Blood pump

Abstract

It is an object of the present invention to provide an improved control method and a correspondingly improved control device for an intravascular blood pump.SOLUTION: The invention relates to a control device 100 for controlling the blood flow of an intravascular blood pump 50, wherein the blood pump 50 comprises a pump unit 52 comprising a drive unit 51 for driving the pump unit 52 and is configured to convey blood from a blood flow inlet 54 towards a blood flow outlet 56, wherein the control device 100 is configured to operate the blood pump 50 in a selectable zero flow control mode, wherein a blood flow command signal is selected, and wherein the control device 100 comprises a first controller 401 and a second controller 402, A first controller 401 is configured to control the blood flow by adjusting the speed command signal to the drive unit 51, and a second controller 402 is configured to control the drive speed of the drive unit 51.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to vascular pumps, particularly intravascular blood pumps for percutaneous insertion into a patient's blood vessels. In particular, the present invention relates to a unique control method for a percutaneously insertable blood pump, a corresponding control device, and a system comprising the control device and the blood pump. The present invention is configured for and is particularly useful for intravascular blood pumps, but is less relevant to larger blood pumps such as VADs that are not located within a blood vessel or the heart but are located outside the patient's heart, for example, implanted in the thoracic cavity. [Background technology]

[0002] Ventricular assist devices (VADs) are used to support the function of a patient's heart, either as left ventricular assist devices (LVADs) or right ventricular assist devices (RVADs). A typical VAD is connected to the patient's heart by an appropriate conduit and implanted outside the heart in the patient's chest cavity. An intravascular blood pump for percutaneous insertion typically includes a catheter and a pump unit, which are inserted into a blood vessel through an access pathway, for example, through the aorta into the left ventricle, and then into the patient's heart. The pump unit may be located at the distal end of the catheter and may include a blood inlet and a blood outlet, and the catheter, and blood flow through the catheter is generated, for example, by a rotor or impeller of the pump unit. For example, a cannula may extend through the aortic valve, with the blood inlet located at the distal end of the cannula in the left ventricle and the blood outlet located at the proximal end of the cannula in the aorta. By creating blood flow, the pressure difference between the outlet and inlet is overcome.

[0003] An important aspect of intravascular blood pumps (hereinafter also referred to simply as "blood pumps") is, among other things, their removal from the patient, thus ensuring that native heart function has recovered. This can be done, for example, by sufficiently reducing the degree of assistance provided by the blood pump, so that the blood pump can ultimately be removed after the heart is determined to have sufficiently recovered. This aspect, i.e., determining the exact timing for removal, is less important with larger VADs, which are typically implanted within the patient's thoracic cavity and designed for long-term use.

[0004] To date, no physical signal is known to adequately indicate the state of cardiac recovery as long as an intravascular blood pump is implanted. The blood pump assists the heart, but it is impossible to know unassisted cardiac function. Furthermore, when the blood pump is turned off, backflow occurs through the cannula, making it impossible to know unassisted cardiac function. Backflow is a major problem with intravascular blood pumps because the blood pump, or more specifically, the pump's cannula, extends through a heart valve, such as the aortic valve, creating an open pathway through the heart valve and allowing blood to flow back into the heart when the blood pump is not operating. Such outflow does not typically occur with extravascular devices because they do not extend through but bypass the heart valve, such as a VAD placed outside the heart in the thoracic cavity.

[0005] In the current state of the art, the current pump speed setting is manually reduced stepwise by a physician, for example, one level at a time, based on expert experience. After the pump speed is reduced, the mean aortic pressure is monitored. Some facilities perform ultrasound-based left ventricular volume assessment and continuous cardiac output measurement. If the mean aortic pressure remains stable, the heart is deemed capable of taking over from the blood pump. However, if the mean aortic pressure decreases, it is deemed that the heart still requires further assistance and therefore that the pump speed needs to be increased again. Furthermore, before the blood pump is removed, a so-called on / off technique is applied. In this way, the pump speed is significantly reduced, for example, over several hours, during which the patient's physiological state and ventricular dilation are particularly observed, for example, based on echocardiography (ECHO) measurements and / or ventriculography. ECHO can provide information about the heart, such as its size and shape, for example, quantifying the internal ventricular size and pumping capacity, allowing for the calculation of cardiac output, ejection fraction, and diastolic function. Ventriculography involves injecting a filler into the ventricles of the heart to measure the amount of blood being pumped. Measurements achieved by ventriculography are ejection fraction, stroke volume, and cardiac output.

[0006] If the blood pump is turned off and the heart is still functioning poorly, the unassisted ventricle will expand significantly, resulting in an insufficient volume of blood being ejected from the ventricle during systole, thereby increasing the left ventricular end-diastolic volume and end-diastolic pressure. In other words, the reduced pumping speed will stress the heart, which can be equivalent to suddenly overloading a heart that has not yet recovered. This can set back treatment by several days.

[0007] Therefore, the practical monitoring process before removal of the blood pump becomes more or less a trial-and-error procedure, where the pump speed is further reduced if the patient's condition remains stable, and if the patient's condition worsens, the pump speed needs to be increased again. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide an improved control method and a corresponding improved control device for an intravascular blood pump, as well as a system comprising this control device and an intravascular blood pump, in which the vascular pump is operated in a manner that ensures a better assessment of the state of cardiac recovery. [Means for solving the problem]

[0009] This object is achieved by the features of the respective independent claims. Advantageous embodiments and further developments are defined in the respective dependent claims.

[0010] For the sake of clarity, the following definitions apply herein: The term "cardiac characteristic parameter" is to be understood as a specific value obtained from a physiological signal that can characterize the state of the heart, for example, in relation to load, such as overload or no load, and / or in relation to physiological conditions, such as weakness, health, or recovery.

[0011] The "human circulatory system" is the organ system that allows blood to circulate. The essential components of the human circulatory system are the heart, blood, and blood vessels. The circulatory system includes the pulmonary circulation, which is a "loop" through the lungs, where blood is oxygenated; and the systemic circulation, which is a "loop" through the rest of the body to provide oxygen-rich blood.

[0012] The improvements disclosed herein relate to blood pumps having settable blood flow levels. For example, in the case of rotary blood pumps, the "settable blood flow level" may be a discrete or continuously settable blood flow level within a range defined by a minimum blood flow and a maximum blood flow.

