Medical product comprising a functional element for the invasive use in a patient's body

Abstract

So as to be able to determine the position of a functional element as precisely as possible during the invasive use of a blood pump in a patient's body without the use of imaging methods, the blood pump is connected to a main sensor which records signals of the patient's heart, which are compared to other electrophysiological heart signals recorded by several sensors distributed on the body surface so as to allow the position of the blood pump to be determined by way of linking.

Claims

1. A method of determining a position of a blood pump in a body of a patient, the method comprising: inserting a blood pump into a heart of a patient, the blood pump having a housing, wherein the housing surrounds a rotor; actuating the rotor; receiving, at a processing unit, a first signal, wherein the first signal represents a rotational speed of the rotor; determining, at the processing unit, based on the first signal, a flow velocity of a periodic blood flow through the blood pump; determining, at the processing unit, a phase angle of the periodic blood flow; detecting, at a main sensor having a constant position relative to the blood pump, a second signal, wherein the second signal is indicative of a cardiac parameter; and determining, from the phase angle of the periodic blood flow and the second signal, the position of the blood pump within the body of the patient.

2. The method of claim 1, further comprising detecting, with the processing unit, a change in the position of the blood pump.

3. The method of claim 2, further comprising generating a third signal when a threshold for the change is exceeded.

4. The method of claim 1, further comprising storing, in a memory unit connected to the processing unit, at least one previously determined position of the blood pump.

5. The method of claim 4, further comprising continuously comparing a currently determined position of the blood pump to the at least one previously determined position of the blood pump stored in the memory unit.

6. The method of claim 5, further comprising determining a difference between the at least one previously determined position of the blood pump and the currently determined position of the blood pump.

7. The method of claim 6, further comprising generating a fourth signal if the difference exceeds an established threshold.

8. The method of claim 1, further comprising monitoring, with the processing unit, the position of the blood pump based on a distance between the main sensor and the blood pump and a position of the main sensor within the body of the patient.

9. The method of claim 1, wherein the second signal is an electrophysiological heart signal.

10. The method of claim 9, further comprising comparing the phase angle of the periodic blood flow to the electrophysiological heart signal.

11. The method of claim 1, wherein the rotational speed of the rotor is determined based on a drive current or a power supplied to the rotor.

12. A blood pump system comprising: a blood pump; a pump housing surrounding a pump rotor, the pump rotor configured to be actuated; a main sensor having a constant position relative to the pump housing; and a processing unit configured to: receive a first signal, wherein the first signal represents a drive current or a power supplied to the pump rotor; receive a second signal, wherein the second signal is indicative of a cardiac parameter; determine from the first signal a phase angle of a periodic blood flow through the pump housing; and compare the phase angle of the periodic blood flow to the second signal to determine a position of the blood pump within a body of a patient.

13. The blood pump system of claim 12, wherein the processing unit is further configured to detect a change in the position of the blood pump.

14. The blood pump system of claim 13, wherein the processing unit is configured to generate a third signal when a threshold for the change is exceeded.

15. The blood pump system of claim 12, further comprising a memory unit connected to the processing unit, wherein the memory unit is configured to store at least one previously determined position of the blood pump.

16. The blood pump system of claim 15, wherein the processing unit is further configured to continuously compare a currently determined position of the blood pump to the at least one previously determined position of the blood pump stored in the memory unit.

17. The blood pump system of claim 16, wherein the processing unit is further configured to determine a difference between the at least one previously determined position of the blood pump and the currently determined position of the blood pump.

18. The blood pump system of claim 17, wherein the processing unit is configured to generate a fourth signal if the difference exceeds an established threshold.

19. The blood pump system of claim 12, wherein the processing unit is further configured to monitor the position of the blood pump based on a distance between the main sensor and the pump housing and a position of the main sensor within the body of the patient.

20. The blood pump system of claim 19, wherein the main sensor is disposed on the pump housing.

21. The blood pump system of claim 20, wherein the main sensor is disposed on a proximal end of the pump housing.

22. The blood pump system of claim 12, wherein the processing unit further comprises a calibration system for detecting and storing reference data.

23. The blood pump system of claim 12, wherein the first signal represents the power supplied to the pump rotor.

24. The blood pump system of claim 12, wherein the second signal is an electrophysiological heart signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described hereafter in an exemplary embodiment and is shown in drawings.

