Extracorporeal circuit support with cardiac activity-optimized delay time

Abstract

The invention relates to a method for controlling / regulating an extracorporeal circuit support, to corresponding devices for controlling / regulating an extracorporeal circuit support, and to circuit support devices, in particular in order to reduce the afterload on a patient. Correspondingly, a method is described for controlling / regulating an extracorporeal circuit support of a patient, having the steps of: receiving cardiac measurement values (10) of the supported patient; determining a systole beginning (16) for a current cardiac cycle of the patient from the cardiac measurement values (10); and providing a trigger signal for the extracorporeal circuit support for the current cardiac cycle with a delay time (24) after the determined systole beginning (10). According to the invention, the delay time (24) is selected on the basis of a cardiac activity which is determined from the cardiac measurement values (10) of at least one previous cardiac cycle and which characterizes the duration (20) of a systole.

Description

[0001] Extracorporeal circulatory support with cardiac activity-optimized delay time

[0002] Technical area

[0003] The present invention relates to methods for controlling / regulating extracorporeal circulatory support and corresponding devices for controlling / regulating extracorporeal circulatory support and circulatory support devices.

[0004] State of the art

[0005] If the heart's pumping capacity or pumping function fails, cardiogenic shock can occur. A reduction in cardiac output or cardiac output can lead to reduced perfusion or blood flow to end organs such as the brain, kidneys, and the vascular system in general. Acute heart failure can therefore cause acute blood deficiency in the tissues and organs, accompanied by a lack of oxygen, also known as hypoxia, resulting in potential end-organ damage.

[0006] To stabilize the patient's condition, circulatory support systems have been developed that provide mechanical support and can be quickly connected to the circulatory system. They can improve blood flow and perfusion to organs, including the coronary arteries, and prevent a hypoxic state. For example, extracorporeal circulatory support systems are known. These systems withdraw blood from, for example, the right atrium or vena cava through a cannula inserted into the femoral vein and return it to the patient via a membrane ventilator through a perfusion cannula inserted into the femoral artery. The membrane ventilator depletes CO2 and oxygenates the blood. Such systems are also known as "extracorporeal membrane oxygenation" (ECMO).

[0007] Although this improves organ perfusion, perfusion, or the return of blood, occurs continuously during both the systolic and diastolic phases. This arrangement results in retrograde blood flow, which is directed against the heart's actual ejection direction and thus undesirably increases the afterload. As a result, blood collects in the left ventricle and is no longer ejected. The left ventricle is unnaturally stretched. This hinders the heart's ejection and prevents it from emptying sufficiently. At the same time, the heart must perform more muscular work and therefore requires an increased oxygen supply. This finding is particularly disadvantageous in the case of a heart already damaged by a myocardial infarction.Under such circumstances, the perfusion and microcirculation of the heart, organs and brain is reduced with a continuous blood flow, since human circulation or perfusion is based on the pulsatility of the heart.

[0008] To reduce afterload, systems have been developed in which a pump is inserted into the left ventricle to prevent over-expansion of the left ventricle. Another approach involves inserting a balloon into the aortic region. The balloon is controlled so that it is rapidly inflated based on an ECG signal, for example with helium, to improve blood flow to the heart muscle tissue during a phase of the cardiac cycle. Such systems are known as "intra-aortic balloon counterpulsation" (IABP). However, the effectiveness of such systems is limited because they only pump blood into the coronary vessels that is not sufficiently oxygenated. Furthermore, such (possibly additional) procedures significantly increase the invasiveness of the treatment.

[0009] To reduce afterload, circulatory support systems can be synchronized with the patient's heartbeat as an alternative to continuous blood recirculation. For example, the pump is triggered with a delay based on a detected R-wave in the ECG signal. The delay is manually set to a predefined value. The complexity and dynamics of the patient's own cardiac output require fine-tuning of the extracorporeal support.

[0010] Accordingly, there is a need for approaches that allow reducing the afterload during extracorporeal circulatory support.

[0011] Description of the invention

[0012] According to the invention, it was recognized that provided circulatory support with a predetermined delay time for the trigger signal to be provided can lead to, for example, a pulse from a blood pump not being delivered during the intended phase of the cardiac cycle. Blood flow through the heart's coronary arteries, which normally supply the heart muscle with sufficient oxygen, generally occurs in the diastole of the cardiac cycle. Appropriate emptying of the left ventricle is required in this case. If the filling pressure in the left ventricle is as low as possible at the end of systole or at the beginning of diastole, the coronary arteries can dilate their lumen as much as possible. In this way, the blood flow rate and the oxygen supply are increased. If patient conditions change, i.e. the current patient condition orHowever, due to the patient's vital signs, perfusion may be inadvertently delivered during systole. The delivered blood flow could then, for example, close the aortic valves and further increase pressure in the left ventricle, especially if blood cannot escape. This increased pressure can trigger a further reduction in coronary artery perfusion, thus counteracting the therapy.

