Catheter guide support

A catheter guide support is provided having a wire with a proximal region, of substantially constant cross-section, a distal tapered region and a flexible protecting sheath which extends at least along the length of the distal region of the wire. The wire is constructed integral with the sheath only at the free extremity of its distal region by means of a first weld forming a rounded end, said support also having a tube extending over the whole region of the wire not covered by the sheath, one extremity of the tube simply abutting against the proximal region of the sheath whereas the opposite extremity of the tube is fixed to the proximal region of the wire by means of a second weld.

FIELD OF THE INVENTION 
The instant invention relates to guide supports in general and in 
particular to guide supports adapted to be introduced and guided in blood 
vessels of small diameter in order to facilitate the introduction of a 
catheter into the latter. 
This type of guide support for catheters is useful for many applications 
notably in the field of cardiovascular surgery such as, for example, in 
cardiovascular angioplasty, during which a catheter is introduced into a 
constricted region in the coronary artery of a patient and the catheter is 
then inflated in order to dilate the passage of the artery. 
DESCRIPTION OF THE PRIOR ART 
It is already known from the specification of U.S. Pat. No. 4,545,390 to 
provide a guide wire for a catheter, the latter having a small diameter 
(.ltoreq.0.5 mm) and being adapted to be introduced by the endovenous 
route into the human body. 
According to this specification, the guide support has a stainless steel 
wire having a tapered zone in its distal region onto which is threaded a 
helical spring having a diameter substantially equal to the diameter of 
the main wire. The proximal end of the spring is fixed to the wire by 
soldering in the region of the wire where the latter begins to taper and 
the distal extremity of the spring is also soldered to the distal 
extremity of the wire. 
Such a guide support generally works in a satisfactory manner but does, 
however, have certain disadvantages. 
Thus, during the fixing of the spring to the wire by soldering, the latter 
is heated to temperatures (.congruent.500.degree. C.) which approach the 
temperatures at the beginning of the crystallographic transformation of 
stainless steels and which correspond to the annealing of the latter, and 
at which the mechanical properties of these steels begin to deteriorate 
very substantially. It will thus be readily understood that this annealing 
which occurs during the soldering operation, could lead to premature 
rupture of the wire during use, such rupture being liable to cause serious 
complications if it were to occur within the vein of a patient. 
Furthermore, guide supports such as are described in the above mentioned 
specification have an extra thickness at the point of the solder which 
carries the risk of impeding or even blocking the catheter when the latter 
slides on the support. 
In addition, when the wire, which is generally coated with a layer of a 
material having a low coefficient of o friction, such as TEFLON.RTM., is 
associated with a helical spring coated with gold for biocompatability 
reasons, the soldering of the spring onto the wire causes a deterioration 
both of the gold layer and also of the layer of material having a low 
coefficient of friction prejudicial to the biocompatibilty of the guide 
support. 
OBJECTS OF THE INVENTION 
It is therefore a principle object of the instant invention to overcome the 
above mentioned disadvantages of the prior art and to provide a guide 
support for a catheter having improved operational reliability. 
BRIEF SUMMARY OF THE INVENTION 
For this purpose, it is an object of the invention to provide a guide 
support for a catheter having a wire having a proximal region of 
substantially constant section and a tapered distal region and a flexible 
protective sheath extending at least over the length of the distal region 
of the wire. 
In accordance with the invention, the wire is attached to the sheath only 
at the free end of its distal region by means of a first weld forming a 
rounded tip and the support also having a tube extending over the whole of 
that part of the wire not covered by the sheath, one end of the tube 
simply abutting against the proximal region of the sheath whereas the 
opposite end of the tube is fixed to the proximal part of the wire by a 
second weld. 
Due to these characteristics, the weld of the protective sheath on the 
operating part of the wire is eliminated. Thus, the mechanical properties 
of the wire in the areas where it is subjected to mechanical stress, 
especially by bending, when the support is employed in the body of a 
patient are not in danger of being changed, for example by annealing of 
the material at the point of the weld when the sheath is welded to the 
wire, so that the operational reliability of the support is increased. 
According to a preferred embodiment of the invention, the wire also 
comprises, at the free end of its distal region a reinforcing section 
having a cross-section substantially equal to the proximal region of the 
wire. 
Such a reinforcing section makes the end of the support more rigid and 
facilitates the introduction of the latter into the veins of the patient 
especially in their more sinuous passages.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, it will be seen that there is a guide support for a 
catheter according to the invention designated by the general reference 
numeral 1. Such a guide support is readily used in medicine for carrying 
out angioplasty techniques, especially for facilitating the introduction 
and positioning of a catheter for exploratory, treatment or similar 
purposes in the cardiovascular system of a patient. In order to position a 
catheter, it is thus necessary as a first step to introduce the guide 
support up to the point where treatment of the cardiovascular system is 
needed and then, in a second step, to slide the catheter required on the 
support up to the zone to be treated. 
As is clearly shown in FIG. 1, the guide support for the catheter comprises 
a wire 2 forming the bore of the support on which is threaded and made 
integral with the wire, the protective sheath 4 and a tube 6. 
The wire 2, which is preferably made of stainless steel for 
biocompatability reasons, has a proximal region 8 of constant cross 
section and a tapered distal section 10. 
The proximal region 8 is of generally cylindrical form and the distal 
region 10 is of generally truncated form. 
