Patent Application
20190223995
Filters for capturing particles from the blood stream are used in many interventional procedures and embodiments. Physicians say the key factors in choosing embolic protection filters are their ability to maintain perfusion, be effective in capturing emboli, a low profile, deliverability, retractibility and the ability to recover all the collected debris. Particles that have dimensions above a given critical size have to be trapped in order to prevent serious damage downstream. They can cause acute problems in organs like heart, brain, lungs, kidneys and others. Most filters are placed by means of delivery from a catheter sheath. Some filters stay in the body forever, like some vena cava filters, but in many cases they are only for temporary use and have to be retrieved. This is done by means of a retrieval sheath that is advanced over a guide wire that is attached to the proximal side of the filter. (In this description proximal means the side where the operator stands).
Therefore retrieval is easy in such cases, because the filter mouth, where the particles enter the filter, is also located at the proximal side of the operator. However, until now there was no solution for closing a filter mouth on the distal side of the operator, when filters are placed in a direction where the blood flows towards the operator. The present disclosure brings a solution for placing filters in these cases.
Filters may be used alone, in combination with balloon angioplasty or stenting or in combination with placement or replacement of a valve in a vein, artery or in the heart. Filter devices could protect patients' brains during not only trans arterial valve insertion, but also surgical aortic valve replacement, atrial fibrillation ablation and other left-heart procedures. Examples of other procedures that may cause the release of particles are the use of scoring balloons or lithotripsy balloons.
During a trans arterial valve insertion (TAVI) procedure balloon angioplasty of the native valve is followed by placement of a new valve. Normally a delivery sheath is withdrawn from the self-expanding stented valve in order to allow the full deployment of the valve. Alternatively a balloon expandable valve is placed, by inflating the balloon with the stented valve located on its outer surface. Such procedures should be done in combination with the use of a protection filter, in order to ensure entrapment of any emboli and other particles, dislodged during angioplasty and/or stented valve delivery. It is important that the side of the filter where the blood flow enters is closed first, before it is retrieved, in order to prevent squeezing out of particles upon reducing the outer dimensions of the filter, when it enters the retrieval sheath. However, in most cases the catheters that hold the balloon and/or valve have their distal end directed towards the blood flow direction. This makes it difficult to place a filter on a location more proximal, as seen from the operator's view. Several companies have developed additional catheters with a filter, but they do not have a solution for the closure of the distal entrance mouth of the filter before it is collapsed and retrieved.
Examples of existing embolic filters for TAVI operations are described in a website Dicardiology.com, specifically the Claret Medical Sentinel system, the Keystone Heart Triguard device, the Edwards Lifesciences Embrella deflector and the Emboline Inc. Prosheath embolic protection system.
Claret's Sentinel system is composed of a double embolic filter net, one for each carotid artery. The system combines a guidewire, support catheter and the two embolic nets into one catheter. Using a 6 French radial artery access point, the catheter is passed through the brachiocephalic artery into the aortic arch. There the tip is manipulated to make an extreme bend into the neighboring left common carotid artery and the first net is deployed just past the ostium inside the vessel. The second net is then deployed inside the brachiocephalic artery. These two filters only provide embolic protection for the brain, but do not stop debris that flows deeper into the descending aorta. One of the filters is closed first at the apex, so there is a risk of squeezing out debris upon retrieval.
Keystone Heart's Triguard device consists of a self-expanding nitinol frame covered in a mesh material to deflect emboli from traveling up any of the three vessels at the top of the aortic arch. It is deployed via a catheter introduced from the femoral artery. As the device is unsheathed, a nitinol stabilizing wire is expanded into the brachiocephalic artery to properly orientate the screen. A second stabilizing wire acts as a foot on the base of the device that touches the bottom of the aortic arch to help push the device upward to form a better seal against the top of the arch. After the procedure it is pulled back into the delivery catheter for removal. The net does not capture emboli, but does deflect it from the carotid vessels.
