Intravascular occlusion removal device

Abstract: An embolism treatment device comprising: (a) a core wire element having a distal end and a proximal end and a longitudinal axis, (b) a cage assembly comprising at least one spirally wound metallic member having a distal end and a proximal end, wherein said cage assembly is generally coaxial to said core wire element and wherein said distal end of said cage assembly is fixedly attached to said core wire element, (c) an actuator fixedly attached to said proximal end of said spirally wound metallic member, and (d) a radioopaque tip fixedly attached to said core wire element distally of said cage assembly, wherein said cage assembly has a first deployment shape when said actuator is in a first deployment position and a second larger expanded shape different from the first deployment shape when said actuator is in a second deployment position.

Description: FIELD OF THE INVENTION This is a medical device. In particular, it is a surgical device usually delivered through an intravascular catheter. It may be used in several ways. It may, for instance, be used to open a clear passageway adjacent thrombus to allow both blood and medication to bypass the clot. It may be used to pierce and to remove thrombus. These thrombus are often found in tortuous vasculature. The device includes several sections. The device has a core element, typically a core wire. Placed around the distal end of the core element is a collapsible but preferably self expanding cage assembly. The cage assembly is preferably radio-opaque. The proximal end of the cage is typically affixed to an actuator in such a way as to allow expansion of the cage after deployment. The cage assembly has a generally conical distal or "trailing" portion when expanded and also a proximal section. The cage assembly can be used for collecting emboli or for displacing them to allow blood flow to resume, either with or without concurrent clot-dissolving drug treatment. The proximal section may have various uses, e.g., for centering the collector assembly in the vascular lumen or for gathering larger amounts of the targeted clot or to act as a passageway for fluid flow. The assembly further has an actuator which permits or causes the collector assembly to expand after deployment. BACKGROUND OF THE INVENTION This surgical device is designed to displace or to penetrate emboli found in the human vasculature. Depending upon the chosen procedure, it is inserted into the region either towards the venous side of the clot or adjacent the clot. The cage is expanded either to displace the clot from the arterial wall and allow flow of fluid (i.e., blood and medications such as anti-thrombolytics or other lysing agents) past (or to) the formerly occluded site or to engage the clot for removal using the cage as a collector assembly, expand once past the target emboli, and catch or net the embolism (or a portion of the embolism) for removal from patient's blood vessels. In some situations, the device may be used to move the clot to another position in the vasculature; perhaps for recovery using another device or to canalize the clot for improved blood flow. The use of inflatable balloons to remove emboli has been practiced for many years. The "Fogarty catheter" has been used, typically in the periphery, to remove clots from arteries found in legs and in arms. These well known devices have been described in some detail in U.S. Patent No. 3,435,826, to Fogarty and in U.S. Patent Nos. 4,403,612 and 3,367,101. These patents describe a balloon catheter in which a balloon material is longitudinally stretched when deflated. Emboli occasionally form around the valves of the heart and then are dislodged and follow the blood flow into the distal regions of the body. They are particularly dangerous if the emboli passes to the brain and causes an embolic stroke. As will be discussed below, many such occlusions occur in the middle cerebral artery (MCA), although such is not the only site where emboli come to rest. Obviously, when blood flow is inhibited or cut off completely from a portion of the brain, the brain's oxygen supply is limited causing severe problems. In procedures for removing emboli using the Fogarty catheter or other similar catheters, it is typical, first, to locate the clot using fluoroscopy. The embolectomy catheter is then inserted and directed to the clot. The distal tip of the balloon catheter is then carefully moved through the center of the clot. Once the balloon has passed through the distal side of the clot, the balloon is inflated. The balloon catheter is then gradually and gently withdrawn. The balloon, in this way, acts to pull the clot ahead of the balloon. The majority of procedures using a Fogarty catheter repeat these steps until the pertinent vessel is cleared of clot material. Such vaso-occlusions occur in a wide variety of sites within the body. The lodging of thrombus in various sites is complicated by the presence of atherosclerosis. This disease causes the vessels