BLOOD PUMP FOR MECHANICAL CIRCULATORY SUPPORT FOR FONTAN PATIENTS

Abstract

The invention relates to a radial blood pump (1) for supporting a blood flow (106) in a human or animal heart (205) comprising a first and a second inlet channel (41, 42), a first outlet channel (51, 52), a first electric motor (71) comprising a first stator (77) and a first internal rotor (75), wherein the first electric motor (71) is configured to drive an impeller (2, 2a, 2b) arranged at an intersection of the first with the second inlet channel (41, 42), wherein the impeller (2, 2a, 2b) is connected to the first internal rotor (75) and wherein the impeller (2, 2a, 2b) comprises a merging portion (22) arranged at the intersection, where a merging of a first blood flow (106) coming from the first inlet channel (41) and a second blood flow (107) coming from the second inlet channel (42) takes place, wherein the impeller (2, 2a, 2b) is configured to pump the first and second blood flow (106, 107) from the first and second inlet channel (41, 42) via the merging portion (22) to the first outlet channel (51), a plurality of blades (20) comprised by the impeller (2, 2a, 2b), wherein the blades (20) form blade channels (21) comprised by the merging portion (22), wherein each blade (20) is arranged and configured to pump the first and second blood (106, 107) flow entering through the first and the second inlet channel (41, 42) towards the outlet channel (51), wherein the blood pump (1) is arranged and configured such that the first blood flow (106) and the second blood flow (107) meet at the merging portion (22), such that a pressure difference between the first and second blood flow (106, 107) is reduced before blood from first and second blood flow (106, 107) is pumped to the first outlet channel (51).

Claims

1. A radial blood pump (1), particularly a cavolpulmonary assist device, for supporting a blood flow (106) in a human or animal heart (205) comprising at least the following components: A first and a second inlet channel (41, 42), A first outlet channel (51, 52), A first electric motor (71) comprising a first stator (77) and a first internal rotor (75), wherein the first electric motor (71) is configured to drive An impeller (2, 2a, 2b) arranged at an intersection of the first with the second inlet channel (41, 42), wherein the impeller (2, 2a, 2b) is connected to the first internal rotor (75) and wherein the impeller (2, 2a, 2b) comprises a merging portion (22) arranged at the intersection, where a merging of a first blood flow (106) coming from the first inlet channel (41) and a second blood flow (107) coming from the second inlet channel (42) takes place, wherein the impeller (2, 2a, 2b) is configured to pump the first and second blood flow (106, 107) from the first and second inlet channel (41, 42) via the merging portion (22) to the first outlet channel (51), A plurality of blades (20) comprised by the impeller (2, 2a, 2b), wherein the blades (20) form blade channels (21) comprised by the merging portion (22), wherein each blade (20) is arranged and configured to pump the first and second blood (106, 107) flow entering through the first and the second inlet channel (41, 42) towards the outlet channel (51), characterized in that the blood pump (1) is arranged and configured such that the first blood flow (106) and the second blood flow (107) meet at the merging portion (22), such that a pressure difference between the first and second blood flow (106, 107) is reduced before blood from first and second blood flow (106, 107) is pumped to the first outlet channel (51).

2. Radial blood pump according to claim 1, wherein the blood pump (1) comprises a second electric motor (72) comprising a second stator (78) and a second internal rotor (76), wherein the second internal rotor (76) is rigidly connected to the first internal rotor (75).

3. Radial blood pump according to claim 2, wherein the first electric motor (71) is arranged in a first half space (S1) extending from a plane (103) extending orthogonally from an axis of rotation (104) of the impeller (2, 2a, 2b) comprising the first inlet channel (41) and the second electric motor (72) is arranged in a second half space (S2) extending from the said plane (103) comprising the second inlet channel (42).

4. Radial blood pump according to claim 1, wherein the impeller (2, 2a, 2b) is a double-suction impeller, particularly a symmetric double-suction impeller (2, 2a, 2b).

5. Radial blood pump according to claim 1, wherein the impeller (2b) is a closed double-suction impeller (2b), wherein the impeller (2b) comprises a first and a second shroud (24) at least partially covering the blades (20), and wherein the merging portion (22) comprises two eyes (23), particularly wherein the two eyes (23) each have a diameter that is larger than 2.5 mm.

6. Radial blood pump according to claim 5, wherein the first internal rotor (75) of the first electric motor (71) is arranged on the first shroud (24) and particularly wherein the second internal rotor (76) of the second electric motor (72) is arranged on the second shroud (24).

