DEFLECTABE MEDICAL DEVICE

Abstract

A deflectable medical device (1) includes a shape memory alloy wire (15) integrated into a flexible elongated body (11). The shape memory alloy wire (15) is arranged to shorten upon receiving energy from an energy supply (2,4), thereby deflecting the medical device (1). A rod (18) positioned in a lumen (14) of the flexible elongated body (11) and compressed between a fixture (16) in the proximal end (12) of the elongated body (11) and the distal end (13) of the elongated body (11) is responsible for the shape memory alloy wire (15) recovering its initial length upon discontinuation of energy supply.

Claims

1. A deflectable medical device comprising: a flexible elongated body comprising a longitudinal axis; a shape memory alloy wire disposed within the flexible elongated body eccentric to the longitudinal axis, wherein the shape memory alloy wire is configured to shorten in an axial direction in response to receiving energy from an energy supply such that the flexible elongated body is deflected; and a rod disposed within the flexible elongated body, wherein the rod is configured to provide a force in the axial direction to lengthen the shape memory alloy wire when the energy supply discontinues providing the energy to the shape memory alloy wire.

2. The device of claim 1, wherein the energy supply is connected electrically to the shape memory alloy wire, and wherein the shape memory alloy wire is configured to convert electrical energy provided by the energy supply into heat through electrical resistance.

3. The device of claim 1, wherein the energy supply is connected electrically to a resistor disposed: proximate to the shape memory alloy wire; or coaxial with the shape memory alloy wire; or as a coating surrounding the shape memory alloy wire; or as windings of a material around the shape memory alloy wire.

4. The device of claim 3, wherein the resistor heats the shape memory alloy wire when energized with energy from the energy supply.

5. The device of claim 1, wherein the energy supply provides alternating current to a coil surrounding the shape memory alloy wire, and wherein the coil heats the shape memory alloy wire through induction when energized by the alternating current.

6. The device of claim 1, wherein the energy supply is a pump for providing fluid flow proximate to at least a portion of the shape memory alloy wire.

7. The device of claim 6, wherein the fluid flow is hotter than the shape memory alloy wire and provides heat energy to the shape memory alloy wire.

8. The device of claim 6, wherein the fluid flow is cooler than the shape memory alloy wire and removes heat energy from the shape memory alloy wire, such that the shape memory alloy wire is induced to lengthen in the axial direction in response to the fluid flow.

9. The device of claim 1, wherein a control unit controls a quantity of energy received from the energy supply by the shape memory alloy wire.

10. The device of claim 1, further comprising a handgrip on a proximal end of the device.

11. The device of claim 1, wherein the shape memory alloy wire comprises an alloy of NiTi, CuAlNi, CuZn, or NiTiPd.

12. The device of claim 1, wherein the shape memory alloy wire comprises a diameter of between about 50 micrometers and about 200 micrometers.

13. The device of claim 1, wherein the flexible elongated body comprises a polymer.

14. The device of claim 13, wherein the polymer comprises a thermoplastic elastomer.

15. The device of claim 14, wherein the thermoplastic elastomer comprises PEBAX.

16. The device of claim 1, wherein the shape memory alloy wire is incorporated into the flexible elongated body by overmolding.

17. The device of claim 1, wherein the flexible elongated body includes through-holes in a distal portion for dispensing fluid into a surrounding of the distal portion.

18. The device of claim 1, wherein a distal portion of the flexible elongated body further comprises a metallic tip for providing treatment energy to a surrounding of the distal portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the drawings:

[0029] FIG. 1 shows schematically and exemplarily an embodiment of a medical device according to the invention,

[0030] FIG. 2 shows schematically and exemplarily the medical device with deflected distal portion,

[0031] FIG. 3 shows schematically and exemplarily an embodiment of the medical device with deflected distal portion, the medical device comprising heterogeneous elongated body,

[0032] FIG. 4 shows schematically and exemplarily an embodiment of the medical device with shape memory alloy wire embedded into the elongated body,

[0033] FIG. 5 shows schematically and exemplarily an embodiment of the medical device with resistor positioned in the surrounding of the shape memory alloy wire,

[0034] FIG. 6 shows schematically and exemplarily an embodiment of the medical device with lumens in the elongated body adapted for fluid flow,

[0035] FIG. 7 shows schematically and exemplarily an embodiment of the medical device comprising a lumen for fluid flow and fluid dispensing holes in the distal portion,

[0036] FIG. 8 shows schematically and exemplarily an embodiment of the medical device with a metallic distal end,