to become tortuous and narrowed. These anomalies are often considered to be the result of the growth of atherosclerotic plaque. Clots occurring in these diseased vessels are difficult to remove using balloon or Fogarty catheters. Removal of emboli using balloon catheters is rife with potential problems. One such problem occurs during removal of a clot. The resistance to such removal often causes the balloon portion of the catheter to evert over the tip of the catheter. Should the user need to partially deflate the balloon during such a deflation, the distal tip of the balloon may become distended and angulate. Another difficulty with balloon catheters is the possibility of damage to the intima of arteries. Inflation pressures can create forces significant enough to shear such a vessel lining or dislodge plaque lodged on such a wall. In the worst case, the balloon may rupture leaving balloon portions in the bloodstream. Movement of a balloon in the MCA using only a balloon can displace the clot through more proximal branches into other large vessels such as the internal carotid artery (ICA) and then into other vessels. There are a variety of different devices intended for use in replacing balloon catheters and in using a device other than a balloon catheter in so removing the emboli. One such device is shown in U.S. Patent No. 4,030,503 to Clark III. This patent describes a spiral helix affixed to the distal end of a catheter. In particular, the spiral helix is designed to be rotated and pushed forward through the clot. It is said that the helix screws into the clot, and when it is firmly embedded or is past the clot, the catheter is pulled out of the vessel without rotation. The catheter is said to operate like a corkscrew. A similar catheter is described in U.S. Patent No. 4,706,671 to Weinrib. This catheter also has a coil section at its distal end. The coil section is said to be stretched initially into a generally linear insertion position for removing inwardly in a vessel. The coil member is then expanded into the form of a hollow conical scoop to then scoop clot material from the blood vessel. The coil member is stiffened by an internal wire which is then removed. The hollow passageway is then filled with a liquid to stiffen the coils. The coils are said to be of an elastomeric material. U.S. No. Patent 4,762,130 to Fogarty et al., describes a helical balloon attached to the distal end of a catheter. The helical or bellowed balloon is maintained in a generally linear condition and passed into a clot. Once the catheter balloon within the clot is inflated, the balloon and adjoining clot are removed together. Another similar device used more to grip and shear atherosclerotic deposits rather than to remove thrombi is described in U.S. Patent No. 4,890,611 to Monfort et al. This device incorporates a pair of helical wires placed on the distal end of a wire. The flexible wire is pulled against a flexible catheter and the two helically configured loops expand to form a shearing apparatus. The totality of the apparatus is then twisted by means of a handle so that the pair of helically wound loops cuts through and is said to retain sections of plaque for removal from the vessel under treatment. Another thrombus extraction system is shown in U.S. Patent No. 5,011,488, to Ginsberg. In this device, an inflatable balloon having a proximal conic shape is deflated and passed through a thrombus. It is then expanded and retracted so that the proximal passage pulls the thrombus into contact with an aspirator. The aspirator then removes the clot or thrombotic material from the vessel. An alternative configuration of the expandable member is also described in the Ginsberg patent. In this variation, a wire coil is attached to an extension wire which may be moved between an extended position and a retracted position. The retracted or expanded configuration is illustrated to have a conical shape. The cone is shown to be one which has a smaller end proximally. U.S. Patent No. 5,112,347, to Taheri, shows an inflatable balloon type embolectomy catheter. The balloon has a number of fingers arranged in a leaf spring arrangement inside the balloon. The balloon is hydraulically inflated and forms a cone after inflation. The deflated device is shown in Figures 11 through 14 to be passed distally past an embolism before inflation. After inflation, the large end of the balloon collects the embolism as it is pulled past the appropriate site in the vessel. U.S. Patent No. 5,192,286, to Phan et al, shows a retrieval catheter for removing materials from various body lumens. The retrieval catheter is shown to have a slack net which may be collapsed for passage into lumen past the material to be collected. The net is unfolded after such passage and materials such as uretral stones are removed. U.S. Patent No. 5,411,509 to Hilal, shows an embolectomy catheter having an elastomeric foam tip attached distally. The foam tip has an actuator means suitable for forming the foam section both