Rotational thrombectomy device

A thrombectomy apparatus for breaking up thrombus or other obstructive material in a lumen of a vascular graft or vessel comprising a flexible sheath, and a wire positioned within the flexible sheath wherein the wire and flexible sheath are relatively movable. The wire is substantially sinuous in configuration and assumes a substantially sinuous shape when in the deployed position and assumes a straighter position in the retracted position. The wire is operatively connected to a motor for rotation of the wire to enable peaks of the sinuous wire to contact a wall of the lumen to break up the thrombus or other obstructive material.

BACKGROUND

1. Technical Field

This application relates to a vascular device and more particularly to a rotational thrombectomy device for clearing thrombus from dialysis grafts.

2. Background of Related Art

Hemodialysis is a well-known method of simulating renal (kidney) function by circulating blood. The kidneys are organs which function to extract water and urea, mineral salts, toxins, and other waste products from the blood with filtering units called nephrons. From the nephrons the collected waste is sent to the bladder for excretion. For patients suffering from chronic renal insufficiency, hemodialysis is life saving because it provides a machine to simulate the function of the kidneys, thereby enabling the patients to live independently between dialysis treatments.

In the hemodialysis procedure, blood is withdrawn from the patient's body and transported to a dialysis machine, also commonly referred to as a kidney machine. In the dialysis machine, toxins and other waste products diffuse through a semi-permeable membrane into a dialysis fluid closely matching the chemical composition of the blood. The filtered blood, i.e. with the waste products removed, is then returned to the patient's body.

In one approach, an arteriovenous fistula is created so a high rate of blood flows from the artery into the patient's vein. The blood is then withdrawn directly from the patient's vein (native vein fistula) providing high rates of blood flow. Since this approach requires multiple needle sticks in the vein to withdraw and return the blood, the vein can eventually be damaged beyond usability, blood clots can form and the vein can fail. Once the vein fails, it could no longer be used for access and an alternate site must be utilized.

To avoid the repetitive damage to the vein, dialysis grafts are used. These grafts, typically made of PTFE, are implanted under the patient's skin, typically in the patient's forearm, and the graft is sutured at one end to the vein (venous anastomosis) for outflow and at the other end to the artery (arterial anastomosis) for inflow. The graft is also typically a loop graft to provide greater access area. This graft, which functions as a shunt creating high blood flow from the artery to the vein, enables access to the patient's blood without having to directly puncture the vein. That is, the technician sticks the two needles into the graft to respectively withdraw and return blood to the patient, with the inlet on the arterial side for blood requiring filtration processing and the outlet on the vein side for return of processed blood from the dialysis machine.

The dialysis graft, while providing an advantageous arrangement for hemodialysis, may become inoperable after a period of time due to thrombus or clots formed as a result of the high rate of blood flow through the graft and repetitive injury at the venous anastomosis.

There have been various attempts to break up clots and other obstructing material in the graft. One approach is through injection of thrombolytic agents such as urokinase or streptokinase. These agents, however, are expensive, require lengthier hospital procedures and create risks of drug toxicity and bleeding complications as the clots are broken.

Other approaches to breaking up clots involve mechanical thrombectomy devices. For example, U.S. Pat. No. 5,766,191 discloses a cage or basket composed of six memory wires that expand to press against the inner lumen to conform to the size and shape of the lumen. This multiple wire device is expensive and can be traumatic to the graft, possibly causing damage, since as the basket rotates, the graft is contacted multiple times by the spinning wires. Other risks associated with the basket include the possibility of catching onto the graft itself and tearing the graft as well as catching and tearing the suture at the anastomotic site. Additionally, the basket can become filled with a clot which would then require time consuming withdrawal of the basket, cleaning the basket and reinserting it into the lumen.

Commonly assigned U.S. Pat. No. 6,090,118, incorporated herein by reference, discloses a wire rotated to create a standing wave to break-up or macerate thrombus. The single wire is less traumatic than the aforedescribed basket device since it minimizes contact with the graft wall while still effectively mechanically removing thrombotic material.

