WIRELESS TISSUE ELECTROSTIMULATION

• US 20090204170A1
• Filed: 01/29/2009
• Published: 08/13/2009
• Est. Priority Date: 02/07/2008
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Becker, John A., Hastings, Roger, Pikus, Michael J., Edmunds, Kevin D., Lafontaine, Daniel M.
• Granted Patent: US 8,738,147 B2
• Time in Patent Office: Days
• US Class Current: 607/33
• CPC Class Codes: A61N 1/0565 Electrode heads
• CPC Class Codes: A61N 1/057 Anchoring means; Means for fixing the head inside the heart
• CPC Class Codes: A61N 1/0573 chacterised by means penetrating the heart tissue, e.g. helix needle or hook
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3624 occurring in the atrium, i.e. atrial tachycardia
• CPC Class Codes: A61N 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/36842 Multi-site stimulation in the same chamber
• CPC Class Codes: A61N 1/37205 Microstimulators, e.g. implantable through a cannula
• CPC Class Codes: A61N 1/37223 Circuits for electromagnetic coupling
• CPC Class Codes: A61N 1/37229 Shape or location of the implanted or external antenna
• CPC Class Codes: A61N 1/3756 Casings with electrodes thereon, e.g. leadless stimulators
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

A wireless electrostimulation system can comprise a wireless energy transmission source, and an implantable cardiovascular wireless electrostimulation node. A receiver circuit comprising an inductive antenna can be configured to capture magnetic energy to generate a tissue electrostimulation. A tissue electrostimulation circuit, coupled to the receiver circuit, can be configured to deliver energy captured by the receiver circuit as a tissue electrostimulation waveform. Delivery of tissue electrostimulation can be initiated by a therapy control unit.

Claims

1. A wireless electrostimulation system comprising:

a wireless energy transmission source, including an inductive antenna, configured to generate a time-varying magnetic flux;

a cardiovascular wireless electrostimulation node sized and shaped to be implantable using a percutaneous transluminal catheter delivery system, the wireless electrostimulation node comprising;

a receiver circuit configured to capture at least enough inductively-coupled energy from the inductive antenna to generate a tissue electrostimulation, the receiver circuit comprising a mechanically-expandable inductive pickup configured to link the time-varying magnetic flux, the inductive pickup comprising a core material including a relative magnetic permeability less than 1. 1; and

a tissue electrostimulation circuit, coupled to the receiver circuit, configured to deliver energy captured by the receiver circuit as a specified tissue electrostimulation waveform, the tissue electrostimulation circuit comprising at least one tissue electrostimulation electrode; and

a therapy control unit, commnunicatively coupled to the tissue electrostimulation node and configured to initiate a delivery of a tissue electrostimulation by the tissue electrostimulation electrode.

2. The system of claim 1, wherein the cardiovascular wireless electrostimulation node is configured and sized for intravascular delivery.

3. The system of claim 1, wherein the receiver circuit comprises:

an energy storage device configured to store inductively-coupled energy transferred by the time-varying magnetic flux;

wherein the energy storage device is configured to store at most 1 milliJoule of energy; and

wherein the tissue electrostimulation is inhibited by a depletion of the energy storage device no more than 1 minute after the termination of the inductively-coupled energy transfer.

4. The system of claim 1, wherein the tissue electrostimulation circuit comprises:

a rectifier, coupled between the receiver circuit and the tissue stimulation electrode;

a direct-current blocking device, coupled between the tissue electrostimulation electrode and the receiver circuit;

wherein the at least one tissue electrostimulation electrode comprises a cathode configured to be coupled to cardiac tissue;

wherein the at least one tissue electrostimulation electrode comprises an anode configured to be coupled to cardiac tissue; and

wherein the tissue electrostimulation circuit is configured to be capable of generating, between the anode and the cathode, an electrostimulation pulse of at least 2.5V peak amplitude at a pulse width of 0.4 msec when coupled to a 500 Ohm equivalent load.