[0013] The invention further recognized that faulty timing of the provided blood flow due to a fixed, preset delay time occurs particularly at different heart rates. This approach does not allow for changes in the respective cardiac cycle phases to be taken into account. Therefore, timing that takes into account the specific and current conditions of the cardiac cycle phases is not possible.

[0014] Based on the known prior art, it is therefore an object of the present invention to further improve the circulatory support to be provided and, in particular, to optimize the timing of the trigger signal to be provided, even under changing patient conditions.

[0015] The problem is solved by the subject matter of the independent claims. Advantageous further developments emerge from the subclaims, the description, and the figures.

[0016] Accordingly, a method for controlling / regulating extracorporeal circulatory support of a patient is proposed, comprising the steps:

[0017] Receiving cardiac measurements from the assisted patient;

[0018] Determining a systole start for a current cardiac cycle of the patient from the cardiac measurements; and

[0019] Providing a trigger signal for extracorporeal circulatory support for the current cardiac cycle with a delay time after the determined onset of systole.

[0020] According to the invention, the delay time is selected on the basis of a cardiac activity which is determined from the cardiac measured values ​​of at least one previous cardiac cycle and is indicative of a systole duration.

[0021] Accordingly, the delay time for the current cardiac cycle can be adapted to cardiac activity. A dynamically configured delay time allows the provision of the trigger signal to be adapted to current changes in patient conditions. In this way, perfusion of the coronary arteries can be prevented from occurring unintentionally during systole. This is all the more true as cardiac activity characterizes the duration of systole and is therefore taken into account when providing the trigger signal by means of the appropriately adjusted delay time. Thus, according to the invention, unlike with a fixed, preset delay time, afterload can be largely avoided or at least significantly reduced, while simultaneously ensuring improved perfusion of the end organs, and in particular of the cardiac coronary arteries.Cardiac activity can be determined for the immediately preceding cardiac cycle or for several previous cardiac cycles. However, it is preferably determined for a period before the onset of systole in the current cardiac cycle, so that the provision of the trigger signal is not compromised.

[0022] Cardiac measurements are preferably recorded and received continuously during extracorporeal circulatory support to obtain high-resolution measurements and facilitate the determination of the onset of systole and cardiac activity. The measurements can, for example, be received for a predetermined period of time corresponding to a therapeutic procedure or a segment of the therapeutic procedure.

[0023] Determining the onset of systole and the related delay time has the advantage that a unique cardiac cycle phase can be determined for each cardiac cycle, so that the trigger signal can be provided with a high temporal stability.

[0024] Preferably, the cardiac activity is determined for each cardiac cycle, and the delay time is selected on a cardiac cycle-specific basis. In this way, the delay time can be adjusted virtually in real time. The delay time is advantageously also optimized for the current cardiac cycle or the trigger signal to be output. In this case, for the current cardiac cycle, typically only the cardiac activity of the immediately preceding cardiac cycle can be taken into account, for example, to account for rapid changes in cardiac activity. Alternatively, however, the cardiac activity of a predetermined number of previous cardiac cycles can also be taken into account to adjust the delay time. Accordingly, for example, a (moving) average of the cardiac activity, for example for the last two, three, four, or five to ten cardiac cycles, can be taken into account.This has the advantage, for example, that individual outliers among the previous cardiac cycles are given less weight. The selected delay time is also less influenced by any measurement fluctuations that may occur.

[0025] As explained above, by making cardiac activity indicative of the systole duration and taking this into account when selecting or adjusting the delay time for the current cardiac cycle, it is possible to prevent the trigger signal from being provided during systole of the current cardiac cycle. Preferably, the cardiac activity comprises at least the beginning of diastole of the respective cardiac cycle. For example, the cardiac activity may comprise or determine the closing of the aortic valves, which occurs at the end of the systolic phase or at the beginning of diastole and indicates a filling phase of the heart. In this way, a trigger signal with the appropriate delay time can be provided for the current cardiac cycle with increased probability, such that, for example, a pulse falls during the diastole of the cardiac cycle or does not fall during the time period during which the heart valves are open.

[0026] Advantageously, the delay time can be selected based on a heart rate determined from the cardiac measurements. Accordingly, changes in heart rate and associated changes in the respective cardiac cycle phases can be considered as dynamically changing patient conditions when adjusting or setting the delay time. This allows the delay time for providing the trigger signal in the intended cardiac cycle phase to be determined or selected even more precisely.

