US20030013986A1 - Device for sensing temperature profile of a hollow body organ - Google Patents

Abstract

A device for sensing the temperature profile of a hollow body organ includes a catheter and hollow a guidewire carrying a thermal sensor. The hollow guidewire is configured to displace the thermal sensor radially relative to the catheter when unconstrained and can be rotated about the longitudinal axis of the catheter. When constrained within the catheter, the guidewire can be advanced to a region of interest in hollow body organ. The catheter can be withdrawn, leaving the guidewire in place in an expanded configuration wherein the thermal sensor contacts the inner wall of the hollow body organ. The guidewire is moveable to sense the temperature at multiple locations. The thermal sensor can be replaced with an electrode for sensing the impedance profile of the hollow body organ.

Description

TECHNICAL FIELD OF THE INVENTION
• This invention relates generally to invasive medical devices and more particularly to devices for sensing the temperature of the interior wall of a hollow body organ such as a blood vessel.[0001]
BACKGROUND OF THE INVENTION
• Acute ischemic syndromes involving arterial blood vessels, such as myocardial infarction, or heart attack, and stroke, frequently occur when atherosclerotic plaque ruptures, triggering the formation of blood clots, or thrombosis. Plaque that is inflamed is particularly unstable and vulnerable to disruption, with potentially devastating consequences. Therefore, there is a strong need to detect and locate this type of plaque so that treatment can be initiated before the plaque undergoes disruption and induces subsequent life-threatening clotting.[0002]
• Various procedures are known for detecting and locating plaque in a blood vessel. Angiography is one such procedure in which X-ray images of blood vessels are generated after a radiopaque dye is injected into the blood stream. This procedure is capable of locating plaque in an artery, but is not capable of revealing whether the plaque is the inflamed, unstable type.[0003]
• Researchers, acting on the theory that inflammation is a factor in the development of atherosclerosis, have discovered that local variations of temperature along arterial walls can indicate the presence of inflamed plaque. The temperature at the site of inflamation, i.e., the unstable plaque, is elevated relative to adjacent plaque-free arterial walls.[0004]
• Using a tiny thermal sensor at the end of a catheter, the temperature at multiple locations along an arterial wall were measured in people with and without atherosclerotic arteries. In people free of heart disease, the temperature was substantially homogeneous wherever measured: an average of 0.65 degrees F. above the oral temperature. In people with stable angina, the temperature of their plaques averaged 0.19 degrees F. above the temperature of their unaffected artery walls. The average temperature increase in people with unstable angina was 1.23 degrees F. The increase was 2.65 degrees F in people who had just suffered a heart attack. Furthermore, temperature variation at different points at the plaque site itself was found to be greatest in people who had just had a heart attack. There was progressively less variation in people with unstable angina and stable angina.[0005]
• The temperature heterogeneity discussed above can be exploited to detect and locate inflamed, unstable plaque through the use of cavity wall profiling apparatus. Typically, cavity wall profiling apparatus are comprised of temperature indicating probes such as thermocouples, thermistors, fluorescence lifetime measurement systems, resistance thermal devices and infrared measurement devices.[0006]
• One problem with conventional cavity wall profiling apparatus is that they usually exert an undue amount of force on the region of interest. If the region of interest cannot withstand these forces, it may be damaged. The inside walls of a healthy human artery are vulnerable to such damage. Furthermore, if inflamed, unstable plaque is present it may be ruptured by such forces.[0007]
• Another problem with conventional cavity wall profiling apparatus is that they can only measure the temperature at one specific location. In order to generate a map of the cavity temperature variation, one would need to move the temperature indicating probe from location to location. This can be very tedious, can increase the risk of damaging the vessel wall or rupturing vulnerable plaque, and may not resolve temporal characteristics of the profile with sufficient resolution. An array of probes could be employed but that could be very big and heavy.[0008]
SUMMARY OF THE INVENTION
