Nerve cuff stimulation electrode, control device for a vagus nerve stimulation system, and vagus nerve stimulation system

Abstract

A nerve cuff stimulation electrode for cervical VNS is provided and configured to be arranged so as to at least partially surround or enclose one of the vagus nerves. The cuff stimulation electrode has at least two contacts configured to deliver electric stimulation pulses to a vagus nerve. The cuff stimulation electrode further has or may be attached or connected to a tilt sensor, a kinematic sensor, and/or a pulsation sensor configured to generate a signal representative of arterial and venous pressures. The implantable tilt sensor is configured to output a posture signal indicating a patient's posture, thus allowing discrimination between supine and semi-recumbent or erect postures.

Claims

1. A vagus nerve stimulation system comprising: a control device; and a cuff stimulation electrode, the cuff stimulation electrode comprising: an inner cuff surface that faces a nerve; at least two contacts arranged on the inner cuff surface for delivering electrical stimulation; and at least one sensor attached to an outer wall of the cuff stimulation electrode, the at least one sensor including a tilt sensor, a kinematic sensor, and/or a pulsation sensor, wherein the at least one sensor is configured to generate a signal representative of physiological parameters, and wherein the control device records far-field electrogram and wherein the control device determines Congestive Heart Failure status from processing the at least one sensor signal and the far-field electrogram recordings.

2. The cuff stimulation electrode according to claim 1, wherein the tilt and kinematic sensors are implemented using an accelerometer.

3. The cuff stimulation electrode according to claim 1, further comprising at least two additional contacts and associated connections, the additional contacts being attached to the outer wall of the cuff stimulation electrode.

4. The cuff stimulation electrode according to claim 3, wherein the pulsation sensor is based on electrical impedance plethsymography via the additional contacts.

5. The cuff stimulation electrode according to claim 3, further comprising an interface to a control device for a data communication connection from and to the cuff stimulation electrode.

6. The cuff stimulation electrode according to claim 5, wherein the data communication connection is a galvanic connection through a patient's body that comprises a data transceiver, and wherein the additional contacts provide data communication via modulation of an imposed alternating electric field.

7. The cuff stimulation electrode according to claim 3, wherein the at least one sensor and the at least two additional contacts are provided in a common housing attached to the outer wall.

8. The cuff stimulation electrode according to claim 1, wherein the pulsation sensor is a strain gage.

9. The cuff stimulation electrode according to claim 1, wherein the cuff stimulation electrode further comprises or is electrically connectable to a thermoelectric generator that is configured to be placed adjacent to a blood vessel.

10. The cuff stimulation electrode according to claim 1, wherein the control device of the cuff stimulation electrode processes posture signals and pressure signals that are generated by the tilt sensor and the pulsation sensor, respectively, and wherein the control device evaluates the pressure signals based on the posture signal, if the posture signal indicates a predetermined change of an orientation of the tilt sensor.

11. The A cuff stimulation electrode according to claim 10, wherein the control device extracts a heart rate signal from the at least one sensor.

12. The vagus nerve stimulation system according to claim 1, wherein the control device processes posture signals and pressure signals that are generated by the tilt sensor and the pulsation sensor, respectively, and wherein the control device evaluates the pressure signals based on the posture signal, if the posture signal indicates a predetermined change of the orientation of the tilt sensor.

13. The vagus nerve stimulation system according to claim 1, wherein the control device is an implantable pulse generator with an internal power source.

14. The cuff stimulation electrode according to claim 1, wherein the inner cuff surface at least partially surrounds and contacts the nerve.