A third device discussed was the Edwards Lifesciences Embrella embolic deflector, which received European CE mark in 2010. The device is placed in the aorta through a sheath inserted in the right brachial or right radial artery. Its porous membrane allows blood flow to the brain while simultaneously deflecting embolic material. The device uses two self-expanding frames covered in a filter mesh, attached to a central catheter from which it is deployed and retrieved. This device is a deflector, similar to the Triguard device, and does not remove emboli from the body upon retrieval.
A fourth device, the Prosheath embolic protection system, deploys a large self-expanding stent structure with a filter mesh covering along the length of the aortic arch into the descending aorta. At the base of the device where it is attached to its deployment catheter, it uses a reversed funnel shaped filter to capture all emboli released during the procedure. It is capable of capturing all emboli released during TAVI procedures, because it deflects the emboli from the side arteries in the aortic arch into a location downstream into the aorta, where it is captured and retrieved in the filter part. However, in this device the filter is retrieved in a sheath from the proximal side, so the filter entrance is closed at the very end of the retrieval, which again may cause squeezing out of the captured particles.
All four devices are based upon an additional catheter holding the protection device. A separate catheter system is first placed before the procedure of angioplasty, stenting, placing a valve or whatever treatment is started. This costs extra equipment, operation time and it takes more place in the aorta. Moreover, there is always the risk of mechanical interaction between the protection device and the catheter that is inserted to do the TAVI procedure. Such mechanical interaction may lead to dislodgement of captured particles from the protection device or even an entanglement between the two devices which can cause huge problems.
There is still a need for an embolic protection system that is integrated with the treatment catheter, placed in the artery between the treatment site and the proximal operator and which can be closed and retrieved safely without the risk of squeezing out debris. Such a device can be used in many upstream procedures.
For downstream embolic protection in the carotid artery there is the Paladin device, having at its distal end a filter, integrated with a proximal angioplasty balloon on the same catheter, where the filter mouth is proximal and can be closed safely in such a downstream application. However, because of its construction this device cannot be used upstream and as of today there are still no devices that have a solution for closing the distal filter mouth.
Other filters for downstream use may include two filters on a single catheter such as that described in U.S. Pat. No. 6,485,502 by Don Michael and Besselink, in which several types of Nitinol frames are covered with a perforated polymer membrane, as well as one with a braided mesh with a specific pore size. In PCT Published Application WO 2004/026175 Besselink describes the use of fibers of high strength materials, embedded in polymer membranes to act as a reinforcement to enable the use of thinner membranes and prevent rupture and/or detachment from an expandable frame. These filters are also used as distal protection devices.
In one embodiment of the present disclosure, an embolic filtering system used to capture embolic debris in a body vessel with the blood flowing from the distal end towards the proximal end of the system is disclosed. The system includes an expandable and collapsible filter assembly with an expandable frame that can be moved between an expanded position and an unexpanded position, where the filter is disposed on a first tubular filter carrying catheter. A flexible filtering element is attached to and movable with the frame. The flow of unfiltered blood may be made to enter the filtering assembly at a first distal entrance side, while the filtered blood leaves the filter assembly at a second proximal exit side. The first filter carrying catheter has a proximal end outside the body and a distal section enclosed by the filter assembly with at least the distal end of the filter assembly being attached. A second tubular catheter is mounted coaxially with the first catheter and is movable in an axial direction relative to the first catheter. A reverse retrieval sheath is connected to the distal end of the second catheter, the sheath having a distal end portion and a proximal end, the distal end portion being connected to the second catheter and the proximal end portion of the sheath having an opening, adapted to maintaining the filter assembly in the unexpanded position, deliver the expandable filter assembly for release and being axially movable to collapse and retrieve the filter assembly, starting the collapse at the distal entrance of the filter; and a way for an operator to manipulate through attachment to the proximal ends of the first and second catheter in such a way to vary the relative axial position of both catheters.
In another embodiment of the present disclosure, a method of using an embolic filtering system is disclosed.
