RU2228729C1 - Controlled intravenous filter - Google Patents

Abstract

FIELD: medical engineering. SUBSTANCE: device has two single-direction filtering members composed of arc-shaped elastic threads one set of ends of which are free and part on circular ways from each other for making contact with internal blood vessel surface. The other set of ends are collected together in fixing bushings connected to each other axial rod. Each fixing member has two thread sets, each set having even number of threads. The first set has centering threads arranged between fixing threads belonging to the other set, which free ends end in fixing members. Axial rod is flexible. Centering thread set is engageable with blood vessel internal surface to the moment the fixing threads open and contact is made between ends of fixing threads and blood vessel surface. EFFECT: reliably retained centered position of fixing members; enhanced effectiveness in catching thrombi. 8 cl, 2 dwg

Description

Area of use

The invention relates to medicine and can be used to prevent pulmonary embolism by implantation in the inferior vena cava.

State of the art

Pulmonary embolism, in which emboli from any part of the vascular system enter the lungs, causes thousands of deaths worldwide every year. Blood clots from the lower regions of the circulatory system enter through the inferior vena cava and from here to the lungs.

Many patients with a diagnosed pulmonary embolism are prescribed anticoagulants to prevent further blood clots, but there are cases in which mechanical closure of the inferior vena cava is the only way to prevent the disease. To prevent the passage of blood clots through the inferior vena cava, it was proposed to place special devices there - filters that filter blood clots. An early description of such filters can be found in M. Aivgeu, et al, comparative in vitro evaluation of the nitinol inferior vena cava filter, radiology 145: 351-355, November, 1982. More recent devices are described in patent literature, for example, US patents 4781177, 5669933, 5720764, 5133733, 5108418, 5152777 and 5242462.

From the international application WO 01/93779, a cava filter is known having locking elements in two planes and providing self-centering in the lumen of the vessel. This filter is able to capture blood clots, help reduce their size and prevent further migration up the bloodstream to the lungs. This filter is a two-plane conical design with two sets of legs (threads) that differ in length. At one end, the legs are assembled together and fastened to form a loop to guide the corrective thread through it, which is used to remove the filter if such an indication occurs. The other ends of the legs of both sets are free and protrude at an angle to the axis of the vessel mainly in the radial direction. When the filter is deployed, the ends of one set of legs reach the vessel walls first and center the filter, located in one plane, the ends of the other set touch the walls in another plane, determined by their length, and securely fix the filter. The free ends of the filter legs are provided with locking hooks. Thus, the filter reliably occupies a central position in the bloodstream and provides filtration of the largest emboli. The blood in it passes freely between the legs, due to which there is a subsequent splitting of large clots by the flow of blood, reducing their size and eliminating the danger of subsequent blockage of blood vessels. However, this filter is difficult to remove from the vein without causing injury to the vessel. In addition, due to the close location of the fixation planes, it remains possible to move the filter tip to one of the vessel walls.

The disadvantages of this design include:

- the impossibility of implantation by access from the bottom (bottom to top) due to the lack of retention elements (the filter may jump upon opening);

- the possibility of distortions during implantation due to the small support base, because the distance between the support planes and the places where the ends of the filter threads touch the vessel walls is small and insufficient for stable self-centering, and the manipulation of the hands to install the filter does not guarantee its strict axial orientation.

Design Advantages:

- small size (length in the bloodstream),

- the ability to remove (remove) the filter.

Known removable filter for trapping blood clots according to international application WO 96/12448, the filter has a longitudinal axis and the first and second sets of legs, legs of each set at one end are connected to each other. Each leg has at least two bends with the formation in the center of the cross section of the filter of the region with a more frequent intersection of the bends of the legs and, thus, a higher capture efficiency of passing blood clots. The ends of the legs belonging to different sets are directed in opposite directions, which provides a more stable centering of the filter along the flow axis. However, both the deployment and the removal of this device require a special device of complex design, the use of which does not remove the problem of surgical removal and serious injury to the patient.

Of the advanced domestic structures for this purpose, mention should be made of the hourglass-type kava-filter according to RF patent 2040278. This filter consists of two cones connected by a common rod and formed by elastic threads with free ends bent outward on one of the cones, while free the ends of the other cone are divided into two parts, oppositely curved along the axis of the filter, and the vertices of the cones are facing one another. This filter, however, is not removable and remains in the inferior vena cava for the remainder of the patient's life, even if the pathological condition that served as the basis for his implantation has already passed. A permanent foreign body in the inferior vena cava carries the risk of complications already characteristic of it: thrombosis of the inferior vena cava and fragmentation of the device itself with irreversible consequences.

