Balloon Microcatheter

Abstract

The present invention provides a balloon microcatheter, comprising an inner tube, an outer tube and a balloon. The inner cavity of the inner tube forms a delivery channel, and the inner tube has a first section and a second section arranged in sequence from the proximal end to the distal end; the outer tube is sleeved on the outer periphery of the first section, and a fluid channel is formed between the outer tube and the first section; the balloon is arranged on the side of the second section and arranged side by side with the second section, and its distal end, proximal end and middle part are all fixedly connected to the outer surface of the second section; the inner cavity of the balloon is connected to the fluid channel, and when the inner cavity of the balloon is filled with fluid to be in an expanded state, the middle part of the second section bulges and bends toward the balloon. Even if the embolization coil kicks the head end of the balloon microcatheter from the middle of the aneurysm cavity to the aneurysm wall, the balloon in the expanded state is close to the aneurysm wall to avoid the head end of the balloon microcatheter from contacting the aneurysm wall, and the tension provided by the balloon can also prevent the second section from bending and deforming under the tension of the embolization coil, thereby reducing the impact on the aneurysm wall and not affecting the delivery of the embolization coil.

Description

Technical Field

[0001] The invention relates to a vascular interventional medical device, in particular to a balloon microcatheter. Background Art

[0002] Intracranial aneurysms are abnormal bulges formed by the gradual expansion of intracranial arteries under the influence of hemodynamic load or other factors. They are caused by congenital abnormalities or acquired injuries, and often appear at the bifurcation or branching of the main blood vessels. Once an intracranial aneurysm ruptures and bleeds, the mortality and disability rates are extremely high. It is a cerebrovascular disease with high morbidity and mortality, and is the main cause of subarachnoid hemorrhage. The mortality rate of ruptured intracranial aneurysms is as high as 51%, and the disability rate of survivors is close to 50%.

[0003] Currently, there are two ways to treat intracranial aneurysms clinically: one is surgical craniotomy to clip or ligate the aneurysm. Its disadvantages are long operation time and great trauma to the patient. It is also very difficult to use surgical treatment for aneurysms in special parts such as the internal carotid artery and the main trunk of the vertebral basilar artery. The other is interventional endovascular treatment, which has the advantages of being minimally invasive, safe and effective. It has become the preferred clinical treatment option for many medical experts. The most commonly used method is percutaneous vascular puncture under the guidance of X-rays, and the embolic coil is embolized into the aneurysm cavity through a delivery catheter to form a solid aneurysm and seal it.

[0004] However, during the process of embolizing aneurysms, on the one hand, the embolizing coil can easily kick the tip of the delivered microcatheter from the middle of the aneurysm cavity to the aneurysm wall, causing the tip of the microcatheter to press against the aneurysm wall and the embolizing coil to release against the wall, thereby increasing the risk of aneurysm rupture; on the other hand, the microcatheter can easily bend and deform under the tension of the embolizing coil, and the bend can press against the aneurysm wall, which not only increases the risk of aneurysm rupture but also affects the delivery of the embolizing coil. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a balloon microcatheter to solve the problem that the microcatheter is easily bent and deformed under the tension of the embolic spring coil, and is kicked to the aneurysm wall, thereby causing the aneurysm wall to rupture easily and the embolic spring coil to be poorly delivered.

[0006] In order to achieve one of the above-mentioned purposes of the invention, an embodiment of the present invention provides a balloon microcatheter, comprising:

[0007] An inner tube, whose inner cavity forms a delivery channel, and the inner tube has a first section and a second section arranged in sequence from the proximal end to the distal end;

[0008] an outer tube, sleeved on the outer circumference of the first section, and forming a fluid channel between the outer tube and the first section;

[0009] The balloon microcatheter also includes a balloon arranged on the side of the second section, the balloon is arranged side by side with the second section, and its distal end, proximal end and middle part are fixedly connected to the outer surface of the second section; the inner cavity of the balloon is connected to the fluid channel, and when the inner cavity of the balloon is filled with fluid to be in an expanded state, the middle part of the second section bulges and bends toward the balloon.

[0010] As a further improvement of an embodiment of the present invention, the stiffness of the inner tube gradually decreases from the proximal end to the distal end.

[0011] As a further improvement of one embodiment of the present invention, the inner tube includes an inner layer, an outer layer, and an intermediate layer arranged between the inner layer and the outer layer, and the intermediate layer includes at least one of a braided segment and a spiral coil segment, wherein the spiral coil segment extends spirally around the outer circumference of the inner layer.

