Abstract:
Apparatus and methods are described including inserting a catheter into a subject&#39;s body via a vein of the subject&#39;s groin. The catheter is advanced distally such that a distal end of the catheter is disposed inside the subject&#39;s renal vein. Respective stabilizing portions of the catheter stabilize the catheter by being in contact with inner walls of, respectively, an iliac vein of the subject, and a vena cava of the subject. Subsequently, a medical device is deployed inside the renal vein by retracting the distal end of the catheter, such that the distal end of the catheter is in a retracted state, in which the respective stabilizing portions of the catheter still stabilize the catheter by being in contact with the inner walls of, respectively, the subject&#39;s iliac vein and the subject&#39;s vena cava. Other applications are also described.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application 61/914,470 to Tuval, filed Dec. 11, 2013, entitled “Curved catheter.” 
     The present application is related to: 
     U.S. patent application Ser. No. 14/405,144 to Tuval (published as US 2015-0164662), which is the US National Phase of International Patent Application PCT/IL2013/050495 to Tuval (published as WO 13/183060), filed Jun. 6, 2013, entitled “Prosthetic renal valve,” which claims priority from U.S. Provisional Patent Application 61/656,244 to Tuval, filed Jun. 6, 2012, entitled “Prosthetic renal valve;” and 
     International Patent Application PCT/IL2014/050289 to Schwammenthal (published as WO 14/141284), filed Mar. 13, 2014, entitled “Renal pump,” which claims priority from (a) U.S. Provisional Patent Application 61/779,803 to Schwammenthal, filed Mar. 13, 2013, entitled “Renal pump,” and (b) U.S. Provisional Patent Application 61/914,475 to Schwammenthal, filed Dec. 11, 2013, entitled “Renal pump.” 
     All of the above-listed applications are incorporated herein by reference. 
    
    
     FIELD OF EMBODIMENTS OF THE INVENTION 
     Some applications of the present invention generally relate to medical apparatus. Specifically, some applications of the present invention relate to apparatus and methods associated with placing a medical device in one or more of a subject&#39;s renal vessels. 
     BACKGROUND 
     Catheters are medical tools that are used for cardiovascular, urological, gastrointestinal, neurovascular, and ophthalmic applications. Catheters may be inserted blood vessels, such as to provide access to the blood vessel to medical devices or tools. Catheters are typically flexible tubes that are inserted into a patient&#39;s body via an access port and advanced, over a guidewire, to a desired location inside the subject&#39;s body. 
     SUMMARY OF EMBODIMENTS 
     In accordance with some applications of the present invention, a catheter is placed into a renal vessel of a subject by being inserted into the subject&#39;s vasculature via a vessel of the subject&#39;s groin. The catheter defines a continuous tube that defines a lumen therethrough, and a medical device is inserted into the subject&#39;s body via the catheter lumen. The continuous tube defined by the catheter typically defines at least a first portion, a second portion, a third portion, a fourth portion, and a fifth portion thereof, each of the portions of the catheter typically defining a shape having given characteristics. 
     The catheter is typically shaped such that both (a) when the catheter is placed into a renal vessel that is ipsilateral with respect to the vessel of the groin via which the catheter is inserted, and (b) when the catheter is placed into a renal vessel that is contralateral with respect to the vessel of the groin via which the catheter is inserted, the catheter is stabilized by portions of the catheter contacting inner walls of the blood vessels of the subject at at least two points. Typically, one of the portions of the catheter stabilizes the catheter by contacting an inner wall of an iliac vessel of the subject, and another one of the portions of the catheter stabilizes the catheter by contacting an inner wall of the vena cava, or the aorta of the subject. Further typically, the catheter is stabilized by portions of the catheter contacting inner walls of the blood vessels of the subject at the at least two points (a) before the catheter is retracted such as to release the device from the distal end of the catheter, and (b) subsequent to the catheter having been retracted, such as to release the device from the distal end of the catheter. 
     There is therefore provided, in accordance with some applications of the present invention, apparatus including: 
     a medical device that is configured to be inserted into a body of a subject; and 
     a catheter that defines a continuous tube that defines a lumen therethrough, the medical device being configured to be inserted into the subject&#39;s body via the catheter, the continuous tube including at least first, second, third, fourth, and fifth portions thereof, 
     the first portion being disposed at a first end of the catheter and being shaped, when the catheter is in a non-constrained configuration, to define a cylindrical portion of the tube that defines a generally straight central longitudinal axis; 
     the second portion being disposed adjacent to the first portion and being shaped, when the catheter is in the non-constrained configuration, to define a curved cylindrical portion of the tube, a curvature of the second portion being such that a central longitudinal axis of the second portion defines a curve that is concave in a given direction, and that curves outwardly away from the central longitudinal axis of the first portion; 
     the third portion being disposed between the second and the fourth portions and being shaped, when the catheter is in the non-constrained configuration, to define a curved cylindrical portion of the tube, a curvature of the third portion being such that a central longitudinal axis of the third portion defines a curve that is convex in the given direction, and that curves inwardly toward the central longitudinal axis of the first portion, such that the central longitudinal axis of the third portion meets the central longitudinal axis of the first portion, 
     the fourth portion being disposed between the third and the fifth portions of the tube, and being shaped, when the catheter is in the non-constrained configuration, to define a curved cylindrical tube, a curvature of the fourth portion being such that a central longitudinal axis of the fourth portion defines a curve that is concave in the given direction, and that curves away from the central longitudinal axis of the first portion, 
     the fifth portion being disposed at a second end of the catheter the fifth portion being shaped, when the catheter is in the non-constrained configuration, to define a curved cylindrical tube, a curvature of the fifth portion being such that a central longitudinal axis of the fifth portion defines a curve that is concave in the given direction, and that curves inwardly toward the central longitudinal axis of the first portion. 
