WO2021048337A1

WO2021048337A1 - System and method for communication among multi-chamber leadless pacemaker devices

Info

Publication number: WO2021048337A1
Application number: PCT/EP2020/075450
Authority: WO
Inventors: Ali KHALEGI; Ilangko BALASINGHAM
Original assignee: Oslo Universitetssykehus Hf
Priority date: 2019-09-11
Filing date: 2020-09-11
Publication date: 2021-03-18

Abstract

A system for communication among multi-chamber leadless pacemaker devices, comprises at least two nodes adapted to be implanted in spaced apart locations in the heart of a patient, the nodes comprising an electrode and an electrical switch. The system further comprises a communication hub/master unit comprising an energy source and a transmitter for transmitting energy for communicating data with the at least two nodes, where the electrical switch is adapted to modulate the energy transmitted by the transmitter as modulated backscatter.

Description

System and method for communication among multi-chamber leadless pacemaker devices.

The present invention relates to a medical implant arranged for wireless communication from within the body, and to a system for communication with the implant, as well as to related methods.

Medical implants are used to gather information about the body and to interact with the body in various contexts. For example, capsule endoscopes are used to gather images within the digestive systems as well as to obtain samples or deliver drugs, neural prosthetic systems link the brain with external devices and exchange electrical signals with the brain, pacemakers can be implanted, and various other devices have been proposed that rely on being held within the body or passed through the body. For all of these medical implant devices it provides advantages if there can be wireless communication with other devices outside of the body. This may be for wireless control or programming of the implant, for transmission of data from sensors such as cameras, temperature sensors, blood monitoring sensors and the like, and other things. Intra-body wireless communication is also an advantageous feature for the next generation of implants in which the communication among multiple implant nodes is essential for data collecting from a patient body to deliver targeted and accurate therapy. The wireless communication provides easy connectivity with less side effects compared to using wires. The main difficulty with wireless communication is the power consumption and integration with small implants that hinders the wide usage. This invention suggests a new approach for wireless communication among multiple implant nodes inside body.

Conventional pacemakers are battery-operated devices that regulate the heartbeat in people with abnormal or slow rhythms. A subcutaneous electronic device is inserted in the chest and wires connect the device to the heart and deliver electrical pulses to the heart. The pacemaker technology is a mature technology which is well established in cardiology. The leads are the primary cause of infection in this technology.

Recent technology is based on the leadless standalone device that is inserted into the heart’s chambers that can sense, analyze and pace the heart to regulate the heart beats. This technology is in a clinical study and removes the problems associated with the leads. The device is only applicable to single chamber usage and is useful for a limited number of heart diseases. Using dual-chamber leadless pacemaker or multi-chamber device is essential for an improved heart function and can be used for a larger number of heart diseases. The problem with dual or multi-chamber pacemaker technology is the synchronous operation of the devices that needs communication among the implants. To synchronize the dual or multi-chamber pacemakers, it is required to provide a communication link between the multiple devices, so each device becomes aware of the other devices’ condition for pacing the heart. The communication among multiple devices is the key point of the function.

The communication can be considered using electric signals. The electric signal communication can be conducted using low-frequency signals (in kHz) by implementing the biological conductivity of the tissues for communications (conductive communication or galvanic coupling), or by using radio frequency (RF) signal propagation (RF communications). Both these approaches have their limitations; the primary and significant limitation is the power consumption.

The active transmitter for RF requires RF front-end with power hungry electronics and low efficient DC to RF power conversion. Also, the integration of RF antennas with leadless capsule is quite tricky due to the metallic body of the capsule and low efficiency of the RF antennas in the biological medium. Using conductive communication is more convenient way of transmission, but requires an active transmitter source and in case of modulation of signals with a carrier signal can be power consuming technology. The main feature of conductive communication is easy integration of the transmitter electrodes with the capsule’s casing. The overall effect of using the active transmitter for communication, both RF and conductive methods, is the power consumption and thus reduced lifetime of the implant device which is operated on non-rechargeable battery resources. This causes critical health problems.

