useful as supporting structures for membrane  40 . According to this embodiment, membrane  40  may be attached to an end portion of structure  472 / 482 , e.g., by attaching membrane  40  to end portions of contact members  474  or by substantially enclosing contact members  474  and linkage members  478 . The structure  472 / 482  may be positioned in the atrial appendage  13  and expanded as described above, such that membrane  40  extends across the ostium  20  to allow blood to pass therethrough while inhibiting the passage of thrombus through the membrane  40 . Drive screw  481  or elongated member  491  may be subsequently detached from the apparatus  472 / 482 .  
     [0139] FIGS.  37 - 39  illustrate another embodiment of the invention. Membrane  40  may be installed in the atrial appendage  13  and held therein by attachment apparatus  500 , which preferably consists of a pair of flexible wire portions  502   a  and  502   b , which are preferably constructed of a material such as nitinol or Elgiloy or stainless steel and having a wire diameter of approximately 0.005 to 0.020 inch. Each wire portion  502   a / 502   b  may include a curved portion  504   a / 504   b , a pair of support members  506   a / 506   b  and a plurality of engagement members  508 . The curved portions  504   a / 504   b  define a substantially closed portion for mounting the membrane  40 . The membrane  40  is attached with sutures, adhesive, or other appropriate means. The engagement members  508  are configured to engage the interior of the atrial appendage  13  to secure the membrane  40  in position across the ostium  20 , as will be described herein. The engagement members  508  may be provided with atraumatic end portions  510 .  
     [0140]FIG. 40 illustrates attachment apparatus  500  and membrane  40  in a compacted configuration for installation in the atrial appendage  13 . Preferably, a delivery catheter apparatus  520  is used to introduce the attachment apparatus  500  and membrane  40  to the atrial appendage. The curved portions  504   a / 504   b  are deflected proximally toward parallelism with the longitudinal axis of the catheter  520 , and the engagement members  508  are deflected distally toward parallelism with the longitudinal axis. An inner member  522  is slidably received within the interior of catheter  520  and may be moved relatively longitudinally with respect to catheter apparatus  520  in order to deploy and install the attachment apparatus  500  and membrane  40 .  
     [0141] FIGS.  41 - 43  illustrated several options for installing the membrane across the ostium  20 . As illustrated in FIG. 50, the curved portions  504   a / 504   b  are positioned within the walls of the ostium  20  itself. The engagement members  508  provide additional support by engaging the interior of the atrial appendage. Alternatively, the curved portions  504   a / 504   b  are positioned outside the ostium within the atrium. Engagement members  508  retain the outer periphery of membrane  40  in direct engagement with the atrial wall surrounding the ostium  20 . According to yet another alternative embodiment, engagement member  508  are provided with sharpened barb end portions  512  which engage and/or pierce the wall of the atrial appendage to secure the membrane in position (FIG. 43).  
     [0142] FIGS.  44 - 45  illustrate another embodiment of the invention. Attachment apparatus  650  provides a first plurality of strut wires  652  that extend distally and radially outward from a support ring  654  toward the distal end portion  656  of the attachment apparatus  650 , and a second plurality of strut wires  658  that extend proximally and radially outward from support ring  654  toward the proximal end portion  660 . The strut wires  652 / 658  may be constructed from an alloy, such as nitinol, having shape memory characteristics. The support ring  654  maintains the strut wires  652 / 658  in the proper configuration and may be made of radiopaque materials, such as, e.g., platinum to provide fluoroscopic imaging of the device position. The strut wires  652  may be provided with barbs  662  or other methods for attachment to the interior of the atrial appendage. The struts  652 / 658  are configured to engage the walls of the ostium on the inner and outside sides thereof, respectively.  
     [0143] The strut wires  658  may serve as a membrane mounting structure. The membrane  40  is attached to strut wires  658  and provides the characteristics described above. In one embodiment, the membrane  40  is permeable wherein blood is allowed to pass through the membrane  40 , but thrombi, clots, and emboli are inhibited from passing therethrough. Alternatively, the membrane  40  may be impermeable to the flow of thrombus as well as blood. The membrane  40  may be connected to the strut wires  602  using adhesive, sutures, encapsulation or other means.  
     [0144] Another embodiment of the invention is illustrated in FIG. 46. Attachment apparatus  670  is constructed of braided or woven mesh material rather than the strut wires  652 / 658  described with respect to FIGS.  44 - 45 . The distal portion  672  is configured to engage the wall of the atrial appendage adjacent the inner portion of the ostium, and the proximal portion  676  is configured to engage the outer portion of the ostium, and the neck portion  674  is disposed therebetween. The braided or woven self-expanded mesh material of attachment apparatus  670  has similar filtering characteristics as membrane  40 , or alternatively, a membrane is attached to the mesh material to provide those characteristics.  
