NL9300728A - Thin-walled catheter with variable properties in a longitudinal direction - Google Patents

Abstract

The invention relates to a catheter comprising at least one innermost tubular element and an outermost tubular element on top. The innermost tubular element is made up of a number of adjacently arranged individual tubular segments with different properties. The flexibility of the segments increases from the proximal to the distal end and the outermost tubular element itself has a slight flexural rigidity. The distally last segment extends beyond the end of the outermost tubular element and this end has a wall thickness gradually decreasing to zero and is connected via the periphery with the last segment.

Description

THIN WALLED CATHETER WITH VARIABLE PROPERTIES

The invention relates to a catheter, in particular a catheter for angiographic purposes.

The development of catheters of this type has been directed to the manufacture of ever smaller diameter catheters which, however, must have a lumen of the largest diameter possible, so that the wall thickness of such catheters progressively decreases.

With thinner catheters it becomes increasingly difficult to give them sufficient bending stiffness, kinking stiffness and torsional stiffness, which properties are desirable when introducing a catheter of this type into the body of a patient. On the other hand, the distal end of the catheter must again be flexural to allow it to properly follow the bends in the blood vessels of the patient.

The object of the invention is now to provide a thin-walled catheter of the aforementioned type which can be manufactured with a very small diameter and yet has the desired properties.

This object is achieved with the catheter as characterized in claim 1. The segments themselves and the outer tube-like element can be made with a very small diameter, smaller than 1 mm and a very small wall thickness in the order of 0.05 mm manufactured. Each segment can be made from one type of material, for example by extrusion, so that its properties can be very well controlled.

The measure of claim 2 is preferably applied. Thus, a catheter of the aforementioned very small dimensions is obtained, which reliably has a stiffness decreasing from the proximal to the distal end. Stiffness is high near the proximal end, allowing good longitudinal pushing force on the catheter upon insertion without the risk of kinking. Due to the greater bending stiffness near the proximal end, the catheter moreover has a good torsional stiffness, so that the catheter can be rotated about its longitudinal axis in a controllable manner during insertion.

Near the distal end, the catheter according to the invention is very flexible, which is very favorable for following the bends in the blood vessel into which the catheter is inserted.

The measure of claim 3 is preferably applied. As a result, the risk of a weakening of the catheter with a high risk of kinking is small where the segments meet.

A further improvement is achieved with the measure of claim 4.

According to the further development, the measure of claim 5 is applied. Hereby a smooth transition and smooth connection of the outer tube-like element with the inner is obtained.

In order to further improve the physical properties such as buckling stiffness and torsional stiffness, the measure as set out in claim 6 can advantageously be applied. The measure of claim 7 is preferred in this respect. By varying the weaving or wrapping pattern, the properties can be further influenced.

In order to retain the desired small diameter and small wall thickness, the measure as set out in claim 8 is preferably applied.

The invention is further elucidated in the following description with reference to the appended drawing.

Figure 1 shows a partially sectioned view of a catheter according to the invention.

Figure 2 illustrates an application of the catheter of Figure 1.

Figure 1 shows the tubular portion of a catheter 1. The connector normally located at the proximal end is not shown here.

The catheter 1 according to the invention is composed of an inner tube-like element 2 and an outer tube-like element 3.

The inner tube-like element is itself composed of a number of contiguous individual tube-like elements 4, 5, 6, 7, each of which may have different properties.

Segments 4-7 can be manufactured separately, for example by extrusion of material of a particular composition, whereby each of these segments reliably has the desired properties.

The segments 4-7 are preferably connected where they lie against each other. The different segments can be slid onto a metal support wire and the ends slid over one another and fixed by tapering the end of one element and tapering off the end of the other element.

Thus, when the inner tubular element 2 is composed of the individual segments, the outer tubular element 3 can be placed over it, for example also by extrusion, or by poaching the prefabricated outer tubular element over it.

At the location of the connections 8 between the segments, the outer tube-like element 3 is preferably connected to the inner tube-like element 2, so that a good and reliable fixation of the connections 8 between the segments is obtained. The connection 9 of the outer tube-like element with the inner tube-like element 2 at these locations can be effected, for example, by ultrasonic welding. The position where the welds are to be applied, ie the position of the joints 8, can be easily determined by measuring.

As shown in Fig. 1, the distal last segment 7 of the inner tubular element 2 extends beyond the end 10 of the outer tubular element 3. This end 10 is chamfered so that it gradually decreases towards the distal end Has. The chamfered end is circumferentially connected to the last segment 7, for example also by ultrasonic welding, while gluing is also possible.

The catheter 1 can be manufactured with a small diameter and a very small wall thickness. For example, the diameter may be less than 1 mm while the wall thickness may be less than 0.1 mm. The wall thickness of the inner tube-shaped element and the outer tube-shaped element may each be less than 0.05 mm. The invention thus makes a catheter with such a small reachable range which nevertheless has very reliably varying properties along the length, for instance a stiffness varying over the length.

Stiffness varying along the length is desirable, particularly with catheters of such small dimensions. When inserting the catheter, the front end, indicated at 14 in Fig. 2, must be flexible so that it can easily follow the bends in a blood vessel 12 and be accurately positioned at the desired location in the body.

During insertion, a pushing force is indicated on the proximal end, which is indicated by the arrow 13 in Fig. 2. Thin and thin-walled catheters, of course, have a quick tendency to buckle, which complicates, if not impossible, insertion. By now designing the catheter with a maximum stiffness near the proximal end, by applying according to the invention over that part segments of the inner tubular element which are made of rigid material, this part of the catheter obtains the desired properties in order to be able to insert it properly, by pushing against the proximal end.

Also, during insertion, the catheter is often rotated about its longitudinal axis by rolling the distal end between the fingers. It is also desirable that the catheter near the proximal end be sufficiently rigid, in particular torsionally rigid, in order to be able to transmit the resulting force.

For certain applications, a reinforcement layer can be applied between the outer and inner tubular element, preferably of woven or wound filaments. For example, through a suitable weaving pattern, the torsional stiffness can be greatly increased, while, moreover, the bursting pressure of the catheter is increased.

Claims (9)

A catheter comprising at least one inner tube-like element and an outer tube-like element over it, the inner tube-like element being composed of a number of contiguous separate tube-like segments with different properties. Catheter as claimed in claim 1, wherein the flexibility of the segments increases from the proximal to the distal end and the outer tube-like element itself has a low bending stiffness. Catheter as claimed in claim 1 or 2, wherein the successive segments are connected to each other. Catheter as claimed in claim 3, wherein the ends of successive segments are complementarily beveled and mutually slidly connected to each other. Catheter as claimed in claim 3, wherein the outer tubular element is also connected to the inner tubular element at the location of the interconnections of the segments. Catheter according to any of the preceding claims, wherein the distal last segment extends beyond the end of the outer tubular member and the end has a gradually decreasing wall thickness to zero and is circumferentially connected to the last segment. Catheter as claimed in any of the foregoing claims, wherein a reinforcing layer is arranged between the outer and the inner tubular element. Catheter as claimed in claim 7, wherein the reinforcing layer is a filament woven or wound layer. Catheter as claimed in claim 8, wherein the reinforcing layer is at least partly embedded in the inner tube-shaped element.