Patent Application
20160287178
The invention generally relates to the area of medical devices. More particularly, the present invention concerns a sensor guide wire for intravascular measurements of a physiological or other variable, e. g. pressure or temperature, inside a living human or animal body, the sensor guide wire including a proximal tube formed of two or more materials, each having a different Young's modulus to improve torque performance and maintain a low bending stiffness.
Equipment and processes have been developed for assisting medical personnel, such as physicians, in diagnosing physiological conditions of a patient. For example, sensor guide wires in which a sensor is mounted at the distal end thereof have been developed. The sensor may be, for example, an intra-vascular pressure sensor that is arranged to measure blood pressure at various points within the vasculature to facilitate locating and determining the severity of, for example, steno sis or other disruptors of blood flow within the vessels of the living body.
Sensor and guide wire assemblies in which a sensor is mounted at the distal end of a guide wire are known. In U.S. Pat. No. Re. 35,648, which is assigned to the present assignee, an example of such a sensor guide wire is disclosed, where a sensor guide wire comprises a sensor element, an electronic unit, at least one signal transmitting cable connecting the sensor element to the electronic unit, a flexible tube having the cable disposed therein, a solid metal wire, and a coil attached to the distal end of the solid wire. The sensor element comprises a pressure sensitive device, e.g. a membrane, with piezoresistive elements connected in a Wheatstone bridge-type of arrangement mounted thereon.
The above-mentioned solid metal wire, also called the core wire, extends from the distal end of the sensor guide wire to the proximal portion, where a male connector is arranged, and determines in part the overall mechanical properties, such as flexibility, torqueability and pushability, of the sensor guide wire. Sensor and guide wire assemblies for intravascular measurements are generally long, e.g. 100-300 cm, and have a small diameter, e.g. 0.35 mm. The core wire often extends along essentially the entire length of the sensor guide wire.
A proximal tube may extend from a proximal male connector to a jacket, inside which a sensor element is arranged. As an alternative, a proximal tube may extend from a proximal male connector to a coil, which, in turn, is connected to such a jacket. The core wire is inserted through a lumen of the proximal tube. The core wire may be longer than the proximal tube, and may extend from the proximal male connector, through the jacket, and to the distal tip of the sensor guide wire.
A core wire is a wire typically made out of metal and is typically of complex mechanical construction since it has to be steered often several feet into a patient, for example, from an opening in the femoral artery in the leg of the patient up to the heart through tortuous blood vessels. The mechanical characteristics (such as maneuverability, steerability, torqueability, and pushability) of a guide wire are very important to a surgeon because the surgeon grasps the proximal end of a guide wire (sticking outside the patient), and by manipulating the proximal end, steers the distal end of the guide wire, which is often several feet away.
Maneuverability describes the overall ability of the guide wire to travel through complex anatomies and is influenced by a number of factors including flexibility, strength, torqueability, pushability and friction within the anatomical environment.
Steerability describes a guide wire's ability to react to torque and push so that the distal end reaches parts of vessels as intended by the user. Steerability is primarily determined by the guide wire's stiffness and its thickness or strength.
Torqueability describes the ability of the guide wire to transmit a rotational displacement along the length of the sensor guide wire. When the rotational movements by the physician translate exactly to the tip of the sensor guide wire within the anatomy, the torque performance is high, so called “1:1” torque ratio.
Pushability describes the ability of the guide wire to transmit a longitudinal force from the proximal end of the shaft to the distal end. When a guide wire shaft has been designed to optimize pushability, it is easier for the physician to maneuver the sensor guide wire to the desired spot.
The guide wire is steered through the arteries, rather than being “pushed” or simply “introduced” through the arteries. A typical guide wire is very thin (typically 0.35 mm or less in diameter). Since the artery wall is soft, any attempt to use the artery itself as a guide for the guide wire could lead to penetration of the artery wall. The guide wire must be steered, for example, from an opening in the femoral artery in the leg of the patient up to the heart through tortuous blood vessels.
In order to increase torqueability, it is known to increase the bending stiffness of the proximal tube by selecting a material with a high Young's modulus. However, as the bending stiffness increases, the proximal tube exerts more pressure on the artery/catheter walls, thereby increasing the friction force on the guide wire. The increased friction contributes to a reduction in torque, which is counteractive to the purpose of the design. In addition, a higher bending stiffness increases the risk of the guide wire penetrating a blood vessel.
Thus, there is a need for an improved sensor guide wire having a proximal tube that exhibits improved torque performance, while maintaining a low bending stiffness.
In one embodiment, a sensor guide wire for an intravascular measurement of a physiological variable in a living body includes a sensor element configured to measure the physiological variable, and a proximal tube comprising a first material having a first Young's modulus and a second material having a second Young's modulus. The second Young's modulus is higher than the first Young's modulus. The second material is configured to improve torqueability.