[0012] As a further improvement of an embodiment of the present invention, the intermediate layer includes a spiral coil segment extending from the proximal end to the distal end of the inner tube, and the spiral coil segment is formed by spirally winding a wire around the outer periphery of the inner layer.

[0013] As a further improvement of one embodiment of the present invention, the wire is a flat wire, and the width of the flat wire gradually decreases from the proximal end to the distal end of the spiral coil segment; or, the wire is a round wire, and the diameter of the round wire gradually decreases from the proximal end to the distal end of the spiral coil segment.

[0014] As a further improvement of an embodiment of the present invention, the pitch of the helical coil segment gradually decreases from the proximal end to the distal end of the helical coil segment.

[0015] As a further improvement of an embodiment of the present invention, the middle layer includes a braided segment and a spiral coil segment arranged in sequence from the proximal end to the distal end.

[0016] As a further improvement of an embodiment of the present invention, the braiding density of the braided segment gradually increases from the proximal end to the distal end.

[0017] As a further improvement of one embodiment of the present invention, the outer layer includes a substrate and a toughening agent doped in the substrate, and the content of the toughening agent gradually decreases from the proximal end to the distal end of the outer layer.

[0018] As a further improvement of an embodiment of the present invention, the thickness of the distal end of the outer layer is smaller than the thickness of the proximal end thereof, and / or the stiffness of the distal end of the outer layer is smaller than the stiffness of the proximal end thereof.

[0019] As a further improvement of an embodiment of the present invention, the balloon is a compliant balloon.

[0020] Compared with the prior art, the present invention has the following beneficial effects: during the process of embolizing an aneurysm, after the tip of the balloon microcatheter reaches the aneurysm cavity, liquid is transported to the inner cavity of the balloon through the fluid channel, so that the balloon is in an expanded state, and the middle part of the second section is convexly bent toward the balloon, so that the tip of the balloon microcatheter can be prevented from directly contacting the aneurysm wall. Even if the embolization spring coil kicks the tip of the balloon microcatheter from the middle of the aneurysm cavity to the aneurysm wall, the side of the balloon away from the second section will contact the aneurysm wall, and the expanded state The inflated balloon is pressed against the aneurysm wall to prevent the tip of the balloon microcatheter from directly contacting the aneurysm wall, and also increases the contact area between the balloon and the aneurysm wall, reducing the impact of the balloon microcatheter on the aneurysm wall. The tension provided by the balloon can also effectively prevent the second section from bending and deforming under the tension of the embolization coil, thereby preventing the tip or second section of the balloon microcatheter from bending and pressing against the aneurysm wall to rupture the aneurysm wall, and will not affect the delivery of the embolization coil, ensuring that the embolization coil is smoothly released from the balloon microcatheter and filled into the aneurysm wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings provided herein are used to further illustrate the understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0022] Figure 1 is an exploded schematic diagram of a balloon microcatheter according to an embodiment of the present invention, wherein a cross section of the second section is shown;

[0023] Figure 2 It is a schematic diagram of an explosion of a balloon microcatheter according to one embodiment of the present invention when the balloon is in an expanded state, wherein a cross section of the second section is shown;

[0024] Figure 3 is a cross-sectional view of a balloon microcatheter according to one embodiment of the present invention;

[0025] Figure 4 It is a schematic diagram of the structure of a balloon microcatheter delivering an embolic coil into an aneurysm cavity in one embodiment of the present invention;

[0026] Figure 5 is a schematic cross-sectional view of an inner tube according to an embodiment of the present invention;

[0027] Figure 6 A schematic diagram of the structure of a spiral coil segment of an intermediate layer according to an embodiment of the present invention;

[0028] Figure 7 It is a schematic structural diagram of a braided segment of an intermediate layer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of this application clearer, the technical solution of this application will be clearly and completely described in combination with the specific embodiments of this application and the corresponding drawings. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] In various drawings of the present invention, for the sake of convenience of illustration, some sizes of structures or parts are exaggerated relative to other structures or parts, and thus, only the basic structure of the subject matter of the present invention is illustrated.