In procedures where a filter is placed upstream, with its entrance for blood holding particles distally from the operator's position, the principle of a reverse sheath can be used. Closure of the filter mouth will then start on the side where the blood enters and this ensures safe entrapment of emboli and other particles before the filter is completely collapsed and retrieved from the body. The reverse sheath is mounted near the distal end of a main catheter, and its opening for retrieval of the filter is located more proximal. Retrieval is achieved by pulling the main catheter with the reverse sheath in proximal direction over the filter frame, while holding the filter in its axial position by means of one or more retrieval wires that are connected to a central control element that is held still upon collapsing the filter. Alternatively the filter is held still in its axial position by a separate filter holder tube, which is placed over the main catheter that holds the sheath that is used for delivery and retrieval of the filter.
It will be understood that the reverse sheath can also be used in combination with other procedures. In the present description, examples are given for the use of such a reverse sheath, integrated with the same catheter device that is also used for angioplasty, stenting or valve replacement, but it can also be used separately besides these devices. For all kinds of upstream treatments resulting in the release of particles, valve tissue, arterial debris, calcification, thrombus or foreign material the filter with a distal blood entrance, eventually retrieved by means of a reverse sheath can provide protection. In another embodiment of a filter with a distal entrance, used in an upstream procedure, but where the room for using a reverse sheath is too small, an example is given of a filter that is expanded or collapsed by means of two concentric tubes, which are independently movable in axial direction. These concentric tubes can slide back and forth over the surface of a standard device for treatment in the patient's vascular system. The relative movement of both tubes cause a length change of the filter struts, resulting in a change of the outer diameter of the filter frame.
The integration of the catheter for any treatment at the distal end in combination with an embolic filter on the same catheter shaft safes precious operation time, reduces costs as compared to separate devices and avoids the risk of undesirable mechanical interaction, including entanglement between separate systems.
Other embodiments include filters with or without a retrieval sheath, either placed concentric or non-concentric over the catheter for upstream treatments in the patient's body.
In the present description, the term “proximal” means the side where the operator stands. Filters according to the disclosure are placed upstream, with the blood flow running from distal to proximal, as seen by the operator. The term “reverse sheath” is used to define a sheath that has its open side directed towards the operator, in contrary to conventional sheaths where the opening is directed distally. The reverse sheath needs to be connected to the main catheter in order to enable the operator to move the sheath back and forth over a central control wire. In a first embodiment the place of the connection between the main catheter and reverse sheath is realized with a perforated connection ring. The perforation through the wall of the ring is needed to guide at least one retrieval wire through, which is connected to an expandable filter frame on the proximal side. The distal end of the retrieval wire is either directly connected to the central control wire or via a control ring, attached on the central control wire at a location distally from the perforated ring. Axial sliding of the main catheter relative to the central control wire causes a movement of the retrieval wires in and out of the reverse sheath, thus enabling the operator to pull the filter frame into this sheath.
Examples are disclosed for use of a reverse sheath in a single filter, a filter in combination with a balloon and for a valve replacement under filter protection. Other examples show a sheathless filter for upstream protection, also in combination with a balloon catheter.
However, for all kinds of upstream treatments resulting in the release of particles, valve tissue, arterial debris, calcification, thrombus or foreign material the filter with reverse sheath can provide protection. Such treatments include intravascular imaging, angioplasty, ablation, use of drug-eluting balloons, scoring balloons, lithoplasty, ultrasonic treatments, placement of closing systems like Left Atrial Appendage Occluders and many more.
In one form, a central lumen may be made to extend all the way between the proximal and distal end of the system. In one form, a diagnostic or interventional treatment catheter may extend through the lumen. Likewise, in one form, the distal end of the treatment catheter may be placed at a location distally of the landing zone where the filter is placed. Moreover, the treatment may include procedures such as intravascular imaging, angioplasty, dissection, ablation, use of drug-eluting balloons, scoring balloons, laser cutting, drilling, reaming, dilating, lithoplasty, ultrasonic treatments, placement of stents, valves, stented valves, occluders, permanent filters and closure devices.
