Blood pump with flow cannula

Abstract

To provide a flow cannula for a blood pump.SOLUTION: A blood pump 1 for supporting the patient's heart includes a flow cannula 4 having a distal end 10 and a proximal end 11 opposite the distal end 10, the distal end 10 of the flow cannula 4 configured to be connected to the heart or the blood vessel of the patient to establish fluid communication between the blood pump 1 and the patient's heart and blood vessel, respectively. The flow cannula 4 includes a distal portion 5 having the distal end 10, and a proximal portion 6 having the proximal end 11. The flow cannula 4 further includes an intermediate portion 7 attached to the distal portion 5 and the proximal portion 6, where the intermediate portion 7 allows twisting thereof with lower force than that when the distal portion 5 and the proximal portion 6 are twisted. The intermediate portion 7 is configured to be fully occluded by twisting the intermediate portion. At least a portion of the intermediate portion 7 either alone or in combination with the distal portion 5 is adapted to be permanently attached to the patient's heart or blood vessel.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a flow cannula for a blood pump for supporting the heart of a patient. The flow cannula is configured to couple the blood pump to the heart and blood vessels of a patient. The flow cannula may be separated such that the portion coupled to the heart or blood vessels remains inside the patient's thorax after removal of the blood pump. The present invention further relates to a method of removing the blood pump from a patient. [Background technology]

[0002] The blood pump may be inserted into a patient's blood vessel, such as the aorta, using a catheter, or may be placed in the chest cavity or even outside the patient's body. In some applications, particularly when the blood pump is not placed in a vessel, it may be necessary to establish a direct connection to the vessel or the heart, e.g., the left ventricle. The blood pump's flow cannula is inserted into an opening in the heart and secured to the wall of the heart to establish fluid communication between the blood pump and the patient's heart. The outflow from the blood pump may then be connected to the aorta to pump blood from the left ventricle directly to the aorta.

[0003] When the blood pump is no longer needed, for example because the heart has recovered, it is removed. However, complete removal of the flow cannula from the heart would usually require open-chest surgery, which would entail a high risk of dangerous bleeding, and the opening in the heart would have to be closed. Therefore, the flow cannula is usually separated, e.g. cut, so that the part connected to the heart remains inside the patient's thorax. Clips, clamps or the like are used to close the remaining part of the flow cannula. However, the flow cannula is usually cut close to the patient's skin to facilitate handling in case of the occurrence of complications. Thus, the remaining part of the flow cannula is usually relatively long and the clamps can be bulky. This can affect the surrounding tissue and can cause irritation or even inflammation. Otherwise, there may be a risk that the flow cannula, which may be relatively stiff and have a relatively large diameter, cannot be clamped tightly, so that blood leaks into the patient's thorax. Summary of the Invention [Problem to be solved by the invention]

[0004] It is therefore an object of the present invention to provide a flow cannula for a blood pump which can be occluded to stop blood flow and subsequently detached, preferably by a minimally invasive procedure, and more preferably with reduced interference with the portions of the flow cannula which remain inside the patient with surrounding tissue, as well as a blood pump including such a flow cannula. [Means for solving the problem]

[0005] This object is achieved according to the invention by a flow cannula and a method having the features of the independent claims. Preferred embodiments and further developments of the invention are specified in the claims dependent thereon.

[0006] According to the present invention, a flow cannula for a blood pump for supporting a patient's heart includes a distal end and a proximal end opposite the distal end along a longitudinal axis of the flow cannula. The distal end of the flow cannula is configured to be coupled to a patient's heart or blood vessel for the purpose of establishing fluid communication between the blood pump and the patient's heart and blood vessel, respectively. The flow cannula includes a distal portion having said distal end and a proximal portion having said proximal end. The flow cannula further includes an intermediate portion attached to at least one of the distal and proximal portions. The intermediate portion allows for at least one of its clamping and twisting, in particular twisting, with less force than at least one of the distal and proximal portions. The intermediate portion is configured to be fully occluded by its twisting. Throughout this disclosure, the term "distal" refers to a direction away from a user, e.g., a surgeon, toward the heart, and the term "proximal" refers to a direction toward the user.

