Response to ambient noise in implantable pulse generator

• US 6,381,494 B1
• Filed: 08/20/1999
• Issued: 04/30/2002
• Est. Priority Date: 08/20/1999
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Harris, Thomas J., Gilkerson, James O., Perschbacher, David L., Birkholz, Doug M.
• Primary Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US09/378,321
• Time in Patent Office: 984 Days
• Field of Search: 607/9, 607/17, 607/18, 607/25, 607/27
• US Class Current: 607/27
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A method and system for response to ambient noise in implantable pulse generator. At least one cardiac signal is sensed with an implantable pulse generator. Cardiac depolarizations are identified in the at least one cardiac signal and cardiac depolarization markers are generated. The at least one cardiac signals are then analyzed for a noise event during a refractory period following the detected cardiac depolarization. The refractory period includes a noise window interval during which noise events are recognized. When a noise event, or events, occur during the noise window interval a first noise marker is generated. The noise window interval is then repeated as long as noise is detected in the noise window intervals. When the noise persists for a predetermined time interval a second noise marker is generated.

Claims

1. A method, comprising:

sensing at least one cardiac signal with an implantable pulse generator;

identifying the occurrence of a cardiac depolarization in the at least one cardiac signal and generating a cardiac depolarization marker when the cardiac depolarization is identified;

analyzing the at least one cardiac signal for a noise event during a refractory period, where the refractory period occurs after the detected cardiac depolarization and where the refractory period includes a noise window interval; and

repeating the noise window interval when the noise event occurs during the noise window interval.

2. The method of claim 1, where analyzing the at least one cardiac signal includes generating a first noise marker when the noise event occurs during the noise interval window.

3. The method of claim 2, including generating a second noise marker when the noise window interval is repeated for a predetermined time interval.

4. The method of claim 3, including programming the predetermined time interval to a value of 340 milliseconds and the noise window in the refractory period to a duration of forty (40) milliseconds.

5. The method of claim 3, including establishing a communication link between the implantable pulse generator and a medical device programmer, where the medical device programmer includes a display screen;

transmitting the at least one cardiac signal, which includes the cardiac depolarization, to the medical device programmer; and

displaying the at least one cardiac signal on the display screen.

6. The method of claim 5, including transmitting the cardiac depolarization marker to the medical device programmer;

and

displaying the cardiac depolarization marker on the display screen with the cardiac depolarization in the at least one cardiac signal.

7. The method of claim 6, including transmitting the first noise marker to the medical device programmer;

displaying the first noise marker on the display screen; and

associating the first noise marker and the noise event of the at least one cardiac signal.

8. The method of claim 7, including transmitting the second noise marker to the medical device programmer;

displaying the second noise marker on the display screen; and

associating the second noise marker and the at least one cardiac signal at the predetermined time interval.

9. The method of claim 8, including printing on paper the at least one cardiac signal, the cardiac depolarization marker, the first noise marker and the second noise marker.

10. The method of claim 1, where the cardiac signal includes a voltage and analyzing the at least one cardiac signal for the noise event includes detecting when the voltage of the cardiac signal exceeds a predetermined sensing floor value.

11. The method of claim 1, where identifying the occurrence of the cardiac depolarization includes producing a pacing level pulse, and identifying the cardiac depolarization when the pacing level pulse is produced.

12. A system, comprising:

at least one cardiac lead that includes two or more electrodes;

control circuitry coupled to the two or more electrodes, where the control circuitry receives at least one cardiac signal that includes indications of cardiac depolarizations and generates a cardiac depolarization marker when the cardiac depolarization is identified, and where the control circuitry includes;

a microprocessor, where the microprocessor times a refractory period and a noise window interval contained within the refractory period;

a cardiac depolarization detector circuit coupled to the microprocessor, where the cardiac depolarization detector circuit detects the occurrence of a cardiac depolarization in the at least one cardiac signal and the microprocessor starts the refractory period after the cardiac depolarization; and

a noise event analysis circuit coupled to the microprocessor and the cardiac depolarization detector circuit, where noise event analyzing circuit analyzes the at least one cardiac signal for noise events during the refractory period, and where the microprocessor repeats the noise window interval when the noise event analysis circuit detects a noise event during the noise window interval.

13. The system of claim 12, where the control circuitry generates a first noise marker when the noise event analysis circuit detects noise events in the noise interval window.

14. The system of claim 13, where the control circuitry generates a second noise marker when the microprocessor repeats the noise window interval for a predetermined time interval.

15. The system of claim 14, where the predetermined time interval is programmed to a value of 340 milliseconds and the noise window in the refractory period is programmed to a duration of forty (40) milliseconds.

16. The system of claim 14, including a communication circuit coupled to the microprocessor;

and

a medical device programmer, where the medical device programmer includes programmer circuitry and a display screen coupled to the programmer circuitry, and where the medical device programmer establishes a communication link with the communication circuit and the communication circuit transmits the at least one cardiac signal, including the occurrence of the cardiac depolarization, to the programmer circuitry for display on the display screen.

17. The system of claim 16, where the communication circuit transmits the cardiac depolarization marker to the programmer circuitry for display on the display screen.

18. The system of claim 16, where the communication circuit transmits the first noise marker to the programmer circuitry for display on the display screen.

19. The system of claim 18, where the communication circuit transmits the second noise marker to the programmer circuitry for display on the display screen.

20. The system of claim 13, where the at least one cardiac signal includes a voltage, and the noise event analysis circuit detects the noise event when the voltage of the cardiac signal exceeds a predetermined sensing floor value.

21. The system of claim 20, where the predetermined sensing floor value is a programmable value in the range of 0.18 to 0.45 millivolts.