Medical device ECG marker for use in compressed data system

• US 6,347,245 B1
• Filed: 07/14/1999
• Issued: 02/12/2002
• Est. Priority Date: 07/14/1999
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Lee, Brian B., Kane, Michael R.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/353,277
• Time in Patent Office: 944 Days
• Field of Search: 607/9, 607/27, 607/28, 607/30, 607/59, 600/509, 600/510, 600/521, 600/519, 600/523
• US Class Current: 600/523
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A system for recording trigger events and noise in conjunction with the recording of physiological signals is provided for use in an implantable medical device. In one embodiment, recorded trigger and noise data is provided for display to a physician along with reconstructed ECG data to facilitate interpretation of the ECG signal. In one embodiment, digitized ECG samples that are outside of a predetermined range are discarded during the sampling process so that one or more ranges of encoded values are available for use in encoding noise and trigger information. This non-physiologic data may be limited in size to individual point values of the ECG signal.

Claims

1. An implantable medical device (IMD) comprising electrodes suitable for chronic contact with internal tissue in a living body so as to receive physiologically originated electrical signals via said contact, said IMD having a hermetically sealed housing and at least one conductor inside said housing, and wherein said electrodes are connected to provide said physiologically originated electrical signals to said at least one conductor inside said housing, said IMD further comprising:

an ECG sensing circuit inside said housing for receiving said physiologically originated electrical signals from said at least one conductor and for generating ECG sample signals having values representative of a feature in said physiologically originated electrical signals at a sampling rate;

an activation triggering circuit inside said housing also in electrical connection to said at least one conductor, for sensing a triggering event and for generating and providing as output, a trigger signal in the presence of triggering events;

a memory circuit connected to receive data signals and to store or retrieve said data signals under control of a processor circuit;

said processor circuit for reacting to said trigger signal to initiate storage into said memory of a group ECG sample signal in said ECG sample signals and said trigger signal such that said trigger signal replaces at least one of said group of ECG sample signals.

2. The IMD as set forth in claim 1 wherein said activation trigger circuit further comprises a noise sensing circuit in electrical connection to said at least one conductor, for sensing noise in said at least one conductor, and in response thereto, for generating a noise detection signal as said trigger signal if noise is sensed to be present in said at least one conductor.

3. The IMD as set forth in claim 2 further comprising an input amplifier circuit coupled to said ECG sensing circuit for generating apparent R-wave signals based on said physiologically originated electrical signals from said at least one conductor, and for generating apparent R-wave detection signals responsive thereto;

and

an auto-trigger circuit for detecting apparent arrhythmias based on said apparent R-wave detection signals from said input amplifier circuit.

4. The IMD as set forth in claim 2 further comprising an input amplifier circuit coupled to said ECG sensing circuit for generating apparent R-wave signals based on said physiologically originated electrical signals from said at least one conductor, and for generating apparent R-wave detection signals responsive thereto, and input amplifier circuit further being responsive to said noise detection signal to cancel generation of said apparent R-wave detection signals in the presence of said noise detection signals;

and

an auto-trigger circuit for detecting apparent arrhythmias based on said apparent R-wave detection signals from said input amplifier circuit.

5. The IMD as set forth in claim 1, and further comprising an R-wave detection circuit connected to said at least one conductor for sensing the presence of apparent R-waves in said physiologic signal and for generating an R-wave detect signal when apparent R-waves are sensed, and wherein said activation trigger circuit comprises a trigger sensing circuit coupled to receive said R-wave detect signal, and for generating an apparent arrhythmia signal as said trigger signal in the presence of a predetermined pattern of R-wave detect signals.

6. The IMD as set forth in claim 5, wherein said processor circuit includes means for receiving a manual trigger signal generated outside said living body, and in response thereto, for initiating storage into said memory of said group of said ECG sample signals.

7. The IMD of claim 6, wherein said processor in response to a manual trigger signal produces distinct data signal indicative of said manual trigger signal.

8. The IMD as set forth in claim 1, and further comprising:

an R-wave detection circuit connected to said at least one conductor for sensing the presence of apparent R-waves in said physiologic signal and for generating an R-wave detect signal when apparent R-waves are sensed, and wherein;

said activation trigger circuit comprises a trigger sensing circuit coupled to receive said R-wave detect signal, and for generating and providing as output, an apparent arrhythmia signal as said trigger signal in the presence of a predetermined pattern of sensed apparent R-waves; and

a noise sensing circuit in electrical connection to said at least one conductor, for sensing noise in said conductor and for generating and providing as output, a noise detection signal if noise is sensed to be present in said at least one conductor, and wherein;

said processor circuit stores a data signal representative of said noise detection signal into said group of ECG sample signals.

9. The IMD as set forth in claim 1, and further comprising an additional physiologic sensor circuit comprising a physiologic sensor for measuring a physiologic a condition and an output generating circuit for generating an additional physiologic data signal output representative of said measurement of said physiologic condition, and wherein said processor circuit stores said additional physiologic data signal with said group of ECG sample signals.

10. The IMD as set forth in claim 1, wherein said processor circuit can only replace a predetermined number of said group of ECG sample signals with said memory trigger signal.

11. The IMD as set forth in claim 10, wherein said predetermined number is not more than 1 in a group of 30 ECG sample signals.

12. The IMD as set forth in claim 1, and further comprising signal to data conversion circuit means for generating a range of digital value data signals representative of said feature of said physiologic signal, wherein a portion of a said range is dedicated to storing signals indicative of said memory trigger signal and is unavailable for representing said feature.

13. The IMD as set forth in claim 1 wherein said feature is amplitude or a variation in amplitude.

14. A medical information system comprising the IMD as set forth in claim 1, wherein said IMD further comprises:

a telemetry circuit for sending and receiving telemetry data signals between itself and an outside device and further comprising;

said outside device having a telemetry circuit for receiving said telemetry data signals and having transformation circuitry for transforming said telemetry data signals into an image for display on a display screen, wherein said transformation circuitry reconstitutes said telemetry data as display data and wherein said transformation circuit parses said additional data from said ECG data in said reconstituted data for display of said ECG data as an ECG representation on said display screen.

15. An implantable medical device (IMD) for monitoring a physiological signal in a body, comprising:

a sensor to sense the physiological signal;

a sampling circuit coupled to the sensor to generate samples of the physiological signal;

a storage circuit coupled to the sampling circuit to selectively store ones of the generated samples in a time-ordered sequence;

a trigger circuit coupled to the storage circuit to generate a trigger signal in response to detection of a trigger event, the trigger signal to control the selective storage of the ones of the samples; and

wherein the storage circuit includes circuits to store one or more data signals that are descriptive of the trigger signal such that ones of the generated samples are replaced by the one or more data signals in the storage circuit.

16. The IMD of claim 15, wherein the one or more data signals that are descriptive of the trigger signal are descriptive of a type of the trigger event.

17. The IMD of claim 15, wherein the trigger circuit includes a circuit to generate the trigger signal in response to a trigger event of noise in the physiological signal.

18. The IMD of claim 16, wherein the trigger circuit includes a circuit to generate the trigger signal in response to a trigger event that includes detecting a predetermined characteristic of the physiological signal.

19. The IMD of claim 15, and further including a noise detector circuit coupled to the trigger circuit to generate noise signals indicative of noise in the physiological signal, and wherein the storage circuit includes circuits to store the noise signals along with the ones of the samples.

20. The IMD of claim 19, wherein the noise detector circuit includes means for generating the noise signals to indicate a type of the noise detected in the physiological signal.