In recent years, Human Body Communication (HBC) has shown advantageous low power characteristics making it compatible for both implant and wearable sensors. HBC is a promising low frequency communication that utilizes human tissues as ohmic conduction media. HBC can use the same electrodes used both for sensing and pacing, allowing a size reduction compared to other kind of communications. HBC frequency is generally considered to be in the range between 10MHz and 50MHz. A typical HBC transmitter employs an electrode structure on the surface of the human body to transmit signals.

US8977358 describes an electrode stimulation delivery system which has a control unit and a network of wireless remote electrodes configured for implantation within a plurality of spaced apart locations in the tissue, e.g. myocardium, of a patient. The control unit is configured to be positioned at or subcutaneous to the patient’s skin. The system comprises an antenna configured for delivering RF energy in proximity to the plurality of wireless remote electrodes. A backscatter communication signal is achieved by changing the effective aperture of the metamaterial and biomimetic antenna. Backscatter communication circuit will include power harvesting circuitry for harvesting power from the RF signal, and a sub modulating circuitry from modulating the impedance of the antenna to generate the modulated backscatter signal.

The object of the invention is to provide a system and method for communication among multi-chamber leadless pacemaker devices that overcomes the problems discussed above.

The object of the invention is achieved by means of the features of the patent claims.

In the following description, low frequency means using any signal in the frequency below 50 MHz down to several KHz. Also the term baseband impulse/ pulse signal is used, which use a wideband signal with a spectrum in the range KHz-several MHz (5-10 MHz).

In one embodiment the system for communication among multi-chamber leadless pacemaker devices, comprises at least two nodes adapted to be implanted in spaced apart locations in the heart of a patient, the nodes comprising an electrode and an electrical switch, and a communication hub/master unit comprising an energy source and a transmitter for transmitting energy for communicating data with the at least two nodes. The nodes may comprise two electrodes.

The nodes may comprise a sensor configured to receive a cardiac electrical signal and sense near field events from the cardiac electrical signal, and/or may comprise a pacemaker. The signals from the sensors may then provide the necessary information to controlling the pacemaker.

The communication hub may comprise a receiver for receiving the modulated energy reflected at the nodes. The communication hub comprises a processor. The processor may then, based on the received signals from the sensors, calculate the need for pacing and send a pacing command signal to the pacemakers.

The electrical switch is in this embodiment adapted to modulate the energy transmitted by the transmitter as modulated backscatter. The electrical switch may be adapted to alter the impedance between two electrodes in the node in order to modulate the energy.

The operation principle of the communication system is based on using wave reflections by the impedance change of the medium surrounded by the communication hub and nodes.

The communication hub, that is leadless, senses the impedance change of the medium continuously. The sensing is conducted by transmitting radio frequency/ low frequency signals by the communication hub. The impedance change is caused by the switch at the nodes and is recorded by the communication hub, making the node data available to the master. Therefore, the communication hub can access each node, and thus each pacemaker, receiving the data in real-time or can read the stored data of slave node.

The communication hub may be an active subcutaneous battery powered reader, an active battery powered right ventricle (RV) capsule, or a unit which is integrated with one of the nodes.

In one embodiment the communication hub is configured to separate signals from the nodes by use of multiplexing techniques. Examples of multiplexing techniques that can be used are frequency division multiplexing (FDM), time division multiplexing (TDM) and code division multiplexing (CDM), but other multiplexing techniques are also feasible. For FDM a crystal filter can be used for providing signals having a specific frequency (RF or LF). Each node is assigned a dedicated frequency, and the communication hub can sequentially send the agreed frequency and record the specific capsule’s data, i.e. targeted reading becomes feasible. When using CDM each slave node contains a specific code for backscattering and the data are decoded at the master receiver relating to a specific capsule. Using TDM means that the reader signal is spread inside the body and each node reply in a specific time slot, which is known to the master. The easiest approach is by using the FDM. TDM needs accurate clock synchronization in the network, which will be discussed later in this document.

The communication hub is in one embodiment configured to sequentially send a signal to the nodes and subsequently receive the backscatter energy from the nodes, where the nodes comprises a clock and are configured to synchronize the clock based on the sequential sent signal.