     For some applications, the continuous tube defined by the catheter further includes a sixth portion disposed between the second and third portions of the tube, the sixth portion of the tube defining a cylindrical portion of the tube that defines a generally straight central longitudinal axis, when the catheter is in the non-constrained configuration. 
     For some applications, a flexibility of at least a distal tip of the fifth portion is greater than a flexibility of each of the first, second, third, and fourth portions. 
     For some applications, at least a tip of the fifth portion is atraumatic. 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature of the second portion is greater than 50 mm. For some applications, when the catheter is in the non-constrained configuration, the radius of curvature of the second portion is less than 250 mm. 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature of the third portion is greater than 20 mm. For some applications, when the catheter is in the non-constrained configuration, the radius of curvature of the third portion is less than 100 mm. 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature of the fourth portion is greater than 10 mm. For some applications, when the catheter is in the non-constrained configuration, the radius of curvature of the fourth portion is less than 80 mm. 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature of the fifth portion is greater than 50 mm. For some applications, when the catheter is in the non-constrained configuration, the radius of curvature of the fifth portion is less than 250 mm. 
     For some applications, when the catheter is in the non-constrained configuration, a ratio of a radius of curvature of the second portion to a radius of curvature of the third portion is greater than 1.5:1. For some applications, when the catheter is in the non-constrained configuration, the ratio of the radius of curvature of the second portion to the radius of curvature of the third portion is less than 4:1. 
     For some applications, when the catheter is in the non-constrained configuration, a length of the second portion of the tube, measured along the longitudinal axis of the second portion, is at least twice the length of the medical device. For some applications, the length of the second portion of the tube is at least 3 times the length of the medical device. 
     For some applications, a length of the third portion of the tube, measured along the longitudinal axis of the third portion, is at least twice the length of the medical device. For some applications, the length of the third portion of the tube is at least 3 times the length of the medical device. 
     For some applications, when the catheter is in the non-constrained configuration a length of the second portion, measured along the longitudinal axis of the second portion, is greater than 20 mm. For some applications, when the catheter is in the non-constrained configuration, the length of the second portion is less than 50 mm. 
     For some applications, when the catheter is in the non-constrained configuration, a length of the third portion, measured along the longitudinal axis of the third portion, is greater than 40 mm. For some applications, when the catheter is in the non-constrained configuration, the length of the third portion is less than 100 mm. 
     For some applications, when the catheter is in the non-constrained configuration, a length of the fourth portion, measured along the longitudinal axis of the fourth portion, is greater than 20 mm. For some applications, when the catheter is in the non-constrained configuration, the length of the fourth portion is less than 50 mm. 
     For some applications, when the catheter is in the non-constrained configuration, a length of the fifth portion, measured along the longitudinal axis of the fifth portion, is greater than 20 mm. For some applications, when the catheter is in the non-constrained configuration, the length of the fifth portion is less than 50 mm. 
     For some applications: 
     the catheter is configured to be:
         inserted into the subject&#39;s body via a blood vessel of a groin of the subject, and   advanced distally such that the fifth portion of the catheter is inserted into a renal vessel that is contralateral to the blood vessel of the subject&#39;s groin; and       

     the medical device is configured to be deployed inside the contralateral renal vessel by the catheter being retracted proximally, subsequent to insertion of the fifth portion of the catheter into the contralateral renal vessel. 
     For some applications, when the fifth portion of the catheter is disposed inside the renal vessel and prior to deploying the medical device by the catheter being retracted proximally, the second portion is configured to stabilize the catheter by contacting an inner wall of an iliac vessel of the subject. 
     For some applications, when the fifth portion of the catheter is disposed inside the renal vessel, and prior to deploying the medical device by the catheter being retracted proximally, the third portion is configured to stabilize the catheter by contacting an inner wall of a vessel of the subject selected from the group consisting of: a vena cava of the subject, and an aorta of the subject. 
     For some applications, when the fifth portion of the catheter is disposed inside the renal vessel, and prior to deploying the medical device by the catheter being retracted proximally, the fourth portion is configured to stabilize the catheter by contacting an inner wall of the renal vessel. 
     For some applications, subsequent to deployment of the device in the contralateral renal vessel by the catheter having been retracted proximally, the second portion is configured to stabilize the catheter by contacting an inner wall of an iliac vessel of the subject. 
     For some applications, subsequent to deployment of the device in the contralateral renal vessel by the catheter having been retracted proximally, the third portion is configured to stabilize the catheter by contacting an inner wall of a vessel of the subject selected from the group consisting of: a vena cava of the subject, and an aorta of the subject. 
     For some applications, subsequent to deployment of the device in the contralateral renal vessel by the catheter having been retracted proximally, the fourth portion is configured to stabilize the catheter by contacting an inner wall of the renal vessel. 
     For some applications: 
     the catheter is configured to be:
         inserted into the subject&#39;s body via a blood vessel of a groin of the subject, and   advanced distally such that the fifth portion of the catheter is inserted into a renal vessel that is ipsilateral to the blood vessel of the subject&#39;s groin; and       

     the medical device is configured to be deployed inside the contralateral renal vessel by the catheter being retracted proximally, subsequent to insertion of the fifth portion of the catheter into the ipsilateral renal vessel. 
     For some applications, when the fifth portion of the catheter is disposed inside the renal vessel, and prior to deploying the medical device by the catheter being retracted proximally, the second portion is configured to stabilize the catheter by contacting an inner wall of an iliac vessel of the subject. 
     For some applications, when the fifth portion of the catheter is disposed inside the renal vessel, and prior to deploying the medical device by the catheter being retracted proximally, the third portion is configured to stabilize the catheter by contacting an inner wall of a vessel of the subject selected from the group consisting of: a vena cava of the subject, and an aorta of the subject. 
