METHODS AND APPARATUS FOR TREATING NEUROVASCULAR VENOUS OUTFLOW OBSTRUCTION
Methods and devices are disclosed for treating neurovascular venous outflow obstructions, with or without implantation of a prosthetic valve. The valve may be carried by a support, such as a stent, which may be self-expandable or balloon expandable. Both transvascular and direct surgical access is contemplated.
This application claims the benefit of U.S. Provisional Application No. 61/400,383, filed Jul. 27, 2010, the entirety of this application is hereby incorporated by reference herein.BACKGROUND OF THE INVENTION
The present invention relates to methods and devices for treating neurovascular venous outflow obstructions, such as to relieve the symptoms of multiple sclerosis or other neurological conditions.
Multiple Sclerosis (MS) is a debilitating disease for which modern medicine has few answers. Questions remain regarding the etiology, the disease process, and possible treatments. Since Jean Martin Charcot first described the clinical and pathological features of MS in 1868 it has perplexed physicians and scientists alike. For years the disease was described clinically, but with the advent of more sophisticated tools such as magnetic resonance imaging (MRI), the disease process was linked to plaques—or inflammatory lesions—in the white matter of the central nervous system. These lesions were characterized by a breakdown of the myelin sheath that surrounds the central axon of a nerve cell. The first clinical signs are thought to manifest years after the pathology begins in the brain. There is also increasing evidence that the pathology is much more widespread than the finite number of lesions seen on MRI. In addition, serial MRI studies have shown that the disease process is ongoing even when clinical symptoms seem to have subsided.
The pathophysiology of the disease process has been described and is believed to involve an autoimmune component; however, the precise underlying etiology remains a mystery. MS has been associated with past Epstein Barr Virus (EBV) exposure, smoking, geography, and it is believed to have some genetic component. MS affects more than 350,000 people in the United States. Estimates of the prevalence of the disease are approximately 90 cases per 100,000 people.
The symptoms of an MS attack or flare can include: paresthesias, limb weakness, paralysis, double vision, loss of vision, incontinence, and cognitive decline. There are three main clinical courses of MS: Relapsing Remitting (RR); Secondary Progressive (SP); and Primary Progressive (PP). RR is characterized by acute exacerbations of the disease followed by complete remission of the symptoms with nearly complete recovery. Some patients with the RR course of the disease will not completely return to their baseline level of function. SP is characterized by progressive deterioration of neurologic function. Most patients with the RR course of the disease will eventually develop SP after several years with RR. PP is characterized by a progressive clinical course from the onset of the disease.
In terms of the pathophysiology, MS involves the breakdown of the myelin sheath that surrounds the central axon of a nerve. There also appears to be widespread axonal damage. In addition, though the disease had often been considered a white matter disease, there is now some evidence of pathology in the grey matter of the brain as well. Though the genetic aspect of MS has been studied there has been no direct genetic link identified. Despite the complicated set of immunological changes that affect the myelin and axons having been studied extensively for years. In addition, there is epidemiological evidence that points to some variable incidence of MS in different parts of the world. And yet, despite all this extensive attention and study, a cure or even an effective treatment for MS remains out of reach.
The best medicine can provide at this point for a patient is to delay the progression of the disease. And eventually even these patients will only have their symptoms managed to maximize their quality of life as the disease inevitably progresses. There is a focus in these early treatments on the few mechanisms thought to be important in the progression of the disease. Anti-inflammatory therapy has been used for acute attacks of the disease, which has no more than short-term benefit to shorten the duration of the attack. Immunosuppressive therapies have been attempted but have provided little benefit and led to substantial side effects. As understanding of the specific immunological mechanisms involved in the disease process improve there are more targeted agents being studied.
For almost four decades neurologists have been able to modify the acute attacks of the disease. Since the 1990's the agents addressing the number and severity of attacks of MS have improved, and have reduced the activity seen on MRI. However, there remains no long-term data that convincingly demonstrates a reduction in the rate of eventual progression of the disease. The various therapies used for MS have been applied by trial and error and changed as the theory of the disease changed. There is now some new evidence that venous blood flow from the brain may play a role in MS.
The venous circulatory system flowing from the brain is complicated. Blood is drained from the brain by back propulsion of the residual arterial pressure (i.e., negative venous pressure), and antegrade postural and respiratory mechanisms. The internal jugular vein (IJV) collects the blood from the brain, face, and neck. The IJV is directly continuous with the sigmoid sinus in the jugular foramen at the base of the skull. At the origin of the IJV, the vein is somewhat dilated—this dilatation is called the superior bulb. It runs down the side of the neck in a vertical direction, lying at first lateral to the internal carotid artery, and then lateral to the common carotid. At the root of the neck the IJV unites with the subclavian vein (SV) to form the innominate vein. A little above its termination is a second dilatation called the inferior bulb. At the root of the neck, the right IJV is farther from the common carotid, and crosses the first part of the subclavian artery, while the left IJV usually overlaps the common carotid artery. The left IJV is generally smaller than the right, and each contains a pair of valves, which are about 2.5 cm above the termination of the vessel. The external jugular (EJV) vein receives the greater part of the blood from the exterior of the cranium and the deep parts of the face, being formed by the junction of the posterior division of the retromandibular vein with the posterior vein. The EJV has two pairs of valves, the lower pair is at the intersection with the SV, and the upper in most people is about 4 cm above the clavicle. The portion between the two valves is often dilated and is called the sinus. These valves do not prevent the regurgitation of blood or the passage of blood from below upward. Supine posture favors cerebral venous outflow through the IJV veins. In the upright position, blood is redirected through the vertebral veins and the azygous vein (AZ) which becomes the predominant pathway.