[0007] At least a portion of the intermediate portion, either alone or in combination with the distal portion, is adapted to be permanently attached to the patient's heart or blood vessel. In other words, said portion of the intermediate portion, either alone or in combination with the distal portion, is adapted to remain inside the patient's body after removal of the blood pump. Conversely, preferably at least the proximal portion, and possibly the proximal and distal portions, in combination with the remaining portion of the intermediate portion, are adapted to be removed from the patient's body. Since only a small portion of the flow cannula is placed inside the patient, only minor irritation or inflammation is caused.

[0008] The flow cannula designed in multiple parts, in particular a proximal part, a distal part and a middle part, allows for improved separation of the flow cannula during removal of the blood pump, and the parts that will remain in the patient's body cause less interference with the surrounding tissue. The flow cannula can be easily occluded by twisting the middle part in a minimally invasive procedure. In particular, the middle part is configured to be twisted to completely occlude and stop the flow of blood through the flow cannula. The twisting of the middle part can be caused by twisting the proximal part relative to the distal part, because the twisting of the middle part requires less force than the twisting of at least the distal part, and preferably both the distal and proximal parts.

[0009] The mid-section can be easily and securely occluded because less force is required for twisting or clamping, or both clamping and twisting. A smaller clamp or clip is sufficient to occlude the mid-section of the flow cannula compared to the clamp or clip that would be required to occlude the distal section. Twisting the mid-section allows temporary occlusion of the flow cannula, which may then be finally closed by a clamp or clip or by other suitable means such as a cable, wire or the like. Because less force is required to manipulate the mid-section, the procedure of occluding the flow cannula and removing the proximal section can be performed minimally invasively and with less risk to the patient. Moreover, instead of or in addition to twisting the mid-section, a loop or cutting wire may be used, which is looped around the mid-section and clamps it by drawing the loop or cutting wire tightly. The term "clip" or "clamp" refers to a piece that is placed around a flow cannula, particularly the twisted portion of the middle section, to tightly and finally close it so that the flow cannula can be cut or otherwise separated. Clips or clamps may be applied in minimally invasive procedures. In contrast, known cannulas may require bulky instruments, such as scissors-like surgical clamps, to stop the flow of blood, which can only be performed in open chest surgery.

[0010] The distal and proximal portions of the flow cannula may be releasably interconnected by a releasable connector, such as, for example, a male and female connector, a screw, a bayonet mount, a quick coupling, a magnet, or the like. Alternatively, the distal and proximal portions of the flow cannula may be connected via a predefined break line, such as a circumferential notch. In this way, the proximal and distal portions can be separated with a small force while the intermediate portion remains attached to both the proximal and distal portions.

[0011] However, although releasably connected, accidental separation of the proximal and distal portions should be avoided. Thus, if a predetermined break line is provided, it should have minimal resistance to withstand low breaking forces. In particular, it may be advantageous to design the predetermined break line such that a hemostat or other instrument such as a clamp or cutting tool is required to separate the proximal and distal portions. For example, it may be possible to protect the predetermined break line by a cover, i.e., a tear strip or the like may be provided. One or more, for example 2, 3, 4, 5 or 6, guard filaments may be provided attached to the proximal and distal portions, respectively, for the purpose of holding the proximal and distal portions together. The guard filaments may be located outside the intermediate portion, for example evenly spaced around the circumference of the flow cannula. They may be cut or otherwise separated to allow separation of the proximal and distal portions from each other.

[0012] When separated from one another, the proximal and distal portions may be axially movable relative to one another, which may be accomplished by axially compressing or stretching the intermediate portion or by twisting the intermediate portion, bringing the proximal and distal portions closer together. Alternatively, the distal and proximal portions may be integrally formed and not intended to be separated. For example, the distal and proximal portions may form a single tubular member, with the intermediate portion disposed over the tubular member like a jacket.

[0013] More specifically, the intermediate portion of the flow cannula may have a distal end and a proximal end, with the distal end of the intermediate portion attached to the distal portion of the flow cannula and the proximal end of the intermediate portion attached to the proximal portion of the flow cannula. As a result, blood does not leak from the flow cannula while the flow cannula is preparing for complete separation because the intermediate portion bridges the gap between the proximal and distal portions even when the proximal and distal portions are separated. It will thus be appreciated that the intermediate portion is preferably attached to at least the distal portion, and preferably to both the proximal and distal portions, in a fluid-tight manner, for the purpose of directing the flow of blood between the distal and proximal portions. For example, the intermediate portion may be attached by gluing, welding, clamping, bonding, or in other ways. In embodiments in which both ends of the intermediate portion are not attached or rigidly fixed to the proximal and distal portions, respectively, the respective free ends may be disposed at least on or around the respective end portions.