     For some applications, when the fifth portion of the catheter is disposed inside the renal vessel, and prior to deploying the medical device by the catheter being retracted proximally, the fourth portion is configured to stabilize the catheter by contacting an inner wall of the renal vessel. 
     For some applications, subsequent to deployment of the device in the ipsilateral renal vessel by the catheter having been retracted proximally, the second portion is configured to stabilize the catheter by contacting an inner wall of an iliac vessel of the subject. 
     For some applications, subsequent to deployment of the device in the ipsilateral renal vessel by the catheter having been retracted proximally, the third portion is configured to stabilize the catheter by contacting an inner wall of a vessel of the subject selected from the group consisting of: a vena cava of the subject, and an aorta of the subject. 
     For some applications, subsequent to deployment of the device in the ipsilateral renal vessel by the catheter having been retracted proximally, the fourth portion is configured to stabilize the catheter by contacting an inner wall of the renal vessel. 
     For some applications, in the non-constrained configuration of the catheter, the catheter defines a span in a direction that is perpendicular to the longitudinal axis of the first portion that is greater than 20 mm. 
     For some applications, in the non-constrained configuration of the catheter, the catheter defines a span in the direction that is perpendicular to the longitudinal axis of the first portion that is greater than 40 mm. 
     For some applications, in the non-constrained configuration of the catheter, the catheter defines a span in the direction that is perpendicular to the longitudinal axis of the first portion that is less than 70 mm. 
     For some applications, in the non-constrained configuration of the catheter, the catheter defines a span in the direction that is perpendicular to the longitudinal axis of the first portion that is less than 60 mm. 
     For some applications, in the non-constrained configuration of the catheter, the catheter defines a length measured along the longitudinal axis of the first portion, from a location at which the longitudinal axis of the second portion begins to curve away from the longitudinal axis of the first portion until the longitudinal axis of the third portion meets the longitudinal axis of the first portion that is greater than 80 mm. For some applications, the length is greater than 100 mm. For some applications, the length is less than 250 mm. For some applications, the length is less than 150 mm. 
     For some applications, the medical device includes a radially-expandable impeller disposed inside a radially-expandable cage. 
     For some applications, a length of cage, measured along a longitudinal axis of the cage, when the cage is in a radially expanded configuration, is between 17 mm and 26 mm. 
     There is further provided, in accordance with some applications of the present invention, a method including: 
     inserting a catheter into a body of a subject via a vein of a groin of the subject, and 
     advancing the catheter distally such that:
         a distal end of the catheter is disposed inside a renal vein of the subject, and   respective stabilizing portions of the catheter stabilize the catheter by being in contact with inner walls of, respectively, an iliac vein of the subject, and a vena cava of the subject; and       

     subsequently, deploying a medical device inside the renal vein by retracting the distal end of the catheter, such that the distal end of the catheter is in a retracted state, in which the respective stabilizing portions of the catheter still stabilize the catheter by being in contact with the inner walls of, respectively, the subject&#39;s iliac vein and the subject&#39;s vena cava. 
     For some applications, advancing the catheter distally includes advancing the catheter distally such that a further stabilizing portion of the catheter stabilizes the catheter by being in contact with an inner wall of the renal vein. 
     For some applications, retracting the distal end of the catheter includes retracting the distal end of the catheter, such that while the distal end of the catheter is in its retracted state, a further stabilizing portion of the catheter stabilizes the catheter by being in contact with an inner wall of the renal vein. 
     For some applications, advancing the catheter distally such that the distal end of the catheter is disposed inside the subject&#39;s renal vein includes advancing the catheter distally such that the distal end of the catheter is disposed inside a renal vein of the subject that is contralateral to the vein of the subject&#39;s groin via which the catheter is inserted. 
     For some applications, advancing the catheter distally such that the distal end of the catheter is disposed inside the subject&#39;s renal vein includes advancing the catheter distally such that the distal end of the catheter is disposed inside a renal vein of the subject that is ipsilateral to the vein of the subject&#39;s groin via which the catheter is inserted. 
     For some applications, the method further includes operating the medical device, inside the renal vein, while the catheter is disposed inside a body of the subject in its retracted state, such that the catheter supports the medical device during its operation. 
     For some applications, deploying the device includes deploying a radially-expandable impeller that is disposed inside a radially-expandable impeller cage, and operating the medical device includes rotating the impeller. 
     There is further provided, in accordance with some applications of the present invention, a method including: 
     inserting a catheter into a body of a subject via an artery of a groin of the subject, and 
     advancing the catheter distally such that:
         a distal end of the catheter is disposed inside a renal artery of the subject, and   respective stabilizing portions of the catheter stabilize the catheter by being in contact with inner walls of, respectively, an iliac artery of the subject, and an aorta of the subject; and       

     subsequently, deploying a medical device inside the renal artery by retracting the distal end of the catheter, such that the distal end of the catheter is in a retracted state, in which the respective stabilizing portions of the catheter still stabilize the catheter by being in contact with the inner walls of, respectively, the subject&#39;s iliac artery and the subject&#39;s aorta. 
     For some applications, advancing the catheter distally includes advancing the catheter distally such that a further stabilizing portion of the catheter stabilizes the catheter by being in contact with an inner wall of the renal artery. 
     For some applications, retracting the distal end of the catheter includes retracting the distal end of the catheter, such that while the distal end of the catheter is in its retracted state, a further stabilizing portion of the catheter stabilizes the catheter by being in contact with an inner wall of the renal artery. 
     For some applications, advancing the catheter distally such that the distal end of the catheter is disposed inside the subject&#39;s renal artery includes advancing the catheter distally such that the distal end of the catheter is disposed inside a renal artery of the subject that is contralateral to the artery of the subject&#39;s groin via which the catheter is inserted. 
