Balloon for a balloon catheter

Abstract

The present invention relates to a balloon (1) for a balloon catheter (100), comprising: a plurality of inflatable balloon sections (10) arranged side by side along a longitudinal axis (x) of the balloon (1), wherein each two neighboring balloon sections (10) are connected to one another via a connecting section (11) forming a constriction of the balloon (1) in an inflated state of the balloon (1), wherein each balloon section (10) comprises a maximal outer diameter (Ds) perpendicular to the longitudinal axis (x) and a wall thickness (ts) in the inflated state, and wherein each connecting section (11) comprises an outer diameter (Dc) perpendicular to the longitudinal axis (x) and a wall thickness (tc) in the inflated state, wherein the maximal outer diameters (Ds) of the balloon sections (10) are larger than the outer diameters (Dc) of the connecting sections (11), and wherein the wall thicknesses (tc) of the connecting sections are larger than said wall thicknesses (ts) of the balloon sections (10).

Description

[0001] Balloon for a Balloon Catheter

[0002] The present invention relates to a balloon, particularly an ultra-high-pressure balloon, for a balloon catheter.

[0003] Such a balloon comprises a plurality of inflatable (e.g. spherical and sphere-hke shaped) balloon sections arranged side by side along a longitudinal axis of the balloon, wherein each two neighboring balloon sections are connected to one another via a connecting section forming a constriction of the balloon in an inflated state of the balloon. Such balloons are therefore also denoted as pearl chain balloons owing to the alternating arrangement of larger outer diameter balloon sections and smaller outer diameter (e.g. cylindrical) connecting sections.

[0004] Current ultra high-pressure balloons are often perceived by physicians as “bulky”. This is mostly attributed to the fact that high-strength materials (e.g. fiber reinforced and or highly oriented molecules) and high wall thicknesses are used to achieve the ultra-high rated burst pressures. This comes at the price that their crossing profile and bending stiffness is accordingly very high.

[0005] Common pearl chain balloons are not designed to achieve higher pressures, particularly ultra- high rated burst pressures. Merely increasing the overall wall thickness of the balloon renders the balloon sections very difficult to fold. As a consequence, the folded balloon diameter increases, and the bending stiffness is getting considerably larger. This also means that it becomes increasingly difficult to get such bulky balloons around strong bendings on a tortuous path. Hence, the trackability of the balloon severely deteriorates.

[0006] Therefore, based on the above, the problem to be solved by the present invention is to provide a balloon that can be inflated to high pressures, particularly ultra-high pressures (e g. larger than 30 atm), while at the same time offering more balloon conformability and trackability capabilities and a higher cracking pressure, particularly with the goal of breaking calcifications in a longitudinally limited fashion (in contrast to cylindrical balloons), so as to avoid large dissections. This problem is solved by a balloon having the features of claim 1 as well as by a balloon catheter having the features of claim 14. Preferred embodiments of these aspects of the present invention are stated in the corresponding dependent claims and are described below.

[0007] A balloon for a balloon catheter is disclosed, comprising

[0008] - a plurality of inflatable balloon sections arranged side by side along a longitudinal axis of the balloon, wherein each two neighboring balloon sections are connected to one another via a connecting section forming a constriction of the balloon in an inflated state of the balloon,

[0009] - wherein each balloon section comprises a maximal outer diameter perpendicular to the longitudinal axis and an (e.g. minimal) wall thickness in the inflated state, and wherein each connecting section comprises an outer diameter perpendicular to the longitudinal axis and a wall thickness in the inflated state, wherein the maximal outer diameters of the balloon sections are larger than the outer diameters of the connecting sections, and wherein the wall thicknesses of the connecting sections are larger than said wall thicknesses of the balloon sections.

[0010] The maximal outer diameter of the balloon sections, the outer diameter of the connecting sections, the wall thicknesses of the balloon sections, and the wall thicknesses of the connecting sections are preferably selected such that in the inflated state of the balloon a hoop stress (preferably according to Barlow’s formula) in the respective balloon section is less than 10 times larger than a hoop stress in the respective connecting section.

[0011] According to Barlow’s formula (see e.g. also Fig. 3 as described further down below), thinwalled spherical and sphere-like shapes (here referring to the balloon sections) feature up to twice the strength against internal pressure of thin-walled cylindrical or cylinder-like connection sections. Spherical sections exhibit equal hoop stresses in all surface directions. The hoop stresses of a spherical shape at a given internal pressure are equal to the axial stresses of a cylindrical shape (each possible cross section through the center of a sphere is identical with the cross section of a cylinder perpendicular to the axis assuming the diameter and wall thickness of both shapes are also equal) but two times lower compared to the hoop stresses of a cylindrical shape. Consequently, balloons with multiple spherical or sphere-like balloon sections being connected by cylindrical or cylinder-like shaped connecting sections having a smaller outer diameter than the balloon sections, and a larger wall thickness than the balloon sections have higher pressure capabilities than purely standard cylindrical balloon geometries. Thus, in the present invention, the connecting sections feature smaller outer diameters and increased wall thicknesses compared to the balloon sections to compensate the geometrical disadvantages of the connecting sections according Barlow’s formula.

