Extracorporeal circulation support with cardiac activity optimized delay time

Abstract

The invention relates to a method for controlling extracorporeal circulation support and to a corresponding device for controlling extracorporeal circulation support and to a circulation support device, in particular for reducing the after-load of a patient. Accordingly, a method for controlling extracorporeal circulation support of a patient is described, the method comprising the steps of: receiving cardiac measurements (10) of a supported patient; determining a systolic start (16) of a current cardiac cycle of the patient from the cardiac measurements (10); and providing a trigger signal with a delay time (24) for extracorporeal circulation support for the current cardiac cycle after the determined systolic period begins (16). According to the invention, the delay time (24) is selected based on cardiac activity determined from cardiac measurements (10) of at least one previous cardiac cycle, the cardiac activity indicating a systolic duration (20).

Description

Field of the Invention

[0001] The present invention relates to a method for controlling extracorporeal circulation support, a corresponding device for controlling extracorporeal circulation support, and a circulation support device. Background Art

[0002] Cardiogenic shock may occur when the pumping ability or function of the heart fails. A reduction in cardiac output or ejection volume generally leads to a reduction in perfusion or blood flow to end organs such as the brain, kidneys, and vascular system. Thus, acute heart failure can result in an acute lack of blood supply in tissues and organs, accompanied by insufficient oxygen supply, also known as hypoxia, which may result in end organ damage.

[0003] To stabilize the patient's condition, circulatory support systems have been developed, which provide mechanical support and can be quickly connected to the circulatory system. The circulatory support system can improve blood flow and perfusion of organs (including the coronary vessels of the heart) and prevent hypoxic states. For example, extracorporeal circulation support systems are known, which are capable of withdrawing blood from, for example, the right atrium or vena cava through a cannula inserted into the femoral vein and returning the blood to the patient via a perfusion cannula inserted into the femoral artery with the aid of a membrane oxygenator. The membrane oxygenator consumes CO2 and oxygenates the blood. Such a system is also referred to as "extracorporeal membrane oxygenation" (ECMO).

[0004] Although this achieves better perfusion of the organs, the perfusion or return of the blood occurs continuously during both the systolic and diastolic phases. Thus, such an arrangement leads to a reverse blood flow, which is opposite to the actual ejection direction of the heart, thereby increasing the afterload in an undesirable manner. As a result, blood accumulates in the left ventricle and is no longer ejected. The left ventricle is unnaturally stretched. Thus, cardiac ejection is blocked and the left ventricle is no longer emptied sufficiently. At the same time, the heart has to do more muscular work and requires a correspondingly increased oxygen supply. This finding has proven to be very disadvantageous especially in cases where the heart has been damaged by a myocardial infarction. In such cases, perfusion and microcirculation of the heart, organs, and brain are reduced in the presence of continuous blood flow because the human circulation or perfusion is based on the pulsatility of the heart.

[0005] To reduce the afterload, systems have been developed that insert a pump into the left ventricle to prevent overstretching of the left ventricle. Another approach is based on inserting a balloon into the aortic region. The balloon is rapidly inflated based on an EKG signal, for example using helium, to improve blood flow to the myocardial tissue during the cardiac cycle phase. Such a system is referred to as "intra-aortic balloon pump" (IABP). However, the effect of such a system is limited because only blood that is not sufficiently oxygenated is delivered to the coronary vessels. In addition, this (potentially additional) procedure greatly increases the invasiveness of the treatment.

[0006] To reduce afterload, the circulatory support system can also be synchronized with the patient's heartbeat as an alternative to continuous blood return. For example, based on the R wave detected in the EKG signal, the pump is controlled by a delay time. The delay time is manually set to a predefined value. The complexity and dynamics of the patient's own heart activity require fine time control or fine-tuning of the extracorporeal support.

[0007] Therefore, a method is needed to allow afterload reduction during extracorporeal circulatory support. Summary of the Invention

[0008] According to the present invention, it has been recognized that for a provided trigger signal, the provided circulatory support with a predetermined delay time may result in, for example, non-application of a pulse from the blood pump during an expected cardiac cycle phase. The perfusion of the coronary arteries of the heart, which normally provides sufficient oxygen to the myocardium, usually occurs during the diastolic phase of the cardiac cycle. At this time, appropriate emptying of the left ventricle is required. If the filling pressure in the left ventricle is as low as possible at the end of systole or the beginning of diastole, then the coronary arteries can widen their lumen as much as possible. In this way, blood flow rate and oxygen supply increase. However, as the patient's condition changes, i.e., the patient's current condition or vital signs change, perfusion may inadvertently be provided during systole. Then, the provided blood flow may, for example, block the aortic valve and further increase the pressure in the left ventricle, especially if the blood cannot escape from it. This increased pressure may trigger a further reduction in coronary artery perfusion, thus offsetting the therapeutic effect.