longitudinally and radially in response to activation of the actuation. In practice, the catheter tip is pressed past an embolism, inflated, and retracted with the clot being pushed proximally as retraction occurs. U.S. Patent No. 5,490,859, to Mische et al., shows an intravascular occlusion material removal device having an expandable material removal element made up of a number of wires passing between the two ends of such element, a catheter shaft, a drive shaft for spinning the material movement element within the blood vessel, and a collection portion placed on the material removal element for collecting any occlusion material removed by the expandable material removal element. The drive shaft may be operated by a motor connected to the drive shaft proximate to the proximal end of the drive shaft. None of these devices approximates the design of the device described below. SUMMARY OF THE INVENTION This is a surgical device according to claim 1 usually delivered through an intravascular catheter. It is designed variously to displace or to pierce and remove emboli particularly when found in tortuous vasculature. This embolectomy device includes several sections. First, the device has a core element. The core element preferably has at least several major functions: first, the distal portion acts as a guidewire for vessel navigation to the treatment site; second, the distal portion assists in puncturing of the clot; and third, it cooperates with the collection assembly during the deployment of that assembly. The core element may be a simple core wire (perhaps enhanced with an adherent braid) fixedly attached to the distal end of the cage assembly or a tubular member attached to the collection assembly having a removable core or guidewire in its interim. Preferably, the core element is able to rotate freely with respect to collection assembly to preserve its abilities as a guidewire while preserving the cage assembly shape and integrity. Placed distally on the core element is a collapsible (but desirably) self expanding cage assembly. That cage may be fixedly or rotatably joined to the core wire at the embolism collection assembly's distal end. The cage has a generally conical distal portion when expanded and a proximal section having varied purposes, e.g., for centering the cage assembly in the vascular lumen and providing a receptacle for entrapment of the clot. Most preferred of the designs for the cage assembly involves a super-elastic alloy ribbon or wire braid. The assembly further has an actuator which permits or causes the collector assembly to expand after deployment. The actuator may be mechanical in nature or electrolytic, or may include a balloon. When the actuator is mechanical, it is typically attached to the proximal end of the cage assembly to allow or cause controllable expansion of the cage assembly. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a generalized schematic of a portion of the arterial system of the head specifying in particular the position of an embolism in the middle cerebral artery. Figure 2 is a partial view of a catheter and a generalized rendering of the inventive device. Figures 3A and 3B show, respectively, a side, cut away view of a spiral version of the device as expanded and as unexpanded. Figures 4A and 4B show, respectively, a side, cut away view of a double spiral version of the device as expanded and as unexpanded. Figure 5A shows a close-up of braid section comprised of a wrapped wire. Figure 5B shows a close-up of braid section comprised of a wrapped ribbon. Figures 6A, 6B and 6C show a cut away side-view of the inventive device utilizing a balloon as an expansion actuator. Figure 7 is a close up partial cut away of a distal tip of the inventive device showing a desired way of fixedly attaching the cage element to the core wire. Figures 8A and 8B show a variation of the inventive device using an electrolytically erodable link as a means for allowing expansion of the included cage element. Figures 9A and 9B show partial, cut away, side view and cross sectional end views of the release mechanism shown in Figures 8A and 8B. Figures 10A, 10B, 10C, 10D and 10E show a generalized sequence of steps for use of the inventive device to remove an embolism. This device is a surgical implement. It is designed variously to move a thrombus aside and provide a fluid passageway along that thrombus or to penetrate and at least partially to retrieve emboli situated in human vasculature. It is intended to be used rapidly as a flow restoration device. Even in those instances where the embolism is not or cannot be completely removed, this inventive device' is believed to be useful in displacing, extracting, or removing a portion of the clot and thereby permitting restoration of partial blood flow. It can be used to move the clot to a more advantageous site in the body. It is suitably flexible to be placed in the distal tortuous vasculature of the brain and hence is useful in treating blocking emboli found there. This device can be