METHODS AND APPARATUS FOR MONITORING P-WAVE DURATION AND END AND QRS DURATION WITH AN IMPLANTABLE MEDICAL DEVICE

• US 20090234412A1
• Filed: 03/13/2008
• Published: 09/17/2009
• Est. Priority Date: 03/13/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: SAMBELASHVILI, Aleksandre T.
• Granted Patent: US 9,566,013 B2
• Time in Patent Office: Days
• US Class Current: 607/25
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/353 Detecting P-waves
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/37258 Alerting the patient

Abstract

Novel methods and apparatus for dynamically monitoring paced and sensed P-wave duration, P-wave end and/or QRS duration and/or S-T segment duration, or length, in a patient having an implantable medical device (IMD) provides diagnostic and clinical benefit allowing for predictions about future arrhythmia, advanced notification, alert and intervention as well as providing acute and chronic information regarding cardiac status, including both possibly declining and/or improving cardiac function. The methods can be performed using a wide variety of IMDs, such as pacemakers, cardiac resynchronization therapy (CRT) device, implantable cardioverter defibrillators (ICDs), and implantable loop recorders (e.g., such as the REVEALS device manufactured by Medtronic, Inc.).

Claims

1. An apparatus for monitoring a subject, comprising:

means for sensing an intrinsic or a paced atrial event of a subject with a pair of electrodes coupled to an IMD;

means for collecting a first portion of a PQRST signal with the pair of electrodes;

means for filtering the first portion of the PQRST signal (band pass);

means for calculating a time derivative of the first portion of the PQRST signal;

means for rectifying the derivative signal;

means for locating at least one peak for the rectified signal (maximum amplitude or near-maximum amplitude);

means for setting a reference threshold based at least in part upon the amplitude of the rectified signal; and

means for translating a temporal window (10-20 ms) from the at least one peak;

means for declaring that the end of a P-wave (PWend) has been located when the rectified signal within the translated temporal window has sub-threshold values; and

means for measuring a P-wave duration (PWd) defined as the time elapsed between the detected atrial event and the PWend; and

means for one of storing the PWd in a memory structure of an IMD and comparing the measured duration to a previously measured PWd value of the subject.

2. An apparatus according to claim 1, further comprising:

means for automatically measuring a duration of a QRS complex (QRSd) of the subject; and

means for one of storing within the IMD and comparing within the IMD the measured QRSd to a previously measured QRSd.

3. An apparatus according to claim 2, wherein in the event that at least one of the PWd and QRSd have differing values than a prior value, then:

activating means for storing at least a portion of a recently captured portion of temporal cardiac activity of the subject in a memory structure.

4. An apparatus according to claim 3, further comprising:

means for providing the stored portion of a recently captured portion of temporal cardiac activity to a remote device.

5. An apparatus according to claim 1, further comprising:

means for measuring a P-wave end-time metric (PWend) relative to an atrial sensed or paced event (As or Ap); and

means for comparing the PWend value to a prior PWend value and in the event that the PWend value is one of acutely different or trending from a prior PWend value.

6. An apparatus according to claim 1, wherein the PWd is measured from a far-field subcutaneous electrode array (SEA).

7. A method of monitoring a subject and automatically measuring the duration of the P-Wave (PWd) of a subject via an implantable medical device (IMD), comprising:

sensing an intrinsic or a paced atrial event of a subject with a pair of electrodes coupled to an IMD;

collecting a first portion of a PQRST signal with the pair of electrodes;

filtering the first portion of the PQRST signal;

calculating a time derivative of the first portion of the PQRST signal;

rectifying the derivative signal;

locating at least one peak for the rectified signal;

setting a reference threshold based at least in part upon the amplitude of the rectified signal; and

translating a temporal window (10-20 ms) from the at least one peak;

declaring that the end of a P-wave (PWend) has been located when the rectified signal within the translated temporal window has sub-threshold values; and

measuring a P-wave duration (PWd) value as the time elapsed between the detected atrial event and PWend; and

one of storing the PWd in a memory structure of the IMD and comparing within the IMD the PWd value to a previously measured PWd value of the subject.