Typically, the diameter of the region 8 of the part of the wire of constant 
cross-section is of the order of 0.5 mm and the diameter of the end of the 
distal region of the wire is of the order of 0.1 mm. 
The protective sheath 4 is formed by a helical spring with contiguous 
spirals. This sheath extends over the distal part 10 of the wire and 
slightly further over a cylindrical portion 12 of the wire on which it 
rests. In this connection it should be noted that the internal diameter of 
the sheath is substantially adjusted to the diameter of the proximal part 
of the wire. 
In accordance with the invention, the sheath 4 is fixed to the wire 2 by a 
single weld 14 at the free end 16 of the distal region 10 of the wire. 
The weld 14 is advantageously a rounded end of the type which will minimise 
risk of injury to the internal walls of the cardiovascular system during 
introduction of the support. 
The tube 6, threaded over the entire proximal region 8 of the wire which is 
not covered by the sheath 4, abuts simply at its end 17 against the 
proximal region 18 of the sheath 4 and is fixed at its end 20 opposite the 
end 22 of the proximal part 8 of the wire by means of a weld 24 which also 
has a rounded tip. 
Preferably, and as is shown in FIG. 1, the outside diameter D1 of the 
sheath 4 and that of the tube D2 are substantially equal. In a typical 
situation, the diameter of these two elements is less than or equal to 0.8 
mm according to the specific applications of the support. 
Furthermore, it will be noted that the diameter D3 of the rounded tips is 
also substantially equal to that of the tube 6 and to that of the sheath 
4. In this way, by means of the rounded shape and the dimension of the 
end, the risk of lesions to the internal walls of the veins during 
introduction of the support is greatly diminished and the introduction of 
the support is greatly facilitated. 
It will also be seen that in the embodiment of the support shown, the tube 
6 is coated over its entire length with a layer 26 of a material having a 
low coefficient of friction such as TEFLON.RTM.. This layer 26 facilitates 
on the one hand the introduction of the support into the cardiovascular 
system of the patient and on the other hand and more importantly the 
sliding of the catheter on the support when the latter is inserted into 
the body of the patient. 
It will thus be readily understood, that with the support structure of the 
invention, the tube 6 may as a first step be covered with the layer 26 
without the former being subject to wear in the active zones of the 
support at the moment when the tube or the sheath is welded, according to 
the invention, all welding of the active region of the wire has been 
eliminated in order to transfer them into neutral zones, that is to say in 
non-operational zones. 
In the embodiment shown, the sheath 4 is made from a biocompatible metal 
which preferably has radiolabile properties so that the extremity of the 
support may be rendered visible by fluoroscopy and thus permit guiding and 
precise positioning of the support in the cardiovascular system. By way of 
example, an alloy of platinum and iridium, containing 70 to 80% of 
platinum and 30 to 20% of iridium was used for the manufacture of the 
sheath 4. 
It is of course quite clear that in the situation where the radiolabile 
alloy forming the sheath is not biocompatible, as is for example the case 
with tungsten, one may cover the sheath with a metal coating that is 
biocompatible, such as gold. Here, too, it will be noted that the absence 
of any weld in the active area of the support prevents deterioration of 
the coating layer rendering the metal biocompatible. 
In the embodiment which has been described, the total length of the support 
is of the order of 200 mm. Clearly, this length may vary according to the 
use in question and more precisely as a function of the distance 
separating the place on the body where the support is introduced from the 
zone in the cardiovascular system which is to be treated. 
As far as the length of the tapered distal part of the wire on which the 
sheath is threaded, is concerned, it is preferably substantially less than 
or equal to 80 mm and this length may vary as a function of the rigidity 
required in the distal part of the wire. 
Referring now to FIG. 2, in which the same features are identical to those 
described in connection with FIG. 1 are identified using the same 
reference numerals, a variation of an embodiment of a support according to 
the invention is shown. 
According to this variation, the distal region 10 of the wire 2 comprises, 
at its end part, a reinforcing section 28 having a section substantially 
equal to the proximal section of the wire 2. 
In this embodiment of the invention, the length of the reinforcing section 
28 is of the order of 10 mm. A reinforcing section of this type enables 
the end region of the sheath to be supported and prevents any substantial 
deformation of this zone of the sheath that is subjected to substantial 
stress during introduction of the support so that its introduction into 
the veins is facilitated. It will be further understood that the length of 
this reinforcement cannot exceed a limited length since otherwise the 
flexibility of the end region of the support would be reduced and would 
impede precise guidance of the support in the cardiovascular system and 
especially in the case where the end of the support has to follow a very 
sinuous path. 
The structure of the support according to the invention enables the 
elimination of any welding of the active part of the wire 2 with the 
result that the risk of annealing of the material forming the wire is 
eliminated. It is also a fact that by dispensing with one of the welds, 
the manufacturing process is rendered more rapid and economical, the two 
welds 14 and 24 are welds which are preferably carried out using a 
microplasma process without the addition of any metal. In this case, it 
may be noted in an advantageous manner that the material of the two 
elements to be connected are fused together in an manner such that there 
is no annealing of the materials. 
It may also be noted that, due to the construction of the support, there is 
a reduction in the length of the tapered part, since it is not necessary 
to have a section of the tapered part for the welding of the sheath onto 
the wire. This makes this part easier to manufacture by milling.