Abstract:
Catheters are provided which have a high capacity of axial (pushability) and rotational (torquability) movement with relative maximum flexibility and which, at the same time have the ability to adapt to at least partial variations of diameter under the thrust of other catheters or dilators travelling though the lumen or so as to flatten itself at least partially to travel through the lumen of other catheters, such as for example feed catheters.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase Application of PCT International Application No. PCT/IB2014/058516, International Filing Date, Jan. 24, 2014, claiming priority to Italian Patent Application No. PD2013A000081 (102013902142496), filed Mar. 29, 2013 each of which is hereby incorporated by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a controlled deformation catheter and in particular to a catheter suitable to modify the cross section of the inner lumen both so as to permit the passage of other catheters, dilators and/or instruments of various types therein, and so as to permit its deformation for the insertion of another catheter, such as for example, a guide catheter. 
     BACKGROUND OF THE INVENTION 
     The catheters used in the human body, in particular vascular catheters for angioplasty and stenting need support to be moved axially (pushability) and to rotate (torquability) as well as requiring flexibility to move up the arterial tree and the veins for this reason catheters are usually made of a metal core covered in plastic material. 
     The current standard core of catheters is composed of a mesh lamina or, to give maximum flexibility, of a coil core. In both cases the catheter has a predefined diameter with no possibility of adaptability to possible, even minimal, variations of diameter required. 
     This impossibility of adapting in shape in practice constitutes a significant limitation to the applications of said catheter. 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is to make a catheter which retains a high capacity of axial (pushability) and rotational (torquability) movement with relative maximum flexibility and which, at the same time has the ability to adapt to at least partial variations of diameter under the thrust of other catheters or dilators travelling though the lumen or so as to flatten itself at least partially to travel through the lumen of other catheters, such as for example feed catheters. 
     Such purposes are achieved by catheters as described and claimed herein. 
     Further characteristics and advantages of the present invention will be more clearly comprehensible from the following description, given purely by way of non-limiting examples with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1 a    shows a side view of a catheter according to one embodiment of the present invention, in a non-deformed configuration; 
         FIG. 1 b    shows a projection on a centreline plane M of an inner core of the catheter; 
         FIG. 2  shows a perspective view of a catheter according to the present invention, in a non-deformed configuration; 
         FIG. 3  shows a perspective view in a deformed configuration, of the catheter in  FIG. 2 ; 
         FIG. 4  shows a perspective view of a catheter according to a further embodiment of the present invention; 
         FIGS. 5-7  show perspective views from different angles, in a deformed configuration, of the catheter in  FIG. 4 ; 
         FIGS. 8-9  show perspective views of a catheter according to a further embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The elements or parts of elements common to the embodiments described below will be indicated using the same reference numerals. 
     With reference to the aforementioned figures, reference numeral  4  globally denotes a catheter comprising a catheter body  8  which extends from a proximal end  12  to a distal end  16 , in a longitudinal direction X-X. 
     The catheter body  8  is a hollow tubular body which defines at least one lumen  20 . 
     For the purposes of the present invention the catheter body  8  may have varied geometries; for example, the catheter body  8 , in relation to a cross-section plane perpendicular to said longitudinal direction X-X, may have a hollow circular cross-section or even a hollow elliptical/oval cross-section. 
     The cross-section of the catheter body  8 , as described further below, also depends on the length and on the inclination of the ribs  40  embedded inside said body. 
     The catheter body  8  comprises a core  24  embedded inside a flexible, outer covering layer  28 . In other words, the outer covering layer  28  has a greater thickness than the thickness of the core  24  so that it is completely covered by said layer. For example, the core is made of nitinol, or in a printed polymer material or in a metal or polymer material obtained by laser printing. 
     The outer covering layer  28  is preferably made of polymer material. 
     The covering material, that is the outer covering layer  28  must be sufficiently elastic as to permit the area without the core  24  to extend. 
     The core  24  comprises a plurality of ribs  40  which extend inside the covering layer  28 : said ribs  40  extend from an attachment end  44 , at which they connect to each other, to a free end  48 , opposite the attachment end  44 , wherein the line joining the attachment ends  44  of the pairs of ribs  40  defines a dorsal side  36  of the catheter body  8 . 
     In a rest configuration, as specified further below, said attachment ends  44  are aligned parallel to the longitudinal direction X-X. 