[0014] In an embodiment, the intermediate portion is attached to the distal and proximal portions of the flow cannula so as to at least partially overlap at least one of the distal and proximal portions of the flow cannula, preferably individually. What that means is that when the proximal and distal portions of the flow cannula are interconnected during operation of the blood pump, the intermediate portion will not come into contact with the blood flow through the flow cannula if it completely overlaps the proximal and distal portions. Thus, the intermediate portion can be made of various materials that would not be suitable for long-term blood exposure. Furthermore, the intermediate portion can be made of very thin materials that would risk breaking if they had to conduct the blood flow during the entire operation of the blood pump. Only during separation of the flow cannula will the intermediate portion be in direct contact with the blood flow, as will be explained in more detail below. Thus, particularly, but not limited to, this embodiment, the intermediate section may have a wall thickness of less than about 150 μm, preferably about 30 μm, and may comprise a tubular polymer film such as polyethylene terephthalate (e.g., Dacron®), polyurethane, or ePTFE. For example, the wall thickness may range from about 5 μm to about 100 μm for polyurethane and about 300 μm to about 1,000 μm for ePTFE. Thin polymer films are particularly well suited to twisting, thereby completely occluding the flow cannula, as described above.

[0015] The intermediate portion may be gathered, particularly in the axial direction, when the distal and proximal portions of the flow cannula are interconnected. The intermediate portion may move in a bellows-like manner, i.e., fold in a zigzag manner, or may simply be compressed in the axial direction. If the intermediate portion is gathered or compressed when the proximal and distal portions are connected, it will unfold or decompress when the proximal and distal portions move away from each other without pulling it. In other words, no tension is present in the intermediate portion when the proximal and distal portions are separated. This allows for easy clamping and, if necessary, twisting of the intermediate portion without the need to hold tension in the intermediate portion, which is beneficial for minimally invasive procedures. However, in any embodiment, the intermediate portion may be extensible in the direction of the longitudinal axis.

[0016] Apart from that, in any embodiment, the intermediate portion is sized and dimensioned so as not to interfere with axial movement of the proximal and distal portions, i.e., the intermediate portion is not overly dense with respect to the proximal and distal portions. For example, a slight gap may be provided between the intermediate portion and at least one, and preferably both, of the proximal and distal portions. Because the intermediate portion may be attached to the proximal and distal portions, the intermediate portion may be slightly tapered, i.e., have a slightly larger diameter in the middle compared to its ends.

[0017] In other embodiments, particularly where the distal and proximal portions are integrally formed, the intermediate portion may include an attachment member at its distal end, such as a disk, configured to be attached, particularly permanently, to the patient's heart, for example by suturing. The proximal end of the intermediate portion is preferably attached to the proximal portion. In this embodiment, the proximal and distal portions of the flow cannula will not be separated but will be pulled out of the heart as a single piece. By pulling the proximal and distal portions, the intermediate portion is stretched or deployed as described above, twisted and clamped. The intermediate portion is cut, so that only the attachment member, together with a portion of the intermediate portion, is left in the patient to close the opening in the patient's heart. The proximal and distal portions are completely removed. In order to avoid accidental retraction of the proximal and distal portions, protective filaments similar to those described above are provided and secured to the attachment member and the proximal portion.

[0018] The attachment member is preferably made of a material that allows for suturing of the attachment member to the heart tissue, such as felt or the like. In one embodiment, the attachment member may include, for example, 3, 4, 5 or 6 radially extending sections with gaps between the sections. Twisting the intermediate portion causes the sections to circumferentially move closer together, thereby compressing the underlying heart tissue in a twisted manner around the opening, thereby narrowing the opening in the heart tissue, particularly when the proximal and distal portions are retracted from the heart. This reduces the wound size after the flow cannula is removed. The wound is then closed by the compressed attachment member and the portion of the intermediate portion that remains inside the patient.

[0019] In yet another embodiment, the intermediate portion may be attached to the distal and proximal portions such that the distal and proximal portions are axially spaced apart from one another and the intermediate portion is disposed between the distal and proximal portions. In other words, the proximal and distal portions are not directly connected to one another but are connected via the intermediate portion. In this embodiment, the intermediate portion directs the flow of blood between the proximal and distal portions during operation of the blood pump. Thus, in this particular embodiment, the intermediate portion may include a polymer tube, preferably a silicone tube or a polyurethane tube, that is suitable for long-term blood exposure.