     For some applications, advancing the catheter distally such that the distal end of the catheter is disposed inside the subject&#39;s renal artery includes advancing the catheter distally such that the distal end of the catheter is disposed inside a renal artery of the subject that is ipsilateral to the artery of the subject&#39;s groin via which the catheter is inserted. 
     For some applications, the method further includes operating the medical device, inside the renal artery, while the catheter is disposed inside a body of the subject in its retracted state, such that the catheter supports the medical device during its operation. 
     For some applications, deploying the device includes deploying a radially-expandable impeller that is disposed inside a radially-expandable impeller cage, and operating the medical device includes rotating the impeller. 
     The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a catheter, in accordance with some applications of the present invention; 
         FIGS. 2A-B  are schematic illustrations of the catheter being inserted via a vein of a subject&#39;s groin, a distal end of the catheter being placed into a renal vein of the subject that is ipsilateral to the vein of the groin, in accordance with some applications of the present invention; 
         FIGS. 2C-D  are schematic illustrations of portions of the catheter, respectively before and after a medical device has been deployed inside the ipsilateral renal vein, via the distal end of the catheter, in accordance with some applications of the present invention; 
         FIG. 2E  is a schematic illustration of a catheter that has been inserted, via an artery of a subject&#39;s groin, such that a distal end of the catheter is placed into a renal artery of the subject that is ipsilateral to the artery of the groin, in accordance with some applications of the present invention; 
         FIGS. 3A-B  are schematic illustrations of a catheter being inserted via a vein of a subject&#39;s groin, a distal end of the catheter being placed into a renal vein of the subject that is contralateral to the vein of the groin, in accordance with some applications of the present invention; 
         FIGS. 3C-D  are schematic illustrations of portions of the catheter, respectively before and after a medical device has been deployed inside the contralateral renal vein, via the distal end of the catheter, in accordance with some applications of the present invention; and 
         FIG. 3E  is a schematic illustration of a catheter that has been inserted, via an artery of a subject&#39;s groin, such that a distal end of the catheter is placed into a renal artery of the subject that is contralateral to the artery of the groin, in accordance with some applications of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Reference is now made to  FIG. 1 , which is a schematic illustration of a catheter  20 , in accordance with some applications of the present invention. Catheter  20  defines a continuous tube that defines a lumen therethrough. A medical device  50  ( FIG. 2D ) is typically inserted into the subject&#39;s body via the catheter lumen. The continuous tube defined by catheter  20  typically defines at least a first portion  22 , a second portion  24 , a third portion  26 , a fourth portion  28 , and a fifth portion  30  thereof. For some applications, the continuous tube additionally defines a sixth portion  32  having characteristics as described hereinbelow. Alternatively or additionally, the continuous tube defines one or more different additional portions. 
     Typically, in a non-constrained configuration of the catheter (i.e., in the absence of any force being applied to the catheter), each of the portions of the catheter defines a shape having characteristics as described hereinbelow. For some applications, the catheter is made from a polymer, a polymer that is reinforced with a braided or coiled metal or alloy, a metal, and/or an alloy (such as nitinol). The catheter is shape set (e.g., by shape setting the catheter in a mold, by steam shaping, and/or by mechanical shape setting), such that the shape of each of the portions has the described characteristics. 
     First portion  22  of catheter  20  is disposed at a first, proximal end of the catheter. When the catheter is in the non-constrained configuration, the first portion typically defines a cylindrical portion of the tube that defines a generally straight central longitudinal axis  23 . 
     As used in the present application, including in the claims, a “central longitudinal axis” of a structure is the set of all centroids of cross-sectional sections of the structure along the structure. Thus the cross-sectional sections are locally perpendicular to the central longitudinal axis, which runs along the structure. (If the structure is circular in cross-section, the centroids correspond with the centers of the circular cross-sectional sections.) 
     Second portion  24  is typically disposed adjacent to the first portion. When the catheter is in the non-constrained configuration, the second portion is typically shaped to define a curved cylindrical portion of the tube. The curvature of the second portion is such that a central longitudinal axis  25  of the second portion defines a curve that is concave in a given direction, and that curves outwardly away from the central longitudinal axis of the first portion. For example, as shown in  FIG. 1  the curve is concave in the direction in which arrow  34  is pointing. 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature R2 of second portion  24  is greater than 50 mm, and/or less than 250 mm, e.g., 50 mm-250 mm. Typically, a length of the second portion of the tube (measured along central longitudinal axis  25  of the second portion) is at least twice the length (e.g., at least 3 times the length) of medical device  50  ( FIG. 2D ), which is configured to be placed inside the subject&#39;s body, via the catheter. For some applications, when the catheter is in the non-constrained configuration, the length of the second portion of the tube is greater than 20 mm, and/or less than 50 mm, e.g., 20 mm-50 mm. 
     Third portion  26  of catheter  20  is disposed between the second and the fourth portions. When the catheter is in the non-constrained configuration, the third portion is shaped to define a curved cylindrical portion of the tube. The curvature of the third portion is typically such that a central longitudinal axis  27  of the third portion defines a curve that is convex in the given direction (in the example shown, in the direction of arrow  34 ), and that curves inwardly toward the central longitudinal axis of the first portion. Further typically, the curvature of the third portion is such that the central longitudinal axis of the third portion meets central longitudinal axis  23  of the first portion. For example, as shown in  FIG. 1 , central longitudinal axis  27  of the third portion meets central longitudinal axis  23  of the first portion at point  36 . 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature R3 of third portion  26  is greater than 20 mm, and/or less than 100 mm, e.g., 20 mm-100 mm. For some applications, when the catheter is in the non-constrained configuration, a ratio of radius of curvature R2 of the second portion to radius of curvature R3 of the third portion is greater than 1.5:1, and/or less than 4:1, e.g., 1.5:1-4:1. 
