Blood pump system

Abstract

To further improve a known blood pump system in terms of arrangement of a pressure sensor.SOLUTION: A blood pump system includes a blood pump 50 and an intravascular flow cannula 53. Within the flow cannula, a pressure sensor 30 is arranged at a level (A) of a blood flow through-opening 54 with respect to the flow cannula's longitudinal axis 1, in the intravascular flow cannula, or borders the level (A) of the blood flow through-opening 54. This arrangement allows the pressure sensor 30 to be used to extremely accurately and safely detect both a pressure outside the flow cannula 53 and a fact of whether a vascular wall is being sucked against the blood flow through-opening 54.SELECTED DRAWING: Figure 2D

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE The present invention relates to a blood pump system that includes a blood pump and an intravascular flow cannula in flow communication with the blood pump for directing blood from a blood vessel to the blood pump. [Background technology]

[0002] More specifically, the blood pump is an intravascular rotary blood pump, which may be placed inside a blood vessel, such as the left or right ventricle or the aorta or any other blood vessel, as the case may be. The blood pump is driven by a motor, which may be outside the patient's body or may be placed inside the blood vessel together with the pump. In the former case, the pump is connected to an external motor by a flexible drive cable, while in the latter case, the pump and the motor are combined to form an integral pump device, which receives energy from outside the patient's body, preferably through a catheter. The latter configuration is the preferred configuration for the blood pump system of the present invention, but the invention is not limited thereto.

[0003] When such blood pump systems are used for temporary cardiac support, they are introduced percutaneously, for example into the femoral artery, and guided through the body's vascular system to, for example, support or replace the pumping action of the heart. During the operation, the flow cannula protrudes through the heart valve opening, allowing blood to be pumped through the heart valve by the pump. Furthermore, the blood pump system is equipped with pressure sensors on the outside of the blood pump housing and on the outside of the flow cannula to establish inlet and outlet pressures. The data on the inlet and outlet pressures, together with the power consumption of the electric motor of the blood pump system, form a set of relevant information about the function and delivery rate of the blood pump system. Furthermore, the measured pressures allow inferences to be drawn regarding the positioning of the blood pump in the vascular system. Furthermore, a comparison of the current power consumption of the motor with the differential pressure allows the local conditions as well as cavitation and aspiration to be ascertained.

[0004] The patent application JP 2003-233666 proposes to provide a blood pump system with two or more pressure sensors. For example, pressure sensors can be provided outside the blood pump system at the proximal end of the blood pump and / or at the distal end of the flow cannula. An additional pressure sensor can be provided inside the flow cannula to determine when the flow cannula is aspirated against the heart chamber wall. In addition to the pressure sensor inside the flow cannula, the patent application JP 2003-2336666 emphasizes that it is also important to have a pressure sensor outside the flow cannula, close to the blood flow through the opening, to measure the physiological blood pressure there, and in particular addresses the preferential placement of an external pressure sensor on the flow cannula to measure the physiological pressure in the patient's ventricle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 160407 Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of the present invention to further improve the known blood pump system in terms of the arrangement of the pressure sensor. [Means for solving the problem]

[0007] The blood pump system of the present invention therefore comprises a blood pump and an intravascular flow cannula in flow communication with the blood pump, with a pressure sensor located inside the flow cannula at a distal end portion of the flow cannula in the region of a blood flow through opening or bordering the region of the blood flow through opening, the distal end portion of the flow cannula being the end portion further away or distal from the blood pump, the blood flow through opening at the distal end of the flow cannula serving the purpose of blood entering the flow cannula on its way to the pump or exiting the flow cannula if the pump is driven in the reverse direction.

[0008] It is important that the pressure sensor be located inside the flow cannula. In this way, the pressure sensor cannot be covered or in any other way obstructed by the heart chamber wall when the flow cannula is aspirated against the heart chamber wall or when the flow cannula is otherwise moved. Thus, an indication by the pressure sensor that the pressure is near zero or that the rhythmic pressure difference of the heartbeat is rapidly decreasing is a clear signal that the flow cannula is aspirated against, for example, the heart chamber wall. In other words, a pressure sensor located inside the flow cannula can be used to specifically serve as a wall suction indicator.