[0020] In any of the above described embodiments, the intermediate portion is preferably a flexible tubular member. The proximal and distal portions of the flow cannula are also preferably tubular members. Advantageously, the distal portion of the flow cannula is as short as possible, and in any case is shorter in the longitudinal direction than the proximal portion of the flow cannula, the length of the distal portion being preferably less than 50%, more preferably less than 25%, and most preferably less than 15% of the length of the proximal portion. For example, the distal portion may be 0.5 cm to 3 cm, e.g. 1 cm, in length and the proximal portion may be 5 cm to 9 cm, e.g. 7 cm, in length. The flow cannula may have a diameter of about 2 to 15 mm, preferably about 6 to 8 mm.

[0021] The blood pump is preferably sized and configured to be placed within the patient's thoracic cavity. This allows for applications in which the blood pump is implanted entirely within the patient's body, e.g., coupled to the patient's heart and aorta. In other embodiments, the blood pump may include a pump device configured to be placed outside the body, with the flow cannula extending through the patient's skin.

[0022] The system may include a blood pump as described above and at least one clip or clamp sized and configured to be placed around the mid-portion to completely occlude the flow cannula. In particular, the clip or clamp may be sized and shaped for placement around the mid-portion when the proximal and distal members are spaced apart from one another. After the clip or clamp is placed around the mid-portion, the proximal portion of the flow cannula may be removed, for example, by cutting the mid-portion as described in more detail below.

[0023] An exemplary method of using a blood pump as described above, and in particular removing the blood pump from a patient, includes the following steps: If the proximal and distal portions of the flow cannula are connected, for example, using a releasable connector or a predefined break line, the proximal and distal portions are separated and axially separated from each other. The middle portion may then be deployed or extended, but remains connected to the proximal and distal portions. The middle portion is then occluded in order to occlude the flow cannula and stop the flow of blood through it. If necessary or indicated by the application, the middle portion may first be twisted in order to obtain a temporary occlusion. At the same time, by twisting the middle portion, its diameter is reduced, allowing a smaller clip to be used. The twisted or untwisted middle portion is then clamped by a clamp, clip or the like in order to completely and positively occlude the flow cannula. The proximal portion of the flow cannula may then be removed, for example, by cutting the middle portion at a location proximal to the clip. The distal portion remains inside the patient, along with a portion of the middle portion and the clip. The procedure can be performed minimally invasively. The parts remaining inside the patient are small and not bulky in order to reduce or avoid interference with surrounding tissue. Irritation and inflammation can be reduced or avoided.

[0024] In other exemplary embodiments, the proximal and distal portions form a single piece and will not be separated. The intermediate portion has an attachment member at its distal end that is firmly attached to the patient's heart, while the proximal end of the intermediate portion is attached to the proximal portion of the flow cannula. Once the flow cannula is removed, the single piece including the proximal and distal portions is pulled out of the heart, thereby allowing the intermediate portion to unfold and / or extend. Once it is pulled far enough out of the heart, it can be twisted and clamped and subsequently cut off. Only the distal portion of the intermediate portion remains inside the patient, along with the attachment member. This can further reduce the size of the material left in the patient and can improve healing of the myocardial punch opening.

