Patent Description:
Clot retrieval catheters and devices are used in mechanical thrombectomy for endovascular intervention, often in cases where patients are suffering from conditions such as acute ischemic stroke (AIS), myocardial infarction (MI), and pulmonary embolism (PE). Accessing remote areas such as the neurovascular bed is challenging with conventional technology, as the target vessels are small in diameter, distant relative to the site of insertion, and are highly tortuous.

The clot itself can complicate procedures by taking on a number of complex morphologies and consistencies, ranging from simple tube-shaped structures which assume the shape of the vessel to long, strand-like arrangements that can span multiple vessels at one time. The age of a clot can also affect its compliance, with older clots tending to be less compressible than fresh clots. Fibrin rich clots also present a challenge in having a sticky nature that can cause a clot to roll along the outer surface of a mechanical thrombectomy device rather than being gripped effectively. Combinations of soft and firm clot regions can also separate during aspiration, with fragmentation leading to distal embolization which can occur in vessels that cannot be reached with currently available devices. Additionally, breaking the bonds adhering the clot to the vessel wall without damaging fragile vessels is a significant challenge.

Conventional clot retrieval catheters, especially those for operating in the neurovascular blood vessels, can suffer from a number of drawbacks. First, the diameters of the catheters themselves must be small enough to be advanced into the vasculature, which is very small in the context of the neurovascular system. The catheter must also be sufficiently flexible to navigate the vasculature and endure high strains, while also having the axial stiffness to offer smooth advancement along the route. Once at the target site, typical objects to be retrieved from the body can be substantially larger in size than the catheter tip, making it more difficult to retrieve objects into the tip. For example, fibrin-rich clots can often be difficult to extract as they can become lodged in the tip of traditional fixed-mouth catheters. This lodging can cause softer portions of the clot to shear away from the firmer regions, leading to distal embolization.

Small diameters and fixed tip sizes can also be less efficient at directing the aspiration necessary to remove blood and thrombus material during the procedure. The aspiration suction must be strong enough such that any fragmentation occurring through the use of a mechanical thrombectomy device or other methods can, at the very least, be held stationary so that fragments cannot migrate and occlude distal vessels. When aspirating with a traditional fixed-mouth catheter, however, a significant portion of the aspiration flow ends up coming from vessel fluid proximal to the tip of the catheter where there is no clot. This significantly reduces aspiration efficiency, lowering the success rate of clot removal.

The disclosed design is aimed at providing an improved aspirating retrieval catheter which addresses the above-stated deficiencies. The disclosure of <CIT> provides a medical device that can include an elongate manipulation member and an intervention member. The elongate manipulation member can include a distal end portion. The intervention member can include a proximal end portion and a mesh. The proximal end portion can be coupled with the distal end portion of the elongate manipulation member. The mesh can have a plurality of cells in a tubular configuration and being compressible to a collapsed configuration for delivery to an endovascular treatment site through a catheter and being self-expandable from the collapsed configuration to an expanded configuration. The mesh can include an anodic metal and a cathodic metal. The anodic metal and the cathodic metal can each form a fraction of a total surface area of the mesh. The disclosure of <CIT> provides a system that includes a catheter having a frame disposed proximate the distal end of the catheter. The frame expands to form a seal with the inner wall of a vessel. In some examples, the frame also captures a clot for removal from the vessel. The frame is manufactured from a shape memory material that can be heat set into a predetermined shape. An electrical connection to an electronic circuit causes a current to run through the frame. The electrical resistance of the shape memory material causes the frame to heat and transition from a martensite to an austenite phase. When the frame is heat set into an expanded configuration, the current causes the frame heat and expand. When the frame is heat set into a closed configuration, the current causes the frame heat and collapse upon a clot. The disclosure of <CIT> provides a lead locking device that has a lead insertion member having a proximal end and a distal end and has a lead engaging assembly. The lead insertion member defines a lumen extending along a longitudinal axis between the distal end and the proximal end of the lead engaging assembly. A mandrel disposed in the lumen of the lead engaging assembly extends along substantially the entire length of the lumen and protrudes beyond the most proximal end of the lead insertion member. The mandrel includes a distal portion in slidable contact with at least a portion of the lead engaging assembly. The lead engaging assembly has a first configuration while being inserted into a lumen of a lead and a second configuration while engaging the lead from within the lumen of the lead. The lead engaging member has at least two expansion jaws that, in the first configuration, define a substantially cylindrical body. The expansion jaws translate radially outwardly from the longitudinal axis to engage the lumen of the lead when in the second configuration. The disclosure of <CIT> provides a catheter that includes an elongate flexible tubular body, a distal zone of the tubular body comprising: a tubular inner liner; a helical coil surrounding the inner liner and having a distal end, a tubular jacket surrounding the helical coil, and extending distally beyond the helical coil distal end to terminate in a catheter distal face, and a tubular radiopaque marker embedded in the tubular jacket. The catheter distal face comprises a first section that resides on a first plane which crosses a longitudinal axis of the tubular body at a first angle within the range of from about <NUM> degrees to about <NUM> degrees, and a second section that resides on a second plane which crosses the longitudinal axis of the tubular body at a second angle within the range from about <NUM> degrees to about <NUM> degrees. The disclosure of <CIT> provides a system for delivering an implant within a patient.