thought of as a partial treatment for embolic stroke. As a matter of practical experience, a large proportion of emboli sloughed into the brain are seldom longer than about 1 to 2 centimeters and, for a variety of reasons both physiological and hemodynamic, settle in the middle cerebral artery (MCA). As is shown in Figure 1, the path from the site of origin of a traveling embolus -- often the heart -- to the MCA is via the common carotid artery past the branch point forming the external and internal carotid arteries into the internal carotid artery (ICA). The MCA is generally considered to be the continuation and termination of the ICA after the siphon and after the branching sites of a variety of other arteries, e.g., the ophthalmic artery, the anterior communicating artery, the posterior communicating artery, and others. The etiology of such an occlusion is varied, varying, and complicated. The occlusion (100) is shown in the MCA in Figure 1 at the noted site. Treatments for such embolic occlusions include catheterization of the patient and introduction of tissue plasminogen activator (TPA) or urokinase to the site of the occlusion. Additionally the embolic occlusion may be penetrated -- often with a microcatheter -- and the TPA or urokinase introduced distally of the occlusion. Removal of the catheter provides a modest passageway for resumed or increased blood flow past the then-partial occlusion. This inventive device is for the rapid restoration of fluid or blood flow past the occlusion. We have found that it can be used in a variety of ways. For instance, when approaching the clot from the arterial end, the device can be used either to bypass the clot along the vessel wall and, upon expansion of the cage assembly, to allow flow of blood across the occlusion using the cage assembly as a fluid passageway. Alternatively, inventive device may be used to canalize or remove an occlusion, via the steps of penetrating the occlusion, expanding a cage assembly distally of the embolism, and preferably removing at least a part of the embolism along with the cage and its attendant catheter. Figure 2 is a diagrammatic portrayal of the major portions of a desired variation of the device and provides a general convention for several of the terms used herein. The assembly typically includes a core element, often a core wire (202), and a coil tip (204) to provide a measure of radio-opacity to the distal tip and protect against damage to the intima, and a cage assembly or element (206) which may be used as an embolism collector made up of a generally conical portion (208) having a decreasing radius and an optional cylindrical portion (210). Because of the "fineness" of the device, the coil tip (204) may also serve the same function as a guidewire tip. The length of the coil tip (204) may be up to 4 or 5 centimeters in such cases. Further, and as is discussed below, the core element may be an assembly comprising a tubular member further containing a removable core or guidewire. The cage assembly (206) is collapsible for passage along-side of or for penetration and passage through the embolism and is generally self expandable once it passes the embolism. Other procedures and devices may, obviously, be used to expand the cage assembly (206) and are discussed at some length below. The cage assembly (206) generally self-expands when the actuator element (212) is permitted to move from its introduction position to its deployment position. Attached proximally to the actuator element (212) is a sheath (214) extending back to the catheter assembly (216) to the person performing the procedure. The catheter assembly (216) is shown with an optional micro-balloon (218) which may be useful in some embolectomy procedures, and two radio-opaque bands for the purpose of allowing the user to visualize the tip of the catheter (216) in relation to the tip coil (204) in the embolism to be removed. Figures 3A and 3B show cross-sectional side views of a variation of the inventive device (250). This variation of the inventive device (250) includes a cage assembly (252) having a distal conical portion (254) and a cylindrical portion (256). The distal end of the distal conical portion (254) is fixedly attached to the core wire (258). Attachment may be by any convenient procedure, e.g., soldering, welding, gluing, etc. A preferred structure for such tip coil (258) is discussed below. The cage assembly (252) is preferably made of a super-elastic alloy wire or ribbon. Some stainless steels are suitable but the ready availability of nickel-titanium alloys in a wide variety of shapes and sizes makes this choice an easy one. In particular, we have found that ribbons as thin as 0.02 mm (0.75 mils) in thickness and as narrow as 0.05 mm (2 mils) in width are suitable for this device. Thicker and wider ribbons are also suitable in some instances as the situation requires. Preferred ribbons for the cage assembly (252) are between 0.02 and 0.038 mm (0.75 and 1.5 mils) in thickness and 0.076 and 0.1 mm (3 and 7 