Patent Description:
In clinic, in order to improve a success rate of a guide wire passing through blood vessels during an interventional surgery, the microcatheter is usually used in combination with the guide wire. The microcatheter can provide support to the guide wire and provide a passage for the guide wire to pass through the blood vessels.

According to the statistics of existing interventional treatment cases, it is found that bifurcation lesions are relatively more common, mainly occurring in the main branch and/or branch of the coronary artery. The branch of the coronary artery, that is, the bifurcation appearing at an end of the main branch, has a different bifurcation angle. The existing microcatheter cannot smoothly enter the branch of the coronary artery after entering the main branch of the coronary artery, which affects the guidewire, a dilatation balloon catheter or a stent system to reach the lesion site, resulting in the severe consequences of the interruption or failure of the interventional surgery. <CIT> discloses a microcatheter with tubular structure.

In order to solve the above discussed technical problem in the prior art that the microcatheter can't help the guide wire to reach the bifurcation lesion of the coronary artery, which affects the normal operation of interventional operation, the invention provides an improved microcatheter with side branch access capability.

To achieve the above objectives, the present invention employs the following technical solutions:
The present invention provides a microcatheter, with tubular structure, comprising a catheter body, a sharp portion disposed at a distal end of the catheter body; wherein the catheter body has a proximal end and a distal end, the catheter body comprises:.

Further, a ratio of a length of the part of the spring layer which is not wrapped by the braid to the length of the part of the spring layer which is wrapped by the braid is from <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>:<NUM>, more preferably <NUM>:<NUM>.

Further, a rigidity of the intermediate layer is greater than the rigidity of the inner layer and the outer layer; the outer layer is made of thermoplastic polymer, and the thermoplastic polymer of the outer layer is embedded in the intermediate layer so as to cover the intermediate layer.

Further preferably, the spring layer is a spring tube, a hollow skeleton tube or a braided tube.

Further, an outer diameter of the spring layer decreases gradually from the proximal end of the catheter body to the distal end of the catheter body.

Further, the spring layer comprises spiral winding flat filaments.

Further, the braid comprises a plurality of winding filaments.

Further preferably, the braid comprises round filaments and flat filaments.

Further preferably, the braid extends spirally around the spring layer in a direction of the longitudinal axis of the catheter body.

Further preferably, the braid is formed by interlacing a plurality of filaments, and at least one of the filaments protrudes outwardly from other filaments so that a helical convex rib can be formed on an outer surface of the braid.

Further, the rigidity of the outer layer decreases gradually from the proximal end of the catheter body to the distal end of the catheter body.

Further, the outer diameter of the outer layer decreases gradually from the proximal end of the catheter body to the distal end of the catheter body.

Further, the thickness of a wall of the outer layer decreases gradually from the proximal end of the catheter body to the distal end of the catheter body.

Further, the spring layer is a tapered spring whose diameter decreases gradually from the proximal end to the distal end of the catheter body, and the spring layer comprises a distal section, a proximal section, a gradational section connected between the distal section and the proximal section, and wherein a pitch of the distal section and the proximal section is constant, and the pitch of the distal section is greater than the pitch of the proximal section, and the pitch of the gradational section tends to increase in a direction from the proximal end to the distal end.

Further, the pitch of the distal section is 180PPI, the pitch of the proximal section is 80PPI, and the pitch of the gradational section gradually transfers from 80PPI to 180PPI from the proximal end to the distal end.

Further, the thickness of the wall of the spiral corrugated tube tends to decrease from the proximal end to the distal end along the direction of the longitudinal axis of the catheter body, and a distance between two adjacent wave crests tends to increase from the proximal end to the distal end along the direction of the longitudinal axis of the catheter body.

Further, the part of the spring layer which is not wrapped by the braid is provided at a position at a distance of <NUM>-<NUM> from a tip of the sharp portion.

Further, the microcatheter further comprises:.

Further, at least one of the spring layer and the braid is made of stainless steel or nickel-titanium alloy.

Further, the part of the spring layer which is not wrapped by the braid is bent at a certain angle, such that the sharp portion of the distal end of the catheter body can be guided into an entrance of a side branch artery.

Further preferably, the microcatheter further comprises:.

Further, the portion of the spring layer which is not wrapped by the braiding can be bent within a range of about <NUM>°to about <NUM>°with respect to the longitudinal axis of the catheter body.

By employing the above technical solutions, the present invention has the following technical effects compared with the prior art:
The catheter body of the microcatheter of the present invention is provided as a multilayer structure, and the braid is only wrapped around the proximal end, near the outer wall of the spring layer; the part of the spring layer not wrapped by the braid can be bent at a corresponding angle to adjust to the angle between the main branch and the branch of the coronary artery, to make sure that the microcatheter can reach the bifurcation lesions of the coronary artery; besides, the rigidity of a pushing section of the catheter body is greater than the rigidity of a shaping section of the catheter body, thereby, the pushing section of the catheter body can provide a certain support force and a recoil force at the proximal end of the shaping section to improve the torque control force of the microcatheter, so that the catheter body has enough torsional pushing force and supporting force to improve the traversing, traceability and flexibility of the microcatheter effectively.