[0012] The wall thickness of the balloon sections may be a minimal wall thickness of the respective balloon section comprised by the respective balloon section at a periphery of the respective balloon section where the respective balloon section comprises its maximal outer diameter.

[0013] An outer surface of the balloon sections in the inflated state of the balloon may comprise one of: a spherical shape, an ellipsoidal shape, a spheroidal shape.

[0014] An outer surface of the connecting section in the inflated state of the balloon may comprise one of: a cylindrical shape, a hyperbolic shape.

[0015] The balloon may be configured to be inflated with a pressure in the range from 25 atm to 50 atm, particularly of more than 30 atm and less than 40 atm, and to withstand this pressure in the inflated state, wherein particularly the balloon is configured to be inflated with a liquid medium.

[0016] An entire outside of the balloon may present a smooth, particularly protrusion-free, outer surface in the inflated state of the balloon.

[0017] The balloon may have a ratio of a maximal outer diameter Ds of each of the balloon sections to an outer diameter De of a neighboring connecting section (Ds:Dc) ofbetween 1.5: 1.0 , 1 :2 , 2:3 and 4.0: 1.0, preferably between 2.0: 1.0 and 3.5: 1.0 and more preferably between 2.8:1 and 3.2: 1. In a preferred embodiment, the ratio of a maximal outer diameter Ds of each of the balloon sections to an outer diameter De of a neighboring connecting section (Ds:Dc) is 2: 1.

[0018] The maximal outer diameter of the respective balloon section may be in the range from 2.50 mm to 3.50 mm, particularly in the range from 2.80 mm to 3.20 mm, particularly in the range from 2.90 mm to 3.10 mm, particularly in the range from 2.95 mm to 3.05 mm.

[0019] The outer diameter of the connecting sections may be in the range from 0.66 mm to 2.40 mm, particularly in the range from 0.80 mm to 2.20 mm, particularly in the range from 0.90 mm to 2.10 mm, particularly in the range from 0.95 mm to 2.05 mm, particularly in the range from 1.90 mm to 2.1 mm or particularly in the range from 0.90 mm to 1.10 mm. Such low diameter (cylindrical) connecting sections enable to withstand ultra-high pressures. The lower the diameter of the connecting sections the lower is the moment of inertia and consequently the lower is the bending stiffness, thus resulting in a better conformability.

[0020] The connecting sections may comprise a connecting section length (Lc) in the direction of the longitudinal axis and in the inflated state of the balloon in the range from 0.20 mm to 7.00 mm, particularly in the range from 0.80 mm to 2.00 mm, particularly in the range from 0.80 mm to 1.60 mm, particularly in the range from 0.90 mm to 1.10 mm, particularly in the range from 0.25 mm to 1.05 mm.

[0021] The total length of the balloon may be between 5 mm and 50 mm, preferably between 15 mm and 40 mm.

[0022] The (e.g. minimal) wall thickness of the balloon sections may be in the range from 20.00 pm to 45.00 pm, particularly in the range from 25.00 pm to 40.00 pm, particularly in the range from 28.00 pm to 35.00 pm, particularly in the range from 29.00 pm to 33.00 pm, particularly in the range from 29.00 pm to 31.00 pm.

[0023] Furthermore, the wall thickness of the connecting sections may be in the range from 140.0 pm to 300 pm, particularly in the range from 140.0 pm to 250 pm, more particularly in the range from 185.00 pm to 250.00 pm.

[0024] The connection sections are configured due to its outer diameter and wall thickness such that they cause stresses that are smaller than the stresses of the balloon sections at its maximum outer diameter.

[0025] Balloons with a Ds:Dc ratio of 2.8:1 to 3.2: 1, 2: 1 and a connecting section length of between 0.25 mm and 1.55 mm and wall thickness of the connecting section of more than 180 pm show rated burst pressures of more than 32 atm.

[0026] The balloon sections may comprise a wall thickness that decreases from a connection section, where the respective balloon section is (e.g. integrally) connected to a neighboring connecting section towards the periphery, where the respective balloon section comprises its minimal wall thickness.

[0027] The balloon may comprise a total number of balloon sections that is in the range from minimum 2 to 15, particularly in the range from 4 to 9. Particularly, due to the construction principle of the balloon the total number of connecting sections is always the total number of balloon sections minus one.

[0028] The (preferably spherical) balloon sections of the balloon may comprise a maximal outer diameter in the range from 2.90 mm to 3.1 mm (particularly in the range from 2.95 mm to 3.05 mm) and the respective (preferably cylindrical) connecting section comprises an outer diameter m the range from 0.90 mm to 1.10 mm (particularly m the range from 0.95mm to 1.05 mm) or in the range from 1.90 mm to 2.10 mm (particularly in the range from 1.95 mm to 2.05 mm). Furthermore, regarding these preferred embodiments, the connecting section length is preferably in the range from 0.9 mm to 1.1 mm (particularly 0.95mm to 1.05 mm). Furthermore, additionally, regarding these two preferred embodiments, the number of spherical sections is preferably 9. Furthermore, additionally, in these two preferred embodiments, said (e.g. minimal) wall thickness of the respective spherical portion is preferably in the range from 30 pm to 33 pm. Furthermore, additionally, in these two preferred embodiments, the wall thickness of the respective connecting section is preferably in the range from 184 pm to 196 pm, wherein particularly the wall thickness of the connecting sections is 185 pm or 195 pm.