mils) in width. Most preferred are 0.02 and 0.1 mm (0.8 mils and 4 mils) respectively. A technical basis for the term "super-elastic" is found in the class of nickel-titanium alloys known as "nitinol" -- alloys discovered by the United States Navy Ordnance Laboratory. These materials are discussed at length in U.S. Patent Nos. 3,174,851 to Buehler et al; 3,351,463 to Rozner et al; and 3,753,700 to Harrison et al. Alloys especially suitable for this invention are those containing at least 1.5% (wt) and up to about 8% (wt) or more, of one or more alloying members selected from the group consisting of vanadium, chromium, manganese, iron, and cobalt. By the term "ribbon", we intend to include elongated shapes, the cross section of which are not square or round and may typically be rectangular, oval, or semi-oval. They should have an aspect ratio of 0.5 (thickness/width) or less. The cage assembly (252) may be made by winding a ribbon onto a mandrel having exterior form to produce the relaxed shape found in Figure 3A. The mandrel and wound ribbon are preferably heated for a suitable period of time (e.g., 750° to 1200° F for one-half to two hours) to produce an embolism cage assembly (252) which has the portrayed shape. For use in the MCA, the outer diameter of the device after deployment need not be any larger than about 3 mm. It is desirable that the collapsed or non-deployed device have a diameter no larger than about I mm. The expansion ratio between any of the deployed and deployable devices discussed herein typically need not be any more than about 3:1 to be effective in the MCA. Expansion ratios between 2:1 and 10:1 are appropriate in this invention. These ratios are suitable for each variation of the invention. The invention is not so limited, however. The actuator (260) may be independently produced from the cage assembly (252) or may be produced integrally with it. The sleeve (262) is attached, as appropriate, to the actuator (260). Each of the cage assemblies shown herein may also be made using wires rather than ribbons. By "wires" we mean to include filamentary shapes having cross-sections where the thickness/width ratio is greater than 0.5 to and including 1.0. The cross-sectional form may be circular, square, oval, etc. The cage assembly (252) is displayed in a relaxed or deployed condition in Figure 3A. Because the cage assembly (252) desirably is springy and self-expanding, it is allowed to expand solely due to the position of the actuator (260). In the actuator (260) position shown in Figure 3A, the cage (252) assumes the "relaxed" position. When the actuator (260) position is as shown in Figure 3B, the cage assembly (252) is pulled within close proximity of the core wire (258). The distal coil (204) is also shown in Figures 3A and 3B. Figure 3B shows the form of the device as it passes through the delivery catheter and is pressed through the embolism. The low profile or small cross-sectional area of the device (250) is apparent. In some designs of the device, it is permissible to use the actuator as an active deployment element rather than as a mere restraint on the premature expansion of the cage assembly. Figures 4A and 4B show a cross section of another variation of the inventive device related to that variation found in Figures 3A and 3B but employing a slightly more complicated cage assembly. In particular, Figure 4A shows an inventive device (270) having a pair (272, 274) of counter-wound ribbons serving as the cage assembly (271), each of which counter-wound ribbon (272, 274) is similar in construction and in materials of construction to cage assembly (252) in Figures 3A and 3B. Clearly the associated elements such as actuator (276, 278), core wire (280), actuator sheath (282), distal coil tip (284) are all similar in construction and use to the analogous parts found in Figures 3A and 3B. The variation shown in Figures 4A and 4B generally have the detriment of being somewhat thicker (or of a larger diameter) than the variations shown in Figures 3A and 3B. On the other hand, it may be expected to have a marginally higher spring rate and therefore self-expand more readily. The probability that the deployed device is centered in the chosen lumen is higher in the Figure 4A and 4B version as is the probability that it will collect a higher percentage of the errant embolism. As a matter of practicality, however, the usual path to a position venous of the embolism will be along the wall of the artery. Consequently, an ability to center in the vessel lumen is useful when the device is used primarily for removal of the clot rather than for merely its displacement. It should be noted that those earlier variations need not be linear as is shown there but may be curved in many different shapes. By "conical" or "cone" we mean simply that the tubular member forming the various embolism cage assemblies has a diameter which is larger at some position along the axis of that embolism cage assembly than at the site where it joins the core element but without regard