The invention relates to an embolic protection device. 
The term xe2x80x9cSTROKExe2x80x9d is used to describe a medical event whereby blood supply to the brain or specific areas of the brain is restricted or blocked to the extent that the supply is inadequate to provide the required flow of oxygenated blood to maintain function.  The brain will be impaired either temporarily or permanently, with the patient experiencing a loss of function such as sight, speech or control of limbs.  There are two distinct types of stroke, haemorrhagic and embolic.  This invention addresses embolic stroke. 
Medical literature describes carotid artery disease as a significant source of embolic material.  Typically, an atherosclerotic plaque builds up in the carotid arteries.  The nature of the plaque varies considerably, but in a significant number of cases pieces of the plaque can break away and flow distally and block bloodflow to specific areas of the brain and cause neurological impairment.  Treatment of the disease is classically by way of surgical carotid endarterectomy whereby, the carotid artery is cut and the plaque is physically removed from the vessel.  The procedure has broad acceptance with neurological complication rates quoted as being low, somewhere in the order of 6% although claims vary widely on this. 
Not all patients are candidates for surgery.  A number of reasons may exist such that the patients could not tolerate surgical intervention.  In these cases and an increasing number of candidates that are surgical candidates are being treated using transcatheter techniques.  In this case, the evolving approach uses devices inserted in the femoral artery and manipulated to the site of the stenosis.  A balloon angioplasty catheter is inflated to open the artery and an intravascular stent is sometimes deployed at the site of the stenosis.  The action of these devices as with surgery can dislodge embolic material which will flow with the arterial blood and if large enough, eventually block a blood vessel and cause a stroke. 
It is known to permanently implant a filter in human vasculature to catch embolic material.  It is also known to use a removable filter for this purpose.  Such removable filters typically comprise umbrella type filters comprising a filter membrane supported on a collapsible frame on a guidewire for movement of the filter membrane between a collapsed position against the guidewire and a laterally extending position occluding a vessel.  Examples of such filters are shown in U.S. Pat.  No.  4,723,549, U.S. Pat.  No.  5,053,008, U.S. Pat.  No.  5,108,419 and WO 98/33443.  Various deployment and/or collapsing arrangements are provided for the umbrella filter.  However, as the filter collapses, the captured embolic material tends to be squeezed outwardly towards an open end of the filter and pieces of embolic material may escape from the filter with potentially catastrophic results.  More usually, the filter umbrella is collapsed against the guidewire before removal through a catheter or the like.  Again, as the filter membrane is collapsed, it will tend to squeeze out the embolic material.  Further, the umbrella filter is generally fixed to the guidewire and any inadvertent movement of the guidewire during an interventional procedure can dislodge the filter. 
The present invention is directed towards overcoming these problems. 
There is a need for an embolic protection device which will overcome this problem. 
According to the invention, there is provided an embolic protection device comprising:
a collapsible filter element mounted on a filter carrier for delivery through a vascular system of a patient,
the filter element being movable between a collapsed stored position against the filter carrier for movement through the vascular system, and an expanded position for occluding a blood vessel such that blood passing through the blood vessel is delivered through the filter element,
the filter element comprising a collapsible filter body having an inlet end and an outlet end,
the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body,
the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body,
means for closing the inlet openings at the inlet end of the filter body, and
means for collapsing the filter body on the support. 
Advantageously, the inlet openings in the filter are closed before the filter is collapsed ensuring retention of all embolic material within the filter element. 
In a particularly preferred embodiment of the invention, the means for closing the inlet comprises:
a tubular filter retrieval device having an open distal end for reception of the filter element,
said distal end being engagable with a proximal inlet end of the filter body to close the inlet openings and being slidable over the filter body from the inlet end to the outlet end to progressively collapse the filter body on the filter carrier and receive the filter body within the retrieval device. 
Conveniently, the retrieval device which may be a catheter or pod or the like which engages and collapses the filter element firstly closing the inlet openings to prevent any escape of embolic material and then collapsing the remainder of the filter, being slid from the proximal end over the filter to the distal end of the filter. 
In a particularly preferred embodiment, the collapsible filter element is slidably mounted on the filter carrier between the a pair of spaced-apart stops on the filter carrier for axial movement of the filter element along the filter carrier between the stops. 