The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present disclosure, and, together with the description, serve to explain the principles of the present invention.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

It will be further understood that the terms "comprises" and/or "comprising," or "includes" and/or "including" or "has" and/or "having" when used herein, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, "around", "about" or "approximately" shall generally mean within <NUM> percent, preferably within <NUM> percent, and more preferably within <NUM> percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term "around", "about" or "approximately" can be inferred if not expressly stated.

As used herein, the term "plurality" means a number greater than one. And the direction term "proximal" is defined as a direction close to the operator during the operation, "distal" is defined as the direction away from the operator during the operation.

Hereinafter, certain exemplary embodiments according to the present disclosure will be described with reference to the accompanying drawings.

As shown in <FIG>, the embodiment of the present invention provides a tubular structure of a microcatheter <NUM>, comprising a catheter body <NUM> and a sharp portion <NUM> disposed at a distal end of the catheter body <NUM>. The catheter body <NUM> extends longitudinally along an axis L, and herein the axis L is referred to as a longitudinal axis of the catheter body <NUM>. The sharp portion <NUM> may be made of a mixture of tungsten powder (<NUM>%) and a thermoplastic elastomer material, and may have sufficient softness and flexibility to prevent damage to a lining of the blood vessel with which it is in contact.

The catheter body <NUM> has a pushing section <NUM> at its proximal end and a shaping section <NUM> at its distal end along the longitudinal axis L thereof. The shaping section <NUM> can be pre-shaped by bending without bending deformation under a suitable external force, and can maintain the preformed shape after the external force is removed, so that a portion of the shaping section <NUM> can be shaped at a certain angle along the longitudinal axis L of the catheter body <NUM>, and the shaped microcatheter <NUM> can generate better supporting force for helping the guide wire enter a severely tortuous or calcified lesions smoothly.

Meanwhile, the rigidity of the pushing section <NUM> is greater than that of the shaping section <NUM>, thus, the pushing section <NUM> can provide a certain supporting force and recoil force near to the shaping section <NUM> to improve the torque control force of the microcatheter <NUM> and provide the catheter body <NUM> sufficient torsional pushing force and supporting force, so that the traversing, traceability and flexibility of the microcatheter <NUM> can be improved effectively.

Moreover, the microcatheter <NUM> further comprises a needle base <NUM>, which is arranged at the proximal end of the catheter body <NUM>. The needle base <NUM>, for example, may be made of polycarbonate, polyester, polyamide and polyimide, and can be adapted to be bonded to a standard luer connector. A connecting member <NUM> is provided between the needle base <NUM> and the catheter body <NUM>. The connecting member <NUM> may be made of an elastomeric material having a rigidity (but the rigidity is lower than the rigidity of the catheter body <NUM>) to cause a soft/hard transition between the needle base <NUM> and the catheter body <NUM>.

The operator usually controls the microcatheter by rotating the connecting member <NUM> during the operation. In the embodiment of the present invention, based on the A Type Shore Hardness Tester, the rigidity of the connecting member <NUM> may be from 15A to 75A, from 25A to 65A or from 35A to 55A to facilitate the operator's operation. The Shore Hardness Tester adapted is recorded in the American Society for Testing and Materials (ASTM) Standard D-<NUM>. The ASTMD-<NUM> Hardness Tester applies a predetermined amount of force to a sample in a consistent manner and measures the rigidity based on a depth of an indentation caused by the applied force. According to the "A" type test set by a scale, a hardened steel bar with a diameter of <NUM> to <NUM> and a truncated cone with a cone angle of <NUM>° are applied to make the indentation.

As shown in <FIG>, in the actual application, the doctor can use a puncture needle to make a part of the shaping section <NUM> to bend at a certain angle along the longitudinal axis L of the catheter body <NUM> according to the actual demand. For example, the bending angle α of the shaping section <NUM> may be similar to the angle of a starting section of the blood vessel, wherein α may range from about <NUM>° to about <NUM>°, about <NUM>° to about <NUM>°, about <NUM>° to about <NUM>°, about <NUM>° to about <NUM>°, about <NUM>° to about <NUM>°, about <NUM>° to about <NUM>°, about <NUM>° to about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about120° or about <NUM>°. Besides, depending on an anatomy requirement of a specific size of a branch entrance, the shaping section <NUM> can also be directly bent into a J-shaped elbow whose bend radius should not be greater than the diameter of the blood vessel; the shaping section <NUM> can also be bent into S-shaped or semi-circular shape. Generally, the shaping section <NUM> may be formed in a variety of curved shapes, including flat, simple curves, complex curves, reverse curves or hyperbolas. A length of the curved section may vary and may include different lengths of the shaped section. The force can be applied in a variety ways, such as through the guide wire that can be inserted into the lumen of the inner layer.

Based on clinical needs, in some embodiments, the shaping section <NUM> may be shaped to have a varying bend radius to form a multi-level elbow. When the curvature of the shaping section <NUM> deviates from a desired requirement, the shaping section <NUM> can be restored to its original shape by a suitable external force, for example by application of heat, then followed by a secondary shaping.

In some embodiments, the shaping section <NUM> of the catheter body <NUM> is disposed at a distance of about <NUM> to about <NUM> from the end of the sharp portion <NUM> to achieve improved side branch access. Because of the flexibility and bendability of the shaping section <NUM>, the microcatheter can access a distal vasculature by manipulating the guide wire. Moreover, the microcatheter <NUM> can pass through the injury site and deliver the guide wire and/or a contrast agent through the site of the injury, for example by deploying an interventional treatment element at the site of the injury and then immediately restore blood flow.