• According to one aspect of the invention, a device is provided for sensing the temperature profile of a hollow body organ. The device includes a catheter, a hollow guidewire, and a temperature sensor disposed on or within the guidewire. The guidewire has a relaxed configuration externally of the catheter that is formed to provide contact with the wall of the hollow body organ. The guidewire also has a contracted configuration internally of the catheter and is of a lesser diameter than the catheter.[0009]
• According to another aspect of the invention, the device is used by contracting the guidewire elastically and constraining the guidewire within the catheter. The catheter and guidewire are advanced to a region of interest in a hollow body organ. The catheter is withdrawn to expose the distal portion of the guidewire in a relaxed configuration in contact with the hollow body organ. The guidewire is moved longitudinally and rotated, continuously or continually, to sense the temperature of the hollow body organ at multiple locations.[0010]
• Further aspects and advantages of the present invention are apparent from the following description of a preferred embodiment referring to the drawings.[0011]
BRIEF DESCRIPTION OF THE DRAWINGS
• In the drawings,[0012]
• FIG. 1 is a perspective view of a preferred embodiment of the present invention;[0013]
• FIG. 2 is a longitudinal sectional view of an arterial hollow body organ in which the embodiment of FIG. 1, also shown in longitudinal section, is deployed;[0014]
• FIG. 3 is a longitudinal sectional view of an arterial hollow body organ in which another preferred embodiment of the present invention, also shown in longitudinal section, is deployed;[0015]
• FIG. 4 is a perspective view of yet another preferred embodiment of the present invention;[0016]
• FIG. 5 is a perspective view, partially in section, of a further preferred embodiment of the present invention;[0017]
• FIG. 6 is a perspective view of yet another preferred embodiment of the present invention;[0018]
• FIG. 7 is a longitudinal sectional view of an arterial hollow body organ in which another preferred embodiment of the present invention, shown in perspective, is deployed;[0019]
• FIG. 8 is a perspective view of a further preferred embodiment of the present invention;[0020]
• FIG. 9 is a perspective view of another preferred embodiment of the present invention; and[0021]
• FIG. 10 is a longitudinal sectional view of an arterial hollow body organ in which yet another preferred embodiment of the present invention, shown in perspective, is deployed.[0022]
DESCRIPTION OF THE PREFERRED EMBODIMENT
• FIG. 1 shows a[0023]device10 for profiling the wall of a hollow body organ.Device10 includes alumened catheter12 having acentral lumen14, ahollow guidewire16 that defines a conduit comprising a tubular helix formed ofmetal wire18 or the like in the shape of a coil defining a central lumen (not shown), and athermal sensor20 disposed at the terminal end of the distal portion ofguidewire16. Conventional conductors or other signal carrying structures (not shown) are provided to convey signals from thethermal sensor20 alongguidewire16 and out of the proximal portion ofguidewire16 for connection to appropriate signal processing apparatus that converts the signals to a temperature indication.Thermal sensor20 can be a thermocouple, a thermistor, or an infrared radiation sensor, for example, and is secured by appropriate mechanical or adhesive means to the terminal end ofguidewire16.
• [0024]Hollow guidewire16 is made ofthin wire18 wound, for example around a mandrel, into small helical coils of desired diameter that lie tightly adjacent one another to form a hollow tube having a central passageway or lumen therethrough. Guidewire16 has an outer diameter somewhat less than the inner diameter ofcatheter12 to permitguidewire16 to slide freely within thelumen14 ofcatheter12. In addition,guidewire16, in its relaxed configuration, is shaped in the form of abend22 at the distal portion thereof, thebend22 being spaced from the terminal end ofguidewire16 at whichthermal sensor20 is disposed. Consequently,thermal sensor20 is displaced radially from thelongitudinal axis24 ofguidewire16 andcatheter12 whenguidewire16 is in the relaxed, bent configuration. Through external manipulation,guidewire16 in the relaxed, bent configuration can be made to rotate aboutaxis24, continuously or continually, depending on the response time for the sensor, thereby causingthermal sensor20 to traverse a circumferential or helical path aboutaxis24 while providing temperature information. Guidewire16 can be deformed elastically into a substantially straight configuration, i.e., withoutbend22, under force. When the force is removed,guidewire16 returns to the relaxed, bent configuration.