[0031] It should be understood that, unless otherwise expressly specified and limited, in the description of the present invention, the terms "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0032] See also Figures 1 to 3 The present invention provides a balloon microcatheter 100, comprising:

[0033] The inner tube 11 has an inner cavity forming a delivery channel 15 for the embolic coil 300 to pass through and be delivered to the aneurysm cavity 21. The inner tube 11 has a first section 111 and a second section 112 connected to each other. Specifically, the first section 111 and the second section 112 are sequentially arranged from the proximal end to the distal end.

[0034] The outer tube 12 is sleeved on the outer circumference of the first section 111, and a fluid channel 16 is formed between the outer tube 12 and the first section 111;

[0035] The handle 13 is connected to the proximal ends of the inner tube 11 and the outer tube 12. The handle 13 includes a main tube 131 whose inner cavity is connected to the delivery channel 15, and a secondary tube 132 whose inner cavity is connected to the fluid channel 16. The embolic spring coil 300 is delivered from the inner cavity of the main tube 131 to the aneurysm cavity 21 through the delivery channel 15.

[0036] The handle 13 is connected to the inner tube 11 and the outer tube 12 by welding or gluing.

[0037] In the present invention, the terms "distal" and "proximal" should be understood as viewed from the direction of the instrument operator, the proximal end is the end facing the instrument operator, and the distal end is the end away from the instrument operator. The direction indicated by the arrow in the figure is from the proximal end to the distal end.

[0038] See also Figures 1 to 3The balloon microcatheter 100 further includes a balloon 14 disposed on the side of the second section 112. The balloon 14 and the second section 112 are disposed side by side, and the distal end, the proximal end and the middle portion thereof are fixedly connected to the outer surface of the second section 112. The inner cavity of the balloon 14 is connected to the fluid channel 16, so that the fluid can flow from the inner cavity of the auxiliary tube 132 through the fluid channel 16 to the inner cavity of the balloon 14, or the fluid can be sucked out of the balloon microcatheter 100 from the inner cavity of the balloon 14 through the fluid channel 16 and the inner cavity of the auxiliary tube 132; see Figure 4 When the inner cavity of the balloon 14 is filled with fluid to be in an expanded state, the middle portion of the second section 112 bulges and bends toward the balloon 14 .

[0039] In this way, during the process of embolizing the aneurysm 200, after the tip of the balloon microcatheter 100 reaches the aneurysm cavity 21, the liquid is transported to the inner cavity of the balloon 14 through the fluid channel 16, so that the balloon 14 is in an expanded state, and the middle part of the second section 112 is convex and curved toward the balloon 14, which can avoid the tip of the balloon microcatheter 100 from directly contacting the aneurysm wall 22. Even if the embolization spring coil 300 kicks the tip of the balloon microcatheter 100 from the middle of the aneurysm cavity 21 to the aneurysm wall 22, the side of the balloon 14 away from the second section 112 will contact the aneurysm wall 22, and the inflated balloon 14 is close to the aneurysm wall 22. The head end of the balloon microcatheter 100 is prevented from directly contacting the aneurysm wall 22, and the contact area between the balloon 14 and the aneurysm wall 22 is increased, reducing the impact of the balloon microcatheter 100 on the aneurysm wall 22. The tension provided by the balloon 14 can also effectively prevent the second section 112 from bending and deforming under the tension of the embolic spring coil 300, thereby preventing the head end of the balloon microcatheter 100 or the second section 112 from bending and pressing against the aneurysm wall 22 to rupture the aneurysm wall 22, and will not affect the delivery of the embolic spring coil 300, thereby ensuring that the embolic spring coil 300 is smoothly released from the balloon microcatheter 100 and filled into the aneurysm wall 22.

[0040] The balloon 14 is a compliant balloon, and the balloon 14 is a silicone balloon, a latex balloon, or a TPU balloon. Thus, when the inner cavity of the balloon 14 is filled with fluid, the shape and volume of the balloon 14 change accordingly and expand, so that when the embolization coil 300 kicks the tip of the balloon microcatheter 100 from the middle of the aneurysm cavity 21 to the aneurysm wall 22, the balloon 14 acts as a buffer between the second section 112 and the aneurysm wall 22, thereby preventing the second section 112 from contacting the aneurysm wall 22, and preventing the balloon microcatheter 100 from bending and deforming under the tension of the embolization coil 300, thereby preventing the tip of the balloon microcatheter 100 or the balloon microcatheter 100 from bending and pressing against the aneurysm wall 22 to rupture the aneurysm wall 22.

