NL2011364C2

NL2011364C2 - Catheter for use in endovascular intervention.

Info

Publication number: NL2011364C2
Application number: NL2011364A
Authority: NL
Inventors: Johnny Johannes Dobbelsteen; Helene Claire Clogenson
Original assignee: Univ Delft Tech
Priority date: 2013-08-30
Filing date: 2013-08-30
Publication date: 2015-03-03

Description

Catheter for use in endovascular intervention

The invention relates to a catheter for use in endovascular intervention comprising a shaft with a proximal end for handling the catheter and a distal end which is provided with at least two deflectable segments which are actuable to accommodate the catheter to a patient's vascular anatomy, wherein the segments are each featured with a group of preselected parameters comprising a length of the segment, a position of the segment along the shaft, and a maximum radius of curvature of the segment. EP-A-0 605 796 discloses a steerable catheter comprising an elongated flexible tube with a first section and a second section, having means for bending the first section of the elongated flexible tube and means for bending the second section of the elongated flexible tube wherein the first section bending means operates substantially independently of the second section bending means. The bendable first section and bendable second section are applied in order to promote the ease of navigation of the steerable catheter, for which purpose the first and second sections are bendable along a continuum of possible shapes without any preference for a particular shape.

Endovascular intervention is a type of minimally invasive intervention, which is used for diagnostics or treatment of various vascular diseases and disorders e.g. atherosclerosis and aneurysms. Compared with conventional open surgery, it presents several advantages for the patient such as less risk of infection, less pain, and shorter recovery time. However, it is more difficult to perform and it requires a longer learning curve, as interventionalists do not have a direct vision of the instrument and, using two-dimensional projection x-ray guidance, need to learn to manipulate long, thin and flexible instruments that are inserted percutaneously into the blood vessels .

Catheters are the basic tools for endovascular intervention. They are used to reach the target in the vasculature as well as to perform focused arteriography, drainage, or delivery of therapeutic devices. Selective catheters typically have fixed and unchangeable distal shapes and are specifically-designed to navigate branches in the vascular tree. There is a multitude of head shapes available on the market. Some selective catheters are designed for general purpose while other have a specific target artery or group of arteries [1]. Therefore, the instruments need to be exchanged frequently to replace tip shape or size. It has been estimated that physicians perform on average twenty extractions and insertions of catheters, guidewires, and sheaths, per procedure [2]. This repeated extraction and insertion increases the risk of infection and embolization, increases procedure time and radiation dose, waste consumables, and it causes easily interventionalists to feel tired [3, 4]. Moreover, the control of the tip gradually decreases as the instruments are manipulated to reach distant locations or pass through lesions [1]; therefore, the instrument may be more likely to deviate from the desired path into side branches and some locations can only be reached with a low success rate [3]. Another drawback of the technique is that endovascular interventions are monitored by an angiography suite where x-ray fluoroscopy, angiography, and digital subtraction angiography (DSA) are used to visualize endovascular devices and iodine-based contrast media in the vessel lumen. Fluoroscopy-angiography gives high spatial resolution, and high achievable frame rates. However, the anatomy is only visible when nephrotoxic and iodine-containing contrast media are administrated to the patient (angiography and DSA), yielding a risk of contrast - induced nephropathy or potential life threatening anaphylactic reactions [5, 6]. Moreover, these two-dimensional projection images do not provide depth perception. Therefore, while manipulating the instruments in three-dimensions, the operators have to rely on two-dimensional angiographic images previously and on three-dimensional mental images of the anatomy [7].

It is therefore an object of the invention to provide a catheter resolving one or more of the above-mentioned problems .

It is an object of the invention to provide a catheter, the use of which results in reduced handling during an intervention .

It is a further object of the invention to reduce the number of instrument exchanges during the navigation of a catheter in an interventional procedure.

It is another object of the invention to reduce the required amount of contrast fluids that must be used for navigating the catheter.

It is another object of the invention to enable the navigation of a catheter in an interventional procedure which may be completed using only one catheter.

These and other objects of the invention are attainable with a catheter having the features of one or more of the appended claims.

Essentially the catheter of the invention has the feature that the actuable deflectable segments with the said preselected parameters are arranged such that a first actuation of the at least two deflectable segments causes the catheter to assume a first preferred shape selected from a group of preferred shapes, and a second actuation of the at least two deflectable segments causes the catheter to assume a second preferred shape selected from the group of preferred shapes, wherein the first shape differs from the second shape.

With the term 'preferred shape' as used herein, it is expressed that when the catheter of the invention is moved to assume a preferred shape, this preferred shape can easily be maintained and corresponds essentially with one of the shapes of existing catheters that an interventionist uses sequentially when navigating through a vascular tree of a patient. Any such preferred shape is preferably realized by arranging that the catheter is embodied with end stops, wherein each end stop corresponds with a preferred shape. In contrast thereto, when the catheter assumes an 'unpreferred shape', the catheter runs free from any end stop, thus requiring continued manipulation of the catheter to maintain such an unpreferred shape.