Advantageously, the filter carrier which may for example be a guidewire can be moved independently of the filter element and thus accidental movement of the guidewire is accommodated without unintentionally moving the filter, for example, during exchange of medical devices. 
In a further embodiment, the filter element is rotatably mounted on the filter carrier. 
In a preferred embodiment, a sleeve is slidably mounted on the filter carrier between the stops, the length of the sleeve being less than the distance between the stops, the filter element being mounted on the sleeve. 
In a particularly preferred embodiment, the filter element comprises:
a collapsible filter net mounted on the filter carrier,
the filter net being movable between a collapsed stored position against the filter carrier and an expanded position extending outwardly of the filter carrier for deployment across a blood vessel. 
Preferably, the tubular filter retrieval device comprises a catheter slidable along the filter carrier, an open distal end of the catheter forming a housing for reception of the filter element. 
In another embodiment, a proximal inlet end of the filter body is fixed to the filter carrier and a distal end of the filter body is slidably mounted on the filter carrier, although this arrangement may be reversed. 
In a further embodiment, the distal end of the filter body is attached to a collar which is slidable along the filter carrier. 
In a preferred embodiment, a filter support frame is mounted on the filter carrier, the support frame being movable between a collapsed position along the filter carrier and an extended outwardly projecting position to support the filter body in the expanded position. 
In another embodiment, the filter support frame is fixed on the filter carrier at a proximal end of the filter body. 
Preferably, the filter support frame slidably engages the filter carrier at a distal end of the filter body.  Ideally, the filter support frame is biased into a normally extended position. 
In a further embodiment, a circumferential groove is provided in the filter body intermediate the ends of the filter body. 
In another embodiment, a guide olive is provided on the filter carrier distally of the filter body, the guide olive having a cylindrical body with a tapered distal end, the cylindrical body being engagable within a distal end of a deployment catheter, said tapered distal end projecting outwardly of the deployment catheter to provide a smooth transition between the catheter and the filter carrier. 
In a further embodiment, the net is gathered into the filter carrier at each end of the net. 
In another embodiment of the invention, there is provided an embolic protection device comprising a filter element for placing in a desired position, the filter element providing a pathway for blood and having means for capturing, retaining and removing undesired embolic material. 
In one embodiment of the invention, the pathway has means for constricting flow to capture undesired embolic material. 
In another embodiment of the invention, the filter has a proximal end and a distal end, openings in the proximal end being larger than openings in the distal end, the proximal end openings being sized to allow the flow of blood and embolic material to enter the filter element and the distal end openings being sized to allow the flow of blood while capturing undesired emboli within the filter element. 
In a further embodiment of the invention, the filter element includes storage means to store captured undesired embolic material in the filter element.  Preferably, the storage means comprises additional storage pathways within the filter element.  Preferably, the filter element defines a three dimensional matrix. 
In another embodiment of the invention, the filter element is of a polymeric porous structure.  In a further embodiment of the invention, the matrix comprises a porous structure dimensioned to entrap embolic material which typically ranges in size from about 100 microns to 3500 microns.  In a still further embodiment of the invention, the filter element is compressible and/or foldable for loading into a delivery device to deliver the filter element to a desired location in the compressed or folded state. 
In one embodiment of the invention, the filter element has material removed from its structure to aid compressibility. 
In another embodiment of the invention, the filter element has material removed from its structure to provide specific sizing in relation to the size of embolic material to be trapped. 
In a further embodiment of the invention, the filter element has pathways through the filter body that are inter-linked such that the flow rate through the filter may be tailored. 
In another embodiment of the invention, the filter element has a distal end which is tapered such that there is a smooth transition in lateral stiffness to improve the manoeuvrability of the filter element in the vascular system. 
In a further embodiment of the invention, the filter element has a soft distal portion to aid in atraumatic transport through the vascular system.  Preferably, the filter element has circumferential grooves to reduce the lateral flexibility of the filter element. 
In one embodiment of the invention, the filter element has a tapered proximal end to facilitate retrieval by a removal catheter. 
In another embodiment of the invention, the filter element has inlet holes that close on pulling back into a retrieval catheter to ensure retention of any collected emboli. 