5. The system of claim 4, wherein the cardiovascular wireless electrostimulation node comprises:

a mechanically-expandable inductive pickup comprising;

an insulated wire loop; and

an expandable mechanical support comprising a loop of shape-memory material mechanically coupled to the insulated wire loop, wherein at least a portion of the loop of shape-memory material is non-conductive;

a housing comprising;

a receiver circuit electrical charge storage device conductively coupled to the insulated wire loop; and

the tissue electrostimulation circuit;

wherein the housing is disposed within a space encompassed by the loop of shape-memory material; and

a strut, comprised of shape-memory material, configured to secure the loop of shape-memory material to the cylindrical housing.

6. The system of claim 5, comprising a bio-compatible dielectric encapsulant configured to encompass at least a portion of the inductive pickup.

7. The system of claim 5, wherein the wireless energy transmission source is configured to vary a burst pulse duration of the time-varying magnetic flux, wherein the tissue electrostimulation circuit comprises a voltage clamping device coupled to the output of the rectifier, and wherein an energy content of the electrostimulation pulse is controlled by the burst pulse duration when a voltage across the voltage clamping device is substantially equal to or greater than a voltage clamping device threshold voltage.

8. The system of claim 5, wherein the inductive pickup is configured for a maximum outside diameter, when expanded, of less than or equal to 2 cm;

wherein the housing comprises a cylindrical diameter less than or equal to 2 mm, and a length less than or equal to 5 mm; and

wherein a total length of the cylindrical housing and the cardiac tissue attachment mechanism is less than or equal to a nominal minimum myocardial tissue wall thickness of 10 mm.

9. The system of claim 1, wherein the wireless energy transmission source is configured to generate the time-varying magnetic flux at a specified receiver resonant frequency within a range of frequencies from 500 kilohertz to 5 megahertz, inclusive;

and wherein the wireless energy transmission source is configured to deliver the inductively coupled energy at a power coupling efficiency of at least 1%.

10. The system of claim 1, wherein the wireless energy transmission source and the therapy control unit are both configured to be located external to a patient'"'"'s body containing the wireless electrostimulation node.

11. The system of claim 1, comprising a battery-powered implantable cardiac rhythm management unit that includes the wireless energy transmission source and the therapy control unit.

12. The system of claim 11, wherein the wireless energy transmission source comprises:

an implantable flexible lead comprising;

a distal end configured to be located near the implantable wireless electrostimulation node;

a proximal end configured to be located at or near a housing of the battery-powered implantable cardiac rhythm management unit;

at least two antenna feed conductors disposed internally to the lead and conductively coupled to the housing of the battery-powered implantable cardiac rhythm management unit; and

the inductive antenna disposed at the distal end of the lead, and conductively coupled to the at least two antenna feed conductors at the distal end of the lead; and

the therapy control unit configured to energize the at least two antenna feed conductors.

13. A method, comprising:

delivering a cardiovascular wireless electrostimulation node to an intra-body location;

expanding a wireless electrostimulation node inductive pickup;

generating a time-varying magnetic flux;

linking the time-varying magnetic flux to the wireless electrostimulation node inductive pickup;

configuring a wireless electrostimulation node inductive pickup wire loop with a core material of a relative magnetic permeability less than 1. 1;

capturing at least enough inductively-coupled energy to deliver a tissue electrostimulation;

controlling the initiation of the delivery of a specified tissue electrostimulation waveform; and

delivering a specified tissue electrostimulation waveform in response to an initiation.

14. The method of claim 13, comprising:

delivering a cardiovascular wireless electrostimulation node through a vascular path to an intra-body location.

15. The method of claim 13, comprising:

storing the inductively-coupled energy within an energy storage device included in the wireless electrostimulation node;

inhibiting the storage of more than 1 milliJoule of energy within the energy storage device;

terminating the time-varying magnetic flux;

depleting the energy storage device; and

inhibiting the delivery of the tissue electrostimulation more than 1 minute after the termination of the time-varying magnetic flux in response to the depleting the energy storage device.