[0027] Preferably, the heart rate is determined for the current cardiac cycle or the heart rate encompasses the current cardiac cycle. For example, the determined start of systole of the current cardiac cycle can serve as the basis for the determined heart rate. This allows the delay time to also take into account any fluctuations in the heart rate in the current cardiac cycle phase. For example, the heart rate can be determined using the determined start of systole for only the current cardiac cycle and the immediately preceding cardiac cycle. This allows the heart rate to be set with a high degree of accuracy, based on the current patient condition or a corresponding trend. Alternatively, the heart rate can also be determined for a predetermined number of cardiac cycles, for example, for the last five starts of systole. This allows minor and / or negligible fluctuations in the heart rate to be compensated.Given a given heart rate stability, corresponding trigger stability can be ensured.

[0028] The cardiac measurements preferably comprise the patient's ECG signals, with the onset of systole and cardiac activity being determined using ECG signals. Based on the ECG signals, corresponding characteristic amplitudes can be determined, for example, for different cardiac cycle phases. For example, an R-wave or R-wave characteristic of the beginning of the systolic phase of the cardiac cycle is generally easily distinguishable from other phases of the cardiac cycle, for example, in a QRS complex. The R-wave, with an appropriate delay time, can therefore be used by means of the trigger signal to control extracorporeal circulatory support, for example, to control a blood pump in a successive diastolic phase. The characteristic amplitude changes also enable the systole duration to be determined with high accuracy, so that the delay time for providing the trigger signal can be suitably adjusted.Accordingly, when determining cardiac activity, a QT interval recorded from ECG signals is preferentially considered. The QT interval corresponds to the period of the cardiac cycle from the beginning of the Q wave of the QRS complex to the end of the successive T wave. The time of the end of the T wave physiologically corresponds to the closure of the aortic valves and thus marks the end of systole or the beginning of diastole.

[0029] Taking the QT interval into account proves to be an advantage because it corresponds approximately to the duration of diastole and the delay time can thus be adjusted even more precisely to the desired time of delivery of the trigger signal in the respective cardiac cycle phase.

[0030] Preferably, the QT interval is standardized and / or considered using a heart rate determined from the ECG signals. Thus, the QT interval typically depends on the patient's heart rate. It is therefore to be expected that a change in the QT interval will be accompanied by a change in the heart rate. Conversely, a heart rate-optimized delay time can be determined particularly advantageously in this way. A standardized QT interval can be expected for corresponding heart rates. For example, a delay time can be selected using the "Framingham formula" to represent the heart rate-based QT interval. In this way, a (theoretical) delay time for the current cardiac cycle can be calculated using standardized values ​​and the current heart rate. Such standardized values ​​can be based on empirical values ​​and, for example, can be specified based on previous data sets that were previously evaluated and validated offline.The delay time can be calculated, for example, using the following variant of the Framingham formula:.

[0031] Delay time = 380 - 154 x (1 - 60 / heart rate)

[0032] The heart rate is preferably determined by backing up the systole start of each cardiac cycle, for example, using a time interval between two R waves of successive cardiac cycles, a so-called RR interval. In this way, the heart rate of the current cardiac cycle can also be taken into account. The delay time can thus be determined and optimized for each cardiac cycle. It is corrected almost automatically if the heart rate changes. Should the systolic phase shorten, for example, due to an increase in heart rate, the delay time can be adjusted accordingly. This is because the heart rate allows a corresponding shortening of the QT interval to be taken into account when determining the delay time. The trigger signal can therefore be delivered with increased probability at a time that does not fall within the systolic phase.A residual load can therefore be reduced or even largely avoided.

[0033] In other words, the delay time can advantageously be selected or determined based on a specific heart rate, wherein (if necessary exclusively) a value for the QT time, which is decisive for the delay time, is determined or taken into account based on the heart rate.

[0034] The cardiac measurements can include pressure values ​​corresponding to the patient's aortic pressure. Cardiac activity can be determined using the pressure values. For example, the duration of systole can be determined using a corresponding pressure amplitude or a pressure increase and decrease. The time of the pressure increase can also be used as a measure of the time of the onset of systole. Aortic pressure can be received in addition to ECG signals. Redundancy of the contained data or information can serve and be helpful, for example, in improving the safety of extracorporeal circulatory support. This applies, for example, if cardiac measurements are missing for a particular, particularly the current, cardiac cycle.

[0035] Such redundancy also allows for monitoring of cardiac measured values. This is done, for example, by determining the time of the onset of systole using both the ECG signal, for example by detecting an R-wave, and the pressure increase, and comparing the respective times. The times can be averaged if the deviation is small. However, if a deviation or the difference between the determined times exceeds a predetermined threshold, a specific cardiac measured value can be selected if necessary. This applies, for example, if fluctuations or interference signals occur for the other or additional cardiac measured value. A (possibly additional) threshold can also be provided, which, if exceeded, can trigger a warning signal.