The communication hub can be configured to calculate the signal sequence based on the received sensor signals and time signals. The time signals represent the time of the measured heart events, and may comprise only one point of time. The communication hub can be configured to calculate a pacing signal and transmitting the pacing signal to the nodes for actuation.

At least one of the nodes may comprise a rectifier and a capacitor. At least some of the energy transmitted from the communication hub may then be rectified in the rectifier and stored in the capacitor. This ensures that there is some available energy at the nodes. At least one of the nodes may comprise a capacitor and a signal transmitter, where the signal transmitter uses energy stored in the capacitor for signal transmission.

In one embodiment the transmitter is configured to transmit energy as low frequency signals. The nodes may comprise a threshold detector configured to detect when a signal exceeds a threshold and to transmit sensor signals to the communication hub when the signal exceeds a threshold.

The nodes can in one embodiment comprise a memory unit which is configured to store sensor data comprising characteristics of the heart together with a time signal and to subsequently send the sensor data and the time signal to the communication hub upon receipt of a trigger signal from the communication hub or when the sensor signal exceeds a threshold.

In one configuration, there is also provided a method for communication among multi-chamber leadless pacemaker devices where the multi-chamber leadless pacemaker devices comprise at least two nodes adapted to be implanted in spaced apart locations in the heart of a patient and the nodes comprising an electrode and an electrical switch. The method comprises

- transmitting energy for communicating data with the at least two nodes from a communication hub/master unit,

- modulating the energy transmitted by the transmitter as modulated backscatter by means of the electrical switch and

- receiving the modulated backscattered energy.

The invention will now be described in more detail, and by reference to the accompanying figures.

Figure 1 illustrates an example of Human Body Backscatter Communication using a subcutaneous leadless reader device.

Figure 2 illustrates an example of Human Body Backscatter Communication using an Right Ventricle leadless reader device

Figure 3a and 3b illustrates two different embodiments of nodes for use in a system according to the invention.

Figure 4 illustrates an embodiment comprising a subcutaneous communication hub equipped with electrode antennas having LF/RF transmitter.

Figure 5 illustrates an example of a subcutaneous communication hub

Figure 6 illustrates an example of using a communication hub without subcutaneous device.

Figure 7a and 7b illustrates two examples of a communication hub incorporated in a node and having LF/RF transmitter.

Figure 1 illustrates a possible embodiment of a system 10 for communication among multi-chamber leadless pacemaker devices. The system comprises three nodes 11, 12, 13 adapted to be implanted in spaced apart locations in the heart of a patient. In this embodiment, the nodes are implanted in three of the heart’s chambers; right atrium (RA) 11, left atrium (LA) 12 and right ventricle (RV) 13. The system 10 further comprises a communication hub/master unit 14 which comprises an energy source and a transmitter for transmitting energy for communicating data with the nodes. The communication hub is for example an active subcutaneous battery powered reader (a reader under the chest skin in an appropriate location on top or around the heart).

The communication hub 14 provides energy via RF/electric signals (galvanic coupling) into the medium, ie. into the body towards the heart. The signal energy is used to provide communication among the nodes 11, 12, 13 inside the heart chambers by using backscatter communication instead of using an active transmitter with the other pacemaker nodes in the left or right atriums (LA, RA) and ventricles (LV, RV). These nodes can be called slave nodes. The nodes have less computation and processing or communication capabilities and are instead equipped with the energy resources for pacing/ actuation purpose. The main function of these nodes is pacing of the heart. Some or all of the nodes may have sensing abilities, ie. they comprise at least one sensor, for example for sensing the electrical activity of the heart or other characteristics. This system eliminates the need for active communication in the nodes, still keeping them readable from the distance by the communication hub.

All the nodes 11, 12, 13 comprise in this embodiment an electrode and an electrical switch. The electrode is used for pacing the heart, while the switch is adapted for modulating the energy transmitted by the transmitter as modulated backscatter. The nodes will be described more detailed later in this document.

Figure 2 illustrates an example where the communication hub 24 is an active battery powered Right Ventricle (RV) capsule. The system 20 in this embodiment, further comprises two nodes 21, 22, for example in the form of multiple capsules inserted inside the chambers of the heart 25. A combination of the communication hub of figure 1 and figure 2 is also feasible.