     Typically, a length of the third portion of the tube (measured along central longitudinal axis  27  of the third portion) is at least twice the length (e.g., at least 3 times the length) of medical device  50  ( FIG. 2D ), which is configured to be placed inside the subject&#39;s body, via catheter  20 . For some applications, when the catheter is in the non-constrained configuration, the length of the third portion of the tube is greater than 40 mm, and/or less than 100 mm, e.g., 40 mm-100 mm. 
     Fourth portion  28  is disposed between the third and the fifth portions of the tube. When the catheter is in the non-constrained configuration, the fourth portion typically defines a curved cylindrical tube. The curvature of the fourth portion is typically such that a central longitudinal axis  29  of the fourth portion defines a curve that is concave in the given direction (in the example shown, in the direction of arrow  34 ), and that curves away from central longitudinal axis  23  of first portion  22 . 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature R4 of fourth portion  28  is greater than 10 mm, and/or less than 80 mm, e.g., 10 mm-80 mm. For some applications, when the catheter is in the non-constrained configuration, a length of the fourth portion of the tube (measured along central longitudinal axis  29  of the fourth portion) is greater than 20 mm, and/or less than 50 mm, e.g., 20 mm-50 mm. 
     Fifth portion  30  is disposed at a second end of the catheter. When the catheter is in the non-constrained configuration, the fifth portion is typically shaped to define a curved cylindrical tube. The curvature of the fifth portion is typically such that a central longitudinal axis  31  of the fifth portion defines a curve that is concave in the given direction (in the example shown, in the direction of arrow  34 ), and that curves inwardly toward central longitudinal axis  23  of first portion  22 . For some applications, at least a distal tip  37  of the fifth portion of the continuous tube defined by the catheter is greater than a flexibility of each of the first, second, third, and fourth portions. 
     For some applications, when the catheter is in the non-constrained configuration, a radius of curvature R5 of fifth portion  30  is greater than 50 mm, and/or less than 250 mm, e.g., 50 mm-250 mm. For some applications, when the catheter is in the non-constrained configuration, a length of the fifth portion of the tube (measured along central longitudinal axis  31  of the fifth portion) is greater than 20 mm, and/or less than 50 mm, e.g., 20 mm-50 mm. 
     As described hereinabove, for some applications, the tube defined by catheter  20  further defines a sixth portion  32 , disposed between the second and third portions of the tube. For some applications, when the catheter is in the non-constrained configuration, the sixth portion of the tube defines a cylindrical portion of the tube that defines a generally straight central longitudinal axis. For some applications, a length of the sixth portion (measured along the central longitudinal axis of the sixth portion) is greater than 10 mm, and/or less than 100 mm, e.g., 10 mm-100 mm. 
     Typically, in the non-constrained configuration of the catheter (i.e., in the absence of any force being applied to the catheter), the catheter defines a span SP in a direction that is perpendicular to longitudinal axis  23  of first portion  22  that is greater than 20 mm (e.g., greater than 40 mm), and/or less than 70 mm (e.g., less than 60 mm), e.g., 20 mm-70 mm (e.g., 40 mm to 60 mm). Further typically, in the non-constrained configuration of the catheter (i.e., in the absence of any force being applied to the catheter), the catheter defines a length L1, measured along longitudinal axis  23  of first portion  22 , from where the second catheter begins to curve until point  36  at which longitudinal axis  27  of third portion  26  meets longitudinal axis  23  of first portion  22  that is greater than 80 mm (e.g., greater than 100 mm), and/or less than 250 mm (e.g., less than 150 mm), e.g., 80 mm-250 mm (e.g., 100 mm to 150 mm). Typically, when the fifth portion of the catheter is placed inside a renal vessel of the subject, as described hereinbelow, length L1 corresponds to the distance from where the second portion of the catheter contacts the wall of an iliac vessel, until the renal vessel. 
     Reference is now made to  FIGS. 2A-B , which are schematic illustrations of catheter  20  being inserted into the subject&#39;s vasculature via a vein of a subject&#39;s groin (right femoral vein  40 , in the example shown). A distal end of the catheter is advanced into a renal vein of the subject that is ipsilateral to the vein of the groin (e.g., right renal vein  42 , in the example shown), in accordance with some applications of the present invention. For some applications, in order to insert the distal end of the catheter into the renal vein, the distal end of the catheter is first placed into the subject&#39;s vena cava  44 , downstream of (i.e., distal to) the renal vein. The catheter is inserted such that due to the curvature of the catheter, the distal tip of the catheter pushes against the inner wall of the vena cava on the ipsilateral side of the vena cava, as shown in  FIG. 2A . The catheter is then retracted proximally, such that when the distal tip of the catheter passes the opening to the renal vein, the distal tip of the catheter enters the renal vein. When the distal tip has entered the renal vein, the catheter is then advanced, such that the distal tip of the catheter is disposed inside the renal vein in the vicinity of the subject&#39;s kidney  46 , as shown in  FIG. 2B . 
     As described hereinabove, typically, at least distal tip  37  of the fifth portion of the continuous tube defined by catheter  20  (i.e. the distal tip of the catheter) is greater than a flexibility of each of the first, second, third, and fourth portions of the catheter. For some applications, the distal tip of the fifth portion (i.e. the distal tip of the catheter) is thus configured to be atraumatic. For some applications, the tip being atraumatic reduces a likelihood of an injury being caused to the inner wall of the vena cava, during the insertion of the catheter, relative to if the distal tip of the catheter were not atraumatic. For some applications, the distal tip of the catheter is made of a more flexible material (e.g., a more flexible polymer) than that of the remainder of the catheter, and/or a reinforcing material (e.g., a braided or coiled metal or alloy) that reinforces the remainder of the catheter is not present in the distal tip of the catheter, or is made to be more flexible in the distal tip of the catheter. 