[0036] Accordingly, the accuracy of the timing of the trigger signal to be provided, for example, to control a blood pump, can be further improved by combining the ECG signal with the measured aortic pressure. In this way, any ECG disturbances can no longer compromise patient safety and the functionality of extracorporeal circulatory support.

[0037] Preferably, a dicrotic point for the respective cardiac cycle is determined using the pressure values, and the systole duration is determined based on the dicrotic point. The pressure values ​​can also be used to determine the onset of systole for a respective cardiac cycle, and the systole duration (based on the dicrotic point) can be displayed. For example, a brief increase in aortic pressure following a previous drop in aortic pressure can indicate the closure of the aortic valves and thus the end of systole and the corresponding onset of diastole, or the filling phase of the heart. Such a pressure change can be detected, for example, in a pressure curve as a dicrotic point, also referred to as a "dicrotic notch." The onset of systole can also be determined in light of a pressure curve.This mode is enabled, for example, when a pressure increase is detected that exceeds a predefined threshold and / or is detected after a predefined pressure drop. Additionally, the end of a T wave can be determined from an ECG signal, which physiologically also corresponds to the closure of the aortic valves. The systole duration can then be determined with a certain degree of safety redundancy.

[0038] The delay time can therefore be determined using the pressure values ​​corresponding to the patient's aortic pressure. It can preferably be selected such that the trigger signal is provided after the dicrotic point, or a pulse of extracorporeal circulatory support is delivered after the dicrotic point. A pulse should ideally be completed before the pressure curve begins to rise again.

[0039] For example, the delay can be selected so that a pump signal is emitted when a brief increase in pressure occurs in the aorta, marking the moment of aortic valve closure and thus the beginning of diastole. By activating the motor or pump drive and the rotor blade and triggering the pulse at this time, a (pulsatile) blood flow can be delivered, for example, via an arterial cannula into the area (directly) downstream of the left ventricle and into the aorta. The positioning and countercurrent orientation of the cannula tip ultimately result in increased pulsatile blood flow in the coronary arteries. This provides a correspondingly improved perfusion of the myocardial tissue without, however, impairing the systemic circulation.

[0040] Because the additional blood flow only occurs after the aortic valves close and is preferably terminated before the onset of a successive systolic phase, a reduction in afterload and, at the same time, even a diastolic augmentation is possible with sufficient perfusion of the end organs.

[0041] The pressure values ​​can be measured, for example, on the extracorporeal circulatory support tube set and / or using a cannula at the level of the patient's aortic arch.

[0042] For example, arterial pressure can be received via an interface that is communicatively connected to at least one pressure sensor. The pressure measurement preferably takes place before a blood pump, after a blood pump, and / or after an oxygenator or membrane ventilator provided in the extracorporeal circulatory system and connected to the blood pump. The pressure measurement of the arterial pressure of the assisted patient can be performed invasively in the patient, for example at the cannula tip of an arterial cannula, for example in the patient's aorta, or using another pressure measuring probe that can be positioned at a suitable location in the aorta, or in the femoral artery and / or hiacal artery or radial artery. In this way, potential interference resulting from the pulse wave transit time through the cannula and tubing set can be eliminated.

[0043] Pressure can be measured using non-invasive pressure sensors (without direct blood contact) or using invasive pressure measurement with blood contact at the tubing limbs of the tubing set. Arterial pressure can be recorded and received non-invasively, for example, by recording the arterial pressure via non-invasive tubing limbs or in the circulatory support system outside the patient. This allows the extracorporeal circulatory support system to be kept compact and avoids complex assembly. For the patient, this also means that inserted cannulas can be smaller and surgical procedures can be performed less invasively.

[0044] The trigger signal is preferably provided to a blood pump for extracorporeal circulatory support. This allows additional and / or supportive blood flow to be provided. Due to the delay time, which is dynamically adjusted to any changing patient conditions, blood flow support can be administered at the appropriate time during the respective cardiac cycle phase.

[0045] The delay time can be selected taking into account a predefined pulse wave transit time of the blood pump. Depending on the patient conditions and the design of the extracorporeal circulatory support, a certain fluidic transport time of a delivered blood pulse can occur. This can occur after the start signal for the blood pump, due to the transit time through the tubing set, due to the transit time through the cannula, and finally due to the time interval until delivery in the aortic arch. The selected delay time can advantageously take such a transit time into account. This can reduce or avoid a delay between the end of the systolic phase or the beginning of diastole and the delivery of blood flow in the target area. The determined delay time can thus be shortened / reduced at least partially or completely by the predefined pulse wave transit time.A pulse wave provided by the trigger signal will thus occur in the target range at a time after the onset of systole, which corresponds to the delay time added to the pulse wave transit time and coincides with the onset of diastole.