[0009] Furthermore, according to the present invention, it has been recognized that incorrect timing of the provided blood flow based on a fixed preset delay time particularly occurs at different heart rates. This method does not allow for consideration of the changes in each cardiac cycle phase. Therefore, it is not possible to perform timing that takes into account the specific and current condition of the cardiac cycle phase.

[0010] Therefore, based on the known prior art, the object of the present invention is to further improve the circulatory support to be provided, in particular to optimize the timing of the trigger signal to be provided, even in the case of changes in the patient's condition.

[0011] The object is achieved by the subject matter claimed in the independent claims. The dependent claims, the description and the drawings define advantageous further embodiments.

[0012] Therefore, a method for controlling extracorporeal circulatory support for a patient is proposed, the method comprising the following steps:

[0013] - Receiving cardiac measurements of the supported patient;

[0014] - Determining the start of systole of the patient's current cardiac cycle from the cardiac measurements; and

[0015] - Provide a trigger signal with a delay time for extracorporeal circulation support for the current cardiac cycle after the start of the determined systolic phase.

[0016] According to the present invention, the delay time is selected based on cardiac activity determined from cardiac measurements of at least one previous cardiac cycle, and the cardiac activity indicates the systolic duration.

[0017] Therefore, the delay time of the current cardiac cycle can be adjusted according to cardiac activity. The dynamically designed delay time allows the provision of the trigger signal to adapt to the current changes in the patient's condition. In this way, inadvertent coronary perfusion during systole can be avoided. This is particularly important because cardiac activity is characteristic of the systolic duration and thus needs to be taken into account when providing the trigger signal with an appropriately adjusted delay time. Therefore, according to the present invention, compared with a fixed preset delay time, afterload can be largely avoided or at least significantly reduced, and at the same time, improved perfusion of the end organs, especially the cardiac coronary arteries, can be ensured. The cardiac activity can be determined for the immediately preceding cardiac cycle or a plurality of previous cardiac cycles. However, preferably, the trigger signal is determined within a period of time before the start of the systolic phase of the current cardiac cycle so that the provision of the trigger signal is not affected.

[0018] Preferably, cardiac measurements are continuously acquired and received during extracorporeal circulation support to receive high-resolution measurements and contribute to the determination of the start of the systolic phase and cardiac activity. For example, the measurements can be received within a predetermined period corresponding to a treatment procedure or a segment or part of a treatment procedure.

[0019] The advantage of determining the start of the systolic phase and the associated delay time is that the cardiac cycle phase can be clearly determined for the corresponding cardiac cycle, so that a trigger signal with high time stability can be provided.

[0020] Preferably, the cardiac activity is determined for each cardiac cycle, and the delay time is selected on a cardiac cycle-specific basis for each cardiac cycle. Therefore, the delay time can be adjusted basically in real time. Advantageously, the delay time is also optimized for the current cardiac cycle or the trigger signal to be output. In this case, for the current cardiac cycle, for example, in order to take into account the rapid changes in cardiac activity, usually only the cardiac activity of the immediately preceding cardiac cycle is considered. However, alternatively, the cardiac activity of a predetermined number of previous cardiac cycles can be considered to adjust the delay time. Therefore, for example, the (moving) average of the cardiac activity of the last two, three, four or 5 to 10 cardiac cycles can be considered. This has the advantage that, for example, the weight of individual outliers in the previous cardiac cycles is lower. In addition, the selected delay time is less affected by any measurement fluctuations that may occur.

[0021] As described above, since cardiac activity is characteristic of the systolic duration and is taken into account when selecting or adjusting the delay time of the current cardiac cycle, it is possible to prevent a trigger signal from being provided during the systole of the current cardiac cycle. Preferably, the cardiac activity at least includes the onset of diastole of the corresponding cardiac cycle. For example, the cardiac activity may include or define the closure of the aortic valve, which occurs at the end of the systolic phase or at the onset of diastole and indicates the filling phase of the heart. In this way, a trigger signal with a corresponding delay time can be provided for the current cardiac cycle with an increased probability, such that for example the pulse falls within the diastole of the cardiac cycle or does not fall within the time period when the heart valve is open.

[0022] Advantageously, the delay time can be selected based on the heart rate determined from cardiac measurements. Thus, when adjusting or setting the delay time, the changes in heart rate and the associated changes in the corresponding cardiac cycle phases can be regarded as a dynamically changing patient condition. This allows for a more accurate determination or selection of the delay time for providing a trigger signal at the expected cardiac cycle phase.