As for the embodiment of figure 1, the communication hub, here the active RV capsule 24, provides energy via RF/electric signals (galvanic coupling) into the medium. The signal energy is used to provide communication among nodes inside the heart chambers by using backscatter communication with the other pacemaker nodes in the left or right atriums (LA, RA) and ventricles (LV, RV). The communication with the nodes may be similar for the embodiments of figure 1 and 2

The nodes 11, 12, 13, 21, 22 comprise a switching mechanism in form of a nanowatt switch that can modulate the reader signal (emitted from the communication hubs) back into the environment where they are arranged. The function of the switch is to alter the impedance between two electrodes of a pacemaker device. A pacemaker comprises an anchor in form of a spring or fins for fixation of the pacemaker device in the correct position, and one electrode is near the anchor. The two electrodes are at both ends of the device. For instance, the anchor in one side and the other floating side can be used as the antenna electrodes. Therefore, the slave nodes use switch system instead of an active transmitter. The power consumption is in this way reduced from tens of mW to several nano-watt range for data transmission. The nodes’ power can be saved, and their battery resources may be used for the other important functions of the device (sensing and pacing) rather than communication. Also, by reading the slave node’s data and transmitting them to the communication hub, the data processing is transferred to the communication hub (subcutaneous or master RV node) and the complex signal processing unit in the capsule can be eliminated. In addition, the slave node’s data are available in one place for more sophisticated control, decision making and processing.

Figure 3a and 3b illustrates two different embodiments of nodes for use in a system according to the invention. The nodes are illustrated as elongated elements comprising a metal casing, but other shapes may be used. The nodes comprise electrode antennas equipped with backscatter switching mechanism. The node in Fig.3a has the electrodes 31 on the surface of a metal casing, while the node in Fig.3b has the electrodes 3 at the tip and surface of the pacemaker. Both designs have a switch 32, 32’ which controls the connection and disconnection of the electrodes. In the connection mode (ON mode) maximum signal from the electrodes is reflected, while minimum signal reflection occurs in the disconnection mode (OFF mode) of the switch. The switch 32, 32’ can then be used to modulate a signal received and reflected at the nodes, thus providing a backscatter signal that can be read by a reader or communication hub.

Figure 4 shows the placement of the communication hub, here a subcutaneous reader/ master device 44 arranged under the skin in the chest. The subcutaneous device 44 is battery powered and is in this embodiment a leadless can that is made from biocompatible material such as titanium.

As in figure 1, the communication hub 44 can provide energy via RF/electric signals (galvanic coupling) into the medium, ie. into the body towards the heart. The signal energy is used to provide communication with and among nodes and/or switch of a pacemaker inside the heart.

Fig.5a and 5b shows an example of a communication hub, for example as the one shown in figure 4, in form of a subcutaneous can with galvanic and RF electrodes. The galvanic electrodes need metal contact with the body (is used in the frequency range in KHz up to 60 MHz) and the RF electrodes uses a spacer between the electrodes and the medium and use the frequency from 60 MHz to 2.5 GHz. The space can be an RF transparent polymer with biocompatible coating.

Figure 6 shows the system without any subcutaneous hub/can device. In this embodiment, the communication hub 64 is arranged in a capsule at the Right Ventricle (RV) and is used as the hub to manage the nodes 61, 62, 63, 65. In this example there are nodes at several places in the heart, one in the Right Atrium (RA) 61, one in the Left Atrium (LA) 62, one in the Left Ventricle (LV) 65 and two in the Right Ventricle 63. The size of the capsule 64 comprising the communication hub is large compared to the other nodes as it has more functionalities such as signal processing, communication, wireless powering and pacing. The communication hub in this implementation mainly uses LF signal for communications. The transmitted signal is distributed inside the heart area and chambers and the backscatter approach described above is used for downloading the slaves’ data. There are two options in this realization.