[0046] The pulse wave transit time can be determined, for example, using a reference directory that lists the corresponding pulse wave transit time for specified tube lengths, blood pumps, and / or pulse parameters. If the cardiac measurements also include aortic pressure values ​​and, for example, the systole duration or end of systole is determined using pressure values, the pulse wave transit time from the aortic arch to the pressure measurement point, for example, a return point on the tubing set, can also be advantageously taken into account.

[0047] In this regard, a received aortic pressure can serve as verification of the selected delay time. The measured aortic pressure can provide feedback for the extracorporeal circulatory support and the provided trigger signal. The measured aortic pressure can provide a feedback signal for the delay time and the pulse transit time, which can be automatically taken into account when determining the delay time. Thus, the determination of the delay time can be further improved and, if necessary, optimized iteratively.

[0048] The trigger signal preferably specifies a pulse duration of the blood pump. The pulse duration is advantageously defined using a cardiac cycle duration determined from the cardiac measured values ​​and the delay time. The pulse duration can be regulated accordingly to optimize or maximize the pulse dose. However, the pressure increase caused by the pulse should be completed at the beginning of successive systole to prevent temporal entanglement or overlap of the pulse-controlled pressure increase and the systole duration. Accordingly, the pulse duration is time-limited. The maximum pulse duration can advantageously be determined from the difference between the cardiac cycle duration and the determined delay time. The cardiac cycle duration can be determined, for example, using an RR interval. The delay time advantageously corresponds to the QT interval of the cardiac cycle, so that the difference ideally corresponds to the duration of the diastolic phase.

[0049] The pulse duration can be determined, for example, using the following formula:

[0050] Pulse duration = 60 / heart rate - delay time

[0051] The heart rate can be determined for the beginning of systole of the current cardiac cycle and the immediately previous cardiac cycle or can be output as a moving average of a given number of previous cardiac cycles.

[0052] The pulse duration can thus be determined based on a specific heart rate and a QT interval determined based on the heart rate, which preferably corresponds to the set delay time. Accordingly, the heart rate, and thus both the delay time and the pulse duration, can advantageously be determined (if necessary exclusively) based on the ECG signals. The QT interval corresponding to the heart rate can be taken into account almost automatically for both the delay time and the pulse duration, thus largely avoiding an overlap of a delivered trigger signal with a systolic phase in a simple yet reliable manner.

[0053] In order to enable curative treatment for the patient, the pulse, the patient's cardiac output and the reduced cardiac output of the damaged heart preferably complement each other to an optimized value. In this way, the cardiac measurements can include pressure values ​​corresponding to the patient's aortic pressure. The trigger signal preferably specifies a pulse height, which can be defined using the pressure values. Using the set pulse height and pulse duration, an additional pulse volume can be provided, which advantageously increases the total pressure in the aortic region in the diastolic phase of the cardiac cycle. The optimal pulse height value can be determined using (preferably non-invasive) measurements of the cardiac output with and without extracorporeal circulatory support. Furthermore, the pulse height can be felt or sensed, e.g. using the received aortic pressure values.adjusted, preferably iteratively, to determine the optimal pulse height continuously or periodically in light of the current cardiac output.

[0054] According to the invention, the blood flow can ensure improved blood flow to both the heart muscle and the end organs. 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 disproportionately increasing the afterload, i.e., advantageously keeping it as low as possible.

[0055] The object underlying the invention is further achieved by a device for controlling / regulating extracorporeal circulatory support of a patient. The device comprises an interface for receiving cardiac measured values ​​of the assisted patient and an evaluation unit configured to determine a systole start for a current cardiac cycle of the patient from the cardiac measured values. The device is configured to provide a trigger signal for the current cardiac cycle with a delay time after the determined systole start for the extracorporeal circulatory support. According to the invention, the evaluation unit is configured to determine cardiac activity, which is characteristic of a systole duration, from the cardiac measured values ​​of at least one previous cardiac cycle and to adjust the delay time based on the cardiac activity.The device can, for example, control or regulate one or more pump drives or pump heads for (particularly non-occlusive) blood pumps present in an extracorporeal circulatory support system and, if necessary, be fluidically connected to other modules. For example, the blood pump can be fluidically connected to an oxygenator or membrane ventilator provided in the extracorporeal circulatory support system. In this way, the oxygen enrichment and CO2 depletion of the blood can occur. The fluidic connection can, for example, be established with a venous access via a venous cannula and an arterial access via an arterial cannula for aspirating or pumping the blood. This provides blood flow from a side with low pressure to a side with higher pressure.Thus, the blood pump enables extracorporeal oxygenation of the blood and improved oxygen supply to the patient. The dynamic delay time, which can be adjusted almost automatically to the patient's specific conditions, allows the oxygen-enriched blood to be administered at the optimal time. It also prevents additional blood flow during a systolic phase.