7. Radial blood pump according to claim 1, wherein the impeller (2) is an open impeller (2a), wherein the blades (20) protrude from a shaft (10) that extends along the axis of rotation (104) of the impeller (2, 2a), wherein the first internal rotor (75) of the first electric motor (71) and/or the second internal rotor (76) of the second electric motor (72) are comprised by the shaft (10).

8. Radial blood pump according to claim 7, wherein the first internal rotor (75) of the first electric motor (71) is arranged on a first portion of the shaft (10) that is located in a first half space (S1) extending from a plane (103) extending radially around an axis of rotation (104) of the impeller (2, 2a) comprising the first inlet channel (41) and wherein the second internal rotor (76) of the second electric motor (72) is arranged on a second portion of the shaft (10) that is located in a second half space (S2) extending from the plane (103) extending radially around the axis of rotation (104) of the impeller (2, 2a) comprising the second inlet channel (42).

9. Radial blood pump according to claim 1, wherein the first and the second inlet channel (41, 42) are arranged opposite to each other and wherein the blades (20) are configured such that a straight-line fluidic passage (105) is provided between the first inlet channel (41) and the second inlet channel (42) through the blade channels (21) of the impeller (2, 2a, 2b) and/or through the eyes (23) of the impeller (2, 2b), such that a pressure difference between the first and the second blood flow (106, 107) is reduced before the blood of the first and the second blood flow (106, 107) is pumped to the first or second outlet channel (51, 52).

10. Radial blood pump according to claim 1, wherein the radial blood pump (1) has a housing (3) comprising the first and/or the second stator (77, 78), the housing (3) encasing at least the following components: a) the impeller (2, 2a, 2b); b) the first and/or the second internal rotor (75, 76); wherein a distance (8, 9) between an inner wall portion (30) of the housing (3) and said components is at least 0.25 mm, preferably at least 0.5 mm throughout the blood pump (1).

11. Radial blood pump according to claim 1, wherein the blood pump (1) comprises an active magnetic bearing (62), particularly a bearingless first and/or second motor (71, 72) or wherein the blood pump (1) comprises a mechanic bearing (61).

12. Radial blood pump according to claim 1, wherein the blood pump (1) comprises a second outlet channel (52) to which blood from the first and/or second inlet channel (41, 42) can be pumped by the impeller (2, 2a, 2b), particularly wherein the second outlet channel (52) is arranged in a tangential direction with respect to the impeller (2, 2a, 2b).

13. System with a blood pump (1) according to claim 1, and a device for electric power transfer, wherein the system further comprises a sensor (11) for estimating a hemodynamic signal (300) and a controller (300) that is configured to adjust a pump rate according to the determined hemodynamic signal (300), wherein the sensor (11) is particularly a pressure sensor.

14. System according to claim 13, wherein the device for electric power transfer is configured to wirelessly transfer the electric power to the blood pump (1), wherein the electric power transfer device comprises a power receiver and a power transceiver, wherein the power receiver is electrically connected to the blood pump (1) and configured for providing the blood pump (1) with electric energy transferred from the electric transceiver to the electric receiver.

15. Method for adjusting a pump rate according to a hemodynamic signal (300) with a system according to claim 13, comprising the steps of: Determining at least one hemodynamic signal (300) of a patient having implanted the radial blood pump (1); Determining from the determined hemodynamic signal (300) a required pump output rate for the first and/or second output channel (51, 52); Adjusting the radial blood pump (1) such that the determined pump output rate is achieved.

Description

[0115] In the following, the invention is explained in detail with reference to exemplary embodiments shown in the figures. It is noted that the drawings are not necessary to scale. It is shown in

[0116] FIG. 1 a cross-sectional view of a radial blood pump according to the invention with an open impeller and mechanical bearings;

[0117] FIG. 2 a perspective view of a radial blood pump according to the invention with an open impeller and mechanical bearings;

[0118] FIG. 3 a cross-sectional view of a radial blood pump according to the invention with an open impeller and merged magnetic bearings;

[0119] FIG. 4 a cross-sectional view of a radial blood pump according to the invention with an open impeller and separate magnetic bearings;

[0120] FIG. 5 a cross-sectional view of a radial blood pump according to the invention with a closed impeller and mechanical bearings;

[0121] FIG. 6 a cross-sectional view of a radial blood pump according to the invention with a closed impeller and separate magnetic bearings;

[0122] FIG. 7 a cross-sectional view of a radial blood pump according to the invention with a closed impeller and merged magnetic bearings;

[0123] FIG. 8 a cross-sectional view of a radial blood pump according to the invention with a closed impeller and separate magnetic bearings;

[0124] FIG. 9 a flow profile through a radial blood pump according to the invention with a closed impeller;

[0125] FIG. 10 a system according to the invention with a blood pump and a pressure sensor; and

[0126] FIG. 11 a schematic flow diagram of a method for controlling with the system according to the invention.