The disadvantages of this filter are:

- the design can only be used for permanent implantation, and there are no methods of removal;

- one of the filter cones is installed not against, but in the bloodstream, i.e. washed by the flow of blood in the direction from the top to the base; this arrangement does not provide for the capture of blood clots in the center of the bloodstream with subsequent destruction of the strongest blood flow, the blood clot will be carried to the periphery in the region of low blood flow, which in the long run will lead to blockage of blood flow;

a sufficiently large length of the product due to the sequential arrangement of multidirectional filter cones.

Advantages:

- simple implantation (does not require management when setting),

- the ability to deliver with any access (both from top to bottom and from bottom to top).

Closest to the claimed device is a filter according to the patent of the Russian Federation 2178683. This filter actually consists of two identical filter elements connected by an axial element and made in the form of arcuate curved spacer rods fixed in a clip, diverging with free ends around a circle. The spacer rods of both filter elements are oriented in the same direction, the axial rod consists of two halves, the connection of which ensures their mutual longitudinal displacement with a change in the length of the rod. At the end of the clip of one of the filter elements, a loop is fixed for holding or fixing the corrective thread used to remove the filter. This filter is almost universal in terms of matching the size of the vessel where it is introduced. It can be used for temporary and permanent implantation. It reliably catches emboli and maintains a central position quite well, which reduces the risk of parietal thrombosis and the penetration of blood clots into the pulmonary circulation. A great advantage is the softness of the structure, due to the execution of the axial rod, which allows for external mechanical influences on the vessel to avoid distal displacement of the filter and excessive immersion of the spacer rods in the vein wall. However, while maintaining the overall orientation of the filter in the center of the vessel, each filter element can easily move, the top of the cone deviates towards the vessel wall and the filtering efficiency of large emboli decreases. Due to the absence of fixing elements at the ends of the spacer rods, the latter can enter the vein wall at different uncontrolled depths, and in some cases, appear on the wall surface or even lose contact with it.

Thus, it becomes apparent that none of the known structures satisfies all the needs of specialists who solve the problem of filtering blood clots coming off and migrating through the vessels.

In the general case, venous filters are introduced into the vascular system through a puncture or incision in a vessel such as the internal jugular vein, and the filter, elastically fixed in the delivery catheter, moves from the jugular vein through the right atrium into the inferior vena cava, after which it is mechanically removed from the catheter and expanded for contact with the vessel. Various hooks are provided to hold the filter in place after removal of the catheter. When removing a filter with hooks from a vessel, surgery is usually required.

Generally, it is more preferred to temporarily administer a venous filter. Once the cause of blood clots has been eliminated, it is advisable to remove the filter from the vessel. Venous filters usually contain a sleeve or a central part, from which there are many threads, legs or rods that trap blood clots and between which blood flows.

The central part of the filter element, which is located mainly in the center of the vessel, and therefore along the flow axis, is often more effective for holding emboli. This is due to an increase in the number of legs and, therefore, a decrease in the area of the openings for the passage of blood.

The holes of the filter between the legs increase in the direction from the center to the walls of the vessel. For positive results, it is desirable that the center of the filter remains near the center of the vessel, but often this is not easy to achieve, and the center of the filter may shift to one or the other side, thereby filtering efficiency is reduced.

Although, as mentioned above, a wide variety of filters have been proposed for use in the vena cava and other vessels, there remains a need for a filter that can be temporarily inserted into the vena cava and then easily removed without unnecessarily injuring the patient, guaranteed with high efficiency trapping blood clots that do not interfere with reliable and accurate imaging with the introduction of a contrast medium. It is especially desirable to create a filter that can easily and accurately deploy in the vessel, center itself inside the channel and hold this position for a long period throughout the entire service life until removal, can be easily removed and thus serve as a reliable means to preserve the health and life of the patient.

SUMMARY OF THE INVENTION

We offer a new filter that will be free from the above disadvantages.

We have developed a design that provides simple insertion, deployment in a vessel and easy removal while eliminating the cause of blood clots, which has two filter elements, both of which are located in the bloodstream, i.e. washed by the flow of blood in the direction from the base to the top, with the provision of trapping of blood clots in the center of the bloodstream and with the subsequent destruction of the most severe blood flow. Our filter has a small length in the presence of two filter elements, can be supplied by any access - from top to bottom, and from bottom to top. Our filter has a large support base and cannot be offset from the center of the vessel.