[0013] The basic idea of ​​the control device and corresponding control method for controlling an intravascular blood pump proposed herein is to realize a mode in which the current blood flow through the blood pump can be kept very low compared to its blood flow output capacity, and preferably at zero. Preferably, the blood flow through the blood pump is maintained between 0 L / min and 1 L / min, more preferably between 0 L / min and 0.5 L / min, 0 L / min and 0.2 L / min, or even between 0 L / min and 0.1 L / min. Most preferably, the blood flow through the blood pump is maintained at approximately zero flow. In this case, the blood pump is controlled to produce neither positive nor negative blood flow. This operating mode is referred to herein as the "zero flow control mode." For example, zero flow rate can be established and / or maintained by controlling a drive unit, such as a motor, of the blood pump, and specifically by controlling the current drive speed of the drive unit, such as a motor, and thus the flow rate, so that only the current pressure difference between the blood inlet and blood outlet of the blood pump is compensated for.

[0014] "Zero flow" in this context should be understood as zero flow or very low blood flow. Since the purpose of the zero flow control mode is to obtain information about the state of cardiac recovery, implementing a very low blood flow may be sufficient. In this context, a low blood flow, such as up to 0.1 L / min, up to 0.2 L / min, or even up to 0.5 L / min, shall be considered as "zero flow". In any case, "zero flow" shall not be negative. In other words, zero flow shall not allow any backflow through the blood pump.

[0015] An intravascular blood pump for percutaneous insertion in the present context comprises a catheter and a pump unit, which is inserted into a patient's heart via a blood vessel, for example, through the aorta into the left ventricle. The pump unit comprises a blood inlet and a blood outlet, and a cannula, through which blood flow is generated by a drive unit for driving the pump unit. For example, the pump unit may comprise a rotor or impeller, e.g., a motor, driven by the drive unit, thereby transporting blood from the blood inlet to the blood outlet. For example, the cannula may extend through the aortic valve, with the blood inlet located at the distal end of the cannula in the left ventricle and the blood outlet located at the proximal end of the cannula in the aorta. The intravascular blood pump can have a maximum outer diameter within the range of about 12 French (F) (about 4 mm) to about 21 French (F) (about 7 mm), for example, 12F (about 4 mm), 18F (about 6 mm), or 21F (about 7 mm), which is usually the maximum outer diameter of the pump unit. The catheter can have an outer diameter that is less than the outer diameter of the pump unit, for example, 9F (about 3 mm).

[0016] Natural heart function creates a pressure difference between, for example, the aorta and the left ventricle. To create positive blood flow, the blood pump must overcome this pressure difference. If this is not the case, i.e., if the pressure created by the blood pump is too low, the existing pressure difference between the aorta and the left ventricle will cause backflow into the left ventricle.

[0017] By applying the zero flow control mode, the blood pump does not or only very slightly assists the heart, thereby advantageously avoiding backflow, i.e., the blood pump does not allow blood to flow backward, e.g., in the case of left ventricular assistance, during diastole, the blood pump does not allow blood to flow backward, such as from the aorta back into the left ventricle.

[0018] By applying the zero flow control mode, the drive unit, e.g., rotor or impeller, of the blood pump will still spin, thus reducing the risk of clot formation due to continuously moving parts.

[0019] The zero flow mode of operation ensures that the assist provided by the blood pump to the heart is essentially zero. "Essentially zero" means that any blood flow produced continuously must be at least negligible and in any event non-negative, meaning that the blood pump does not allow backflow through the blood pump.

[0020] In the zero-flow mode of operation, the entire work in overcoming the pressure difference between the pressure in the assisted ventricle, e.g., the left ventricle, and the pressure in the adjacent vessel, e.g., the aorta, is provided solely by the heart. In this manner, the zero-flow mode of operation allows for monitoring one or more suitable characteristic parameters of the heart that can be used or interpreted as indicators for the state of cardiac recovery.

[0021] Preferably, the blood flow of the blood pump is related to the drive speed of a drive unit, e.g., a motor, the current supplied to the drive unit, and / or the pressure difference between the outlet and inlet of the blood pump. This association may be stored in a memory, e.g., in a look-up table, as will be explained in more detail below. That is, the command signal values ​​may be stored in a memory of the control device or in a memory within the blood pump that is accessible by the control device.

[0022] The first aspect is a blood flow Q of an intravascular blood pump for percutaneous insertion into a patient's blood vessel. pump (t) is a blood pump comprising a pump unit and a drive unit for driving the pump unit, the drive unit being configured to convey blood from a blood flow inlet toward a blood flow outlet. The control device is configured to operate the blood pump in a selectable zero flow control mode, in which a blood flow command signal Q pumpset (t) is selected. The control device comprises a first controller and a second controller, wherein the first controller generates a speed command signal n pump set (t) by adjusting the blood flow Q pump (t), and the second control device controls the drive speed n pump (t). More specifically, the control device is specifically configured to control an intravascular blood pump, or more generally, to control a low inertia device, as will be described in more detail below.

[0023] Preferably, the intravascular blood pump comprises a cannula between the blood inlet and the blood outlet, through which blood flow is generated by the pump unit. In operation, the cannula can extend, for example, through the aortic valve, while the blood inlet is located in the left ventricle and the blood outlet is located in the aorta.

[0024] For example, the controlled blood flow can be constant. By compensating for the most recent pressure difference between the blood inlet and the blood outlet, the actual blood flow through the blood pump is zero flow. That is, in the zero flow control mode, the influence of the most recent pressure difference between the blood outlet and the blood inlet is counteracted by controlling the blood flow via controlling the drive speed.

[0025] Preferably, the first controller controls the blood flow command signal Q pump set (t) and blood flow Q pump (t) based on the difference ΔQ between the speed command signal n pump set In other words, the first controller is configured to determine the velocity command signal n pump set The actual blood flow Q (t) is determined pump (t) is the blood flow command signal Q pump set It is configured to be compared with (t).

[0026] Preferably, the second control device controls the drive current I supplied to the drive unit. pump (t) by adjusting the driving speed n pump (t). For example, the drive unit may comprise a motor, and in particular an electric motor, and the drive current to be adjusted may be the motor current supplied to the motor. Thus, in the case of a rotary drive unit, the drive unit command speed signal n pump set (t) and set drive speed n pump set (t) may be the rotational speed. The motor may be located within the pump unit and is directly or indirectly coupled to the impeller, for example by a mechanical or magnetic connection.

[0027] Preferably, the first controller and the second controller are part of a cascade control system, where the first controller is an outer controller and the second controller is an inner controller. The outer controller may be embedded in the outer control loop and may manage the blood flow generated by the blood pump by comparing the blood flow command signal with the generated blood flow and by setting the set point of the inner control loop, i.e., the speed command signal of the blood pump. The inner controller is part of the inner control loop and may control the speed of the blood pump by adjusting the motor current accordingly.