The invention is defined in claims <NUM> and <NUM>. No surgical methods form part of the invention. Examples presented herein include devices and methods for removing acute blockages from blood vessels during intravascular medical treatments. More specifically, the present disclosure relates to an electrically actuated clot retrieval catheter system. An example system for retrieving an obstruction in a blood vessel can include a catheter, a metallic region, and two conductive wires. The catheter can have a wall that defines an inner lumen of the catheter. The inner lumen can extend between a proximal hub with an electrical current controller and a distal tip of the catheter. The metallic region can include at least two abutting metals in a coiled configuration, forming a bimetallic coil. The metallic region can be located at or near the distal end of the catheter. At least a first portion of a first metal of the metallic region can make up an outer perimeter of the bimetallic coil and at least a portion of a second metal of the metallic region can make up an inner perimeter of the bimetallic coil. The two conductive wires can extend along a longitudinal axis of the catheter and can be in electrical communication with the electrical current controller and in electrical communication with at least a portion of the metallic region.

At least a portion of the metallic region can be configured to reversibly expand from a tight configuration to an expanded configuration upon electrical current stimulation. The tight configuration can include a first diameter that is smaller than a second diameter of the expanded configuration.

At least a portion of the bimetallic coil can be affixed to the catheter at the distal tip and can be engaged with the two conductive wires. A current applied to at least a portion of the bimetallic coil from the two conductive wires can move the bimetallic coil along a deflection between a first end and a second end of the bimetallic coil to the expanded configuration.

The first metal of the at least two abutting metals of the bimetallic coil can include a first thermal expansion coefficient. The second metal of the at least two abutting metals of the bimetallic coil can include a second thermal expansion coefficient. The first thermal expansion coefficient can be different from the second thermal expansion coefficient.

The first metal can include a thermal expansion coefficient lower than the thermal expansion coefficient of the second metal.

At least part of the metallic region can include a radiopaque region.

At least a portion of the distal tip of the catheter can include an elastic jacket disposed around the bimetallic coil. The elastic jacket can form an elastic region of the catheter and can extend proximally from the distal tip of the catheter beyond the metallic region.

The elastic region can be configured to reversibly expand as the bimetallic coil expands from the tight configuration to the expanded configuration.

The system can further include a current path from the electrical current controller, through the two conductive wires, to at least one of a first end and/or a second end of the bimetallic coil affixed to the catheter, through a majority of a length of the bimetallic coil, and through a return path to the electrical current controller.

At least one of the two conductive wires can be electrically affixed to the first end of the bimetallic coil. A return path can include at least the other of the two conductive wires electrically affixed to the second of the bimetallic coil and extending along the longitudinal axis.

Another example system for retrieving an obstruction in a blood vessel can include a catheter and a bimetallic coil. The catheter can include a distal tip having an elastic region. The bimetallic coil can be positioned within the elastic region at the distal tip of the catheter. At least a portion of a first metal makes up an outer perimeter of the bimetallic coil and at least a portion of a second metal makes up an inner perimeter of the bimetallic coil.

At least a portion of the bimetallic coil can be configured to reversibly expand from a tight configuration to an expanded configuration. The tight configuration can include a first diameter that is smaller than a second diameter of the expanded configuration.

At least a portion of the bimetallic coil can be affixed to the catheter and can be encapsulated by an elastic jacket within the elastic region. The expanded configuration can include a deflection between a first end and a second end of the bimetallic coil.

The first metal of the bimetallic coil can include a first thermal expansion coefficient. The second metal of the bimetallic coil can include a second thermal expansion coefficient. The first thermal expansion coefficient can be distinct from the second thermal expansion coefficient. The first metal of the bimetallic coil can include a thermal expansion coefficient lower than the thermal expansion coefficient of the second metal of the bimetallic coil.

They system for retrieving an obstruction in a blood vessel can further include two conductive wires and a metallic region. The two conductive wires can extend along a longitudinal axis of the catheter. An electrical current controller can be configured to provide a first current to at least one of the two conductive wires. The metallic region of the catheter can be in electrical communication with the two conductive wires. The metallic region can include the bimetallic coil. At least a portion of the metallic region can include a radiopaque region. At least a portion of the metallic region can be configured to reversibly expand from a tight configuration to an expanded configuration upon electrical current stimulation.