In addition, the shaping section <NUM> enters the side branch of the vasculature. When the microcatheter within the aorta reaches a branch point where the side branch is detached from the aorta, the shaping section <NUM> can be bent at an appropriate angle (e.g., about <NUM>° to about <NUM>°) with respect to the longitudinal axis L of the catheter body <NUM> to point to the entry of the side branch, for example, by removing the guide wire from the microcatheter. When the microcatheter is manipulated by the operator, the shaping section <NUM> having been directed to the entrance of the side branch can be moved into the side branch artery through the entrance. It should be noted that the torque force can be applied to the catheter by rotating the needle base of the catheter body that is rotatable about a central axis.

In the present embodiment, a ratio of the softness of the shaping section <NUM> to the cubic diameter of the shaping section <NUM> is 9gf-17gf/inch<NUM>. The material of the intermediate layer <NUM> of the shaping section is metal, its rigidity is greater than those of the inner layer <NUM> and the outer layer <NUM> of the shaping section. The intermediate section <NUM> of the shaping layer having a relatively high rigidity provides enough rigidity for the shaping section <NUM>, and the inner layer <NUM> and the outer layer <NUM> of the shaping section having a lower rigidity provide a corresponding flexibility for the shaping section <NUM>, thereby enabling the rigidity and the flexibility of the shaping section <NUM> to coexist, and thus the deformation can be memorized while being deformed.

Referring to <FIG>, a schematic cross-sectional view of the shaping section <NUM> of the catheter body is shown. The shaping section <NUM> of the catheter body <NUM> in the present embodiment is a concentric three-layer structure, which comprises: a inner layer <NUM> of the shaping section with a hollow lumen; a tubular intermediate layer <NUM> of the shaping section wrapped outside the inner layer <NUM> of the shaping section, wherein the intermediate layer <NUM> of the shaping section is a spring layer not wrap with the braid; and a tubular outer layer <NUM> of the shaping section wrapped outside the intermediate layer <NUM> of the shaping section, a part of the intermediate layer <NUM> of the shaping section not wrapped with the braid is bent at a certain angle along the longitudinal axis L of the catheter body <NUM>. Thereby, when the microcatheter <NUM> needs to pass through a branch lesion in the coronary artery, the shaping section <NUM> can be previously bent at a corresponding angle in vitro to adapt the angle between the branch and the main branch of the coronary artery, so that the microcatheter <NUM> can pass through the branch lesions smoothly. In the inner layer <NUM> of the shaping section of the catheter body <NUM>, a desired material is interposed, such as a drug, a guide wire may be provided in the hollow lumen of the inner layer <NUM> of the shaping section. The outer diameter of the distal end of the catheter body <NUM> can also vary as measured at the outer surface of the outer layer <NUM> of the shaping section, for example from about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM> and so on.

In the present embodiment, the intermediate layer of the catheter body <NUM> is made of a metal material, and the rigidity of the intermediate layer <NUM> of the pushing section is greater than the rigidity of the intermediate layer <NUM> of the shaping section. The inner layer <NUM> of the pushing section <NUM> is integrated with the inner layer <NUM> of the shaping layer <NUM> to form the inner layer of the catheter body <NUM>, and the outer layer <NUM> of the pushing section <NUM> is integrated with the outer layer <NUM> of the shaping section <NUM> to form the catheter layer of the catheter body <NUM>.

With continued reference to <FIG>, in the present embodiment, the wall of the intermediate layer <NUM> of the shaping section has a plurality of voids. The outer layer <NUM> is embedded in the void of the intermediate layer <NUM> of the shaping section and is heat-fused with the inner layer <NUM> so that the shaping section <NUM> becomes an integrated structure from inside to outside, and the integrated structure is softer and has a certain degree of toughness in the void of the intermediate layer <NUM>, which is conductive to bending for shaping and is not easily broken, and has a certain rigidity in the intermediate layer <NUM> without the voids, which is conductive to maintaining the shape after being shaped. Besides, since the outer layer <NUM> is embedded in the void of the intermediate layer <NUM> and is heat-fused with the inner layer <NUM>, so that the catheter body <NUM> forms a self-locking structure similar to the lead angle of the thread at the void of the intermediate layer <NUM> so that a memory microcatheter <NUM> with a better preformed effect is obtained.

In the present embodiment, the intermediate layer <NUM> of the shaping section <NUM> is a spring tube, the void is formed between the adjacent threads of the spring tube, wherein the outer layer <NUM> of the shaping section is embedded in the void of the adj acent threads and is bonded with inner layer <NUM> of the shaping section so as to obtain a better preformed ability.

The outer layer <NUM> may be made of a material with good flowability, the inner layer <NUM> may be made of a material with poor flowability, wherein the outer layer <NUM> herein is made of a thermoplastic polymer, and the thermoplastic polymer of the outer layer <NUM> of the shaping section is embedded in the intermediate layer <NUM> of the shaping section to wrap around the intermediate layer <NUM> of the shaping section. When the outer layer and the inner layer are hot-melt-bonded, the outer layer <NUM> of the shaping section can penetrate and diffuse into the inner layer <NUM> of the shaping section through the void of the intermediate layer <NUM> of the shaping section to achieve melting.