[0056] Preferably, the interface is configured to receive ECG signals and / or pressure values ​​representative of aortic pressure from the patient as cardiac measurements. In this way, measurements representative of cardiac activity can be determined simply and clearly. For example, an R wave from a QRS complex as well as a T wave or its end can be determined from the ECG in order to define, as described above, a start and end of systole or a corresponding QT interval. Similarly, based on pressure values, at least one dicrotic point, which is representative of or caused by the closure of the aortic valves, can be determined. Thus, the time of the start of diastole can be clearly defined.

[0057] The device may further be configured to carry out the preferred method steps described above.

[0058] Furthermore, a circulatory support device is proposed which comprises the device according to the invention described above.

[0059] The interface can, for example, be designed as a sensor box, which can be connected via ports to various sensors, such as pressure sensors integrated in the hose system, and an ECG device. In addition to the interface and the evaluation unit, the circulatory support device can also have an ECG device that is communicatively connected to the interface. This allows the circulatory support device to be used functionally completely independently, in particular without the need to provide additional components. The ECG device can also be attached to the control / regulation device, thereby enabling a compact arrangement. The ECG device is preferably implemented, for example, in a sensor box in the form of an ECG card or an ECG module.

[0060] One or more components of the circulatory support device can further be integrated into a (e.g., single) housing. The control / regulation device can be implemented, for example, in the form of a console having a user interface for entering and reading system settings, in particular parameters of the blood pump and / or the trigger signal to be provided or provided. For example, the console can comprise a touchscreen and / or a display with a keyboard for user operation. The control / regulation device operates, actuates, controls, regulates, and monitors the blood pump and enables synchronization of the blood pump with the patient's respective cardiac cycle.

[0061] For example, the received ECG signal and the heart rate can be recorded, with the display showing the current ECG signal graphically and the current or averaged heart rate numerically. Furthermore, characteristic properties of the ECG signal can be emphasized or marked in the graphic representation, so that, for example, an R-wave detected in a QRS signal to provide the trigger signal and a QT interval relevant to the delay time can be marked in the ECG signal. Furthermore, other settings, such as the time of the emitted trigger signal and the pulse duration in the ECG signal, can be displayed, allowing a user to monitor the control and regulation of the blood pump with regard to the patient's physiological state and, in particular, the systolic and diastolic phases.

[0062] Short description of the characters

[0063] Preferred further embodiments of the invention are explained in more detail in the following description of the figures. They show:

[0064] Figure 1 shows a schematic representation of ideal-typical cardiac signals in the form of ECG signals and measured values ​​of aortic pressure;

[0065] Figure 2 shows a schematic representation of various parameters to be taken into account for providing the trigger signal;

[0066] Figure 3 is a schematic representation of the cardiac signals according to Figure 1 with a fixed delay time for different heart rates; and

[0067] Figure 4 is a schematic representation of an inventive provision of a trigger signal for a blood pump according to a preferred embodiment. Detailed Description of Preferred Embodiments

[0068] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are provided with identical reference numerals. A repeated description of some of these elements has been omitted to avoid repetition.

[0069] Figure 1 schematically shows a progression of cardiac measured values ​​10 over a predetermined period of time for successive cardiac cycles. The cardiac measured values ​​10 are available in the form of ECG signals 12 and in the form of a pressure value or measured value of a patient's aortic pressure 14. The ECG signals 12 and the aortic pressure values ​​14 can be received, for example, via an interface of an extracorporeal circulatory support device and subsequently evaluated by an evaluation unit.

[0070] The curves shown represent idealized progressions to depict a standardized progression of the cardiac cycle phase(s). Accordingly, a QRS complex can be detected in the ECG signal 12 after a P wave, which includes a clearly detectable R wave that characterizes the beginning of systole 16. The successive end of systole or the subsequent beginning of diastole 18 then follows at the end of the T wave, the end of which corresponds to the closure of the aortic valves.

[0071] The lower pressure curve of the aortic pressure 14 further indicates that the beginning of systole 16, at which the aortic valves open, can be determined as a pressure increase following a received low pressure value. A slight pressure increase after a decreasing pressure value curve, but at a higher absolute pressure, indicates the end of systole or the beginning of diastole 18. Such a pressure increase in the already decreasing pressure curve and the successive further pressure decrease is also known as a dicrotic point or a "dicrotic notch" and is usually clearly detectable in the pressure curve. Accordingly, various cardiac activities, which are characteristic at least for the duration of systole, can be determined based on the ECG signals 12 and the values ​​of the aortic pressure 14.

