System for waveform stimulation compensating electrode polarization

• US 20060224199A1
• Filed: 03/31/2005
• Published: 10/05/2006
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zeijlemaker, Volkert A.
• Granted Patent: US 7,577,480 B2
• Time in Patent Office: Days
• US Class Current: 607/11
• CPC Class Codes: A61N 1/371 Capture, i.e. successful stimulation

Abstract

Upon delivery of a pacing pulse to a heart by an electrode of an implantable medical device (IMD), a deleterious pace polarization artifact is generally created at the electrode-tissue interface and subsequently stored by the electrode. Such polarization artifact is generally minimized through the use of passive recharge circuitry. Such passive recharge circuitry functions in creating a recharge pulse at the electrode which in essence, minimizes the polarization artifact on the electrode. In order to produce further artifact minimization from a subsequent pacing pulse, following termination of the recharge pulse, any remaining polarization artifact is sampled and analyzed by the IMD and IMD software optionally compensates the next recharge pulse to further minimize the polarization artifact generated by a next pacing pulse. This sampling and optional compensation is repeated for subsequent pacing pulses so that polarization artifacts are effectively analyzed and if necessary, minimized.

Claims

1. A method of reducing polarization on an implanted electrode used for electrically stimulating cardiac tissue, comprising:

a) providing an implantable medical device used for electrically stimulating cardiac tissue via one or more electrodes and used for sensing cardiac signals emanating from the cardiac tissue via one or more sense amplifiers;

b) delivering an electrical stimulation pulse generated by the device to the cardiac tissue via one of the electrodes;

c) delivering an electrical recharge pulse generated by the device to the cardiac tissue via the one of the electrodes, the electrical recharge pulse for minimizing polarization on the one of the electrodes resulting from the electrical stimulation pulse;

d) sensing the polarization on the one of the electrodes after delivery of the electrical recharge pulse;

e) determining whether the magnitude of the sensed polarization is within a predetermined desirable range;

f) calculating an adjustment amount for the electrical recharge pulse if the sensed polarization is not within the predetermined desirable range, the adjustment amount being based on the sensed polarization and calculated towards minimizing the sensed polarization; and

g) adjusting the electrical recharge pulse by the calculated adjustment amount for a subsequent electrical recharge pulse to improve the minimization of the polarization resulting from a subsequent electrical stimulation pulse.

2. The method of claim 1, wherein the adjustment amount is proportional to the sensed polarization.

3. The method of claim 1, wherein the adjustment amount is calculated as a fraction of the electrical recharge pulse.

4. The method of claim 1, wherein the electrical recharge pulse is not adjusted if the magnitude of the sensed polarization is within the predetermined desirable range.

5. The method of claim 1, wherein the predetermined desirable range is less than 1 millivolt.

6. The method of claim 1, wherein the electrode polarization is sensed before a T-wave emanates from the cardiac tissue.

7. The method of claim 1, wherein the electrode polarization is sensed a predetermined amount of time after delivery of the electrical recharge pulse.

8. The method of claim 1, further comprising adjusting signal gain when sensing the polarization on the on of the electrodes to more accurately quantify polarization.

9. The method of claim 1, wherein the adjustment amount adjusts the amplitude of the electrical recharge pulse.

10. The method of claim 1, wherein the adjustment amount for the electrical recharge pulse is calculated using the formula

Adjustment Amount=α

*V_sample(x)*V_Sx,

where V_Sx is amplitude of the electrical recharge pulse, α

is a constant, and V_sample(x) is the amplitude of the polarization sample.

11. The method of claim 10, wherein the amplitude of the electrical recharge pulse is adjusted to produce the subsequent recharge pulse according to the formula Subsequent Recharge Pulse=V_Sx−

Adjustment Amount.

12. The method of claim 10, wherein α

is set to 0.2.

13. An implantable medical device for electrically stimulating cardiac tissue, comprising:

a) a lead that conducts electrical pulses to an electrode on the lead, the electrode adapted for electrical contact with cardiac tissue;

b) a pulse generator coupled to the lead to deliver electrical pulses to the cardiac tissue via the electrode, the generator generating an electrical stimulation pulse and an electrical recharge pulse, the electrical recharge pulse for minimizing polarization on the electrode resulting from the electrical stimulation pulse;

c) a sensor that senses the polarization on the one of the electrodes, the sensor sensing the polarization after delivery of the electrical recharge pulse; and

d) a processor that calculates an adjustment amount for the electrical recharge pulse if the sensed polarization is not within a predetermined desirable range, the adjustment amount being based on the sensed polarization and calculated towards minimizing the sensed polarization, the processor adjusting the electrical recharge pulse by the calculated adjustment amount for a subsequent electrical recharge pulse.

14. The implantable medical device of claim 13, wherein the implantable medical device is a pacemaker.

15. The implantable medical device of claim 13, wherein the electrodes on the cardiac tissue are located for providing anti-tachycardia therapy.

16. The implantable medical device of claim 13, wherein the processor is a digital signal processor.

17. A computer readable medium that provides instructions, which when executed on a processor, cause said processor to perform operations for reducing polarization on at least one electrode, the processor being within a controller of an implantable medical device for electrically stimulating cardiac tissue via the at least one electrode, wherein the implantable medical device is also used for sensing cardiac signals emanating from the cardiac tissue via at least one sense amplifier, the operations comprising:

a) creating an electrical stimulation pulse to stimulate cardiac tissue via one electrode;

b) generating an electrical recharge pulse for delivery to the cardiac tissue via the one electrode to minimize polarization remaining on the one electrode from the electrical stimulation pulse;

c) sampling the polarization remaining on the one electrode a certain time after the electrical recharge pulse is delivered;

d) determining whether the sampled polarization is at a desirable level;

e) calculating an adjustment amount for the electrical recharge pulse if the sampled polarization is not within the predetermined desirable range, the adjustment amount being based on the sampled polarization and calculated towards minimizing the sensed polarization; and

f) adjusting the electrical recharge pulse by the calculated adjustment amount for a subsequent electrical recharge pulse to improve the minimization of the polarization resulting from a subsequent electrical stimulation pulse.

18. The computer readable medium of claim 17, further comprising adjusting the electrical recharge pulse by the calculated adjustment amount for the subsequent electrical recharge pulse after delivery of the subsequent electrical stimulation pulse.

19. The computer readable medium of claim 17, further comprising adjusting the electrical recharge pulse by the calculated adjustment amount for the subsequent electrical recharge pulse before and after delivery of the subsequent electrical stimulation pulse.

20. The computer readable medium of claim 19, further comprising

a) adjusting the calculated adjustment amount for the electrical recharge pulse;

b) delivering the subsequent electrical recharge pulse to the cardiac tissue via the one electrode before delivery of the subsequent electrical stimulation pulse and based on the adjusted calculated adjustment amount;

c) sampling the polarization on the one electrode after delivery of the subsequent electrical recharge pulse;

d) calculating a further adjustment amount for the electrical recharge pulse based on the sampling of the subsequent electrical recharge pulse and the calculated adjustment amount; and

e) adjusting the electrical recharge pulse by the further calculated adjustment amount for a subsequent electrical recharge pulse after delivery of the subsequent electrical stimulation pulse.