[0029] In one embodiment, each of the balloon sections comprises a balloon section length (Ls) in the direction of the longitudinal axis (x), and the balloon comprises a balloon-connector length (Lsc) in the direction of the longitudinal axis (x), wherein the balloon-connector length (Lsc) is the sum of the balloon section length (Ls) and the connecting section length (Lc), wherein the balloon-connector length (Lsc) is larger than or equal to the maximal outer diameter (Ds) of each of the balloon sections.

[0030] In a preferred embodiment, the balloon-connector length (Lsc) is larger than or equal to the maximal outer diameter (Ds) of each of the balloon sections and smaller than or equal to two times the maximal outer diameter (Ds) of each of the balloon sections.

[0031] In a further preferred diameter, the balloon-connector length (Lsc) is larger than or equal to the maximal outer diameter (Ds) of each of the balloon sections and smaller than or equal to one and half times the maximal outer diameter (Ds) of each of the balloon sections. The balloon sections and / or the connecting sections may be formed out of or comprise one of the following materials: Polyamide, particularly polyamide 12 (PA12), polyethylene terephthalate (PET), polyamide 1010 (PA10), polyamide 610 (PA610). Particularly, polyamide 12 (PA12), i.e., Poly(dodecano- 12-lactam) having the CAS Number 24937-16-4, is a polymer having 12 Carbon atoms (Ci2H23NO)n. It can be made from co-aminolauric acid or laurolactam monomers that each have 12 carbons.

[0032] The balloon for a balloon catheter may have a total length from 20 mm to 30 mm and a total number of balloon sections from 4 to 10, wherein in the inflated state each balloon section has a spherical / ellipsoidal / spheroidal shape having a maximal outer diameter from 2.90 mm to 3.10 mm and a minimal wall thickness at the maximal outer diameter, and wherein each connecting section has a cylindrical / hyperbolic shape having a wall thickness of 140 pm to 250 pm, and a length in the direction of the longitudinal axis from 0.90 mm and 1.60 mm and an outer diameter from 0.90 mm and 2.10 mm, and wherein the balloon is made of a polyamide (and each balloon section comprises a wall thickness that decreases from a connection section towards a periphery of the balloon section). Such balloons show rated burst pressures of more than 25 atm.

[0033] The balloon for a balloon catheter may have a total length from 20 mm to 30 mm and a total number of balloon sections from 4 to 10, wherein in the inflated state each balloon section has a spherical / ellipsoidal / spheroidal shape having a maximal outer diameter from 2.90 mm to 3.10 mm and a minimal wall thickness at the maximal outer diameter, and wherein each connecting section has a cylindrical / hyperbolic shape having a wall thickness of more than 185 pm (and preferably less than 250 pm), and a connecting section length in the direction of the longitudinal axis from 0.90 mm and 1.6 mm and an outer diameter from 0.90 mm and 1.10 mm, and wherein the balloon is made of a polyamide (and each balloon section comprises a wall thickness that decreases from a connection section towards a periphery of the balloon section). Such balloons show rated burst pressures of more than 32 atm.

[0034] The balloon according to the present invention may be deflectable in the inflated state, when a force of about 0.2 N is applied to a middle section of the balloon perpendicular to the longitudinal axis (with the opposing ends of the balloon being fixed).

[0035] The balloons may be made by blow molding and / or thermoforming.

[0036] A further aspect of the present invention relates to a balloon catheter compnsing a catheter shaft having an inflation lumen, and a balloon according to the present invention, the balloon being arranged on a distal portion of the catheter shaft. The balloon catheter may comprise a connector at a proximal end of the catheter shaft that is in flow connection via the inflation lumen with an interior space of the balloon for inflating the balloon. In one embodiment the balloon catheter may comprise an outer shaft comprising an outer shaft lumen and an opening in an outer shaft sidewall, an inner shaft comprising an inner shaft lumen and an open proximal end, wherein the inner shaft is arranged within the outer shaft lumen so that a guide wire can be guided out from the outer shaft through the opening and into the inner shaft lumen, a metallic tube element comprising a metallic tube element lumen, wherein the metallic tube element is arranged within the outer shaft lumen, and a stiffening element, wherein the stiffening element is attached to the metallic tube element and extends distally into the outer shaft lumen.

[0037] The metallic tube element may be a hypotube. The bond between the metallic tube element and the stiffening element may be a welded joint.

[0038] The outer shaft and the inner shaft may be formed by one or more of the following materials or comprises one or more of the following materials: a polymer, polyamide, polyurethane, polyester such as polyethylene terephthalate, polyester copolymers such as Hyrtel (tradename), or polyester block amide such as PEBAX (tradename). The aforementioned materials are preferred since they can be used to produce a welded or fused connection to a broad range of materials. The inner shaft many be coated with a hydrophilic coating material.

[0039] According to one embodiment, the stiffening element comprises a proximal portion with a first radius, a distal portion with a second radius and a tapered central portion, wherein a proximal end of the central portion comprises the first radius and a distal part of the central portion comprises the second radius, wherein the first radius is larger than the second radius. The stiffening element may be a stiffening wire. According to this embodiment, the controllability of the catheter may be further increased.

