DEVICES FOR RESTORING BLOOD FLOW WITHIN BLOCKED VASCULATURE
The devices and methods described herein relate to clearing of blockages within body lumens, such as the vasculature, by addressing the frictional resistance on the obstruction prior to attempting to translate and/or mobilize the obstruction within the body lumen.
This application is a non-provisional of U.S. Provisional Application No. 60/765,496 filed Feb. 03, 2006 which is incorporated by reference in its entirety.
FIELD OF THE INVENTIONThe devices and methods described herein relate to clearing of blockages within body lumens, such as the vasculature, by addressing the frictional resistance on the obstruction prior to attempting to translate the obstruction within the body lumen. In one variation, the devices and methods described below may treat conditions of ischemic stroke by remove blockages within arteries leading to the brain. Accordingly, variations of such methods and devices must navigate tortuous anatomy and vasculature without causing unacceptable damage to the anatomy. Also, the devices and methods first secure and surround the obstruction (such as a clot) prior to significantly moving the clot within the anatomy.
BACKGROUND OF THE INVENTIONIschemic stroke occurs when a blockage in an artery leading to the brain causes a lack of supply of oxygen and nutrients to the brain tissue. The brain relies on its arteries to supply oxygenated blood from the heart and lungs. The blood returning from the brain carries carbon dioxide and cellular waste. Blockages that interfere with this supply eventually cause the brain tissue to stop functioning. If the disruption in supply occurs for a sufficient amount of time, the continued lack of nutrients and oxygen causes irreversible cell death (infarction). Accordingly, immediate medical treatment of an ischemic stroke is critical for the recovery of a patient.
The infarction may not develop or may be greatly limited given a rapid clearing of the blockage to reestablish the flow of blood. However, if left untreated, ischemic stroke may lead to the permanent loss of brain tissue, and can be marked by fall or partial paralysis, loss of motor control, memory loss, or death.
Several different diseases may lead to an ischemic stroke. Typically, deposition of cholesterol (artherosclerosis), formation of blood clots, or other objects in the vessels may disrupt blood flow and lead to ischemic stroke. Furthermore, the substances that cause the blockages may break free from larger vessels outside the brain and become lodged within narrower arteries closer to the brain (embolism).
Ischemic stroke may be divided into thrombotic strokes and embolic strokes. A thrombotic stroke occurs when the building and rupturing of atheromatous plaque within the brain blocks cerebral arteries. Clinically referred to as cerebral thrombosis or cerebral infarction, this condition represents approximately 10% of all strokes. An embolic stroke occurs when a clot or emboli forms somewhere other than in the brain, such as in the cervical carotid artery or in the heart, and travels in the bloodstream until the clot becomes lodged and can not travel any further. When such a condition occurs in the arteries supplying the brain, the condition results in almost immediate physical and neurological effects.
While these are the most common causes of ischemic stroke, there are many other possible causes. Examples include use of drugs, trauma to the blood vessels of the neck, or blood clotting disorders.
Apart from surgical techniques, medical practitioners could address such blockages with the use of Tissue Plasminogen Activator (t-PA). However, t-PA must be used within the first three hours of the onset of stroke symptoms and may take hours or even days to successfully restore flow. In addition, t-PA carries an increased risk of intracerebral hemorrhage. It is currently believed that the use of t-PA results in a 30% success rate as well as a 6% major complication rate. In view of these limitations, the majority of stroke patients in the U.S. do not receive t-PA treatment.
In addition, there are a number of surgical techniques used to remove blockages. For example, an embolectomy, involves incising a blood vessel and introducing a balloon-tipped device (such as the Fogarty catheter) to the location of the occlusion. The balloon is then inflated at a point beyond the clot and used to translate the obstructing material back to the point of incision. The obstructing material is then removed by the surgeon. Concentric Medical, Inc. of Mountain View, Calif. supplies devices for an interventional approach to the removal of obstructions. Concentric supplies a Merci® Retriever system as a device based approach for the removal of clots. This system engages and ensnares a clot. Once captured, a balloon catheter inflates to temporarily halt forward blood flow while the clot is withdrawn. The clot is then pulled into the catheter and out of the body.