[0023] Preferably, the heart rate is determined for the current cardiac cycle, or the heart rate includes the current cardiac cycle. For example, the corresponding determined onset of systole of the current cardiac cycle can be used as the basis for the determined heart rate. In this way, the delay time can also take into account any fluctuations in heart rate during the current cardiac cycle phase. For example, the heart rate can be determined using only the corresponding determined onset of systole of the current cardiac cycle and the immediately preceding cardiac cycle. Thus, the heart rate can be determined with high precision based on the current patient condition or trend. Alternatively, the heart rate can also be determined for a predetermined number of cardiac cycles, for example, for the last five onsets of systole. This compensates for or flattens out minor and / or negligible fluctuations in heart rate. Given the stability of the heart rate, the corresponding trigger stability can be ensured.

[0024] The cardiac measurements preferably include the patient's EKG signal, wherein the onset of systole and cardiac activity are determined using the EKG signal. For example, based on the EKG signal, characteristic amplitudes can be determined for the corresponding different cardiac cycle phases. Thus, the R peak or R wave, which is characteristic of the onset of the systolic phase of the cardiac cycle, is generally easily distinguishable from other phases of the cardiac cycle, for example in the QRS complex. Thus, the R wave can be used to control extracorporeal circulation support with an appropriate delay time by means of a trigger signal, for example, to control a blood pump during consecutive diastolic phases.

[0025] The variation of the characteristic amplitude also enables the determination of the contraction duration with high precision, so that the delay time for providing the trigger signal can be appropriately set. Therefore, in order to determine the cardiac activity, it is preferable to consider the QT time obtained from the EKG signal. The QT time corresponds to the time period of the cardiac cycle from the start of the Q wave of the QRS complex to the end of the consecutive T wave. The time of the end of the T wave physiologically corresponds to the closure of the aortic valve and thus marks the end of the systolic phase or the start of the diastolic phase.

[0026] It has proven advantageous to consider the QT duration because it approximately corresponds to the duration of the diastolic phase, and the delay time can thus be even more precisely adapted to the desired time for delivering the trigger signal in the corresponding cardiac cycle phase.

[0027] Preferably, the QT time is normalized and / or considered by means of the heart rate determined from the EKG signal. The QT time usually depends on the patient's heart rate. Therefore, it can be expected that changes in the QT time may be accompanied by changes in the heart rate. Conversely, this makes it particularly advantageous to determine the delay time optimized for the heart rate. For the corresponding heart rate, a standardized QT time can be expected. For example, the "Framingham formula" can be used to select the delay time to represent the QT time based on the heart rate. Therefore, using the normalized value and the current heart rate, the (theoretical) delay time for the current cardiac cycle can be calculated. Such a normalized value can be based on empirical values and can be predefined, for example, according to a previous dataset that has been previously evaluated and verified offline. For example, the delay time can be calculated using the following variant of the Framingham formula:

[0028] Delay time = 380 - 154×(1 - 60 / heart rate).

[0029] Preferably, the heart rate is determined by covering the start of the systolic phase of the corresponding cardiac cycle, for example, by means of the time interval between two R waves of consecutive cardiac cycles, i.e., the so-called R-R interval. In this way, the heart rate of the current cardiac cycle can also be considered. Therefore, the delay time can be determined and optimized for each cardiac cycle. If the heart rate changes, the delay time will be quasi-automatically corrected. For example, if the systolic phase is shortened due to an increase in the heart rate, the delay time can be adjusted accordingly. This is because when determining the delay time, the heart rate allows for the corresponding shortening of the QT time to be considered. Therefore, the trigger signal can be delivered with an increased probability at a time that does not fall into the systolic phase. Therefore, the afterload can be minimized or even avoided.

[0030] In other words, it can be advantageously selected or determined based on a specific heart rate, where the QT time value that is decisive for the delay time can be determined or considered (possibly only) based on the heart rate.

[0031] Cardiac measurements may include a pressure corresponding to the patient's aortic pressure. Cardiac activity can be determined with the aid of the pressure values. For example, the systolic duration can be determined with the aid of the corresponding pressure amplitude or pressure increase and pressure decrease. The time of the pressure increase can further be used as a measure of the start time of the systole. In addition to the EKG signal, the aortic pressure can also be received. The redundancy of the data or information obtained can serve and help, for example, to increase the safety of extracorporeal circulation support. This applies, for example, to the case where cardiac measurements are missing for a corresponding, especially current, cardiac cycle.

[0032] This redundancy can also be used to monitor cardiac measurements. This is achieved, for example, by determining the start time of the systole by means of the EKG signal (e.g., by determining the R wave) and by means of the pressure increase and comparing the corresponding time points with each other. If the deviation is small, the time points can be averaged. However, if the deviation or difference of the determined time points exceeds a predefined threshold, a specific cardiac measurement can be selected if necessary. This applies, for example, to the case where fluctuations or interference signals occur for other or further corresponding cardiac measurements. A (possibly higher) threshold can also be provided, exceeding which can trigger an alarm signal.