[0127] FIG. 1 to FIG. 9 show various views and embodiments of the radial blood pump 1. In all depicted embodiments the blood pump 1 is designed symmetrically with respect to a central point 100 where the vertical axis 101 and the horizontal axis 102 intersect, or to a radial plane 103 extending orthogonally to the vertical line 101 and comprising the horizontal line 102. The vertical line 101 corresponds to the axis of rotation 104 of a single impeller 2 that is arranged in the housing 3 of the blood pump 1.

[0128] The symmetric pump design, particularly the oppositely arranged inlet channels 41, 42 and outlet channels 51, 52, reduces hydraulic forces on the impeller 2 and thus the bearings 60.

[0129] The radial plane 103 divides the space in a first half space S1 comprising the first inlet channel 41 of the pump 1 and a second half space S2 comprising a second inlet channel 42 of the pump 1.

[0130] The first and the second inlet channel 41, 42 are arranged opposite of each other and form a straight tube.

[0131] When the radial blood pump 1 is implanted in a patient, the first inlet channel 41 is connected to the superior vena cava 200, while the second inlet channel is connected to the inferior vena cava 201.

[0132] The blood flow 200 entering the radial blood pump 1 is depicted as arrows.

[0133] The impeller 2 of the radial blood pump 1 rotates around the axis of rotation 104 and is centered on the central point 100. In the embodiments shown, the pump 1 always comprises two outlet channels 51, 52 that are arranged on opposite sides pointing in a radial direction of the radial blood pump 1.

[0134] The first and second outlet channel 51, 52 extent tangentially with respect to the impeller 2.

[0135] The impeller 2 is driven by a first and a second electric motor 71, 72, wherein in the depicted embodiments the first electric motor 71 is arranged in the first half space S1, while the second electric motor 72 is arranged in the second half space S2.

[0136] The impeller 2 is designed as a double-suction impeller 2 comprises a plurality of blades 20 that form blade channels 21 through which the blood is pumped towards at least one outlet channel 51, 52.

[0137] The first and the second electric motor 71, 72 comprise motor coils 73 and motor magnets 74 and are brushless DC motors, facilitating a contactless actuation and requiring less maintenance.

[0138] The motor coils 73 are arranged in the housing 3 of the pump 1 and can be connected to a power supply and a controller controlling the motor speed (not shown). The housing 3 therefore comprises or can be considered the first and second stator of the first and the second electric motor 71, 72 respectively.

[0139] The motor magnets 74 of the first and the second motor 71, 72 are arranged on a first and second rotor 75, 76 of the first and second motor 71, 72 respectively.

[0140] The first and the second rotor 75, 76 are rigidly connected or coupled to each other such that the first and the second motor 71, 72 always turn at the same speed.

[0141] The presence of two independently driven but synchronized electric motors 71, 72 with rigidly connected rotors 75, 76 provides a failsafe option to the radial blood pump 1, in case one motor is damaged or otherwise compromised such that it could not maintain a desired pump speed. In case one motor fails the other motor is capable to maintain a desired pump speed or at least an emergency pump speed that is safe for the patient.

[0142] In general, all embodiments of the pump 1 have comparably large fluid channels 8 and gaps 9 for the blood flow and thus provide a comparably low resistance against floating thrombi.

[0143] Moreover, the blood pump 1 is designed such that recirculation and stagnation of blood in the pump 1 is avoided. This is for example achieved by opposite inlet and outlet channels 41, 42, 51, 52, well designed flow paths and large gaps 9.

[0144] An ideal hepatic flow distribution is achieved as the pump 1 is designed to discharge the well-mixed blood entering through the first and the second inlet channel 41, 42 to opposite outlet channels 51, 52, preventing degeneration of pulmonary vasculature.