     [0145] FIGS.  47 - 48  illustrate apparatus for delivering and installing the attachment apparatus  650  and membrane  40  and/or attachment apparatus  670 . The catheter apparatus  620  includes an outer sheath  622  and an inner member  624  slidably received within the interior of outer sheath  622 . The outer sheath  622  and inner member  624  may be fabricated from materials, such as polymers, that are sufficiently flexible to negotiate the anatomy, yet sufficiently rigid for relative longitudinal movement to deploy and position the attachment apparatus  600 . Inner member  624  may have a distal end portion  626  and a shoulder portion  628 . Strut wires  652  of apparatus  650  (or distal portions  672  of apparatus  670 ) are deflected distally toward parallelism with the longitudinal axis of the catheter device  620  and retained in the deflected configuration by the outer sheath  622 . Similarly, strut wires  658  (or proximal portions  676 ) are deflected proximally toward parallelism with the longitudinal axis and retained in this configuration by the outer sheath  622 . In order to deploy the attachment apparatus  600 , the outer sheath  622  is moved longitudinally relative to the inner member  626 . The shoulder portion  628  retains the attachment apparatus  650 / 670  in position. Upon retraction of the outer sheath  622 , the shape memory characteristics of the strut wires  652 / 658  (or portions  672 / 676 ) cause the apparatus to return to a shape approximating that of FIG. 44 (or FIG. 46).  
     [0146] FIGS.  49 - 50  illustrate the installation of attachment apparatus  650 / 670  and membrane  40  in greater detail. As illustrated in FIG. 49, the catheter device  622  is advanced partially within the atrial appendage  13 . The outer sheath  622  may be retracted proximally, which permits the strut wires  652  to extend radially outwardly. The physician may use the radiopaque characteristics of the ring  654  in order to properly position the ring  654  within the ostium  20 . Further proximal retraction of the outer sheath  622  allows the distal strut wires  652  and the proximal strut wires  658  to extend radially outward and engage the interior of the atrial appendage  13  (FIG. 50). The barbs  662  may engage and/or pierce the wall of the atrial appendage to provide increased stability of the attachment apparatus  600 . The membrane  40  is consequently positioned across the ostium  20  such that the outer periphery of membrane  40  is secured in direct engagement with the atrial wall surrounding the ostium. In one embodiment, the membrane  40  is impermeable and does not permit blood or thrombus to flow, whereas a filtering membrane may be used to allow blood to pass through the membrane, while substantially inhibiting thrombi, clots, and emboli from exiting the atrial appendage  13 . Struts  658  provide additional securement in order to maintain a leakproof seal between membrane  40  and the atrial wall surrounding the ostium  20 .  
     [0147] FIGS.  51 - 52  illustrate yet another embodiment of the invention. Attachment apparatus  700  provides a plurality of strut wires  702  that extend radially outward from a support ring  704 . A first portion  706  of each strut wire  702  extends towards the proximal end portion  708  of the attachment apparatus  700 , and a second portion  710  of each strut wire  702  extends towards the distal end portion  712 . The distal portion  710  of each strut wire  702  may be provided with a sharpened barb tip  714  or other methods for attachment to the interior of the atrial appendage. The strut wires  702  are constructed from an alloy, similar to material used for strut wires  602 , above. The support ring  704  maintains the strut wires  702  in the proper configuration and is substantially similar to support ring  604 , above. The proximal portions  706  and distal portions  710  of strut wires  702  are configured to engage the walls of the ostium on the outer and inner sides thereof, respectively.  
     [0148] The membrane  40  is attached to proximal portions  706  of strut wires  702  and may provides the filtering characteristic described above, wherein blood is allowed to pass through the membrane  40 , but thrombi, clots, and emboli are inhibited from passing therethrough. Alternatively, membrane  40  may be impermeable to both blood and thrombi. The membrane  40  may be connected to the strut wires  702  using adhesive, sutures, encapsulation or other means.  
     [0149] FIGS.  53 - 54  illustrate apparatus for delivering and installing the attachment apparatus  700  and membrane  40 . The catheter apparatus  620  is described above with respect to FIGS.  47 - 48 . Strut wires  702  are deflected towards parallelism with the longitudinal axis of the catheter device  620  and retained in the deflected configuration by the outer sheath  622 . In order to deploy the attachment apparatus  700 , the outer sheath  622  is moved longitudinally relative to the inner member  626 . The shoulder portion  628  retains the attachment apparatus  700  in position. Upon retraction of the outer sheath  622 , the shape memory characteristics of the strut wires  702  causes the apparatus to resume the shape approximating that of FIG. 51.  