Typically, the existing means to remove obstructions do not address the frictional forces that act on the obstruction during removal of the obstruction. For example, some conventional devices engage the clot from the distal (or downstream) side. As the device is pulled proximally (or upstream), the device attempts to either engulf or ensnare the clot. However, due to the consistency of the clot and because the clot is typically well lodged within the vessel, the act of pulling the clot in a proximal direction cause the clot to also compress in an axial direction. This axial compression (when viewed along the axis of the vessel) causes a contemporaneous radial expansion of the clot (when viewed relative to the vessel). As a result, the increase in diameter of the clot causes an increase in the frictional forces applied against the arterial wall. Thus, by not addressing the frictional forces acting on the obstruction, the process of removing the clot may actually increase the static force that would otherwise be required to remove or translate the clot within the vessel. Unfortunately, increasing the amount of force applied upon one side of the clot also increases the probability of complications during the procedure (e.g., fragmenting the clot, failing to remove the clot, failure to fully engulf/ensnare the clot, and/or device failure) and can cause potential damage to the surrounding vessel.
While there are other drugs and suppliers of devices for removal of blockages, there remains a need for methods and devices that improve the success rate and/or reduce the complication rate in restoring flow and thereby limit the damage from an ischemic stroke.
SUMMARY OF THE INVENTIONIt should be noted that the present methods and devices may be used to treat blockages leading to ischemic stroke as well as to treat blockages (caused by “obstructions”) within other parts of the body (i.e., unless specifically noted, the devices and methods are not simply limited to the cerebral vasculature). The term obstructions may include blood clot, plaque, cholesterol, thrombus, naturally occurring foreign bodies (i.e., a part of the body that is lodged within the lumen), a non-naturally occurring foreign body (i.e., a portion of a medical device or other non-naturally occurring substance lodged within the lumen.)
In one variation of the devices described herein, the device allows for surrounding the obstruction prior to attempting to translate or move the obstruction within the vessel. It should be noted that although minimal axial movement of the obstruction may take place, the device surrounds the obstruction before such movement causes significant distortion to the geometry of the obstruction resulting in an increase in the static force required to remove the obstruction from the vessel.
In another variation of the device, the device may include a low friction mode (such as a set of parallel wires, or wires extending axially along the lumen or vessel) that converts to an increased friction mode (such as a compressed set of wires acting on the obstruction or a twisted set of wires acting on the obstruction). The increase in friction is an increase in the friction between the obstruction and the device (as opposed to the vessel wall. In some cases, the low friction modes is a low surface area mode and the high friction mode is a high surface area mode. When configured in the low friction mode, the device is better suited to engage the obstruction without the undesirable effect of prematurely mobilizing the obstruction or compacting the obstruction (e.g., when wires are slid across the obstruction in a transverse motion). Upon engaging the obstruction, the device will conform to a high friction mode with respect to the obstruction (in some cases the device will have an increased surface area mode). This high friction mode permits the device to better grip the obstruction for ultimate removal of the obstruction.
The operation of the devices and method described herein secure the obstruction, overcome the elastic forces of the obstruction, then remove the obstruction from the anatomy without losing or fractionating the obstruction. In one variation of the invention, this is accomplished by the obstruction removal device interacting with the obstruction in the following manner: (1) the traversing filaments traverse the obstruction by passing either through the obstruction or between the obstruction and the vascular wall; (2) the traversing portion is pulled proximally to engage the surrounding portion of the device around the obstruction, the surrounding portion engaging the obstruction without causing significant mobilization of the obstruction; (3) the obstruction removal device is pulled further proximally and the surrounding portion now mobilizes the obstruction.
As shown below, variations of the devices have a configuration that provides a path for a portion of the device to surround the obstruction. The paths are made using traversing filaments that allow for low frictional translation of a surrounding portion of the device over the obstruction without causing axial translation of the obstruction. This mechanism is described in more detail below.
Once in the proper position, a portion of the device (e.g., a surrounding portion) increases the frictional contact with the obstruction to disperse the pulling force more evenly across the obstruction. The increase points of contact allow for removal of the obstruction through tortuous anatomy while ensuring that the obstruction will not escape the encapsulation.
The surrounding portion may be fabricated in a variety of ways. For example, the surrounding portion may comprise one or more filaments. The surrounding portion may comprise a filter/bag, a coil, helical filament, a mesh structure, corrugated sheet, braided filaments, single wound or crossing filaments, tubes, membranes, films, solid wires, filled tubes, castings. Furthermore, the surrounding portion may have one or more ports, openings, slits, and/or holes. The surrounding portion may be made by photochemical etching, mechanical drilling, weaving, braiding, laser cutting, or other means.
It should be noted that reference to surrounding or securing the obstruction includes partially and/or fully surrounding, engulfing, encapsulating, and/or securing the obstruction. In any case, the surrounding portion engages the obstruction prior to translation of the obstruction within the lumen. As noted herein, a portion of the device may convert into a surrounding section (e.g., when traversing wires reorient to increase the friction acting on the obstruction). Accordingly, the traversing section converts into a surrounding section.