There are valves in the IJV in more than 90% of patients. These valves are frequently located in the distal portion of the IJV. Sonography demonstrates bilateral valves in 60% of patients, with the majority of unilateral valves are right sided. Doppler ultrasound (US) of the IJV has demonstrated symmetrical biphasic blood flow in 57% of 148 patients, continuous flow in 29%, and monophasic flow in 13%. Scientists have hypothesized blood flow velocity normal when it is less than 1 m/s and varies with both respiration and heart rate. Others have reported an average right-plus-left jugular vein flow of 740±209 ml/min. Flow was 8.7% lower in female than in male subjects, but normalization of flow to 100 g brain tissue failed to reveal any significant sex difference. Normal Doppler US waveforms are characterized by two physiological variations: 1) cardiac pulsatility, due to the retrograde pressure waves of right atrial contraction, is synchronized to the pulse rate and frequently results in a biphasic signal; 2) superimposed variations related to the respiratory cycle, with an increase on inspiration and a decrease on expiration.
IJV valve incompetence has been documented for many years, and is hypothesized to be associated with various disease process including respiratory brain syndrome and cough headaches. The IJV valve is situated just above the termination of the IJV and is the only valve between the heart and the brain. If the IJV valve is damaged or becomes incompetent, increase in intrapleural pressure could result in raised intracranial pressure. Additionally, the jugular venous pulse is used clinically to estimate right atrial pressure. A high prevalence of IJV valve insufficiency appears to be present in patients with clinical diagnosis of transient global amnesia (TGA)—suggesting that venous congestion in areas of the brain associated with memory may partially explain episodes of benign TGA. IJV valve insufficiency has been found to be present in at least 1 side in almost 80% of patients with TGA, compared with only 25% of control subjects. There was also a trend toward a predominance of right-sided IJV valve insufficiency. Studies have shown valvular insufficiency in nearly 80% of subjects with TGA compared to 25% of subjects with no history of TGA.
Ever since Jean Martin Charcot first described MS, the plaques were known to be venocentric. Since then magnetic resonance venographs (MRVs) and postmortem studies have shown a central vein oriented along the long axis of the inflammatory lesion. In addition, the brains and spinal cords of patients with MS contain abnormally high levels of redoxactive metals, particularly iron, as documented by advanced MRI studies. Histologic studies have shown disposition of iron stores in CNS venous walls in patients with MS. In the 80's it was hypothesized that MS might be related to cardiorespiratory blood “backjets” as the basis for the Dawson's Fingers, which are lesions seen around the CNS veins near the ventricle in MS patients.
A condition called Chronic Cerebrospinal Venous Insufficiency (CCSVI) has been hypothesized to be associated with MS. Researchers have described CCSVI as a condition with multiple stenoses of the principal pathways of the extracranial venous drainage, such as the IJV and Azygous vein (AV). A study from 2009 looking at 65 MS patients (35 with RR; 20 with SP; and 10 with PP) and 265 controls (60 healthy—age and gender matched; 82 healthy but older than study group; 45 with other neurological disease; 48 with other disease scheduled for venography) examined the flow in the azygous and jugular venous system. Zamboni et al., Chronic Cerebrospinal Venous Insufficiency in Patients with Multiple Sclerosis, 80 J. N
Notwithstanding the foregoing, there remains a need for methods and devices for treating neurovascular venous outflow obstructions, such as to relieve the symptoms of Multiple Sclerosis or other neurological conditions or disease.SUMMARY OF THE INVENTION
There is provided in accordance with the present invention methods and devices for treating cerebrospinal venous insufficiency, which treatment may reduce or eliminate certain symptoms of multiple sclerosis or other neurological conditions. In accordance with the methods of the present invention, a patient is identified having at least a partial obstruction at a site in the venous outflow track from the brain. Patency is restored by at least partially removing the obstruction, and a valve is implanted in fluid communication with the site, to permit venous outflow and reduce retrograde pressure. The valve may be implanted at the site, or in upstream or downstream fluid communication with the site.
The removing the obstruction step may comprise inflating a dilatation balloon at the site. The dilatation balloon may additionally carry an implant at the time of the inflating step to remove the obstruction. Alternatively, following removal of the obstruction, a deployment balloon may be positioned at the site carrying an implant for balloon deployment. The deployment balloon may be carried by a catheter, which is introduced into the vasculature at an access point spaced apart from the site.
The removing the obstruction step may comprise surgically removing a section of vein. The implanting step may comprise surgically attaching a valve, or a graft containing a valve, at the site.
The method may comprise attaching a first end of a graft at a first anastomosis to a vein and attaching a second end of the graft at a second anastomosis to a vein. The first anastomosis may be to the right internal jugular, the left internal jugular or the azygos vein. The second anastomosis may be to the right internal jugular, the left internal jugular, the right innominate, the left innominate the azygos or the superior vena cava.