     For some applications, a control unit  48  disposed outside the subject&#39;s body is coupled to medical device  50  ( FIG. 2D ), and is configured to control the functioning of the medical device. For example, the medical device may be a pump, and the control unit may control the functioning of the pump, by rotating a portion of the pump via a motor  49 . Typically, the control unit includes any type of processor (such as a computer processor) configured to execute the actions described herein. Further typically, a user interacts with the control unit via a user interface  51 , which typically includes any type of user interface configured to receive inputs from a user and/or to provide outputs to the user (including but not limited to keyboards, displays, pointing devices, etc.). 
     Reference is now made to  FIGS. 2C-D , which are schematic illustrations of portions of catheter  20 , respectively before and after a medical device  50  has been deployed inside renal vein  42 , via the distal end of the catheter, in accordance with some applications of the present invention. Typically, medical device  50  is self expandable. For example, medical device  50  may be a self expandable valve, a self expandable stent, and/or a self-expandable pump. For some applications, medical device  50  is a blood pump that includes a radially-expandable impeller disposed inside a radially-expandable impeller cage, e.g., as described with reference to  12 Ai- 22 Cii of WO 14/141284 to Schwammenthal, which is incorporated herein by reference. For such applications, control unit  48  typically controls the functioning of the pump, by rotating the impeller of the pump via motor  49 . Typically, the medical device is deployed inside the renal vein by retracting the distal end of catheter  20 , such that the medical device self expands, as shown in the transition from  FIG. 2C  to  FIG. 2D . 
     Typically, during deployment of medical device  50  inside renal vein (i.e., during retraction of catheter  20  from the position shown in  FIG. 2C  to the position shown in  FIG. 2D ), second portion  24  of the catheter is configured to stabilize the catheter by contacting an inner wall of an iliac vein  52  of the subject. Further typically, subsequent to the deployment of the medical device inside the renal vein, second portion  24  of the catheter is configured to stabilize the catheter by contacting the inner wall of iliac vein  52 , as shown in  FIG. 2D . In this manner, second portion  24  acts as a stabilizing portion of the catheter. For some applications, the device is temporarily placed inside the subject&#39;s renal vein, in order to provide an acute treatment to the subject. The catheter remains in place inside the subject&#39;s vasculature during the treatment, and the second portion of the catheter provides stabilization to the catheter by contacting the inner wall of iliac vein  52 , as shown in  FIG. 2D . Subsequent to the treatment being terminated, device  50  is withdrawn from the subject&#39;s renal vein via the catheter. 
     As described hereinabove, the length of second portion  24  of the tube defined by catheter  20  is typically at least twice the length (e.g., at least 3 times the length) of medical device  50 . Typically, the second portion is thus configured to contact the inner wall of iliac vein  52  both (a) before the catheter has been retracted such as to release the device from the distal end of the catheter (as shown in  FIG. 2C ), and (b) subsequent to the catheter having been retracted at least by the length of the device, such as to release the device from the distal end of the catheter (as shown in  FIG. 2D ). 
     As described hereinabove, for some applications, medical device  50  is a blood pump that includes a radially-expandable impeller disposed inside a radially-expandable impeller cage, e.g., as described with reference to  12 Ai- 22 Cii of WO 14/141284 to Schwammenthal, which is incorporated herein by reference. For such applications, the length of the cage, measured along the longitudinal axis of the cage, and when the cage is in a radially expanded configuration, is typically greater than 17 mm, less than 26 mm, and/or between 17 and 26 mm. For some applications, the length of second portion  24  of the tube defined by catheter  20  is at least 30 mm (e.g., at least 50 mm), and/or less than 80 mm (e.g., less than 65 mm). 
     Typically, during deployment of medical device  50  inside renal vein (i.e., during retraction of catheter  20  from the position shown in  FIG. 2C  to the position shown in  FIG. 2D ), third portion  26  of the catheter is configured to stabilize the catheter by contacting an inner wall of the subject&#39;s vena cava  44 . Further typically, subsequent to the deployment of the medical device inside the renal vein, third portion  26  of the catheter is configured to stabilize the catheter by contacting the inner wall of the vena cava, as shown in  FIG. 2D . In this manner, third portion  26  acts as a stabilizing portion of the catheter. As described hereinabove, the length of the third portion of the tube defined by catheter  20  is typically at least twice the length (e.g., at least 3 times the length) of medical device  50 . Typically, the third portion is thus configured to contact the inner wall of vena cava  44  both (a) before the catheter has been retracted such as to release the device from the distal end of the catheter (as shown in  FIG. 2C ), and (b) subsequent to the catheter having been retracted at least by the length of the device, such as to release the device from the distal end of the catheter (as shown in  FIG. 2D ). 
     As described hereinabove, for some applications, medical device  50  is a blood pump that includes a radially-expandable impeller disposed inside a radially-expandable impeller cage, e.g., as described with reference to  12 Ai- 22 Cii of WO 14/141284 to Schwammenthal, which is incorporated herein by reference. For such applications, the length of the cage, measured along the longitudinal axis of the cage, is typically greater than 17 mm, less than 26 mm, and/or between 17 and 26 mm. For some applications, the length of third portion  26  of the tube defined by catheter  20  is at least 30 mm (e.g., at least 50 mm), and/or less than 80 mm (e.g., less than 65 mm). 
     For some applications, during at least a portion of the deployment of medical device  50  inside renal vein  42 , fourth portion  28  of the catheter is configured to stabilize the catheter by contacting an inner wall of the subject&#39;s renal vein. For example, as shown in  FIG. 2C , prior to the retraction of catheter  20  such as to deploy device  50 , the fourth portion stabilizes the catheter by contacting the inner wall of the renal vein. In this manner, fourth portion  28  acts as a stabilizing portion of the catheter. For some applications, fourth portion  28  of the catheter is configured to stabilize the catheter by contacting an inner wall of the subject&#39;s renal vein even after the device has been deployed by the catheter having been retracted proximally. Alternatively, fourth portion  28  of the catheter is configured not contact the inner wall of the subject&#39;s renal vein after the device has been deployed by the catheter having been retracted proximally, as shown in  FIG. 2D . 