[0028] Preferably, the control device controls the blood flow Q over a predetermined zero flow control time. pump (t) is configured to control the

[0029] For example, the predetermined zero-flow control time can be set to last for a portion of one cardiac cycle of the assisted heart. That is, the zero-flow control mode is simply applied for a short period of time "within a beat." In this case, the predetermined zero-flow time is preferably short compared to the duration of a cardiac cycle. In this way, information about the recovery state of the heart can be gathered without overloading the heart in any way, because the duration of time the heart is unassisted is kept to a minimum.

[0030] For example, the predetermined zero flow control time may be set to last for at least one complete cardiac cycle or for a predetermined number of complete consecutive cardiac cycles.

[0031] Preferably, the control device is configured to synchronize the zero flow control time with the occurrence of at least one characteristic cardiac cycle event. For example, the start and / or end of the zero flow control time is synchronized with the occurrence of at least one characteristic cardiac cycle event. In particular, the start and end of the zero flow control time may be synchronized with the occurrence of two characteristic cardiac cycle events. In this way, the zero flow control mode may be set to match a time interval of the cardiac cycle, where certain characteristic cardiac parameters can provide particularly useful information that directly or indirectly indicates the state of cardiac recovery.

[0032] For example, the characteristic cardiac cycle event may be an aortic valve opening or aortic valve closing. For example, the control device may be configured to detect the aortic valve opening by one of the following: the presence of equilibrium in left ventricular or aortic pressure, the occurrence of an R wave in an electrocardiogram, an ECG, or a signal sent from a patient with an assisted heart.

[0033] Additionally, the characteristic cardiac cycle event may be the opening of the mitral valve, the closing of the mitral valve, or the development of end-diastolic left ventricular pressure.

[0034] Preferably, the control device is configured to monitor the value of one or more characteristic cardiac parameters, i.e., the control device may be configured to monitor the value of one or more characteristic cardiac parameters in the zero flow control mode each time the zero flow control mode is applied.

[0035] Preferably, the control device is configured to operate the intravascular blood pump in the zero-flow control mode periodically or irregularly, the periodic or irregular application of the zero-flow control mode being carried out over a predetermined period of time, for example, from a portion of one cardiac cycle up to several days.

[0036] Preferably, the control device is configured to identify a trend in the value of one or more of the monitored characteristic cardiac parameters. The trend in the one or more monitored characteristic cardiac parameters can be used as an indicator for the state of cardiac recovery or for the condition of cardiac recovery, i.e., whether or not recovery is progressing, and assistance can be provided. The trend can be presented to a physician via a user interface of the control device, thereby enabling the physician to make a decision regarding the state of cardiac recovery.

[0037] For example, at least one characteristic parameter of the heart may be the arterial blood pressure, which is measured each time the zero-flow operating mode is established. Applying the zero-flow control mode may cause the arterial blood pressure to drop. A pressure drop reaching a critical value or showing a critical drop indicates that the heart is not recovering and therefore the blood pump cannot be removed. In another example, in the zero-flow control mode, the arterial blood pressure may remain stable, i.e., showing only a small pressure drop. In such a case, it may be considered that the heart has sufficiently recovered and the blood pump can be removed.

[0038] Preferably, the at least one characteristic cardiac parameter is: arterial pressure pulsatility AOP| max -AOP| min , mean arterial pressure, cardiac contractility dLVP(t) / dt| max, cardiac relaxation dLVP(t) / dt| min , and heart rate HR.

[0039] The control device measures the blood flow Q pump (t) or blood flow Q pump The blood pump may be configured to calculate or estimate (t). For example, the pressure difference between the blood flow outlet and the blood flow inlet may be determined by respective pressure sensors located at the inlet and outlet of the blood pump, i.e., a pressure sensor capturing the subsequent load of the blood pump and a pressure sensor capturing the preload of the blood pump. Alternatively or additionally, the blood pump may include one sensor configured to measure the pressure difference only in a direct manner. Furthermore, in alternatives, the pressure difference between the blood flow outlet and the blood flow inlet may be estimated, measured, or calculated.

[0040] Blood flow Q pump Rather than measuring (t), a lookup table is used to calculate the blood flow Q pump (t) can be determined, and the look-up table can represent the relationship between blood flow, drive speed, and at least one of the pressure difference between the blood flow outlet and the blood flow inlet and the drive current supplied to the drive unit. Such a look-up table can include a set of characteristic curves representing each relationship, for example, a set of curves each corresponding to a particular pump speed. It will be appreciated that other suitable look-up tables can be used and that the values ​​in the look-up table can be given in a variety of units.

[0041] Data for use in look-up tables, such as motor current and blood flow, can be recorded on a test bench assembly by running a blood pump through fluid at a given motor speed and at a predetermined pump load (pressure difference between the inlet and outlet) while recording the flow produced by the pump. For example, the pump load can be increased over time from zero load (no pressure difference between the blood inlet and outlet, i.e., maximum flow rate) to maximum load (pump not functioning, i.e., no flow) while the motor current and blood flow are recorded. Such look-up tables can be created for multiple different motor speeds. Blood flow Q pump By using such a look-up table to determine (t), the blood flow Q pump Compared to techniques that measure or calculate the blood flow Q during blood pump operation, pump A more advantageous approach for determining the blood flow Q(t) can be realized by using a look-up table, based solely on readily available operating parameters of the blood pump. pump (t) is determined. Therefore, no sensors are required to detect patient parameters, such as pressure or flow sensors to detect pressure differences inside the patient's vessels. Furthermore, the blood flow Q can be determined from a look-up table. pump Reading the value for (t) does not require computer-intensive calculations.

[0042] However, monitoring one or more appropriate characteristic cardiac parameters by only applying the single-beat zero-flow control mode may not adequately adapt the heart to the inadequate assistance of the blood pump. Thus, the monitored characteristic cardiac parameters may still not adequately represent the true state of cardiac recovery, e.g., may not adequately represent the actual pumping capacity of the heart. Therefore, the single-beat zero-flow control mode may be repeated for multiple consecutive cardiac cycles.

[0043] Therefore, the predetermined zero-flow time can be set to last for at least one complete cardiac cycle or a predetermined number of complete consecutive cardiac cycles. For example, the predetermined zero-flow time can be set to be a portion of one cardiac cycle for up to several hours. In this way, the heart can be fully adapted to a state without blood pump assistance, so that the actual state of cardiac recovery can be better ascertained.

[0044] It is also possible to combine zero flow for one heartbeat with zero flow over a complete cardiac cycle. For example, the zero flow control mode can be applied initially for a relatively short period of time, such as for a portion of one cardiac cycle, or for 1 to 300 consecutive cardiac cycles. After native cardiac function and sufficient recovery have been established, the zero flow control mode can be applied for an extended period of time, such as for several minutes or hours, or even for multiple complete cardiac cycles, up to several days.

[0045] A second aspect provides a system comprising an intravascular blood pump for cardiac assistance and a control device according to the first aspect.