15. The cuff stimulation electrode according to claim 1, further comprising biocompatible strings attached to the outer wall to enable opening of the cuff stimulation electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is an illustration of an implanted cuff stimulation electrode and control device according to an exemplary embodiment of the invention;

(3) FIG. 2 is a schematic block diagram of the main electronic components (front-end) of the cuff stimulation electrode;

(4) FIG. 3 is an illustration of a cuff stimulation electrode that incorporates the control device and is connected to an implanted Thermoelectric Generator (TEG);

(5) FIG. 4 is a cross-sectional view of the vagus nerve, the Common Carotid Artery (CCA) and the Internal Jugular Vein (IJV) within the carotid sheath in the neck area;

(6) FIG. 5 is an illustration of an exemplary embodiment, wherein the TEG module is placed with its hot plate adjacent to the CCA and its cold plate facing surrounding tissue away from the IJV;

(7) FIG. 6: is an illustration of an IJV and a CCA pressure waveform;

(8) FIG. 7: illustrates a communication scheme with an implantable nerve stimulation system; and

(9) FIG. 8: illustrates a communication scheme with an implantable nerve stimulation system.

DETAILED DESCRIPTION OF THE INVENTION

(10) According to an exemplary embodiment of the invention as shown in FIG. 1, a nerve cuff stimulation electrode 100 is constructed, using a silicone rubber tube 101, with at least two exposed Pt/Ir (or equivalent material) ring contacts 102 in its interior wall in contact with the vagus nerve 103 surface, and a closing structure 104. The cuff stimulation electrode 100 can be self-coiling, or it may include other closing mechanisms, such as a piano hinge with a nylon suture. Biocompatible strings 105 are built on the cuff stimulation electrode 100 outer wall to open it for easy implantation around the nerve 103. Electronic circuitry 106, which may include a pulsation sensor, a triaxial accelerometer, and associated front-end electronic circuitry, is built on the cuff stimulation electrode 100 outer wall and/or associated assembly structures.

(11) In an exemplary embodiment, the ring contacts 102 are replaced by multiple contacts around the nerve 103. Local bipolar stimulation between any two of these contacts may increase effectiveness and selectivity for cardiovascular effects.

(12) The nerve cuff stimulation electrode 100 is connectable to an Implantable Pulse Generator (IPG) 107 located in the patient's chest area via a subcutaneously implanted wire 108. Such wire 108 provides electrical connection to the contacts 102, powers the electronic module 106 built on the cuff stimulation electrode 100, and receives pre-processed pressure and acceleration signals from the vicinity of the cuff stimulation electrode 100. Electronic circuitry in the IPG 107 can drive the ring contacts 102 for delivering low-level electrical stimulation pulses to the nerve 103, i.e. a stimulation level that may not cause a heart rate drop or any other noticeable effect in the patient. Sub-threshold pulses can also be delivered through the ring contacts 102 for impedance measurement to assess potential nerve 103 damage, connective tissue growth, or closing structure 104 failure. The IPG 107 also has the capabilities of recording intrathoracic far-field EGMs 109 between its can and a contact 102, or alternatively using a separate lead with contact(s) 110 closer to the heart. Thus, the IPG 107 acts as a control device for the cuff stimulation electrode 100. It should be noted that the control device may also be another device different from an IPG.

(13) FIG. 2 is a schematic block diagram showing the main electronic components of the nerve cuff stimulation electrode 100. These may include a pulsation sensor 106.2, which utilizes a displacement-sensitive measurement method (e.g. a strain gage), and a triaxial accelerometer 106.3, both connected to the front-end electronic circuitry 106.1. Such circuitry 106.1 may be connected to stimulation contacts 102 and/or to communication contacts 106.4. These contacts 106.4 may serve for galvanic intrabody data communication via modulation of an imposed alternating electric field on the body. They can be part of a data communication interface of the IPG 107. For the purpose of data communication, the IPG 107 may comprise a data transceiver connected to communication contacts 106.4. In an embodiment, the pulsation sensor is based on electrical impedance plethsymography re-utilizing these contacts 106.4 (multiplexed with communication) and the IPG 107 circuitry utilized for nerve 103 impedance measurements.