The said end stop can be arranged by any suitable means, and may for instance be embodied by including stops for the wires that connect the segments of the catheter with the handle, or may for instance be embodied by a proper selection of the length and shape of the respective segments, the position of the segments along the shaft, and the maximum radius of curvature of each segment.

By arranging that each of the preferred shapes of the group of preferred shapes identify or essentially resemble existing catheter shapes of known design, the interventionist applying the catheter of the invention is allowed to work with what is virtually a known instrument, avoiding the need to pass through a learning process and become familiar with the catheter of the invention. Nevertheless the catheter of the invention avoids the need to be frequently exchanged to replace tip shape or size, since this can be done simply by switching between the first preferred shape and the second preferred shape of the group of available preferred shapes without the need of retracting the catheter and replacing it by another catheter as is required in the prior art. Consequently also the use of contrast fluid to assist in navigating through the vascular tree can be tremendously reduced.

Preferably during the transition from the first preferred shape to the second preferred shape the catheter passes through a series of unpreferred shapes intermediate between the first preferred shape and the second preferred shape.

Although the invention is sufficiently clearly and completely disclosed in the above to enable the skilled person to carry out the invention, the invention will hereinafter further be elucidated with reference to a discussion of a prototype design catheter according to the invention and a drawing pertaining to selected figures of this prototype design catheter .

Catheter design

The shaft of the prototype design catheter of the invention consists of a 120cm long tube of polyether ether ketone (PEEK), a very stiff polymer material with high tensile strength, torquability, and pushability. This biocompatible polymer is used for medical applications, and can be autoclaved or sterilized via ethylene oxide. This tube presented an inside diameter (ID) of 1mm, and an outside diameter (OD) of 1.8mm. To mimic the shapes of three conventional selective catheters (Fig 1), two deflectable segments are applied at the extremity of the prototype: a distal one, at the very tip of the instrument, and a proximal one. This segmented structure •' solution is preferred in order to achieve satisfactory tor-quability, acute bending capability and to ensure that the segments bend in the plane.

The segments of the catheter are provided with links or hinges that are manufactured by laser cutting technology. Adjacent hinges are interlocked. Based on the geometries of the three conventional selective catheters (Fig 1) the lengths, locations, and bending angles of both segments of the steerable catheters are defined (Fig 2). As the segments of the prototype bend in the plane, the geometry of each curve is defined for its right and left side. The lengths of a single hinge of the distal and proximal section are in this example 1mm and 3mm respectively. The maximum relative angle between two links is defined as 11.6°, in order to ensure that a guidewire can be advanced through the catheter lumen without obstruction. The actuation of each deflectable segment is possible by the use of two 0.12 mm diameter Dyneema® pull wires, of which the middle is attached distally to each section. Both wires are placed in the same two grooves (width=0.3mm; depth=0.25mm), which are milled diametrically opposed along the PEEK tube constituting the catheter shaft and segments. Each wire is placed in one groove, attached above the segment by looping in the circumferential groove and application of a small amount of adhesive and then going down the shaft in the opposed grooves. Therefore, one wire is attached to each segment and pulling on one or the other end of the wire results in bending the corresponding segment to one side or the other. A nitinol rod is placed in an additional groove made along the proximal segment. The rod provides an additional stiffness assisting the control of both sections independently. Shrink sleeves of polyethylene (PE) are placed around the PEEK tube and maintains the wires and the nitinol rod in their own grooves .

Handle design

The handle (Fig 3) enables the manipulator to actuate the deflectable segments by applying tension to the appropriate pull-wires. The handle presents two sliders, each driving. the two opposite end of the wires of a single segment. For each section, one end of the wire is directly attached to the slider while the second end is first passed over a wire pulley placed at the back of the handle. Therefore, for a given segment, translating the slider backward actuates the end of the wire that is directly attached to it. Pushing the slider front actuates the second wire end, which is passed over the pulley. Actuating the proximal segment alters the lengths of the pull wires of the distal one. Therefore, a compensating mechanism is used to ensure that the segments can be actuated independently with the handle: one slider is placed on top of the other one. Consequently, the slider placed on top moves along with the bottom slider, while the movement of the top slider does not influence the bottom one. The pull wires of the distal segment are attached to the top slider, so that its wires are automatically adjusted when the proximal one is actuated.

Both sliders are designed as rings so that it is possible to drive the segments for any position of the handle.

Two rubber rings are placed between the sliders and the handle body and induce friction. This holding mechanism ensures that the shape of the catheter stays fixed when the sliders are released.

The designed 120cm long shapeable catheter presents an inside diameter of 1mm, allowing a 0.035" guidewire to be exchanged. A length of 120cm makes possible to reach various parts of the vasculature.