     According to one embodiment, the core  24  comprises a longitudinal element or backbone  32 , defining a dorsal side  36  of the catheter body  8 , from which the ribs  40 , in pairs, unwind from opposite sides to the longitudinal element  32 , extending inside said outer covering layer  28 . 
     The longitudinal element  32  connects the attachment ends  44  of the pairs of ribs  40  to each other. 
     In other words, the attachment ends  44  of the ribs  40  converge in the longitudinal element or backbone  32  which mechanically connects the pairs of ribs  40  to each other along the longitudinal extension of the catheter body  8 . 
     The free ends  48  of the same pairs of ribs  40  are separate from each other and identify at least one discontinuity  52  of said ribs  40 , said discontinuity  52  being positioned on a ventral side  56 , opposite said dorsal side  36 . 
     Advantageously, having defined a first plane P perpendicular to the longitudinal element  32  and passing through the attachment end  44  of a rib  40 , and having defined a second plane Q passing through the free end  48  and through the attachment end  44  of the same rib  40 , said planes P, Q are inclined to each other so as to form an acute angle A on the side of the proximal end  12  or of the distal end  16 . In yet other words, the ribs  40  are not perpendicular overall to the longitudinal element  32 , but are inclined either backwards, that is towards the proximal end  12 , or forwards, that is towards the distal end  16 . 
     The inclinations of the ribs  40  are more clearly visible in  FIG. 1 b    which shows the projection of the core of the catheter body  8  on a centreline plane M-M of said catheter body. 
     For example, the backward inclination of the ribs  40 , that is towards the proximal end  12 , facilitates the penetration of the catheter  4  in a narrower tube. 
     These ribs  40  must be inclined co-measuring the inclination, length and aperture depending on whether one wishes to obtain catheters of a circular or oval cross-section. In particular, the inclination favours the deformability and thus the penetrability of the catheter  4  which will also be in relation to the thickness and wideness of said ribs. 
     For the purposes of the present invention the definition of longitudinal direction and of angular inclinations and orientations of the ribs  40  refer to a rest position wherein the catheter body  8  is positioned in a rectilinear configuration, parallel to said longitudinal direction X-X. 
     Consequently, the arrangement of the planes, for example first and second P, Q are to be understood as in relation to a rectilinear, rest configuration of the catheter body  8 . It is understood that the catheter body  8  is perfectly able to assume any curvilinear configuration so as to follow the winding nature of the vessels; in such curvilinear configuration obviously the inclinations relative to the planes and the ribs  40  may vary depending on the degree of deformation imposed For example the catheter  4  may curve towards the ventral side  56 , so as to assume a convex configuration on the dorsal side  36  and concave on the ventral side  56 , but also curve towards the dorsal side  36 , so as to assume a concave configuration on the dorsal side  36  and convex on the ventral side  56 . In addition, the catheter body  8  may also curve in transversal directions Y-Y, perpendicular to the longitudinal direction X-X, so as to assume a concave configuration at a first transversal side  57  and a convex configuration at a second transversal side  58 . Obviously the opposite curvature is also possible. The ribs  40  arranged on the transversal side  57 , 58  which curve in a convex configuration, move away from each other, while the ribs  40  arranged on the opposite transversal side  58 , 57 , which curve in a concave configuration, move towards each other. 
     In this manoeuvre therefore the curvature of the catheter body is conditioned by the distance between said ribs. 
     Henceforth in the description, all the geometric configurations described, will always refer to the rectilinear configuration of the catheter body  8 . 
     According to one embodiment, said acute angle A, formed between the first and second plane P, Q, is from 10 to 70 degrees. 
     According to a further embodiment, said acute angle A, formed between the first and second plane P, Q, is from 40 to 60 degrees. 
     According to a possible embodiment, the ribs  40 , in relation to a projection plane H perpendicular to the longitudinal element  32  and passing through a centreline M of the catheter body  8 , have a rectilinear median line S ( FIG. 1 b   ). The median line S is the place of the midpoints of the longitudinal thicknesses of the ribs  40 , said longitudinal thicknesses being measured in relation to lines parallel to said longitudinal direction X-X. 
     According to a further embodiment, the ribs  40 , in relation to a projection plane H perpendicular to the longitudinal element  32  and passing through a centreline M of the catheter body  8 , have a curvilinear median line S. As seen, the median line S is the place of the midpoints of the longitudinal thicknesses of the ribs  40 , said longitudinal thicknesses being measured in relation to lines parallel to said longitudinal direction X-X. 