[0037] FIG. 9a, 9b show transversal cross sections of alternative embodiments of the medical device,

[0038] FIG. 9c, 9d show transversal cross sections of alternative embodiments of the medical device comprising multiple shape memory alloy wires,

[0039] FIG. 10 shows schematically and exemplarily a system for deflection of a medical device according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0040] Navigation of medical devices through branching pathways sets stringent requirement with respect to device configuration. Besides reduced diameter and flexibility of the medical devices, steering of the distal portion is utmost important for the ability of reaching designated locations within anatomical structures. FIG. 1 shows an embodiment of a medical device 1 according to the invention. The medical device 1 is constructed from a flexible elongated body 11 having a proximal end 12 and a distal end 13, comprising a first lumen 14 visible in the longitudinal cross section B-B of the medical device, wherein a rod 18 is positioned. The rod may consist of compressible or incompressible materials. The proximal end 12 of the elongated body 11 comprises a fixture 16, the rod 18 extending from the fixture 16 to the distal end 13 of the elongated body 11. The proximal end 12 of the elongated body may be a handgrip. The functional designation of the fixture 16 is fixing and/or supporting the rod directly or indirectly, such that the rod 18 can be brought in a compression state between the fixture 16 and the distal end 13 with respect to the elongated body 11. The position of the fixture 16 may be variable with respect to the handgrip by sliding the fixture 16 through a slot 17. The fixture 16 may alternatively be a spindle mechanism. Depending on the mechanism used for the fixture, the rod 18 may extend proximally beyond the fixture 16 or even beyond the medical device 1. The rod 18 is arranged such that it is compressed between the fixture 16 and the distal end 13 of the elongated body 11, thereby generating a tensile stress in the elongated body 11. The fixture 16 may further comprise a loaded spring supporting the rod 18. The first lumen 14 may be positioned coaxially in the medical device as shown in FIG. 1, or it may be eccentric to the longitudinal axis, like in the FIG. 2.

[0041] A shape memory alloy wire 15, visible in the transversal cross section A-A and in the longitudinal cross section B-B, is arranged in a second lumen 19, extending at least partially along the elongated body 11 and positioned eccentric to the longitudinal axis 30 of the elongated body 11. Both ends of the shape memory alloy wire are fixed with respect to the elongated body 11. The shape memory alloy wire 15 is arranged to receive energy from an energy supply through wiring 20 connected to the proximal and distal ends of the shape memory alloy wire 15. By supplying electrical energy to the shape memory alloy wire, its temperature rises due to resistive heating.

[0042] The shape memory alloy wire 15, having an initial length, is arranged to shorten upon its resistive heating, which creates a pulling force on the elongated body 11 at the locations where both ends of the shape memory alloy wire 15 are fixed with respect to the elongated body 11. This creates a deflection of the portion of the elongated body 11 associated to the position of the shape memory alloy wire 15, due to the eccentric position of the second lumen 19 to the longitudinal axis 30 of the medical device 1. The longitudinal axis 30 is defined as the line connecting the centers of the transversal cross sections along the length of the medical device 1 in the neutral position, thus when there is no energy provided to the shape memory alloy wire. The radius of deflection R depends on the materials used for the manufacturing of the medical device 1, as well as on the design configuration. Usual candidates for the shape memory alloy wires are alloys of NiTi, CuAlNi, CuZn, NiTiPd with typical diameters of 50-200 micrometers. A broad range of polymers can be used for fabrication of the elongated body, from which the most known group is that of thermoplastic elastomers (e.g. PEBAX).

[0043] The benefit of using wires of shape memory alloys is the miniaturization potential of the medical device, since relatively thin shape memory alloy wires create sufficiently high force in axial stroke upon heating. The operation of the medical device relies on the lever that is created by the shape memory alloy wire positioned eccentric to the longitudinal axis 30 of the medical device, therefore a restoring bending force of a spring or that of supplementary structures, urging the shape memory element in a second direction away from the first direction upon cooling of the shape memory alloy wire, is not necessary. However, the shape memory alloy wire 15 requires axial tension to regain its initial length after discontinuing supply of energy to the shape memory alloy wire 15. Detwinning, the particular deformation mechanism partially responsible for the shape memory effect in addition to phase transformation, is promoted by the axial tension generated in the elongated body 11 due to the compression of the rod 18 between the fixture 16 and the distal end 13. Detwinning shape memory alloy wires in axial direction is less stringent and requires only sufficient axial tension in the elongated body, which allows manufacturing of medical devices with smaller diameter than those needing detwinning of laterally bending shape memory elements.