[0040] In a preferred embodiment, the length of the stiffening element is between 100 mm and 300 mm. In a further preferred embodiment, the length of the stiffening element is between 150 mm and 200 mm. In one embodiment, the length of the tapered central portion is more than half of the length of the stiffening element, the length of the distal portion is less than half of the length of the central portion and the length of the proximal portion is less than half of the length of the distal portion. According to this embodiment, the controllability of the catheter may be further increased.

[0041] In one embodiment, at least a part of the proximal portion is attached to an inner sidewall of the metallic tube element. According to this embodiment, a more stable attachment between the stiffening element and the metallic tube element is achieved. The balloon catheter is configured to withstand a liquid medium having a pressure in the range from 25 atm to 50 atm, particularly of more than 30 atm and less than 40 atm.

[0042] The balloon catheter can comprise a guide wire lumen extending through the interior space of the balloon, wherein the guide wire lumen is configured to receive a guide wire of the balloon catheter. The guide wire lumen may extend from a distal tip of the catheter shaft to a guide wire exit port located on the distal portion of the catheter shaft (so-called rapid exchange or Rx balloon catheter) or on a proximal end section of the catheter (so-called OTW or over-the-wire balloon catheter).

[0043] The balloon catheter may comprise a tip forming a guide wire lumen that exits distally from the balloon. The guidewire may be used as a scoring element outside when the balloon is in the inflated state.

[0044] In the following, embodiments, examples as well as further features and advantages of the present invention are described with reference to the Figures, wherein

[0045] Fig. 1 shows a schematic illustration of an embodiment of a balloon according to the present invention;

[0046] Fig. 2A shows a detail of the embodiment shown in Fig. 1, wherein the individual dimensions of the balloon are indicated;

[0047] Fig. 2B shows a microscope photo of a part of a balloon;

[0048] Fig. 3 shows a perspective cross-sectional view of a connecting section of an embodiment of the balloon according to the present invention in order to illustrate Barlow’s formula;

[0049] Fig. 4 shows measured rated burst pressures for different embodiments of the balloon according to the present invention;

[0050] Fig. 5 illustrates conformability test of an embodiment of the balloon according to the present invention; Fig. 6 shows forces needed to bend different balloons according to the present invention compared to a cylindrical balloon (depth [mm] of corresponding bending shown on x axis);

[0051] Fig. 7 shows average tracking force over distance in tortuous anatomy (lower portion of Fig. 7) of different balloon catheters according to the present invention (“pearl chain catheter”) compared to a “standard balloon (cylindrical)” catheter;

[0052] Fig. 8 illustrates generation of multiple short axial cracks C using a balloon according to the present invention;

[0053] Fig. 9 shows measured pressures to crack a stenosis (crack pressure [atm]) for different embodiments of the balloon according to the present invention; and

[0054] Fig. 10 shows an embodiment of a balloon catheter according to the present invention using a balloon according to the present invention;

[0055] Fig. 11 shows a schematic illustration of different embodiments of a balloon according to the present invention;

[0056] Fig. 12 shows measured rated burst pressures for the different embodiments of Fig. 11 ;

[0057] Fig. 13 shows measured rated burst pressures for the different embodiments having different wall thicknesses; and

[0058] Fig. 14 shows a cross-section view of the ballon catheter at the guide wire exit port.

[0059] Fig. 1 shows in conjunction with Fig. 2A an embodiment of a balloon 1 according to the present invention. According thereto, the balloon 1 comprises a plurality of inflatable balloon sections 10 arranged side by side along a longitudinal axis x of the balloon 1. Preferably the balloon sections 10 comprise a spherical (or ellipsoidal, particularly spheroidal) shape. Furthermore, each two neighboring balloon sections 10 are connected to one another, particularly integrally, via a connecting section 11 forming a constriction of the balloon 1 in an inflated state of the balloon 1 , hence the name pearl chain balloon of such a configuration. In an inflated state, the connecting sections 11 can comprise a cylindrical (or hyperbolic) shape. Preferably, in all embodiments, the balloon sections 10 and the connecting sections 11 together form a single inflatable volume of the balloon. Furthermore, as depicted in Fig. 2A, each balloon section 10 comprises a maximal outer diameter Dsperpendicular to the longitudinal axis x and an (e.g. minimal) wall thickness tsin the inflated state. Similarly, each connecting section 11 comprises an outer diameter Dcperpendicular to the longitudinal axis x and a wall thickness tcin the inflated state. The maximal outer diameters Dsof the balloon sections 10 are larger than the outer diameters Dcof the connecting sections 11, and the wall thicknesses tcof the connecting sections 11 are larger than said wall thicknesses tsof the balloon sections 10. Particularly, this is based on considerations relating to Barlow’s formula which is described in more detail below and allows to compensate the larger hoop stresses present in cylindrical (and similar) shapes compared to spherical (and similar) shapes.