[0033] Therefore, the accuracy of the time point of the trigger signal to be provided, for example for controlling a blood pump, can also be further improved by combining the EKG signal and the measured aortic pressure. Thus, any EKG interference will no longer compromise the patient's safety and the function of extracorporeal circulation support.

[0034] Preferably, the pressure value is used to determine the dicrotic point of the corresponding cardiac cycle, and the systolic duration is determined based on the dicrotic point. The pressure value can also be used to determine the start of the systole of the corresponding cardiac cycle and display the systolic duration (based on the dicrotic point).

[0035] For example, a brief increase in the aortic pressure after a previous decrease in the aortic pressure can indicate the closure of the aortic valve, thus indicating the end of the systole and the start of the corresponding diastole or the filling phase of the heart. Such a pressure change can be detected, for example, as a dicrotic point in the pressure curve, also known as a "dicrotic notch". The start of the systole can also be determined based on the pressure curve. For example, when it is determined that the pressure increase exceeds a predetermined threshold and / or a pressure increase is detected after a predetermined pressure decrease, this mode is enabled. In addition, the end point of the T wave can be determined from the EKG signal, which also physiologically corresponds to the closure of the aortic valve. Then the systolic duration can be determined with a certain level of safety redundancy.

[0036] Accordingly, the delay time can be determined by means of the pressure value corresponding to the patient's aortic pressure. It can preferably be selected such that a trigger signal is provided after the dicrotic notch, or a delivery pulse of extracorporeal circulation support is applied after the dicrotic notch. Advantageously, the pulse should be completed before the pressure curve increases again.

[0037] For example, the delay can be selected such that the pump signal is delivered when the pressure in the aorta increases briefly, marking the time point of aortic valve closure and thus marking the start of diastole. By actuating the motor or pump driver and the rotor blades and triggering the pulse at this time point, the (pulsatile) blood flow can be delivered, for example via an arterial cannula, to the region immediately downstream of the left ventricle and into the aorta. The positioning of the cannula tip and the direction of reverse flow ultimately result in an increased pulsatile blood flow in the coronary arteries. Accordingly, a correspondingly improved blood flow to the myocardial tissue is provided without compromising the systemic circulation.

[0038] Since the additional blood flow only occurs after aortic valve closure and preferably terminates before the start of the successive systolic phase, the afterload can be reduced while at the same time diastole can be increased even with sufficient perfusion of the end organs.

[0039] The pressure value can be measured, for example, at the tubing set of the extracorporeal circulation support and / or by means of a cannula located at the level of the patient's aortic arch.

[0040] For example, the arterial pressure can be received via an interface communicatively connected to at least one pressure sensor. Preferably, the pressure measurement is performed upstream of the blood pump, downstream of the blood pump, and / or downstream of an oxygenator or membrane ventilator provided in the extracorporeal circulation system and connected to the blood pump. The pressure measurement of the arterial pressure of the supported patient can be performed invasively in the patient's body, for example at the cannula tip of an arterial cannula, for example in the patient's aorta, or by means of another pressure measurement probe, which can be positioned at an appropriate location in the aorta, for example, or can also be positioned in the femoral artery and / or iliac artery or radial artery. In this way, potential interferences caused by the pulse wave conduction time through the cannula and tubing set can be eliminated.

[0041] A non-invasive pressure sensor (without direct blood contact) can be used to measure the pressure, or invasive pressure measurement can be used to measure the pressure, where it is in contact with the blood on the tubing leg of the tubing set. The arterial pressure can be detected and received in a non-invasive manner, for example, via a non-invasive tubing leg outside the patient or in the circulation support system. This means that the extracorporeal circulation support system can remain compact and complex arrangements can be avoided. For the patient, this also means that the inserted cannula can be smaller in size and the surgery is generally less invasive.

[0042] Preferably provides a trigger signal for a blood pump supported by extracorporeal circulation. In this way, additional and / or supportive blood flow can be provided. Due to the delay time that dynamically adapts to potentially changing patient conditions, blood flow support can be administered at an appropriate time point in the corresponding cardiac cycle phase.

[0043] The delay time can be selected considering the predetermined pulse wave conduction time of the blood pump. That is, depending on the patient's condition and the design of the extracorporeal circulation support, a certain fluid delivery time of the delivered blood pulse may occur. This may occur after the start signal of the blood pump due to the transmission time through the tubing set, the transmission time through the cannula, and the time interval before delivery in the aortic arch finally. The selected delay time can advantageously take this transmission time into account. This can reduce or avoid the delay between the end of the systolic phase or the start of the diastolic phase and the administration of blood flow in the target area. Therefore, the determined delay time can at least partially or completely shorten / reduce the predetermined pulse wave conduction time. Thus, the pulse wave provided by means of the trigger signal will appear at a time point after the start of the systolic phase in the target area, the time point corresponding to the delay time increased by the pulse wave conduction time and coinciding with the start of the diastolic phase.