This device of the '118 patent is effective in atraumatically and effectively breaking up blood clots. The present invention likewise provides a marked advance over the prior mechanical thrombectomy devices such as the baskets. The present invention achieves the same advantages as the device of the '118 patent, however, it utilizes a wire with a substantially sinuous configuration to create a wave-like rotational device. Thus, it provides the additional advantages of increased reliability and consistency in creating the wave pattern since the wave pattern created by the standing wave of the '118 patent will depend more on the rotational speed and the stiffness of the wire. Additionally, the sinuous configuration enables creation of a wave pattern at a lower rotational speed.

Co-pending commonly assigned U.S. patent application Ser. No. 09/888,149 incorporated herein by reference, discloses a thrombectomy device having a double balloon structure. This device advantageously reduces the number of individual catheters required to perform the thrombectomy procedure and reduces the number of surgical steps. The present invention therefore provides in one version a double balloon device with a sinuous wire configuration. The advantages of the double balloon thrombectomy device in simplifying the procedure and reducing operating costs is explained in more detail below in conjunction with the comparative flow charts ofFIGS. 19-20.

SUMMARY

The present invention advantageously provides a thrombectomy apparatus for breaking up thrombus or other obstructive material in a lumen of a vascular graft or vessel comprising a flexible sheath and a wire of sinuous configuration positioned within the flexible sheath. The wire and flexible sheath are relatively movable so the wire assumes a sinuous configuration in a deployed configuration and assumes a straighter configuration in a non-deployed configuration. The wire is operatively connected to a motor for rotation of the wire to enable peaks of the sinuous wire to contact a wall of the lumen to break up the thrombus or other obstructive material.

Preferably, the wire is composed of an inner core and an outer layer. The inner core in one embodiment is formed by at least two wires twisted together. In a preferred embodiment, the distal portion of the flexible sheath is at an angle to a longitudinal axis of the sheath.

Preferably, the apparatus further includes a housing having a battery and a motor therein for causing rotation of the wire. In a preferred embodiment, a metal tube is operatively connected to the motor and the wire is connected to the metal tube such that rotation of the metal tube rotates the wire.

In one embodiment, the apparatus further includes first and second balloons and the flexible sheath has first and second lumens wherein the first lumen communicates with the first balloon and the second lumen communicates with the second balloon. In one of the double balloon embodiments, the first balloon is an angioplasty balloon and the second balloon is distal of the first balloon and configured for engaging and pulling an arterial plug into the graft.

The present invention also provides a thrombectomy apparatus comprising a flexible tube and a wire positioned within the flexible tube, wherein the wire and flexible tube are relatively slidable so the wire is movable between a substantially straightened position and a deployed position where it assumes a curved configuration. In the curved configuration the wire has a first arcuate region extending in a first direction and a second arcuate region spaced longitudinally from the first arcuate region extending in a second direction, wherein the first and second arcuate regions are configured to break up thrombotic material as the wire spins.

Preferably the wire is formed of an inner core of twisted wires and an outer layer.

In one embodiment, the apparatus includes an expandable balloon and the flexible tube contains a first lumen to receive the wire and a second lumen communicating with the balloon for injection of fluid to inflate the balloon.

The present invention also provides a thrombectomy apparatus comprising a flexible sheath and a wire rotatably positioned within the flexible sheath composed of at least one wire forming an inner core and at least one wire around the inner core to form an outer layer. The wire has a first arcuate region extending in a first direction, a second arcuate region extending in a second direction, and a substantially linear region, wherein the first and second arcuate regions break up thrombotic material in a vascular structure as the wire spins.

The present invention also provides a thrombectomy apparatus comprising a flexible tube, a wire of non-linear configuration positioned within the flexible tube and rotatable with respect to the flexible tube, first and second balloons inflatable to expand radially with respect to the flexible tube, and a motor for rotating the wire to break up the thrombotic material as the wire rotates (spins).

The present invention also provides a thrombectomy apparatus for performing a thrombectomy procedure to break up thrombus from a graft functioning as a shunt between an artery and a vein. The apparatus comprises a flexible catheter having a declotting mechanism to break up thrombotic or other obstructive material, a first angioplasty balloon inflatable to expand radially with respect to the flexible tube to perform angioplasty, and a second balloon inflatable to a configuration capable of pulling vascular material into the graft.