The various devices described herein rely on a reduced profile for delivery and an expanded profile for ultimate removal of the clot. The devices, or components of the devices, may expand when released from a constraint, which allows the device, or component, to assume a predetermined shape. Alternatively, or in combination, the devices may be actuated to assume the expanded profiles. For example, the devices may be shape memory alloys that assume a profile when reaching a predetermined temperature (e.g., body temperature, or another temperature via delivery of energy to the shape memory alloy to trigger a phase change). Actuation may also include use any expandable member (such as a coiled spring, balloon, wedge, etc.) that mechanically or fluidly forces expansion of the device. These modes are well known by those skilled in the art and are intended to be within the scope of the disclosure. When combined with the inventive concepts disclosed herein, such combinations fall within the inventive scope of this disclosure.
As noted above, the filaments of the invention may be used to translate the device or may be used to form the surrounding section. Accordingly, the filaments may be single wound or crossing filaments, tubes, membranes, films, solid wires, filled tubes, castings or any similar structure. Moreover, the cross section of such filaments may vary as required (e.g., circular, oval, rectangular, square, or any such shape.) The filaments may be constructed from metals, polymers, composites, hydrogels, membranes, shape memory metals, shape memory polymers, or shape memory alloys, superelastic metals, superelastic polymers, or superelastic alloys, or combinations thereof. The filaments may have uniform diameters or varying diameters. The characteristics of the filament may be selected to better suit their required function. For example, they can be stiff, floppy, or even have different zones of flexibility. Moreover, the filaments may be braided or woven members, or the construction may provide that the filaments cross at one or many points in an overlapping, interwoven, crisscrossing or similar manner.
It should be noted that in some variations of the invention, all or some of the filaments (used in the surrounding portion of the device) can be designed to increase their ability to adhere to the obstruction. For example, the filaments of the surrounding portion may be coupled to an energy source (e.g., RF, ultrasonic, or thermal energy) to “weld” to the obstruction. Application of energy to the filaments may allow the surrounding portion to deform into the obstruction and “embed” within the obstruction. Alternatively, the filaments may impart a positive charge to the obstruction to partially liquefy the obstruction sufficiently to allow for easier removal. Alternatively, a negative charge could be applied to further build thombus and nest the device for better pulling force. The filaments may be made stickier by use of a hydrophilic substance(s), or by chemicals that would generate a chemical bond to the surface of the obstruction. Alternatively, the filaments may reduce the temperature of the obstruction to congeal or adhere to the obstruction.
BRIEF DESCRIPTION OF THE DRAWINGSEach of the following figures diagrammatically illustrates aspects of the invention. Variation of the invention from the aspects shown in the figures is contemplated.
It is understood that the examples below discuss uses in the cerebral vasculature (namely the arteries). However, unless specifically noted, variations of the device and method are not limited to use in the cerebral vasculature. Instead, the invention may have applicability in various parts of the body. Moreover, the invention may be used in various procedures where the benefits of the method and/or device are desired.
It is noted that any number of catheters or microcatheters maybe used to locate the catheter/microcatheter 12 carrying the obstruction removal device (not illustrated) at the desired target site. Such techniques are well understood standard interventional catheterization techniques. Furthermore, the catheter 12 may be coupled to auxiliary or support components 14, 16 (e.g., energy controllers, power supplies, actuators for movement of the device(s), vacuum sources, inflation sources, sources for therapeutic substances, pressure monitoring, flow monitoring, various biochemical sensors, bio-chemical substances etc.) Again, such components are within the scope of the system 10 described herein.
In addition, devices of the present invention may be packaged in kits including the components discussed above along with guiding catheters, various devices that assist in the stabilization or removal of the obstruction (e.g., proximal-assist devices that holds the proximal end of the obstruction in place preventing it from straying during removal or assisting in the removal of the obstruction), balloon-tipped guide catheters, dilators, etc.
The connectors 108, 110 and/or traversing filaments 112 are designed to expand to the wall of the vessel when released from the catheter. This action allows the device 100 to surround the obstruction 2 prior to attempting to dislodge it. The components of the obstruction removal device 100 (e.g., the leading wires 106, the connectors 108 110, the traversing filaments 112, and/or the surrounding portion 114) may be fabricated from any biocompatible material that permits the function as described herein. In some variations, the material may comprise a shape memory or super-elastic alloy such as nitinol.
As discussed herein, the obstruction removal devices include a plurality of filaments affixed between connectors. Since the far connector 110 is deployed at the distal side 4 of the obstruction 2, withdrawal of the microcatheter 102 results in the plurality of filaments 112 spanning across the obstruction 2 as shown.