[0009] However, due to its specific arrangement in or bordering the area of ​​the blood flow through opening of the flow cannula, the blood pressure in the area of ​​the blood flow through opening substantially coincides with the blood pressure outside the flow cannula, so that in some cases the same pressure sensor can be used to serve a second purpose, i.e. to measure or at least approximately measure the pressure outside the flow cannula, such as the pressure inside the left or right ventricle of the heart. The proposed special location of the pressure sensor therefore makes it possible to dispense with a separate external pressure sensor outside the flow cannula. In particular, according to a preferred embodiment of the invention, the blood pump system can be configured to determine the pressure difference between a first pressure value provided by a pressure sensor arranged inside the distal end portion of the flow cannula and a second pressure value provided by a second pressure sensor arranged outside the blood pump, for example on the blood pump housing.

[0010] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram of a blood pump system including a blood pump and a flow cannula placed through the aorta and extending through the aortic valve into the left ventricle (16). [Figure 2A] FIG. 13 shows an option for placing a pressure sensor inside the flow cannula. [Figure 2B] FIG. 13 shows an option for placing a pressure sensor inside the flow cannula. [Figure 2C] FIG. 13 shows an option for placing a pressure sensor inside the flow cannula. [Figure 2D] FIG. 13 shows an option for placing a pressure sensor inside the flow cannula. [Figure 3a] 13A-13D are diagrams of variations of the frame structure defining the inflow cage of the flow cannula. [Figure 3b] 13A-13D are diagrams of variations of the frame structure defining the inflow cage of the flow cannula. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] FIG. 1 shows a blood pump system with a catheter 10, which in this embodiment is introduced retrogradely into the descending aorta 11. The descending aorta 11 is a part of the aorta 12, which first ascends and then descends from the heart and has an aortic arch 14. At the beginning of the aorta 12, an aortic valve 15 is located, which connects the left ventricle 16 to the aorta 12, up to which the intravascular blood pump system extends. In addition to the catheter 10, the blood pump system includes a rotary pump 50, which is fastened to the distal end of the catheter hose 20 and has a motor section 51 and a pump section 52 arranged at an axial distance from the motor section 51, as well as a flow cannula 53 protruding distally from the inflow end of the pump section 52. The flow cannula 53 has a blood flow through opening 54 at its distal end part EP, which forms a suction inlet or, if the pump 50 is driven in the retrograde direction, a blood flow outlet. Distal to the through opening 54 is provided a soft flexible tip 55, which may be configured, for example, as a "pigtail" or in a J-shape. Through the catheter hose 20 extend various wires and devices that are important for operating the pump device 50. Of these, FIG. 1 only shows two optical fibers 28A, 28B, the proximal ends of which are attached to the evaluation device 100. These optical fibers 28A, 28B are each part of an optical pressure sensor, the sensor heads 30 and 60 of which are located on the one hand outside the housing of the pump section 52 and on the other hand inside the distal end part EP of the flow cannula 53. The pressure transmitted by the sensor heads 30 and 60 is converted into an electrical signal in the evaluation device 100 and displayed, for example, on a display screen 101.

[0013] As already mentioned, the present invention is not limited to rotary pumps with integral motor section 51. Alternatively, the motor for driving the pump may be provided external to the patient, and a flexible drive cable may connect the pump to an external motor.

[0014] Both the measurement of the aortic pressure by the sensor head 60 and the measurement of the ventricular pressure by the sensor head 30 allow the establishment of an actual pressure signal as well as a measurement of the contractility, by which the restitution of the heart is measured, as well as a pressure difference, which is used to calculate the flow of the pump device 50. The principles of electro-optical pressure measurement and the construction and arrangement of optical fibers are explained in more detail in US Pat. No. 5,399,363, the disclosure of each of which is incorporated herein by reference. The present invention differs from this disclosure only in that the pressure sensor 30 is placed at a specific position inside the flow cannula 53, as will be explained below, rather than on the outer surface of the flow cannula.

[0015] FIG. 2A shows the distal end portion EP of the flow cannula 53 in more detail according to a preferred embodiment. The end portion EP includes, relative to its approximate longitudinal axis 1, a radial blood flow through opening 54 for blood to enter or, in some cases, exit the flow cannula 53. In the region of the blood flow through opening 54, a frame structure including a number of struts 58 is provided to form a cage that serves two purposes. First, the struts 58 connect the flow conducting part of the flow cannula 53 with the soft flexible tip 55. Second, the frame structure forming the cage prevents the heart chamber wall from being sucked into the flow cannula 53 and obstructing it. Thus, although the struts 58 may extend generally axially, they may extend helically in the same way, cross each other and / or have interconnections. As shown in FIG. 2B, the struts 58 divide the blood flow through opening 54 into separate blood flow openings 54A-54D. The dashed lines in the region of the blood flow through openings 54A and 54D indicate the outer limit of the flow cannula 53 in the region A of the blood flow inlet 54.