Referring to <FIG>, a schematic cross-sectional view of the position of the pushing section <NUM> that the spring layer <NUM> is wrapped with the braid <NUM> in the microcatheter is shown. The pushing section <NUM> of the present embodiment includes, from the inner to the outer, a inner layer <NUM> of the pushing section having a hollow lumen, a tubular intermediate layer <NUM> of the pushing section wrapped outside the inner layer <NUM> of the pushing section, and a tubular outer layer <NUM> of the pushing section wrapped outside the intermediate layer <NUM> of the pushing section. Wherein, the intermediate layer <NUM> of the pushing section is made of a metal material, and the rigidity of the intermediate layer <NUM> of the pushing section is greater than the rigidity of the intermediate layer <NUM> of the shaping section.

The <FIG> is shown as a longitudinal side view of the catheter body <NUM>, the intermediate layer <NUM> of the shaping section is a double-layered tube comprising a spring layer <NUM> and a braid <NUM> wrapping around a longitudinal part of the spring layer <NUM> from the proximal end. The intermediate layer of the catheter body <NUM> is formed integrally by the intermediate layer <NUM> of the shaping section extending to the pushing section <NUM>, and the braid <NUM> is wrapped outside the spring layer <NUM>. In some embodiment, the braid <NUM> wrapped around about <NUM>%-<NUM>%, about <NUM>%-<NUM>%, about <NUM>%-<NUM>%, about <NUM>%-<NUM>%, or about <NUM>%-<NUM>% of the entire longitudinal length of the spring layer <NUM>. A bending point is located at the distal end of the position where the braid <NUM> wrapping range ends. However, the bending point may occur at any point along the shaping section <NUM>. In a particular embodiment, the braid <NUM> may wrap around <NUM>% of the entire spring layer <NUM>, for example, the length of the spring layer <NUM> is <NUM>, then the length of the braid <NUM> is <NUM>, thereby, <NUM> of spring layer <NUM> is not wrapped with the braid <NUM>.

The outer surface of the spring layer <NUM> of the shaping section is not completely wrapped with the braid <NUM> (partial) as shown in <FIG>, the part of the microcatheter with a extending braid <NUM> has an extra rigidity and elasticity compared to the portion without the braid <NUM> so that the portion containing the braid <NUM> constitutes the pushing section <NUM> of the catheter body <NUM>; the portion not containing the braid <NUM> constitutes the shaping section <NUM> of the catheter body <NUM>. When the microcatheter enters the blood vessel, a stiffer pushing section can be used to provide forward thrust to advance the microcatheter through an obstacle such as a severe lesion.

In the present embodiment, the outer diameter of the entire spring layer of the catheter body <NUM> which consists of the spring layer <NUM> of the pushing section and the spring layer <NUM> of the shaping section decreases from the proximal end to the distal end. The spring layer may comprise a winding flat filaments made of stainless steel or Nitinol. It can also be made of other metal materials. For example, other metals include superelastic nickel titanium, shape memory nickel titanium, Ti-Ni, nickel titanium, approximately <NUM>-<NUM> wt% of Ni, Ni-Ti-Hf, Ni-Ti-Pd, Ni-Mn-Ga, <NUM> to <NUM> series of SAE grade stainless steel (SST), such as <NUM>, <NUM>, <NUM>, <NUM>, MP35N and <NUM>-<NUM> precipitation hardening (PH) stainless steel, other spring steels, other high tensile strength materials or other biocompatible metal materials. In a preferred embodiment, the material is superelastic or shape memory nickel titanium; in another preferred embodiment, the material is stainless steel.

The spring layer may include a superelastic alloy normally called "shape memory alloy". Components made of this shape memory alloy have the ability to recover their original shapes after deformation, so that they will undergo permanent deformation if they are made of ordinary metals. The superelastic alloys used in the present invention include: Elgiloy® and Phynox® spring alloys (Elgiloy® alloys are available from Carpenter Technology Corporation, Reading Pa; Phynox® alloys are available from Metal Imphy, Imphy, France), SAE grade <NUM> stainless steels, MP35N(nickel-cobalt) alloys obtained from Carpenter Technology, Latrobe Steel, Latrobe, Pa. , and superelastic Nitinol, available from Shape Memory Applications, Santa Clara, California.

As described above, suitable superelastic alloys include nickel titanium (Nitinol) consisting essentially of <NUM>-<NUM> atomic precent Ni, Cu-Zn alloy consisting essentially of <NUM>-<NUM> wt% Zn, Cu-Zn-X alloy containing <NUM>-<NUM> wt% X (X=Be, Si, Sn, Al or Ga), and Ni-Al alloy consisting essentially of <NUM>-<NUM> atomic percent Al. The particularly preferred superelastic alloy is Nitinol. The mechanical property of the nickel-titanium alloy can be changed as needed, replacing a part of the Ti-Ni alloy with another element X (X=Cu, Pd or Zr) of <NUM> to <NUM> atomic percent, or selecting the condition for cold processing and/or final heat treatment. The bending strength (stress generated when the load is increased) of the superelastic alloy used is <NUM>-<NUM>/mm<NUM> (<NUM>), preferably <NUM>-<NUM>/mm<NUM>, and the recovery stress (stress generated when the load is reduced) is <NUM>-<NUM>/mm<NUM>(<NUM>), preferably <NUM>-<NUM>/mm<NUM>. Alternatively, the spring layer may be formed from a polymer. Examples of polymers include polymide, PEEK, nylon, polyurethane, polyethylene terephthalate (PET), latex, HDHMWPE (high density, high molecular weight polyethylene) and thermoplastic elastomers.