• Guidewire[0025]16 can be constructed of spring steel that can be deformed into a relatively straight configuration when withdrawn intocatheter12, but which springs back to its bent configuration when extruded fromcatheter12 and released from constraint. Another way is to constructguidewire16 of superelastic nitinol and take advantage of the martensitic transformation properties of nitinol. Guidewire16 can be inserted intocatheter12 in its straight form and kept cool within the catheter by the injection of cold saline throughcatheter12 and overguidewire16. Upon release ofguidewire16 into the bloodstream, it will warm up and change to its austenite memory shape based on the well-known martensitic transformation by application of heat and putting the material through its transformation temperature.
• Guidewire[0026]16 can also be made out of a composite such as a nitinol tube within the guidewire structure. In this fashion, the martensitic or superelastic properties of nitinol can be combined with the spring steel characteristics of the spring and lead to a desirable composition. Other suitable materials forguidewire16 include copper, constantin, chromel or alumel.
• FIG. 2 shows[0027]device10 deployed in a hollow body organ comprising anarterial blood vessel26 having anendothelium28 forming the inner wall thereof. Only the distal portion ofguidewire16 that extends beyondcatheter12 is shown.Electrical conductor32 extends throughlumen30 ofguidewire16.Conductor32 is electrically insulated from thecoils18 ofguidewire16 so thatguidewire16 comprises one conductor andconductor32 comprises another conductor or lead of thethermal sensor20 which can be a thermocouple or thermistor. The conductors convey signals from thethermal sensor20 to the proximal end ofguidewire16 for connection to appropriate signal processing apparatus that converts the received signals to a temperature indication.
• In use, the[0028]guidewire16 andthermal sensor20 of the preferred embodiment ofdevice10, as shown in FIGS. 1 and 2, are inserted into thelumen14 ofcatheter12 from the proximal end, thereby constrainingguidewire16 in a substantially straight configuration with thethermal sensor20 near the distal end ofcatheter12. Using conventional percutaneous insertion techniques, access to theblood vessel26 is obtained surgically.Catheter12, withguidewire16 andthermal sensor20 disposed within, is advanced through theblood vessel26 to the region of interest.
• [0029]Catheter12 is slowly withdrawn whileguidewire16 is secured against movement relative to the patent such that guidewire16 emerges from the distal end ofcatheter12 and reverts to the relaxed, bent configuration within theblood vessel26.Guidewire16 remains substantially fixed in the axial direction relative to theblood vessel26 ascatheter12 is withdrawn, with the re-formed bent distal portion ofguidewire16 springing gently radially outwardly into contact with thevessel wall28.
• With[0030]guidewire16 exposed andthermal sensor20 lying in contact with thewall28 ofblood vessel26, thethermal sensor20 senses the localized temperature of thevessel wall26 at the region where thethermal sensor20 is situated. By slowly withdrawingguidewire16 intocatheter12 while simultaneously rotatingguidewire16 about its longitudinal axis, thermal sensor25 can be made to traverse a helical path around theinner wall28 of theblood vessel26, permitting temperature measurements to be taken at intervals of different regions of thevessel wall28. Depending upon the response time ofthermal sensor20, rotation can be intermittent or continuous, as needed. By withdrawing and rotating theguidewire16 at constant rates, the location of thethermal sensor20 relative to the distal end of thecatheter12 can be determined as a function of time, so that a temperature profile of theblood vessel26 can be mapped, provided the response time of the thermal sensor is relatively short.
• Once the mapping is completed, the[0031]guidewire16 is withdrawn fully intocatheter12, re-sheathed and constrained in a substantially straight configuration.Catheter12 can then either be withdrawn from theblood vessel26 or repositioned to another region of interest within the hollow body organ for further mapping of the temperature profile at that region.
• FIG. 3 shows a second preferred embodiment of a[0032]device10′ for profiling the wall of a hollow body organ.Device10′ can be deployed in a hollow body organ in a manner similar to the embodiment ofdevice10 shown in FIGS. 1 and 2 and described above with respect to structure and use. Components ofdevice10′ that are similar in structure and function to corresponding components ofdevice10 of FIGS. 1 and 2 are designated by like primed numerals. The description ofdevice10 above applies also todevice10′ unless described otherwise below.
