Embolus trap
This application is a continuation-in-part of my co-pending application Ser. No. 601,220, filed Apr. 17, 1984, now U.S. Pat. No. 4,643,184, captioned EMBOLUS TRAP which was a continuation-in-part of my application Ser. No. 428,254, filed Sept. 29, 1982 captioned BLOOD CLOT ENGAGING DEVICE FOR FLUID PASSAGEWAYS, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a device for implanting in a fluid passageway of the human body, preferably in the inferior vena cava, and to a method of implanting it. My embolus trap traps migrating blood clots traveling upstream in human veins and prevents them from reaching the lungs. My invention is more particularly concerned with an embolus trap which may be implanted either through the jugular vein, subclavian vein or through the femoral vein, and with specific procedures for such implanting. 
     BACKGROUND OF THE INVENTION 
     The problem addressed by my invention arises especially with persons who have had operations. The extended time in which such a person must lie supine in bed not infrequently leads to the development of blood clots which are carried by the veins to the heart, and by reason of the structure of the human body through the inferior vena cava. As these clots enter the heart at least some are pumped outwardly through the artery which leads to the lungs. It is here that by reason of the numerous small passageways which characterize the lungs that the clots block certain of the blood passageways. This may lead to sudden death because here the clots act so that the blood flow to the lungs is interrupted or obstructed and the rejuvenation required by the oxygenation process cannot take place. 
     In the past, this problem has been met by a major surgical operation which requires a tying of the inferior vena cava and the collateral circulation which results is relied upon to provide passageways for the transmittal of satisfactory blood flow to the heart. Because this surgical operation of tying the vena cava is usually performed on a person who has already been weakened by other surgery, and by reason of the fact that it requires a rather extensive incision through the trunk area to reach the vena cava to tie it, it is considered a major and generally dangerous operation. 
     Anticoagulation agents are effective in many cases; nevertheless formation of blood clots in the veins of the lower extremities and migration thereof to lungs continues to be a major health hazard, especially in hospitalization, resulting in morbidity and mortality. 
     Mechanical devices have been developed for insertion into the vena cava by a simple catheter technique under local anesthetic, thus avoiding a major operation under general anesthesia. One such device is disclosed in Mobin-Uddin U.S. Pat. No. 3,540,431 of Nov. 17, 1970. This device is of umbrella-type configuration including skeletal framework and a hood of filtering media for lodgement in spanning relation of a vein or passageway of the human body to filter fluid flowing in a closed passageway. The undesirable features of this device are: (1) dislodgement and migration in a small percentage of patients; and (2) tendency to clogging up resulting in the development of collateral circulation. Another such device is disclosed in Kimmell U.S. Pat. No. 3,952,747 of Apr. 27, 1976. It comprises a plurality of convergent legs in generally conical array and joined at their convergent ends to an apical hub, each leg having a reversely bent hook at its end which is distal with respect to the hub. Each leg also includes a plurality of bends intermediate its length, which bends decrease the solids by-pass capability of the filter without concurrent fluid occlusion. 
     It has been found that such devices migrate through the blood vessel or passageway resulting in a potentially dangerous complication of internal bleeding and perforation of adjacent important organs. Also this device at times when ejected from the catheter into the vein positions itself sideways or tilted inside the passageway, with resulting increased tendency to an undesirable penetration through the vein wall. 
     THE INVENTOR&#39;S SOLUTION TO THE PROBLEM 
     The embolus trap of my invention is an expansible article which is inserted in its collapsed condition in a passageway and which then opens and anchors itself. It comprises a central hollow column carrying preferably two or more tiers spaced therealong of radially extending elongated filaments, pairs of which are connected at their outer ends to form loops. Each tier includes two or more such loops and the loops of one tier are positioned circumferentially between the loops of the next adjoining tier. At the outside ends the filaments are formed into outwardly extending hooks backed by offsets, the latter limiting the penetration of the hooks into the wall of a passageway in which my device is implanted. The filaments are preferably made of metal wire or other filament with sufficient spring to permit them to be folded back against the central column while my device is inserted into a passageway and then when released to assume a radially extended position within the passageway forcing their hooked ends against the passage wall. I prefer to curve or bow the filaments concave outwardly from the central hollow column in a configuration which I designate as semi-lunarly curved. 