[0060] Particularly, as also indicated in Fig. 2A, said wall thickness ts of the respective balloon section 10 can be a minimal wall thickness of the respective balloon section 10 comprised by the respective balloon section 10 at a circumferential periphery P of the respective balloon section 10. The respective balloon section 10 comprises its maximal outer diameter Dsat this periphery P. An entire outside la of the balloon presents a smooth, particularly protrusion-free, outer surface in the inflated state of the balloon.

[0061] The distance between peripheries P of two neighboring balloon sections corresponds to the balloon-connector length Lsc which is the sum of the balloon section length Ls and the connecting section length Lc.

[0062] Regarding the maximal outer diameter Dsof the balloon sections 10 and outer diameter Dcof the connecting sections 11 and the wall thicknesses tsand tc, the balloon 1 can have the dimensions as stated above for the various examples / embodiments of the balloon according to the present invention.

[0063] Particularly, these dimensions can be selected to as to put emphasis on achieving a maximum rated burst pressure (RBP) paired with a minimum cracking pressure (cf. also Figs. 4 and 9). The rated burst pressure (RBP) is the pressure at which 99.9% of the balloons will not burst at or below this value with at least 95% confidence. The rated burst pressure was determined according to ISO 25539-2. Particularly, the outer diameter of the connecting sections 11 can be optimized for achieving a maximum RBP. Particularly, in case the stenosis is narrower than the outer diameter Dcof the connecting sections 11 , the cracking pressures will not differ from a cylindrical balloon. On the other hand, the selection of the dimensions of the balloon 1 can be used to put emphasis on achieving multiple short axial dissections (cf. also Fig. 8) and accepting increased stenosis cracking pressures. Such embodiments can be characterized by connecting sections 11 in between the sphere-like balloon sections 10 with a connecting section length Lcof the connecting sections 11 to limit crack propagation.

[0064] However, all embodiments according to the present invention facilitate consistently high rated burst pressures with low standard deviations (cf. Fig. 4). Particularly, the improved rated burst pressure characteristics can be related to the sphere-like balloon sections 10 having e.g. factor 0.5 hoop stresses compared to cylindrical shapes of the inner connecting sections 11 allowing the usage of smaller wall thickness ts (see below). Furthermore, pressures needed to crack stenoses decrease when the ratio Ds / Dc decreases.

[0065] According to Barlow’s formula thin-walled (here referring to the wall thickness / outer diameter ratio of the shape) spherical and sphere-like shapes feature up to twice the strength against internal pressure of thin-walled cylindrical or cylmder-like shapes as shown in Fig. 3. Spherical balloon sections exhibit equal hoop stresses in all surface directions. The hoop stresses of a spherical shape at a given internal pressure are equal to the axial stresses of a cylindrical shape (each possible cross section through the center of a sphere is identical with the cross section of a cylinder perpendicular to the axis assuming the diameter and wall thickness of both shapes are also equal) but two times lower compared to the hoop stresses of a cylindrical shape. Consequently, spherical, or sphere-like balloon geometries have higher pressure capabilities than cylindrical balloon geometries (connecting sections). Thus, in the present invention, the connecting sections 11 feature smaller outer diameters Dcand increased wall thicknesses tccompared to the balloon sections 10 to compensate the geometrical disadvantages of the connecting sections 11 according to Barlow’s formula.

[0066] Particularly, in case of a cylinder, Barlow’s formula reads: ac= where ocis the hoop stress.

[0067] P'D

[0068] As described above, the hoop stress osfor a spherical shape is as=

[0069] For a typical distribution of wall thickness according to an embodiment of the present invention as shown in Fig. 2B. The wall thickness tccan be about 180.70 pm in the respective connecting section 11 (value DST1 in Fig. 2B) which decreases towards the periphery P to the minimal wall thickness tsof the respective balloon section 10 of about 30.703 pm (value DST3 in Fig. 2B). A wall thickness of the balloon section DST2 towards a connection section may be 84.678 pm). The wall-thickness was measured via the cross sections under a microscope and a white light interferometer. Alternatively, it can be measured by a thickness caliper.

[0070] Particularly, in the embodiment of Fig. 2B, the outer diameter Dcof the connecting sections 11 is 1.0 mm, and the maximal outer diameter of the balloon sections is 3.0 mm. Thus, in the inflated state, a hoop stress osaccording to Barlow’s formula in the respective balloon section 10 in the plane of the periphery P is about 9 times larger than a hoop stress ocin the respective connecting section 11. Particularly, as indicated in Fig. 4 (design A), such a selection of dimensions yields a favorable rated burst pressure of about 35 atm.

[0071] Fig. 4 shows rated burst pressures for different designs of a balloon 1 having four balloon sections. Design A corresponds to a balloon 1 having a maximal outer diameter Ds of 3.0 mm and an outer diameter Dc of 1.0 mm and a connecting section length of 1 mm, while design D corresponds to a balloon 1 having a maximal outer diameter Ds of 3.0 mm and an outer diameter Dc of 2.0 mm and a connecting section length of 1 mm. The wall thickness tcof the connecting sections 11 are stated in parenthesis on the x-axis (tsis about 30pm, respectively). As indicated, the balloons of design A and design D shown in Fig. 4 have two different wall thicknesses namely design A has a wall thickness (ts) at the connection section of 0. 190 mm or 0. 180 mm, design D has a wall thickness (ts) at the connection section of 0.245 mm or 0.180 mm). The balloon with design A having the same wall thickness of the connecting sections as the balloon of design D, namely a wall thickness of the connecting section of 0.180 mm, has a higher rated burst pressure than the balloon of design D. The total length of the design A and design D balloon is 30 mm, respectively.