to the outer profile of the element. That is to say that the profile of the embolism collector assembly element is not otherwise limited. The profile may be linear, curved, stepped, etc. As noted elsewhere, the location of the cage assembly should be visible using fluoroscopy. Various methods have been suggested above. One highly preferred method is shown in Figures 5A and 5B. In essence, at least some of the elements (ribbons or wires) making up the cage assembly are provided with significant radio-visibility via the placement of a radio-opaque covering on these elements. A metallic coating of a metal having comparatively more visibility, during fluoroscopic use, than stainless steel is preferred. Such metals are well-known but include gold and members of the platinum group of the Periodic Table, e.g., platinum, palladium, rhenium, rhodium, etc. The cage assembly wires or ribbons may be electroplated or otherwise provided with a continuous coating but a thick coating may be had by wrapping the element with a radio-opaque wire or ribbon. Figure 5A shows a portion of a cage assembly (325) made up of a woven braid of wires (326) which in turn are tightly wrapped with radio-opaque wires (327). The right side of Figure 5A is a partial cut away showing the wires (326) below the radio-opaque wires in cross-section (327). As an example of the device shown in Figure 5A, we have found that nickel/titanium superelastic alloy wire having a diameter in the range of 0.025 to 0.1 mm (0.001" to 0.004") wrapped with 0.025 to 0.05 mm (0.001" to 0.002") diameter platinum wire is suitable and is quite visible. Figure 5B shows a partial cut away of a cage assembly (328) constructed of ribbon (329) as described above and further wrapped with radio-opaque wires (327). As was the case with the Figure 3A variation, the right side of the drawing is a partial cut away showing the internal ribbon (329). The variations of the cage assemblies shown in Figures 5A and 5B may be used in place of any of the cage assemblies found elsewhere herein. Figures 6A, 6B, and 6C show a variation (350) of the inventive device depicting two independent concepts. First, the cage assembly (352) is braided and has no proximal sector. Second, the deployment is aided by the use of an optional micro-balloon (354). Specifically, cage assembly (352) is a rosebud-shaped braid (as shown in Figure 6B). It is maintained in a collapsed condition against core wire (358) by a number of actuators (360). The cage assembly (352) is constructed in the same way and using the same materials as those braided cage assembly discussed above. Although the cage assembly (352) is self-expanding, this variation of the invention includes a micro-balloon (354) which is shown inflated in Figure 10B and deflated in Figure 6C. The balloon (354) may be used in this way to assist in the expansion of the cage assembly (352). Although not critical to this variation, the balloon may be sized so that it does not extend to the proximal end of the cage assembly (352). In this way the balloon (354) is available to hold the cage assembly (352) in the center of the lumen, maintain a controllable amount of force on the cage assembly (352) radius, and yet maintain room within the proximal end of the cage assembly (352) for the desired embolus collection. Alternatively to (or in addition to) the balloon (354), actuator elements (360) may also be used to control the expansion of cage assembly (352). An axially movable sheath (362) may be used in conjunction with the actuator elements (360) in the manner discussed above. The actuator element (360), as well as each of the analogous elements discussed above, may either be very flexible in which case they are used only in tension to hold the cage assembly against the respective core wires or they may be of such a stiffness that they may be used both in tension to maintain the cage assemblies against the core wire and then used in compression to assist in expansion of the cage assembly. In general, the choice of size of the actuator elements is a matter for the designer of a particular variation of this device. The factors entering into such a decision include such diverse matters as the size of the vessel to be recanalized and its tortuousity, the length of the occlusion, and then secondarily, the composition and size of the components woven into the cage assembly. Figure 7 shows a detail of the most distal tip of the device and in particular depicts a desirable way to fixedly attach the cage assembly to the core wire. The distal assembly (400) utilizes a cage assembly (402) which at its most distal region is held against the core wire (404) by a (desirably) radio-opaque coil (406). An atraumatic tip (408) may be placed on the tip of the core wire (404). The tip (408) is typically of the same material as is the coil (406). These various pieces of metal (core wire (404), coil (400), and cage assembly (402)) may be . soldered together although other metal joining techniques such as brazing or welding may