Alternatively, a valve may be implanted in one or more of the left internal jugular, the right internal jugular, the azygos and the superior vena cava.
Further features and advantages of the present invention will become apparent to those of skill in the art in view of the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims.
Venous flow through the left internal jugular 20 and external jugular 22 merge with the subclavian vein 24, and lead via the left innominate 26 to the superior vena cava 16.
The extracranial venous vasculature described above is typically also characterized by the presence of a number of valves. Although patient-to-patient variation is observed, a typical patient may have a first valve 28 and a second valve 30 within the right internal jugular 10. The left internal jugular 20 may also be provided with a first valve 32 and a second valve 34. In addition, the azygos vein 18 is often found with at least one valve 36.
In a healthy patient, the valves function to permit outflow from the cerebral vasculature, while inhibiting retrograde flow and/or pressure throughout the cardiac cycle.
Anomalies in the venous outflow track from the brain have been associated with a variety of neurological conditions. For example, malformed or deformed valves can lead to regurgitant flow. Venous stenosis, which may result from either the formation of thrombus or plaque, or from extreme twisting or bending of the vein, can produce resistance to normal venous drainage. Stenotic legions in the venous vasculature are often observed in the vicinity of or involving one or more valves, or may be spaced apart from the valves.
In accordance with the present invention, one or more therapeutic procedures which may involve an implant are accomplished on the extracranial venous vasculature, to alleviate an abnormality in venous blood flow. As is discussed in greater detail below, the procedure may be accomplished either via a direct surgical incision, or transvascularly using one or more catheters introduced into the venous system at a remote site. The procedure may involve restoring patency to the venous lumen, such as by balloon dilatation or other recanalization technique. The procedure may additionally involve deployment of a permanent or temporary implant, such as a tubular scaffold to inhibit restenosis of the venous lumen. One or more valves may also be deployed, and oriented to permit venous outflow but resist regurgitant pressure and/or flow. Various aspects of the invention will be described in additional detail below.
The catheter 40 generally comprises an elongate tubular body 42 extending between a proximal end 44 and a distal functional end 46. The length of the tubular body 42 depends upon the desired application. For example, lengths in the area of from about 120 cm to about 140 cm or more are typical to reach the jugular veins via femoral access. A different catheter shaft length may be appropriate depending upon the vascular access site, as will be understood in the art.
The proximal end 44 of catheter 40 is additionally provided with a handle 48 having one or more access ports as is known in the art. Generally, handle 48 is provided with a guidewire, port 50 in an over-the-wire construction, and optionally an aspiration or infusion port (not illustrated). The guidewire port 50 may comprise a standard luer connector, and is in communication with a distal guidewire access port 52 by way of an elongate guidewire lumen 54. Alternatively, aspiration or infusion may be accomplished through the guidewire lumen in an OTW configuration if the guidewire is proximally retracted following placement of the catheter 40.
A rapid exchange configuration may be provided, by eliminating the proximal luer connector at the proximal guidewire port 50, and positioning the proximal guidewire port 50 along the side wall of the tubular body 42. Generally, the proximal guidewire access port 50 in a rapid exchange configuration will be positional within about 20 cm, and, in some embodiments, within about 10 cm from the distal guidewire port 52 as is understood in the art. Additional access ports may be provided as needed, depending upon the desired functional capabilities of the catheter. Handle 48 may be injection molded from any of a variety of medical grade plastics, or formed in accordance with other techniques known in the art.
The cross-sectional view of
Referring back to
Any of a variety of controls 70 may be utilized, including switches, levers, rotatable knobs, pull/push wires, and others which will be apparent to those of skill in the art in view of the disclosure herein.
Avoiding a tight fit between the guidewire 68 and inside diameter of guidewire lumen 54 enhances the slideability of the catheter over the guidewire. In ultra small diameter catheter designs, it may be desirable to coat the outside surface of the guidewire 68 and/or the inside surface of the wall defining lumen 54 with a lubricous coating to minimize friction as the catheter 40 is axially moved with respect to the guidewire 68. A variety of coatings may be utilized, such as Paralene, Teflon, silicone rubber, polyimide-polytetrafluoroethylene composite materials or others known in the art and suitable depending upon the material of the guidewire or inner tubular wall of lumen 54.
In general, the inside diameter of guidewire lumen 54 will be at least about 0.003 inches or greater larger than the outside diameter of the intended guidewire. Guidewires having diameters in the range of from about 0.009 inches to about 0.016 inches are presently contemplated.
Catheters of the present invention which are adapted for intracranial applications generally have a total length in the range of from 60 cm to 250 cm, usually from about 135 cm to about 175 cm. The length of the proximal segment 33 will typically be from 20 cm to 220 cm, more typically from 100 cm to about 120 cm.
The catheters of the present invention may be constructed from any of a variety of known biologically compatible polymeric resins having suitable characteristics when formed typically by extrusion into the tubular catheter body segments. Exemplary materials include a variety of medical grade polyvinyl chloride, polyethers, polyamides, polyethylenes, polyurethanes, copolymers thereof, and the like. Suitable species include PEBAX, PEEK, and others known in the angioplasty arts. In certain embodiments, the distal tip 64 may be fanned from more elastic materials, such as latex rubber, silicone rubber, and blends thereof.