[0145] In FIG. 1 and FIG. 2 an embodiment of the radial pump 1 is shown that comprises an open impeller 2a. The radial blood pump 1 comprises a shaft 10 that extends along the axis of rotation 104 of the impeller 2a. The impeller 2a together with the blades 20 is integrally formed to the shaft 10. The shaft 10 comprises the motor magnets 74 of the first and second motor 71, 72. Thus, the shaft 10 comprises the impeller 2a and the first and second rotor 75, 76.

[0146] Between all rotating components, i.e. the shaft 10 with all its components and an inner housing wall 30 of the radial blood pump 1, a gap size of at least 1 mm is sustained, such that even clots of blood can be pumped by the pump 1. The dimension of the gap 9 also prevents adhesion and formation of blood clots in the pump 1.

[0147] The first and the second motor 71, 72 are cooled by blood flowing through the respective inlet channel 41, 42. The heat dissipated by the motors 71, 72 leads to an increased temperature of the blood. As clot formation depends inter alia on the blood temperature it is advantageous to arrange the first and second motor 71, 72 along different inlet channels 51, 52 in order to avoid a temperature increase beyond a critical clot-formation temperature.

[0148] The shaft 10 of the radial blood pump 1 comprises mechanical bearings 61 at its axial ends. The mechanical bearings 61 can be ball cup bearings consisting of ceramics such as ruby.

[0149] Mechanical bearings 61 are resistant against axial forces and also allow small pump sizes. However, a mechanical bearing 61 generates additional heat and disturbed flow fields which can both lead to blood trauma and clot formation. Materials with excellent tribological properties as well as a high thermal conductivity limit wear to an acceptable extent, thereby minimizing this risk which is further reduced by a well-washed design. Moreover, the mechanical bearings 61 are located in a comparably large distance to the impeller merging portions 22, here the blade channels 21, so that the flow field around the mechanical bearings 61 is much smoother than e.g. in the mechanically supported HeartMate II (Abbott Inc, Chicago, Ill., USA).

[0150] In FIG. 3 a cross-section of an embodiment similar to FIG. 1 and FIG. 2 is shown. However, in contrast to the radial blood pump 1 in FIG. 1 and FIG. 2, the radial blood pump 1 does not comprise mechanical bearings 61, but magnetic bearings 62, keeping the shaft 10 on the central axis 101. Each stator 77, 78 comprises bearing coils 63 and bearing sensors (not shown) that are placed around the axial flow path. Radial position control of the shaft 10 (and thus the first and second rotor 75, 76) is performed using the bearing coils 63 and bearing sensors. Axial positioning of the shaft 10 is achieved by reluctance forces.

[0151] The motor coils 73 and bearing coils 63 are be integrated into one functional unit in this example, of an essentially bearingless motor. The magnetic bearings 62 work contactless and show no mechanical wear.

[0152] FIG. 4 shows a similar design as depicted in FIG. 3, however, with magnetic bearing coils 63 and bearing magnets 64 separate and distinct from the motor coils 73. In this embodiment the radial levitation is achieved passive magnetically (repelling magnets 64). The control coil(s) 63 control the rotors position in a way the axial magnetic forces of the repelling bearing magnets acting on the impeller always equalize the axial thrust forces and the rotor is levitated with a minimum power demand. (Zero force control). The reference sings in all figures refer to functional similar or identical means and are therefore not re-iterated for each figure.

[0153] FIG. 5 to FIG. 9 show radial blood pumps 1 with a closed impeller 2b design. Reference signs from previous figures apply as long as not explicitly mentioned otherwise. Function and specific arrangement of the pump components have been explained above and apply similarly to the closed-impeller designs 2a as long as not indicated otherwise.

[0154] In FIG. 5 a radial blood pump 1 with mechanical bearings 61 is shown.

[0155] FIG. 5 shows a cross-sectional view of the pump 1.

[0156] The impeller 2 is a double-suction closed impeller 2b, wherein the merging portion 22 of the impeller 2b is located in the eyes 23 of the impeller 2b as well as in the blade channels 21. A straight-line flow connection 105 between the first and second inlet channel 41, 42 is located centrally around the axis of rotation 104.

[0157] In the embodiment the first motor 71 is arranged in the first half space S1 and the second motor 72 is arranged in the second half space S2. The motor coils 73 are arranged on the respective first and second stator 77, 78 formed by the housing 3 of the pump 1. The closed impeller 2b has two shrouds 24 covering the blades 20. Blood from the first and second inlet channel 41, 42 flows through the eyes 23 of the impeller 2b and mix at the central region of the impeller 2b, the merging portion 22.