[0044] For example, for a given tube length, blood pump, and / or pulse parameters, the pulse wave conduction time can be determined from a look-up table or register indicating the corresponding pulse wave conduction time. In addition, if the cardiac measurements include aortic pressure values and, for example, the pressure value is used to determine the systolic duration or the end of the systolic phase, the pulse wave conduction time from the aortic arch to the pressure measurement point (such as the return point on the tubing set) can be advantageously considered.

[0045] In this regard, the received aortic pressure can potentially be used as a verification of the selected delay time. The measured aortic pressure can provide feedback for the extracorporeal circulation support and the provided trigger signal. The measured aortic pressure can provide a feedback signal for the delay time and the pulse wave conduction time, which can be automatically considered when determining the delay time. Therefore, the determination of the delay time can be further improved and, if necessary, optimized in an iterative manner.

[0046] The trigger signal preferably provides or defines the pulse duration of the blood pump. Advantageously, the duration of the cardiac cycle and the delay time determined from cardiac measurements are used to define the pulse duration. The pulse duration can be controlled accordingly to optimize or maximize the pulse dose. However, the pressure increase caused by the pulse should be completed at the start of the consecutive systolic phase to prevent a time crossover or overlap of the pressure increase controlled by the pulse and the systolic duration. Thus, the pulse duration is time-limited. Advantageously, the maximum pulse duration can be determined by the difference between the cardiac cycle duration and the determined delay time. The cardiac cycle duration can be determined, for example, by means of the R-R interval. The delay time advantageously corresponds to the QT time of the cardiac cycle, such that the difference ideally corresponds to the duration of the diastolic phase.

[0047] For example, the pulse duration can be determined using the following formula:

[0048] Pulse duration = 60 / heart rate - delay time.

[0049] The heart rate can be determined for the current cardiac cycle and the start of the systolic phase of the immediately preceding cardiac cycle, or it can be output as a moving average of a predetermined number of previous cardiac cycles.

[0050] Thus, the pulse duration can be determined based on a specific heart rate and the QT time specified by said heart rate, which preferably corresponds to the set delay time. Thus, the heart rate and thus the delay time and the pulse duration can advantageously (possibly only) be determined based on the EKG signal. For the delay time and the pulse duration, the QT time corresponding to the heart rate can be quasi-automatically taken into account, and an overlap of the delivered trigger signal and the systolic phase can be maximally avoided in a simple but safe manner.

[0051] In order to be able to perform a curative treatment on the patient, the patient's pulse rate, cardiac output, and the reduced cardiac output of the damaged heart preferably complement each other to reach an optimum value. Thus, the cardiac measurements can include the pressure corresponding to the patient's aortic pressure. The trigger signal preferably specifies the pulse height, which can be defined using the pressure value. With the set pulse height and pulse duration, an additional pulse volume can thus be provided, which advantageously increases the total pressure in the aortic region during the diastolic phase of the cardiac cycle. The optimum value of the pulse height can be determined by means of (preferably non-invasive) measurements of the cardiac output with and without extracorporeal circulation support. In addition, the pulse height can be readjusted, for example, by the received aortic pressure value, preferably iteratively, in order to continuously or periodically determine the optimum pulse height according to the corresponding current cardiac output.

[0052] According to the present invention, due to blood flow, improved blood perfusion of the myocardium and end organs can be ensured. The blood pump and pulse parameters can be further or even fully adapted to the patient's intrinsic heart rhythm. In particular, diastolic augmentation can be achieved without excessive increase in afterload, i.e., advantageously keeping the afterload as low as possible.

[0053] The problem of the present invention is also solved by a device for controlling extracorporeal circulation support of a patient. The device includes an interface for receiving cardiac measurements of the supported patient and an evaluation unit configured to determine the start of the systolic phase of the patient's current cardiac cycle based on the cardiac measurements. The device is configured to provide a trigger signal with a delay time for the current cardiac cycle after the determined start of the systolic phase of the extracorporeal circulation support. According to the present invention, the evaluation unit is configured to determine cardiac activity indicating the systolic duration based on cardiac measurements of at least one previous cardiac cycle and to adjust the delay time based on the cardiac activity.

[0054] The device can, for example, control or regulate one or more pump drivers or pump heads of a (particularly non-occlusive) blood pump present in an extracorporeal circulation support system and can be fluidly connected to additional modules. For example, the blood pump can be fluidly connected to an oxygenator or membrane ventilator provided in the extracorporeal circulation support system. In this way, oxygenation of the blood and CO2 depletion can occur. The fluid connection can be established, for example, by means of a venous cannula with a venous access and by means of an arterial cannula with an arterial access for aspirating and delivering blood accordingly. This provides blood flow from the low-pressure side to the high-pressure side. Thus, extracorporeal oxygenation of the blood and improved oxygen supply to the patient can be achieved with the blood pump. Since the quasi-automatic dynamic delay time can be adapted to the respective patient condition, oxygen-rich blood can be administered at the optimal time point. Additionally, additional blood flow during the systolic phase can be avoided.