The catheter body 42 may further comprise other components, such as radiopaque fillers; colorants; reinforcing materials; reinforcement layers, such as braids and helical reinforcement elements; or the like. In particular, a proximal zone on body 42 may be reinforced in order to enhance its column strength and torqueability while preferably limiting its wall thickness and outside diameter.
Radiopaque markers may be provided at least at the proximal and/or distal ends of the annular recess 62. The implant may comprise a radiopaque material or be provided with markers. Other radiopaque markers may be provided elsewhere, such as on the distal end of the movable sleeve 56. One radiopaque marker comprises a metal band which is embedded within the wall of the sleeve 56 or core 58. Suitable marker bands can be produced from a variety of materials, including platinum, gold, and tungsten/rhenium alloy.
The tubular body 42 may be produced in accordance with any of a variety of known techniques for manufacturing interventional catheter bodies, such as by extrusion of appropriate biocompatible polymeric materials. Alternatively, at least a proximal portion or all of the length of tubular body 16 may comprise a polymeric or metal spring coil, solid walled hypodermic needle tubing, or braided reinforced wall, as is known in the microcatheter arts.
In many applications, the tubular body 42 is provided with an approximately circular cross-sectional configuration having an external diameter within the range of from about 0.025 inches to about 0.065 inches. Alternatively, a generally oval or triangular cross-sectional configuration can also be used, as well as other noncircular configurations, depending upon the method of manufacture, number and arrangement of internal lumens and the intended use.
In a catheter intended for peripheral vascular applications, the body 42 may have an outside diameter within the range of from about 0.039 inches to about 0.065 inches. In coronary vascular applications, the body 42 may have an outside diameter within the range of from about 0.025 inches to about 0.045 inches. Catheters configured to access the external jugular vein 22 will typically have an outside diameter of no more than about 0.045 inches, and as low as about 0.028 inches or about 0.025 inches or about 0.022 inches or lower.
Diameters outside of the preferred ranges may also be used, provided that the functional consequences of the diameter are acceptable for the intended purpose of the catheter. For example, the lower limit of the diameter for any portion of tubular body 42 in a given application will be a function of the number of fluid or other functional lumen contained in the catheter, together with the collapsed diameter of the implant.
Tubular body 42 must have sufficient structural integrity (e.g., column strength or “pushability”) to permit the catheter to be advanced to distal locations without buckling or undesirable bending of the tubular body. The ability of the body 16 to transmit torque may also be desirable, such as to avoid kinking upon rotation, to assist in steering. The tubular body 42, may be provided with any of a variety of torque and/or column strength enhancing structures. For example, axially extending stiffening wires, spiral wrapped support layers, braided or woven reinforcement filaments may be built into or layered on the tubular body 16. See, for example, U.S. Pat. No. 5,891,114 to Chien, et al., the disclosure of which is incorporated in its entirety herein by reference.
Alternatively, any of a variety of the implants disclosed herein can be configured for deployment from a balloon catheter. In a most basic embodiment, a balloon expandable stent is provided with a valve and carried in a collapsed configuration over a deflated balloon to the deployment site. The balloon is inflated at the deployment site to expand the stent, leaving the stent and valve construct at the deployment site following deflation and proximal retraction of the balloon catheter. Many of the dimensions and considerations previously discussed in connection with self-expandable implant deployment systems will also guide the design of suitable balloon catheter deployment systems. Balloon catheters intended for deployment of an implant in the azygos vein may have an inflated balloon diameter within the range of about 6 mm to about 8 mm, and an inflated diameter within the range of about 8 mm to 16 mm for balloons intended to deploy an implant in the jugular vein.
Certain stenoses in the extracranial venous vasculature require a relatively high inflation pressure in order to recanalize the lumen. Inflation pressures of at least about 18 atmospheres or 20 atmospheres or more are often desirable. As a consequence, deployment of a self-expanding implant preferably will be preceded by a balloon dilatation. The valves associated with balloon expandable implants, particularly if a tissue valve is utilized, may or may not tolerate the compression resulting from high inflation pressures. Thus, depending upon the valve design, either a pre-implantation balloon dilatation may be preferred, or the dilatation can be accomplished simultaneously with expansion of the implant at the deployment site.
Resistant stenoses may alternatively be dilated using a cutting balloon. Cutting balloons are known in the percutaneous transluminal coronary angioplasty arts, and include one or more axially elongate incising elements mounted on the exterior of the inflatable balloon. One example of a cutting balloon may be seen in U.S. Pat. No. 7,799,043 to O'Brien et al. (Boston Scientific) the disclosure of which is hereby incorporated in its entirety herein by reference.
As a further alternative, the implant may be a two or more part construct which is assembled in situ at the deployment site. For example, a support structure such as a stent can be carried by a balloon to the deployment site, and expanded under high pressure to generate sufficient radial force to dilate both the stent and the lesion utilizing a first procedure catheter. A second procedure catheter may thereafter be introduced and positioned within the support structure, to deploy the valve. The valve deployment may either be accomplished by a balloon catheter, which may have a lower inflation pressure than the first procedure catheter, or in a self-expanding mode. The valve is coupled to the support structure, to produce the final construct.