     [0150] FIGS.  55 - 56  illustrate the installation of attachment apparatus  700  and membrane  40  in greater detail. As illustrated in FIG. 55, the catheter device  622  is advanced partially within the atrial appendage  13 . The outer sheath  622  may be retracted proximally, which permits the distal portions  710  of strut wires  702  to extend radially outwardly. Further proximal retraction of the outer sheath  622  allows the distal portions  710  to engage the interior of the atrial appendage  13  and the proximal portions  706  to engage the outer portion of the ostium  20  (FIG. 56). Struts  706  provide additional securement in order to maintain a leakproof seal between membrane  40  and the atrial wall surrounding the ostium  20 . The barbs  714  may engage and/or pierce the wall of the atrial appendage to provide increased stability of the attachment apparatus  700 . The membrane  40  is consequently positioned across the ostium  20 , such that the outer periphery of the membrane is secured in direct engagement with the atrial wall surrounding the ostium  20 . Struts  706  provide additional securement of the membrane to the atrial wall to provide a leakproof seal. A court order should be obtained in order to allow blood to pass through the membrane, while substantially inhibiting thrombi, clots, and emboli from exiting the atrial appendage  13 .  
     [0151] FIGS.  57 - 58  illustrate additional embodiments of the invention. Attachment apparatus  750  includes a plurality of strut wires  752  that extend radially outward and distally from a support member  754  towards the distal end portion  756 . Each strut wire  752  may be provided with a sharpened barb tip  758  or other methods for attachment to the interior of the atrial appendage. The strut wires  702  are constructed from an alloy, similar to the material used for strut wires  602 , above. The support member  754  maintains the strut wires  752  in the desired configuration.  
     [0152] The proximal end portion of support member  754  supports a curved membrane mounting structure  760  that defines a substantially closed curve. The membrane  40  is attached to membrane mounting structure  760  and may provide the filtering characteristic described above, wherein blood is allowed to pass through the membrane  40 , but thrombi, clots, and emboli are inhibited from passing therethrough. The membrane  40  may alternatively be impermeable to blood flow and the passage of thrombi. The membrane  40  may be connected to the membrane mounting structure  760  using adhesive, sutures, encapsulation or other means.  
     [0153] The attachment apparatus  770 , illustrated in FIG. 58 is substantially identical to attachment apparatus  750 , with the differences noted herein. For example, the proximal end portion of support member  754  supports a membrane mounting structure  772  having a spiral configuration. The membrane  40  is attached to spiral mounting structure  772  substantially as described above with respect to membrane mounting structure  760 , above. The spiral configuration may, e.g., assist in reducing the mounting structure to a compacted configuration during installation.  
     [0154] FIGS.  59 - 60  illustrate the installation of attachment apparatus  750  (or  770 ) and membrane  40  in the atrial appendage  13 . Catheter apparatus  780  is provided for delivering and installing the attachment apparatus  750  and membrane  40 . The catheter apparatus  780  is similar to catheter apparatus  620  described above with respect to FIG. 55. Catheter apparatus  780  includes an outer sheath  782  and an inner member  784 . Inner member  784  preferably has an engagement surface  785  on a distal end portion thereof. During installation, strut wires  752  are deflected towards parallelism with the longitudinal axis of the catheter device  780  and retained in the deflected configuration by the outer sheath  782  (not shown in FIG. 59). Similarly, the membrane mounting portion  760  (or  772 ) is folded, rolled or otherwise compacted inside outer sheath  782  as illustrated in FIG. 59.  
     [0155] In order to deploy the attachment apparatus  750 , the catheter device  780  is advanced partially within the atrial appendage  13 . The outer sheath  782  may be retracted proximally, which permits the strut wires  752  to extend radially outwardly due to its shape memory characteristics, as shown. The inner member  784  retains the attachment apparatus  750  in position.  
     [0156] As illustrated in FIG. 60, further proximal retraction of the outer sheath  782  allows the strut wires  752  to extend radially outward and engage the interior of the atrial appendage. The barbs  758  may engage and/or pierce the wall of the atrial appendage to provide increased stability of the attachment apparatus  700 . The membrane mounting structure  760  (or  772 ) is likewise permitted to return to its disc-like configuration, such that membrane  40  is positioned across the ostium  20  such that the outer periphery of the membrane  40  is secured in direct engagement with the atrial wall surrounding the ostium. The membrane  40  may be permeable in order to allow blood to pass through the membrane, while substantially inhibiting thrombi, clots, and emboli from exiting the atrial appendage  13 . Alternatively, the membrane  40  may be impermeable to blood flow and the passage of thrombus.  
     [0157] FIGS.  61 - 67  illustrate additional embodiments of the invention wherein membrane  40  is sized to cover the ostium  20  of the atrial appendage and secured in direct engagement with the atrial wall surrounding the ostium. Membrane  40  is thus provided with a diameter or other dimension that is larger than the diameter or corresponding dimension of the ostium  20  in order to entirely cover the ostium. More particularly, membrane  40  defines an outer periphery which is secured in direct engagement with the ostium or the atrial wall surrounding the ostium.  
