Implantable monitor

• US 6,230,059 B1
• Filed: 03/17/1999
• Issued: 05/08/2001
• Est. Priority Date: 03/17/1999
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Duffin, Edwin G.
• Primary Examiner(s): KAMM, WILLIAM E
• Application Number:
  US09/271,107
• Time in Patent Office: 783 Days
• Field of Search: 607/32, 607/60, 128/903, 600/300, 600/510
• US Class Current: 607/60
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

An implantable medical device (IMD) capable of monitoring physiologic data, distinguishing relatively noisy and noise free physiologic data, and recording noisy and relatively noise free segments of physiologic data in separate memory registers of a limited memory for retrieval and analysis at a later time. Preferably the physiologic data comprises the sampled EGM of the heart detected from sense electrode pairs that are implanted in the patient at sites where extraneous electrical noise, e.g., electromyographic signals, are also capable of being detected. The sense electrode pairs can constitute one or both sense electrodes located on or adjacent to the atrial and/or ventricular heart chambers and coupled to the IMD by a lead body or sense electrode pairs that are located remotely from the heart, e.g. at a subcutaneous implantation site of the IMD. A plurality of noisy EGM episode data registers store a corresponding plurality of noisy EGM episode data sets on a FIFO basis and another plurality of noise free EGM episode data registers to store a corresponding plurality of relatively noise free EGM episode data sets on a FIFO basis. Any form of discrimination of noisy data from relatively noise free data can be employed at the time of recording, but because the stored EGM episode data sets are subsequently viewed and analyzed by a physician, discrimination with absolute certainty is not required, and the physician can alter the detection criteria to fine tune it.

Claims

1. In an implantable medical device adapted to be implanted in a patient and operated to record electrical signals of the body for later retrieval and review to aid in diagnosing a condition of the patient, a method for recording such data that may be corrupted by ambient electrical noise comprising the steps of:

sampling the electrical signals of interest and providing sample values;

commanding the storage of a sequence of sample values in a storage register from which the sample values can be retrieved for review at a later time; and

in response to the commanded storage, examining the sequence of sample values to determine if the sequence of sample values is corrupted with noise or is relatively noise free; and

if the sequence of sample values is determined to be corrupted by noise, storing the sequence of sample values in a storage register designated as a noisy storage register to only receive a sequence of sample values determined to be corrupted by noise;

or

if the sequence of sample values is determined to be relatively noise free, storing the sequence of sample values in a storage register designated as a relatively noise free storage register to only receive sample values determined to be relatively noise free.

2. The method of claim 1, wherein the number of noisy and relatively noise free storage registers of the implantable medical device are limited, and wherein said storing steps further comprise the steps of:

storing the sequence of sample values determined to be corrupted by noise in a noisy storage register on a FIFO basis, whereby the oldest sequence of sample values corrupted by noise is deleted if the noisy storage registers are already filled; and

storing the sequence of sample values determined to be relatively free of noise in a noise free storage register on a FIFO basis, whereby the oldest sequence of sample values determined to be relatively free of noise is deleted if the noise free storage registers are already filled.

3. The method of claim 2, wherein the commanding step further comprises the step of:

receiving a storage command originating externally to the patient'"'"'s body and commanding the storage of the sequence of sample values in a storage register.

4. The method of claim 2, wherein the commanding step further comprises the steps of:

monitoring a state of the electrical signals of interest with respect to detection criteria of a medical condition of interest; and

commanding the storage of the sequence of sample values in a storage register when the electrical signals of interest satisfy the detection criteria.

5. The method of claim 1, wherein the commanding step further comprises the steps of:

monitoring a state of the electrical signals of interest with respect to detection criteria of a medical condition of interest; and

commanding the storage of the sequence of sample values in a storage register when the electrical signals of interest satisfy the detection criteria.

6. The method of claim 1, wherein the commanding step further comprises the steps of:

receiving a storage command originating externally to the patient'"'"'s body and commanding the storage of the sequence of sample values in a storage register.