Certain exemplary valve and support structure constructs will be described below. The present invention contemplates the use of any of the valve structures described below with any of the support structures described below, and not merely the specific examples given. In general, the implant can take any of variety of forms including a tubular scaffold without a valve, or a tubular scaffold with a valve on the same device. Alternatively, the tubular scaffold and the valve may be separately implanted and connected or associated in situ. Any of the valves disclosed herein may be alternatively be configured for anchoring to the vessel wall or within the vessel using a structure other than a tubular scaffold. As used herein, terms such as scaffold or support structure may include a form of a stent, but also include intravascular support structures which might not be considered a stent. The support structures can be balloon expandable, or self-expandable, or not expandable at all, such as in the case of certain hooks or barbs, depending upon the desired configuration.
In the illustrated embodiment, the occluder is in the form of a collapsible cone or wind sock extending from an apex 80 at an upstream end to a downstream opening 82 having a fully opened diameter at least as great as the inside diameter of the lumen. The occluder 78 is secured at apex 80 and at one or more points along its length on a first, fixation side of the occluder to the support structure 76. A second, opposing dynamic side of the implant 74 is moveable between a radially expanded (occlusive) configuration as illustrated in
As implanted in a vessel, retrograde flow 84 has a tendency to enter the open end of the occluder in a manner like a wind sock and advance the dynamic side across the lumen to occlude further retrograde flow. Referring to
Although illustrated as having only a single occluder 78, two or three or four or more inflatable and collapsible occluder elements may cooperate with each other to achieve the same functionality, in which the valve is either opened or closed in response to the direction of blood flow.
The occluder 78 may comprise any of a variety of materials, preferably in the form of a thin blood impermeable membrane. Preferably, the membrane is highly compliant and responsive to subtle changes in blood flow. The thickness of the membrane can be optimized by those of skill in the art in view of the composition of the membrane. Presently contemplated ePTFE membranes will typically have a thickness of no more than about 0.01 inches and, in some embodiments, no more than about 0.005 inches or 0.001 inches or less. Ultrathin membranes of any of a variety of polymers utilized in the catheter arts may also be used, such as nylon, polyethylene terephthalate, PEEK, various densities of polyethylene and others known in the art. Alternatively, ultrathin metal mesh membrane or porous metal membranes may be utilized, provided that they demonstrate the desired physical properties.
Preferably, the material of the membrane as well as the support structure will be antithrombogenic or at least resist thrombus formation either inherently, or through the provision of an antithrombotic coating.
In the ultrathin membrane embodiments, one or two or more axially extending struts may desirable be incorporated within or attached to the occluder 78, to improve the structural integrity of the membrane in the environment of high velocity blood flow. Depending upon the desired performance, the membrane may either be completely impermeable to blood flow, or may be provided with a level of porosity that permits a small amount of retrograde blood flow. Pore sizes of no more than about 100μ and in some embodiments no more than about 50μ or 20μ may be used.
The support structure 76 may comprise any of a variety of balloon expandable or self-expandable stents, or other support structure that is sufficient to retain the occluder 78 at the desired deployment site and resist migration under the force of blood flow. Thus, for example, the apex 80 may be secured directly to the vessel wall, using any of a variety of attachment techniques such as clips, sutures, staples, or other barb structures which extend into and optionally through the wall 70.
In the illustrated embodiment, the support structure 76 comprises at least one self-expanding tubular support in the form of a stent 86. The stent comprises a plurality of struts 88 extending in a zig-zag fashion having a plurality of alternating proximal apexes 90 and distal apexes 92, a structure some times referred to as a “Z” stent. The struts 88 may comprise any of a variety of materials having suitable properties, such as Nitinol, stainless steel, Elgiloy or others known in the art.
In the illustrated embodiment, a first tubular support 86 is spaced axially apart from a second tubular support 94 and connected by an axially extending strut 96. The axially extending strut 96 serves to both maintain the spatial relationship of the first and second tubular supports, as well as provide an attachment structure for the fixation side of the conical occluder. The occluder may be attached to the support structure at the point of manufacture, and introduced into the vessel as a single unit. Alternatively, the support structure may be deployed in a first step, and the occluder carried into position and attached to the support structure in situ in a second step.
In one implementation of the invention, the occluder 106 comprises a substantially oval shaped profile, such that it approximately conforms to the wall of the lumen when in the occlusive orientation illustrated in
Any of a variety of alternative valve construction may be utilized, depending upon the desired performance result. For example, referring to
In the illustrated embodiment, the valve 114 comprises a first leaflet 116 coaptively engaged with a second leaflet 118 to enable flow in a single direction. Single leaflet, bi-leaflet, tri-leaflet or other valves may be utilized, although bi-leaflet or tri-leaflet may be preferred. Suitable valves may be harvested from porcine, bovine, canine or other animal sources known in the art, or may be constructed such as from bovine, porcine or human tissue. The harvesting, treatment and use, for example, of pericardium is well understood in the prosthetic heart valve arts, and not disclosed in detail herein. Alternatively, autologous valves such as venous valves harvested from the peripheral vasculature of a patient may be prepared and deployed in accordance with the present invention.