[0025] The foregoing summary, as well as the following detailed description of the preferred embodiments, will be better understood when read in conjunction with the appended drawings. For purposes of illustrating the disclosure, reference is made to the drawings. The scope of the disclosure, however, is not limited to the specific embodiments disclosed in the drawings. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 illustrates a patient's heart with a blood pump attached thereto. [Figure 2a] FIG. 1 illustrates an embodiment of a flow cannula. [Figure 2b] FIG. 1 illustrates an embodiment of a flow cannula. [Figure 3a] FIG. 2c shows the flow cannula of FIGS. 2a and 2b in use. [Figure 3b] FIG. 2c shows the flow cannula of FIGS. 2a and 2b in use. [Figure 3c] FIG. 2c shows the flow cannula of FIGS. 2a and 2b in use. [Figure 3d] FIG. 2c shows the flow cannula of FIGS. 2a and 2b in use. [Figure 3e] FIG. 2c shows the flow cannula of FIGS. 2a and 2b in use. [Figure 4a] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 4b] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 4c] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 4d] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 5a] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 5b] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 5c] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 5d] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 5e] FIG. 13 illustrates a flow cannula according to another embodiment in use. [Figure 6] FIG. 2 shows an intermediate portion according to one embodiment. [Figure 7] FIG. 13 shows an intermediate portion according to another embodiment. [Figure 8a] 1A-1D show schematic diagrams of the attachment member in use; [Figure 8b] 1A-1D show schematic diagrams of the attachment member in use; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Referring to FIG. 1, the blood pump 1 is illustrated inserted into the patient's heart H. The blood pump 1 is placed in the thoracic cavity and directly connected to the left ventricle LV of the heart H using a flow cannula 4, which in this application is an inflow cannula, because blood is drawn into the flow cannula 4 and conveyed into the pump casing 20 through the inlet 2 using an impeller (not shown) in the pump casing 20, and out of the blood pump 1 through the outflow cannula 3 attached to the aorta AO. The flow cannula 4 has a distal portion 5 fixed to the wall of the heart H, a proximal portion 6 connected to the inlet 2 of the pump casing 20, and an intermediate portion 7 attached to the distal portion 5 and the proximal portion 6, as will be explained in more detail below. The blood pump 1 supports the patient's heart H. Once the blood pump 1 is to be removed, the flow cannula 4 is separated and the remaining distal portion of the flow cannula 4 is closed and left in the thoracic cavity.

[0028] The flow cannula 4 is illustrated in more detail in Figures 2a and 2b. Figure 2a shows an unassembled view for the purpose of illustrating the connection 12 between the proximal and distal portions 5, 6. The proximal and distal portions 5, 6 are releasably connected to each other, for example, using a predefined break line, which may be formed, for example, by a peripheral notch (see enlarged cutout) or by any other releasable connector, such as a screw, a male and female connector, a bayonet mount, etc. The flow cannula 4 has a distal end 10 that is inserted into the patient's heart H as illustrated in Figure 1, and an opposing proximal end 11 that is attached to the pump casing 20. The distal end 10 may be sloped or tapered to facilitate insertion into the heart H.

[0029] The intermediate portion 7 has a distal end 8 that is attached to the distal portion 5 and a proximal end 9 that is attached to the proximal portion 6 as shown in FIG. 2b. Thus, the intermediate portion 7 overlaps both the distal portion 5 and the proximal portion 6. It will be appreciated that the intermediate portion 7 may be attached to the distal and proximal portions 5, 6 such that it overlaps only one of them. The intermediate portion 7 is gathered onto the distal and proximal portions 5, 6. Because the distal and proximal portions 5, 6 are coupled as shown in FIG. 2a, the intermediate portion 7 does not have contact with the blood flowing through the flow cannula 4 during operation of the blood pump 1.

[0030] 3a-3e, an exemplary method of removing a flow cannula from a patient's body is described, for example during removal of the blood pump 1 of FIG. 1, including the flow cannula 4 of FIG. 2b. Although the blood pump 1 is shown as a centrifugal blood pump, it will be understood that the flow cannula 4 may be used in combination with other medical devices, particularly other types of blood pumps, such as axial blood pumps and mixed type (centrifugal / axial) blood pumps. FIG. 3a is substantially the same view as FIG. 2b, showing the flow cannula 4 during operation of the blood pump 1. After operation of the blood pump 1 has ceased, the flow cannula 4 must be separated in order to remove the proximal portion 6 from the patient. As illustrated in FIG. 3b, the proximal portion 6 is separated from the distal portion 5 by decoupling the releasable connector 12, which may be done, for example, by breaking the flow cannula 4 at a predetermined break line. Other coupling mechanisms, such as threaded connections, may be used but are not shown in FIG. 3b for simplicity. The distal portion 5 remains attached to the patient's heart H, while the proximal portion 6 is axially spaced from the distal portion 5. The intermediate portion 7 unfolds or stretches to bridge the created gap between the distal and proximal portions 5, 6. Thus, the intermediate portion 7 is attached to the proximal and distal portions 5, 6 in a fluid-tight manner.