An example method of retrieving an occlusive thrombus from a blood vessel of a patient can include attaching, at least a portion, of a bimetallic coil within a distal tip of a catheter, connecting a first end of a conductive wire to a metallic region including the bimetallic coil, and connecting a second end of the conductive wire to an electrical current controller. The bimetallic coil within the metallic region can include a first metal having a first thermal expansion coefficient and a second metal having a second thermal expansion coefficient distinct from the first thermal expansion coefficient. At least a portion of the bimetallic coil can be affixed to the catheter.

The method of retrieving an occlusive thrombus from a blood vessel of a patient can further include applying an electrical current, through the conductive wire, from an electric current controller to a first end of the bimetallic coil. The method can further include expanding, by the electrical current, the bimetallic coil from a tight configuration to an expanded configuration. The method can further include attaching an elastic jacket around the metallic region.

The above and further aspects of this disclosure are further discussed with the following description of the accompanying drawings, in which like numerals indicate like structural elements and features in various figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating principles of the disclosure. The figures depict one or more implementations of the inventive devices, by way of example only, not by way of limitation. It is expected that those of skill in the art can conceive of and combining elements from multiple figures to better suit the needs of the user.

The herein disclosed solution is directed to a clot retrieval catheter capable of expanding to form a funnel to reduce the risk of clot shear and restrict/arrest blood flow via a modular distal tip. Flow restriction and large tipped designs offer substantially greater aspiration efficiency and reduce the risk of emboli migration. Such advantages can also be especially beneficial in the case of stroke intervention procedures, where vessels in the neurovascular bed are particularly small and circuitous, and as a result a clot retrieval catheter with a tip that can expand and decrease can readily move through tortuous vessels while increasing the aspiration efficiency at the clot location. The catheter can also be compatible with relatively low-profile access sheaths and outer catheters, so that a puncture wound in the patient's groin (in the case of femoral access) can be easily and reliably closed. The catheter can also feature internal and/or external low-friction liners, and an outer polymer jacket, elastic sheath, or membrane disposed around the support structure. The membrane can be an elastomeric material that encapsulates the actuated catheter tip having a bimetallic coil at the mouth of the catheter or is fitted over the bimetallic coil so that the mouth of the catheter can move independently of the membrane. The elastomeric membrane can be tight or loose fitting. A loose-fitting elastomeric membrane will be easier to open than a tight-fitting membrane. The membrane can be baggy and made of a non-elastomeric material such that the force to open the membrane is low compared to that of a tight-fitting elastomeric membrane. The membrane can be inverted to extend distally from a proximal location radially inwardly of the mouth of the catheter before reverting back to extend proximally radially outwardly of the mouth of the catheter and wherein the inner and outer layers of the membrane are bonded or reflowed together at a proximal location or for the full length of the membrane. The membrane can comprise an inner and an outer tube, the proximal and distal ends of the inner and outer tube being bonded together or reflowed such that the two tubes form a sock around the catheter tip and bimetallic coil, the bimetallic coil being free to move and expand within the sock.

These improvements can lead to safe and more rapid access of a catheter and other devices to complex areas in order to remove occlusions and shorten procedure times. While the description is in many cases in the context of mechanical thrombectomy treatments, the systems and methods can be adapted for other procedures and in other body passageways as well.

Accessing the various vessels within the vascular system, whether they are coronary, pulmonary, or cerebral, involves well-known procedural steps and the use of a number of conventional, commercially-available accessory products. These products, such as angiographic materials, rotating hemostasis valves, and guidewires are widely used in laboratory and medical procedures. When these products are employed in conjunction with the system and methods in the description below, their function and exact constitution are not known in the related art.

The present systems and methods employ the characteristics of bimetallic materials to customize the distal dimensions of a clot-retrieval device. Bimetallic materials consist of two different metals which can bend or expand at different rates when heated or electrically stimulated. Different thermal expansions allow the bimetallic materials to bend in one direction when heated and in the opposite direction when cooled. Once the heat is removed from the bimetallic material, the material can return to its original position. Alternatively, or in addition thereto, when the heat is removed from the bimetallic material, the clot-retrieval device may be retracted into a guide catheter to assist with returning the bimetallic material to its original position. The bimetallic material can be set to bend or expand to a certain displaced position at a predetermined temperature. Note that while the description discusses bimetallic materials, the invention is not so limited. The inventors contemplate using any alloy that can produce the results described below. This ranges from impurities in a bimetallic alloy to an alloy of three or more elements, metallic or otherwise.

Various examples described herein can include bimetallic materials at the mouth of the catheter such that the mouth of a catheter can resemble a funnel shape once expanded that can exert a radial force on the vasculature. Fluid can be aspirated into the expanded funnel-shaped mouth and then into the catheter to capture a thrombus within the funnel. The bimetallic material can include an elastic jacket covering or membrane that directs the aspirate into the catheter. The bimetallic material can be disposed within an inner lumen of the catheter. As the bimetallic material expands and collapses, the inner diameter of the catheter can be increased and decreased to adjust the flow rate into the catheter.