A method for breaking up thrombotic material from a lumen of a vascular graft or vessel is also provided. The method comprises:

inserting a sheath;

exposing a rotatable wire with respect to the sheath, the wire having a sinuous configuration; and

rotating the wire so the peaks of the sinuous wire directly contact the graft wall as the wire spins.

A method for performing a thrombectomy procedure to break up thrombotic material in a vascular graft which forms a shunt between an artery and a vein is also provided. The method comprises:

inserting an introducer sheath;

providing a thrombectomy device having at least one inflatable balloon;

inserting the thrombectomy device through the introducer sheath and into a vascular graft;

inflating the at least one balloon to expand the balloon radially from the thrombectomy device;

deflating the balloon; and

actuating the thrombectomy device to break up thrombotic material from the graft.

The method may further include the step of inflating a second balloon on the thrombectomy device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now in detail to the drawings where like reference numerals identify similar or like components throughout the several views,FIGS. 1 and 2illustrate a first embodiment of the thrombectomy apparatus of the present invention, designated generally by reference numeral10.

Apparatus10has a housing12composed of housing halves12a,12b, a flexible tube or sheath40and a rotational thrombectomy wire60contained within the flexible sheath40. A knob42, extending from distal end14of housing12, is attached to the flexible sheath40to enable both rotation and sliding movement of the flexible sheath (tube)40with respect to the wire which is fixed axially. Note that although the flexible sheath40is shown as slidable and the wire60is fixed axially, alternatively, the wire can be axially slidable with the sheath40stationary, or both the wire60and sheath40can be slidable. In any case, relative movement of the wire60and sheath40will enable the wire60to be exposed to assume the curved configuration described below to enable removal of obstructions, such as blood clots, from the lumen of the vascular structure, i.e. the vascular graft or the vessel wall.

With reference toFIG. 3, details of the internal structure of the apparatus10will be described. Contained within housing12is a motor22powered by a battery24. Actuation button30is electrically connected to contact terminal26bof battery24by button wire28b; motor22is electrically connected to contact terminal26aof battery24by battery wire28a. Actuation button30is connected to motor22via wire strip25such that depression of button30, which is accessible from the top portion of housing12, turns on motor22to activate the apparatus. Battery door33can be provided to allow access to the battery24.

Wire60is operatively connected to motor22via support tube36which is preferably composed of metal. Support tube36extends through opening53in Touhy borst50and into chuck38, where a small set screw (not shown) extends through the outer wall of the chuck38to engage and compress the support tube36to maintain it in engagement with chuck38. Belt29connects motor22to chuck pulley or speed reducing gear37to decrease the rotational speed, for example from 10,000 rpm to 3,000 rpm. Shaft39of chuck38extends through chuck pulley37. Motor gear27engages chuck pulley or reducer gear37. With this connection, when motor22is energized, the support tube36is rotated about its longitudinal axis, via rotation of chuck38driven by gears27,37, thereby rotating the wire60about its longitudinal axis. This rotation of wire60creates at least one vortex that macerates and liquefies the thrombus into small particles within the vascular lumen.

As noted above, flexible tube (sheath)40is slidable with respect to the housing12and wire60. Flexible tube40is also rotatable. More specifically and with reference toFIGS. 3,7and8, knob42has a gripping region46and a shaft48, with a lumen extending therethrough. Strain relief49is frictionally fit, insert molded or attached by other suitable means to knob42and flexible tube40is connected to strain relief49(FIG. 3) by insert molding or other suitable means. With this attachment, sliding movement of knob42accordingly slides sheath40axially and rotation of knob42accordingly rotates sheath40about its longitudinal axis. Sliding movement of knob42exposes rotational wire60, enabling it to assume its curved configuration; rotation of knob42orients the rotational wire60due to the J-shaped distal end of tube (sheath)40, designated by reference numeral47. The proximal end of gripping region46contains external threads (not shown) for threaded engagement with the distal end of housing12to lock the sheath40in the advanced position to maintain covering of the wire60. Extension48of knob42has external threads (not shown) for threaded engagement within touhy50to lock the sheath40in the retracted position to maintain exposure of the wire.