[0055] Preferably, the interface is configured to receive an EKG signal and / or a pressure value indicating aortic pressure from the patient as cardiac measurements. In this way, measurements indicating cardiac activity can be easily and unambiguously determined. For example, as described above, the R wave and T wave or their ends from the QRS complex can be determined from the EKG to define the start and end of the systolic phase or the offset or the corresponding QT time. Similarly, the pressure value can be used to determine at least one dicrotic point, which is characteristic of or caused by the closure of the aortic valve. Thus, the time point of the start of diastole can be clearly defined.

[0056] The device can also be adapted to perform the above preferred method steps.

[0057] Furthermore, a circulatory support device is proposed, which includes a device according to the present invention as described above.

[0058] The interface can be designed, for example, as a sensor cartridge which can be connected via a connector to various sensors, such as a pressure sensor integrated in a tube system, and to an EKG device. Thus, in addition to the interface and the evaluation unit, the circulatory support device can also include an EKG device communicatively connected to the interface. Thus, the circulatory support device can be used completely independently functionally, in particular without the need to provide additional components. The EKG device can also be attached to the control device, thus allowing a compact arrangement. Preferably, the EKG device is implemented, for example, in the form of an EKG card or an EKG module in the sensor cartridge.

[0059] One or more components of the circulatory support device can also be integrated in a (for example single) housing. The control device can be implemented, for example, in the form of a console which has a user interface for inputting and reading out the settings of the system, in particular the parameters of the blood pump and / or the trigger signals to be provided or already provided. For example, the console can include a touch screen and / or a display with a keyboard for user operation. The control device operates, actuates, controls, regulates and monitors the blood pump such that the blood pump can be synchronized with the corresponding cardiac cycle of the patient.

[0060] For example, the received EKG signals and the heart rate can be recorded, and the display graphically displays the current EKG signal and numerically displays the current or average heart rate. In addition, the characteristic properties of the EKG signal can be emphasized or marked in the graphical display such that, for example, in the QRS signal, the R wave recorded for providing the trigger signal and the QT time related to the delay time can be highlighted in the EKG signal. In addition, other settings, such as the time point of the output trigger signal and the pulse duration in the EKG signal, can be displayed such that the user can monitor the control and regulation of the blood pump according to the physiological state, in particular the systolic and diastolic phases of the patient. Description of the Drawings

[0061] Further preferred embodiments of the invention will be explained in more detail by the following description of the drawings.

[0062] Figure 1 A schematic diagram showing typical ideal cardiac signals in the form of EKG signals and aortic pressure measurements;

[0063] Figure 2 A schematic diagram showing various parameters to be considered when providing a trigger signal;

[0064] Figure 3 Shows according to Figure 1 a schematic diagram of a cardiac signal, wherein a set fixed delay time is provided for different heart rates; and

[0065] Figure 4The figure schematically shows a triggering signal provided for a blood pump according to the present invention in accordance with a preferred embodiment. Detailed Description of the Preferred Embodiment

[0066] Hereinafter, the preferred embodiment will be explained in more detail with reference to the accompanying drawings. In the drawings, corresponding, similar or analogous elements are denoted by the same reference numerals, and in order to avoid repetition, their repeated description may be omitted at least in part.

[0067] According to Figure 1 , a curve of cardiac measurement values 10 over a predetermined time period in consecutive cardiac cycles is schematically shown. The cardiac measurement values 10 exist in the form of an EKG signal 12 and in the form of pressure values or measurements of the patient's aortic pressure 14. The values of the EKG signal 12 and the aortic pressure 14 can be received, for example, by means of an interface of an extracorporeal circulation support device and subsequently evaluated by an evaluation unit.

[0068] The curve shown represents an idealized progression or process in order to depict a standardized sequence of cardiac cycle phases or a plurality of phases. Thus, the QRS complex can be determined after the P wave in the EKG signal 12, the complex including the R wave, which is characteristic of the beginning 16 of systole and can be clearly detected. The subsequent end 18 of systole or the subsequent beginning 18 of diastole then follows the end of the T wave, which corresponds to the closure of the aortic valve.

[0069] The bottom pressure curve of the aortic pressure 14 further shows the beginning 16 of systole when the aortic valve opens, which can be detected as an increase in pressure after receiving a low pressure value. After a decreased pressure value but at a higher absolute pressure, a small increase in pressure indicates the end 18 of systole or the beginning 18 of diastole. This increase in pressure and the subsequent further decrease in the already decreased pressure curve are also referred to as the dicrotic notch or "dicrotic incisure" and can generally be clearly detected in the pressure curve. Thus, the values of the EKG signal 12 and the aortic pressure 14 can be used to determine various cardiac activities, which are at least characteristic of the systolic duration.