In another embodiment, a method of forming a proximal tube for a sensor guide wire for an intravascular measurement of a physiological variable in a living body is described. The method includes providing at least one sheet made of one of 1) a first material having a first Young's modulus or 2) a second material having a second Young's modulus, providing a plurality of strips made of the other of the first material and the second material, joining the first material and the second material, and forming the joined first material and the second material into a hollow tube having the plurality of strips spaced along a length of the hollow tube. The second Young's modulus is higher than the first Young's modulus.
In yet another embodiment, a guide wire includes a tubular member having along its length a first material having a first Young's modulus and a second material having a second Young's modulus. The second Young's modulus is higher than the first Young's modulus. The tubular member has alternating portions of the first material and the second material.
All references cited in this disclosure are hereby incorporated by reference in their entireties for the devices, techniques, and methods described therein relating to medical sensors and devices, and for any disclosure relating to medical sensors and devices.
The features, aspects and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.
Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present invention is not limited to the details or methodology set forth in the description or illustrated in the figures.
The sensor element 111 may be used to sense any suitable physiological variable, such as, for example, pressure or temperature or flow. The sensor may be a microchip, a pressure sensitive device in the form of a membrane, a thermistor, a sensor for measuring the concentration or presence of a blood analyte, or other suitable pressure, temperature, or other variable-measuring device. Furthermore, the sensor element 111 may be a plurality of sensor devices. The physiological monitor 130 may use the sensor readings from the sensor element 111 to determine blood pressure, blood temperature, blood flow, the concentration or presence of one or more blood analytes, and/or Fractional Flow Reserve measurements (FFR). In short, FFR is used to identify constrictions of coronary vessels by obtaining the ratio between the pressure distally and proximally of a constriction.
The sensor element(s) 111 are connected to the microcables or optical signal lines 210, for transmitting signals between the sensor element 111 in the distal part of the guide wire and the connector 112 at the proximal end of the proximal tube 203. Examples of suitable microcables are described, for example, in U.S. Patent Application Publication No. 2010/0228112, U.S. Patent Application Publication No. 2011/0213220, and U.S. Patent Application Publication No. 2012/0289808, all of which are hereby incorporated by reference in their entireties for their teachings related to microcables in guide wire assemblies and the structure and use of guide wire assemblies.
The sensor guide wire 110 may optionally comprise a safety wire 211, which is attached in the tip 207 and extends preferably to the proximal connector 112. In case of an accidental break of the sensor guide wire 110 when, for example, a doctor tries to push the sensor guide wire 110 through a sharp bend in an artery of a patient, the safety wire 211 will make it possible to retrieve all parts of the sensor guide wire 110 from the patient's artery. The safety wire 211 may also be helpful during manufacturing of the sensor guide wire 110 in that the safety wire 211 can act as a guide when the different parts are assembled and threaded over each other. The safety wire 211 may alternatively have a shorter extension along the sensor guide wire 110, typically from the tip 207 to the jacket 205.
In
A=the length of the distal end portion=about 2 cm to about 3 cm;
The diameter of the sensor guide wire 110 preferably varies between about 0.25 to about 2.5 mm; for use in coronary arteries, for example, the diameter is normally about 0.35 mm. In the context of length, width, diametrical, and other spatial dimensions, the modifier “about” can include a deviation of plus or minus 0 to 10% of the amount it modifies, preferably plus or minus 0 to 5% of the amount it modifies.
It should in particular be noted that the length of the jacket or sleeve 205 is rather small in comparison with the total length of the sensor guide wire. For example, the jacket or sleeve 205 can range about 0.01% to 5% of the total length of the sensor guide wire, preferably 0.025% to 2.5% of the total length of the sensor guide wire, more preferably 0.05% to 1.5% of the total length of the sensor guide wire.
The proximal tube 203 may be made of two or more materials, each having a different Young's modulus.
Referring now to
The first material 300 may be stainless steel, a super elastic alloy, such as Nitinol, copper-tin, copper-zinc, or copper-zinc-tin, or another metal or metal alloy. The first material 300 may also be an Al—Mg—Cu alloy, an Al—Mg alloy, or an Al—Cu alloy. The second material 310 may be any material having a higher Young's modulus than the first material 300 selected. For example, the second material 310 may have a Young's modulus 10%, 30%, or 50% higher than the Young's modulus of the first material 300. For example, the second material 310 may be made of tungsten, molybdenum, alloys thereof, or another metal or metal alloy. In one example, if a very soft alloy such as a Cu alloy or an Al alloy having a low Young's modulus is used as the first material 300, steel can be used as the second material 310 since steel has a higher Young's modulus than a Cu alloy or an Al alloy.