In option 1, the LF signal is used to wake-up the nodes and the received signal is rectified and saved in a capacitor comprised in the nodes. This means a sequential communication can be used, in which the stored energy is used to communicate the data back to the master node. The backward communication can be a very simple implementation using baseband impulse communication. This means that the capacitors’ energy is sequentially released in the medium to communicate the slave nodes’ data to the master. Pulse position modulation (PPM) can be used in this embodiment which can be called backscatter baseband impulse communication. If the DC component of the transmitted pulse is removed from the pulse spectrum, the baseband impulse will not affect the regular functionality of the heart. The differential impulse signal is a very narrow pulse of width 20-40 nsec with an amplitude of 2-3 volts. This voltage level can be easily achieved by transmitting LF signal from the master node.

In option 2, the LF signal is directly reflected in the medium using a subcarrier frequency, so the RV receiver (communication hub) becomes simple and compact for implementation. The subcarrier frequency shifts the transmitted signal from the communication hub to a new frequency, which makes it possible for the same electrode to be used for both transmission and reception. In this implementation there is no power scavenging circuit at the nodes, and thus no need for energy storage at the nodes.

The (slave) nodes are distributed inside the heart chambers with locations depending on the type of the patient and the planned therapy. The nodes are implanted by using a known available delivery technology, for example by using a catheter. Each slave node can be very thin (in diameter) but needs some length. Preferably the distance between the electrodes is more than 5 mm. The slave nodes mainly are used for pacing (with a command from the master node) and have very little functionality for saving the space and energy. The main function of the slave nodes is to sense the cardiac signals locally and use a threshold level to register the heart electrical signal level and time of such threshold level being exceeded. There may be further functionalities for some of the other slave nodes. The other function of the slave nodes is pacing of the heart muscles by applying a predefined pulse amplitude and width (pulse energy).

The communication hub, such as the subcutaneous reader of figure 4 or the master node in RV in figure 6, is used as a reader device which requires continuous transmission of the RF/ HBC signal for inquiring the events in real time. It is obvious that transmitting a RF/LF signal from the communication hub in a continuous manner depletes the device battery and might cause some health problems due to continuous RF / LF signal exposure. This limits the device longevity.

Therefore, it is essential to save the power of the reader by reading events in the heart in appropriate timing. Such power saving can be achieved by sequential reading of the slave node’s data using pulse modulated transmitter signal from the communication hub.

In one embodiment, for example using a subcutaneous reader, the RF/ LF signal from the reader is transmitted sequentially to deliver some charges to the slave nodes, in addition to communication with them. The slave nodes can for example use a very simple threshold detector circuit for data reception and signal rectification, which enables saving energy in a capacitor as described earlier. The harvested charge/ energy in the capacitor can be used later to send events sensed in the nodes using baseband impulse communications. The received signals from the communication hub can also be used in the slave nodes to synchronize an internal clock or timer function with the master as the reference. In addition, the timing (absolute time with a given accuracy) can be transferred to the slave nodes. In case of any event happening at the nodes, this event can be communicated to the communication hub. The communication can for example be performed by means of baseband impulse radio link.

This approach can also be used if a communication hub in form of a RV master node is used instead of the subcutaneous reader. In fact, the function of the master is wireless power transfer (WPT) to the slave nodes for communication in case of event.

In another embodiment, the backscatter communication is used to interrogate with the slave nodes and the nodes’ data can be read by a subcutaneous reader without active transmitter in the slave nodes. The process is as follows: 1- The subcutaneous reader sends signals sequentially into the heart environment, where the signal is received by the slave nodes to synchronize their clock signal with the communication hub/master. Then the timing of all the slave nodes are set based on the master reference time. All the slave nodes will hold the same time reference.

2- The communication hub sends sequential reading signals and interrogates the registered events in each slave node with the related time of the event. Therefore, the communication hub can log the event offline while knowing the real occurrence time of the event. The events’ occurrence time are used to manage the network for pacing. The processed signal for pacing is prepared in the communication hub and a command signal is transmitted to the node for actuation/pacing.

3- Depending on the registered time period between events, the reader signal activity period can be adjusted to save the energy. If for example, a patient had too many anomalies the reader continues the reading of the slave nodes data more frequently, for example 4 times in each heart beat, but if there is no anomaly during a time period, the reading rate can be limited to once in two heart beats.