[0031] Because the midsection 7 is made of a thin polymer film, it can be easily twisted to temporarily completely occlude the flow cannula 4, as shown in Fig. 3c, in order to stop the flow of blood through the flow cannula 4. A clip 13 is then placed around the twisted midsection 7 (Fig. 3d) for final occlusion, and the midsection 7 is separated, for example by cutting (Fig. 3e). The remaining section does not require much space in the thoracic cavity and may remain in the thoracic cavity without causing significant irritation or inflammation.

[0032] With reference to Figures 4a-4d, an exemplary method during removal of a blood pump according to another embodiment is described. In contrast to the embodiment of Figures 3a-3e, the flow cannula 14 does not overlap the distal and proximal portions 15, 16, but includes an intermediate portion 17 disposed between them and connected at a proximal end 18 to the proximal portion 15 and at a distal end 19 to the distal portion 16. Thus, the intermediate portion 17 is in contact with the blood flowing through the flow cannula 14 and is preferably made of a material suitable for long-term blood exposure, such as silicone or polyurethane. The intermediate portion 17 is not as thin as the intermediate portion 7 of the previous embodiment, but is more flexible than the distal and proximal portions 15, 16, allowing clamping, and, if applicable, twisting, with less force than at least the distal portion 15.

[0033] As shown in Figure 4b, the intermediate portion 17 is twisted to create a temporary complete occlusion of the flow cannula 14 to stop the flow of blood through the flow cannula 14. It will be appreciated that this step may be omitted and a clip 13 (Figure 4c) may be placed over the twisted or untwisted intermediate portion 17 to create a complete occlusion of the flow cannula 14. As in the previous embodiment, the intermediate portion 17 is then separated to remove the proximal portion 16 from the patient while the distal portion 15 remains attached to the patient's heart H (Figure 4d).

[0034] With reference to Figures 5a-5e, an exemplary method during removal of a blood pump according to yet another embodiment is described. The flow cannula 24 includes a jacket-like intermediate portion 27 including an attachment member 30, which may be in the form of a disk, plate or sheet at its distal end 29 opposite its proximal end 28, which is shown in more detail in Figures 6 and 7. The attachment member 30 is configured to be attached, e.g., sutured, directly to the patient's heart H and remain permanently attached to the heart H. Except for the attachment member 30, the intermediate portion 27 is substantially similar to the intermediate portion 7 of the embodiment of Figures 3a-3e, e.g., with respect to material and rigidity characteristics. The flow cannula 24 includes a tube having a proximal portion 26 and a distal portion 25 that are integrally formed. In contrast to the previous embodiment, the proximal portion 26 and the distal portion 25 will not be separated but will be formed as a single piece. The intermediate portion 27 is disposed on the tube and may in particular be coupled to the proximal portion 26 with a proximal end 28. It may be sufficient if intermediate portion 27 is attached to proximal portion 26 by a friction fit, although a firm and liquid-tight attachment may be preferred.

[0035] During operation of the blood pump, the attachment member 30, which may be made of a felt material or the like, is fixed, for example sutured, to the heart H, with the proximal portion 25 extending into the heart H (FIG. 5a). When the blood pump is to be removed, the tube including the proximal portion 26 and the distal portion 25 is pulled out of the heart H, as shown in FIG. 5b. Since the disk 30 is rigidly fixed to the heart H and the proximal end 28 of the intermediate portion 27 is attached to the proximal portion 26, the intermediate portion 27 will unfold or extend as shown in FIG. 5b. It will be understood that any fixation between the intermediate portion 27 and the proximal portion 26 is suitable and will allow this movement, for example a permanent fixation or a sufficiently strong friction fit. It may be possible for the proximal end 28 of the intermediate portion 27 to slide along the proximal portion 26.

[0036] To prevent the tube from being inadvertently pulled out of the heart, guard filaments 31 are provided and attach to the tube and attachment member 30, as shown in Figure 5a. They are cut or otherwise separated to allow the tube to be retracted, as shown in Figure 5b. The portion of the guard filament 31 that remains inside the patient's body is kept as short as possible. More than one guard filament 31 may be provided, for example 2, 3, 4, 5 or 6 guard filaments 31.