7. The method of claim 1, wherein the electrical signals of the body comprise the cardiac EGM, the sample values are EGM sample values, and the sequence of EGM sample values comprise EGM episode data, and wherein the commanding step further comprises the step of:

receiving a patient initiated storage command originating externally to the patient'"'"'s body and commanding the storage of EGM episode data in a storage register.

8. The method of claim 1, wherein the electrical signals of the body comprise the cardiac EGM, the sample values are EGM sample values, and the sequence of EGM sample values comprise EGM episode data, and wherein the commanding step further comprises the steps of:

comparing the EGM sample values to arrhythmia detection criteria of one or more tachyarrhythmia condition of interest; and

commanding the storage of the EGM episode data in a storage register when a sequence of the EGM sample values satisfy the detection criteria.

9. In an implantable medical device adapted to be implanted in a patient and operated to record electrical signals of interest of the body for later retrieval and review to aid in diagnosing a condition of the patient, apparatus for recording sequences of such electrical signals that may be corrupted by ambient electrical noise comprising:

means for sampling the electrical signals of interest and providing sample values;

a data memory comprising at least one noisy storage register designated to only store a sequence of sample values determined to be corrupted by noise and at least one noise free storage register designated to only store a sequence of sample values determined to be relatively noise free;

means for commanding the storage of the sequence of sample values in a storage register of said data memory;

means for examining the sequence of sample values to determine if the sequence of sample values is corrupted with noise or is relatively noise free, and

storing means operable, if the sequence of sample values is determined to be corrupted by noise, for storing the sequence of sample values in a noisy storage register and operable, if the sequence of sample values is determined to be relatively noise free, for storing the sequence of sample values in a noise free storage register.

10. The apparatus of claim 9, wherein:

said data memory comprises a plurality of noisy and relatively noise free storage registers; and

said storing means further comprises means for storing the sequence of sample values in a noisy or noise free storage register on a FIFO basis, whereby the oldest sequence of sample values stored in the noisy or noise free storage register, respectively, is deleted.

11. The apparatus of claim 10, wherein the commanding means further comprises:

means for receiving a storage command originating externally to the patient'"'"'s body and for commanding storage of the sequence of sample values in a storage register.

12. The apparatus of claim 10, wherein the commanding means further comprises:

means for monitoring a state of the electrical signals of interest with respect to detection criteria of a medical condition of interest; and

means for commanding the storage of the sequence of sample values in a storage register when the electrical signals of interest satisfy the detection criteria.

13. The apparatus of claim 9, wherein the commanding means further comprises:

means for receiving a storage command originating externally to the patient'"'"'s body and for commanding storage of the sequence of sample values in said temporary storage register.

14. The apparatus of claim 9, wherein the commanding means further comprises:

means for monitoring a state of the electrical signals of interest with respect to detection criteria of a medical condition of interest; and

means for commanding the storage of the sequence of sample values in a storage register when the electrical signals of interest satisfy the detection criteria.

15. The apparatus of claim 9, wherein the electrical signals of the body comprise the cardiac EGM, the sample values are EGM sample values, and the sequence of EGM sample values comprise EGM episode data, and the commanding means further comprises:

means for receiving a storage command originating externally to the patient'"'"'s body and for commanding storage of the EGM episode data in a storage register.

16. The apparatus of claim 9, wherein the electrical signals of the body comprise the cardiac EGM, the sample values are EGM sample values, and the sequence of EGM sample values comprise EGM episode data, and the commanding means further comprises:

means for comparing the EGM sample values to arrhythmia detection criteria of one or more tachyarrhythmia condition of interest; and

means for commanding the storage of the EGM episode data in a storage register when a sequence of the EGM sample values satisfy the detection criteria.

17. In an implantable medical device adapted to be implanted in a patient and operated to record EGM episode data of the heart for later retrieval and review to aid in diagnosing a cardiac arrhythmia condition of the patient, a method for recording such EGM episode data that may be corrupted by ambient electrical noise comprising the steps of:

continuously sampling the cardiac EGM and providing a sequence of EGM sample values;

determining if the sequence of EGM sample values is corrupted with noise or is relatively noise free and designating the sequence of EGM sample values as noisy EGM episode data or noise free EGM episode data in response to the determination;

storing the noisy EGM episode data in a noisy storage register designated to only receive EGM sample values determined to be corrupted by noise; and

storing the noise free EGM episode data in a noise free storage register designated to only receive sample EGM values determined to be relatively noise free.