The flexible sheath40can optionally contain one or more braided wires embedded in the wall to increase the stiffness. Such braided wires would preferably extend the length of the sheath40, terminating proximal of the angled tip47.

Touhy50, having an extension arm52, is positioned within housing12and has a lumen53communicating with the lumen of flexible sheath40. Fluids, such as imaging dye can be injected through arm52, flowing through sheath40in the space between wire60and the inner wall of the sheath40, and exiting distal opening41to flow into the graft or vessel. This imaging dye provides an indication that fluid flow has resumed in the graft. Touhy50contains a conventional silicone gasket which is compressed when tightened to provide a seal to prevent back flow of fluid around the support tube36. A radiopaque marker can be provided in the apparatus for imaging to visually locate the position of the apparatus.

Turning now to the rotational wire60and with particular reference to FIGS.2and4-6, wire60, in its expanded (deployed) configuration assumes a substantially sinuous configuration. This sinuous configuration resembles a sine curve.

As shown, wire60has a substantially linear portion extending through most of its length, from proximal region62, through intermediate region64to distal region66. At the distal region66, wire60has a sinuous shape in that as shown it has a first arcuate region63facing a first direction (upwardly as viewed in the orientation ofFIG. 3) and a second arcuate region65, spaced longitudinally from the first arcuate region63, facing a second opposite direction (downwardly as viewed in the orientation of FIG.3). These arcuate regions63,65form “peaks” to contact vascular structure as the wire60rotates. The distal tip69of wire60continues upwardly as a continuation of the “sine curve” configuration. An atraumatic tip70, preferably composed of rubber, Pebax, or other elastomeric materials, although other materials are also contemplated, is insert molded or otherwise attached to the distalmost tip of the wire60to provide the apparatus10with an atraumatic distal tip to prevent damage to the graft or vessel wall during manipulation and rotation of the wire60.

When the sheath40is in the advanced position, the curved regions of the wire60are compressed so the wire60(including the distal region66) is contained in the tube40in a substantially straight or linear non-deployed configuration. This covering of the wire60by sheath40facilitates insertion through an introducer sheath and manipulation within the vascular structure. When the flexible sheath40is retracted by proximal axial movement of knob42, the distal region66of the wire60is exposed to enable the wire60to return to its non-linear sinuous configuration shown in FIG.2. The wire60is preferably composed of stainless steel which is pre-bent to the curved configuration of FIG.4and returns to this position when released from the flexible sheath40.

In one embodiment, the wire60is composed of an inner core61and outer layer or coil68. Inner core61can be formed by twisting three wires together in a tight configuration. Outer coil68is formed by winding a wire, preferably of larger diameter, to form an opening therethrough. Note the pitch of the outer coil68in region67increases as it is slightly stretched to facilitate attachment of the tip70. In manufacture, the inner core61is slid within the opening of outer coil68, and the core61and coil68are welded together at a proximal and distal end. This tightly wound outer/inner core structure enables rotation of the distal end of the wire60corresponding to rotation at its proximal end as torque is transmitted to the distal end. Rotation of the sinuous wire60results in a spiral path to simulate a multiple wire basket configuration, however with a reduced traumatic affect since contact with the vascular structure occurs a fraction of the time.

Various dimensions of the wire and flexible tube are contemplated. By way of example only, in one embodiment, where the flexible tube40has an outer diameter of about 0.062 inches, the curved regions of the wire60would extend from the longitudinal axis a distance of about 0.188 inches and the radius of curvature at region65would be about 0.376 inches in a wire having an overall diameter (combined outer coil and inner core) of about 0.035 inches. As can be appreciated, these dimensions are provided by way of example as other dimensions are also contemplated.