[0070] The determined cardiac activities, such as the end 18 of systole, can be used as a basis for determining the delay time of the triggering signal to be provided. As described above, if possible, additional reverse blood flow in the aortic arch should be avoided during systole to reduce afterload. By detecting the beginning 16 of systole (e.g., as the R wave in the EKG signal 12), and detecting the end 18 of systole (e.g., using the T wave in the EKG signal 12), it is possible to determine the systolic duration 20. For example, the systolic duration 20 of the cardiac cycle can be determined, and when providing the triggering signal for consecutive cardiac cycles, the systolic duration 20 can be taken into account.

[0071] Thus, an optimized delay time for the current cardiac cycle can be determined, which takes into account the cardiac activity of at least one previous cardiac cycle. Thus, extracorporeal circulation support is provided, which enables immediate account to be taken of the changing phases of the cardiac cycle. According to the invention, there is no longer a need to manually adjust a preset delay time.

[0072] Furthermore, alternatively or additionally, the cardiac activity of the current cardiac cycle can even be determined by determining the heart rate-related QT time. For example, such a standardized QT time can be determined according to empirical values and the (possibly adjusted) Framingham formula. In this case, only the heart rate of the current cardiac cycle needs to be determined. By determining the heart rate, for example based on the R-R interval or the P-P interval, which in any case is before the start of diastole 18, the cardiac activity of the current cardiac cycle can also - or only - be algorithmically taken into account for determining the delay time.

[0073] As Figure 2 shown, for the pulse to be provided, not only the delay time 24 but also other factors need to be considered. For example, a generally fixed recording or detection time 22 is provided for acquiring or detecting and determining the start of systole 16, which is used as the starting point for providing a trigger signal. Thus, the determined delay time 24 can be shortened by the acquisition or detection time 22, so that the trigger signal is provided at the desired time.

[0074] Furthermore, providing an additional blood flow pulse to be administered usually requires a certain fluid delivery time to reach the target area, the so-called pulse wave conduction time 26. To ensure that the extracorporeal circulation support optimally uses the diastolic phase, the delay time 24 can take into account the pulse wave conduction time 26 and be shortened accordingly.

[0075] Thus, the trigger signal can be provided accurately or almost accurately at the start of diastole, so that the corresponding pulse duration 28 can be optimized without increasing the afterload.

[0076] Figure 3 Schematically shows the effect of a fixed delay time 24 on the afterload at different heart rates (A, B, C). As Figure 1As shown, the cardiac signal 10 in the drawing is also shown as the value of the EKG signal 12 and the aortic pressure 14. As shown, for a given heart rate, for example 120 heartbeats per minute, a fixed delay time 24 allows a trigger signal to be provided during diastole, as shown in section B. The delay time can be optimized based on the QT interval or heart rate, for example using the "Framingham formula" described above, and can thus be, for example, approximately 300 ms, or in the range of 270 to 330 ms. However, if the patient's condition changes, for example the heart rate drops to, for example, 90 beats per minute, the trigger signal will be provided during the systolic phase of the current cardiac cycle, as shown in section A. Conversely, if the heart rate increases to, for example, 150 beats per minute, as shown in section C, the additional pulses applied will occur during the systolic phase of consecutive cardiac cycles. Neither of these situations is desirable.

[0077] Therefore, an adjustment of the delay time can be provided, where, in the case of a lower heart rate, the delay time can be increased by a value in the range of, for example, 10 to 60 ms, or, for example, increased by approximately 30 ms from 300 ms (or another value in the range of, for example, 270 to 330 ms), for example increased to 310 to 360 ms (in the case of an initial value of 300 ms). When the heart rate increases, the delay time can be correspondingly decreased, for example decreased by a value in the range of 10 to 60 ms, or, for example, decreased by approximately 15 ms, for example decreased to 285 ms in the case of a 15 ms decrease when the initial value is 300 ms. In this way, the provision of the trigger signal can be advantageously optimized based on cardiac activity (such as heart rate) to prevent extracorporeal circulation support pulses from being delivered during unexpected cardiac cycle phases.

[0078] Therefore, whether the heart rate decreases or increases, a fixed preset delay time 24 will result in the negative impact of increased afterload. The present invention prevents these negative impacts by making the delay time 24 dynamically adapt to cardiac activity, in particular to the patient's heart rate.

[0079] An example of such optimized circulatory support is Figure 4 shown. The aortic pressure 14 at a predetermined time is shown. The aortic pressure 14 provided based on the patient's pulse 30 can be further increased by means of support pulses 32, that is, when the aortic valve has closed and the systolic phase has ended. The additional pulse amount can be optimized based on a specific available pulse duration and the corresponding pulse height.