     According to one embodiment, the ribs  40  are curvilinear and are oriented so as to present an intrados  60  or concave portion, on the side of the proximal end  12 , and an extrados  64 , or convex portion, on the side of the distal end  16 . 
     The inverse configuration is also possible, according to which the ribs  40  are curvilinear and are oriented so as to present an intrados  60  or concave portion, on the side of the distal end  16 , and an extrados  64 , or convex portion, on the side of the proximal end  12 . 
     According to one embodiment, the ribs  40  present a first section  68  which extends from the attachment end  44  to an intermediate portion  72  and which, in relation to a projection plane H perpendicular to the longitudinal element  32  and passing through a centreline M of the catheter body  8 , is inclined towards the distal end  16 , and a second section  76  which extends from the intermediate portion  72  to the free end  48  and which, in relation to said projection plane H, is inclined towards the proximal end  12 , so that the first and the second sections  68 , 76  have opposite inclinations to each other. 
     The inverse configuration is also possible, according to which the first section  68  proves inclined towards the proximal end  12 , and the second section  76  proves inclined towards the distal end  16 , so that the first and the second sections  68 , 76  have opposite inclinations to each other. 
     The fact that the first and the second sections  68 ,  76  have opposite inclinations to each other improves the behaviour of the ribs  40  during the elastic deformation of the catheter body  8 , both on the passage of the catheter body  8  through a lumen of reduced dimensions in relation to the outer diameter of said catheter body, and on the introduction of a body, such as for example an instrument, inside the lumen  20 , said instrument having a greater diameter than said lumen. 
     In fact, the presence of the double curvature counters an excessive closing or widening of the ribs  40  upon the variation in diameter of the catheter body. 
     Such double curvature of the ribs  40  contributes to the geometric and dimensional control of the catheter body  8 . 
     According to one embodiment, at least an intermediate portion  72  of the ribs  40  extends from the first plane P, passing through the attachment end  44  and perpendicular to the longitudinal element  32 , towards the distal end  16  and at least a second section  76  of the rib  40 , comprising said free end  48 , extends from the first plane P towards the proximal end  12 . 
     According to one embodiment, the ribs  40  are conformed and oriented in such a way that a radial plane R, perpendicular to the longitudinal element, passing through the free ends  48  of a first pair of ribs  40 ′, intercepts at least partially an intermediate portion  72  of a second pair of ribs  40 ″, adjacent to the first pair of ribs  40 ′, on the side of the proximal end  12 . 
     Obviously the inverse configuration is also possible, according to which the ribs  40  are conformed and oriented in such a way that a radial plane R, perpendicular to the longitudinal element, passing through the free ends  48  of a first pair of ribs  40 ′, intercepts at least partially an intermediate portion  72  of a second pair of ribs  40 ″, adjacent to the first pair of ribs  40 ′, on the side of the distal end  16 . 
     According to a possible embodiment, the ribs  40  are thread-shaped, that is obtained from a flexible, thread-shaped filament. 
     According to a further embodiment, the ribs  40  have a variable axial thickness, said thickness being measured parallel to said longitudinal direction. 
     According to a further embodiment, said axial thickness of the ribs increases moving from the attachment end  44  towards an intermediate portion  72  and tapers moving from the intermediate portion  72  towards the free end  48 , the intermediate portion  72  being comprised between the attachment end  44  and the free end  48 . 
     Preferably, each pair of ribs  40  comprises ribs symmetrical to each other in relation to the longitudinal element  32 . 
     Preferably, the length and curvature of the ribs  40  is modified according to the desired inclination of said ribs. 
     According to a possible embodiment, the free ends  48  of the same pair of ribs  40  are separate from each other at a discontinuity  52  having a curvilinear extension equal to at least 20% of the total perimeter of the catheter body  8 , measured on a cross-section plane perpendicular to said longitudinal element  32 . 
     Preferably, the discontinuity  52  has a curvilinear extension of not more than 50% of the total perimeter of the catheter body  8 , measured on a cross-section plane perpendicular to said longitudinal element  32 . 
     According to one embodiment, the ribs  40 , at the attachment end  44 , comprise at least one notch  84  suitable for favoring the flexing of the ribs  40  towards the proximal end  12 , so as to keep a skirt of rib  40  in one piece with the longitudinal element  32 , positioned on the attachment end  44  on the side of the proximal end  12  and to have an opening  88  positioned on the attachment end  44  on the side of the distal end  16 . 