(2) In the drawings:

(3) FIG. 1 is a schematic view of an intra-aortic balloon pump in a blood vessel close to the heart, wherein the balloon takes on the compressed from thereof;

(4) FIG. 2 shows the configuration of FIG. 1 with an expanded balloon;

(5) FIG. 3 is a schematic view of the upper body of a patient with electrodes for recording ECG signals and an intra-aortic balloon pump comprising a main sensor;

(6) FIG. 4 is a schematic view of a blood vessel with a functional element, a main sensor and auxiliary sensors, and a processing unit;

(7) FIG. 5 is a schematic view of an alternative processing unit;

(8) FIG. 6 is a further embodiment of a processing unit;

(9) FIG. 7 shows an alternative embodiment of the medical product according to the invention, comprising a pressure sensor which forms the main sensor;

(10) FIG. 8 shows a further alternative embodiment of the invention for determining the position of a functional element;

(11) FIG. 9 shows an implantable heart pump comprising a rotor as an example of a functional element; and

(12) FIG. 10 shows a medical product comprising a blood pump and a processing unit for position monitoring and an alarm system.

DETAILED DESCRIPTION OF THE INVENTION

(13) FIG. 1 is a schematic view of a portion of a heart with a left atrium 1, a left ventricle 2, from which a blood vessel 3 extends, and heart valves 4, which allow the blood to flow from the left ventricle 2 into the blood vessel.

(14) FIG. 1 shows the state in the systolic phase, in which the balloon pump 5 is present with the balloon being in the compressed state. In this case, the balloon pump 5 forms the functional element, which can be used to support the heart by relieving the left ventricle during acute cardiac insufficiency, coronary heart disease and similar instances. Such an intra-aortic balloon pump can be used both within the scope of coronary bypass surgeries when treating cardiogenic shock and acute myocardial infarction, and with acute myocarditis, cardiomyopathy and acute left heart failure. It is typically advanced into the aorta starting from the femoral artery and is then located with the tip of the pump catheter at the end of the aortic arch. The balloon can typically be filled with a volume of 40 ml helium gas over a length of 20 cm and thus be expanded. The balloon is periodically filled and emptied (compressed) by an external pneumatic system. Because the balloon filling and emptying take place counter to the cardiac activity, the afterload for the left ventricle is decreased during the systole, which results in an increased ejection fraction and decreased myocardial oxygen consumption.

(15) The diastolic filling of the pump balloon, as shown in FIG. 2, displaces an average of 40 ml of blood, whereby the diastolic blood pressure is raised and the organ blood flow, and the coronary blood flow in particular, is improved during this phase.

(16) The key in this connection is to position the functional element as optimally as possible in the aorta relative to the heart valve 4 or the mouth of the blood vessel into the left ventricle.

(17) In this connection, as is shown in FIG. 3, the invention relates to a main sensor 6, which in the example shown is disposed at the tip of the balloon pump, however in any case is disposed in a fixed spatial relationship, for example at a fixed, known distance thereto or directly thereon, and which allows electrophysiological signals of the heart or of a fluid mechanics variable of the ejected blood flow to be detected. The main sensor is, for example, designed as an electrode or antenna, depending on the internal circuitry, or comprises such an element.

(18) In addition, auxiliary sensor 7, 8, 9, 10, 11 are provided, which can be formed by electrodes for ECG measurement applied externally to the patient's body. Alternately, differently placed sensors are also conceivable, for example sensors which, as part of implanted devices, are not disposed on the body surface but in the body interior, but are suitable for recording electrophysiological cardiac signals. Such sensors can, for example, be provided in cardiac pacemakers or implanted defibrillators.

(19) It is also conceivable to provide a lower number of auxiliary sensors, for example one, two, three or four auxiliary sensors, wherein a higher number allows a complex ECG vector to be attained, which allows more precise localization of the main sensor, and thus of the functional element 5, by comparison and linking to the signals from the main sensor 6.

(20) Both the main sensor 6 and the auxiliary sensors record a respective temporal curve of the electrophysiological cardiac signals or other measured variables, so that the position of the main sensor can be determined by comparing and linking the signals from the main sensor to the signals of the remaining auxiliary sensors having various positions.

(21) In addition to the functional element 12, which can be a rotary pump, for example, the corresponding main sensor 6 at the tip of the functional element, and the auxiliary sensors 7, 8, 9, 10, 11, FIG. 4 shows a processing unit 13 in which the signals from all sensors are combined.

(22) In the case of ECG data, the signals from the auxiliary sensors are combined to form a

(23) $\hspace{1em}\left(\begin{array}{c}{m}_1\left(t\right)\\ \mathrm{.Math.}\\ m_5\left(t\right)\end{array}\right)\mathrm{vector},$
while the temporally variable signal from the main sensor 6 is present as a scalar f.sub.1(t). The vector of the signals from the auxiliary sensors is compared to the function f.sub.1(t) so as to perform the position determination of the main sensor 6 in the processing unit 13 using predetermined metrics and to display the result in the display device 14. To this end, either the absolute distance of the functional element 12 from the inlet into the left ventricle, or the spacing along the blood vessel 3 can be shown in the display device.