[0046] Preferably, the blood pump is catheter-based, that is to say, the blood pump preferably comprises a catheter and a pump unit, the pump unit preferably being located at the distal end of the catheter.

[0047] Preferably, the blood pump may be implemented as a rotary blood pump, i.e. as a blood pump driven by a rotary motor.

[0048] The blood pump may be catheter-based for percutaneous implantation or placement directly into the heart through a corresponding blood vessel. For example, the blood pump may be a blood pump such as that disclosed in U.S. Patent No. 5,911,685, which is particularly configured for temporary placement or implantation within a patient's left or right heart. As noted above, the present invention is particularly useful for intravascular blood pumps and is less relevant to larger VADs that are not placed within a blood vessel or the heart but are instead placed outside the patient's heart, for example, implanted in the thoracic cavity.

[0049] Preferably, the blood pump is a low inertia device. (a) The blood pump is a low inertia device by having one or more of the following characteristics: (b) the moving parts, particularly the rotating parts, e.g., rotors or impellers, of the blood pump have low mass, e.g., by being made of lightweight materials such as plastic; (c) the drive unit, e.g., electric motor, is located near, preferably very close to, and most preferably adjacent to, the moving parts, e.g., rotors or impellers, of the pump unit driven by the drive unit; (d) if the blood pump is catheter-based, there are no rotary drive cables or wires; (e) the couplings or connections, e.g., shafts, of the drive unit to the rotating parts, e.g., rotors or impellers, of the pump unit driven by the drive unit are short; and (f) all moving parts, particularly the rotating parts, of the blood pump have small diameters.

[0050] Low-inertia devices include, in particular, intravascular blood pumps for percutaneous insertion into a patient's blood vessels. Because of their small diameter, especially compared to relatively bulky VADs, all moving parts of the intravascular blood pump are lightweight and located close to the axis of rotation. This allows for very precise control of the pump speed, since the impeller rotation is only slightly affected by the impeller's inertia. This means that there is only a short delay between a command signal and the actual response of the blood pump. In contrast, VADs designed as centrifugal blood pumps, for example, may be bulky and have a large diameter, thereby having a large rotor with a larger mass, and may not be referred to as "low-inertia devices."

[0051] One characteristic of low-inertia devices is that, for example, reducing the pump speed of a low-inertia device, and particularly reducing the pump speed rapidly, does not require a negative speed signal (as typically required in large VADs) or other braking command; rather, the pump speed is reduced by directly reducing the motor current; thus, the blood pump can be placed into zero-flow control mode simply by reducing the motor current. This is particularly relevant for single-beat control because the cardiac cycle is very short and requires short reaction times for the moving parts of the blood pump. Conversely, to exit zero-flow control mode, it is equally desirable to rapidly accelerate the moving parts, i.e., to rapidly increase the pump speed.

[0052] For example, when using a low inertia device in the sense of the present invention, it is possible to significantly increase or decrease the pump speed in a very short time, for example within about 50 ms to about 100 ms, and preferably 60 ms to 80 ms, In other words, the pump speed can be changed quickly or "step-changed".

[0053] For example, within the above time ranges, the pump speed may be reduced from about 35,000 rpm to about 10,000 rpm, or from about 51,000 rpm to about 25,000 rpm in another blood pump, or vice versa, with the pump speed increased accordingly. However, the duration of the pump speed change is also determined by other factors, such as blood flow, pressure differential, the amount of the intended change in pump speed (i.e., the difference between the pump speed before and after the intended speed change), or timing in the cardiac cycle (due to accelerated blood flow during systole and decelerated blood flow during diastole).

[0054] The third aspect is a method for controlling the blood flow Q of the intravascular blood pump discussed in the first aspect. pump A method for controlling a set blood flow value Q(t) is provided, where the blood pump comprises a pump unit having a drive unit and configured to deliver blood from a blood flow inlet to a blood flow outlet, the method comprising: (i) adjusting a set blood flow value Q(t) to obtain a control error e(t) in a first closed-loop cycle; pump set (t) is the blood flow value Q pump (ii) calculating from the control error e(t) a set speed value n for the drive means; pump set (t) in a second closed-loop cycle; determining a set speed value n pump set (t) is the driving speed n pump By comparing with (t), the drive speed of the drive unit n pump and (t) controlling the

[0055] Preferably, the method comprises maintaining a set blood flow value Q for a predetermined zero flow control time. pump set The method further includes providing a zero flow mode in which (t) is zero, and preferably further includes setting the predetermined zero flow control time to last for a portion of one cardiac cycle of the assisted heart, or for at least one complete cardiac cycle or a portion and / or complete cardiac cycle of a predetermined number of consecutive cardiac cycles.

[0056] As described in more detail above in connection with the control device, the method uses an appropriate look-up table to calculate the blood flow Q pump The method may include determining or estimating (t).

[0057] Preferably, the first closed loop cycle is the outer control loop of the cascade control and the second closed loop cycle is the inner control loop. Cascade control systems having outer and inner control loops are described in more detail above in relation to the control device and are also useful in the present method.

[0058] Preferably, the method further comprises synchronizing the zero flow control time with at least one particular characteristic cardiac cycle event.

[0059] Preferably, the start and / or end of the zero flow control period is synchronized with the occurrence of at least one characteristic cardiac cycle event.

[0060] Preferably, the method further comprises monitoring the value of one or more characteristic cardiac parameters.

[0061] Preferably, the method further comprises identifying a trend in one or more monitored values ​​of the characteristic cardiac parameters.

[0062] A fourth aspect provides a control device according to the first aspect, configured to carry out a method according to the third aspect.

[0063] The above-discussed functions or functionalities of the control device and the corresponding functions and functionalities of the control method can be implemented by corresponding computing units in the control device's hardware or software, or any combination thereof. The computing units can be configured by corresponding computer programs having software codes for causing the computing units to perform the respective required control steps. Programmable computing units are basically known in the art and are familiar to those skilled in the art. Therefore, it is not necessary to describe the programmable computing units in detail here. The computing units can also comprise specific dedicated hardware useful for specific functions, such as one or more signal processors for processing and / or analyzing the discussed measurement signals. Furthermore, respective units for controlling the speed of the blood pump's driver can likewise be implemented by respective software modules.