For example, the spring layer can be prepared by forming a superelastic metal tube, and then by removing the portion of the tube that will form recesses or holes. The recesses, holes or cuts may be formed in the pipe by the way that may be selected from the group of consisting of laser (e.g., YAG laser), electrical discharge, chemical etching, mechanical cutting or a combination thereof.

After being deformed and deformed into a predetermined shape (for example, a curved shape) by heating, the spring layer may be cooled. The spring layer is then constrained in a deformed state within a delivery system to facilitate insertion into blood vessels such as arteries. Once the physical constraints on the tubular module have been removed, the superelastic tubular module can returned to its original underformed shape, i.e. curve.

In one embodiment, the spring layer may be formed of a plurality of spiral portions. The spring layer may have several different types of spiral cutting patterns, comprising continuous and discontinuous spiral cutting patterns. The different spiral cutting patterns may be distributed on the same or different tubular modules. The spiral cutting section can provide a gradual trasition of bending flexibility by pushability, kink resistance, axial torque transmission for rotational response and/or torque on fault measurement. For example, the spiral cutting patterns may have a varying pitch to increase flexibility in one or more regions of the spring layer. The spiral cutting pitch can be measured by the distance between points in the same radial position in two adjacent threads. In one embodiment, the pitch may increase when the spiral cutting progresses from the proximal position to the distal position of the catheter. By adjusting the pitch and the incision and the uncut path of the spiral incision, the pushability, kink resistance, torque, flexibility, and compression resistance of the catheter (i.e. the tubular module) can be adjusted.

In addition, when the tubular module is bent or tortuous, the spiral cutting pattern allows to maintain the cross-sectional diameter of the lumen. The spiral cutting sections with different cutting patterns may be distributed along the length of the tubular module. The spiral pattern may be continuous or discontinuous along the length of the module. For example, there may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,. n spiral cutting sections along the length of the module. The spiral cutting sections may be continuous or discontinuous. There may be a constant cutting pattern within each section, but the cutting pattern can be changed for example according to the pitch in the different sections of the tubular module. Each section can also contain a variable pitch pattern within a specific section. Each spiral cutting section may have a constant pitch, for example in the range of about <NUM> to about <NUM>, for example <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and so on. The pitch can also vary within each section. The pitch of the different spiral cutting sections may be the same or different. Alternatively, the catheter may be formed of a tubular module having a continuously varying spiral cutting pattern along the length of the catheter. The orientation in the module or the helicity of the spiral cutting section may also vary within the spiral incision. The width of the spiral incision can vary, for example from about <NUM> micro to about <NUM> microns. In another embodiment, the spring layer may be a continuous coil.

The braid <NUM> of the intermediate layer <NUM> of the pushing section is formed by alternatively interlacing a plurality of strands of filaments. At least one strand of the filaments protrudes outwardly from other threads so that the outer surface of the braid <NUM> has convex ribs with streamline. The braiding density of the braid <NUM> in the present embodiment gradually changed from <NUM> PPI to <NUM> PPI from the proximal end to the distal end.

Preferably, as shown in <FIG>, in the present embodiment, the braid <NUM> is formed by alternatively interlacing thick threads <NUM> and thin threads <NUM>. The surface of the thick thread <NUM> protrudes outwardly from the surface of the thin thread <NUM>, and the protruding thick thread <NUM> extends spirally along the axial direction of the braid. In the microcatheter <NUM> provided in such a configuration, the thick thread <NUM> can form a spiral protrusion on the surface of the outer layer after the outer layer of the catheter body <NUM> is wrapped around the braid <NUM>, so that the contact area between the microcatheter <NUM> and the inner wall of the blood vessel is reduced, thus the resistance of the microcatheter <NUM> is reduced during the pushing process.

Specifically, the braid <NUM> in the present embodiment can be braided in a <NUM>:<NUM> or <NUM>:<NUM> weaving manner using <NUM>-strand, <NUM>-strand or <NUM>-strand threads. When the <NUM>-strand threads are used for weaving, <NUM>-strand thick threads <NUM> can be matched with <NUM>-strand thin threads, followed by alternately weaving with <NUM>-strand threads. Therein, the outer diameter of the thick thread <NUM> is larger than the outer diameter of the thin thread <NUM>.

Referring to <FIG>, in another embodiment, the spring layer <NUM> is a tapered spring having a diameter that tapers from the proximal end to the distal end of the catheter body <NUM>, and the spring layer <NUM> may be formed by a continuous winding spring coil. The spring layer <NUM> comprises a distal section <NUM>, a proximal section <NUM>, and gradational section <NUM> between the distal section <NUM> and the proximal section <NUM>. In the present embodiment, the pitch of windings in the distal section and the pitch of the proximal section are constant, and the coil pitch of the distal section <NUM> is greater than the coil pitch of the proximal section <NUM>. In the illustrated embodiment, the coil pitch of the gradational section <NUM> is not constant but increases along its longitudinal length. By varying the pitch of the coils, the spring layer <NUM> of the catheter body <NUM> can increase flexibility gradually toward the distal end while maintaining proper torsional forces and malleability to enable manipulation of the microcatheter.