[0080] To determine the required or tolerable or even possible pulse height, for example, the cardiac output of a damaged heart can be recorded, for example, by means of echocardiography, wherein the cardiac output is preferably measured both with and without the support pulse 32. Advantageously, the pulse level can be adjusted iteratively. The measured aortic pressure 14 can additionally be used as a feedback signal to take into account the effect of the provided pulse on the aortic pressure.

[0081] In applicable cases, all individual features described in the exemplary embodiments can be combined and / or exchanged without departing from the scope of the invention.

[0082] List of reference numerals

[0083] 10 Cardiac measurement

[0084] 12 EKG signal

[0085] 14 Aortic pressure

[0086] 16 Beginning of systole

[0087] 18 End of systole or beginning of diastole

[0088] 20 Systolic duration

[0089] 21 Diastolic duration

[0090] 22 Detection time

[0091] 24 Delay time

[0092] 26 Pulse wave conduction time

[0093] 28 Pulse duration

[0094] 30 Patient pulse

[0095] 32 Support pulse

Claims

1. A method for controlling extracorporeal circulation support for a patient, the method comprising the steps of: - receiving cardiac measurements (10) of the supported patient; - determining the start of systole (16) of the current cardiac cycle of the patient from the cardiac measurements (10); and - providing, after the determined start of systole (16), a trigger signal with a delay time (24) for extracorporeal circulation support for the current cardiac cycle, wherein the delay time (24) is selected based on cardiac activity determined from cardiac measurements (10) of at least one previous cardiac cycle, the cardiac activity indicating the systolic duration (20).

2. The method according to claim 1, wherein For each cardiac cycle, cardiac activity is determined and the delay time (24) is selected.

3. The method according to any one of the preceding claims, wherein, The cardiac activity includes the start of diastole (18) of the corresponding cardiac cycle.

4. The method according to any one of the preceding claims, wherein, The delay time (24) is selected based on the heart rate determined from the cardiac measurements (10).

5. The method according to claim 4, wherein The heart rate is determined for the current cardiac cycle or includes the current cardiac cycle.

6. The method according to any one of the preceding claims, wherein, The cardiac measurements (10) include the patient's EKG signal (12), and the start of systole (16) and cardiac activity are determined based on the EKG signal (12).

7. The method according to claim 6, wherein, The QT time detected from the EKG signal (12) is considered when determining cardiac activity.

8. The method according to claim 7, wherein The QT time is normalized and / or considered based on the heart rate determined from the EKG signal (12).

9. The method according to any one of the preceding claims, wherein, The cardiac measurements (10) include pressure values corresponding to the patient's aortic pressure (14), and wherein cardiac activity is determined based on the pressure values.

10. The method according to claim 9, wherein A dicrotic notch is determined for the corresponding cardiac cycle based on the pressure values, and wherein the systolic duration (20) is determined based on the dicrotic notch.

11. The method according to claim 9 or 10, wherein The start of systole (16) is determined for the corresponding cardiac cycle using the pressure values, and wherein the systolic duration (20) is determined based on the dicrotic notch.

12. The method according to any one of claims 9-11, wherein, The pressure values are measured at the tubing set of the extracorporeal circulation support and / or by means of a cannula located at the level of the patient's aortic arch.

13. The method according to any one of the preceding claims, wherein, The trigger signal is provided to the blood pump of the extracorporeal circulation support.

14. The method according to claim 13, wherein, The delay time (24) is selected based on a predefined pulse wave conduction time (26) of the blood pump.

15. The method according to claim 13 or 14, wherein, The trigger signal specifies the pulse duration (28) of the blood pump, wherein the pulse duration (28) is selected based on the cardiac cycle duration determined from the cardiac measurements (10) and the delay time (24).

16. The method according to claim 15, wherein, The cardiac measurements (10) include pressure values corresponding to the patient's aortic pressure (14), and wherein the trigger signal specifies a pulse height selected based on the pressure values.

17. A device for controlling extracorporeal circulation support for a patient, the device comprising: - an interface for receiving cardiac measurements (10) of the supported patient, and - an evaluation unit configured to be able to determine the start of systole (16) of the current cardiac cycle of the patient from the cardiac measurements (10), wherein the device is configured to provide, after the determined start of systole (16), a trigger signal with a delay time (24) for extracorporeal circulation support for the current cardiac cycle, Wherein, the evaluation unit is configured to determine cardiac activity indicative of a systolic duration (20) from cardiac measurements (10) of at least one previous cardiac cycle, and to adjust the delay time (24) based on the cardiac activity.

18. The device according to claim 17, wherein, The interface is configured to receive an EKG signal (12) and / or a patient pressure indicative of an aortic pressure (14) as cardiac measurements (10).

19. The device according to claim 17 or 18, the device being configured to perform the method according to any one of claims 1-16.

20. A circulatory support device comprising the device according to any one of claims 17-19.

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