be used. A flux is used for soldering or brazing and must be chosen with care to achieve the desired joint amongst the various differing metals and alloys. Figures 8A and 8B show another variation of the invention using electrically erodable or electrolytically erodable bands to loose the self-expandable cage assembly in place of the actuator.elements or balloons. Figures 9A and 9B show details of one such erodable linkage. Figure 8A shows a braided cage assembly (440) held in tight compression against the core wire (442) by a pair of bands (444) having an electrically erodable link therein. Upon severing the link (shown as (444) by example in Figures 8A and 8B), the bands (444) open and the braided cage assembly (440) expands as shown in Figure 8B. This version has a number of benefits over the mechanical and hydraulic variations discussed earlier. First, the cage assembly (440) may be made of material having substantially more springiness than normally suitable for use when using mechanical releases. This is so because the mechanical release actuators have very little mechanical advantage in pulling the cage assembly down to the core wire since they run parallel to that core wire. Since the stress applied to the actuators must be offset by one in the core wire, the core wire must be made larger or of stiffer material to counteract the applied stress. The various tensions also make the assembly somewhat stiffer and therefore more difficult to manipulate in tortuous passageways. In contrast, the bound variations shown in Figures 8A, 8B, 9A, and 9B need not have the same axial mechanical strength to carry the axial stresses of the actuators. The core wire may then be made smaller and more flexible (if such flexibility is desired), and the cage assembly may be given more springiness than would be available in the mechanical release form. The detriment is that each of the elements in the assembly must be insulated from electrical contact with the bloodstream or constructed of materials which are more "noble" in the electromotive series than the material making up the erodable link. Insulating such components with coatings of PARALENE or polyfluorocarbon polymers is time-consuming and expensive. Electrolytic separation occurs after a small current is applied to insulated conductor (446) which is an electrical connection with the metallic sacrificial link (not shown in Figures 8A and 8B). The voltage passes through the sacrificial link into the surrounding blood and other fluids and completes the circuit through the body via an electrode placed, e.g., in or on the delivery catheter. Two bands (444) are shown in the drawings; more may be desirable or only one may be needed. The number and design of the bands is a matter of detail for the device designer. One desirable design for the release bands (444) is shown in Figures 9A and 9B. The band (444) is depicted as a split polymeric ring held tightly in place around the cage assembly (440) by a sacrificial link (450). The sacrificial link is, e.g., stainless steel wire of a diameter of about 0.025 mm (0.001 inches) and is electrically attached to an insulated power supply wire (446). The insulating covering (452) placed on the exterior of the core wire (442) may be seen in the Figures. It is within the scope of this invention that the distal coil tip be used as the return electrode completing the electrical circuit through the center of the core wire to the not seen power supply. Erosion of the sacrificial link allows the ring to open and the cage assembly to deploy. Figures 10A to 10E depict the generic procedural steps for the use of the inventive device. In Figure 10A, a catheter (600) is used to place the inventive device (608) just proximal of the embolism (604) to be removed. In this procedure, the inventive device is used as an embolectomy device. The cage assembly (606) is held against the core wire (608). Figure 10B shows the penetration of the occlusion (604) by the embolectomy device (602) and Figure 10C shows the embolectomy device emerging from the distal end of the occlusion (604). Figure 10D shows a cage assembly (606) after completion of its self-expansion. Figure 10E shows the embolism removing device (602) being moved proximally to remove the embolism (604). It should be apparent that the cage assembly of this invention may be re-collapsed and re-deployed as necessary to displace or collect emboli as necessary or desired. A final note on the construction of the devices: it is obviously valuable to be able to ascertain the outline of the cage assemblys discussed above both before and after deployment. Consequently, the use of radio-opaque markers is very valuable. The design and of such is routine and is within the skill of an ordinary designer in this art. Similarly, obvious variants of the invention described above are within the scope of the invention. This and other known or non-critical items have been omitted from the drawings for the sake of brevity and clarity of the invention disclosed here.