[0037] As in the previous embodiment, the intermediate portion 27 is twisted to temporarily close it (FIG. 5c) and stop the flow of blood through the flow cannula 24. This is done by twisting the proximal portion 26, which requires sufficient fixation of the intermediate portion 27 relative to the proximal portion 26. The intermediate portion 27 is then clamped by the clip 13 (FIG. 5d). Finally, the intermediate portion 27 is cut, so that the entire tube, including the distal portion 25 and the proximal portion 26 together with the cut part of the intermediate portion 27, is removed from the patient. Only the attachment member 30 with the distal part of the intermediate portion 27 remains attached to the heart H inside the patient, closing the opening of the heart H. As only a small part of the flow cannula 24 remains inside the patient, the risk of irritation or inflammation of the surrounding tissue can be reduced.

[0038] As shown in Figures 6 and 7, the attachment member 30 may be designed according to different embodiments. The attachment member is preferably made of or includes a material that allows suturing of the attachment member to the patient's heart. A suitable material may be felt or the like. The attachment member 30 may be a disk, a sheet or the like as shown in Figure 6, and may assume any suitable shape, such as round, circular, rectangular, polygonal or the like. For example, the surgeon may adapt the size and shape by cutting the edges of the attachment member 30.

[0039] In other embodiments, as shown in Figure 7, attachment member 30 may include multiple, e.g., three, four, five or six, sections 32 separated by respective gaps 33. Sections 32 extend radially from intermediate portion 27. Referring again to Figures 5c-5e and 8a and 8b, an advantage of providing sections 32 instead of a continuous disk or sheet is that during twisting of intermediate portion 27, sections 32 are twisted closer together, thereby narrowing the punched hole in the cardiac tissue and reducing wound size, as shown by the arrows in Figure 8b.

Claims

1. A flow cannula (4; 14; 24) for a blood pump (1) for supporting a patient's heart, the flow cannula (4; 14; 24) comprising a distal end (10) and a proximal end (11) opposite the distal end (10) along a longitudinal axis of the flow cannula (4; 14; 24), the distal end (10) of the flow cannula (4; 14; 24) being configured to be coupled to the patient's heart or blood vessel for the purpose of establishing fluid communication between the blood pump (1) and the patient's heart and blood vessel, respectively, the flow cannula (4; 14; 24) comprising a distal portion (5; 15; 25) having the distal end (10) and a proximal portion (6; 16; 26) having the proximal end (11). the flow cannula (4; 14; 24) further comprises an intermediate portion (7; 17; 27) attached to at least one of the distal portion (5; 15; 25) and the proximal portion (6; 16; 26), the intermediate portion (7; 17; 27) allowing its twisting with a lesser force than at least one of the distal portion (5; 15; 25) and the proximal portion (6; 16; 26), the intermediate portion (7; 17; 27) being configured to be completely occluded by its twisting, and at least a portion of the intermediate portion (7; 17; 27) being adapted to be permanently attached to the patient's heart or blood vessel, either alone or in combination with the distal portion (5; 15; 25).

2. 2. The flow cannula of claim 1, wherein the intermediate portion (7; 17; 27) of the flow cannula (4; 14; 24) has a distal end (8; 18; 28) and a proximal end (9; 19; 29), the distal end (8; 18; 28) of the intermediate portion (7; 17; 27) being attached or disposed to the distal portion (5; 15; 25) of the flow cannula (4; 14; 24) and the proximal end (9; 19; 29) of the intermediate portion (7; 17; 27) being attached or disposed to the proximal portion (6; 16; 26) of the flow cannula (4; 14; 24).

3. 3. The flow cannula according to claim 1 or 2, characterized in that the intermediate portion (7; 17; 27) is attached to at least one of the distal portion (5; 15; 25) and the proximal portion (6; 16; 26), preferably to both the distal and proximal portions (5, 6; 15, 16; 25, 26) of the flow cannula (4; 14; 24) in a liquid-tight manner, for the purpose of directing the flow of blood between the distal portion (5; 15; 25) and the proximal portion (6; 16; 26).

4. 4. The flow cannula according to any one of claims 1 to 3, characterized in that the intermediate portion (7; 27) is attached or arranged on the distal and proximal portions (5, 6; 25, 26) of the flow cannula (4; 24) such that it at least partially overlaps at least one, preferably each, of the distal and proximal portions (5, 6; 25, 26) of the flow cannula (4; 24).

5. 5. The flow cannula according to any one of claims 1 to 4, characterized in that the distal (5) and proximal (6) portions of the flow cannula (4) are releasably connected to each other.