Two Steerable Segments

The shapeable catheter presents two steerable sections that bent in the same plane. The proximal segment is stiffer than the distal one. Therefore, it is possible to independently steer the distal segments for small angles. To accommodate the situation that the distal segment is actuated to present bigger angles, and to prevent that the proximal one will be slightly curving along, a correction is carried out by actuating the opposite wires on of the proximal segment. In this way it is possible to actuate both sections independently.

With the design prototype catheter of the invention it is possible to mimic the three selective catheter shapes by-actuation of one or two deflectable segments. The maximum angle of the proximal segments is designed to match the required angles to form the target shapes, notably the RDC and SIM2 shapes shown in figure 1. The shape of the BER catheter is mimicked by actuating the distal segment only.

The shapeable catheter of the invention is· designed and assembled to mimic several conventional catheters and to perform navigation tasks. The prototype presented stiff shape at the tip when actuated. This stiffness is of interest in the case of an intervention that requires a good anchorage at the entrance of a target artery when an intervention has to be performed further down in that branch. This may for instance be the case of angioplasty, stenting, or placing a coil to stop a bleeding. The device can then be locked in a particular shape at the entrance of a major target artery and provide anchorage and support for other instruments. Therefore, the in-terventionalist does not have to worry that the support is lost while he/she is working further down the vessel.

Reference signs:

Fig. 2: A = Left ( + ) B = Right (-) C = Tip D = Distal segment E = Proximal segment A1: 8 links with 9 hinges B1: 8 links with 9 hinges A2 : 1 link B2: 6 links with 7 hinges A3: 19 links with 20 hinges Fig. 3: 1 = Top slider (distal) 2 = Bottom slider (proximal) 3 = Wire clamps 4 = Wire pulleys 5 = Catheter clamp 6 = Lumen

References [1] Schneider, P., 2008, Endovascular Skills: Guidewire and Catheter Skills for Endovascular Surgery, Informa Healthcare, New York [2] Bakker, N.H., Tanase, D., Reekers, J.A., and Grimbergen, C.A. , 2002, "Evaluation of Vascular and Interventional Procedures with Timq-Action Analysis: a Pilot Study," Journal of vascular and interventional radiology, 13 (5) , pp. 483-488.

[3] Fu, Y., Liu, H., Huang, W., Wang, S., and Liang, Z., 2009, "Steerable Catheters in Minimally Invasive Vascular Surgery, " International journal of medical robotics and computer assisted surgery, 5(4), pp. 381-391.

[4] Nordon, I.M., Hinchliffe, R.J., Holt, P.J., Loftus, I.M., and Thompson, M.M., 2010, "The Requirement for Smart Catheters for Advanced Endovascular Applications," Proceedings of the Institution of Mechanical Engineers, Part H, Journal of engineering in medicine, 224(6), [5] Sharma, P., Kyriakides, C., 2007, "Surveillance of Patients Post-Endovascular Aneurysm Repair," Postgraduate medical journal, 83(986), pp. 750-753.

[6] http ://Www.Drugs . Com, http ://www. drugs .com/pro/visipaque.html [7] Razavi, R., Hill, D.L., Keevil, S.F., Miquel, M.E., Mu-thurangu, V., Hegde, S., Rhode, K., Barnett, M., van Vaals, J., Hawkes, D.J., Baker, E., 2003, "Cardiac Catheterisation Guided by Mri in Children and Adults with Congenital Heart Disease," Lancet, 362(9399), pp. 1877-82.

Claims

A catheter for use in an endovascular intervention comprising a shaft with a proximal end for handling the catheter and a distal end which is provided with at least two adjustable segments which are operable to accommodate the catheter to a vascular anatomy of a patient, wherein the segments are each provided with a group of preselected parameters comprising a length of the segment, a position of the segment along the shaft, and a maximum radius of curvature of the segment, characterized in that the operable adjustable segments with said predetermined parameters are arranged such that a first actuation of the at least two adjustable segments causes the catheter to assume a first shape selected from a group of preferred shapes, and a second actuation of the at least two adjustable segments causes the catheter to have a second takes shape selected from the group of preference rs forms, the first form deviating from the second form.

Catheter as claimed in claim 1, characterized in that the catheter is provided with end plugs, wherein each end plug corresponds to one preferred form selected from the group of preferred forms.

Catheter as claimed in claim 1 or 2, characterized in that said end plugs are made by receiving stops for the wires connecting the segments of the catheter with a handle provided at the proximal end of the catheter, or being designed by choosing the length and shape of the respective segments, the position of the segments along the shaft, and the maximum radius of curvature of each segment.

Catheter as claimed in any of the claims 1-3, characterized in that during the transition from the first form to the second form the catheter is adjusted by a series of non-preferred forms that lie between the first form and the second form.