The support structure for the venous valves in accordance with the present invention function to support the valve in an operative orientation within the vein, and resist migration away from the deployment site. A stent or stent like tubular structure is one convenient form of a support, and provides the basis for much of the discussion herein. However, structures which do not resemble a conventional stent may alternatively be used.
For example, referring to
A variation is illustrated in
In any of the stent or other support structure systems disclosed herein, any of a variety of features may be added to inhibit migration within the vessel. For example, referring to
The anchor system may also be customized to unique anatomical environments. For example,
Migration may also be inhibited through the use of one or more extra vascular structures, which provide an interference fit through the venous wall with a component on the valve to inhibit migration. Referring to
A radially outwardly extending element such as a projection, flange or annulus 158 is provided on the implant 160. The outside diameter of the annulus 158 plus the wall thickness of the vein 153 exceeds the inside diameter of the extra vascular cuff 156, thereby inhibiting downstream migration of the valve.
In accordance with the method of the present invention, a patient is identified having an obstruction in the venous outflow track from the brain. The obstruction may be identified using doppler ultrasound in accordance with techniques well understood in the art. The doppler ultrasound may be accomplished on patients with a clinical diagnosis of transient global amnesia, multiple sclerosis, or any of a variety of symptoms associated with multiple sclerosis, such as paresthesias, numbness, limb weakness, double vision, visual loss, complete local motor dependency, urine incontinence and cognitive decline. Doppler ultrasound may be performed on patients diagnosed with multiple sclerosis, in any of the three main clinical courses of relapsing remitting, secondary progressive, and primary progressive. Evaluation may include sonographic (extracranial echo color-doppler and transcranial color-doppler ultrasound) evaluation.
Once a stenotic lesion as been identified, percutaneous access to the venous vasculature may be achieved for example at the femoral vein, and a balloon dilatation catheter may be advanced over or along a guidewire to position the balloon within the lesion. The lesion is thereafter dilated, the balloon deflated and removed in accordance with techniques well understood in the art.
In certain implementations of the invention, dilation is accompanied by placement of an intravascular stent, without implantation of a valve.
In an alternative implementation of the invention, the dilation is followed by placement of a valve, carried by a support structure such as a stent. In general, stenotic lesions which are spaced apart from the native valves, may be dilated and supported with an intravascular stent in the absence of implantation of a valve. However, lesions involving a valve, or other valvular dysfunction may suggest the desirability of implantation of one or more valves of the type disclosed previously herein.
In one example, one or two valves in the left internal jugular have become undesirably resistive to forward blood flow. The valve is accessed via conventional techniques, and a valvuloplasty is accomplished by dilation of a balloon or other expansion structure within the valve to restore patency to the lumen. The valvuloplasty catheter may comprise a bare balloon, or a balloon which carries an intravascular support such as a stent. A valve may be associated with the intravascular support.
Alternatively, the valvuloplasty balloon may be utilized to deploy a stent or other support structure in the vicinity of the dilated valve simultaneously with valve dilatation. The valvuloplasty balloon catheter is removed from the patient, and a valve deployment catheter is thereafter positioned within the deployed support. A valve carried by the valve deployment catheter is coupled to the support, and the valve delivery catheter is proximally retracted from the patient leaving the valve coupled to the support at the treatment site.
It is believed that the implanted valve need not necessarily reside at the same location as the native valve. Thus, a valve and valve support structure may be deployed within the vasculature, spaced apart from the dilated valve. Balloon dilatation of valves in the right internal jugular, for example, may therefore be followed by placement of a valve in either the right internal jugular or the right innominate vein. Similarly, balloon dilation of one or more valves in the left internal jugular may be followed by implantation of one or more valves in the left internal jugular or the left innominate vein. As a further alternative, balloon dilation, with or without stenting, of any of a variety of valves in the venous outflow track from the brain may be followed by positioning of a valve in the superior vena cava. For example, referring to
In addition to any of the foregoing, it may be desirable to implant a filter in the flow path between the treatment site and the heart, if a risk of embolization to the heart is a concern. Thus, referring to
Either as an alternative to or in addition to any of the foregoing percutaneous or minimally invasive procedures, methods and devices in accordance with the present invention can also be optimized for surgical intervention. Thus, referring to
The extravascular valved venous graft 200 comprises an elongate flexible tubular body 208 extending between a superior end 210 and an inferior end 212. Superior end 210 is provided with an end to side anastomosis 214 to the left internal jugular vein, utilizing sutures 216 or other clips or attachment techniques known in the art. Inferior end 212 of tubular body 208 is connected via anastomosis 218 at the inferior opening 204 to the left innominate vein 26. Tubular body 208 thus provides a bypass conduit for cerebral venous drainage, avoiding the obstruction 206.
Tubular body 208 may be provided with at least a first valve 220, and, optionally, at least a second valve 222. Any of a variety of valves structures such as those disclosed elsewhere herein may be utilized. Tubular body 208 may comprise any of a variety of materials suitable for use in vascular grafts, such as ePTFE, Dacron, or other fabric or extrudable polymers. The tubular body 208 may be supported along at least a portion or the entire length thereof to maintain patency of the graft 200. Any of a variety of support structures may be utilized, such as an end-to-end construct of Z stent structures as has been disclosed elsewhere herein. Alternatively, since the endovascular valved venous graft 200 is intended for surgical implantation, the ability to collapse and expand may not be necessary. Thus, any of a variety of reinforcing structures such as a plurality of axially spaced apart annular rings or hoops, or a helical wire or polymeric filament support may be attached to the interior surface or the exterior surface of the graft 200, or entrapped between an inner tubular layer and an outer tubular layer. Techniques for surgical implantation and anastomosis of bypass grafts are well understood in the coronary and peripheral vasculature, and will not be detailed further herein.