The present disclosure provides a system for heating a metallic region to cause the bimetallic material to bend into an expanded configuration. One or more conductive wires can provide a current to the metallic region and/or the bimetallic material. The natural electrical conductivity of the bimetallic material can then cause the bimetallic material to bend into an expanded configuration. A thermocouple can also be provided to monitor the temperature of the metallic region and/or the bimetallic material such that the metallic region nor the bimetallic material overheat and cause trauma to the surrounding vasculature. In some examples, a thermoelectric cooling circuit, such as a Peltier chip, can be provided to transition the bimetallic material back into its original position or to bend the opposite direction to cause a tighter configuration of the catheter tip. The present disclosure provides various example designs for bimetallic materials.

Various devices and methods are disclosed for providing an electrically actuated clot retrieval catheter, and examples of the devices and methods will now be described with reference to the accompanying figures. <FIG> provide an illustration of an example clot retrieval system <NUM>. The system <NUM> can include a catheter <NUM> having a wall that defines an inner lumen <NUM> of the catheter <NUM>, an electrical current controller <NUM>, and a distal tip. The inner lumen <NUM> can extend between the proximal hub with an electrical current controller <NUM> and the distal tip. The system <NUM> can include a metallic region <NUM> comprising at least two abutting metals in a coiled configuration, the "bimetallic coil" <NUM>. The bimetallic coil <NUM> can be positioned at the distal tip of the catheter <NUM>. The bimetallic coil <NUM> can expand the distal tip of the catheter <NUM>, as shown in <FIG>. In some examples, the bimetallic coil <NUM> can be disposed within the inner lumen <NUM> of the catheter <NUM>, within the wall of the catheter <NUM>, or within a membrane, as will be described in greater detail below.

The bimetallic coil <NUM> can be encapsulated within an inverted membrane, dual layer sealed membrane or an overmoulded or dipped membrane, forming an elastic jacket, to be discussed further below. Where the bimetallic coil <NUM> is housed within an inner and outer membrane layer, the bimetallic coil <NUM> can have unhindered movement. Where an overmoulded membrane is supplied, there may be more resistance as the bimetallic coil <NUM> may be required to stretch more discrete areas of membrane material. It is appreciated that, as an electrical current will be passed through the metallic region <NUM> and/or the bimetallic coil <NUM>, the metallic region <NUM> and bimetallic coil <NUM> can be insulated in order to contain the electrical current. The membrane material can serve to insulate the metallic region <NUM> and the bimetallic coil <NUM>.

The bimetallic coil <NUM> can have an expanded configuration and a tight configuration. <FIG> shows a bimetallic coil <NUM> in the tight configuration, having a first diameter D1, while <FIG> shows the same bimetallic coil <NUM> in the expanded configuration, having a second diameter D2. In some examples, the expanded configuration can be a shape of a funnel.

The bimetallic coil <NUM> can include at least two abutting metals. As shown in <FIG>, at least a portion of a first metal <NUM> of the metallic region can be positioned on the exterior of the coil shape and form an outer perimeter of the bimetallic coil <NUM>. Similarly, at least a portion of a second metal <NUM> of the metallic region can be positioned on the interior of the coil shape and form an inner perimeter of the bimetallic coil <NUM>. The different metal materials can be joined together along their length by riveting, brazing, welding, or any other suitable manner to join two metal materials.

The first metal <NUM> can have a first thermal expansion coefficient. The second metal <NUM> can have a second thermal expansion coefficient. The first thermal expansion coefficient can be different than the second thermal expansion coefficient, such that the two abutting metals forming the bimetallic coil <NUM> can transition from a collapsed configuration to an expanded configuration, or vice versa, upon being heated and return to its previous configuration upon cooling. The metal material of the bimetallic coil <NUM> can include any suitable metal-based materials including, but not limited to steel, copper, and brass. In some examples, the bimetallic coil <NUM> can include two or more materials that have different coefficients of thermal expansion and can also include radiopaque and/or biocompatible metal-based materials. In one example, the bimetallic coil does not include shape memory material such as Ni-Ti (Nitinol). Alternately, Nitinol, in whole or in part, can be used for the bimetallic coil <NUM>, but its shape memory features are set to temperature generated by the electrical current controller <NUM> and not body temperature.

Metal-based materials with two or more different coefficients enable devices to be manufactured such that, once heated, the metal material having the lower thermal expansion coefficient can cause the bimetallic coil <NUM> of the device to bend or expand into an expanded shape. In general, the higher a coefficient of thermal expansion that a material has, the more the material will expand in response to being heated. Considering the example bimetallic coil <NUM> of <FIG>, the bimetallic coil <NUM> can be provided in a collapsed configuration (<FIG>). The bimetallic coil <NUM> can then be heated to a suitable temperature such that the material with a lower thermal expansion coefficient can bend and expand the bimetallic coil <NUM> and cause the distal tip of the device to form an expanded configuration (<FIG>). Once the source of heat is removed, either by removing the electrical current or other methods, the bimetallic coil <NUM> is re-cooled such that the material having the thermal expansion coefficient causes the bimetallic coil <NUM> to return to its tight configuration (<FIG>). In some examples, the cooling can be achieved easily through conduction with the wires and/or thermocouple wires, and subsequentially through the catheter <NUM> elastic jacket <NUM> disposed around the bimetallic coil <NUM> and/or membrane material. In certain examples, the elasticity of the elastic jacket <NUM> disposed around the bimetallic coil <NUM> may assist in causing the bimetallic coil <NUM> to return to its tight configuration.