(14) In an embodiment, the control device is integrated with the electronic circuitry 106 and powered by a Thermoelectric Generator (TEG) module 111 implanted around the External Jugular Vein (EJV) 112 using a Ni-based vein cuff, with the TEG's hot plate in thermal contact with the EJV 112 outer wall and the cold plate facing the surrounding tissue beneath the skin 113, as shown in FIG. 3. A temperature difference of 2 K can be expected between the two plates of the TEG module 111, and such temperature difference can be converted (by Seebeck effect) into electrical energy for powering the embedded electronic circuitry 106. Typically 1.0 V at 5.0 A or 5.0 W can be harvested with this TEG. This is enough power for the particular application given that VNS for CHF is duty cycled with a few pulses delivered every few seconds or cardiac cycles. A typical stimulation pulse may have a rectangular pulse of 1.0 mA with a 200 s width which requires negligible charge consumption compared with the background power consumption required for operation. Most of the power consumption in the present application is required for signal processing from the mentioned sensors.

(15) The circuitry 106 in this case includes the necessary low-power management circuitry for power regulation and continuous operation. Power supply from the TEG module 111 to the control device and electronic circuitry 106 is provided by the power supply wire 114.

(16) FIG. 4 sketches a cross-sectional view of the vagus nerve 103, the Common Carotid Artery (CCA) 200 and the Internal Jugular Vein (IJV) 201 within the carotid sheath 203 in the neck area. As can be seen, the nerve cuff electrode 100 is implanted so its built-in electronic circuitry 106 faces the CCA 200 and IJV 201 for pressure waveform recording. In an embodiment, the nerve cuff electrode 100 may partially or fully wrap at least one of the CCA 200 and IJV 201 for improved pressure waveform recording.

(17) As can be taken from FIG. 5, the TEG module 111 is instead placed with its hot plate adjacent to the CCA 300 and its cold plate facing surrounding tissue away from the blood vessel, for instance the IJV. The TEG module 111 anchoring may be part of the cuff 304, wrapping both the vagus nerve 103 and the CCA 300. As can be seen in FIG. 5, the cuff 304 is implanted so its embedded electronic circuitry 106 faces the CCA 300.

(18) As pointed out above, the signal provided by the pulsation sensor 106.2 is representative of arterial and venous pressures in terms of shape and timing with respect to the cardiac cycle and thus can be considered an indirect pressure signal.

(19) The CCA 200 and IJV 201 pressure waveforms provide relevant information about the patient's heart condition and hence are very useful for the monitoring of CHF status. As shown in FIG. 6, the IJV pressure waveform can be differentiated from the CCA pressure waveform by recording when the triaxial accelerometer indicates a supine and a semi-recumbent or erect position, respectively. The sampled pressure waveform is band-pass filtered to eliminate or minimize respiratory components. In an embodiment, the lower limit of the digital linear phase filter is set to a frequency above the fundamental respiratory rate and below the fundamental heart rate. The upper limit, on the other hand, can be set to reduce electrical noise from the mains. The front-end electronic circuitry 106.1 is configured to filter the pressure signal with a lower cutoff frequency between 0.75 Hz-1.75 Hz and an upper cutoff frequency between 20 Hz-30 Hz. The pressure signal either represents the IJV or CCA pressure based on the patient's position. An exemplary sampling rate can be 200 Hz.

(20) The accelerometer signal provided by the triaxial accelerometer 106.3 is pre-processed by the front-end electronic circuitry 106.1 to determine heart and respiratory signals as follows:

(21) Breathing signal band-pass: 0.10 Hz-0.50 Hz.

(22) Heart rate signal band-pass: 0.50 Hz-3.50 Hz.

(23) Snoring signal band-pass: 3.5 Hz-100.0 Hz.