[0072] Consequently, further improvement of the rated burst pressures of these types of balloon shapes can be achieved by increasing the wall thickness across all applied shapes of the balloon geometry. While it is possible to achieve ultra-high RBPs of up to 35 atm for 3.0 balloons already with standard balloon material like Polyamide 12 as described above, switching to other materials like PAI 010 or PA610 (e.g. Greenline IS & 2S), or even PET, known for their higher tensile strength, would further increase the RBP. Particularly, Rated Burst Pressures (RBP) are substantially increased compared to cylindrical standard balloons. Furthermore, spherical shapes and increased wall thickness tcin the connecting sections 11 result in ultra-high pressure (UHP) resistance of the respective balloon.

[0073] Furthermore, Figs. 5 and 6 demonstrate the improved conformability capabilities that can be achieved by a balloon geometry featuring multiple low diameter (Dc) cylindrical connecting sections 11 and multiple larger diameter balloon sections (Ds) evenly distributed over the balloon length. In the graph of Fig. 6, “cyl” denotes a standard cylindrical balloon, while “desD” corresponds to the balloon of design D and “desA” to design A described above.

[0074] The moment of inertia Izof a cylindrical connection section can be described by Iz = 4 it • (R4- r4), wherein R is the outer radius (e.g. half the outer diameter) and r is the inner radius (e.g. half the inner diameter) of the connection section.

[0075] Particularly, the cylindrical smaller diameter connecting sections 11 of such a balloon geometry feature a reduced moment of inertia compared to a standard cylindrical balloon with invariant diameter. The reduced moment of inertia results in an improved axial conformability because lower bending moments are required to inflect the balloon in inflated condition compared to inflated standard balloons of the same size. Improved conformability reduces risks connected to straightening of tortuous vessels. Furthermore, decreasing the distance between the spherical balloon sections 10 to extent the regions of low moment of inertia leads to further improved conformability because the share of low moment of inertia regions increases.

[0076] Furthermore, Fig. 7 demonstrates that the principal pearl chain catheter design according to the present invention shows advantages in tortuous 90° track tests (lower portion of Fig. 7. Again, the lower diameter connecting sections 11 support easier tracking of a balloon catheter employing a balloon 1 according to the present invention. Particularly, improved trackability capabilities can be achieved with the same balloon geometry characteristics as described for improved conformability capabilities. Multiple, evenly over the balloon length distributed lower diameter connecting sections 11 provide sections of low moment of inertia and the subsequently reduced bending moments lower friction in tortuous anatomy because the balloon sections 10 of the catheter conform more easily to the anatomy, even in folded condition.

[0077] Another option to improve trackability is the optimization of the packing density of the folded spherical or sphere-like balloon sections 10. Typically, folded balloons still contain areas in which the folded membranes do not touch each other completely but are separated by air. Increasing the packaging density involves the reduction of the diameter of the folded spherical or sphere-like balloon sections, hence the moment of inertia and consequently lower friction in tortuous anatomy.

[0078] Further, a balloon angioplasty of a stenosis with a typical cylindrical balloon usually initiates a crack at the edge of the stenosis which propagates over the full length of the stenosis with the risk to create one large longitudinal dissection surface. A row of spherical balloon sections 10 with a specific separation (e.g. Lc=2.0 mm for a chain of balloon sections 10 having an outer diameter Ds=3.0 mm) to each other replaces such a long axial crack by multiple short axial cracks and a lowered risk for large dissections as shown in Fig. 8 on the lower right-hand side. Fig. 9 shows typical crack pressures needed to crack a stenoses for various embodiments. The wall thickness of the respective connecting section is stated on the x-axis.

[0079] Finally, Fig. 10 shows an application of a balloon according to the present invention in the framework of a balloon catheter 100. Particularly, such a balloon catheter can be realized as a a rapid exchange (Rx) or over-the wire (OTW) system.

[0080] Particularly, the balloon catheter 100 comprises a catheter shaft 101 comprising an inflation lumen 102, and a balloon 1 according to the present invention, wherein the balloon 1 being arranged on a distal portion 101a of the catheter shaft 101. Furthermore, the balloon catheter 100 comprises a connector 108 (e.g. in form of a Luer connector) at a proximal end of the catheter shaft 101, wherein the connector 108 is in flow connection via the inflation lumen 102 with an interior space of the balloon 1 for inflating the balloon 1.

[0081] Preferably, the inflation lumen 102 and the connector 108 are configured to guide and withstand a liquid medium having a pressure in the range from 25 atm to 50 atm, particularly of more than 30 atm an less than 40 atm.