Single Filter
A first example present in this disclosure is based on a filter, used without additional treatment devices. A reverse sheath for retrieval of the filter is mounted on a perforated connection ring near the distal end of a main catheter, with its retrieval opening directed to the proximal end of this catheter. Closure of the filter mouth, where the blood enters the filter, is achieved by pulling the retrieval sheath in proximal direction over the filter. By doing this, the particles that are collected in the filter, cannot be squeezed out because the filter entrance is entirely closed now. During closing the filter must be held in place while the sheath is moved over the filter surface. Retrieval wires that are connected to the distal end of the filter frame and to a control ring, mounted on a central control wire hold the filter in place. These retrieval wires, running between the outer surface of the main catheter and the inner surface of the reverse sheath, leave the distal end of the main catheter through the perforations in the perforated connection ring and are directly attached to a control ring on the central control wire. Latter attachment may be by means of shape fit, crimping, welding, soldering, glue or any other conventional technique.
The distal section of the control wire may have a floppy or steerable end, dependent on specific applications. Further the control wire in all following examples may be solid or tubular, for example for insertion of a guide wire or injecting contrast fluid through its inner lumen.
When the control wire is held in place and the reverse sheath is moved to proximal, the retrieval wires are stretched and the tensile force in these wires pulls the filter into the gap between main catheter and reverse sheath. Any type of filter may be used in combination with a reverse sheath catheter according to the present disclosure. This includes nitinol frames with a perforated polymer membrane or vena cava filters entirely made of metal. Retrieval of the latter filter, where the apex of the filter is pulled into the reverse sheath would occur with the blood flow in distal direction, in contrary with the other examples.
The connection of sheath 130 to catheter 120 via ring 140 can be made by any known technique. In a specific example ring 140 may be one integrated part of the distal end of the main catheter. After placement of the retrieval wires the reverse sheath may be positioned on ring 140 and glued or crimped to its outer surface.
The elongated distal sheath 170 has a proximal end 171 and a distal end 172 and it can be used for delivery of other devices under the protection of the deployed filter downstream. The elongated sheath 170 can hold a stent or a stented valve, for example. Withdrawal of the sheath over the control wire 110 will push the stent out of distal end 172, while the reverse sheath moves simultaneously towards the filter mouth, which it will engage at its proximal end 131 first. (The filter itself is not shown here).
Retrieval of the filter is caused by holding the control wire 110 still and pulling the main catheter 120 into proximal direction.
This applies tension on the retrieval wire 151, finally causing deformation and collapse of the loop when it meets the proximal end of the reverse sheath. After the dimensions of the loop have changed enough, the moving sheath can enclose it completely. It may not be necessary to pull the entire filter membrane into the sheath, because closure of the loop is sufficient to prevent squeezing out of captured debris. The single retrieval wire 151 can be made of metal, like nitinol, but also may be made of a more flexible high strength polymer, which makes it possible to wrap it up in the gap between main catheter and retrieval sheath when the filter is loaded in the sheath before insertion into the patient. This can make the sheath shorter.
In the following
During use the blood enters through the wide open distal frame entrance and is then filtered by membrane or mesh 190.
The filter is brought in place in collapsed state. At the proximal ends of main catheter 120 and sheath 125, outside the patient's body, manipulators or stops 114 and 128 are attached. These manipulators enable the operator to hold and move the separate parts in a reliable and smooth way. Any tool may be used for this manipulation, and the manipulators are only depicted schematically as small rectangular stops in the figures.
In the shown examples of
Filter Holder Tube
In the examples described above a control wire inside the main catheter is used to pull the filter into the sheath by means of retrieval wires. Another example of an embodiment of the disclosure is given as device 700 in
The distance between the two rings 191 and 192 is sufficient to allow the filter frame to move easily in radial direction relative to the surface of the filter holder. Details associated with such filters are disclosed in patents EP1539031, JP4440787 and published US application 2006/015136 the details of which are incorporated by reference in their entirety. An important feature of the design is that the expanded filter frame ensures a perfect wall apposition, preventing any blood to pass around the filter mouth. Radial and tangential movements of the catheter in the bent aortic arch do not influence the shape and wall apposition of the filter frame, because the membrane and retrieval wires are extremely flexible. This eliminates most of potential mechanical interaction between filter and catheter. Normally the filter frame is made of laser cut Nitinol tubing with linear elasticity or superelasticity, but it will be appreciated that alternative materials may be used, and that all such variants are deemed to be within the scope of the present disclosure.