<FIG> and <FIG> provide an example method of using the transition characteristics of bimetallic materials to actuate a clot retrieval system <NUM>. The actuated clot retrieval system <NUM> including the catheter <NUM> and bimetallic coil <NUM> can be advanced to a target site in a vessel containing a blood clot (BC). This can be completed by advancing the system <NUM> through an outer catheter. However, as will be described below, the catheter <NUM> and bimetallic coil <NUM> can be advanced to the target site without the need for an outer catheter. Once the catheter <NUM> and bimetallic coil <NUM> reach the target site, the bimetallic coil <NUM> can be in its tight configuration, as shown in <FIG>. This can enable the bimetallic coil <NUM> to advance through the tortuous blood vessel with ease. Once the bimetallic coil <NUM> is at the target site, the bimetallic coil <NUM> can be heated, which is described in greater detail below, to enable the bimetallic coil <NUM> to transition from the tight configuration to the expanded configuration. In the example shown in <FIG>, when heated, the bimetallic coil <NUM> expands to a funnel shape that can exert a force on the vessel. The clot can then be aspirated into the catheter through the expanded bimetallic coil <NUM> and removed from the target site. In some examples, the bimetallic coil <NUM> can be actively cooled such that the bimetallic coil <NUM> collapses into its tight configuration to capture the clot. Alternatively, the bimetallic coil <NUM> can automatically cool when the electrical current is removed from the bimetallic coil <NUM> and subsequently through the catheter <NUM> elastic jacket <NUM> disposed around the bimetallic coil <NUM> and/or membrane material. In addition, the elastic jacket <NUM> disposed around the bimetallic coil <NUM> may assist in causing the bimetallic coil <NUM> to return to its tight configuration once electrical current is removed from the bimetallic coil <NUM>.

Referring again to <FIG>, various bimetallic materials, including the alloys described above, have different linear thermal expansion coefficients, enabling the system <NUM> to be customized for the particular procedure. The bimetallic materials (first metal <NUM> and/or second metal <NUM>) can be selected or processed such that the thermal expansion coefficients are above human blood (e.g., above <NUM>) so that the bimetallic coil <NUM> is not inadvertently activated prior to reaching the intended activation location in a vessel. The thermal expansion coefficients of the materials can independently range from about <NUM> × <NUM>-<NUM> m/(m °C) to about <NUM> × <NUM>-<NUM> m/(m °C), which can correlate to a temperature range between <NUM> and <NUM> (e.g., between <NUM> and <NUM>, between <NUM> and <NUM>, etc.). Ideally the thermal expansion coefficients can correlate to a temperature range between about <NUM> to about <NUM>. This can help ensure expandable properties for a delivery configuration while minimizing the energy required to heat the bimetallic coil <NUM> for transition from the tight configuration to the expanded configuration.

As used herein, the terms "about" or "approximately" for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose. More specifically, "about" or "approximately" may refer to the range of values ±<NUM>% of the recited value, e.g. "about <NUM>" may refer to the range of values from <NUM> to <NUM>.

The bimetallic coil <NUM> can be heated by providing a current to the bimetallic coil <NUM>. The high electrical conductance of the bimetallic materials, for example steel and copper, can cause the bimetallic coil <NUM> to heat in response to the electrical current and the heat in turn cause the transition from the tight configuration to the expanded configuration. The system <NUM> can include a proximal hub with an electronic current controller <NUM> to provide the required current to the bimetallic coil <NUM>. The electronic current controller <NUM> can be activated with a switch, such as an on-off switch with electrical contacts that can be connected to an electrical current source. The electronic current controller <NUM> can include a colored LED bulb, or other suitable indicator. The colored LED bulb can flash when the bimetallic coil <NUM> is configured to expand in an "on" mode. The electronic current controller <NUM> can feed from approximately <NUM> mA to approximately <NUM> mA (e.g., approximately <NUM> mA to approximately <NUM> mA) to the bimetallic coil <NUM> using a power supply ranging, for example, from approximately <NUM> to <NUM> V, more preferably from approximately <NUM> to <NUM> V. The current can be pulsed from <NUM> to <NUM> msec, more preferable from <NUM> to <NUM> msec with a break in current of between <NUM> and <NUM> msec, more preferably from <NUM> to <NUM> msec. Pulsing allows the temperature of the bimetallic coil <NUM> to be maintained between a set temperature range, the on segment of the pulses heating and the off segment of the pulse allowing the bimetallic coil <NUM> to cool such that the temperature is kept between a range. The temperature can be monitored by a thermocouple such that the pulses can be altered if the temperature goes out of range; for example, a continuous feed of current can be used to ramp up the temperature quickly and the pulses can be lowered to keep the temperature of the bimetallic coil <NUM> under the upper range. The electronic current controller <NUM> can also have an opening <NUM> on the proximal end of the electronic current controller <NUM> to provide access to the inner lumen <NUM> of the catheter <NUM>. The opening <NUM> can be configured to fit a luer connector fitting with luer threads or other suitable connectors. The luer connector can provide access to the inner lumen <NUM> of the catheter <NUM>. As shown in <FIG>, the luer connector can include external threads to assist in providing secured access to the inner lumen <NUM> of the catheter <NUM>.