[0082] Furthermore, the balloon catheter 100 comprises a guide wire lumen 104 extending through the interior space of the balloon 1, wherein the guide wire lumen 105 is configured to receive a guide wire 105 of the balloon catheter 100. As already mentioned above, the guide wire lumen 104 can extends from a distal tip 107 of the catheter shaft 101 to a guide wire exit port 106 located on the distal portion 101a of the catheter shaft (Rx system) or on a proximal end section of the catheter (OTW system). Furthermore, the shaft 101 can comprise a hypotube with jacket at a transition to the connector 108.

[0083] Further, preferably, specific areas of the balloon catheter such as the guide wire exit port 106, the shaft 101 are reinforced to endure the ultra-high pressures stated above.

[0084] A cross-section view of the balloon catheter at the guide wire exit port (marked at DETAIL A in Fig. 10) is given at Fig. 14. Fig. 11 shows a schematic illustration of different embodiments of a balloon according to the present invention (Vers.) having different numbers of balloon sections (No. of spheres), different outer diameters of the connection section (connector OD) and different length of the connection sections (connecting section length Lc). The outer diameter of the balloon sections is 3 mm, respectively.

[0085] Fig. 12 shows measured rated burst pressures for the different embodiments of Fig. 11. It can be seen that balloons with connection sections having an outer diameter of 1 mm show higher rated burst pressure than balloons with connection sections having an outer diameter of 2 mm. It should be noted that a balloon having a length of the connection sections of 7 mm shows lower rated burst pressures compared to balloons having a connecting section length of less than 2 mm.

[0086] Fig. 13 shows measured rated burst pressures for a polyamide balloon 1 having six balloon sections. The outer diameter of the balloon sections is 3 mm, respectively. The outer diameter of the connection sections is 1 mm and the length of the connection sections are 1 mm, respectively. The wall thicknesses of the connection sections (balloon tube WT) are 0.195 mm, 0.180 mm and 0.145 mm. It can be seen that with increasing wall thickness of the connection sections the rated burst pressure increases.

[0087] The present invention offers the advantage of ultra-high pressure capability due to a balloon geometry composed from e g. spherical balloon sections and e g. cylindrical connecting sections The balloon sections allow an optimized distribution of stresses which allow ultra-high pressures. The connecting sections feature smaller diameters and increased wall thickness which also support ultra-high pressure capability. Furthermore, the smaller diameter connecting sections of the pearl chain balloon feature a reduced moment of inertia compared to a standard cylindrical balloon. The improved moment of inertia results in an improved axial conformability of the balloon in inflated condition com-pared to inflated standard balloons of the same size. Improved conformability reduces risks connected to straightening of tortuous vessels. Even in a folded condition the above-mentioned smaller diameter connecting sections feature a lower moment of inertia compared to folded standard cylindrical balloons of the same size. The consequently improved axial conformability in folded conditions results in an optimized trackability because the conforming balloon cause less friction with tortuous vessels.

[0088] Fig. 14 illustrates a cross-section view of the balloon catheter 100 at the guide wire exit port 106. The balloon catheter 100 comprises an outer shaft 107 comprising an inflation lumen 102 and an inner shaft 108 comprising a guide wire lumen 104. The inner shaft 108 is arranged within inflation lumen 102. The inner shaft 108 comprises an open proximal end which is attached to the outer shaft 107 at an opening of a sidewall of the outer shaft 107 to form a guide wire exit port 106 that enables a guide wire to be guided out from the outer shaft 107 through the guide wire exit port 106 and into the guide wire lumen 104. The attachment between the inner shaft 108 and the outer shaft may be achieved by an adhesive, a heat treatment or a welding process which forms a material-locking bond between the outer shaft 107 and the inner shaft 108. The balloon catheter 100 comprises a metallic tube element 109 (hypotube) comprising a metallic tube element lumen 114, wherein the metallic tube element 109 is arranged within the inflation lumen 102. The balloon catheter 100 comprises a stiffening element 110, wherein the stiffening element 110 is attached to the metallic tube element 109 and extends distally into the inflation lumen 102. The stiffening element 110 comprises a proximal portion 111 with a first radius, a distal portion 113 with a second radius and a tapered central portion 112, wherein the first radius is larger than the second radius. A part of the proximal portion 111 is attached to an inner sidewall of the metallic tube element 109

Claims

Claims1. Balloon (1) for a balloon catheter (100), comprising:- a plurality of inflatable balloon sections (10) arranged along a longitudinal axis (x) of the balloon (1), wherein each two neighboring balloon sections (10) are connected to one another via a connecting section (11) forming a constriction of the balloon (1) in an inflated state of the balloon (1),- wherein each of the balloon sections (10) comprises a maximal outer diameter (Ds) perpendicular to the longitudinal axis (x) and a wall thickness (ts) in the inflated state, and wherein each of the connecting sections (11) comprises an outer diameter (Dc) perpendicular to the longitudinal axis (x) and a wall thickness (tc) in the inflated state, wherein the maximal outer diameter (Ds) of each of the balloon sections (10) is larger than the outer diameter (Dc) of each of the connecting sections (11), and wherein the wall thicknesses (tc) of each of the connecting sections (11) is larger than the wall thickness (ts) of each of the balloon sections (10).