16. The method of claim 13, comprising:

rectifying the time-varying magnetic flux;

coupling a cathode to cardiac tissue;

coupling an anode to cardiac tissue;

generating, between the anode and the cathode, an electrostimulation pulse of at least 2.5V peak amplitude at a pulse width of 0.4 msec when coupled to a 500 Ohm equivalent load; and

blocking the passage of direct-current between a tissue stimulation electrode and a receiver circuit.

17. The method of claim 16, comprising:

insulating the inductive pickup wire loop;

coupling the inductive pickup wire loop to a shape-memory mechanical support mechanically;

expanding the shape-memory expandable mechanical support to a specified loop shape proximate to a cardiac tissue wall;

forming a non-conductive portion along the circumference of the shape-memory expandable mechanical support;

coupling the shape-memory mechanical support to a cylindrical housing mechanically; and

disposing the cylindrical housing within a space encompassed by the shape-memory mechanical support.

18. The method of claim 17, comprising:

encompassing at least a portion of the inductive pickup with a bio-compatible dielectric encapsulant.

19. The method of claim 17, comprising:

varying a burst pulse duration of the time-varying magnetic flux;

clamping a voltage developed by the rectifying the time-varying magnetic flux; and

controlling an energy content of the electrostimulation pulse, via the varying of the burst pulse duration of the time-varying magnetic flux, when a voltage across a voltage clamping device is substantially equal to or greater than a voltage clamping device threshold voltage.

20. The method of claim 17, comprising:

expanding the inductive pickup to a maximum outside diameter, when expanded, of less than or equal to 2 cm;

limiting the cylindrical housing to a diameter less than or equal to 2 mm;

limiting the cylindrical housing to a length less than or equal to 5 mm; and

limiting a total length of the cylindrical housing and a cardiac tissue attachment mechanism to less than or equal to a nominal minimum myocardial tissue wall thickness of 10 mm.

21. The method of claim 13, comprising:

generating the time-varying magnetic flux at a specified receiver resonant frequency within a range of frequencies from 500 kilohertz to 5 megahertz, inclusive; and

transferring the inductively-coupled energy at a power coupling efficiency of at least 1%.

22. The method of claim 13, comprising:

generating the time-varying magnetic flux from a location external to a patient'"'"'s body; and

initiating a tissue electrostimulation from a location external to the patient'"'"'s body.

23. The method of claim 13, comprising:

delivering a battery-powered implantable cardiac rhythm management unit to an intra-body location;

conductively coupling an inductive antenna to the implantable cardiac rhythm management device;

generating the time-varying magnetic flux using the inductive antenna; and

initiating a tissue electrostimulation using the implantable cardiac rhythm management unit.

24. The method of claim 23, comprising:

locating a distal end of an implantable flexible lead near to the implantable wireless electrostimulation node;

mechanically coupling the inductive antenna to the distal end of the implantable flexible lead;

locating a proximal end of the cardiovascular implantable flexible lead at or near to a housing of the battery-powered implantable cardiac rhythm management unit therapy control unit;

locating at least two antenna feed conductors within the implantable flexible lead;

conductively coupling the at least two antenna feed conductors from the battery-powered implantable cardiac rhythm management unit therapy control unit housing to the inductive antenna; and

energizing the at least two antenna feed conductors.

25. A system comprising:

means for delivering a cardiovascular wireless electrostimulation node to an intra-body location;

means for expanding a wireless electrostimulation node inductive pickup;

means for generating a time-varying magnetic flux;

means for linking the time-varying magnetic flux to the wireless electrostimulation node inductive pickup;

means for surrounding a wireless electrostimulation node inductive pickup wire loop with a material of a relative magnetic permeability less than 1.1;

means for capturing at least enough inductively-coupled energy to deliver a tissue electrostimulation;

means for controlling the initiation of the delivery of a specified tissue electrostimulation waveform; and

means for delivering a specified tissue electrostimulation waveform in response to an initiation.