One or more conductive wires <NUM>, 400b (e.g., a positive lead and a negative lead) can extend between the electronic current controller <NUM> and the bimetallic coil <NUM> to provide the electrical current to heat the bimetallic coil <NUM>. The electrical current controller <NUM> can include an on-off switch with electrical contacts that can be connected to an electrical current source. The conductive wires <NUM>, 400b can be embedded within layers of the catheter <NUM> so that the wire is not exposed on the outer or inner surface of the catheter <NUM>. This can enable the system <NUM> to be advanced into an outer catheter without the wire restricting the movement of the system <NUM> through the outer catheter. The conductive wires <NUM>, 400b can comprise copper or any other material suitable to provide a current to the bimetallic coil <NUM>. Embedded conductive wires <NUM>, 400b throughout the length of the shaft of the catheter <NUM> can increase the tensile strength and resistance to stretching of the catheter <NUM> between the electronic current controller <NUM> and the bimetallic coil <NUM>. Increasing the strength of the shaft of the catheter <NUM> is desirable during aspiration and can offer greater aspiration efficiency and extraction of clots.

The system <NUM> can further include a thermocouple connected to the bimetallic coil <NUM> to monitor the temperature of the bimetallic coil <NUM>. If the bimetallic coil <NUM> is heated above a certain temperature, the bimetallic coil <NUM> can burn the surrounding vasculature. To prevent this, the thermocouple can monitor the temperature of the bimetallic coil <NUM> as it is heated by the current. If the bimetallic coil <NUM> exceeds a certain temperature, for example <NUM>, the thermocouple can communicate this information to the electronic current controller <NUM> to deactivate the current being supplied to the bimetallic coil <NUM>. The thermocouple can comprise a platinum, stainless-steel, or other suitable conductive wire that can be welded between the bimetallic coil <NUM> (e.g., at an anchor strut) and one of the two conductive wires <NUM>, 400b, where electronic current controller <NUM> measures the difference in resistivity between the bimetallic coil <NUM> and the thermocouple wire to determine the temperature of the bimetallic coil <NUM>. This can be calibrated and can have a linear temperature relationship.

The system <NUM> can include a thermoelectric cooling circuit in electrical communication with the bimetallic coil <NUM>. The thermoelectric cooling circuit can include, for example, a Peltier chip, disposed proximate the bimetallic coil <NUM>. As described above, when the bimetallic coil <NUM> is cooled, the metal material of the bimetallic coil having a lower thermal expansion coefficient can bend or transition back into the tight configuration. This can be completed to capture the clot in the bimetallic coil <NUM>. Instead of allowing the bimetallic material to cool naturally, the thermoelectric cooling circuit can pump heat from the bimetallic coil <NUM> to cool the bimetallic coil <NUM> more rapidly.

Although not shown, the system <NUM> can be used in combination with an aspiration source. In many cases the expanded bimetallic coil <NUM> can seal with the walls of the vessel at the target sit to direct aspiration to the distal end of the catheter <NUM>. In other words, the expanded bimetallic coil <NUM> can also arrest flow and prevent the unwanted aspiration of blood, or emboli migration proximal to the bimetallic coil <NUM>.

<FIG> and <FIG> depict the catheter <NUM> for the bimetallic coil <NUM> inserted through a blood vessel. In some examples, the catheter <NUM> may be inserted through an outer catheter, however, the outer catheter is not required. As depicted in <FIG> and <FIG>, the catheter <NUM> for the bimetallic coil <NUM> can be the only catheter required to be advanced from a guide catheter (guide catheter not shown in <FIG> or <FIG>). The catheter <NUM> and bimetallic coil <NUM>, for example, can travel farther away from a guide catheter because the system is highly flexible and self-actuating. Therefore, the guide catheter can reside in the internal carotid artery, for example, and catheter <NUM> and bimetallic coil <NUM> can extend entirely to an M1 or M2 vessel.