2. The balloon according to claim 1, wherein the maximal outer diameters (Ds) of the balloon sections (10), the outer diameters (Dc) of the connecting sections (11), the wall thicknesses (ts) of the balloon sections (10), and the wall thicknesses (tc) of the connecting sections (11) are selected such that in the inflated state of the balloon (1) a hoop stress (os) in the respective balloon section (10) is less than 10 times larger than a hoop stress (oc) in the respective connecting section (11).

3. The balloon according to claim 1 or 2, wherein each of the balloon sections (10) has a minimal wall thickness (ts) at its maximal outer diameter (Ds).

4. The balloon according to one of the preceding claims, wherein in the inflated state of the balloon (1) each of the balloon sections (10) comprises one of: a spherical shape, an ellipsoidal shape, a spheroidal shape and / or each of the connecting sections (11) comprises one of: a cylindrical shape, a hyperbolic shape.

5. The balloon according to one of the preceding claims, wherein the balloon (1) is configured to be inflated with a pressure in the range from 25 atm to 45 atm, particularly of more than 30 atm and less than 40 atm, and to withstand this pressure in the inflated state, wherein particularly the balloon (1) is configured to be inflated with a liquid medium.

6. The balloon according to one of the preceding claims, wherein a ratio of the maximal outer diameter (Ds) of each of the balloon sections to an outer diameter (De) of a neighboring connecting section (Ds:Dc) is between 1.5:1.0 and 4.0: 1.0, particularly between 2.0: 1.0 and 3.5: 1.0.

7. The balloon according to one of the preceding claims, wherein the maximal outer diameter (Ds) of each of the balloon sections (10) is in the range from 2.50 mm to 3.50 mm, particularly in the range from 2.90 mm to 3. 10 mm and / or wherein the outer diameter (Dc) of each of the connecting sections (11) is in the range from 0.80 mm to 2.40 mm, particularly in the range from 0.90 mm to 2.10 mm, more particularly in the range from 0.90 mm to 1.10 mm.

8. The balloon according to one of the preceding claims, wherein each of the connecting sections (11) comprises a connecting section length (Lc) in the direction of the longitudinal axis (x) and in the inflated state of the balloon (1) in the range from 0.20 mm to 7.00 mm, particularly in the range from 0.20 mm to 2.00 mm, more particularly in the range from 0.20 mm to 1.10 mm.

9. The balloon according to one of the preceding claims, wherein the wall thickness (ts) of each of the balloon sections (10) is in the range from 20.00 pm to 140.00 pm, and / or wherein the wall thickness (tc) of each of the connecting sections (11) is in the range from 140.0 pm to 250 pm, particularly in the range from 185.0 pm to 250 pm.

10. The balloon according to one of the preceding claims, wherein each of the balloon sections comprises a balloon section length (Ls) in the direction of the longitudinal axis (x), and the balloon comprises a balloon-connector length (Lsc) in the direction of the longitudinal axis (x), wherein the balloon-connector length (Lsc) is the sum of the balloon section length (Ls) and the connecting section length (Lc), wherein the balloon-connector length (Lsc) is larger than or equal to the maximal outer diameter (Ds) of each of the balloon sections..

11. The balloon according to one of the preceding claims, wherein each of the balloon sections (10) comprises a wall thickness that decreases from a connection region, where the respective balloon section is (10) connected to a neighboring connecting section (11),towards a periphery (P) of the balloon sections (10), where the respective balloon section (10) comprises its minimal wall thickness (ts).

12. The balloon according to one of the preceding claims, wherein the balloon (1) comprises a total number of balloon sections (10) that is in the range from 2 to 15, particularly in the range from 4 to 9.

13. The balloon according to one of the preceding claims, wherein each of the balloon sections (10) and / or each of the connecting sections (11) consists of or comprises one of the following materials: polyethylene terephthalate (PET), Polyamide, particularly polyamide 12, polyamide 1010 (PA10), polyamide 610 (PA610).

14. A balloon catheter (100) comprising a balloon (1) according to one of the preceding claims.

15. A balloon catheter (100) according to claim 14, wherein the balloon catheter comprises an outer shaft comprising an outer shaft lumen and an opening in an outer shaft sidewall; an inner shaft comprising an inner shaft lumen and an open proximal end, wherein the inner shaft is arranged within the outer shaft lumen so that a guide wire can be guided out from the outer shaft through the opening and into the inner shaft lumen; a metallic tube element comprising a metallic tube element lumen, wherein the metallic tube element is arranged within the outer shaft lumen; and a stiffening element, wherein the stiffening element is attached to the metallic tube element and extends distally into the outer shaft lumen.

16. A balloon catheter (100) according to claim 15, wherein the stiffening element comprises a proximal portion with a first radius, a distal portion with a second radius and a tapered central portion, wherein a proximal end of the central portion comprises the first radius and a distal part of the central portion comprises the second radius, wherein the first radius is larger than the second radius.

17. A balloon catheter (100) according to claim 16, wherein at least a part of the proximal portion is attached to an inner sidewall of the metallic tube element.

18. A balloon catheter (100) according to any of claims 14 to 17, wherein the balloon catheter is configured to withstand a liquid medium having a pressure in the range from 25 atm to 50 atm, particularly of more than 30 atm and less than 40 atm and wherein the balloon is configured to apply a crack pressure to a stenosis of more than 10 atm, particularly between 20 atm and 30 atm.

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