(24) FIG. 5 shows an alternative embodiment of the processing unit, in which no

(25) $\hspace{1em}\left(\begin{array}{c}{s}_1\left(t\right)\\ \mathrm{.Math.}\\ s_n\left(t\right)\end{array}\right)$
currently detected electrophysiological signals are detected by auxiliary sensors and instead stored data
is used. This data is stored in a memory unit 15 of the processing unit 13′ and was, for example, measured when the treatment of the patient started and was archived, so as to later allow the position of the functional element to be determined by comparing the currently measured signals from the main sensor to typical signals of the patient's heart.

(26) FIG. 6 shows a variant of the invention in which both currently measured electrophysiological heart signals

(27) $\hspace{1em}\left(\begin{array}{c}{m}_1\left(t\right)\\ \mathrm{.Math.}\\ m_5\left(t\right)\end{array}\right)$
and stored ECG data

(28) $\hspace{1em}\left(\begin{array}{c}{s}_1\left(t\right)\\ \mathrm{.Math.}\\ s_n\left(t\right)\end{array}\right)$
are linked to the signals from a main sensor. To this end, as in the example described based on FIG. 4, the signals from the main sensor can be

(29) $\hspace{1em}\left(\begin{array}{c}{f}_1\left(t\right)\\ \mathrm{.Math.}\\ f_n\left(t\right)\end{array}\right)$
recorded via several main sensor elements which are spatially distributed on the functional element 5, so that the main sensor also allows a signal vector to be detected. It is then possible to first compare the currently detected electrophysiological heart signals

(30) $\hspace{1em}\left(\begin{array}{c}{m}_1\left(t\right)\\ \mathrm{.Math.}\\ m_5\left(t\right)\end{array}\right)$
to the stored data

(31) $\hspace{1em}\left(\begin{array}{c}{s}_1\left(t\right)\\ \mathrm{.Math.}\\ s_n\left(t\right)\end{array}\right)$
and link the result of this comparison to the data detected by the main sensor, so as to output position information in the display unit 14 using metrics. To this end, either an absolute distance or a traffic light-type indicator in form of a green light for an allowed distance range, a yellow light for a critical distance range and a red light for a prohibited distance range of the functional element from the ventricle may be provided. As an alternative or in addition, the position may also be graphically represented, for example by a representation relative to the position of the heart or of a reference point, for example of an auxiliary sensor, the position of which can in particular be exactly known. Moreover, the position can also be represented by means of an acoustic signal, for example an alarm signal, which indicates the departure from the intended position or a change in distance from a predetermined location.

(32) FIG. 7 shows an alternative design of a medical product according to the invention, in which a heart, which is shown symbolically and denoted by numeral 16, simultaneously emits electrophysiological signals which are recorded by means of one or more auxiliary sensors 7′, and blood pressure fluctuations are transported via the vascular system due to the periodic pump activity, wherein the fluctuations can be recorded by means of a pressure sensor 6′ at the tip of a functional element 5′, for example a heart pump.

(33) Because the electrophysiological signals are recorded by the sensors 7′ virtually without delay, these convey a current picture of the cardiac activity, which can be compared to the pressure fluctuations arriving at the main sensor 6′ with delay due to the slower migration velocity. It can be determined, or it is known, at what times with regard to a complete cardiac period certain maximal or minimal blood pressure values are generated in the heart, so that, having knowledge of the migration velocity of pressure waves, the distance of the main sensor 6′ from the ventricle can be concluded from the time difference of the recording by the sensors 6′, 7′. Using the configuration shown and a corresponding processing unit 13′″, it is thus possible to determine the position of the main sensor 6′, and thus that of the functional element 5′, relative to the vascular system in relation to the heart and the position can be displayed.

(34) The measurement is typically carried out based on the pressure maximum that is achieved. The measurement by means of the processing unit 13′″ can be calibrated when introducing the functional element 5′, for example by slowly inserting the blood vessel while also determining the position of the functional element 5′ by means of imaging.

(35) FIG. 8 shows a further alternative of the medical product according to the invention, in which a main sensor 6″, which is disposed at the tip of a functional element 5″, interacts with several, notably two, three or four, auxiliary sensors or transceivers 17, 18, 19, 20, for example via magnetic fields, electrical fields or electromagnetic coupling. A corresponding transceiver may also be used as the main sensor 6″, so that it either transmits signals received from the elements 17, 18, 19, 20, or vice versa. The intensity of the coupling of the elements 17, 18, 19, 20 to the respective element 6″ can be used to determine the position thereof relative to the elements 17, 18, 19, 20. For example electrodes, which are already present and which are alternately used for position determination and as ECG electrodes, may be used as transceiver elements 17, 18, 19, 20.