• [0033]Device10′ includes a secondthermal sensor36 disposed at the outside ofbend22′ and exposed for contact with theinner wall28′ ofvessel26′. A secondelectrical conductor38 is electrically insulated theconductor32′ and from thewire18′ ofguidewire16′ so that guidewire16′ comprises one conductor andconductor38 comprises another conductor of the thermocouple or thermistor ofthermal sensor36 for conveying signals from thethermal sensor36 to the proximal end ofguidewire16 for connection to appropriate signal processing apparatus that converts the signals to a temperature indication.Wire18′ ofguidewire16′ is a conductor common tothermal sensors20′ and36.
• [0034]Device10′ of FIG. 3 can be used in a manner substantially similar to the manner of use described above with respect todevice10 of FIGS. 1 and 2, except that thermistors20′ and38 simultaneously traverse intertwined helical paths in contact with theinner wall28′ ofhollow body organ26′. Consequently, the temperature profile of theinner wall28′ can be mapped more quickly because data can be gathered from different locations simultaneously.
• FIG. 4 shows yet another preferred embodiment of a[0035]device210 for profiling the wall temperature of a hollow body organ.Device210 can be deployed in a hollow body organ in the manner described above with respect to the embodiments ofdevices10 and10′ shown in FIGS. 1, 2 and3 and described above. Components ofdevice210 that are similar in structure and function to corresponding components ofdevice10 of FIGS. 1 and 2 are designated by like reference numerals in the 200 series but having the same last two digits. The description ofdevice10 above applies also todevice210 unless described otherwise below.
• [0036]Device210 of FIG. 4 includes onethermal sensor40 disposed at the outside of adogleg bend42 that is spaced distally frombend222 and from the terminal end ofguidewire216.Thermal sensor40 is exposed for contact with the inner wall228 of vessel226. An electrical conductor (not shown) is electrically insulated from thewire218 ofguidewire216 so thatguidewire216 comprises one conductor and the electrical conductor comprises another conductor of the thermocouple or thermistor ofthermal sensor40 for conveying signals from thethermal sensor40 to the proximal end ofguidewire216 for connection to appropriate signal processing apparatus that converts the signals to a temperature indication. Unlike the embodiments ofdevices10 and10′ of FIGS. 1, 2 and3,device210 includes only a thermistor at dog-leg bend42 and no thermistor at the terminal end ofguidewire216 or atbend222.
• [0037]Device210 of FIG. 4 can be used in a manner substantially similar to the manner of use described above with respect todevice10 of FIGS. 1 and 2.
• FIG. 5 shows a further preferred embodiment of a[0038]device310 for profiling the wall temperature of a hollow body organ.Device310 can be deployed in a hollow body organ in the manner described above with respect to the embodiments ofdevice10 shown in FIGS. 1 and 2 and described above. Components ofdevice310 that are similar in structure and function to corresponding components ofdevice10 of FIGS. 1 and 2 are designated by like reference numerals in the 300 series but having the same last two digits. The description ofdevice10 above applies also todevice310 unless described otherwise below.
• [0039]Device310 of FIG. 5, rather than having externally exposed thermal sensors as in the embodiments of FIGS. 1 through 4 above, includes athermal sensor50 disposed within the lumen330 ofhollow guidewire316 and in thermal contact with the coiledwire318 that comprisesguidewire316.Thermal sensor50 is located at adogleg bend52 that is spaced betweenbend322 and the distal end ofguidewire316.Guidewire316 also includesbend54 betweenbend52 and the distal end ofguidewire316.Bends322,52 and54 together cause the distal portion ofguidewire316 to assume the shape of a question mark when in a relaxed configuration. In such a configuration, bend52 and bend54 contact opposite sides of the inner wall of the hollow body organ. The spring nature ofguidewire316 urges bend52 in contact with the hollow body organ. Insulatedelectrical conductors56 and58 are operatively connected to the thermocouple or thermistor ofthermal sensor50 for conveying signals from thethermal sensor50 to the proximal end ofguidewire316 for connection to appropriate signal processing apparatus that converts the signals to a temperature indication.
• [0040]Device310 of FIG. 5 can be used in a manner substantially similar to the manner of use described above with respect todevice10 of FIGS. 1 and 2.
• FIG. 6 shows another embodiment of a[0041]device410 for profiling the wall temperature of a hollow body organ.Device410 is an alternative configuration of thedevice310 of FIG. 5, in which bend454 extends in a direction opposite to that ofbend54, such that the terminal end portion ofguidewire416 extends axially away fromcatheter412.Bend454 serves a purpose similar to that ofbend54 ofdevice310 of FIG. 5, i.e., to assure thatbend452, at whichthermal sensor450 is located, remains in contact with the inner wall of the hollow body organ when deployed therein.