[0064] The corresponding computer program may be stored on a data medium containing the computer program, or alternatively, the computer program may be transmitted without the need for a data medium, for example via the Internet, in the form of a data stream containing the computer program. [Brief explanation of the drawings]

[0065] The invention will now be described by way of example only with reference to the accompanying drawings, in which: [Figure 1] FIG. 2 is a block diagram showing feedback control. [Figure 2] FIG. 1 illustrates an exemplary blood pump positioned through the aorta, extending through the aortic valve and into the left ventricle, along with a block diagram of a control device for the pumping speed of the blood pump. [Figure 3] FIG. 2 is a detailed view of the example blood pump of FIG. 1. [Figure 4]1 is an exemplary graph showing a set of characteristic curves illustrating the relationship between the actual pressure difference between the inlet and outlet of a blood pump, the actual pumping speed of the blood pump, and the blood flow produced through the blood pump. DETAILED DESCRIPTION OF THE INVENTION

[0066] 1 is a block diagram of an embodiment of a feedback control loop for blood flow control implemented as a cascade control system. The control loop comprises an outer controller 401 and an inner controller 402. The outer controller 401 is embedded in the outer control loop and provides a blood flow command signal Q pump set (t) Generated blood flow Q pump (t) and the set point of the inner control loop, i.e., the speed command signal n of the blood pump 50. pump set By setting (t), the blood flow Q generated by the blood pump 50 shown in FIG. pump (t). The inner controller 402 is part of the inner control loop and controls the motor current I pump (t) by adjusting the speed n of the blood pump 50 pump Control (t).

[0067] In the feedback loop shown in Figure 1, the resulting blood flow Q pump (t) is the current I pump (t) and velocity n pump (t) and the generated blood flow Q pump Alternatively or additionally, another look-up table may be calculated based on the relationship between the pressure difference between the blood pump outlet 56 and the blood pump inlet 54 (see FIG. 3) and the speed n pump (t) and blood flow Q pump (t) can be used to express the relationship between the generated blood flow Q pump Another alternative or additional option for data acquisition in (t) is to use a flow sensor.

[0068] This flow control is controlled by a blood flow command signal Q, which may be a constant value (also called a set point) or a time-varying signal. pump set The blood flow Q through the blood pump 50 according to (t) pump (t) to control the constant blood flow set point Q pump set (t) may be in the range of [-5...10] L / min, preferably in the range of [0...5] L / min, and most preferably 0 L / min, or may be a very small blood flow as zero flow.

[0069] One aim of the flow control disclosed herein is to monitor the values ​​of characteristic parameters of the heart when using an implanted pump 50 in order to determine the state of cardiac recovery while reducing the impact of the pump on cardiac function. To this end, the flow control is performed at a set blood flow Q of 0 L / min. pump set A very small blood flow as (t) or zero flow can be used.

[0070] It has been found that the inner control loop can have a constant shorter time period compared to the outer control loop, thus allowing the inner control loop to react more quickly than the outer control loop, and also allowing the inner control loop to have a higher sampling rate than the outer control loop.

[0071] For example, the sampling rate of the data in the inner control loop is fs IN may be in the range of [250...10k] Hz, preferably in the range of [1...3] kHz, and most preferably 2.5 kHz.

[0072] For example, the sampling rate of the data in the outer control loop, fs OUT may be in the range of [25...1000] Hz, preferably in the range of [100...300] Hz, and most preferably 250 Hz.

[0073] 2 and 3 show an example of a blood pump. The blood pump is an intravascular blood pump configured to be inserted percutaneously into the heart. In the embodiment shown, the blood pump is a microaxial rotary blood pump, hereinafter referred to as blood pump 50. Such a blood pump is known, for example, from U.S. Pat. No. 5,911,685.

[0074] The blood pump 50 is based on a catheter 20 by which the blood pump 50 can be temporarily introduced into a ventricle of a patient's heart via a vasculature. In addition to the catheter 20, the blood pump 50 comprises a rotary drive unit 51 fixed to the catheter 20. The rotary drive unit 51 is coupled to a pump unit 52 located at a fixed axial distance from the rotary drive unit 51.

[0075] A flow cannula 53 is connected at one end to a pump unit 52 and extends from the pump unit 52, having a blood flow inlet 54 located at its other end. The blood flow inlet 54 has a soft, flexible tip 55 attached to the blood inlet 54.

[0076] Pump unit 52 includes a pump housing with a blood flow outlet 56. Pump unit 52 further includes a drive shaft 57 that protrudes from drive unit 51 into the pump housing of pump unit 52. Drive shaft 57 drives impeller 58 as a propulsion element. During operation of blood pump 50, blood is drawn in through blood flow inlet 54, conveyed through cannula 53, and discharged through blood flow outlet 56. Blood flow is created by rotating impeller 58, which is driven by drive unit 51.

[0077] In the embodiment shown, three wires pass through catheter 20: two signal wires 28A, 28B and a power supply wire 29 for powering drive unit 51 of blood pump 50. Signal wires 28A, 28B and power supply wire 29 are attached at their proximal ends to control device 100 ( FIG. 2 ). Signal wires 28A, 28B are associated with respective blood pressure sensors, each of which includes a corresponding sensor head 30 and 60. Power supply wire 29 includes a supply wire for powering drive unit 51.

[0078] The drive unit 51 may be a synchronous motor. In an exemplary configuration, the electric motor may include a plurality of motor winding units for driving an impeller 58 coupled to a drive shaft 57. The rotor of the synchronous motor may include at least one field winding, or alternatively, a permanent magnet in the case of a synchronous motor excited by a permanent magnet.

[0079] In a preferred embodiment, blood pump 50 is a catheter-based microaxial rotary blood pump for percutaneous insertion into a patient's heart through the patient's vasculature. Here, "micro" indicates a size small enough to allow the blood pump to be percutaneously inserted into the heart, such as into one of the heart's ventricles, via a blood vessel leading to the heart. This further defines blood pump 50 as an "intravascular" blood pump for percutaneous insertion. Here, "axial" indicates that pump unit 52 and drive unit 51 driving pump unit 52 are arranged in an axial configuration. Here, "rotary" means that the functionality of the pump is based on the rotational movement of a propulsion element, i.e., impeller 58, driven by a rotary electric motor of drive unit 51.

[0080] As discussed above, the blood pump 50 is based on the catheter 20, which allows insertion of the blood pump 50 through the vasculature, and through which the power supply wires 29 may pass to supply power to the drive unit 51 and to supply control signals, for example, from the drive unit 51 and the sensor heads 30, 60.

[0081] As noted above, the present invention is particularly adapted for intravascular blood pumps, such as blood pump 50 shown in Figure 3, and is less adapted for, or even suitable for, VADs that are implanted outside the patient's heart, such as centrifugal blood pumps that are connected to the patient's heart, placed within the thoracic cavity, and that operate over a range of pumping speeds. As explained herein, this is particularly due to inertial effects that significantly affect the function of large VADs, but which can be avoided in low inertia devices such as intravascular blood pumps.