(36) The various coupling intensities are linked in the processing unit 13″″. In this case, it is also possible for several sensor elements to be disposed on the main sensor, for example so as to render the position determination more precise or additionally allow the orientation of the functional element to be determined.

(37) FIG. 9 shows a rotary pump 30 as the functional element by way of example, which is designed to be compressible and expandable for insertion in a ventricle 31. The pump 30 comprises a rotor 32 having a hub 33, which can be driven by means of a drive shaft 34 from outside the patient body. The drive shaft is guided through a hollow catheter 35, which is shown only partially. The pump 30 comprises a compressible pump housing 36, to the proximal end of which a main sensor 37 is attached. The main sensor can be connected to a processing unit disposed outside the body, for example via an electrical conductor located in the lumen or the housing wall of the hollow catheter 35, and notably via the drive shaft.

(38) During operation, the pump takes in blood via the intake cage 38 and ejects the same into the blood vessel 40 via ejection openings 39. A flexible outflow hose 41 is provided, which in cooperation with the heart valve 42, which surrounds the outflow hose, periodically closes the ejection/outflow openings 39 and thus prevents the backflow of blood.

(39) This demonstrates that the position of the pump relative to the heart valve must be precisely adhered to.

(40) If the position of the main sensor 37 can be determined, it is also possible to correctly position the pump 30 in the ventricle.

(41) In a modification, a further sensor 37a is attached to the distal end of the pump housing. In this case, it is possible to determine a corresponding signal, for example an ECG vector, directly between these two sensors and to draw a conclusion therefrom as to the position, or change in position, of the pump. Depending on the accuracy requirements in terms of the position determination, it may be possible in this instance to forego additional, notably external, auxiliary sensors.

(42) An operating property of the blood pump may also be used to implement a main sensor which measures a fluid mechanics variable, for example the blood pressure or the flow velocity of the blood, for example in the case of a rotary pump the current rotational speed can be used if the driving power/torque is known, or a driving torque, driving power, or current/voltage/electrical power of a driving motor of the pump.

(43) The current rotational speed and the electrical power required for driving purposes, which can be determined based on the drive current required by the driving motor, can be used to determine the flow velocity of the blood flow flowing through the pump in a time-resolved manner. When the heart is beating, this results in a periodic pattern, the phase angle of which can be compared to ECG data so as to determine the delay of the fluid mechanics changes from the heart to the main sensor, and thus the distance of the main sensor from the heart.

(44) It is also possible to position two sensors in the same blood vessel, and using travel time measurements which are determined based on the measurement of fluid mechanics variables by each of the sensors, it is possible to determine the distance or a change in the distance of the two sensors. If the position of one of the sensors is fixed and/or known, it is also possible to determine and monitor the absolute position of the other sensor.

(45) FIG. 10 shows a patient body, the heart 43 of whom is supported by means of a blood pump which is placed in the heart valve by means of a catheter 44. A sensor is disposed on the blood pump, and the signals of the sensor are transported by means of a line 45 extending along the catheter 44, notably in the catheter. The signal detection takes place in a signal detection unit 46, which as an alternative or in addition can also receive radio signals and signals from sensors in the outside region of the patient, for example from ECG electrodes. The signal monitoring unit 47 monitors trends of the monitored signals and/or a comparison to reference signals for variances from threshold values and/or instances in which the same are exceeded. If a significant change or variance in the position is found, a signal is emitted to the alarm system 48, which communicates with the outside and optionally can initiate an adjustment of the position of the blood pump. During adjustment, the elimination of the alarm signal may serve as an indication that the desired position has been reached. The processing unit can also comprise a calibration system 49 for detecting and storing reference data when the desirable positioning is carried with methods other than those that are desirable.

(46) The medical product described in this patent application can be used for visualizing the signals of the main sensor 6, 6′, 6″ for optimal positioning during the implantation process, enabling easier and safer placement of the medical product in the circulation. The visualization may take place on a screen of a user's console which is configured to show the position of the medical product within the human or animal body. The screen may be a touch screen configured to display and control the medical product during use. The visualization is very advantageous with regard to control of the medical product's position in the blood circuit. For instance, the position of a rotary blood pump in relation to a heart valve (see, for example, FIG. 9 of the instant patent application) can be easily controlled by medical personnel, and any necessary corrections can be made by repositioning the medical product according to the vectors displayed on the above-mentioned screen.