• FIG. 7 shows yet another embodiment of the present invention.[0042]Temperature sensing device510 is carried byhollow guidewire516 which extends outwardly from the distal end ofcatheter512 and includesthermal sensor550, e.g., a thermistor at adogleg bend552 spaced frombend522 which is situated between the sensor-carryingbend552 and the distal end portion ofcatheter512. The distal end portion ofguide wire516 terminates in a generally crescent-shaped loop and is rotatable, continuously or continually, as desired, to sense the temperature of theendothelium528 lining the wall ofblood vessel526 in the vicinity ofplaque deposit592.
• FIG. 8 shows a further embodiment of a device[0043]610 for profiling the wall temperature of a hollow body organ. Device610 comprises another alternative configuration of thedevice310 of FIG. 5, in which guidewire616 is shaped as a plurality ofloops60 with a plurality ofthermal sensors62 located withinguidewire616 at each location along theloops60 that would contact the wall of the hollow body organ when disposed therein.
• FIG. 9 shows yet another embodiment of a[0044]device710 for profiling the wall temperature of a hollow body organ.Device710 includes alumened catheter712 and ahollow guidewire716. The inner surface oflumen730 ofguidewire716, at abend742 similar to bend42 ofdevice210 of FIG. 4, is lined with a layer ofblack paint70 which is in turn lined with athermochromic material72 that is sensitive to a change of temperature of theguidewire716. The color of thethermochromic material716 varies as a function of temperature.
• Disposed within[0045]lumen730 ofguidewire716, inwardly ofthermochromic material72, is anoptical probe74 including an illuminatingoptical fiber76 having a radially emittingdiffuser78 at the distal end thereof, and a sensingoptical fiber80 having a conically beveleddistal end82 for collecting light. An illuminating electromagnetic radiation source connected to the proximal end of illuminatingoptical fiber76 provides illuminating radiation that is guided byoptical fiber76 to the region of interest within the hollow body organ, and diffused radially bydiffuser78 to illuminate the interior oflumen730, particularlythermochromic material72. The illuminating radiation can be in the visible, infrared or ultraviolet portions of the spectrum. Radiation fromdiffuser78 is differentially absorbed and reflected bythermochromic material72, according to the color ofmaterial72 which is indicative of the temperature ofguidewire716 in contact with the wall of the hollow body organ in the region of interest.
• The light reflected from[0046]thermochromic material72, having wavelengths indicative of the color thereof, is collected bydistal end82 and directed toward the proximal end of sensingoptical fiber80. An appropriate optical reflectance spectrometry device connected to the proximal end of sensingoptical fiber80 generates an electrical signal indicative of the color, and therefore temperature, ofthermochromic material72.
• FIG. 10 shows yet another embodiment of a[0047]device810 suitable for profiling the impedance of the wall of a hollow body organ.Device810 includes acatheter812 within which is disposed aguidewire816 having a dog-leg bend in the distal portion thereof.Device810 is similar in configuration to the embodiment ofdevice210 of FIG. 4, and like components are indicated by like reference numerals in the 800 series but having the same last two digits. Unlikedevice210 of FIG. 4,device810 does not employ thermal sensing, but rather employs impedance sensing for profiling the wall of a hollow body organ. Anelectrode90 at the outside of the dog-leg bend ofguidewire816 is in electrical contact withguidewire816 and in electrical contact with theinner wall828 of thehollow body organ826.Guidewire816 comprises a conductor operatively connected to an external impedance measuring device that has a ground terminal electrically connected to the body in which the hollow body organ is located. A small electrical current is applied viaguidewire816 andelectrode90 to theinner wall828 at the region of contact therebetween. The impedance of the electrical path through the body, including through the region of interest in thehollow body organ826, can be measured and recorded. By moving guidewire816 relative to thehollow body organ826 as described above with respect to other embodiments, the impedance of the wall of thevessel826 can be mapped. Any change of impedance along thewall828 indicates the presence of an anomaly in the wall, such as aplaque92.
• Although the present invention has been described in detail in terms of preferred embodiments, no limitation on the scope of the invention is intended. The scope of the subject matter in which an exclusive right is claimed is defined in the appended claims.[0048]