[0082] 2, each signal line 28A, 28B is connected to a respective blood pressure sensor with a corresponding sensor head 30, 60, each of which is located on the exterior of the housing of the pump unit 52. The sensor head 60 of the first pressure sensor is connected to the signal line 28B and is intended to measure the blood pressure at the blood flow outlet 56. The sensor head 30 of the second blood pressure sensor is connected to the signal line 28A and is intended to measure the blood pressure at the blood flow inlet 54. Essentially, signals, which may be of any suitable physical origin, for example optical, hydraulic or electrical, and which are captured by the pressure sensors and convey respective information about the pressure at the sensor location, are transmitted via the respective signal lines 28A, 28B to corresponding input devices of the data processing unit 110 of the control device 100. In the embodiment shown in FIG. 2, blood pump 50 is positioned in the aorta and further in the left ventricle of the heart via the aortic valve, so that pressure sensors are positioned to measure aortic pressure AoP(t) with sensor head 60 and left ventricular pressure LVP(t) with sensor head 30.

[0083] The data processing unit 110 is configured to acquire external and internal signals for signal processing, which may include, for example, the generation of blood flow Q pump The present invention includes calculating the difference between the pressure signals as a basis for estimating σ(t). The external and internal signals can serve as control signals for this flow control approach, for signal analysis aimed at detecting the occurrence of characteristic events during the cardiac cycle based on the acquired and calculated signals, and for generating a trigger signal σ(t) aimed at initiating the velocity command signal generator 120, to name a few.

[0084] As a given example of a flow control technique, velocity command signal generator 120 represents outer controller 401 in FIG.

[0085] In the embodiment shown, the data processing unit 110 is connected via corresponding signal lines to additional measurement devices, generally depicted at 300. Such additional measurement devices are in this embodiment a patient monitoring unit 310 and an electrocardiograph (ECG) 320, although it will be apparent that these two devices 310 and 320 are merely two examples and not all inclusive, i.e., other measurement devices may be used to provide similarly useful signals. The depicted ECG 320 provides an ECG signal ECG(t) to the data processing unit 110.

[0086] The control device 100 further comprises a user interface 200 for interaction with a user of the device. The user interface 200 comprises a display 210 as an output means and a communication interface 220 as an input means. On the display 210, values ​​of set parameters, values ​​of monitored parameters such as measured pressure values, and other information are displayed. Furthermore, the communication interface 220 allows the user of the control device 100 to control the control device 100, for example, by changing the setup and settings of the entire system consisting of the blood pump and the control device 100.

[0087] For the example flow control technique given here, the setting is the desired pump flow Q in Figure 1. pump set The answer is to select (t).

[0088] The data processing unit 110 is particularly configured to derive or predict the timing of occurrence of one or more predetermined characteristic events during the cardiac cycle of the assisted heart. For example, the data processing unit 110 is configured to detect the predetermined characteristic cardiac cycle events during the cardiac cycle by real-time analysis of the monitored signals. Alternatively or additionally, the predetermined characteristic cardiac cycle events, such as R waves, can be identified by an ECG signal from the ECG 320.

[0089] The occurrence of one or more determined predetermined characteristic events is utilized to generate a particular trigger signal σ(t) or a series of trigger signals σ(t). The resulting trigger signal σ(t) (or series of trigger signals) is forwarded to the velocity command signal generator 120, thereby initiating a corresponding modification of the velocity command signal provided to the velocity control unit 130.

[0090] In the context of the present invention, the speed command signal generator 120 is configured to operate the blood pump 50 in a zero flow control mode.

[0091] The data processing unit 110 is adapted to predict the timing of occurrence of at least one predetermined characteristic cardiac cycle event during the next cardiac cycle based on stored information regarding characteristic cardiac cycle events occurring during the most recent and / or previous cardiac cycles, and to generate these rate command signals n pump set Previous values ​​of (t) are configured to be analyzed as well.

[0092] For example, a characteristic cardiac cycle event may be the onset of cardiac contraction at the beginning of systole. The detected or predicted occurrence of such a characteristic cardiac cycle event may be utilized to synchronize the application of a particular control strategy for blood pump 50 to a range of one or more cardiac cycles or to a particular time interval within the cardiac cycle.

[0093] Correspondingly, the rate command signal generator 120 generates a given blood flow command signal Q, which may be set to, for example, 0 L / min. pump set According to (t), the generated blood flow Q pump The speed command signal n to the blood pump 50 is used to control pump set (t) is configured to adjust.

[0094] Generated blood flow Q pumpTo control (t), a velocity command signal generator 120 generates a blood flow Q pump (t) in a time-uninterrupted manner (as a first setup) or in an event-based switching manner (as a second setup), by controlling the appropriate speed command signal n pump set (t) to the speed control unit 130.

[0095] In the first setup, the command signal generator 120 generates a velocity command signal n as part of a cascade blood flow control system supplied with external and internal signals by the data processing unit 10. pump set (t) is continuously provided to the rate control unit 130.

[0096] In the second setup, the velocity command signal generator 120 operates similarly to the first setup, but now with additional structure for switching the continuous blood flow control on and off.

[0097] In zero flow control mode, the speed command signal n pump set (t) is continuously adjusted by a flow controller in the outer control loop. The on / off switching is initiated by at least one trigger signal σ(t) provided by the data processing unit 110.

[0098] The second setup is appropriate when the zero flow control is applied only for short time intervals, particularly short when compared to the duration of one cardiac cycle. In other words, the generated blood flow is controlled by a blood flow command signal Q of 0 L / min only for a short time interval in this cardiac cycle. pump set (t) is used to control the blood flow in one heartbeat.

[0099] The speed control unit 130 generates a speed command signal n pumpset According to (t), a current I is supplied to the drive unit 51 of the blood pump 50 via the power supply line 29. pump (t) to increase the speed of the blood pump 50 pump Control (t).

[0100] Supplied motor current I pump The latest level of (t) is, for example, the speed command signal n pump set (t) corresponds to the current required at that time by, for example, the electric motor of the drive unit 51 to establish the target speed level defined by (t). pump Measurement signals such as (t) may be used as representative signals of internal signals of the control device 100 and may be provided to the data processing unit 110 for further processing. Via the power supply line 29, the blood pump 50 may further communicate with the control unit 100.

[0101] Basically, among other things, the control device 100 is configured to operate the blood pump 50 in a selectable zero flow control mode, in which the blood flow Q of the blood pump 50 is pump (t) is controlled to counteract the effect of a varying pressure difference between the blood outlet 56 and the blood inlet 54 due to cardiac pulsation, which may be considered a disturbance. pump set By adjusting (t), the blood flow Q pump As proposed herein, the control device 100 controls the blood flow Q of the blood pump 50. pump (t) so that the blood pump 50 generates zero blood flow for a predetermined zero flow control time.