[0016] FIG. 2C is a cross-sectional view through the end portion EP. The area A enclosed by a dashed line indicates the height of the blood flow through opening 54 or the blood flow through openings 54A-54D, respectively, relative to the longitudinal axis 1 of the flow cannula. This is the area in which the pressure sensor 30 can be located inside the flow cannula. For example, the pressure sensor can be illustrated by a pressure sensor 30', which is placed at position X as shown in FIG. 2C and is only diagrammatically shown. In any case, the pressure-sensitive surface 32 of the pressure sensor 30' must be oriented perpendicular to the longitudinal axis 1 for reasons that will be explained in more detail in WO 2013 / 160407 A1, i.e. so that high-frequency physiological signals of up to 250 Hz can be obtained from the signal data with increased measurement accuracy.

[0017] This allows the area height A to be bounded, rather than placing the pressure sensor 30 somewhere in the area A of the blood flow through opening 54. Preferably, the pressure sensor is located at its proximal boundary, as illustrated in FIG. 2C by the pressure sensors 30″ and 30′″. Again, the pressure sensors 30″ and 30′″ located at positions Y and Z are only shown diagrammatically, their pressure sensitive surfaces 32 being oriented perpendicular to the longitudinal axis 1 in the same way. That is, the blood flow through opening 54 or at least one of the blood flow through openings 54A-54D each has a boundary line surrounding the through opening 54 or 54A-54D, respectively, said boundary line having a proximal portion, which in the embodiment shown in FIG. 2 is formed by an end face 57 of a funnel structure 56, which forms part of the flow cannula 53. The funnel structure may be formed from a thin film, in particular a thin polymer film. It is preferred to position the pressure sensor 30, preferably with its pressure sensitive surface, precisely at the height of the proximal portion 57 of the boundary line surrounding the through opening 54 or through openings 54A-54D, as shown in FIG. 2C by pressure sensors 30″ and 30′″. This allows the overall pressure inside the ventricular cavity to be sensed during normal pump operation with minimal or no interference with the pump flow rate. Furthermore, if suction is present, the sensor at this preferred location can also detect negative pressure due to suction, which is a local phenomenon at the inlet. More preferably, the pressure sensor is positioned, preferably fixed, to the frame structure, for example to the strut 58. The location can be tangential from the strut 58 as shown by pressure sensor 30″ in FIG. 2C, or more preferably radially inward of the frame structure as shown by pressure sensor 30′″ in FIG. 2C.

[0018] FIG. 2D shows a concrete example of how the pressure sensor 30 can be placed inside the flow cannula 53, corresponding to the position Z of the pressure sensor 30''' in FIG. 2C. Thus, the pressure-sensitive surface 32 of the pressure sensor 30 is bounded at the height of the blood flow through-opening 54, precisely at the proximal portion 57 of the boundary line surrounding the through-opening 54, which is defined by the end face of the funnel structure 56 surrounding the frame structure of the end portion EP. As can be seen in the figure, the optical fiber 28A, or multiple fibers, are protected inside a separate lumen 27, inside which the fibers can move freely. The lumen 27 may be made of a polymer, in particular polyurethane, or preferably Nitinol or another shape memory alloy, and is placed along the exterior of the flexible flow cannula 53. Lumen 27 passes through a funnel structure 56 into flow cannula 53 , and the distal end of optical fiber 28 A carrying pressure sensor 30 is secured radially inward of struts 58 .