The presence of the second material 310 (i.e., a high Young's modulus material) at or around the circumference of the proximal tube 203 improves the transfer of a rotational force from the proximal end to the distal end of the guide wire, when the guide wire is rotated at the proximal end. The presence of the first material 300 (i.e., a low Young's modulus material) at or around the circumference of the proximal tube 203 allows the guide wire to bend in a direction perpendicular to the longitudinal axis of the guide wire.
In the embodiment of
The first material 300 and the second material 310 are joined by roll bonding, the sheet of the first material 300 (with the second material 310) is rolled, and ends of the sheet are welded to form a hollow tube having varying stiffness along its length. In other words, the proximal tube 203 will have alternating segments of a low Young's modulus material (i.e., the first material 300) and a low Young's modulus material (i.e., the first material) reinforced with a high Young's modulus material (i.e., the second material 310). Other suitable methods of joining the first material 300 and the second material 310 may be used, for example, welding, a combination of welding and a known forming process, or an explosion welding/bonding technique. The plurality of strips of the second material 310 may be placed so that the second material 310 is provided on an outer circumference of the proximal tube 203 (see
The plurality of strips of the second material 310 may be evenly spaced along the full length of the proximal tube 203. The spacing of the plurality of strips of the second material 310 may be varied to adjust the flexibility and torqueability of the proximal tube 203. For example, the plurality of strips of the second material 310 may be spaced further apart in portions of the proximal tube 203 that require more flexibility (e.g., the end of the proximal tube 203 closer to the sensor element 111) and/or spaced closer together in portions of the proximal tube 203 that require more stiffness (i.e., less flexibility).
In the embodiment of
The first material 300 and the second material 310 are roll bonded, and the sheet of the second material 310 (with the first material 300) is rolled, and ends of the sheet are welded to form a hollow tube having varying stiffness along its length. In other words, the proximal tube 203 will have alternating segments of a high Young's modulus material (i.e., the second material 310) and a high Young's modulus material (i.e., the second material 310) reinforced with a low Young's modulus material (i.e., the first material 300). Other suitable methods of joining the first material 300 and the second material 310 may be used, for example, welding, a combination of welding and a known forming process, or an explosion welding/bonding technique. The plurality of strips of the first material 300 may be placed so that the first material 300 is provided on an outer circumference of the proximal tube 203 (see
The plurality of strips of the first material 300 may be evenly spaced along the full length of the proximal tube 203. The spacing of the plurality of strips of the first material 300 may be varied to adjust the flexibility and torqueability of the proximal tube 203. For example, the plurality of strips of the first material 300 may be spaced further apart in portions of the proximal tube 203 that require less flexibility (e.g., the end of the proximal tube 203 further from the sensor element 111) and/or spaced closer together in portions of the proximal tube 203 that require less stiffness (i.e., more flexibility).
In the embodiment of
In the embodiment of
In both of the embodiments of
In the embodiments illustrated in
Referring now to
In the examples discussed above, two materials are utilized to form the proximal tube 203. However, it should be understood that three or more materials may be used, provided that at least two of the materials have a different Young's modulus.
In the examples discussed above, each of the plurality of strips has a same width. However, it should be understood that strips of varying widths may be used along a length of the proximal tube.
It should be understood that even more variations of proximal tube shapes and opening alignments are possible. For example, the proximal tube 203 may include any number of cylindrical sections of different diameters, and may include any number of tapered sections or other sections to transition between the cylindrical sections, provided that the tube is mainly formed from the first material 300 and the cylindrical sections of decreased diameter or tapered sections are reinforced with the second material 310. The cross-section of the proximal tube 203 may be of any shape (e.g., rectangular, ovoid, spherical, etc.).
The proximal tube described in any of the embodiments may be used in place of the jacket 205 or other parts of a guide wire. In this case, distal openings and side openings placed through the wide wall of the proximal tube 203 may be located in any of the sections of the proximal tube 203 such that fluids flow into the guide wire at a distal end of the guide wire through the distal openings, and flows over the sensor element 111 (e.g., a pressure sensor) and through the side openings (or vice versa). The proximal tube described in any of the embodiments may be used with a guide wire without a core wire. The proximal tube described in any of the embodiments may also be used with a guide wire without a sensor or a guide wire with a braided portion.
The construction and arrangements of the sensor guide wire, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention. Features of one embodiment may be combined with a feature of another embodiment.
As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the form provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention.
The present application claims the benefit of U.S. Provisional Application No. 62/140,132, filed on Mar. 30, 2015, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62140132 | Mar 2015 | US |