Claims: An embolism treatment device (250, 350, 608) comprising: (a) a core wire element (202, 258, 280, 358, 404) having a distal end and a proximal end and a longitudinal axis, (b) a cage assembly (206, 252, 271, 352, 402, 440, 606) consisting of at least one spirally wound metallic member (272, 274) and having a distal end and a proximal end, wherein said cage assembly is generally coaxial to said core wire element (202) and wherein said distal end of said cage assembly is fixedly attached to said core wire element, (c) an actuator (212, 260, 276, 278, 360) fixedly attached to said cage assembly proximally of the attachment of said cage assembly to said core wire element, said actuator comprising a tubular member (214, 262, 282, 362) and an actuator element (212, 260, 276, 278, 360, 446) coupling the tubular member to said cage assembly, and (d) a radioopaque coil (204, 284, 406) fixedly attached to said core wire element distally of said cage assembly, wherein said cage assembly has a first deployment shape when said actuator is in a first deployment position and a second larger expanded shape different from the first deployment shape when said actuator is in a second deployment position; characterised in that said cage assembly in its second expanded shape is substantially conical in shape with the proximal end of the cage assembly having a greater diameter than the distal end of the cage assembly such that the cage assembly is adapted to be used as an embolism collector. The device of claim 1, wherein said first deployment shape is adjacent said core wire (202, 258, 280, 358, 404). The device of claim 1 or claim 2, wherein the cage assembly further comprises a cylindrical section (210, 256) proximally of said distal end. The device of any one of the preceding claims, wherein the cage assembly (206, 252, 271, 352, 402, 440, 606) comprises at least two spirally wound superelastic alloy members (272, 274) selected from the group consisting of ribbons and wires, said members being wound respectively clockwise and counter-clockwise about the axis of the core wire. The device of any one of the preceding claims, wherein the cage assembly (3 52) comprises a plurality of ribbons woven into a braid. The device of any one of the preceding claims, wherein the cage assembly (206, 252, 271, 440) is self deploying. The device of any one of the preceding claims, wherein the cage assembly (206, 252, 271, 352, 402, 440, 606) comprises a nickel-titanium alloy. The device of any one of the preceding claims, wherein the cage assembly is contained in its said first deployment shape by an electrolytically severable band (444) adapted to be eroded by passing a current through said band to release the cage assembly for expansion to the second larger expanded shape. The device of any one of the preceding claims, wherein said cage assembly (206, 252, 271, 352, 402, 440, 606) is radioopaque under fluoroscopy. The device of any one of the preceding claims, wherein said at least one spirally wound metallic member (272, 274) is covered by a radioopaque covering. The device of claim 10, wherein the radioopaque covering comprises radioopaque wire (327) wrapped around said at least one spirally wound metallic member (326, 329). The device of any one of the preceding claims, wherein the actuator (212, 260, 276, 278, 360) is fixedly attached to said proximal end of said cage assembly (206, 252, 271, 352, 402, 440, 606).

Inventors: ENGELSON ERIK T, NGUYEN KIM, SAMSON GENE, WONG ROSE Y, ENGELSON, ERIK T., NGUYEN, KIM, SAMSON, GENE, WONG, ROSE Y.
Applicants: BOSTON SCIENT LTD, BOSTON SCIENTIFIC LIMITED
Application year: 1997
Main classification: A61B17
IPC codes: A61B17, A61M29, A61M25