Therefore a slightly different design is showed in
The combination of main catheter and filter holder tube, eventually with the extra tube 197 can slide over a central guide wire, but also over a balloon catheter or a TAVI delivery catheter, for example. The balloon may be used for any procedure as described before. It may be a bare balloon, but it can also hold a balloon expandable stent, eventually in combination with a valve mounted to the stent frame (not shown here).
In
Filtration can still continue after deflation of the balloon and when the desirable filtration time has expired, the main catheter 120 can be pulled in proximal direction while the filter is held still with catheter 197.
The principle of a filter holder tube may be used in combination with various filter types. One example would be the filter with a loop frame like the one shown in
Balloon with Internal Retrieval Sheath
When there is not enough axial space available to place the filter frame in a proper landing zone, the device can be made shorter by combining the balloon with the sheath. This can be done by placing at least a part of the sheath inside the balloon, so that the sheath and balloon act together as an inflatable sheath.
In
Therefore, in another embodiment a more flexible sheath material inside the balloon section may be used. The sheath entrance 131 can still be more rigid, because it is outside the balloon. When the balloon is inflated, it will expand outside but it also pushes the enclosed sheath 130 against the outer surface of its underlying catheter 120, which is also used to pull the sheath over the filter after the balloon is deflated. When the material of the sheath is made elastically enough in radial direction, it can unfold or expand back to a similar diameter as the remainder of the sheath outside the balloon area, as soon as the balloon is deflated. By choosing the right compliance of the balloon and sheath material, eventually in combination with the use of reinforcement fibers, the behavior of this balloon/sheath combination can be optimized. In one example, the balloon material is elastic enough to maintain a circular cross section during the complete inflation/deflation process. Reinforcement fibers embedded in the balloon surface may limit the maximum balloon diameter to prevent burst. It may be clear that the sheath material must be able to withstand enough axial compression forces without buckling in order to be able to retrieve the filter.
When the deflated balloon/sheath is pulled into proximal direction in order to collapse the filter frame, the proximal opening of the sheath first encloses the filter mouth, and upon further axial withdrawal of the sheath also the flexible section of the sheath expands to its nominal size and takes up the remainder of the filter frame. With such a combined sheath/balloon a considerable gain is reached in the possible landing zone for a filter between the aortic valve and the brachio-cephalic artery. Other components in
Optionally a balloon catheter may also be provided with a perfusion lumen (not shown), if it has to be used for a longer period, for example when drug delivery from the balloon surface is taking time. An example of a such a perfusion balloon is described in U.S. Pat. No. 6,776,771 by Van Moorleghem and Besselink the details of which are incorporated by reference in their entirety. Such devices may be combined with a reverse sheath as described in the present disclosure.
The perfusion lumen can be used as a reverse sheath as well, similar to the examples of
Placing an Integrated Self-Expanding Stent or TAVI-Valve with a Filter
In this example the filter has to be placed further away from the proximal end of the stent than from the balloon in
The insertion state of the stent, valve and filter of the device is depicted in
A separate main catheter 120 with a reverse sheath 130 runs over valve delivery catheter 173. Main catheter 120 carries a filter holder tube 195 and a filter with frame 181, membrane 190 and retrieval wires 150, similar to the one described in
In
Then, as shown in
The filter can still stay open for some moments now, in order to enable the blood flow to flush all particles into the membrane. Finally, as shown in
If needed, the version described in
For a TAVI procedure the best location for placing the distal end of the filter frame is in the aortic arch, between the aortic valve and the brachiocephalic artery. The position of the perforated filter membrane itself is less relevant, because the filter frame holds the membrane entrance tightly against the aorta wall. So the membrane itself may either be located upstream of the entrance of the brachiocephalic artery, or cover it entirely or partly. In the latter case the perforations allow perfusion into the artery. Typical drilled circular perforations for protecting the brain against stroke are in the order of 100-120 microns in diameter, but other sizes and geometries, for example made by laser cutting, may be used as well. The hole geometry is also dependent on which filter is used. It may be a structure of fine metal or polymer wires made by any of well known techniques like braiding, crocheting, knitting, weaving or knotting, for example, and then the holes are not circular. Eventually the mesh structure may be dipped into a solution that contains glue, polyurethane or any other material, in order to secure the relative position of the fibers. This will prevent the undesired shape change of the perforations upon use. It is also possible that there are more than one filter frames, holding the filter membrane in place. The membrane can be attached to the frame in many ways, including suturing, laser bonding, laminating, embedding the frame struts between sandwich layers, welding, melting, gluing and so on.