6. 6. The flow cannula according to claim 5, characterized in that the intermediate portion (7) is axially gathered when the distal and proximal portions (5, 6) of the flow cannula (4) are interconnected.

7. 5. The flow cannula according to any one of claims 1 to 4, wherein the intermediate portion (27) comprises an attachment member (30) at its distal end (28), the attachment member (30) being configured for attachment to the patient's heart, preferably wherein a proximal end (29) of the intermediate portion (27) is attached to the proximal portion (26), more preferably wherein the distal portion (25) and the proximal portion (26) are integrally formed.

8. 4. The flow cannula according to claim 1, wherein the intermediate portion (17) is attached to the distal portion (15) and the proximal portion (16) of the flow cannula (14), whereby the distal portion (15) and the proximal portion (16) are axially spaced from each other and the intermediate portion (17) is disposed between the distal portion (15) and the proximal portion (16).

9. 9. A flow cannula according to any one of the preceding claims, characterized in that the intermediate section (7; 17; 27) is a flexible tubular member.

10. 10. The flow cannula according to any one of the preceding claims, characterized in that the intermediate section (7; 17; 27) is extensible in the direction of the longitudinal axis.

11. 11. The flow cannula according to any one of claims 1 to 10, characterized in that the intermediate portion (7; 27) has a wall thickness of about 5 μm to about 1,000 μm, preferably less than about 150 μm, more preferably less than about 50 μm, even more preferably about 30 μm.

12. 12. The flow cannula according to any one of claims 1 to 11, characterized in that the intermediate portion (7; 27) comprises a tubular polymer film, preferably a tissue ingrowth inducing polymer material, more preferably polyethylene terephthalate, or the intermediate portion (17) comprises a polymer tube, preferably a silicone or polyurethane tube.

13. A blood pump (1) for supporting a patient's heart, characterized in that it comprises a flow cannula (4; 14; 24) according to any one of claims 1 to 12.

14. 14. The blood pump of claim 13, wherein the blood pump is sized and configured to be placed within the patient's thoracic cavity.

15. 15. A system comprising a flow cannula (4; 14; 24) according to any one of claims 1 to 12 or a blood pump according to claims 13 or 14, and at least one clip (13) sized and configured to be placed around the intermediate portion (7; 17; 27) of the flow cannula (4; 14; 24) to completely occlude the flow cannula (4; 14; 24).

16. A method for removing a blood pump (1) from a patient, said blood pump (1) being in fluid communication with a heart or blood vessel of said patient via a flow cannula (4; 14; 24) comprising a distal end (10) and a proximal end (11) opposite said distal end (10) along a longitudinal axis of said flow cannula (4; 14; 24), said distal end (10) of said flow cannula (4; 14; 24) being coupled to the heart or blood vessel of said patient for the purpose of establishing said fluid communication between said blood pump (1) and said heart and blood vessel of said patient, respectively; the flow cannula (4; 14; 24) comprises a distal portion (5; 15; 25) having the distal end (10) and a proximal portion (6; 16; 26) having the proximal end (11), the flow cannula (4; 14; 24) further comprising an intermediate portion (7; 17; 27) attached to at least one of the distal portion (5; 15; 25) and the proximal portion (6; 16; 26), the method comprising twisting the intermediate portion (7; 17; 27) so as to become completely occluded to stop the flow of blood through the flow cannula (4; 14; 24).

17. 17. The method according to claim 16, further comprising the step of attaching a clip (13) around the twisted intermediate portion (7; 17; 27) for the purpose of positively occluding the flow cannula (4; 14; 24).

18. 18. The method of claim 16 or 17, further comprising the step of detaching the proximal portion (6; 16; 26) of the flow cannula (4; 14: 24) by separating the intermediate portion (7; 17; 27) at a location proximal to the clip (13), wherein at least a portion of the intermediate portion (7; 17; 27) remains permanently attached to the patient's heart or blood vessel, either alone or in combination with the distal portion (5; 15; 25).

19. 19. The method of any one of claims 16-18, further comprising the step of separating the proximal and distal portions to axially move the proximal and distal portions away from one another prior to twisting the intermediate portion.

20. 20. The method according to any one of claims 16 to 19, further comprising the step of unfolding or stretching the intermediate portion (7; 17; 27) before twisting.

21. 21. The method according to any one of claims 16 to 20, characterized in that it is performed in a minimally invasive surgery.

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