     The inverse configuration is also possible, wherein the skirt of rib  40  in one piece with the longitudinal element  32 , is positioned on the attachment end  44 , on the side of the distal end  16  and the opening  88  is positioned on the attachment end  44  on the side of the proximal end  12 . 
     In general, the notch  84  is positioned on the side opposite to the direction of inclination of the ribs  40 ; this way if the ribs  40  are inclined towards the proximal end  12 , the opening  88  defined by the notch  84  is facing towards the distal end  16 , while if the ribs  40  are inclined towards the distal end  16 , the opening  88  defined by the notch  84  is facing towards the proximal end  12 . 
     In other words, the notch  84  and the relative opening  88  are positioned so as to facilitate the predefined inclination of the ribs  40 . 
     For example such notch  84  has a circular sector conformation. 
     Preferably, the opening  88  has an extension of 50% to 80% of the cross-section of solid attachment, in other words the notch consists of a removal of material of 50-80% compared to the corresponding solid cross-section of the attachment end  44 . 
     Preferably, the ribs  40  have a variable rigidity which decreases moving from the dorsal side  36  to the ventral side  56 ; such variable rigidity may for example be achieved, as seen, by reducing the axial thickness of the ribs  40 , that is the thickness measured in a direction parallel to the longitudinal direction X-X, moving from the attachment end  44  towards the free end  48 . 
     A reduction of the radial thickness of the ribs  40  moving from the attachment end  44  towards the free end  48  may also be provided for, wherein the radial thickness is the thickness of the ribs  40  measured in relation to a cross-section plane perpendicular to the longitudinal direction X-X. 
     As may be seen from the description, the catheter according to the invention makes it possible to overcome the drawbacks presented in the prior art. 
     In particular, the inclination of the ribs permits a greater deformation and flattening of the profile of the catheter when this needs to be inserted in another catheter, such as for example, in the case of a guide catheter which needs to enter a feed catheter. 
     In addition, the inclination of the ribs permits a dilation when, inside the lumen of the catheter comprising such inclined rib conformation, another catheter or feeder of a slightly larger calibre compared to said inner lumen is inserted. 
     The catheter according to the invention may be devised so as to be applicable to different types of catheters and feeders. 
     Thereby making it possible to overcome the handicap of guide catheters or feeders which move along winding anatomies (see the aortic fork in the PTA/cross over stenting procedure) which, on account of the extensive bending which reduces the lumen and increases the friction, prevents the passage through it of catheters equal to the nominal lumen. Generally speaking today catheters having a diameter of at least one French (F) more than the catheter needed in rectilinear seats must be used. In these cases the ventral side must be placed on the outer side of the curvature axis rotating the catheter as needed. 
     In addition, the ventral area permits the association, if needed of an (outer) guide beside the guide catheter with a ‘snake skeleton’ core deforming it inwards in the ventral line of the catheter (where there is no core) maintaining an overall circumference enabling it to enter said feeder, (a feeder of a greater calibre is not needed). 
     In addition, the present invention does not require the ovalisation of the tip of a catheter created to permit the passage of the guide, allowing the tip of the catheter to retain a diameter identical to the rest of the catheter body for its entire length: this way important operating advantages are achieved for the passage of subsequent catheters and/or the overall diameter of said catheter may be reduced. 
     In addition, the present invention further makes it possible, using elastic covering material, to create feeders of variable diameter depending on the dilator used, the catheter being able to expand depending on the dilator used. 
     Flexible shape memory metal may be used or depending on use, expandable material capable of maintaining its shape may be used. 
     The functioning of the catheter according to the present invention derives from the co-operation of the core and the outer covering layer. 
     In fact, the core has the primary function of guaranteeing the characteristics of resistance upon advancement and rotation (pushability e torquability) of the catheter, that is to assure the necessary rigidity of the catheter so that it may be introduced and guided inside vessels or other instruments following the desired geometries. 
     In addition the core has the function of withstanding stresses and strains which the covering layer alone would not be able to withstand in the absence of armor, without incurring in plastic deformations or damage. 
     The area of the catheter body on the ventral side is at least partially without a core so as to permit a greater deformability of the catheter body to modify the through cross-section or lumen both in terms of compression and in terms of dilation. 
     A person skilled in the art may make modifications and variations to the catheters described above so as to satisfy contingent and specific requirements, while remaining within the sphere of protection of the invention as described and claimed herein.