Patent Application
20050283179
The present invention pertains generally to medical devices that are to be advanced into the vasculature of a patient. More particularly, the present invention pertains to introducer sheaths. The present invention is particularly, but not exclusively, useful for introducer sheaths having variable rigidity with increasing flexibility in the distal direction.
Introducer sheaths, as the name suggests, are medical devices that are used to establish extracorporeal access into the vasculature of a patient. More specifically, introducer sheaths are used to effectively establish an access port into the vasculature through which other interventional medical devices can be subsequently introduced and withdrawn. Typically, during a particular medical procedure, several different types of medical devices may need to be inserted into and withdrawn from the vasculature through the same introducer sheath.
In order for an introducer sheath to effectively perform its intended purpose, it needs to exhibit several specific structural and functional capabilities. For one, the introducer sheath must provide a passageway of sufficient size to accommodate the insertion and withdrawal of medical devices through the passageway. Also, for ease of use, the preference here is for a sheath wherein the percentage of cross sectional area available for use as a passageway is maximized. On the other hand, the overall outside diameter of the sheath must not be too large.
With the above in mind, the amount of material that can be used for constructing the structure of the sheath should be minimal. This raises a competing concern in that, on the one hand, the structure of the sheath surrounding its passageway needs to be small. On the other hand, it must also have sufficient strength to maintain the integrity of the device during its use. Specifically, the sheath must be capable of resisting collapse and withstanding any tendency to kink. Further, it is necessary for the introducer sheath to have sufficient flexibility to allow it to be properly advanced and positioned in the vasculature. Ideally, the introducer sheath will also have variable flexibility along its length, with the most flexibility being at its distal end.
Insofar as strength capabilities for an introducer sheath are concerned, the incorporation of a tube-like structure that is made of a high strength material, such as stainless steel, is preferable. Specifically, a hypotube of a type well known in the pertinent art is quite suitable for this purpose. Hypotubes, however, are very stiff and inflexible.
In light of the above, it is an object of the present invention to provide an introducer sheath that has the “hoop strength” needed to resist a collapsing or kinking of the sheath during its use. Another object of the present invention is to provide an introducer sheath that has a variable flexibility along its length for effectively positioning the sheath into the vasculature of a patient. Still another object of the present invention is to provide an introducer sheath that is relatively simple to manufacture, is easy to use and is comparatively cost effective.
An introducer sheath in accordance with the present invention includes an elongated hollow hypotube which is coated with a flexible polymer material. In particular, the hypotube is formed with a spiral cut that extends the length of the tube from its proximal end to its distal end. Importantly, the spiral cut also extends completely through the hypotube from its outer surface to its inner surface. With this structure, the spiral cut can be characterized at any axial location along the hypotube by a pitch angle (α). Specifically, the pitch angle (α) is measured between the axis of the hypotube and the inclination of the spiral cut at a location. Functionally, the pitch angle (α) is indicative of the flexibility of the hypotube at each particular location.
As an alternative to the above description, the introducer sheath of the present invention can be described as being a ribbon-like band that is configured as a helical spiral. In this description, the spiral band is positioned around an axis, at a predetermined radial distance from the axis. One edge of the band is juxtaposed at an extremely short axial distance from its other edge to form a flexible tube. As a practical matter, this axial distance is determined by the gap width of the spiral cut mentioned above in the first description of the introducer sheath.
In line with either of the descriptions given above for the introducer sheath, the result is a tube (hypotube) that has a proximal end and a distal end with a lumen extending through the tube from end to end. Also, in each case, a flexible polymer material is positioned on the outer surface of the band as a coating that will provide a substantially fluid-tight condition for the lumen and give the introducer sheath a lubricious quality that will facilitate its advancement into the vasculature of a patient.
As an additional feature for the present invention, the polymer coating on the hypotube may be formed with an inflation lumen that extends from the proximal end of the hypotube to substantially the distal end thereof. Further, a balloon can be mounted on the hypotube at its distal end and connected in fluid communication with the inflation lumen. Still further, a fluid pump may be connected in fluid communication with the inflation lumen at the proximal end of the hypotube for selectively inflating the balloon.
Insofar as the spiral cut is concerned, it is an important aspect of the present invention that the pitch angle (α) can be varied along the length of the introducer sheath. Preferably, variations in the pitch angle (α) will be in a range between forty-five and ninety degrees. With this in mind, the introducer sheath may be characterized as having a plurality of sections, wherein the pitch angle (α) has a respective average value for each of the different sections. For example, for a sheath having three sections, there may be a first pitch angle (α1) having an average value equal to approximately seventy-five degrees in a first section, a second pitch angle (α2) having an average value equal to approximately eighty degrees in a second section, and a third pitch angle (α3) having an average value equal to approximately eighty-five degrees in a third section. In this example, the introducer sheath would exhibit greater flexibility wherever the pitch angle is greater.
In the manufacture of the introducer sheath, the spiral cut is preferably accomplished using an industrial laser cutting system. Also, the hypotube is preferably made of either stainless steel or NITINOL. Further, the flexible polymer coating is preferably a PEBAX type material.
The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:
Referring initially to
The construction of the introducer sheath 10 will, perhaps, be best appreciated with reference to
As will be appreciated by cross-referencing
Referring to the
Preferably, the spiral cut 40 is made using well known industrial laser cutting techniques. The spiral cut 40, however, may be made by several other means well known in the pertinent art. In any event, during manufacture, the pitch angle (α) and the width “w” can be established at locations in sections along the length of the hypotube 20 (e.g. sections 34, 36 and 38) to give it the desired flexibility. For example, the pitch angle (α) may be varied within a range between forty-five and ninety degrees and have a respective average value for each of the sections 34, 36 and 38. Again, by way of example, the pitch angle (α1) in section 34 may have an average value equal to approximately seventy-five degrees while pitch angle (α2) in section 36 has an average value equal to approximately eighty degrees in a second section. Pitch (α3) in section 38 may then have an average value equal to approximately eighty-five degrees in a third section. The hypotube 20 can then be covered with the polymer coating 28 to provide a fluid-tight condition for the central lumen 26 and give the introducer sheath 10 a lubricious quality that will facilitate insertion of the sheath 10 into the vasculature of a patient.
The consequence of the present invention is an introducer sheath 10 that, due to the structural qualities of the hypotube 20, has sufficient strength to resist collapse and avoid kinking. At the same time, due to the geometry of the spiral cut 40, the sheath 10 has the desired degrees of variable flexibility. In combination, this provides an introducer sheath 10 having the different bending characteristics that are substantially shown in
While the particular Introducer Sheath as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.