The filter contains two filter elements, each of which consists of two unidirectional cones, formed by an even number of flexible threads (wires), and the geometry of the free threads in the two cones is different and such that it ensures the initial opening of the centering threads, and then the fixing ones, which loose threads end with a fixing hook (sharpening element). Two sets of threads (centering and fixing) are arranged so that the threads of one are located between the threads of the other (space shift). The threads of both sets are assembled by a locking sleeve.

The technical result achieved when using this filter in comparison with the closest analogue is to reliably maintain the central position of the filter elements and the filter as a whole and to ensure high efficiency of trapping blood clots in the center of the bloodstream with their subsequent partition.

An additional technical result consists in reliable fixation of the filter to the vessel wall.

Another additional technical result is to provide easy removal of the filter from the vessel.

Another additional technical result is to minimize injury to the patient.

The technical result is achieved due to the fact that in an intravenous filter containing two unidirectional filter elements consisting of arched curved elastic threads, some ends of which are free diverge but to circles for contact with the inner surface of the vessel, and the others are assembled together by fixing bushes interconnected rod, each filter element contains two sets of threads, each set includes an even number of threads, the threads of the first set - centering are designed to center I filter in the blood vessel and are located between the threads of the second set - fixing, designed to fix the filter in the blood vessel, the free ends of the fixing threads end with locking elements, while the rod is flexible, and many centering threads have the ability to contact the free ends of the threads with the inner surface of the blood vessel until the fixing threads open and contact between the free ends of the fixing threads and the vessel occurs.

An additional technical result is achieved due to the fact that the locking elements at the ends of the fixing threads are made in the form of hooks for fixing in the vessel wall or in the form of sharpening elements, which are the pointed ends of the threads.

An additional technical result is achieved due to the fact that the free ends of the centering threads are made rounded or flat.

The technical result is enhanced due to the fact that the centering threads of the two filter elements are configured to form two centering planes in contact with the inner surface of the blood vessel.

The technical result is enhanced due to the fact that the fixing threads of the two filter elements are made with the possibility of the formation of two planes of fixation upon contact and the introduction of the fixing elements into the inner surface of the blood vessel.

The technical result is enhanced by the fact that the radius of curvature of the fixing threads is greater than the radius of curvature of the centering threads.

An additional technical result is achieved due to the fact that the filter is equipped with a locking hook mounted on the free end of the locking sleeve.

The technical result is enhanced due to the fact that the threads and locking sleeves are made of stainless steel.

Brief Description of the Drawings

The invention will be more apparent from the drawings, where figure 1 shows the design of the filter with deployed filter elements; figure 2 shows the placement of the filter in the inferior vena cava with external influence on the vessel, illustrating the ability of the claimed design to self-centering.

SUMMARY OF THE INVENTION

The filter 1 is intended to be placed in a vessel 2, in particular in a vena cava. The filter 1 consists of two unidirectional filter elements 3 having a substantially conical shape. Each filter element contains many threads of two types - centering 4 and fixing 5 threads. The threads have different geometry: the length and radius of curvature, as well as the execution of the free ends (depending on the functions assigned to them). The threads of different sets follow, alternating through one. Moreover, the number of threads of both sets is even. The fixing threads 5 have hooks 7 at the free ends 6 for attaching the filter 1 to the wall of the vessel 2, which serve the purpose of reliable installation and elimination of migration in the bloodstream. Another variant of the ends of the fixing threads 5, however, less preferred is their execution in the form of pointed ends (not shown). The centering threads 4 do not have hooks, and their geometry is such that their contact with the walls of the vessel 2 occurs until the fixing threads 5 are opened. Technically, this is achieved by the corresponding geometry of different types of threads. The radius of curvature of the fixing threads 5 is smaller, and the centering threads 4 are larger.

This opening sequence provides, firstly, the centering of the filter 1 in the bloodstream and only then the fixing of the filter elements 3, and both cones of the filter elements 3 open in this sequence, i.e. the entire filter 1 opens sequentially along the axis 8 of the blood flow. In this case, four planes of contact and fixation of the threads 4, 5 to the wall of the vessel 2 are formed. All threads of both filter elements are assembled together on the opposite 9 from the free ends by means of fixing sleeves 10. The sleeves 10 are interconnected by a flexible axial rod 11, which can be easily bent, helping to maintain the central position of the filter element. The filter has two options for ensuring its establishment and removal:

- with a hook following the sleeve,

- only with a sleeve.

In the first embodiment, a hook 13 is fixed in the free end 12 of one of the bushings 11, which serves to attach a device (not shown) to it for introducing and subsequently removing the filter 1. The filter in the second embodiment can be introduced using a multi-foot extractor. All filter elements 1 are made of stainless steel.