     Reference is now made to  FIG. 2E , which is a schematic illustration of catheter  20 , the catheter having been inserted into the subject&#39;s vasculature via an artery of a subject&#39;s groin (right femoral artery  60 , in the example shown). A distal end of the catheter is advanced into a renal artery of the subject that is ipsilateral to the artery of the groin (e.g., right renal artery  62 , in the example shown). For some applications, generally similar techniques to those described hereinabove with reference to  FIGS. 2A-2D  are performed on the arterial side of the subject&#39;s vasculature, mutatis mutandis. For some applications, when catheter  20  is used on the arterial side of the subject&#39;s vasculature, during at least a portion of the procedure (a) second portion  24  of the catheter stabilizes the catheter by contacting an inner wall of an iliac artery  64  of the subject, (b) third portion  26  of the catheter stabilizes the catheter by contacting an inner wall of an aorta  66  of the subject, and (c) fourth portion  28  of the catheter stabilizes the catheter by contacting an inner wall of renal artery  62 . Typically, both before and after the catheter is retracted such as to release device  50  inside the renal artery, (a) second portion  24  of the catheter stabilizes the catheter by contacting the inner wall of iliac artery  64 , and (b) third portion  26  of the catheter stabilizes the catheter by contacting the inner wall of aorta  66 . 
     Reference is now made to  FIGS. 3A-B , which are schematic illustrations of catheter  20  being inserted via a vein of a subject&#39;s groin (right femoral vein  40 , in the example shown), a distal end of the catheter being advanced into a renal vein of the subject that is contralateral to the vein of the groin (e.g., left renal vein  72 , in the example shown), in accordance with some applications of the present invention. 
     For some applications, in order to insert the distal end of the catheter into renal vein  72 , the distal end of the catheter is first placed into the subject&#39;s vena cava  44 , downstream of (i.e., distal to) the renal vein. The catheter is inserted such that due to the curvature of the catheter, the distal tip of the catheter pushes against the inner wall of the vena cava on the contralateral side of the vena cava, as shown in  FIG. 3A . The catheter is then retracted proximally, such that when the distal tip of the catheter passes the opening to the renal vein, the distal tip of the catheter enters the renal vein. When the distal tip has entered the renal vein, the catheter is then advanced, such that the distal tip of the catheter is disposed inside the renal vein in the vicinity of the subject&#39;s kidney  46 , as shown in  FIG. 3B . As described hereinabove with reference to  FIGS. 2A-B , typically, the tip of catheter  20  being atraumatic reduces a likelihood of an injury being caused to the inner wall of the vena cava, during the insertion of the catheter, relative to if the distal tip of the catheter were not atraumatic. 
     Reference is now made to  FIGS. 3C-D , which are schematic illustrations of portions of catheter  20 , respectively before and after medical device  50  has been deployed inside renal vein  72 , via the distal end of the catheter, in accordance with some applications of the present invention. Typically, during deployment of medical device  50  inside renal vein  72  (i.e., during retraction of catheter  20  from the position shown in  FIG. 3C  to the position shown in  FIG. 3D ), second portion  24  of the catheter is configured to stabilize the catheter by contacting an inner wall of iliac vein  52 . Further typically, subsequent to the deployment of the medical device inside the renal vein second portion  24  of the catheter is configured to stabilize the catheter by contacting the inner wall of iliac vein  52 , as shown in  FIG. 3D . As described hereinabove, with reference to  FIGS. 2C-D , for some applications, the device is temporarily placed inside the subject&#39;s renal vein, in order to provide an acute treatment to the subject. The catheter remains in place inside the subject&#39;s vasculature during the treatment, and the second portion of the catheter provides stabilization to the catheter by contacting the inner wall of iliac vein  52 , as shown in  FIG. 3D . Subsequent to the treatment being terminated, the device is withdrawn from the subject&#39;s renal vein via the catheter. 
     As described hereinabove with reference to  FIGS. 2C-D , the length of the second portion of the tube defined by catheter  20  is typically at least twice the length (e.g., at least 3 times the length) of medical device  50 . Typically, the second portion is thus configured to contact the inner wall of iliac vein  52  both (a) before the catheter has been retracted such as to release the device from the distal end of the catheter (as shown in  FIG. 3C ), and (b) subsequent to the catheter having been retracted at least by the length of the device, such as to release the device from the distal end of the catheter (as shown in  FIG. 3D ). 
     As described hereinabove, for some applications, medical device  50  is a blood pump that includes a radially-expandable impeller disposed inside a radially-expandable impeller cage, e.g., as described with reference to  12 Ai- 22 Cii of WO 14/141284 to Schwammenthal, which is incorporated herein by reference. For such applications, the length of the cage, measured along the longitudinal axis of the cage, is typically greater than 17 mm, less than 26 mm, and/or between 17 and 26 mm. For some applications, the length of second portion  24  of the tube defined by catheter  20  is at least 30 mm (e.g., at least 50 mm), and/or less than 80 mm (e.g., less than 65 mm). 