[0102] In a first setup using continuous flow control, the predetermined zero flow control time is set to last for at least one complete cardiac cycle or a predetermined number of consecutive complete cardiac cycles. Further, in the first setup, the control device 100 is configured to monitor the values ​​of one or more characteristic cardiac parameters using the implanted blood pump 50. Again, the monitored values ​​of the one or more characteristic cardiac parameters can be used as indicators for the state of cardiac recovery.

[0103] In a second setup using event-based zero flow control, the predetermined zero flow control time is set to be a fraction of the duration of one cardiac cycle of the heart implanted with blood pump 50. In this setup, control device 100 is configured to synchronize the start and end of the zero flow control time with the occurrence of certain characteristic cardiac cycle events.

[0104] In particular, the control device 100 periodically or irregularly controls the blood flow Q through the blood pump 50. pump (t) can be controlled.

[0105] In certain implementations, the characteristic cardiac cycle event is an aortic valve opening or aortic valve closing, or a mitral valve opening or mitral valve closing, or a particular pressure value as the end-diastolic left ventricular pressure.

[0106] Furthermore, in the second setup, similar to the first setup, the control device 100 is configured to monitor, during the zero flow control time, the values ​​of one or more characteristic cardiac parameters of the heart implanted with the blood pump 50. The monitored values ​​of the one or more characteristic cardiac parameters may likewise be used as indicators for the state of cardiac recovery.

[0107] The control device 100 is further configured to identify trends in the values ​​of one or more monitored characteristic parameters, which, as mentioned herein above, may also be interpreted as an indicator for the state of cardiac recovery.

[0108] In either case, to implement the zero flow control mode, the control device 100 generates a speed command signal n pump set (t) by adjusting the blood flow Q pump (t), thereby controlling the drive speed n pump (t) is subject to the varying pressure difference between the blood flow outlet 56 of the blood pump 50 and the blood flow inlet 54 of the blood pump 50 during the cardiac cycle.

[0109] In particular, the control device 100 may, for example, determine the driving speed n pump (t), current I pump (t), and / or the blood flow Q of the blood pump 50 based on a predetermined signal, such as the pressure difference between the blood flow outlet 56 and the blood flow inlet 54 of the blood pump 50. pump (t) is configured to determine

[0110] FIG. 4 shows the pressure difference ΔP between the blood flow outlet 56 and the blood flow inlet 54 of the blood pump 50. pump (t) and the driving speed n of the blood pump 50 pump (t) and the blood flow Q generated by the blood pump 50, for example, through the flow cannula 53 of FIG. pump 1 is an exemplary graph showing a set of characteristic curves representing the relationship between (t) and

[0111] To achieve zero flow control, the data processing unit 110 calculates the flow rate at a known rate n pump (t), the known current I supplied to the pump unit 51 pump (t), and / or the monitored pressure difference ΔP between the blood flow outlet 56 and the blood flow inlet 54 of the blood pump 50. pump Based on (t), the blood flow Q generated by the blood pump 50 pump (t) is continuously determined.pump set (t) may be zero, or at least a positive value close to zero.

[0112] For example, based on FIG. 4, the monitored pressure difference ΔP between the blood flow outlet 56 and the blood flow inlet 54 of the blood pump 50 is pump In the case where (t) is 60 mmHg, the driving speed n pump (t) is approximately 0 L / min blood flow Q pump To generate (t), the rotation speed needs to be approximately 20,000 rpm.

[0113] It will be appreciated that the values, relationships, and shapes of the curves shown in the characteristic graph of Figure 4 are merely exemplary and may vary depending on the blood pump used, the patient, or other factors. Specifically, each and every blood pump, or even blood pumps of a similar type, may have an individual characteristic graph, i.e., the look-up table may be pump-specific. Furthermore, once implanted in a patient, the characteristic graph may need to be adapted with patient-specific correction factors, which may include a variety of factors such as blood viscosity, blood pump location, etc. The use of correction factors may improve the accuracy of the flow estimates achieved by the look-up table.

[0114] As discussed above, the latest pressure difference ΔP pump 4 (where ΔP is the value discussed above) can be determined by a pressure sensor (e.g., sensors 30, 60 of FIG. 3) in the blood pump 50. Thus, the speed control unit 130 can determine the pressure (ΔP) in the blood pump 50, e.g., by a pressure sensor (e.g., sensors 30, 60 of FIG. 3). pump (t), Q pump (t), and n pump The blood pump 50 may be continuously provided with values ​​from a memory unit, such as a look-up table having stored therein a characteristic curve (representing the relationship between (t) and (t)) that represents the relationship between (t) and (t). This memory unit may be a read-only memory of the data processing unit 110, or alternatively may be a memory chip located within the blood pump 50 or within its control console 130.

[0115] The value of the at least one characteristic cardiac parameter is at least one of: arterial blood pressure, which is measured each time a zero-flow operating mode is established.

[0116] Preferably, blood pump 50 is a low-inertia device. This is achieved in particular by having low mass for the moving parts, specifically the rotating parts, such as the rotor or impeller, of blood pump 50, by being made of lightweight materials, such as plastic. In addition, a drive unit, such as an electric motor, is located near, preferably very close to, and most preferably adjacent to, the parts, such as the propulsion elements, such as rotor or impeller 58, that are driven by the drive unit. In addition, even if blood pump 50 is catheter-based, there are no rotary drive cables or wires. In addition, the couplings or connections to the propulsion elements, such as rotor or impeller 58, that are driven by drive unit 51, i.e., the couplings or connections, such as shaft 57 of drive unit 51, are kept short. In addition, all moving parts, specifically the rotating parts, of blood pump 50 have small diameters.

[0117] In summary, in the zero flow control approach proposed herein, the control device 100 controls the generated blood flow Q through the blood pump 50 in a cascade control consisting of an outer control loop and an inner control loop. pump (t) which controls the generated blood flow Q through the pump unit 50 pump (t) is the speed command signal n to the drive unit 51 of the blood pump 50 in the outer control loop. pump set (t) and the current I pump (t) by adjusting the driving speed n pumpThis means that (t) is controlled within the inner control loop. This zero flow control technique may be applied continuously or partially continuously, i.e., the zero flow control time may last for one or more complete cardiac cycles or for only a portion of a cardiac cycle. In cases where a given zero flow control time lasts for only a portion of the duration of a cardiac cycle, the zero flow control time may be synchronized with the cardiac beat of at least one characteristic event of the cardiac cycle.