     My device above described is inserted into a vein by a catheter of plastic tubing having a tubular capsule at its distal end containing my device in its collapsed condition. In the capsule the filaments are forced against the central column and are relatively straight. When my embolus trap is ejected its filaments spring outwardly in the vein tending to assume their semi-lunar curvature. A wire guide extends through the hollow central column of my device and out beyond the capsule. The wire guide has a flexible J-tip at its outer end which facilitates maneuvering and prevents anchoring in the wall of the vein. A hollow push rod which fits over the wire allows the catheter to eject my embolus trap from the capsule so that it travels along the wire guide to its destination. For maneuvering the capsule in place a different type of hollow rod is provided which will not eject the embolus trap from the capsule. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of an embodiment of my embolus trap in an intermediate stage of manufacture; 
     FIG. 2 is an isometric view of the completed article of FIG. 1; 
     FIG. 3 is an enlarged detail of the hooks and offsets of a loop of FIG. 2; 
     FIG. 4 is an isometric view of the article of FIG. 2 in an open position in a vein or like passageway; 
     FIG. 5 is a section taken on the plane V--V of FIG. 4; 
     FIG. 6 is an enlarged detail showing hook engagement with a wall of a vein or like passageway; 
     FIG. 7 is an isometric view of an embodiment of my embolus trap shown in FIG. 2 presently preferred by me; 
     FIG. 8 is an assembly of my embolus trap in its catheter; 
     FIGS. 9, 10 and 11 illustrate certain accessories used with my catheter; 
     FIGS. 12 through 16 illustrate certain stages in my process; 
     FIGS. 17, 18 and 19 illustrate the stages of loading my embolus trap into the capsule of my catheter for jugular/subclavian implant; and 
     FIGS. 20 through 23 illustrate the stages of loading my embolus trap into the capsule of my catheter for femoral implant. 
     FIG. 24 is an isometric view similar to FIG. 2 of another embodiment of my invention but showing only one pair of loops, upper or lower. 
     FIG. 25 is a side view of the embolus trap of FIG. 24 in position in the capsule of my catheter. 
     FIG. 26 is a side view similar to FIG. 4 of the embolus trap of FIG. 24 in an open position in a vein or like passageway. 
     FIG. 27 is a view of the embolus trap of FIGS. 25 or 26 at 90 degrees from its position in those figures. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     My embolus trap comprises a central cylindrical column 11 to which is attached a plurality of upper elongated loops 12 of filaments 13 and 14, such as metal wire, and a plurality of like lower loops 15. Loops 12 and 15 are assembled in two tiers spaced from one another on column 11, as are shown in FIGS. 1, 2, 4, 5 and 7. The loops 12 in the upper tier are circumferentially spaced from each other in symmetrical fashion, as are the loops 15 in the lower tier. The loops of adjacent tiers are displaced from each other circumferentially, preferably centrally, so that a loop 12 of the upper tier is centrally located between two loops 15 of the lower tier, and vice versa. The loops as shown in FIGS. 4, 5 and 6 are in their extended position within a passageway 10, each inclined outwardly from column 11 and making contact at its outer end with the wall 24 of passageway 10. Each of loops 12 and 15 is formed of two wires 13 and 14. The inner ends of adjoining filaments, such as 13 and 14, are anchored in central column 11 and the outer ends of those filaments are joined or abutted to form a closed elongated loop as is shown in FIG. 3. The outer ends of filaments 13 and 14 are bent toward each other to form short circumferentially extending portions 18 and 19 respectively, and then 180° in the same plane to form oppositely extending circumferential portions 20 and 21 respectively, as is shown in FIG. 3. The extreme ends of portions 20 and 21 are bent radially outwardly into hooks 22 as is also shown in FIG. 3. The wires of each loop may be joined at the crowns of the open loops formed by bent portions 18 and 20 of wire 13 and 19 and 21 of wire 14, by threading the wires through a short piece of small diameter metal tubing 23 and crimping the tubing against the wires to fix its position. Those circumferentially bent portions 20 and 21 form a stop or barrier which prevents hook 22 from penetrating the wall 24 of the passageway 10 sufficient to puncture it. 