[0044] In the embodiment of the medical device shown in FIG. 3, the elongated body of the medical device is heterogeneous, specifically it is constructed from two materials with different properties. The proximal part of the elongated body 11 is made of a stiffer polymer which can additionally be reinforced with braiding to confer higher rigidity of the proximal portion of the medical device. The distal part 21 of the elongated body can be made of a more flexible polymer, as mostly the distal part of the medical device has different requirements in order to easily be deflectable when navigating in branching anatomical structures. The second lumen 19 extends at least partially in both segments of the elongated body, in the stiffer proximal part 11 and in the flexible distal part 21. The shape memory alloy wire 15, located in the second lumen 19 and fixed at both ends with respect to the heterogeneous elongated body, can be considerably long. A shape memory alloy wire of a certain material, hence with a defined maximum allowable strain, can produce a larger axial stroke for a longer segment when it is exposed to a difference of temperature. The deflection of the medical device due to the axial stroke created by the shortening of the shape memory alloy wire will not have its effect in the stiffer part, but the effect will be transferred almost entirely to the flexible distal part, resulting in a smaller radius of deflection r of the distal part of the medical device 1. In another embodiment of the medical device the stiffer and flexible regions of the elongated body may alternate repeatedly along the length of the medical device, resulting in complex three dimensional deflection of the medical device in operation.

[0045] The second lumen 19 in the elongated body is not directly necessary for deflecting a medical device, therefore the shape memory alloy wire 15 may directly be integrated in the elongated body, as shown in FIG. 4. The requirement for deflecting the medical device is that an axial stroke of the shape memory alloy wire 15 is created with respect to the longitudinal axis of the elongated body 11. Therefore, the shape memory alloy wire has to be fixed at least in two distinctive points with respect to the elongated body 11. Technology like overmolding allows incorporation of the shape memory alloy wire in the elongated body. When multiple contact points or regions exist between the elongated body 11 and the shape memory alloy wire 15 along their overlapping length, the friction between the two can be significant during relative motion occurring by deflection of the medical device. This can potentially limit the range of bending radii addressable by the medical device. Processing steps such as covering portion of the shape memory alloy wire with materials promoting low friction is a practical solution.

[0046] The shape memory alloy wire may be arranged to receive energy from an energy supply in numerous alternative ways. In an embodiment of the medical device 1 shown in FIG. 5, the elongated body 11 comprises a resistor connectable to an energy supply and arranged to convert the electrical energy received from the energy supply in heat for heating the shape memory alloy wire. The resistor may comprise windings 22 of metallic wire around the shape memory alloy wire 15, or it may be a metallic wire placed in the surrounding of the shape memory alloy wire. Alternatively, the resistor may be metallic structure coaxial with the shape memory alloy wire. This can be realized by conformal metallic coating of the shape memory alloy wire through various technological procedures (e.g. evaporation, electroplating, etc.).

[0047] A coil surrounding the shape memory alloy wire may also be used for induction heating of the shape memory alloy wire 15. Such embodiment may be similar to that presented in FIG. 5, wherein the induction coil 22 can be operated with a high-frequency alternative current.

[0048] The energy supply might be a pump circulating fluid in the surrounding of the shape memory alloy wire 15, the fluid having a higher temperature than the shape memory alloy wire. In a medical device with such a configuration, shown in FIG. 6, the shape memory alloy wire 15 receives energy from the fluid through heat transfer. A third lumen 23 and a fourth lumen 24 in the elongated body 11 are connected with each other in the distal portion of the elongated body, and they extend such that at least partially overlap in the axial direction with the shape memory alloy wire 15. The third lumen 23 is adapted to allow fluid inflow and the fourth lumen 24 to allow fluid outflow. The wiring 20 of the shape memory alloy wire 15 is superfluous and might be absent when fluid at higher temperature than that of the shape memory alloy is circulated for heating the shape memory alloy wire 15.

[0049] The medical device shown in FIG. 6 can alternatively be configured such that the shape memory alloy wire 15 receives electrical energy through the wiring 20 from the energy supply, and fluid at a lower temperature than that of the shape memory alloy wire 15, flowing through the third and fourth lumens 23,24, cools the shape memory alloy wire. The cooling fluid flow can significantly shorten the response time of the medical device to discontinuation of supplying energy to the shape memory alloy wire, thereby accelerating the recovery of the medical device to its neutral position.