[0041] In this embodiment, the balloon 14 is independent of the second section 112, and the inner cavity of the balloon 14 is formed by the balloon 14 itself, that is, the inner cavity of the balloon 14 has no direct contact with the tube wall of the second section 112, and the distal end and the proximal end of the balloon 14 are bonded to the outer surface of the second section 112 by welding or glue. On the one hand, the distal and proximal ends of the balloon 14 are respectively fixed to the second section 112, and on the other hand, the balloon 14 is arranged on the side of the second section 112, so that when the inner cavity of the balloon 14 is filled with fluid, the second section 112 is The middle portion of the segment 112 is convex and curved toward the balloon 14, so that when the embolization coil 300 kicks the tip of the balloon microcatheter 100 from the middle of the aneurysm cavity 21 to the aneurysm wall 22, the inflated balloon 14 abuts against the aneurysm wall 22 and prevents the second segment 112 from abutting against the aneurysm wall 22, thereby preventing the tip of the balloon microcatheter 100 from directly contacting the aneurysm wall 22 and preventing the tip of the balloon microcatheter 100 or the balloon microcatheter 100 from bending and abutting against the aneurysm wall 22 to rupture the aneurysm wall 22.

[0042] In other embodiments, the inner cavity of the balloon 14 can also be formed between the balloon body of the balloon 14 and the tube wall of the second section 112, that is, the balloon 14 is a piece of balloon body wrapped around the side of the second section 112, and the four sides of the balloon body are bonded to the outer surface of the second section 112 by welding or glue, thereby ensuring the sealing of the connection between the balloon 14 and the second section 112, which not only prevents the fluid filled in the inner cavity of the balloon 14 from flowing into the blood vessel or the aneurysm cavity 21, but also allows the middle part of the second section 112 to bulge and bend toward the balloon 14 when the inner cavity of the balloon 14 is filled with fluid.

[0043] Furthermore, the proximal end of the balloon 14 and the distal end of the outer tube 12 are bonded by welding or gluing.

[0044] Furthermore, the stiffness of the second section 112 is less than that of the first section 111, thus taking into account both the support function of the proximal end and the flexibility of the distal end of the balloon microcatheter 100, which is beneficial for the balloon microcatheter 100 to pass through tortuous blood vessels and reduces the possibility of damage to the blood vessel wall, so that the balloon microcatheter 100 can smoothly reach the target position.

[0045] Preferably, the rigidity of the inner tube 11 gradually decreases from the proximal end to the distal end, so that the flexibility and bending resistance of the balloon microcatheter 100 are increasingly improved from the proximal end to the distal end, so as to facilitate the balloon microcatheter 100 to pass through tortuous blood vessels.

[0046] See also Figures 5 to 7 Furthermore, the inner tube 11 includes an inner layer 113 , an outer layer 114 , and an intermediate layer 115 disposed between the inner layer 113 and the outer layer 114 , and the intermediate layer 115 includes at least one of a braided segment 1152 and a spiral coil segment 1151 .

[0047] See also Figure 6 In this embodiment, the middle layer 115 includes a spiral coil segment 1151 extending from the proximal end to the distal end of the inner tube 11. The spiral coil segment 1151 is formed by spirally winding a wire around the outer periphery of the inner layer 113, and the wire is a stainless steel wire or a nickel-titanium alloy wire. The spiral coil segment 1151 spirally extends around the outer periphery of the inner layer 113, and the pitch of the spiral coil segment 1151 is 0.050 to 0.762 mm, and the pitch of the spiral coil segment 1151 gradually decreases from the proximal end to the distal end of the spiral coil segment 1151. On the one hand, the middle layer 115 has good continuity and excellent flexibility, so that the balloon microcatheter 100 has excellent anti-bending ability, which is beneficial to the delivery of the embolic spring coil 300, and the wire is not easy to leak out of the inner tube 11, so it will not cause damage to the blood vessel wall; on the other hand, it takes into account the support of the proximal end and the flexibility of the distal end of the balloon microcatheter 100, which is beneficial for the balloon microcatheter 100 to pass through tortuous blood vessels and reduces the possibility of damage to the blood vessel wall, so that the balloon microcatheter 100 can reach the target position smoothly.