Spacing the filaments may occur via a number of modes such as tensioning, expanding, spreading separating and/or withdrawing the filaments. In certain variations of the device, the filaments are moveable relative to a near connector and/or a far connector. Such a feature allows application of tension to the filaments while keeping the connector in place. This causes the filament to enter a state of tension for spacing about the wall of the vessel. Alternatively, the filaments may be fixed relative to the connectors. Upon deployment the filaments either self expand or are actuated to space about the vessel wall for eventual translation of the device over the obstruction. Regardless of the mode used, the filaments are intended to be positioned at or near a surface of the obstruction so that they can reduce the effects of any friction between the obstruction and the lumen or vessel wall.
Although the variation shows only four traversing wires 112 any number of wires may be used so long as the rotation converts the traversing wires 112 into a relatively increased friction mode as compared to the low friction mode (when the traversing wires are in a parallel configuration). The low friction mode is represented by
The rotation of the connector 108 can be performed in any number of ways as known to those skilled in the art. However, as shown in
In
The variation of
In this variation, the obstruction removal device 100 includes leading filaments 106 connected to a near connector 108. In this example, the lead filament 106 may be a single wire or filament. Alternatively, the lead filament may comprise a single wire with a plurality of wires connecting the single wire to the ring.
As with the above examples, the illustrated variation shows the connector 108 as comprising a loop. However, as described herein, the connectors may also comprise various alternate shapes (e.g., a circle, an arcuate shape, a partial circular shape, a loop, an oval, a square, a rectangle, a polygon, an overlapping loop, a pair of semi-circles, a flower shape, and a
As shown, this variation of the obstruction removal device 120 includes two sets of traversing filaments 122, 124 and accompanying connectors 108, 110, and 126, 128. The first set 122 comprises a first near connector 108 and first far connector 110 with the accompanying traversing filaments. The second set 124 comprises the second near connector 126 and second far connector 128 with the accompanying traversing filaments 124. The second set 124 is coaxially located over the first set 122. The materials of the components may be as described above. In any case, the components are designed to. expand to the perimeter of the vessel wall upon release from the catheter.
In another variation, the devices described herein may be assembled or constructed in-situ. For example, components of the device may include connectors, portions of the connectors, traversing elements, and/or surrounding sections. Any combination of these components can be placed in sequential fashion. Doing so forms a completed structure from deployment of a number of individual components. The end result is the formation of a device as shown in the figures. Accordingly, such components of the device may be separately deployed in a manner that requires “assembly” of the components by a medical practitioner during the procedure.
In another example, the device may be fabricated from a polymer composite that makes up the fasteners, filaments, bags, etc. where the polymeric composite is very floppy until it is exposed to either the body fluids and or some other delivered activator that causes the polymer to further polymerize or stiffen for strength. Various coatings could protect the polymer from further polymerizing before the device is properly placed. The coatings could provide a specific duration for placement (e.g., 5 minutes) after which the covering degrades or is activated with an agent (that doesn't affect the surrounding tissues) allowing the device to increase in stiffness so that it doesn't stretch as the thrombus is pulled out. For example, shape memory polymers would allow the device to increase in stiffness.
Another aspect applicable to all variations of the devices is to configure the devices (whether the traversing filament or the surrounding portion) for better adherence to the obstruction. One such mode includes the use of coatings that bond to certain clots (or other materials causing the obstruction.) For example, the traversing filament and/or surrounding portion may be coated with a hydrogel or adhesive that bonds to a thrombus. Accordingly, as the surrounding portion covers the clot, or as the device twists about the clot, the combination of the additive and the mechanical structure of the device may improve the effectiveness of the device in removing the obstruction.
Such improvements may also be mechanical or structural. For example, as shown in
In addition to additives, the device can be coupled to an RF or other power source (such as 14 or 16 in
The methods described herein may also include treating the obstruction prior to attempting to remove the obstruction. Such a treatment can include applying a chemical or pharmaceutical agent with the goal of making the occlusion shrink or to make it more rigid for easier removal. Such agents include, but are not limited to chemotherapy drugs, or solutions, a mild formalin, or aldehyde solution.
Although not illustrated, the devices and methods described herein may also be useful in removing obstructions lodged within bifurcations in the anatomy. Generally, bifurcations greatly increase the frictional forces on the obstructions since the obstruction tends to be lodged in both branching sections of the bifurcation. In such cases, the use of the presently described devices and methods may also include an additional “puller” device that advances beyond the portion of the obstruction partially located in the bifurcated vessel.