[0050] In an alternative embodiment of the medical device shown in FIG. 7, the elongated body comprises just the third lumen 23, adapted only for fluid inflow. The third lumen 23 communicates with through-holes 25 in the distal portion 13 of the elongated body. The fluid flowing through the third lumen 23 is dispensed into the surrounding of the distal end 13 via the through-holes 25. Cooling of the shape memory alloy wire 15 with this configuration is advantageous for medical devices where irrigation with fluid is required (e.g. cardiac ablation).

[0051] FIG. 8 shows a medical device with distal portion ending with a metallic tip 26 for providing energy to the surrounding. In cardiac ablation the surrounding is heart tissue and the energy may be radiofrequency current delivered by a platinum-iridium alloy tip. The rod 18 can be supported by the metallic tip 26 at the distal end 13, or it can be fixed to it. In yet a further alternative, the rod 18 may be used as electrical connection of the metallic tip to the external radiofrequency current source.

[0052] Combination of the aforementioned embodiments may provide optimal solution for specific applications. The position of various components of the medical device may also vary. In the transversal cross section of a medical device, shown in FIG. 9a, the third and fourth lumens 23,24 adapted for fluid flow are at equal distance to the shape memory alloy wire 15, thereby further accelerating the recovery of the medical device to its neutral position upon discontinuation of supplying energy to the shape memory alloy wire. FIG. 9b shows an embodiment with a first lumen 14 having a larger cross section, wherein besides the rod 18 also the wiring 20 of the shape memory alloy wire as well as the third 23 and fourth 24 lumens are placed. The main advantage is an easier manufacturing of such a medical device.

[0053] Multiple shape memory alloy wires extending at least partially along the elongated body may be used in a medical device in order to increase the maneuverability of the medical device in multiple directions and/or to deflect differentially various segments of the medical device. In FIG. 9c a transversal cross section of an embodiment of the medical device is shown, comprising three shape memory alloy wires 15, allowing deflection of the distal portion of the medical device in any direction with respect to its longitudinal axis 30 by an appropriately harmonized operation of the individual shape memory alloy wires with dissimilar quantities of energy from the energy supply. In an alternative embodiment the medical device with multiple shape memory alloy wires 15 may have individual cooling lumens 23 for each shape memory alloy wire 15, as shown in FIG. 9d.

[0054] The deflection of the medical device needs to be controlled and reproducible for navigation within complex anatomical structures. A system 10 assuring reproducible deflection performance of the medical device is shown in FIG. 10. A control unit 3 is regulating the quantity of energy provided by the energy supply 2 to the shape memory alloy wire in the medical device 1. The control unit 3 and the energy supply 2 may be integrated in one unit. The system 10 may further comprise a pump 4 for circulating fluid through the lumens specifically designated therefore within the medical device 1. The pump 4 may also be controlled by the control unit 3 with respect to supplying fluid flow for the medical device at required temperature and volumetric flow rate. The pump may function in two regimes. The first regime is for cooling the shape memory alloy wires, therewith shortening the reaction time of the shape memory alloy wires to an alteration of the quantity of energy received from the electrical energy source 2. Alternatively, the pump 4 may also function as energy supply by providing fluid flow in the lumens at a higher temperature than that of the shape memory alloy wire, thereby transferring heat from the fluid in the lumens to the shape memory alloy wire positioned adjacent to the lumens in the medical device. The control unit 3 may further control the compression of the rod 18 between the fixture 16 and the distal end 13 of the medical device 1. The fixture 16 may be an electrically controllable spindle mechanism.

[0055] Controlling the deflection of the medical device comprising one or multiple shape memory alloy wires extending at least partially along the elongated body can be realized in steps. In a first step the control unit 3 provides a finite compression to the rod 18 fixed between the distal end 13 and the fixture 16 of the deflectable medical device 1. In the second step the control unit 3 regulates the quantity of energy necessary for the one or multiple shape memory alloy wires 15 to deflect the medical device 1 according to the required performance, and the energy supply 2 provides the respective quantity of energy to the one or multiple shape memory alloy wires 15. In step three the control unit 3 regulates the parameters of the pump 4 with respect to temperature of the fluid and volumetric fluid flow rate, according to the required deflection performance of the medical device 1. The steps may be carried out consecutively or simultaneously.

[0056] The control unit comprises a computer, a computer-readable medium having stored a computer-executable program and a user interface. The computer program comprises program code means for causing a deflectable medical device to carry out the steps for deflection of the medical device when the computer program is run on the computer of the control unit controlling the deflectable medical device.

[0057] Although medical device was used in the exemplary description of the invention, that should not be construed as limiting the scope.

[0058] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0059] A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0060] In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality.

[0061] Any reference signs in the claims should not be construed as limiting the scope.