In a further embodiment of the invention, the filter element has outlet openings sized to capture embolic material of a size large enough to impair the function of the organ receiving the blood downstream of the filter body element.  Preferably, the filter element is sized to capture embolic material of a size greater than 100 microns.  Most preferably, the filter element is sized to capture embolic material of a size greater than 200 microns.  Most preferably, the filter element is sized to capture embolic material of a size greater than 500 microns. 
In one embodiment of the invention, the filter element is sized for complete coverage of a vessel cross-section that allows passage of blood and blood components. 
In a still further embodiment of the invention, there is provided a device having means for placing over a medical guidewire. 
In another embodiment of the invention, there is provided a device which may be placed under a balloon or stent delivery catheter. 
In a further embodiment of the invention, there is provided a device having means for insertion through, femoral, brachial, radial, subclavian or other arterial puncture by means of a transcatheter approach. 
In one embodiment of the invention, there is provided a device for protection of neurological function which is inserted for the duration of a surgical intervention at or near the site of surgical opening. 
It is envisaged that two devices could be used bi-laterally in left and right carotid arteries allowing sufficient cerebral blood flow to maintain neurological function during procedures with a high risk of generating clot such as electrophysiological treatment of coronary arrhythmias. 
In a further embodiment of the invention, there is provided a device including a delivery catheter in which an external sheath is engagable with the filter element or filter carrier to provide push during delivery and is removable to allow maximum space in the vascular cross-section during an interventional procedure. 
In one embodiment of the invention, the external sheath is joined to the filter element or filter carrier by a joining means.  The joining means may be a removable shrink tube or a removable clip.  Preferably the joining means is a compression connector such as a Tuohy Borst adapter. 
In another embodiment of the invention, the delivery catheter has a central lumen for at least part of it""s length to allow it to track over a steerable guidewire. 
In a further embodiment of the invention, the external sheath is sufficiently long to extend to the outside of the vasculature and is movable proximally to release the filter element from the catheter. 
In one embodiment of the invention, the delivery catheter has an external covering which extends beyond the push element to define a filter retention sleeve. 
In another embodiment of the invention, the delivery catheter has a spring component with a localised stepwise increasing pitch to alter stiffness characteristics to suit the target vasculature. 
In a further embodiment of the invention, the delivery catheter has a spring component with a localised gradually increasing pitch to alter stiffness characteristics to suit the target vasculature. 
In one embodiment of the invention, the filter element is mounted on a collapsible support structure which is movable between a collapsed position for deployment and an extended in-use position, means being provided for retaining the support structure in the collapsed position.  Preferably, the support structure comprises support arms.  Preferably, the support arms are formed from a shape memory or elastic memory material.  Most preferably, the support arms are formed from Nitinol. 
In one embodiment of the invention, the support arms are configured to open co-axially with the filter carrier such that they may be restrained for removal by pulling the filter element proximally into an appropriately dimensioned sheath. 
In another embodiment of the invention, the filter element has an associated support structure with a pre-shaped spiral arrangement such that it provides radial support to the filter element. 
In a further embodiment of the invention, the filter support structure is adapted to fold into the collapsed position when pulled into a retrieval catheter. 
In one embodiment of the invention, the filter element comprises a flexible shaped polymeric component. 
In another embodiment of the invention, the shaped polymeric component is constructed such that fluid flow through the component assists in opening the component from the collapsed position. 
In a further embodiment of the invention, the shaped polymeric component is flexible and opens to make cicumferential contact with the vessel wall by way of using the pressure drop across the exit filter face. 
In a further embodiment of the invention the filter element is mounted on a guidewire such that the guidewire has freedom to rotate and/or move axially independently of the filter.  More preferably the wire has complete freedom to rotate independently of the filter and has limited axial movement.  The limit of axial movement is determined by stops mounted on or connected to the wire.  Ideally the wire can move 100 mm in the axial direction independent of the filter.  More ideally the wire can move less than 50 mm independently of the filter.  This embodiment facilitates the maintenance of filter position during the exchange of catheters and permits the steering of the wire independent of the filter. 
In a further embodiment of this invention the filter element is bonded to the filter mount at its proximal end and its distal end is free to move relative to the filter mount and proximal bond so as to aid the collapse of the filter for deployment. 
In a further embodiment of the invention the filter element is tapered over part or all of its length such that it is accurately sized to the vessel over some portion of its length. 