Claims

1. The blood flow Q of an intravascular blood pump (50) for percutaneous insertion into a patient's blood vessel. ｐｕｍｐ a control device (100) for controlling (t), wherein the blood pump (50) comprises a pump unit (52) and a drive unit (51) for driving the pump unit, the drive unit being configured to transport blood from a blood inlet (54) towards a blood outlet (56); The control device (100) is configured to operate the blood pump (50) in a selectable zero flow control mode, and a blood flow command signal Q ｐｕｍｐ ｓｅｔ (t) is selected, and the control device comprises a first control device (401) and a second control device (402); The first control device (401) outputs a speed command signal n to the drive unit (51). ｐｕｍｐ ｓｅｔ (t) to adjust the blood flow Q ｐｕｍｐ (t), and the second control device (402) controls the drive speed n ｐｕｍｐ (t), A control device (100) characterized in that:

2. 2. The control device (100) of claim 1, wherein the first control unit (401) controls the blood flow command signal Q ｐｕｍｐ ｓｅｔ (t) and the blood flow Q ｐｕｍｐ (t) based on the difference ΔQ between ｐｕｍｐ ｓｅｔ (t).

3. 3. The control device (100) according to claim 1 or 2, wherein the second control device (402) controls the drive current I supplied to the drive unit (51). ｐｕｍｐ (t) to adjust the driving speed n ｐｕｍｐ 1. A control device (100) configured to control (t).

4. 4. The control device (100) according to claim 1, wherein the first control device (401) and the second control device (402) are part of a cascade control system, the first control device (401) being an outer control device and the second control device being an inner control device (402).

5. 5. The control device (100) of claim 1, wherein the control device (100) controls the blood flow Q over a predetermined zero flow control time. ｐｕｍｐ 1. A control device (100) configured to control (t).

6. 6. A control device (100) according to claim 5, the predetermined zero-flow control time is set to last for a portion of one cardiac cycle of the assisted heart; or the predetermined zero flow control time is set to last for at least one complete cardiac cycle or a predetermined number of consecutive complete cardiac cycles; A control device (100) characterized in that:

7. 7. A control device (100) according to any one of claims 1 to 6, characterized in that the control device (100) is configured to synchronize the zero flow control time with the occurrence of at least one characteristic cardiac cycle event.

8. 8. The control device of claim 7, wherein the start and / or end of the zero flow control period is synchronized with the occurrence of the at least one characteristic cardiac cycle event.

9. 9. The control device (100) of claim 8, wherein the at least one characteristic cardiac cycle event is an aortic valve opening or an aortic valve closing.

10. 10. The control device (100) according to any one of claims 1 to 9, characterized in that the control device (100) is configured to monitor values ​​of one or more characteristic cardiac parameters.

11. 11. The control device (100) of claim 1, wherein the control device (100) is configured to operate the blood pump (50) in the zero flow control mode periodically or irregularly.

12. 12. The control device (100) of claim 1, wherein the control device (100) is configured to identify trends in the values ​​of one or more monitored characteristic cardiac parameters.

13. 13. The control device (100) according to claim 12, wherein the at least one characteristic cardiac parameter is a pulsatile arterial pressure (AOP) | ｍａｘ -AOP | ｍｉｎ , mean arterial pressure, cardiac contractility dLVP(t) / dt | ｍａｘ , cardiac relaxation dLVP(t) / dt | ｍｉｎ , heart rate HR.

14. 14. The control device (100) according to any one of claims 1 to 13, wherein the control device (100) measures the blood flow Q by a sensor. ｐｕｍｐ (t) or the blood flow Q ｐｕｍｐ 2. A control device (100) configured to calculate or estimate (t).

15. 15. The control device (100) according to any one of claims 1 to 14, wherein the control device (100) controls the blood flow Q ｐｕｍｐ (t) and the driving speed n ｐｕｍｐ (t) and the pressure difference ΔP between the blood flow outlet (56) and the blood flow inlet (54). ｐｕｍｐ (t) and the drive current I supplied to the drive unit (51) ｐｕｍｐ (t) and the blood flow Q ｐｕｍｐ (t).

16. A system comprising an intravascular blood pump (50) for percutaneous insertion into a blood vessel of a patient and a control device (100) according to any one of claims 1 to 15.

17. 17. The system of claim 16, wherein the blood pump (50) is a low inertia device by having one or more of the following properties: the moving parts of the blood pump, in particular the rotating parts, such as the rotor or impeller, have a low mass, for example by being made of lightweight materials, such as plastic; the drive unit (51), such as an electric motor, is located close to, preferably very close to and most preferably adjacent to, the moving parts, such as the rotor or impeller, that are driven by the drive unit (51); if catheter-based, preferably has no rotary drive cables or wires; the couplings or connections, such as shafts, of the drive unit (51) to the rotating parts, such as the rotor or impeller, that are driven by the drive unit (51); and all moving parts, such as rotating parts, of the blood pump have small diameters.

18. The blood flow Q of an intravascular blood pump (50) for percutaneous insertion into a patient's blood vessel. ｐｕｍｐ 1. A method for controlling (t), wherein the blood pump (50) comprises a pump unit (52) having a drive unit (51) and configured to transport blood from a blood inlet (54) towards a blood outlet (56), the method comprising: To obtain the control error e(t) in the first closed-loop cycle, the set blood flow value Q ｐｕｍｐ ｓｅｔ (t) is the blood flow value Q ｐｕｍｐ (t) and comparing it with From the control error e(t), the set speed value n for the drive means is calculated. ｐｕｍｐ ｓｅｔ determining (t); In the second closed loop cycle, the set speed value n ｐｕｍｐ ｓｅｔ (t) is the driving speed n ｐｕｍｐ (t), the driving speed n ｐｕｍｐ (t) and Including, A method characterized by:

19. 20. The method of claim 18, The set blood flow value Q for a predetermined zero flow control time ｐｕｍｐ ｓｅｔ providing a zero flow mode in which (t) is zero; Preferably, the predetermined zero flow control time is set to last for a portion of one cardiac cycle of the assisted heart, or for at least one complete cardiac cycle or a predetermined number of portions and / or complete cardiac cycles of consecutive cardiac cycles. The method further comprising:

20. 20. The method of claim 18 or 19, wherein the first closed loop cycle is an outer control loop and the second closed loop cycle is an inner control loop of a cascade control.

21. 21. The method of any one of claims 18 to 20, Synchronizing the zero flow control time with at least one particular characteristic cardiac cycle event. The method further comprising:

22. 22. The method of any one of claims 18 to 21, wherein the start and / or end of the zero flow control time is synchronized with the occurrence of the at least one characteristic cardiac cycle event.

23. 23. The method of any one of claims 18 to 22, comprising: monitoring the value of one or more characteristic cardiac parameters; The method further comprising:

24. 24. The method of any one of claims 18 to 23, comprising: Identifying trends in one or more monitored values ​​of the characteristic cardiac parameters. The method further comprising:

25. A control device (100) according to any one of claims 1 to 14, configured to carry out a method according to any one of claims 18 to 24.

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