[0048] Among them, the wire material can be a flat wire, the width of the flat wire is 0.025-0.254mm, the thickness of the flat wire is 0.012-0.051mm, and the width of the flat wire gradually decreases from the proximal end to the distal end of the spiral coil segment 1151, taking into account the support of the proximal end and the flexibility of the distal end of the balloon microcatheter 100, which is beneficial for the balloon microcatheter 100 to pass through tortuous blood vessels and reduces the possibility of damage to the blood vessel wall, so that the balloon microcatheter 100 can reach the target position smoothly.

[0049] Alternatively, the wire may be a round wire, and the wire diameter of the round wire gradually decreases from the proximal end to the distal end of the spiral coil segment 1151, which can also take into account the support of the proximal end and the flexibility of the distal end of the balloon microcatheter 100, which is beneficial for the balloon microcatheter 100 to pass through tortuous blood vessels and reduces the possibility of damage to the blood vessel wall, so that the balloon microcatheter 100 can reach the target position smoothly.

[0050] In other embodiments, the middle layer 115 may also be configured to include a braided segment 1152 and a spiral coil segment 1151 sequentially arranged from the proximal end to the distal end, so that the middle layer 115 has good continuity and excellent flexibility, and takes into account both the support of the proximal end of the balloon microcatheter 100 and the flexibility of the distal end, which is conducive to the balloon microcatheter 100 passing through a tortuous blood vessel, and reduces the possibility of damage to the blood vessel wall, so that the balloon microcatheter 100 can smoothly reach the target position. Similarly, the pitch of the spiral coil segment 1151 can be gradually reduced from its proximal end to its distal end, and the wire diameter or width of the spiral coil segment 1151 can also be gradually reduced from its proximal end to its distal end.

[0051] Preferably, the braiding density of the braided segment 1152 increases gradually from the proximal end to the distal end, wherein the braiding density refers to the number of warp and weft yarns per unit area of ​​the braided fabric.

[0052] See also Figure 7 In a modified embodiment, the middle layer 115 may also include a braided segment 1152 extending from the proximal end to the distal end of the inner tube 11, and the braided segment 1152 may be braided from stainless steel wire or nickel-titanium alloy wire. Preferably, the braiding density of the braided segment 1152 gradually increases from the proximal end to the distal end. The braiding density refers to the number of warp and weft yarns per unit area of ​​the braid.

[0053] The material of the inner layer 113 is PTFE, and the thickness thereof is 0.010-0.038 mm.

[0054] The outer layer 114 includes a substrate and a toughening agent doped in the substrate, and the content of the toughening agent gradually decreases from the proximal end to the distal end of the outer layer 114, wherein the substrate is a TPU layer, a Pebax layer, a nylon layer, or other polymer material layer, and the toughening agent and the fiber are added to toughen and strengthen the outer layer 114. Preferably, the toughening agent is a fiber, which has a reinforcing effect on the outer layer 114.

[0055] Preferably, in this embodiment, the outer layer 114 includes a substrate and carbon fibers doped in the substrate to improve the bending resistance of the outer layer 114. Even if the thickness of the outer layer 114 is small, it can still have excellent bending resistance and bending resistance. Therefore, both thickness and bending resistance can be taken into account, and the outer diameter of the balloon microcatheter 100 can be further reduced under the premise of ensuring the diameter of the delivery channel 15. Furthermore, the content of the carbon fibers gradually decreases from the proximal end to the distal end of the outer layer 114, so that the stiffness of the outer layer 114 gradually decreases from the proximal end to the distal end, and the balloon microcatheter 100 gradually becomes softer from the proximal end to the distal end.

[0056] Furthermore, the thickness of the distal end of the outer layer 114 is smaller than the thickness of its proximal end, and / or the stiffness of the distal end of the outer layer 114 is smaller than the stiffness of its proximal end, thereby taking into account both the support of the proximal end and the flexibility of the distal end of the balloon microcatheter 100, which is beneficial for the balloon microcatheter 100 to pass through tortuous blood vessels and reduces the possibility of damage to the blood vessel wall, so that the balloon microcatheter 100 can smoothly reach the target position.

[0057] Preferably, the thickness of the outer layer 114 gradually decreases from the proximal end to the distal end of the inner tube 11 .

[0058] Preferably, the outer diameter of the outer layer 114 gradually decreases from the proximal end to the distal end of the inner tube 11 .

[0059] Preferably, the outer layer 114 is designed in sections, each section is integrally arranged or laser welded together, and the thickness of each section decreases from the proximal end to the distal end, and / or the stiffness of each section decreases from the proximal end to the distal end.