<FIG> are illustrations of exemplary bimetallic coil designs. The bimetallic coil <NUM> can have a variety of shapes, including an overlapping coil, or a spring coil. Alternatively, the bimetallic coil <NUM> can have a shape that reduces coil crossing or overlap when in the tight configuration, such as a step interlock coil (<FIG>), angle interlock coil (<FIG>), and the like. The length of the bimetallic coil <NUM> can be longer or shorter than the one shown. The length can be increased, for example, to provide more surface-area contact with the vessel wall or increase the reception space for a clot within the bimetallic coil <NUM>.

The metallic region <NUM> or the bimetallic coil <NUM> can be formed primarily of a non-radiopaque material such as steel and can include a radiopaque region <NUM> made of a radiopaque material such as platinum and/or tungsten. The radiopaque material and the non-radiopaque material of the bimetallic coil <NUM> can be concentrically welded. The radiopaque region <NUM> can be positioned within the bimetallic coil <NUM> or within the metallic region <NUM> near the bimetallic coil <NUM>. The radiopaque region <NUM> can be positioned a predetermined distance from a distal tip of the catheter <NUM> so that a physician can readily visualize the placement of the distal tip, the metallic region <NUM>, or the bimetallic coil <NUM> of the catheter <NUM> during a treatment procedure.

<FIG> and <FIG> are illustrations of exemplary actuated clot retrieval system having an expandable tip. The catheter tip can have an elastic region 300a that extends proximally from the distal tip of the catheter <NUM> and over at least a portion of the metallic region <NUM>. In some examples, the elastic region 300a extends over the entire metallic region <NUM>. For example, the metallic region <NUM> can extend proximally from the distal tip of the catheter <NUM> and along the longitudinal axis L-L for approximately <NUM> or less, while the elastic region 300a can extend proximally from the distal tip of the catheter <NUM> and along the longitudinal axis L-L for approximately <NUM> or more. The elastic region 300a can form an atraumatic tip at the distal tip of the catheter <NUM>. The bimetallic coil <NUM> can be enclosed within an elastic jacket <NUM>. The elastic jacket <NUM> can provide a means to direct fluid aspirate into the bimetallic coil <NUM> and into the catheter <NUM>. The elastic jacket <NUM> can also maintain the position of the bimetallic coil <NUM> in a collapsed configuration. Elastic jacket <NUM> materials can include suitable elastic polyurethanes such as Chronoprene, Chronosil, Chronoflex, and other silicon and urethane polymers and the like that have high elasticity and insulative properties with good tear resistance. The elastic jacket <NUM> can have a low hardness to enable the elastic jacket <NUM> to stretch when the bimetallic coil <NUM> is expanded. For example, the elastic jacket <NUM> can have a Shore hardness typical of <NUM> ranges and Shore A0. <NUM> to Shore A100 (e.g., Shore A40 to Shore A80). Because the elastic jacket <NUM> is encapsulating the bimetallic coil <NUM>, which may be intended to expand, the elastic jacket <NUM> can also have a degree of expandability, for example from <NUM> - <NUM>% (e.g., from <NUM> - <NUM>%).

The surface of the bimetallic coil <NUM> can be coated with a film of material with high dielectric strength such as Parylene to insulate the metal material from blood, which is a conductor, for example if the bimetallic coil <NUM> is not fully encapsulated or sealed by the elastic jacket <NUM>.

The bimetallic coil <NUM> can be held in place within the metallic region <NUM> at the distal tip of the catheter <NUM> by the elastic jacket <NUM> described above and by affixing the two conductive wires <NUM>, 400b. The two conductive wires <NUM>, 400b can be affixed by welding, riveting, brazing, or other suitable methods. In some examples, the two conductive wires <NUM>, 400b can be affixed to certain portions of the bimetallic coil <NUM> such that the first end <NUM> and the second end <NUM> of the bimetallic coil <NUM> can move or bend independently. Alternatively, the first end <NUM> of the bimetallic coil <NUM> can be affixed to the catheter <NUM> such that the first end <NUM> is fixed and the second end <NUM> is free to move or bend as the bimetallic coil <NUM> expands and contracts.

<FIG> is a cross-sectional illustration of an exemplary actuated clot retrieval system having embedded conductive wires. In some examples, insulating certain portions of the bimetallic coil <NUM> may enable the bimetallic coil <NUM> to have a distinct activation sequence. The first end <NUM> of the bimetallic coil <NUM> can be configured to expand upon receiving current and the second end <NUM> of the bimetallic coil <NUM> can be configured to tighten upon receiving current. This can enable the user to tighten or collapse the bimetallic coil <NUM> by applying a current to one portion of the bimetallic coil <NUM> instead of waiting for the metal material to cool. Current can flow through a negative lead into one side of a bimetallic coil <NUM> and flow in an even electrical resistance path to the other side of the bimetallic coil <NUM> where it returns through a positive lead. Segments of the bimetallic coil <NUM> can be divided by insulators and different segments can each have independent sets of positive and negative lead wires.