[0072] The determined cardiac activities, such as the end of systole 16, can serve as the basis for determining a delay time for a trigger signal to be provided. As explained above, additional retrograde blood flow in the aortic arch during systole should be avoided as much as possible to reduce afterload. Detecting the beginning of systole 16, for example, as an R wave in the ECG signal 12, and detecting the end of systole 18, for example, based on the T wave in the ECG signal 12, makes it possible to determine the systole duration 20. For example, a systole duration 20 can be determined for one cardiac cycle, and the systole duration 20 can be taken into account when providing a trigger signal for a successive cardiac cycle.

[0073] In this way, an optimized delay time can be determined for a current cardiac cycle, taking into account the cardiac activity of at least one previous cardiac cycle. This provides extracorporeal circulatory support that can be used to directly account for changing cardiac cycle phases. According to the invention, manual adjustment of a preset delay time is no longer necessary.

[0074] Furthermore, alternatively or additionally, cardiac activity can even be determined for the current cardiac cycle by determining a heart rate-dependent QT interval. Such a standardized QT interval can be determined, for example, based on empirical values ​​and a (possibly adapted) Framingham formula. In this case, only the heart rate for the current cardiac cycle would have to be determined. By determining the heart rate, for example, based on an RR interval or a PP interval, which in any case precede the onset of diastole, the cardiac activity of the current cardiac cycle can also be considered algorithmically—or exclusively—for determining the delay time.

[0075] As shown in Figure 2, not only the delay time 24 but also other factors can be taken into account for a pulse to be delivered. For example, a typically fixed acquisition time 22 is provided for the detection and determination of the onset of systole 16, which serves as the starting point for providing the trigger signal. The determined delay time 24 can therefore be shortened by the acquisition time 22, so that the trigger signal is delivered at the desired time.

[0076] Furthermore, in order to provide an additional blood flow pulse to be administered, a certain fluidic transport time to the target area may generally be required, a so-called pulse wave transit time 26. In order to ensure that a diastolic phase is optimally utilized by the extracorporeal circulatory support, the delay time 24 can take into account the pulse wave transit time 26 and be shortened accordingly.

[0077] In this way, the trigger signal can be provided exactly or almost exactly at the beginning of diastole, so that the corresponding pulse duration 28 can be optimized without increasing the afterload.

[0078] Figure 3 schematically illustrates the influence a fixed delay time 24 can have on the afterload at different heart rates (A, B, C). As in Figure 1, the cardiac signals 10 are also depicted in this figure as ECG signals 12 and aortic pressure values ​​14. It is shown that the fixed delay time 24 for a specific heart rate, for example, 120 beats per minute, enables the provision of a trigger signal within diastole, as shown in section B. A delay time that can be optimized based on the QT interval or the heart rate, for example, using the "Framingham formula" described above, can thus be, for example, approximately 300 ms or in a range from 270 to 330 ms.However, if patient conditions change, for example, if the heart rate decreases, for example, to 90 beats per minute, the trigger signal is delivered during the systole of the current cardiac cycle, as shown in Section A. Conversely, if the heart rate is elevated, for example, to 150 beats per minute, as shown in Section C, the additional pulse delivered occurs during the systolic phase of a subsequent cardiac cycle. Both cases are undesirable.

[0079] Accordingly, an adjustment of the delay time can be provided, whereby at the lower heart rate it can be increased, for example, by a value in the range of 10 to 60 ms or, for example, by approximately 30 ms from 300 ms (or, for example, another value in the range of 270-330 ms), for example to 310 to 360 ms (in the case of an initial value of 300 ms). At the increased heart rate, it can be reduced accordingly, for example by a value in the range of 10 to 60 ms or, for example, by approximately 15 ms, for example to 285 ms in the case of a reduction of an initial value of 300 ms by 15 ms. In this way, the provision of the trigger signal can advantageously be optimized based on cardiac activity such as the heart rate in order to prevent a pulse of extracorporeal circulatory support from being administered in an unintended phase of the cardiac cycle.

[0080] Both in the case of a reduction and an increase in heart rate, the fixed preset delay time 24 results in negative effects that increase the afterload. The present invention prevents these negative effects by dynamically adapting the delay time 24 to the patient's cardiac activity and, in particular, the heart rate.

[0081] An example of such optimized circulatory support is shown in Figure 4. The aortic pressure 14 is plotted for a predetermined time. The aortic pressure 14 provided by a patient pulse 30 can be further increased with the aid of a support pulse 32, specifically when the aortic valves are already closed and the systolic phase has ended. The additional pulse volume can be optimized based on a specific available pulse duration and a corresponding pulse height.

