Wireless tissue electrostimulation

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 cardiovascular 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 including an expandable coil configured to receive the time-varying magnetic flux, the inductive pickup comprising a core material including a relative magnetic permeability less than 1.1, wherein the mechanically-expandable inductive pickup comprises an expandable mechanical support comprising a loop of shape-memory material mechanically coupled to the expandable coil;

a strut coupling the expandable mechanical support to a housing of the cardiovascular wireless electrostimulation node, the strut including a portion that controls an implant depth of the cardiovascular wireless electrostimulation node in myocardial tissue when the portion is pressed against a tissue surface; 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, communicatively coupled to the cardiovascular wireless 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 1 , wherein

wherein at least a portion of the loop of shape-memory material is non-conductive; and

wherein the cardiovascular wireless electrostimulation node includes 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.

6. The system of claim 1 , comprising a bio-compatible dielectric encapsulant configured to encompass at least a portion of the inductive pickup.

7. The system of claim 4 , 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 cardiovascular 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 cardiovascular 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 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 cardiovascular 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 including an expandable coil configured to receive the time-varying magnetic flux, the inductive pickup comprising a core material including a relative magnetic permeability less than 1.1; wherein the mechanically-expandable inductive pickup comprises an expandable mechanical support comprising a loop of shape-memory material mechanically coupled to the expandable coil;

a strut coupling the expandable mechanical support to a housing of the cardiovascular wireless electrostimulation node, the strut including a portion that controls an implant depth of the cardiovascular wireless electrostimulation node in myocardial tissue when the portion is pressed against a tissue surface; 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, communicatively coupled to the cardiovascular wireless electrostimulation node and configured to initiate a delivery of a tissue electrostimulation by the tissue electrostimulation electrode;

wherein the cardiovascular wireless electrostimulation node is configured and sized for intravascular delivery; and

wherein at least one of the wireless energy transmission source or the therapy control unit are both configured to be located external to a patient's body containing the cardiovascular wireless electrostimulation node.

14. A method, comprising:

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

expanding a cardiovascular wireless electrostimulation node inductive pickup, the mechanically-expandable inductive pickup comprising a core material including a magnetic permeability less than 1.1, the mechanically-expandable inductive pickup including an expandable coil, and the expanding including expanding the expandable coil;

generating a time-varying magnetic flux;

receiving the time-varying magnetic flux using the cardiovascular wireless electrostimulation node inductive pickup;

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;

wherein the mechanically-expandable inductive pickup comprises an expandable mechanical support comprising a loop of shape-memory material mechanically coupled to the expandable coil and

wherein the cardiovascular wireless electrostimulation node comprises a strut coupling the expandable mechanical support to a housing of the cardiovascular wireless electrostimulation node, the strut including a portion that controls an implant depth of the cardiovascular wireless electrostimulation node in myocardial tissue when the portion is pressed against a tissue surface.

15. The method of claim 14 , comprising:

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

16. The method of claim 14 , comprising:

storing the inductively-coupled energy within an energy storage device included in the cardiovascular 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.

17. The method of claim 14 , 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.

18. The method of claim 14 , comprising:

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

mechanically coupling the shape-memory mechanical support to a housing of the cardiovascular wireless electrostimulation node; and

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

19. The method of claim 14 , comprising:

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

20. 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.

21. The method of claim 18 , 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.

22. The method of claim 14 , 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%.

23. The method of claim 14 , 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.

24. The method of claim 14 , 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.

25. The method of claim 24 , comprising:

locating a distal end of an implantable flexible lead near to the cardiovascular 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.