As an alternative to extravascular bypass as illustrated in
As an alternative to the prosthetic grafts described above, native tissue (typically autologous) can be harvested, prepared and implanted in accordance with the methods of the present invention. Thus, either of the valved grafts 200 (of
Hybrid procedures may also be utilized, such as balloon valvuloplasty of a valve in the venous outflow track from the brain, followed by surgical access to implant a prosthetic valve. Any of a variety of valve configurations may be utilized for surgical implantation, as will be appreciated by those of skill in the art. For example, a valve adapted for surgical implantation is illustrated in
Alternatively, in a prosthetic valve such as one in which the leaflets comprise a polymeric membrane or tissue such as pericardium, the annulus 120 may comprise a biocompatible metal or polymer. In this instance, a fabric coating 121 such as a Dacron or ePTFE sleeve may be provided over the annulus 120, to form a sewing ring such that sutures can be stitched through the fabric 121 into adjacent venous tissue.
Alternatively, the valve 114 may be supported within a length of tubular graft 250, as schematically illustrated in
In accordance with a further aspect of the present invention, there is provided a formed in situ valve. Formed in situ valves may be constructed either translumenally, surgically or a combination of both.
Vessel segment 260 defines a central flow lumen 261 which permits blood flow in a downstream flow direction 263. Flow thus extends from an upstream side 262 to a downstream side 264 of the valve.
The valve is formed by creating an incision 266 having a generally U shape, such that a first end 267 and second end 269 of incision 266 are oriented in a relative upstream direction, and a free end 272 is oriented in a downstream direction. Incision 266 thus creates a flap 268 which remains connected to the vessel 260 via a hinge 270. This construction enables the flap 268 to pivot about the vicinity of the hinge 270 and close the central lumen 261 as illustrated in
Due to the thin nature of the venous wall, a flap 268 in the presence of reverse direction blood flow may well be carried in an upstream direction beyond the hinge 270 and not provide any valving function. Thus, a backstop 274 which comprises a limit surface such as a plurality of spaced apart struts 276 may be positioned within the vessel, to limit upstream movement of the flap 268 beyond a closed orientation. Backstop 274 may be integrally formed with or attached to a support 278 which may comprise any of a variety of balloon expandable stents, self-expandable stents or other attachment structures such as those disclosed elsewhere herein. Backstop 274 may be introduced into the vessel either via the incision 266 in a surgical procedure, or translumenally via a remote vascular access site. As illustrated in
Since the flap 268 functions as the occluder in the formed in situ valve 258, when the flap 268 is in the “closed” orientation as in
Any of the valves or valve supports deployed in accordance with the present invention may be coated with or otherwise carry a drug to be eluted over time at the deployment site. Any of a variety of therapeutically useful agents may be used, including but not limited to, for example, agents for inhibiting restenosis, inhibiting platelet aggregation, or encouraging endothelialization. Some of the suitable agents may include smooth muscle cell proliferation inhibitors such as rapamycin, angiopeptin, and monoclonal antibodies capable of blocking smooth muscle cell proliferation; anti-inflammatory agents such as dexamethasone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, acetyl salicylic acid, and mesalamine, lipoxygenase inhibitors; calcium entry blockers such as verapamil, diltiazem and nifedipine; antineoplastic/antiproliferative/anti-mitotic agents such as paclitaxel, 5-fluorouracil, methotrexate, doxorubicin, daunorubicin, cyclosporine, cisplatin, vinblastine, vincristine, colchicine, epothilones, endostatin, angiostatin, Squalamine, and thymidine kinase inhibitors; L-arginine; antimicrobials such astriclosan, cephalosporins, aminoglycosides, and nitorfuirantoin; anesthetic agents such as lidocaine, bupivacaine, and ropivacaine; nitric oxide (NO) donors such as lisidomine, molsidomine, NO-protein adducts, NO-polysaccharide adducts, polymeric or oligomeric NO adducts or chemical complexes; anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone, an RGD peptide-containing compound, heparin, antithrombin compounds, platelet receptor antagonists, anti-thrombin antibodies, anti-platelet receptor antibodies, enoxaparin, hirudin, Warafin sodium, Dicumarol, aspirin, prostaglandin inhibitors, platelet inhibitors and tick antiplatelet factors; interleukins, interferons, and free radical scavengers; vascular cell growth promoters such as growth factors, growth factor receptor antagonists, transcriptional activators, and translational promotors; vascular cell growth inhibitors such as growth factor inhibitors (e.g., PDGF inhibitor—Trapidil), growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, bifunctional molecules consisting of a growth factor and a cytotoxin, bifunctional molecules consisting of an antibody and a cytotoxin; Tyrosine kinase inhibitors, chymase inhibitors, e.g., Tranilast, ACE inhibitors, e.g., Enalapril, MMP inhibitors, (e.g., Ilomastat, Metastat), GP IIb/IIIa inhibitors (e.g., Intergrilin, abciximab), seratonin antagnonist, and 5-HT uptake inhibitors; cholesterol-lowering agents; vasodilating agents; and agents which interfere with endogeneus vascoactive mechanisms. Polynucleotide sequences may also function as anti-restenosis agents, such as p15, p16, p18, p19, p21, p27, p53, p57, Rb, nFkB and E2F decoys, thymidine kinase (“TK”) and combinations thereof and other agents useful for interfering with cell proliferation. The selection of an active agent can be made taking into account the desired clinical result and the nature of a particular patient's condition and contraindications. With or without the inclusion of a drug, certain of the valve supports disclosed herein can be made from a bioabsorbable material. Various polymeric carriers, binding systems or other coatings to permit controlled release of active agent from the valve or support or its coating are well known in the coronary stent arts and not reproduced herein.