The filter frame with attached fibers can also entirely be replaced by a metal frame such as Nitinol or the like. Instead of connecting the frame via flexible fibers to the catheter, the proximal and/or distal ends of the frame are directly connected to the catheter or filter holder tube, in order to enable delivery and retrieval. Of course, distinct frame sections need to have different functions. For example, the struts that run from the connection ring on the catheter to the section that supports the actual filter may have to be more flexible than the struts that are responsible for the radial expansion of the frame. Any filter design may be used in combination with a reverse sheath according to the present disclosure. Coatings on the contact surfaces can be used to reduce the friction.
Double Filter Frame Version
In all of the previous figures, only one filter frame is shown, but it is also possible to use a device with multiple frames.
Frames 184 and 185 may be frames similar to the ones described before, but now they are holding a relative long cylindrical perforated membrane 199 in between.
Frame 184 only holds the cylindrical membrane 199 open and firmly pressed to the inner aorta wall. It can be retrieved by pulling the main catheter 120 with the reverse sheath 130 over the frame by means of retrieval wires 150, as described before.
The second frame 185 is connected to the proximal end of cylindrical membrane 199. At the proximal side of the proximal frame 185 the apex of a conical membrane 190, like the one in
Such an elongated cylindrical membrane section 199 may be used to cover the entire upper aortic arch, including the entrances of the brachiocephalic artery, the left common carotid artery and the left subclavian artery. Membrane 199 actually does not capture debris, as it only prevents it to enter the three arteries. It acts as a deflector, guiding the debris to the conical filter 190, which is connected to the proximal side 189 of frame section 185 and which filters the remainder of the blood flow downstream the aorta.
Catheter 110 runs all the way from the proximal side until the distal end, where it is used for any procedure in the heart.
With a proper positioning of filter systems according to the disclosure it will give sufficient embolic protection for all arteries downstream. In this case the only arteries that do not have protection are the coronary arteries, because their entrances are located between the valve and landing zone for the filter in the aortic arch. The pore size of the conical membrane 190 may be identical as for the cylindrical membrane 199. However, for more protection against stroke the pore size of the cylindrical membrane 199 may be smaller than for the conical membrane 190.
The material of the reverse sheath may be relatively rigid, but can also be compliant. In the latter case it may work like the body of a snake that swallows a prey with a large size. As soon as the prey has passed the mouth of the snake, the outer diameter of the snake's head elastically returns to its normal size. If the entrance of the reverse sheath has a similar behavior, it becomes easier to get the filter frame into its collapsed state. Also, this entrance may have a small outside flare or taper to make withdrawal easier. It is also desirable to put marker bands on the reverse sheath and on the filter in order to be able to see the relative positions.
Filter with Non-Concentric Sheath
In the examples above the main catheter, the reverse sheath and the filter were always shown as concentric parts with a rotational symmetry, except for the example in
Filter without Reverse Sheath
The shapes of the filters, with or without any type of frames may be varied in numerous embodiments, but the examples given so far, with separate filter frame and retrieval wires, are just mentioned to show the function of the reverse sheath principle. Any combination of concentric or non-concentric devices having a main catheter plus reverse sheath for delivery and/or retrieval of any filter is meant to be part of the disclosure.
Besides the described embodiments with a reverse sheath, there is also an option to use many aspects of the examples above, but without a retrieval sheath.
Several options are possible in such an embodiment. In the example of
Alternatively the frame may be shape set in its stretched state, having its smallest delivery profile.