(24) Also in an embodiment, morphological filters are implemented in the IPG 107 embedded electronic circuitry to track changes in the IJV and CCA pressure waveforms. The parameters of these filters may be adjusted following implantation. Deviations from the original waveforms with time will indicate heart complications that may occur with the progression of the patient's condition. In addition, changes in the Pulse Transit Time (PTT) 303, i.e. the delay between the R-wave detection and the peak of the CCA pressure waveform, can be used to determine arterial stiffness and to perform monitoring of arterial blood pressure. PTT trending analysis can be used to assess disease progression.

(25) The system of the present invention has the signal processing capabilities to identify changes that may occur in the CCA and IJV pressure waveforms and alerting, for example, a Home Monitoring Center via a bedside Patient Messenger.

(26) In an embodiment, the system of the present invention has the signal processing capabilities to identify changes that may occur in the CCA and IJV pressure waveforms and alert, for example, a Home Monitoring Center accordingly either via a skin Patch when applied or by relaying the information to a heart monitor implanted device with wireless communication with the outside world.

(27) As mentioned above, the triaxial accelerometer 106.3 signal can also be filtered in different ways to extract heart, breathing and snoring signals, which are key elements for the diagnosis of OSA. It can also be used to extract sleeping angle patterns. A decrease in the patient's sleeping angle will indicate an improvement of the patient's condition, as patients with CHF tend to sleep with several pillows due to breathing difficulties associated with the disease. Furthermore, the accelerometer can be used to determine the Reflected Wave Transit Time (RWTT) of the CCA pulse wave, which is the temporal difference between the incident and reflected wave at the same position. It has been shown in vivo that the RWTT has high correlation with systolic blood pressure, and hence it can be used as an estimator.

(28) Going to FIG. 7, the IPG 107 can be wirelessly programmed by an external Programmer 400 via a MICS-band link 401 (or equivalent). The IPG 107 can also communicate with a bedside Patient Messenger 402 via a similar link 403. Arrhythmia detection, blood pressure waveform changes, and the other relevant diagnostic parameters described before can be transmitted to the bedside Patient Messenger 402 who can alert a Home Monitoring/Remote Programming Center, if medical attention is required.

(29) Referring to FIG. 8, the nerve stimulation electrode cuff 304 includes a minimum of two external contacts 600 placed longitudinally across its outer wall that can be used for galvanic communication 601 with an external skin Patch 602 applied on the patient's neck 603 or adjacent upper body location and wired to an external Programmer 604. The external skin Patch 602 can also be employed as an ambulatory monitor, if desired, with a low-power wireless link 605 to a bedside Patient Messenger 606 connected to, for example, a Home Monitoring/Remote Programming Center. The external contacts 600 can also be used for heart rate determination.

(30) In an embodiment, the same communication contacts 600 of FIG. 8 for galvanic intrabody communication via modulation of an imposed alternating electric field can be multiplexed and utilized for impedance plethysmography that indirectly allows measuring the pulsatile blood flow through the CCA. The circuitry built-in for nerve impedance measurement can be used for this purpose.

(31) The nerve cuff stimulation electrode 304 may also communicate via galvanic intrabody communication 607 with an implantable heart monitor 608 or another implantable device with the capability of MICS-communication 609 (or equivalent) with the bedside Patient Messenger 606.

(32) Technical advantages of this invention include at least: a nerve cuff stimulation electrode with built-in electronic circuitry that includes a pulsation sensor (e.g. electrical impedance plethsymography or strain gauge), a tilt-kinematic sensor (e.g. a triaxial accelerometer), and associated front-end electronic circuitry, implanted as a standard VNS cuff for CHF; a VNS for CHF system, capable of recording CCA and IJV pressure waveforms, critical parameters for CHF monitoring, in addition to other relevant parameters, such as heart rate, OSA-related, body posture, etc.; a VNS for CHF system, capable of recording intrathoracic far-field EGMs for arrhythmia detection in particular; and/or a VNS for CHF system, suitable for integration into a Home Monitoring/Remote Programming regime or another monitoring device.

(33) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.