     [0158] As illustrated in FIGS.  61 - 62 , membrane  40  is provided with a plurality of engagement members  400 , which may be attached to and positioned about the outer periphery of membrane  40 , and which may have shank portions  402  and barbed free ends  404  which in this case may extend radially outward from the engagement members  400 .  
     [0159] As shown in FIG. 63, membrane  40  is installed to cover ostium  20 . Engagement members  400  pierce the wall of the ostium  20  or the atrial wall surrounding the ostium to attach the membrane  40  directly to the ostium  20  or the atrial wall surrounding the ostium. Barbed free ends  404  prevent the engagement members  400  from being withdrawn from the wall, and assists in securing the membrane  40  in position as shown in the FIG. Membrane  40  has a structure which blocks thrombus from leaving the atrial appendage and entering the bloodstream. A filtering permeable membrane may alternatively be used, which allows blood to flow through while substantially inhibiting thrombus.  
     [0160]FIG. 64 illustrates another embodiment wherein the membrane  40  covers the ostium  20  of the atrial appendage  13 . A biocompatible tissue adhesive  420 , such as fibrin glue or cyanoacrylate or a similar material, may be applied about the outer periphery of the membrane and used to attach the membrane  40  directly to the ostium  20  or the wall of the atrium surrounding the ostium  20 . Membrane  40  blocks thrombus from leaving the atrial appendage and entering the bloodstream. A filtering permeable membrane may alternatively be used, which allows blood to flow through while substantially inhibiting thrombus.  
     [0161] FIGS.  65 - 66  illustrate still another embodiment of the invention wherein membrane  40  is provided with a plurality of engagement members  430 . Each of engagement members  430  is mounted about the periphery of membrane  40 , and has an elongated shank portion  432  that extends distally longitudinally and a barbed free end  434  that may extend radially outward from the elongated shank portion  432 . Shank portion  432  is substantially longer than shank portions  402  described above with respect to FIGS.  61 - 63 . Engagement members  430  define a spacing  436 , or the distance between opposite engagement members  430 , exclusive of the radial projection of the barb-like free ends  434 , that is similar in size to the interior dimensions of the ostium  20 . This spacing  436  between engagement members  430  located on opposite sides of the membrane  40  provides the feature of centering the engagement members within the interior of the ostium  20  and the atrial appendage  13 .  
     [0162] As shown in FIG. 67, membrane  40  is installed to cover ostium  20 . Elongated shank portions  432  extend a distance into the ostium  20  or the atrial appendage  13  and assist in centering the membrane  40  within the ostium  20 . Barbed free ends  434  engage the interior wall of the atrial appendage  13  to prevent the engagement members  430  from being withdrawn from the wall, and secure the membrane  40  in direct engagement with the ostium  40  or the atrial wall surrounding the ostium  40  as shown in the FIG. Membrane  40  has a structure which blocks thrombus from leaving the atrial appendage and entering the bloodstream. A filtering permeable membrane may alternatively be used, which allows blood to flow through while substantially inhibiting thrombus.  
     [0163] The devices described above may be percutaneously delivered to the left and right atrial appendages  13 ,  23  respectively. The devices may have materials in them which enhance visualization or imaging by ultrasound, x-ray or other means making it easier for the device to be implanted and accurately centered with respect to the ostium  20  of the atrial appendage  13 . This may consist of small beads placed strategically on the membrane, the connecting elements, or on the anchors. Referring to FIG. 1 catheter  21  is seen entering the heart by way of the aorta  12  to the left ventricle  16  passing through the mitral valve  17  and then entering the left atrial appendage  13  to apply the membrane  40  in one of the embodiments as disclosed above. In FIG. 2 the catheter  21  enters the heart from the femoral vein, passes through the inferior vena cava  18  to the right atrium and then passes through the fossa ovalis  19  or through the septum  29  into the left atrium  11  and then approaches the left atrial appendage  13  to apply the membrane  40  thereto. FIG. 3 shows the catheter  21  being applied to the right atrial appendage  23 . Catheter  21  may enter the heart through the jugular vein  28  or the femoral vein to the inferior vena cava  18 .  
     [0164] It is understood that the invention may be practiced with numerous means of attaching the membrane  40  across the ostium  20  of the atrial appendages  13  and  23 . All of the above embodiments shown and discussed for the left atrial appendage  13  are also useable on the right atrial appendage  23 . Any combination of the attachment means with adhesives, prongs, cylindrical structures, anchors, disks, tethers or springs may be used. The membrane may penetrate the atrial appendage and provide a means to securely lock the membrane device into place. If permeable characteristics are preferred by the physician, other means of providing a membrane for allowing blood flow therethrough and substantially inhibiting blood clots from exiting out of the atrial appendages not listed herein may also be used.  
     [0165] Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.