In the embodiments shown in
Example of a Prototype
Flexible fibers of UHMWPE (ultra-high molecular weight polyethylene), made by DSM in The Netherlands as Dyneema™, are extremely flexible and strong with a tensile strength of 20 times more than Nitinol. When the retrieval wires are made of 55 dTex fibers, the tensile strength is about 17 Newton. In the examples of prototypes according to
A TAVI catheter with a filter mounted on its surface should not have a larger profile than the existing catheter profile in order to prevent extra damage in the insertion site. If the reverse sheath profile has diameters of 6 mm OD by 5.6 mm ID it works well.
This means that the available space between the outer surface of the filter holder tube and inner surface of the reverse sheath is only 4.4 mm ID by 5.6 mm OD. In this gap, with a surface area of 9.4 mm2, the filter holder tube, connection ring, retrieval wires and self expanding frame, as well as the filter membrane must fit. Therefor it is important to keep the dimensions of all components as small as possible, and the use of reinforcement fibers for the membrane is helpful in order to minimize the thickness of the membrane while the strength and reliability is maintained. Samples were made with a membrane of polyurethane skin, with reinforcement fibers of Dyneema™. The membrane thickness was varied for different samples by choosing the amount of steps during the dipping process of a PTFE cone in a solution of polyurethane in THF (tetrahydrofuran). A typical final thickness of about 20-30 microns for the membrane works well for reaching enough stability. The conical filter membrane was connected to a nitinol frame with 6 cells and expanded diameter of 30 mm. The filterframe was laser cut from tubing of 4 mm by 3.4 mm diameter and shape set on 30 mm.
The total cross section surface area for a 30 mm diameter membrane of 30 microns is only 2.8 mm2 and for the frame it is 3.5 mm2, so frame and membrane together fit easily in the gap between reverse sheath and filter holder tube. Providing the surfaces with a hydrophilic coating further helps reducing the friction in order to achieve a smooth delivery and withdrawal of the filter.
Instead of using a dipped and perforated membrane, a Dyneema™ fabric with a density of 25 gram/m2 and a suitable pore size of about 100 microns can be used, because it is thin enough to fit in the reverse sheath together with the expandable frame. Another suitable mesh material may include a filter material made from fine-gauge nylon wires with well defined pore sizes.
Embodiments of the Disclosure
A reverse sheath may be used in any upstream procedure for opening up or widening of a more or less blocked artery, placing a stent or to prepare the annulus of a damaged heart valve for receiving a new valve. Such procedures include all types of diagnostic procedures or interventional treatments by means of a balloon, like drugs delivery from its surface or angioplasty, but also dissection methods for removing calcifications, stenosis, laser cutting, scoring balloons, lithotripsy systems and others. Balloon expandable stents or heart valve frames can be placed in combination with a filter with a reverse sheath according to the disclosure as well. One example is the TAVI-procedure where a heart valve is delivered. In particular, the procedure can be improved using the present filter as disclosed, by combining the delivery system for the valve with a filter as described on a single catheter. This saves costs, operation time, and reduces the risk as compared to using separate filtering devices.
As previously discussed, in one form, a central lumen may be made to extend all the way between the proximal and distal end of the system. In one form, a diagnostic or interventional treatment catheter may extend through the lumen. Likewise, in one form, the distal end of the treatment catheter may be placed at a location distally of the landing zone where the filter is placed. Moreover, the treatment may include procedures such as intravascular imaging, angioplasty, dissection, ablation, use of drug-eluting balloons, scoring balloons, laser cutting, drilling, reaming, dilating, lithoplasty, ultrasonic treatments, placement of stents, valves, stented valves, occluders, permanent filters and closure devices.
The balloon, filter and reverse sheath can be mounted on a common main catheter holding the same central control wire. Before inflation of the balloon the filter is pulled out of its delivery sheath. Optionally the filter is located inside the reverse sheath and a second filter delivery sheath and pulled out of both sheaths. One sheath may only contain the filter frame, while the other sheath contains the filter membrane. After deflation of the balloon the reverse sheath is pulled back, while the central control wire applies tension to the retrieval wires, finally causing the closure of the filter mouth. If needed, the remainder of the filter membrane may be collapsed by a second retrieval sheath, which is pushed forward over the first common catheter. However, full closure of the filter membrane may not be desirable and only closure of the filter mouth may be sufficient.