8. A method according to claim 7, further comprising:

measuring a duration of a QRS complex (QRSd) of the subject; and

one of storing and comparing the measured QRS duration to a previously measured QRSd value in a CRT delivery device.

9. A method according to claim 8, wherein in the event that at least one of the PWd and QRSd are longer in duration than a prior value, then:

storing at least a portion of a recently captured portion of temporal cardiac activity of the subject in a memory structure.

10. A method according to claim 9, further comprising:

providing the stored portion of a recently captured portion of temporal cardiac activity to a remote device.

11. A method according to claim 7, further comprising:

measuring a P-wave end-time metric (PWend) relative to an atrial sensed or paced event (As or Ap);

comparing the PWend value to a prior PWend value and in the event that the PWend value is one of acutely different or trending from a prior PWend value then either providing a notification via telemetry to a remote device or storing the measured values in a memory structure.

12. A method according to claim 7, wherein the PWd is measured from a far-field subcutaneous electrode array (SEA).

13. A method according to claim 7, wherein the PWd metric is measured via a temporary pacing and sensing lead in electrical communication with the heart.

14. A method according to claim 7, wherein the PWd metric is measured via a chronic pacing and sensing lead in direct communication with the heart.

15. A method according to claim 7, wherein the PWd metric is measured via a subcutaneous cardiac sensing array in a position spaced from, but in electrical communication with, the heart.

16. A method according to claim 7, wherein the heart rate excursion is measured via at least one surface sensing electrode in communication with the heart.

17. A method according to claim 7, wherein the PWd metric is measured via a temporary pacing lead in communication with the heart.

18. A computer readable medium for storing executable instructions operable under computer processor control to monitor a subject, comprising:

instructions for sensing an intrinsic or a paced atrial event with a pair of electrodes coupled to an IMD;

instructions for collecting a first portion of a PQRST signal with the pair of electrodes;

instructions for filtering the first portion of the PQRST signal (band pass);

instructions for calculating a time derivative of the first portion of the PQRST signal;

instructions for rectifying the derivative signal;

instructions for locating at least one peak for the rectified signal (maximum amplitude or near-maximum amplitude);

instructions for setting a reference threshold based at least in part upon the amplitude of the rectified signal; and

instructions for translating a temporal window (10-20 ms) from the at least one peak;

instructions for declaring that the end of a P-wave (PWend) has been located when the rectified signal within the translated temporal window has sub-threshold values; and

instructions for measuring the time elapsed between the detected atrial event and PWend as the P-wave duration (PWd) and instructions for one of storing the PWd in a memory structure of an IMD and comparing the measured duration to a previously measured PWd value of the subject.

19. A computer readable medium according to claim 19, further comprising:

instructions for automatically measuring a duration of a QRS complex (QRSd) of the subject; and

instructions for one of storing and comparing the measured QRS duration to a previously measured QRSd value in the IMD.

20. An apparatus for monitoring a subject, comprising

at least a pair of electrodes adapted for sensing an intrinsic or a paced atrial event of a subject with a pair of electrodes coupled to an implantable medical device (IMD):

a processor adapted to collect a first portion of a PQRST signal with the pair of electrodes;

a band-pass filter coupled to processor adapted to filter at least the first portion of the PQRST signal and provide a filtered output signal;

circuitry adapted to calculate a time derivative of the first portion of the PQRST signal and provide a derivative signal;

a rectifying circuit coupled to the circuitry to receive the derivative signal and produce a rectified signal of said derivative signal;

means for locating at least one peak for the rectified signal at a maximum amplitude or a near-maximum amplitude of the rectified signal and for providing a reference threshold based at least in part upon the amplitude of the rectified signal;

means for translating a temporal window (10-20 ms) from the at least one peak;

means for declaring that the end of a P-wave (PWend) has been located when the rectified signal within the translated temporal window has sub-threshold values; and

a timer adapted to measure a P-wave duration (PWd) as defined by the time elapsed between the detected atrial event and the PWend;

a memory structure disposed within the IMD for storing the PWd; and

a comparator circuit coupled to the memory structure adapted to compare the measured PWd to a previously measured PWd value of the subject.