In some examples, instead of extending from the catheter <NUM>, the bimetallic coil <NUM> can be positioned within an inner lumen <NUM> of the catheter <NUM>. In a similar manner, as the bimetallic coil <NUM> expands inside the inner lumen <NUM>, the bore size of the catheter <NUM> can increase to adjust the flow.

<FIG> is a flow diagram illustrating a method of manufacturing a clot retrieval system. The method steps in <FIG> can be implemented by any of the example means described herein or by similar means, as will be appreciated. Referring to method <NUM> as outlined in <FIG>, in step <NUM>, method <NUM> can include attaching at least a portion of a bimetallic coil within a distal tip of a catheter. The bimetallic coil can include a first metal with a first thermal expansion coefficient and a second metal with a second thermal expansion coefficient distinct from the first thermal expansion coefficient.

In step <NUM>, method <NUM> can include connecting a first end of a conductive wire to a metallic region of the catheter. The metallic region can include the bimetallic coil such that the conductive wire is affixed to the metallic region or affixed directly to the bimetallic coil.

At step <NUM>, method <NUM> can include connecting a second end of the conductive wire to an electrical current controller.

Step <NUM> includes applying an electrical current, through the conductive wire, from the electrical current controller to the metallic region. Applying the electrical current to the metallic region may also include applying the electrical current directly or indirectly to the bimetallic coil. The user can activate the electronic circuit outside of the patient.

In step <NUM>, method <NUM> can include expanding, by the electrical current, the bimetallic coil from a tight configuration to an expanded configuration.

Although not shown, method <NUM> may further include attaching an elastic jacket around the metallic region such that the elastic jacket allows expansion of the metallic region, as described above.

Method <NUM> can end after step <NUM>. In other embodiments, additional steps according to the examples described above can be performed. For example, method <NUM> can include advancing a catheter to a target site through an outer catheter or access sheath. Method <NUM> can also include deactivating the first current to cool at least a first end of the bimetallic coil. Cooling the bimetallic material can cause the at least a first end to tighten upon the occlusive thrombus to improve the capture the thrombus for removal. Method <NUM> may further include aspirating the occlusive thrombus into the bimetallic coil. The aspiration can be directed into the catheter by the bimetallic coil. Method <NUM> can also include withdrawing the catheter with the occlusive thrombus from the patient. With the thrombus captured within the bimetallic coil, the thrombus can be pulled from the vessel of the patient without worry of the thrombus dislodging from the catheter due to poor capture.

In some examples, method <NUM> can include delivering a second current to at least a second end of the bimetallic coil. The second end can have a different transformation characteristic than the first end, such as a different thermal expansion coefficient. For example, the second end can be configured to bend the opposite direction to cause the bimetallic coil to tighten, which means that, once heated, it can collapse upon the thrombus. Accordingly, method <NUM> can include heating, via the second current, the second end of the bimetallic coil to cause the second portion of the bimetallic coil to change from an expanded configuration to a collapsed configuration and upon the occlusive thrombus.

Method <NUM> can also include cooling the at least a first end of the bimetallic coil with a thermoelectric cooling circuit to cause the at least a first end of the bimetallic coil to collapse or tighten upon the occlusive thrombus. A thermoelectric cooling circuit, such as a Peltier chip, can pump heat from a system. Using this effect, the thermoelectric cooling circuit can cause the at least a first end of the bimetallic coil to cool and collapse more rapidly around the occlusive thrombus.

Method <NUM> can include delivering the current in a series of pulses so as to maintain a steady bimetallic coil temperature, and the electronic circuit can monitor the temperature and adjust the pulse duration and/or length accordingly.

Method <NUM> can also include monitoring a temperature of the bimetallic coil with a thermocouple. In some examples, the thermocouple can monitor to determine if the bimetallic coil exceeds a certain temperature, for example <NUM>, and deactivate the first current if the bimetallic coil exceeds the temperature.

Claim 1:
A system (<NUM>) comprising:
a catheter (<NUM>) having a wall that defines an inner lumen (<NUM>) of the catheter, the inner lumen extending between a proximal hub with an electrical current controller (<NUM>), and a distal tip;
a metallic region (<NUM>) comprising at least two abutting metals in a coiled configuration (<NUM>) positioned at the distal tip of the catheter,
wherein at least a portion of a first metal (<NUM>) of the metallic region comprises an outer perimeter of the bimetallic coil (<NUM>) and at least a portion of a second metal (<NUM>) of the metallic region comprises an inner perimeter of the bimetallic coil (<NUM>); and
two conductive wires (<NUM>, 400b) extending along a longitudinal axis of the catheter in electrical communication with the electrical current controller and in electrical communication with at least a portion of the metallic region,
wherein at least a portion of the metallic region is configured to reversibly expand from a tight configuration to an expanded configuration upon electrical current stimulation, and
wherein the tight configuration comprises a first diameter that is smaller than a second diameter of the expanded configuration.