[0019] Although the invention has been described with respect to end portion EP having an enlarged cross section relative to the remainder of flow cannula 53, the invention is not limited in this respect. However, an enlarged cross section, particularly a funnel-shaped structure 56 that funnels from distal to proximal, is advantageous because the pressure drop of blood flow along the axis 1 of the flow cannula is less rapid inside the funnel shape than the pressure drop inside the non-funnel-shaped remainder of the flow cannula 53. Thus, precise placement of pressure sensor 30 at the proximal portion 57 of the boundary line surrounding the through opening is less critical with a funnel-shaped flow cannula, and misplacing pressure sensor 30 by a minimum axial distance inside flow cannula 53 has less impact compared to a non-funnel-shaped structure. At least the struts 58 of the frame structure are made from a shape memory alloy, such as Nitinol, or a shape memory polymer, and the funnel structure 56 surrounding the frame structure is made from a flexible material such that upon insertion of the flow cannula 53 through the patient's vascular system, the frame structure, together with the funnel structure 56, has substantially the same diameter as the remainder of the flow cannula 53. The expanded configuration, having an enlarged cross section, is assumed after deployment of the device when the frame structure reaches body temperature.

[0020] 3a and 3b show alternative variations of the expandable frame structure defining the inflow cage. In FIG. 3a, interconnecting struts 58 are provided between the main struts to provide a structure that further divides the inlet / outlet openings 54A-54D into smaller openings 54A'-54A'''. This prevents ingestion of highly flexible structures such as the valve (mitral valve: leaflets, cordae, papilla structures) organs. Here, the preferred sensor location, indicated by ZZ in FIG. 3a, is radially inward of the interconnecting strut assembly 58' at the junction of the interconnecting struts 58' with the end face 57 of the funnel structure 56, e.g., the edge of a thin polymer film.

[0021] In FIG. 3b, the same interconnecting strut assembly 58′ is present, in addition to being similarly provided, e.g., mirrored (58”), on the side of the flexible funnel structure 56. This prevents local inward bending of the funnel structure 56, which may otherwise occur during normal flow conditions due to local pressure drops when flow enters the inlet, or during a suction event, when negative pressure may exist. The inflow end surface 57 of the funnel structure 56 may be further structurally improved by locally increasing the thickness of the funnel structure. A radially stiffer funnel structure 56 is particularly advantageous for releasing from the cardiac structure after a suction event.

Claims

1. 1. A blood pump system comprising: a blood pump (50); and an intravascular flow cannula (53) in flow communication with said blood pump, said intravascular flow cannula (53) having an approximate longitudinal axis (1), and a distal end portion (EP) distal from said blood pump and a proximal end portion proximal to said blood pump, said flow cannula (53) having at least one blood flow through opening (54; 54A-54D) at its distal end portion (EP) for allowing blood to enter or leave said flow cannula, and a pressure sensor (30; 30'; 30", 30'") arranged inside said flow cannula, characterized in that said pressure sensor is arranged at a height (A) of said at least one blood flow through opening relative to the longitudinal axis (1) of the flow cannula or bounds said height (A) of said at least one blood flow through opening.

2. 2. The blood pump system according to claim 1, characterized in that each of the at least one blood flow through-openings has a boundary line surrounding the through-opening, the boundary line having a proximal portion (57), and the pressure sensor (30; 30', 30"; 30'") is arranged at the height of the proximal portion (57) of the boundary line relative to the longitudinal axis (1) of the flow cannula.

3. 3. The blood pump system of claim 2, wherein the pressure sensor (30; 30'; 30"; 30'") bounds the proximal portion (57) of the boundary line.

4. 4. The blood pump system according to claim 1, characterized in that a frame structure (58) is provided in the region of the blood flow through openings (54; 54A-54D) and the pressure sensor (30; 30'; 30"; 30'") is arranged on the frame structure (58).

5. 5. The blood pump system according to claim 4, characterized in that the pressure sensor (30) is arranged radially inward of the frame structure (58) with respect to the longitudinal axis (1) of the flow cannula.

6. 6. A blood pump system according to claim 1, characterized in that the flow cannula (53) has, at its distal end portion (EP), a section with an enlarged cross section, and in that the at least one blood flow through opening (54; 54A-54D) is arranged in the section with the enlarged cross section.

7. 7. The blood pump system of claim 6, wherein the section with the enlarged cross section includes a funnel structure (56) that is funnel-shaped from distal to proximal, and the pressure sensor (30) is disposed at a distal end of the funnel structure.

8. 8. The blood pump system according to claim 1, further comprising a pressure sensor (60) arranged outside the blood pump (50), characterized in that the blood pump system is configured to determine a differential pressure from a first pressure value provided by the pressure sensor (30; 30'; 30"; 30'") arranged inside the flow cannula (53) and a second pressure value provided by the pressure sensor (60) arranged outside the blood pump (50).

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