     Typically, during deployment of medical device  50  inside renal vein  72  (i.e., during retraction of catheter  20  from the position shown in  FIG. 3C  to the position shown in  FIG. 3D ), third portion  26  of the catheter is configured to stabilize the catheter by contacting an inner wall of the subject&#39;s vena cava  44 . Further typically, subsequent to the deployment of the medical device inside the renal vein, third portion  26  of the catheter is configured to stabilize the catheter by contacting the inner wall of the vena cava, as shown in  FIG. 3D . As described hereinabove, the length of the third portion of the tube defined by catheter  20  is typically at least twice the length (e.g., at least 3 times the length) of medical device  50 . Typically, the third portion is thus configured to contact the inner wall of vena cava  44  both (a) before the catheter has been retracted such as to release the device from the distal end of the catheter (as shown in  FIG. 3C ), and (b) subsequent to the catheter having been retracted at least by the length of the device, such as to release the device from the distal end of the catheter (as shown in  FIG. 3D ). 
     As described hereinabove, for some applications, medical device  50  is a blood pump that includes a radially-expandable impeller disposed inside a radially-expandable impeller cage, e.g., as described with reference to  12 Ai- 22 Cii of WO 14/141284 to Schwammenthal, which is incorporated herein by reference. For such applications, the length of the cage, measured along the longitudinal axis of the cage, is typically greater than 17 mm, less than 26 mm, and/or between 17 and 26 mm. For some applications, the length of third portion  26  of the tube defined by catheter  20  is at least 30 mm (e.g., at least 50 mm), and/or less than 80 mm (e.g., less than 65 mm). 
     For some applications, during at least a portion of the deployment of medical device  50  inside renal vein  72 , fourth portion  28  of the catheter is configured to stabilize the catheter by contacting an inner wall of the subject&#39;s renal vein. For example, as shown in  FIG. 3C , prior to the retraction of catheter  20  such as to deploy device  50 , the fourth portion stabilizes the catheter by contacting the inner wall of the renal vein. For some applications, fourth portion  28  of the catheter is configured to stabilize the catheter by contacting an inner wall of the subject&#39;s renal vein even after the device has been deployed by the catheter having been retracted proximally, as shown in  FIG. 3D . 
     Reference is now made to  FIG. 3E , which is a schematic illustration of catheter  20 , the catheter having been inserted into the subject&#39;s vasculature via an artery of a subject&#39;s groin (right femoral artery  60 , in the example shown). A distal end of the catheter is advanced into a renal artery of the subject that is contralateral to the artery of the groin (e.g., right renal artery  82 , in the example shown). For some applications, generally similar techniques to those described hereinabove with reference to  FIGS. 3A-3D  are performed on the arterial side of the subject&#39;s vasculature, mutatis mutandis. For some applications, when catheter  20  is used on the arterial side of the subject&#39;s vasculature, during at least a portion of the procedure (a) second portion  24  of the catheter stabilizes the catheter by contacting an inner wall of an iliac artery  64  of the subject, (b) third portion  26  of the catheter stabilizes the catheter by contacting an inner wall of an aorta  66  of the subject, and (c) fourth portion  28  of the catheter stabilizes the catheter by contacting an inner wall of renal artery  82 . Typically, both before and after the catheter is retracted such as to release device  50  inside the renal artery, (a) second portion  24  of the catheter stabilizes the catheter by contacting the inner wall of iliac artery  64 , and (b) third portion  26  of the catheter stabilizes the catheter by contacting the inner wall of aorta  66 . 
     It is noted that, in accordance with the above description of catheter  20 , the catheter is shaped such that both (a) when the catheter is placed into a renal vessel that is ipsilateral with respect to the vessel of the groin via which the catheter is inserted, and (b) when the catheter is placed into a renal vessel that is ipsilateral with respect to the vessel of the groin via which the catheter is inserted, the catheter is stabilized by portions of the catheter contacting inner walls of the blood vessels of the subject at at least two points. Typically, the second portion of the catheter stabilizes the catheter by contacting an inner wall of an iliac vessel of the subject, and the third portion stabilizes the catheter by contacting an inner of the vena cava or the aorta of the subject. Further typically, the catheter is stabilized by portions of the catheter contacting inner walls of the blood vessels of the subject at the at least two points (a) before the catheter is retracted such as to release the device from the distal end of the catheter, and (b) subsequent to the catheter having been retracted such as to release the device from the distal end of the catheter. 
     It is noted that, for some applications, catheter  20  is used for the insertion of a medical device therethrough that provides a therapy (e.g., renal denervation) to a renal vessel (e.g., a renal artery or a renal vein). Subsequent to providing the therapy, the device is withdrawn from the renal vessel via the catheter. Catheter  20  provides stabilization during the advancement of the device, during the withdrawal of the device, and/or during the provision of the therapy by (a) second portion  24  of the catheter stabilizing the catheter by contacting an inner wall of an iliac vessel of the subject, (b) third portion  26  of the catheter stabilizing the catheter by contacting an inner wall of vena cava  44  or aorta  66  of the subject, and, optionally, (c) fourth portion  28  of the catheter stabilizing the catheter by contacting an inner wall of the renal vessel, in accordance with the techniques described hereinabove. 
     Although catheter  20  is described hereinabove as being inserted via a femoral blood vessel, for some applications, catheter  20  is inserted through a different peripheral vessel in the subject&#39;s groin, e.g., the iliofemoral vein. Alternatively or additionally, the catheter is inserted via a vein of the arm (e.g., a brachial, or antecubital vein), the chest (e.g., the subclavian vein), or the neck (e.g., the jugular vein). For some applications, catheter  20  is inserted into the hepatic vein. 
     In general, in the specification and in the claims of the present application, the term “proximal” and related terms, when used with reference to a device or a portion thereof, should be interpreted to mean an end of the device or the portion thereof that, when inserted into a subject&#39;s body, is typically closer to a location through which the device is inserted into the subject&#39;s body. The term “distal” and related terms, when used with reference to a device or a portion thereof, should be interpreted to mean an end of the device or the portion thereof that, when inserted into a subject&#39;s body, is typically further from the location through which the device is inserted into the subject&#39;s body. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.