     While the various filaments 13 and 14 may be attached to central column 11 in any convenient manner, I prefer the structure shown in FIG. 7. The filaments in each tier are positioned in pairs at the desired spacing around column 11, enclosed in a metal sleeve 50, and are welded thereto at an end of the sleeve. The sleeve 50 with filaments attached is then crimped on column 11. Column 11 is hollow, and preferably rigid, having a central cavity 51 running therethrough. 
     Although I have described and illustrated four-loop tiers, a two or more tier embodiment may have only two loops per tier, providing that they are rotated with respect to each other sufficiently to effect proper centering. Tiers of three loops or more may be used if desired. Several loops in a single tier may be used. The loops of a tier are preferably shaped so that the areas between the loops are slightly greater than the areas within the loops, and successive tiers are disposed so that a loop of one tier is axially spaced from a space between loops of an adjoining tier. 
     While I have described a central column with protruding wires or filaments formed into loops, the disposition of wire struts attached to the central column can be varied to achieve any desired shape or configuration. The wire struts may be arranged in a plurality of angularly disposed pairs, longitudinally spaced and rotatively displaced around the axis of the central column. 
     When my device is implanted in a vein, for example, as above described, the loops form a central network or web extending over the entire cross section of the vein. A similar network or web is likewise formed by each additional spaced tier of my device. The several tiers are kept in alignment by the central column, thus insuring that each above mentioned web or network is normal to the vein axis. A blood clot approaching my device and being engaged in a loop or loops tends to slide along the wires toward the center impelled by the motion of the bloodstream and to become wedged between the loop and the column. It is thus held in a place where the flow of the bloodstream around it tends to lyse or dissolve the clot. 
     The hooks, as have been mentioned, penetrate the vein wall a controlled amount, so anchoring the device. They are caused to do so by the outward springing of the loops when my device is released from its capsule in a vein. The angle of the hook is canted or adjusted to maximize its holding effect and the dimensions of the hook are adjusted to prevent perforation of the vein wall. The barrier behind each hook formed by the offset bends in the wire previously described effectively limits hook penetration of the vein wall to a safe amount and eliminates any tendency of the hooks to work themselves through the vein wall. 
     It will be evident from the above description that my clot engaging device adjusts itself to veins or other passageways of a considerable range of sizes and is self-centering. Because its hooks are canted so as to be urged toward the vein wall by the flow of blood in a vein it will not dislodge and migrate either upstream or downstream. 
     The apparatus for inserting my embolus trap of FIG. 7 in a vein is shown in FIG. 8. A catheter assembly suitable for my purpose is likewise shown in that figure. A tubular capsule 26 of smaller diameter than a jugular vein has an open end 27 and an opposite end 28 of reduced diameter to which is connected a plastic flexible tube 29. 
     The opposite end of tube 29 is connected to one end of a fitting 33 with a side port 34 for injection purposes and a locking device 35 which locks tube 29 to fitting 33. A hollow push rod stylet 42 passes through the fitting 33 and tube 29 into catheter capsule 26 as shown in FIG. 8. A stylet seal lock 30 with locking hub 31 is affixed to the outside end of stylet 42. A guide wire 36 is threaded through the entire length of hollow push rod stylet 42 and capsule 26. By tightening the locking hub 31 the push rod stylet is locked against guide wire 36. The distal end of guide wire 36 has a flexible J-tip 37. The straight end of guide wire 36 is inserted through the hole 51 in column 11 of my embolus trap and through push rod 42. In order to make clear the functions of my apparatus it will be necessary to describe its method of use. The various steps of placement of an introducer sheath for my embolus trap are shown in FIGS. 12-16 inclusive. FIG. 12 shows puncture of a vein by a temporary or precussor hollow needle 38. In FIG. 13 a wire guide 32, is passed through hollow needle 38 into the vein. In FIG. 14 hollow needle 38 is removed over wire guide 32 leaving the latter in place. In FIG. 15 an introducer sheath 39 and introducer 40 are slipped over wire guide 32 and into the vein. In FIG. 16 the wire guide 32 and introducer 40 are removed leaving introducer sheath 39 in the vein. 