Filter 1 is a self-centering dimensionless device for trapping blood clots, it is possible to remove it if necessary after a threatened period, the device can be implanted with any access (top or bottom). The device has good stability due to two cones and, accordingly, four levels of support (cannot deviate), increased filtering properties due to two consecutive filtering unidirectional cones, does not have “dead” zones (zones of stagnation of blood), has a short length (length in the bloodstream) , which is determined only by the stability conditions and the size (diameter) of the implantation device.

When implanting from top to bottom, it is possible to open one filter element and use it as a means for shifting down (transporting) a floating thrombus to ensure proper implantation of the entire product from the condition of its location below the renal veins.

The dimensionlessness and universality of the filter for introduction into any vessels of larger or smaller diameter is ensured by the selection of the length of the threads and the diameter of the wire from which they are made.

The claimed filter has the following advantages:

Firstly, it is self-centering and even with an external effect on a blood vessel (see figure 2) and when it is displaced, the fixing bushings and the tops of the cones of the filtering elements do not deviate from the central axis of the vessel, with this arrangement the blood clots settle in the center and break the strongest blood flow along the axis.

The filter is self-locking. First, as described above, the centering threads open, due to the greater curvature, they come into contact with the walls of the vessel and the filter is centered in the bloodstream along two centering planes, the centering threads do not penetrate deep into the vessel walls, since their ends are rounded or flat. Then, fixing threads with less curvature are deployed, due to the hooks at their ends, they are fixed to the vessel wall in two planes.

The filter is dimensionless. The dimensionlessness and universality of the filter for introduction into any vessels of larger or smaller diameter is ensured by the selection of the length of the threads and the diameter of the wire from which they are made.

The filter is deleteable. Removal is carried out with radiologically confirmed absence of fresh blood clots in the lumen of the vessel. Removal is performed under local anesthesia. A skin puncture or incision is made at the site of the catheterization, a device for fixation is put on the filter hook, and then the filter is separated from the place of fixation in the vessel by pushing it on the filter catheter of the device and then it is brought out by the usual method.

The filter is implanted equally successfully both by access from above and from below. With transclavicular implantation, a subclavian vein is punctured and the filter is passed through the right atrium to the site of installation. The operation is carried out after sedation and local anesthesia, under X-ray television control. It is advisable to carry out a control cavography or scan of the vessel before the introduction of the filter to detect parietal floating thrombi.

The claimed design of the filter allows you to provide:

- simple implantation with any access,

- simple deletion or rearrangement,

- a blood clot in the bloodstream by the lower filter element.

A number of successfully performed operations on implantation and removal of filters of the claimed design and clinical observations of patients indicate the high qualities and reality of the positive properties of the filter described above.

Claims (8)

1. Intravenous filter containing two unidirectional filter elements, consisting of arcuate curved elastic threads, the free ends of which diverge in circles to contact the inner surface of the vessel, and the other ends are assembled together by fixing sleeves connected by a rod, characterized in that each filter an element contains two sets of threads, each set includes an even number of threads, the threads of the first set are centering, designed to center the filter in a blood vessel and are located between the threads of the second set - fixing, designed to fix the filter in a blood vessel, the free ends of the fixing threads end with fixing elements, while the rod is flexible, and many centering threads can contact the free ends of the threads with the inner surface of the blood vessel until the fixing threads and the occurrence of contact between the free ends of the fixing threads and vessels. 2. The intravenous filter according to claim 1, characterized in that the locking elements at the ends of the fixing threads are made in the form of hooks for fixing to the vessel wall or in the form of sharpening elements, which are pointed ends. 3. The intravenous filter according to claim 1, characterized in that the free ends of the centering threads are rounded or flat. 4. The intravenous filter according to claim 1, characterized in that the centering threads of the two filter elements are configured to form two centering planes in contact with the inner surface of the blood vessel. 5. The intravenous filter according to claim 1, characterized in that the fixing threads of the two filter elements are configured to form two fixation planes upon contact and insertion of the fixing elements into the inner surface of the blood vessel. 6. Intravenous filter according to claims 1, 2 or 3, characterized in that the radius of curvature of the fixing threads is less than the radius of curvature of the centering threads. 7. An intravenous filter according to any one of the preceding paragraphs, characterized in that a hook is attached to the free end of the fixing sleeve for fixing the implantation and removal device. 8. Intravenous filter according to any one of the preceding paragraphs, characterized in that the threads and fixing sleeves are made of stainless steel.

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