Claims (19)

I claim:

1. A device for sensing the temperature profile of a hollow body organ, comprising:

a catheter having a longitudinal axis;

a hollow guidewire being disposable in a relaxed configuration externally of the catheter, and in a contracted configuration internally of the catheter; a temperature sensor connected to the guidewire and moveable therewith, the temperature sensor being displaced laterally relative to the longitudinal axis of the catheter when the guidewire is in the relaxed configuration.

2. The device ofclaim 1, wherein the hollow guidewire comprises a tubular helix.

3. The device ofclaim 1, wherein the hollow guidewire comprises a material having martensitic transformation properties.

4. The device ofclaim 3, wherein the hollow guidewire comprises nitinol.

5. The device ofclaim 1, wherein the hollow guidewire comprises an elastic material.

6. The device ofclaim 5, wherein the hollow guidewire comprises spring steel.

7. The device ofclaim 1, wherein the temperature sensor is a thermocouple.

8. The device ofclaim 7, wherein the temperature sensor comprises one leg of the thermocouple and the guidewire comprises another leg of the thermocouple.

9. The device ofclaim 1, wherein the temperature sensor is a thermistor.

10. The device ofclaim 1, wherein the temperature sensor comprises a thermochromic material.

11. The device ofclaim 10, wherein the thermochromic material is in thermal contact with the lumen of the hollow guidewire.

12. The device ofclaim 11, wherein the temperature sensor further includes an optical probe for sensing the color of the thermochromic material.

13. The device ofclaim 12, wherein the optical probe includes an illumination device for illuminating a region of interest of the hollow guidewire.

14. The device ofclaim 13, wherein the optical probe includes a sensing device for sensing reflected radiation from the thermochromic material.

15. The device ofclaim 14, wherein the reflected radiation is in the visible spectrum.

16. The device ofclaim 14, wherein the reflected radiation is in the infrared spectrum.

17. The device ofclaim 14, wherein the reflected radiation is in the ultraviolet spectrum.

18. The device ofclaim 1 wherein the temperature sensor is adapted for rotational displacement about the longitudinal axis of the catheter while in contact with the hollow body organ.

19. A device for sensing the impedance profile of a hollow body organ, comprising:

a catheter having a longitudinal axis;

a hollow guidewire being disposable in a relaxed configuration externally of the catheter, and in a contracted configuration internally of the catheter; an electrode connected to the guidewire and moveable therewith, the electrode being displaced laterally relative to the longitudinal axis when the guidewire is in the relaxed configuration.

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