In the present embodiment, the pitch of the distal section <NUM> and the pitch of the proximal section <NUM> are both constant, and the pitch of the distal section <NUM> is greater than the pitch of the proximal section <NUM>. Specifically, the pitch of the distal section <NUM> is <NUM> PPI, and the pitch of the proximal section <NUM> is <NUM> PPI; the pitch of the gradational section <NUM> shows an increase trend from the proximal end to the distal end, and the pitch of the gradational section <NUM> changes gradually from <NUM> PPI to <NUM> PPI from the proximal end to the distal end, thereby obtaining a better bending and shape-locking effect in the shaping section, while improving the supporting force and the recoil force of the proximal end.

In addition, the intermediate layer of the catheter body <NUM> in the present embodiment is a tapered spring with a diameter gradually reduced from the proximal end to the distal end to further ensure the flexibility of the distal end of the microcatheter <NUM>.

Referring to <FIG>, in the present embodiment, the outer layer <NUM> of the catheter body <NUM> is an integrated spiral corrugated tube, which comprises: a spirally convex wave crest <NUM> and a concave wave trough <NUM> relative to the wave crest on the outer surface of the spiral corrugated tube. In the present embodiment, the intermediate layer <NUM> of the shaping section <NUM> is a spring layer. Further, the wave trough <NUM> on the outer layer of the catheter body <NUM> is embedded in a gap between threads of the spring tube, the wave crest of the outer layer and the threads of the spring tube are in contact and bonded together. The microcatheter <NUM> arranged in such a configuration may form a spirally convex wavy surface on the outer surface of the catheter body <NUM>. Since the protruding wave crest <NUM> tends to contact with an inner wall of the blood vessel, and the wave trough <NUM> tends not to contact with the inner wall of the blood vessel, the contact area between the outer surface of the microcatheter and the inner wall of the vessel through which the microcatheter penetrates is reduced, thereby, the friction to the blood vessel during the progress of the microcatheter advancement is reduced.

Preferably, the wall thickness of the spiral corrugated tube decreases along the direction from the proximal end to the distal end, and a distance between two adjacent wave crests <NUM> increases along the direction from the proximal end to the distal end. In the present embodiment, the pitch of the spiral corrugated tube gradually changes from <NUM> PPI to <NUM> PPI from the proximal end to the distal end.

Besides, in the present embodiment, the outer diameter of the outer layer of the catheter body <NUM> tends to decrease along the direction from the proximal end to the distal end, and the rigidity of the outer layer of the catheter body <NUM> tends to decrease along the direction from the proximal end to the distal end, and the wall thickness of the outer layer of the catheter body <NUM> tends to decrease along the direction from the proximal end to the distal end.

Specifically, the outer layer of the catheter body <NUM> of the present embodiment is wrapped outside the outer surface of the intermediate layer, this outer layer may be made of only one of thermoplastic materials such as polyester, polyamide, polyimide, polyethylene, polypropylene and the like, or is formed by polymerization of the above two or more materials to obtain better lubricity and fluidity after heating of the outer layer, and improve the hot melting adhesion effect of the inner and outer layer of the catheter body <NUM>. Preferably, the rigidity of the outer layer decrease from the proximal end to the distal end. Preferably, on a Type A Shore Hardness Scale, the rigidity of the outer layer can be within the range from about 30A to about 80A, about 40A to about 70A or about 45A to about 65A. In addition, the outer diameter of the outer layer <NUM> can be reduced from the proximal end to distal end, which further ensures the rigidity of the catheter body <NUM> decreasing toward the distal end.

Referring to <FIG>, a schematic diagram of a preferred structure of the intermediate layer of the catheter body <NUM> is shown, a hollowed-out skeleton tube, rather than the spring tube, is used as the intermediate layer <NUM> of the shaping section, wherein the hollow in the skeleton tube forms the gap of the intermediate layer, and the outer layer of the catheter body <NUM> is embedded in the intermediate layer <NUM> of the shaping section through the hollow in the skeleton tube and is thermally fused with the inner layer <NUM> of the shaping section, so that the hollow part forms a soft and flexible structure, which is conducive to bending and is not easily broken, and the non-hollowed part has a certain rigidity, which facilitates shape retention after shaping, so that the whole microcatheter <NUM> is formed into a rigid and flexible intertwined structure, and thus a microcatheter <NUM> with a better preshaping effect and a better locking function is obtained.

Referring to <FIG>, which is another alternative embodiment of the intermediate layer of the pushing section of the catheter body <NUM>, the intermediate layer <NUM> of the pushing section comprises a spring layer <NUM> and a braid <NUM>. This braid <NUM> is a spring-like structure wound by monofilaments, and is wound around a majority of the spring layer <NUM> with a relatively small pitch. The spring layer <NUM> is a spring tube. The spring layer <NUM> of the shaping section is not wrapped by the braid <NUM> at the distal side of the spring layer <NUM>, namely, the intermediate layer <NUM> of the pushing section is a spring-like double-layer spring structure formed by wrapping a monofilament braid around the spring tube to make sure that the ratio between the rigidity of the pushing section <NUM> to the rigidity of the shaping section <NUM> is moderate, further, the torsional force and flexion resistance in the proximal end of the microcatheter <NUM> is balanced, and the traversing, traceability and flexibility and supporting force in the distal end are balanced, to ensure the microcatheter <NUM> will reach the lesion site smoothly.