     Wire guide 32 above described is used only to lead the sheath 39 into place. It is not intended to reach the site where the embolus trap is to be stationed. It has a flexible J-tip at its free end to prevent anchoring. After it is removed, my embolus trap is collapsed and loaded into capsule 26 and a second wire guide 36 similar to the first but appreciably longer is threaded through the central hole 51 in column 11 of my trap. The long wire guide 36 is then introduced into the vein through sheath 39 until its J-tipped end 37 reaches the desired location in the vein. The capsule 26 is then advanced over wire guide 36 into the vein to the desired location and wire guide 36 is withdrawn. This is the well-known Seldinger Technique. 
     The process of loading my embolus trap into the capsule of the catheter is somewhat different for jugular subclavian approach than it is for femoral approach, as the embolus trap is loaded in reverse direction. FIGS. 17, 18 and 19 illustrate the procedure for jugular implants. Hollow push rod 42 is introduced into capsule 26 and wire guide 36 is threaded through it and out the open end of capsule 26. That wire guide is also passed through a loading sleeve or cone 46 which fits over the open end of capsule 26 and through hollow column 11 of my embolus trap from top to bottom, as that trap appears in FIG. 7. Then with the help of pin 44 shown in FIG. 11, the embolus trap is pushed through loading cone 46 which collapses its filaments against its center column and into capsule 26, while hollow push rod 42 is withdrawn into capsule end 28 as is shown in FIG. 18. The embolus trap in place in capsule 26 is shown in FIG. 19. 
     The process of loading my embolus trap into capsule 26 for femoral implanting is shown in FIGS. 20 through 23. No hollow push rod is required. Loading cone 47 is fitted onto the open end of capsule 26. My embolus trap is introduced over wire guide 36 into the cone in FIG. 21, bottom end first, as it is positioned in FIG. 7. The tapering cone collapses the wire filaments and with the help of pin 44 the trap is pushed into capsule 26, as is shown in FIG. 22. Then the loading cone 47 is removed. My embolus trap in place in capsule 26 is shown in FIG. 23. 
     FIGS. 24-27 inclusive illustrate another preferred embodiment of my embolus trap. I have found that the individual filaments 13 and 14 described hereinabove may in service break off from column 11 immediately below sleeve 50 or 51. This failure appears to result from the flexing of the filaments in the immediate area adjoining those sleeves where it is confined because of the rather severe bend of the filaments at that region. In my embodiment of the figures above-mentioned, the filaments 53 and 54 forming a loop 55 in their unstressed condition are curved concave outwardly from the central column 11 as is shown in FIG. 24. At the sleeve 50 their ends are aligned with column 11. The two filaments of each pair form a portion of a lune and I call their curvatures semi-lunar. When my embolus trap is confined in a capsule 26 the filaments are forced against column 11 and their radius of curvature is greatly increased as is shown in FIG. 25 but the stress extends over a considerable portion of their length. When my embolus trap is ejected into a vein the filaments spring outwardly so that their hooks 22 engage the wall of the vein 24 as is shown in FIG. 26 and the radius of the curvature of filaments 53 and 54 is appreciably decreased. In both conditions above-described however the stress on the filaments is distributed over a much greater portion of their length than it is in the embodiment illustrated in FIG. 7. In one preferred embodiment of my invention, I employ two tiers of three loops 55 each, spaced equidistantly 120 degrees apart around column 11. 
     While I have shown and described a present preferred embodiment of my invention and I have illustrated a present preferred method of practicing the same, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.