Additional treatment systems and methods of use for application in patients suffering from Multiple Sclerosis caused by insufficient venous capacity are described below. This treatment is particularly challenging due to the large size and compliance of veins and the resulting in the potential stent migration. Furthermore, some lesions within the venous vasculature can be very fibrotic and difficult to open with standard PTA balloons. More aggressive dilatation devices such as the cutting balloon from Boston Scientific, Inc. may have application with the fibrotic lesion, but are potentially dangerous to adjacent areas of healthy vessel.
With the compliant balloons inflated and optimally positioned, the semi-compliant or non-compliant balloon is inflated to dilate the stenosis. See
Once the lesion has been expanded with the balloon device described in
Although certain preferred embodiments and examples have been described herein, it will be understood by those skilled in the art that both the devices and methods of the present invention extend beyond the specifically disclosed examples to other alternative embodiments and/or uses of the invention and modifications and equivalents thereof. Thus, it is intended that the scope of the present inventive subject matter herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined by reference to the following claims.
1. A method of treating cerebrospinal venous insufficiency, comprising the steps of:
- identifying a patient having at least a partial obstruction at a site in the venous outflow track from the brain;
- removing the obstruction; and
- implanting a valve in fluid communication with the site, to permit venous outflow and reduce retrograde pressure.
2. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the removing step comprises inflating a balloon at the site.
3. A method of treating cerebrospinal venous insufficiency as in claim 2, wherein the balloon carries an implant at the time of the inflating step.
4. A method of treating cerebrospinal venous insufficiency as in claim 2, further comprising removing the balloon and thereafter performing the implanting a valve step.
5. A method of treating cerebrospinal venous insufficiency as in claim 2, wherein the balloon is carried by a catheter introduced into the vasculature at an access point spaced apart from the site.
6. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the removing step comprises surgically removing a section of vein.
7. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the implanting step comprises surgically attaching a valve at the site.
8. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the implanting step comprises releasing a valve having a self expandable support at the site.
9. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the implanting step comprises inflating a balloon within a balloon expandable portion of a valve support at the site.
10. A method of treating cerebrospinal venous insufficiency as in claim 7, wherein the implanting step comprises implanting a tubular graft having a valve mounted therein.
11. A method of treating cerebrospinal venous insufficiency as in claim 7, wherein the implanting step comprises attaching a first end of the graft at a first anastomosis to the left internal jugular vein and attaching a second end of the graft at a second anastomosis to the left innominate vein.
12. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the valve is implanted in the left internal jugular vein.
13. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the valve is implanted in the right internal jugular vein.
14. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the valve is implanted in the azygos vein.
15. A method of treating cerebrospinal venous insufficiency as in claim 1, wherein the valve is implanted in the superior vena cava.
16. A method of treating cerebrospinal venous insufficiency as in claim 10, wherein the graft comprises a tubular ePTFE wall.
17. A method of treating cerebrospinal venous insufficiency as in claim 10, wherein the graft comprises a section of saphenous vein.
18. A cerebrospinal venous insufficiency catheter, comprising:
- a first elongate, tubular shaft, having an inflation lumen extending therethrough;
- a first balloon carried by the shaft;
- a second elongate, tubular shaft, having a central lumen, and axially movably carried by the first shaft, the central lumen having a distal opening;
- wherein the distal opening is axially movably positionable between a first position in which the first balloon is at least partially within the central lumen, and a second position in which the first balloon is fully exposed beyond the distal opening.
19. A cerebrospinal venous insufficiency catheter as in claim 18, further comprising a second balloon carried by the first shaft.
20. A cerebrospinal venous insufficiency catheter as in claim 18, further comprising a third balloon carried by the second shaft.
21. An implant, for positioning in the neurovascular venous outflow tract, comprising:
- a radially expandable frame, for engaging the wall of a vein; the frame having a flowpath therethrough;
- an occluder support within the frame, extending across the flow path at an inclined angle relative to the central axis of blood flow; and
- a thin film occluder, movable between a first position spaced apart from the occluder support sufficient to permit flow through the flow path in a first direction, and a second position in contact with the support such that it inhibits flow through the flow path in a second direction.
22. An implant as in claim 21, further comprising at least one anchor on the frame for engaging the wall of the vein.
International Classification: A61F 2/06 (20060101); A61F 2/84 (20060101);