[0060] Furthermore, the end portion 17 and the second section 112 are respectively provided with a developing ring 18 so that the instrument operator can observe the positions of the end portion 17 and the balloon 14 .

[0061] In summary, in the process of embolizing the aneurysm 200, the balloon microcatheter 100 proposed in the present invention, after the head end of the balloon microcatheter 100 reaches the aneurysm cavity 21, the liquid is transported to the inner cavity of the balloon 14 through the fluid channel 16, so that the balloon 14 is in an expanded state, and the middle part of the second section 112 is convex and curved toward the balloon 14, which can prevent the head end of the balloon microcatheter 100 from directly contacting the aneurysm wall 22. Even if the embolization spring coil 300 kicks the head end of the balloon microcatheter 100 from the middle of the aneurysm cavity 21 to the aneurysm wall 22, the side of the balloon 14 away from the second section 112 will contact the aneurysm wall 22, and the expanded balloon 1 The balloon 14 is close to the aneurysm wall 22 to avoid the head end of the balloon microcatheter 100 directly contacting the aneurysm wall 22, thereby increasing the contact area between the balloon 14 and the aneurysm wall 22 and reducing the impact of the balloon microcatheter 100 on the aneurysm wall 22. The tension provided by the balloon 14 can also effectively prevent the second section 112 from bending and deforming under the tension of the embolization coil 300, thereby preventing the head end of the balloon microcatheter 100 or the second section 112 from bending and pressing against the aneurysm wall 22 to rupture the aneurysm wall 22, and will not affect the delivery of the embolization coil 300, ensuring that the embolization coil 300 is smoothly released from the balloon microcatheter 100 and filled into the aneurysm wall 22.

[0062] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A balloon microcatheter, comprising: An inner tube, whose inner cavity forms a delivery channel for the embolic coil to pass through and be delivered to the aneurysm cavity, the distal end opening of the inner tube forms the outlet of the delivery channel, the inner tube has a first section and a second section arranged in sequence from the proximal end to the distal end, and the rigidity of the inner tube gradually decreases from the proximal end to the distal end; An outer tube is sleeved on the outer circumference of the first section, and a fluid channel is formed between the outer tube and the first section; characterized in that the balloon microcatheter also includes: A balloon is arranged on the side of the second section, the balloon is arranged side by side with the second section, and its distal end, proximal end and middle part are fixedly connected to the outer surface of the second section; the inner cavity of the balloon is connected to the fluid channel, and when the inner cavity of the balloon is filled with fluid to be in an expanded state, the middle part of the second section bulges and bends toward the balloon.

2. The balloon microcatheter according to claim 1, characterized in that: The inner tube includes an inner layer, an outer layer, and an intermediate layer disposed between the inner layer and the outer layer, wherein the intermediate layer includes at least one of a braided segment and a spiral coil segment, wherein the spiral coil segment spirally extends around the outer circumference of the inner layer.

3. The balloon microcatheter according to claim 2, characterized in that: The middle layer includes a spiral coil segment extending from the proximal end to the distal end of the inner tube, and the spiral coil segment is formed by spirally winding a wire around the outer circumference of the inner layer.

4. The balloon microcatheter according to claim 3, characterized in that: The wire is a flat wire, and the width of the flat wire gradually decreases from the proximal end to the distal end of the spiral coil segment; or, the wire is a round wire, and the diameter of the round wire gradually decreases from the proximal end to the distal end of the spiral coil segment.

5. The balloon microcatheter according to claim 3, characterized in that: The pitch of the helical coil segment gradually decreases from the proximal end to the distal end of the helical coil segment.

6. The balloon microcatheter according to claim 2, characterized in that: The middle layer includes a braided segment and a spiral coil segment which are sequentially arranged from the proximal end to the distal end.

7. The balloon microcatheter according to claim 6, characterized in that: The braiding density of the braided segment gradually increases from the proximal end to the distal end.

8. The balloon microcatheter according to claim 2, characterized in that: The outer layer includes a substrate and a toughening agent doped in the substrate, and the content of the toughening agent gradually decreases from the proximal end to the distal end of the outer layer.

9. The balloon microcatheter according to claim 2, characterized in that: The thickness of the outer layer at the distal end is smaller than that of the outer layer at the proximal end, and / or the stiffness of the outer layer at the distal end is smaller than that of the outer layer at the proximal end.

10. The balloon microcatheter according to claim 2, characterized in that: The balloon is a compliant balloon.

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