Surgery – Diagnostic testing – Flexible catheter guide
Reexamination Certificate
1999-01-14
2001-02-06
O'Connor, Cary (Department: 3736)
Surgery
Diagnostic testing
Flexible catheter guide
C600S485000, C600S505000, C600S561000
Reexamination Certificate
active
06183424
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a pressure measuring guide wire comprising an elongated flexible shaft with a proximal portion, a distal portion, a lumen extending through the shaft, wall means surrounding said lumen, and aperture means for entry of a pressure medium into the lumen.
Intracoronary pressure recordings give valuable information to the cardiologist to assess both coronary and myocardial flow reserve and collateral blood flow.
The problem of pressure measuring guide wires is to provide an uninterrupted lumen throughout the shaft which has to be highly flexible to conform with the tortuous pathways of the blood vessels, simultaneously, the shaft must have a reasonably high stiffness to assure pushability and torque transmission thereto; and furthermore, the shaft must have a very good kink resistance to avoid the risk of constrictions resulting in modification of the advance of pressure waves through the lumen.
Current pressure measuring guide wires are made of a plastic tube and a stiffening wire. This is, however, very costly and leads to constrictions in the lumen which obstruct the advance of pressure waves in the lumen.
Another approach is shown in the document EP-A1-0419277 which describes a guide wire for use in measuring a characteristic of liquid flow in a vessel comprising a flexible elongate element in the form of a tube with a core wire provided therein the distal extremity of which is tapered and extends beyond the distal end of the tube. The tapered extremity of the core wire extends into a coil spring which is soldered to the tube. The coil spring is formed of two parts which are screwed together and the spring is bonded to the core wire by solder at the region where the two portions of the coil spring are screwed together. A safety wire extends from the joint of the two coils to the distal extremity of the coil spring where it is secured to a transducer carried by the distal end of the coil spring. Front and rear contacts are provided on the transducer and are connected to a two conductor wire which extends rearwardly and interiorly of the coil spring and further extends into the tube between the core wire and the interior of the tube to get out of the tube for connection to a male connector. According to a variant, an insulating sleeve may form a tight fit with the exterior surface of the core wire and it may also fit within the tube to insulate the core from the tube so that the core and the tube and core may serve as separate and independent electrical conductors.
It is an object of this invention to improve over the cited art by means of a pressure measuring guide wire which is easy and inexpensive to manufacture, which is highly versatile while having excellent qualities of pushability and resistance to kinking, and which allows a smooth advance of pressure waves through the lumen.
SUMMARY OF THE INVENTION
Towards fulfilling of these and other objects, the invention provides for a pressure measuring guide wire comprising an elongated flexible shaft with a proximal area, a distal area, a lumen extending through the shaft, wall means surrounding said lumen, and aperture means for entry of a pressure medium into the lumen, wherein said wall means have a first portion of length having a first resistance to kinking, a second portion of length having a second resistance to kinking, said second resistance to kinking being smaller than said first resistance to kinking, and wherein coil means are supporting said second portion of length. Accordingly, it becomes possible to modulate the resistance to kinking as a function of the structural organization for the pressure medium entry into the lumen. The wall thickness may be selected at will, whereby the shaft can be made flexible and stiff enough to be pushed. The resistance to kinking can be practically constant and the risk of constrictions due to kinking is eliminated. A stiffening wire is no more needed, and there is a better frequency behaviour for the fluid medium.
The first portion of length or the second portion of length may be in the distal area of the shaft, making it possible to select at will the configuration of the supporting coil means.
Where the first portion of length has a first thickness and the second portion of length a second thickness smaller than the first one, with the first portion of length having a plurality of slots formed therein for entry of the pressure medium, the mere choice of thickness allows mastering the difference in resistance to kinking due to the presence of the slots.
Within this frame, the first portion of length may have a first outer diameter and the second portion of length may have a second outer diameter smaller than the first outer diameter, whereby the coil means may surround the second portion of length. In this configuration, the coil means and diameters may be easily chosen to have the coil means in flush alignment with the first outer diameter, for having an overall outer diameter constant and reduced friction upon travelling through the blood vessels. And to assure simple positioning of the coil means on the second portion of length, this second portion of length may be preceded proximally by a third portion of length having a third outer diameter larger than said second outer diameter, with the coil means surrounding the second portion of length between said first and third outer diameters. In that configuration the coil means may also be in flush alignment with the first outer diameter for the same reason of diameter constancy and friction reduction.
Still within this frame, the first portion of length may have a first inner diameter and the second portion of length may have a second inner diameter larger than the first inner diameter, whereby the coil means may be located within the second portion of length. In this configuration, the coil means and diameters may also be easily chosen to have the coil means in flush alignment with the first inner diameter for having an overall outer shaft surface which is homogeneous while the inner diameter of the shaft remains constant.
In any of the arrangements with the first portion of length in the distal area of the shaft and with slots formed in the first portion of length, some of the slots may be proximal of the first portion of length with some other slots being distal of the first portion of length, thereby avoiding too many holes on the same diameter in order to minimize the risk of kinking resistance reduction in that area.
Where the second portion of length has a plurality of elongated slots formed therein for entry of the pressure medium and the coil means are located inside the shaft and extend at least under the slots, a very small thickness of the wall may be achieved all along the shaft, including the weakened area of slot location which is supported by the coil means which avoids the risk of kinking in that delicate area. And as the slots are fully supported by the coil means, they can be located at the same level along the second portion of length. To facilitate entry of the pressure medium, the coil means may have adjacent windings which are spaced apart from one another extending at least under the slots.
In order to stiffen the coil means without interfering with the shaft, core means may extend through the coil means. Where such core means have a proximal portion for longitudinal abutment against a proximal end of the coil means and a distal portion for longitudinal abutment with a distal end of the coil means, a stress free assembly is achieved which stiffens the turns of the coil means and which leaves the shaft lumen free of any obstruction proximally of the coil means. The core means may also have their proximal portion integral with a wire which extends proximally along and out of the lumen of the shaft. In that case, the supporting coil may be placed under the slots only for insertion of the guide wire to assure the required resistance to kinking. During insertion, the wire extending the core also has some stiffening effect for the shaft and improves its pusha
Messal Todd P.
O'Connor Cary
Schneider (Europe) A.G.
Wingood Pamela
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