18. The method of claim 17, wherein the number of noisy and relatively noise free storage registers of the implantable medical device are limited, and wherein said storing steps further comprise:

storing the noisy EGM episode data in a designated noisy storage register on a FIFO basis, whereby the oldest sequence of noisy EGM episode data is deleted if the noisy storage registers are already filled with noisy EGM episode data; and

storing the noise free EGM episode data in a designated noise free storage register on a FIFO basis, whereby the oldest sequence of noise free EGM episode data is deleted if the noise free storage registers are already filled with noise free EGM episode data.

19. The method of claim 18, further comprising the steps of:

comparing a sequence of the EGM sample values to arrhythmia detection criteria of one or more tachyarrhythmia condition of interest; and

commanding the storage of the EGM episode data in a storage register when a sequence of the EGM sample values satisfy the detection criteria.

20. The method of claim 18, further comprising the step of:

receiving a patient initiated storage command originating externally to the patient'"'"'s body and commanding the storage of the EGM episode data in a storage register.

21. In an implantable medical device adapted to be implanted in a patient and operated to record EGM episode data of the heart for later retrieval and review to aid in diagnosing a cardiac arrhythmia condition of the patient, apparatus for recording such EGM episode data that may be corrupted by ambient electrical noise comprising:

means for continuously sampling the cardiac EGM and providing EGM sample values;

a data memory comprising at least one noisy storage register designated to only receive EGM sample values determined to be corrupted by noise and at least one noise free storage register designated to only receive EGM sample values determined to be relatively noise free;

means for temporarily storing a sequence of the EGM sample values;

means for determining if the temporarily stored sequence of EGM sample values is corrupted with noise or is relatively noise free and designating the sequence of EGM sample values as noisy EGM episode data or noise free EGM episode data, respectively, in response to the determination;

means for storing the noisy EGM episode data in a noisy storage register; and

means for storing the noise free EGM episode data in a noise free storage register.

22. The apparatus of claim 21, wherein:

said data memory comprises a plurality of noisy and relatively noise free storage registers, and

said storing means further comprise;

means for storing the noisy EGM episode data in a designated noisy storage register on a FIFO basis, whereby the oldest sequence of noisy EGM episode data is deleted if the noisy storage registers are already filled with noisy EGM episode data; and

means for storing the noise free EGM episode data in a designated noise free storage register on a FIFO basis, whereby the oldest sequence of noise free EGM episode data is deleted if the noise free storage registers are already filled with noise free EGM episode data.

23. The apparatus of claim 22, further comprising:

means for comparing the temporarily stored sequence of EGM sample values to arrhythmia detection criteria of one or more tachyarrhythmia condition of interest; and

means responsive to the comparing means for commanding the storage of the temporarily stored sequence of EGM sample values by said storing means in a determined one of said noisy or noise free storage registers when a sequence of the EGM sample values satisfy the detection criteria.

24. The apparatus of claim 22, further comprising:

means responsive to a patient initiated storage command originating externally to the patient'"'"'s body for commanding the storage of the temporarily stored EGM sample values by said storing means in a determined one of said noisy or noise free storage registers.

25. The apparatus of claim 21, further comprising:

means for comparing the temporarily stored sequence of EGM sample values to arrhythmia detection criteria of one or more tachyarrhythmia condition of interest; and

means responsive to the comparing means for commanding the storage of the temporarily stored sequence of EGM sample values by said storing means in a determined one of said noisy or noise free storage registers when a sequence of the EGM sample values satisfy the detection criteria.

26. The apparatus of claim 21, further comprising:

means responsive to a patient initiated storage command originating externally to the patient'"'"'s body for commanding the storage of the temporarily stored EGM sample values by said storing means in a determined one of said noisy or noise free storage registers.