Referring to <FIG>, the intermediate layer <NUM> of the pushing section of the catheter body <NUM> comprises a spring layer <NUM> and a braid <NUM> partially wrapped on the spring layer <NUM>, wherein this spring layer <NUM> is a spring tube, and the braid <NUM> is a skeleton layer, the skeleton layer of the present embodiment is a hollow body structure. The skeleton layer is wrapped outside the spring tube, and the skeleton layer and the spring tube wrapped with the skeleton layer constitute the intermediate layer <NUM> of the pushing section, namely, the intermediate layer <NUM> of the pushing section is a structure in the form of the spring tube being sleeved on the skeleton tube, further, the torsional force and flexion resistance in the proximal end of the microcatheter <NUM> is balanced, and the traversing, traceability and flexibility and supporting force in the distal end are balanced, to ensure the microcatheter <NUM> will reach the lesion site smoothly.

In <FIG>, another alternative embodiment is shown. In the present embodiment, the shaping section <NUM> of the microcatheter <NUM> comprises a spiral corrugated tube formed by a strengthening rib <NUM> that is protruded periodically. The spiral corrugated tube comprises a tubular inner wall <NUM> and corrugations <NUM> spirally projected on an outer periphery of the inner wall, wherein the metal strengthening rib <NUM> is provided on the spiral corrugated tube. The strengthening rib <NUM> of this embodiment is provided between the corrugations <NUM> and the inner wall <NUM>, fitting inside the corrugations <NUM> along the corrugations <NUM>. In some other preferred embodiments, the strengthening rib <NUM> may also be embedded in the corrugations <NUM>, specifically, the corrugation <NUM> has a two-layer structure, and the strengthening ribs <NUM> are embedded between two corrugations <NUM>.

A position between the adjacent corrugations <NUM> of the spiral corrugated pipe is relatively soft and has a certain toughness, which is conducive to bending and is not easy to be broken, while the position of the corrugations <NUM> has a certain rigidity, which is conducive to shape retention and shape locking after shaping. Accordingly, the deformation of the spiral corrugated tube after being deformed can be memorized, so as to ensure that the microcatheter <NUM> can adapt to different angles between the branch and the main branch of the coronary artery, and thus to make sure that the microcatheter <NUM> can smoothly pass through the branch lesions.

Preferably, the inner wall <NUM> of the spiral corrugated tube in this embodiment may be made of a material with a small friction coefficient, so that medicine, the guide wire or other interventional systems entering the spiral corrugated tube will obtain a smaller friction force to reach the lesion site in the blood vessels smoothly.

Preferably, the outer diameter of the catheter body <NUM> in this embodiment decreases gradually along the direction from the proximal end to the distal end, so as to further ensure the softness of the catheter body <NUM> increases gradually from the proximal end to the distal end.

In this embodiment, the inner layer of the catheter body <NUM> is made of a material with a low coefficient of friction, such as a polymer material of nylon, polyether block amide, PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene), PFA(Perfluoroalkoxyalkane), PET(polyethylene terephthalate) or PEEK(polyetheretherketone). The inner layer may be formed by a dip coating process or by spraying a coating onto the inner surface of the intermediate layer. The low coefficient of friction of the inner layer helps to intervene the desired material through the microcatheter, so that the medicine, guide wire or other interventional systems entering the inner layer will obtain a smaller friction force to reach the lesion site in the blood vessels smoothly.

The outer surface of the outer layer of the catheter body <NUM> in the present embodiment is coated with a highly lubricious hydrophilic polymer. The outer layer may be made of a material with good fluidity, and the inner layer may be made of a material with poor fluidity. When the outer layer and the inner layer are hot-melt-bonded, the outer layer can penetrate and diffuse into the inner layer to achieve melting.

It should be noted that in other embodiments, the spring layer of the catheter body <NUM> may be a straight tube of an equal diameter, or may be a reducing tube with a diameter gradually decreasing from the proximal end to the distal end. Correspondingly, when the spring layer of the catheter body <NUM> is the equal-diameter straight tube, the outer layer of the catheter body <NUM> can either be a straight tube with a smooth outer wall of equal diameter, or an equal-diameter corrugated tube; when the spring layer of the catheter body <NUM> is the reducing tube that is tapered from the proximal end to the distal end, the outer layer of the catheter body <NUM> can be a conical tube or a conical corrugated tube of a corresponding diameter.

<FIG> is a perspective view of the distal end of the microcatheter (shown with the outer layer being transparent), showing the shaping section <NUM> in a slightly curved configuration with respect to the axis of the microcatheter.