In use, the thrombectomy apparatus10is inserted into the graft (or vessel) through an access sheath and located via imaging. Once in the graft, the flexible sheath40of apparatus100can be rotated so the J-tip47is oriented to the desired position. Once in the desired position, the flexible sheath40is retracted, and button30is depressed to actuate motor22, thereby causing support tube36and wire60to rotate about their longitudinal axis, causing the arcuate regions63,65to directly contact and break up the thrombotic material inside the lumen of the graft (or vessel). Note that the location of the access sheaths for introducing the thrombectomy apparatus10can be appreciated by the illustration inFIG. 13which shows use of apparatus100discussed below. Although the procedural steps differ between apparatus10and apparatus100, the introducer sheath location could be the same. The introducer sheaths can optionally have side ports for aspirating the small macerated particles.

Alternate Embodiment—Thrombectomy Device with Balloon(s)

FIG. 9illustrates an alternative embodiment of the thrombectomy apparatus of the present invention, designated generally by reference numeral100. Thrombectomy apparatus100is similar to apparatus10ofFIGS. 1-8, except for the provision of two inflatable balloons and two lumens in the catheter, each communicating with one of the balloons to allow passage of inflation fluid. Thus, the apparatus has a housing112, a flexible sheath (tube)140and a rotational wire contained within sheath140identical in configuration and function to wire60of the FIG.1. Knob144is rotatable to orient J-tip146and slides tube140to uncover the rotational wire in the same manner as knob42of FIG.1. Note thatFIGS. 9,11and12show both balloons inflated for illustrative purposes since in the preferred use of the apparatus as discussed in detail below, only one balloon would be inflated at a time.

The flexible sheath140of apparatus100has a lumen110, illustratively circular in cross-section, for receiving the rotational wire160, and first and second lumens113,114, each communicating with a balloon, for inflating the balloon. More specifically, first lumen113communicates with angioplasty balloon120, which is preferably somewhat elliptical in shape, and second lumen114communicates with balloon124, which is preferably substantially spherical in shape. Inlet ports130,132communicate with lumens113,114, respectively, to inflate the respective balloons120,124.

The double balloon thrombectomy apparatus100reduces the procedural steps for thrombus removal and can be appreciated by comparison of the flow charts ofFIGS. 19 and 20. In the prior art, two independent balloon catheters plus a mechanical thrombectomy device are required to perform a thrombectomy procedure; with the present invention, only one device, apparatus100, is required.

More specifically and with reference first to the anatomical drawing ofFIG. 13, a vascular graft G functions as a shunt between the artery A and vein V. Graft G is sutured to the artery at arterial anastomosis site210and is sutured to the vein at venous anastomosis site212. A venous access sheath218is inserted on the arterial side and extends through the graft G to access the venous side; an arterial access sheath214is inserted in the venous side and extends through the graft G to access the arterial side.

Describing first the prior art method, which is not shown, and with reference to the flow chart ofFIG. 19, an angioplasty balloon catheter is inserted through the venous access sheath and advanced to the venous anastomosis site, where the angioplasty balloon is inflated to treat the stenosis, i.e. expand the lumen by removing plaque. Then the angioplasty balloon is deflated and the balloon catheter is removed through the venous access sheath. Next a thrombectomy device is inserted through the venous access sheath into the graft. The thrombectomy device is then actuated to clear the thrombus and other obstructive material in the graft. The broken particles can then optionally be removed by suction with the thrombectomy device in place or after removal of the device from the graft.

Next, after removal of the thrombectomy device from the sheath, an arterial access sheath is inserted to access the arterial side. A balloon catheter, containing an expandable balloon such as a “Fogarty balloon”, is inserted through the sheath and advanced past the arterial anastomosis so the tip is past the arterial plug (clot) adjacent the anastomosis site. The balloon, preferably composed of Latex, although other materials are contemplated, is inflated, and the balloon catheter is moved proximally to pull the arterial plug into the graft. The balloon is then deflated and the balloon catheter is removed through the arterial access sheath. The thrombectomy device is then inserted through the arterial access sheath into the graft, and actuated to break up the arterial plug. The particles can optionally be removed from the graft by suction with the thrombectomy device in place or removed from the sheath. The thrombectomy device is withdrawn from the arterial access sheath to complete the thrombectomy procedure.