In a further embodiment of the invention the shaped polymeric component contains one or more circumferential grooves along its body to maintain the circular shape of the filter element in an under sized artery. 
In one embodiment of the invention, the filter element is directly bonded onto a steerable medical guide wire incorporating a slidable sheath that is movable to deploy the filter. 
In another embodiment of the invention, there is provided a device incorporating a medical guidewire with a flexible segment of wire distal to the filter so as to provide steerability of the wire particularly prior to it being deployed. 
In a further embodiment of the invention, there is provided a device incorporating a medical guide wire with a soft distal segment so as to provide a tip section that will be atraumatic. 
In a still further embodiment of the invention, there is provided a device with a porous coating on a distal end of the filter element only with a means for opening and closing the filter by slidable motion. 
In one embodiment of the invention, the filter element incorporates proximal tapering such that it may be pulled proximally into a sheath for removal in order that such pulling action will effectively reduce the diameter of the filter and assist retrieval. 
In another embodiment of the invention, the filter element has a porous structure that can be deployed and closed by way of a slidable motion, the closure thereof caused by way of snap-fit to a protruding rim that allows the support elements be pulled proximally, thus closing the structure with the filter membrane attached. 
In a further embodiment of the invention, there is provided a device having a filter element which permits the incorporation of a medical guide wire in the outer wall of the filter element to facilitate the incorporation of large inlet holes on the proximal inlet end of the filter element. 
In one embodiment of the invention, the filter element comprises a mesh work structure with large proximal inlet holes and small distal outlet holes wherein the mesh structure is collapsible into a small diameter delivery catheter and is expandable upon deployment to a shape which is remembered by the mesh structure either through shape memory characteristics or elastic memory characteristics. 
In another embodiment of the invention, the filter element comprises a mesh work structure wherein the expansion of the filter element within the vessel causes blood flowing through the vessel to flow through the filter element due to the filter element engaging with the wall of the vessel to conform to the shape of the vessel bore. 
In another embodiment, the filter element comprises a braided fibrous mesh work.  Preferably, distal outlet openings are defined by an area enclosed by a series of crossing interwoven fibres.  Larger proximal inlet holes are provided by the convergence of the fibres of the braid into a few bundles which are mounted to the filter carrier.  Preferably, the fibrous meshwork material is an elastic or shape memory material such that it can be collapsed into a delivery catheter and recover its enlarged shape upon deployment.  The fibres of the meshwork are bonded at the points where they cross one another.  The fibres may be made from either a polymer or metal or a composite material. 
In a further embodiment, the distal end of the filter element has the facility to move in the axial direction relative to the proximal end of the filter element so as to take up the exact shape of the blood vessel. 
In a further embodiment, the device has a porous coating on a distal end of the filter element only with means for opening and closing the filter element by slidable motion.  Preferably, the filter element comprises a collapsible wire frame having a plurality of wires, outer ends of the wires being hingedly mounted on the filter carrier, the wires being hinged intermediate their ends, at one end the wires being fixed on the filter carrier and at the other end the wires being mounted on a collar which is slidable along the filter carrier, a porous filter mesh being mounted on the wire frame.  An actuating sleeve is slidable over the filter carrier to push the collar towards the fixed end of the filter element, and a collapsing device is engagable with the collar to pull back the collar away from the fixed end of the filter element to collapse the wire frame against the filter carrier for retrieval of the filter element. 
In a still further embodiment of the invention, there is provided a filter retrieval system for use with the device comprising a longitudinal catheter with a radially deformable or elastic tip to assist the pull back of the filter into the tip. 
In another embodiment of the invention, there is provided a system incorporating a filter, a delivery catheter and a retrieval catheter for temporary filtration of the vascular system during an interventional procedure. 
In another aspect the invention provides an embolic protection device comprising:
a collapsible filter element mounted on a filter carrier for delivery through a vascular system of a patient,
the filter element being movable between a collapsed stored position against the filter carrier for movement through the vascular system, and an expanded position for occluding a blood vessel such that blood passing through the blood vessel is delivered through the filter element, a pair of spaced-apart stops on the filter carrier, the collapsible filter element being slidably mounted on the filter carrier for axial movement along the filter carrier between the stops, and means for collapsing the filter element on the filter carrier.