<FIG> show a sequence in which the shaping section <NUM> of the microcatheter is bent from a line structure (<NUM>°with respect to the longitudinal axis L) to a bending position of about <NUM>° with respect to the longitudinal axis L of the catheter body. Specifically, in <FIG>, the catheter body comprising the pushing section <NUM>, the shaping section <NUM> and the sharp portion <NUM> is longitudinally aligned. In <FIG>, the shaping section <NUM> is being bent downward. In some embodiments, the shaping section <NUM> is bent downward along with the withdrawal of the guide wire, which allows the shaping section <NUM> to present its natural curved shape due to shape memory. As the shaping section <NUM> bends, the sharp portion <NUM> bends downward with the shaping section <NUM>.

In <FIG>, the shaping section <NUM> reaches its stability limit based on its shape memory so that the distal end of the shaping section and the sharp portion are directed at an angle of α with respect to the axis L. In the described embodiment, the angle α is about <NUM>°, but in various embodiments, the bending angle can be preset differently based on shape memory to manipulate the microcatheter to pass through the tortuous side branch of the vascular system. The shaping section <NUM> may be bent at any point of the shaping section. The angle α may range from about <NUM>°to about <NUM>°, about <NUM>°to about <NUM>°, about <NUM>°to about <NUM>°, about <NUM>°to about <NUM>°, about <NUM>°to about <NUM>°, about <NUM>°to about <NUM>°, about <NUM>°to about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>°, about <NUM>° or about <NUM>°. Depending on the anatomy requirement of the branch entrance of a specific size, the shaping section <NUM> can also be directly bent into a J-shaped elbow, S-shaped or semi-circular shape. The bending point can be set by adjusting the thickness of the coil or by using the characteristics of the shape memory metal at the bending point.

<FIG> shows the side branch access of the microcatheter. In <FIG>, the microcatheter is moving through the aorta <NUM> in a right direction. The side branch <NUM> occurs at a junction from the apex of the aorta and extends upward and rightward from the aorta. As shown in <FIG>, the shaping section of the microcatheter <NUM> is bent in the way shown in <FIG>. In this configuration, the sharp portion <NUM> of the microcatheter is aligned with the side branch <NUM>. With proper manipulation of the microcatheter by the operator, the catheter body <NUM> of the microcatheter can be moved upwards and the sharp portion <NUM> can be guided into the side branch <NUM> along the path of the arrow.

In addition, as other embodiments of the present invention, the intermediate layer <NUM> of the pushing section of the catheter body <NUM> may also be a single-layer structure or a structure of more than three layers, but regardless of how many layers the intermediate layer <NUM> of the pushing section may have, it must satisfy the requirement that the rigidity of the intermediate layer <NUM> of the pushing section is greater than the rigidity of the intermediate layer <NUM> of the shaping section. When the intermediate layer <NUM> of the pushing section is the single-layer structure, the intermediate layer <NUM> of the pushing section and the intermediate layer <NUM> of the shaping section can be manufactured separately using different materials and then welded together. Alternatively, the intermediate layer <NUM> of the pushing section and the intermediate layer <NUM> of the shaping section are made of same material, but the material thickness or the material density of the intermediate layer <NUM> of the pushing section is higher, or adopting different structures to make the rigidity of the intermediate layer <NUM> of the pushing section greater than the rigidity of the intermediate layer <NUM> of the shaping section.

In summary, according to the microcatheter of the present invention, the certain length range near to the sharp portion is the shaping section with prefabricating ability. This shaping section can be bent at a corresponding angle in advance in vitro to fit the angle between the branch and the main branch of the coronary artery, which allows the microcatheter to pass through the lesions in the branch smoothly; meanwhile, the pushing section can provide a certain support force and recoil force proximal to the shaping section to improve the torque control force of the microcatheter, so that the catheter body has sufficient twisting force and supporting force, thereby improving the traversing, traceability and flexibility of the microcatheter effectively.

Claim 1:
A microcatheter (<NUM>), with tubular structure, comprising a catheter body (<NUM>), a sharp portion (<NUM>) disposed at a distal end of the catheter body (<NUM>); the catheter body (<NUM>) has a proximal end and a distal end, the catheter body (<NUM>) comprises:
an inner layer (<NUM>, <NUM>), with a hollow lumen;
a tubular intermediate layer (<NUM>, <NUM>) wrapped outside the inner layer (<NUM>, <NUM>), comprising a spring layer (<NUM>, <NUM>) and a braid (<NUM>) above the spring layer (<NUM>, <NUM>), the braid (<NUM>) extending longitudinally along a part of the spring layer (<NUM>, <NUM>); and
a tubular outer layer (<NUM>, <NUM>), wrapped outside the intermediate layer (<NUM>, <NUM>);
the part of the spring layer (<NUM>, <NUM>) which is not wrapped by the braid (<NUM>) is bent at a certain angle along a longitudinal axis of the catheter body (<NUM>);
characterized in that
the outer layer (<NUM>, <NUM>) is a spiral corrugated tube, which comprises: a spirally convex wave crest (<NUM>) and a concave wave trough (<NUM>) relative to the wave crest (<NUM>) on the outer surface of the spiral corrugated tube, and wherein the part of the spring layer (<NUM>, <NUM>) which is not wrapped by the braid (<NUM>) is a spring tube, and the wave trough (<NUM>) of the outer layer (<NUM>, <NUM>) is embedded in a gap between threads of the spring tube, the wave crest (<NUM>) of the outer layer (<NUM>, <NUM>) and the threads of the spring tube are in contact and bonded together.