As can be appreciated, this prior art method requires two balloon catheters in addition to the thrombectomy device. Further, this prior art method is time consuming since it requires four instrument insertions and removals: angioplasty balloon catheter, thrombectomy device, balloon catheter, and thrombectomy device.

With the thrombectomy device ofFIG. 9of the present invention, these numerous catheter insertions and removals are avoided. As depicted in the flow chart ofFIG. 20, and as can be appreciated by the method drawings ofFIGS. 13-18, fewer steps are required.

After the venous access sheath218is inserted, the thrombectomy device100which contains an angioplasty balloon120is inserted through the sheath (FIG. 13) so tip146extends past plaque P. Angioplasty balloon120is inflated via lumen113as shown inFIG. 14to remove and compress the plaque P to open the lumen. The angioplasty balloon120is then deflated and the apparatus100is moved proximally so the rotational thrombectomy wire160is in the region of the graft G at the blood clot C as depicted in FIG.15. The apparatus100is then activated to spin the sinuous wire160to break up the thrombus and other obstructive material. Suction can then optionally be applied either with the apparatus100in place, with the particles being removed through the gap between the flexible sheath140and the introducer sheath218, or the apparatus100can be removed and suction applied through the sheath218.

After breaking up the blood clot, apparatus100is removed from venous access sheath218and inserted through arterial access sheath214. The apparatus100is inserted so the tip extends slightly beyond the arterial anastomotic site210, past the arterial plug (clot) D, and the spherical distal balloon124on apparatus100is inflated (FIG.16). The apparatus100is then pulled proximally so that balloon124pulls the arterial plug D into the graft G (FIG.17). The thrombectomy apparatus100can then be actuated to rotate wire160to break up the clot D (FIG. 18) and other obstructive material, and optionally the broken particles can be removed by suction as described above. The thrombectomy apparatus100is then removed through arterial access sheath214, completing the thrombectomy procedure.

It is also contemplated that as an alternative to the double balloon thrombectomy device, a single balloon device can be provided. This device could contain either angioplasty balloon120or balloon124. If only balloon120is provided, although the procedure would still require a separate balloon catheter to remove the arterial plug, it would still advantageously eliminate the step and expense of a separate angioplasty catheter. Alternatively, if the single balloon device contained only balloon124, although the procedure would require a separate angioplasty balloon catheter, it would still advantageously eliminate the step and expense of a separate balloon catheter for pulling the arterial plug into the graft.

It should also be appreciated that the double balloon concept to facilitate and expedite the surgical thrombectomy procedure can be utilized with other thrombectomy devices. For example, mechanical thrombectomy devices utilizing rotating wire baskets, fluid jet (hydrodynamic) devices applying high pressure fluid, devices utilizing brushes having bristles to scrape the clot and devices with rotating impellers can be modified to incorporate one or more balloons, i.e. an angioplasty and/or distal balloon to perform an angioplasty procedure and/or pull an arterial plug into the graft.

In the alternate embodiment of the thrombectomy apparatus inFIGS. 21-23, apparatus200(only the distal portion is shown) is identical to apparatus100except for shrink-wrap tubing202around a distal portion of the apparatus100to form an opening or lumen204for a guidewire. A guidewire206would be inserted through the arterial access sheath and past the stenosis (arterial clot). The guidewire206would then be threaded through the lumen204formed between tubing202and the outer surface209of flexible sheath212(which contains inflation lumens216and lumen218for the rotational wire). Guidewire206enters at entrance port216and exits through exit port214, to extend along the length of flexible sheath212. In this manner, this rapid exchange feature would allow the apparatus200to be more easily advanced past the arterial plug or stenosis as it is threaded over the guidewire.

As an alternative to the shrink wrap tubing forming the guidewire lumen, the catheter could be provided with an additional lumen formed therein, extending a short distance at the distal end portion, to accommodate the guidewire.

While the above description contains many specifics, those specifics should not be construed as limitations on the scope of the disclosure, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art will envision many other possible variations that are within the scope and spirit of the disclosure as defined by the claims appended hereto.