[0082] To determine the required, tolerable, or even possible pulse height, the cardiac output of the damaged heart can be recorded, for example, using an ultrasound examination. The cardiac output is preferably measured both with and without the assist pulse 32. The pulse height can advantageously be adjusted iteratively. The measured aortic pressure 14 can also be used as a feedback signal to account for the influence of the provided pulse on the aortic pressure.

[0083] Where applicable, all individual features presented in the embodiments may be combined and / or exchanged without departing from the scope of the invention.

[0084] List of reference symbols

[0085] 10 cardiac measurements

[0086] 12 ECG signal

[0087] 14 Aortic pressure

[0088] 16 Beginning of systole

[0089] 18 Beginning of diastole

[0090] 20 systole duration

[0091] 21 Diastole duration

[0092] 22 Recording time

[0093] 24 Delay time

[0094] 26 Pulse wave transit time

[0095] 28 pulse duration

[0096] 30 patient pulse

[0097] 32 support pulse

Claims

Claims 1. A method for controlling / regulating extracorporeal circulatory support of a patient, comprising the steps: Receiving cardiac measurements (10) of the assisted patient; Determining a systole start (16) for a current cardiac cycle of the patient from the cardiac measured values ​​(10); and Providing a trigger signal for the extracorporeal circulatory support for the current cardiac cycle with a delay time (24) after the determined systole start (16), wherein the delay time (24) is selected based on a cardiac activity which is determined from the cardiac measured values ​​(10) of at least one previous cardiac cycle and is indicative of a systole duration (20).

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

3. Method according to one of the preceding claims, wherein the cardiac activity comprises the beginning of diastole (18) of the respective cardiac cycle.

4. Method according to one of the preceding claims, wherein the delay time (24) is selected based on a heart rate determined from the cardiac measured values ​​(10).

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

6. Method according to one of the preceding claims, wherein the cardiac measured values ​​(10) comprise ECG signals (12) of the patient and the start of systole (16) and the cardiac activity are determined based on the ECG signals (12).

7. The method according to claim 6, wherein a QT time detected from the ECG signals (12) is taken into account when determining the cardiac activity.

8. The method according to claim 7, wherein the QT time is normalized and / or taken into account based on a heart rate determined from the ECG signals (12). . Method according to one of the preceding claims, wherein the cardiac measured values ​​(10) comprise pressure values ​​corresponding to the patient's aortic pressure (14), and wherein the cardiac activity is determined based on the pressure values.

0. Method according to claim 9, wherein a dicrotic point for the respective cardiac cycle is determined based on the pressure values, and the systole duration (20) is determined based on the dicrotic point.

1. Method according to claim 9 or 10, wherein a systole start (16) for the respective cardiac cycle is determined based on the pressure values, and the systole duration (20) is determined based on the dicrotic point.

2. Method according to one of claims 9 to 11, wherein the pressure values ​​are measured on the tube set of the extracorporeal circulatory support and / or by means of a cannula at the level of the patient's aortic arch. 3.Method according to one of the preceding claims, wherein the trigger signal is provided for a blood pump for extracorporeal circulatory support.

4. Method according to claim 13, wherein the delay time (24) is selected based on a predetermined pulse transit time (26) of the blood pump.

5. Method according to claim 13 or 14, wherein the trigger signal specifies a pulse duration (28) of the blood pump, wherein the pulse duration (28) is selected based on a cardiac cycle duration determined from the cardiac measured values ​​(10) and the delay time (24).

6. Method according to claim 15, wherein the cardiac measured values ​​(10) comprise pressure values ​​corresponding to the aortic pressure (14) of the patient, and wherein the trigger signal specifies a pulse height selected based on the pressure values.Device for controlling / regulating extracorporeal circulatory support of a patient, comprising an interface for receiving cardiac measured values ​​(10) of the supported patient, and an evaluation unit which is configured to determine a systole start (16) for a current cardiac cycle of the patient from the cardiac measured values ​​(10). wherein the device is configured to provide a trigger signal for the current cardiac cycle with a delay time (24) after the determined start of systole (16) for the extracorporeal circulatory support, wherein the evaluation unit is configured to determine cardiac activity, which is indicative of a systole duration (20), from the cardiac measured values ​​(10) of at least one previous cardiac cycle and to adjust the delay time (24) based on the cardiac activity. Device according to claim 17, wherein the interface is configured to receive ECG signals (12) and / or pressure values ​​of the patient, which are indicative of aortic pressure (14), as cardiac measured values ​​(10). Device according to claim 17 or 18, which is configured to carry out the method according to one of claims 1 to 16. Circulatory support device comprising a device according to one of claims 17 to 19.

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