Figure 7a and 7b illustrates two different embodiments of communication hubs for use in a system according to the invention, for example the communication hub 64 in the embodiments of figure 6. The communication hub can be used as the source of LF/ RF signal with electrode antennas. The signal will spread in the heart chamber and is used by the nodes to communicate their data back to the communication hub.

Claims

I. System for communication among multi-chamber leadless pacemaker devices, comprising

- at least two nodes adapted to be implanted in spaced apart locations in the heart of a patient, the nodes comprising two electrodes and an electrical switch

- a communication hub/master unit comprising an energy source and a transmitter for transmitting energy for communicating data with the at least two nodes,

- where the electrical switch is adapted to modulate the energy transmitted by the transmitter as modulated backscatter.

2. System according to claim 1, where the communication hub comprises a receiver for receiving the modulated energy reflected at the nodes.

3. System according to claim 1 or 2, where the communication hub is an active subcutaneous battery powered reader.

4. System according to claim 1 or 2, where the communication hub is an active battery powered right ventricle (RV) capsule.

5. System according to claim 4, where the communication hub is integrated with one of the nodes.

6. System according to one of the previous claims, where at least one of the nodes comprises a sensor configured to receive a cardiac electrical signal and sense near field events from the cardiac electrical signal.

7. System according to one of the previous claims, where the electronical switch is adapted to alter the impedance of the medium between two electrodes in the node.

8. System according to one of the previous claims, where the nodes comprise a pacemaker.

9. System according to one of the previous claims, where the communication hub comprises a processor which, based on the received signals from the sensors, calculate the need for pacing and send a pacing command signal to the pacemakers.

10. System according to one of the previous claims, where at least one of the nodes comprises a rectifier and capacitor, where at least some of the energy transmitted from the communication hub is rectified in the rectifier and stored in the capacitor.

I I . System according to one of the previous claims, where at least one of the nodes comprises a capacitor and a signal transmitter, where the signal transmitter uses energy stored in the capacitor for signal transmission.

12. System according to one of the previous claims, where the transmitter is configured to transmit energy as low frequency signals.

13. System according to one of the previous claims, where the communication hub is configured to separate signals from the nodes by use of multiplexing techniques.

14. System according to one of claims 6-13, where the communication hub is configured to sequentially send a signal to the nodes and subsequently receive the backscatter energy from the nodes, where the nodes comprises a clock and are configured to synchronize the clock based on the sequential sent signal.

15. System according to claim 14, where the nodes comprise a threshold detector configured to detect when a signal exceeds a threshold and to transmit sensor signals to the communication hub when the signal exceeds a threshold.

16. System according to claim 14 or 15, where the nodes comprise a memory unit which is configured to store sensor data comprising characteristics of the heart together with a time signal and to subsequently send the sensor data and the time signal to the communication hub upon receipt of a trigger signal from the communication hub or when the sensor signal exceeds a threshold.

17. System according to one of claims 14-16, where the communication hub is configured to calculate the signal sequence based on the received sensor signals and time signals.

18. System according to one of the previous claims, where the communication hub is configured to calculate a pacing command signal and transmitting the pacing command signal to the nodes for actuation.

19. Method for communication among multi-chamber leadless pacemaker devices where the multi-chamber leadless pacemaker devices comprise at least two nodes adapted to be implanted in spaced apart locations in the heart of a patient and the nodes comprising an electrode and an electrical switch. The method comprises

- receiving the modulated backscattered energy.

20. Method according to claim 19, where the transmitted energy is low frequency signal or radio frequency (RF).

21. Method according to claim 19, comprising separating signals from the nodes by using multiplexing techniques.

22. Method according to claim 19, comprising sequentially transmitting a synchronizing signal from the communication hub to the nodes.

23. Method according to claim 22, comprising sensing characteristics of the heart and storing the characteristics data in a memory unit together with a time signal.

24. Method according to claim 23, comprising reading the data from the memory by means of the modulated backscattered energy.

25. Method according to one of claims 19-24, comprising detecting when a signal exceeds a threshold and transmit sensor signals to the communication hub when the signal exceeds a threshold.