[0158] Motor magnets 74, 75 are comprised by the impeller 2b, particularly by the shrouds 24 of the impeller 2b.

[0159] In contrast to an open impeller the closed impeller 2b is more efficient and allows for almost equal flow around the upper and lower motor region in the secondary flow path even in case of imbalanced inflow/outflow situations. Further, the shroud 24 is beneficial in terms of blood damage compared to an open impeller.

[0160] FIG. 6 shows a schematic cross-section of a radial blood pump 1 with a closed impeller 2b and magnetic bearings 62.

[0161] The magnetic bearings 62 comprise bearing magnets 64, bearing coils 63 and bearing sensors (not shown). In this embodiment the radial levitation is achieved passive magnetically (attractive magnets). The control coil(s) control the rotors position in a way the axial magnetic forces of the attracting bearing magnets acting on the impeller always equalize the axial thrust forces and the the rotor is levitated with a minimum power demand. (Zero force control). The motor magnets 74 of the first and second motor 71, 72 as well as the bearing magnets 64 are placed within the shrouds 24 of the impeller 2b. Axial position control is achieved using the bearing coils 63 and bearing sensors (not shown). Radial positioning is achieved passively.

[0162] FIG. 7 shows an embodiments with magnetic bearings 62 merged with the electric motors 71,72 (axial bearingless motor), wherein the bearings 62 (and thus the motors 71, 72) are arranged such that the axial position of the impeller 2b is actively controllable, while the radial position of the impeller 2b is achieved passively (reluctance forces). The motor magnets 74 and the bearing magnets 64 are merged and formed as a single magnet each.

[0163] FIG. 8 shows an embodiment with magnetic bearings 62 merged with the electric motors 71,72 (axial bearingless motor), wherein the bearings 62 (and thus the motors 71, 72) are arranged such that the radial position of the impeller 2b is actively controllable, while the axial position of the impeller 2b is achieved passively (reluctance forces). The motor magnets 74 and the bearing magnets 64 are merged and formed as a single magnet each.

[0164] In FIG. 9 the flow profile of a blood flow through the operating radial blood pump 1 is shown. The depicted radial blood pump 1 is a blood pump with a closed impeller 2b. The bearings are not shown in this embodiment.

[0165] The arrows indicate the flow velocity in the pump 1 at the location of the arrow. As can be seen, the merging portion 22 in the closed impeller 2b embodiments is in the central region of the impeller 2b at the eyes 23 and at the blade channels 20 of the closed impeller 2b.

[0166] Thus, the merging of the blood flows from the first and second inlet channel 41, 42 takes place before and simultaneously with the blood being transported towards the outlet channels 51, 52. This allows for a pressure equalization between the two inlet channels 41, 42 such that symmetric forces are sustained within the pump 1. Many straight-line connections 105 between the first inlet channel 41 and the second inlet channel 42 exist and are exemplary indicated with dotted lines. The straight-line connections 105 allow for an instant pressure equalization between the inlet channels 41, 42.

[0167] FIG. 10 shows a part of the system according to the invention. The radial blood pump 1 is connected to the respective blood vessels 200, 201, 202, 203 of the heart 205 and support the Fontan circulation of the heart 205. With the first inlet channel 41 the pump 1 is connected to the SVC 200, with the second inlet channel the pump is connected to the IVC 201 via a graft 206, with the first outlet channel 51 the pump 1 connected to the left pulmonary artery 202 and with the second outlet channel 52, the pump is connected to the right pulmonary artery 203

[0168] Additionally, a differential pressure sensor 11 is arranged between the atrium of the heart 205 and one of the inlet channels 41, 42, here the second inlet channel 42 of the radial blood pump 1.

[0169] The data from the pressure sensor 11 is then used for adjusting the pump rate of the pump 1.

[0170] This is shown in FIG. 11. The estimated differential pressure 300 is compared 400 to a desired differential pressure 301. A signal coding the deviation 402 between the desired and estimated differential pressure 300, 301 is provided to a controller 302 of the system. The controller 302 adjusts 401 the pump speed accordingly such that the deviation 402 between the desired pressure 301 and estimated pressure 300 is minimized. The pressure sensor data 403 are processed prior to the comparison with a processor 303 in order to provide an appropriate response. This way the blood flow 200 in the cardiovascular system 500 can be controlled in a robust and fail-safe manner.

[0171] The invention provides a blood pump 1, particularly a Fontan pump with reduced space requirements and robust and fail-safe operation.

REFERENCES

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