In another TAVI procedure a new heart valve in a self-expanding stent frame is placed inside the damaged original valve by means of a long catheter that is inserted through an incision in the patient's groin. One sheath delivers the valve, while a reverse sheath, coaxially located around the first catheter that holds the valve, delivers and retrieves the filter. Both sheaths can be moved independently. The filter is placed before the valve is deployed in order to capture any debris that may be dislodged during valve placement.
Besides balloon expandable TAVI-valves and self-expandable valves the disclosed filter can also be used in combination with other valve systems, such as those that have a frame that is mechanically expanded by axial contraction, followed by locking at the desired diameter. A catheter carrying a filter according to the present invention can be applied over the catheter that places this system.
The size and porosity of the filter membrane may be different for different types of procedures. In one embodiment the filter is only short and does not overlap with side arteries. It only filters the main stream in the aorta. In TAVI procedures the filter is preferably placed in the ascending aorta, between the valve annulus and brachiocephalic artery, in order to ensure protection against emboli entering the brains.
In another embodiment the filter is much longer and also covers the entrance of side arteries. In this embodiment the fine pores in the filter membrane allow the blood to enter into the side arteries, but emboli and other particles are deviated into the aorta and finally captured deeper into the filter.
In another embodiment the filter is connected to retrieval wires that run through side holes in the valve delivery sheath, these wires being connected to a ring that is mounted on a central control wire. During delivery of the valve the control wire is held in a fixed position, with the delivery sheath and stented valve located exactly in the area where the valve has to be seated. As soon as the valve delivery sheath is pulled back, the retrieval wires become stretched and the reverse sheath moves towards the filter opening. If delay is needed between valve delivery and filter closure, the device may be held in an intermediate position for a while, with the valve already in place.
Delivery of the valve is followed by closure of the filter in this way, using the same device, which can be removed from the patient then.
There may also be more than one expandable filter frame, mounted on the same catheter, for example when a long cylindrical filter membrane is located between two separate frame rings. In such cases the reverse sheath has to be long enough to be able to collapse both frames before retrieval, or retrieval can be done from two sides. First closing the distal filter mouth with the reverse sheath and finally closing the proximal frame with a conventional sheath, as will be described in the following examples.
In another embodiment a filter does not need a sheath for expansion or contraction. The filter catheter is placed on the catheter for treatment of the patient and the filter frame in expanded and collapsed by changing its length. The filter has its entrance for the blood is at the distal side and collects debris at the proximal side. Optionally a reverse sheath or a sheath from the proximal side may be used in combination with such a filter.
Filters according to the invention may be placed concentric or non-concentric on the catheter that is used for treatment in the patient's body.
For
For
For
It is noted that defined terms like “reverse sheath”, “main catheter”, “delivery sheath”, “concentric”, “filter holder” and others are not utilized herein to limit the scope of the disclosed subject matter or to imply that certain features are critical, essential, or even important to the structure or function of the disclosed subject matter. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present disclosure.
Likewise, for the purposes of describing and defining the present disclosure, it is noted that the terms “substantially” and “approximately” and their variants are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement or other representation, as well as to represent the degree by which a quantitative representation may vary without resulting in a change in the basic function of the subject matter at issue.
While certain representative embodiments and details have been shown for purposes of illustrating the subject matter of the present disclosure, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the disclosure, which is defined in the appended claims.
While certain representative embodiments and details have been shown for purposes of illustrating the disclosure, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the disclosure, which is defined in the appended claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/399,623, filed Sep. 26, 2016, U.S. Provisional Application Ser. No. 62/425,762, filed Nov. 23, 2016 and U.S. Provisional Application Ser. No. 62/458,646, filed Feb. 14, 2017.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2017/001344 | 9/25/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62458646 | Feb 2017 | US | |
| 62425762 | Nov 2016 | US | |
| 62399623 | Sep 2016 | US |