As for other details of the present invention, materials and manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts that are commonly or logically employed. In addition, though the invention has been described in reference to several examples, optionally incorporating various features, the invention is not to be limited to that which is described or indicated as contemplated with respect to each variation of the invention.
It should be noted that any number of traversing filaments 112 or sets may be used in these variations.
In additional aspect of the invention, as shown in
In those variations with a mechanical expansion means, the expansion means may be located on the delivery catheter of the obstruction removal device, on a wire member of the device, and/or on a separate catheter or wire used in combination with the first delivery catheter. However, variations of such configurations are within the scope of the invention.
In addition, devices and methods described herein may also use balloons proximal to the obstruction to stop or slow blood flow thereby preventing the blood from dislodging part or all of the obstruction.
Various changes may be made to the invention described and equivalents (whether recited herein or not included for the sake of some brevity) may be substituted without departing from the true spirit and scope of the invention. Also, any optional feature of the inventive variations may be set forth and claimed independently, or in combination with any one or more of the features described herein. Accordingly, the invention contemplates combinations of various aspects of the embodiments or combinations of the embodiments themselves, where possible. Reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “and,” “said,” and “the” include plural references unless the context clearly dictates otherwise.
Claims
1-46. (canceled)
47. An intravascular apparatus for removing an obstruction from a vessel, the device comprising:
- a microcatheter having a size and flexibility to navigate within a neurovascular region of the patient;
- a near connector being self expanding and having a first expanded profile when unconstrained, such that on deployment in the vessel the near connector self expands towards the first expanded profile;
- a far connector being collapsible to fit within the microcatheter and being self-expanding to assume a second expanded profile when unconstrained, such that on deployment in the vessel the second connector expands towards the second expanded profile and expands within the vessel;
- at least one lead filament coupling the near connector to the microcatheter;
- a plurality of traversing filaments extending between the near and far connectors, and spaced apart on each connector such that spreading the traversing filaments causes the filaments to move towards an exterior of the obstruction; and
- a blood permeable filter member affixed to the far connector, the blood permeable filter being collapsible to fit within the microcatheter and self-expanding to expand in the vessel upon deployment.
48. The intravascular apparatus of claim 47, where the blood permeable member comprises a structure selected from the group consisting of a basket, a filter, a bag, a coil, a helical wire structure, a mesh, a corrugated sheet, a braided wires, a single wound wire, a plurality of crossing wires, a tube, a membranes, and a film.
49. The intravascular apparatus of claim 47, further comprising a plurality of hook shaped members located on the blood permeable member.
50. The intravascular apparatus of claim 47, further comprising a third connector located adjacent to the near connector, and a plurality of non-rotating filaments extending between the far connector and the third connector, where the first connector is rotatable relative to the far and third connectors to cause the plurality of traversing filaments to form a helical pattern.
51. The intravascular apparatus of claim 47, where the near connector comprises a shape selected from a circle, an arcuate shape, a partial circular shape, a loop, an oval, a square, a rectangle, a polygon, an overlapping loop, a pair of semi-circles, a flower shape, and a FIG. 8.
52. The intravascular apparatus of claim 47, where the far connector comprises a shape selected from a circle, an arcuate shape, a partial circular shape, a loop, an oval, a square, a rectangle, a polygon, an overlapping loop, a pair of semi-circles, a flower shape, and a FIG. 8.
53. The intravascular apparatus of claim 47, where the first expanded profile comprises an arcuate shape.
54. The intravascular apparatus of claim 47, further comprising a plurality of hook shaped members located on at least one filament.
55. The intravascular apparatus of claim 47, where the near connector is collapsible to fit within the microcatheter.
56. The intravascular apparatus of claim 47, where the near connector is affixed to an exterior of the microcatheter.
57. The intravascular apparatus of claim 47, where the near connector comprises a plurality of near connector portions.
58. The intravascular apparatus of claim 57, where at least one of the near connector portions is axially spaced from another near connector portion.
59. The intravascular apparatus of claim 47, where the far connector comprises a plurality of far connector portions.
60. The intravascular apparatus of claim 59, where at least one of the far connector portions is axially spaced from another far connector portion.
61. The intravascular apparatus of claim 47, further comprising at least one support ring within the filament.
62. The intravascular apparatus of claim 47, where the a near connector, the lead filament, and the plurality of traversing filaments, are collapsible to fit within the microcatheter and are self-expanding upon deployment from the microcatheter.
63-167. (canceled)
Type: Application
Filed: Mar 9, 2007
Publication Date: Aug 9, 2007
Inventors: Brian Martin (Boulder Creek, CA), Martin Dieck (Menlo Park, CA)
Application Number: 11/684,535
International Classification: A61B 17/26 (20060101);