Method and apparatus for monitoring heart rate and abnormal respiration

• US 6,752,765 B1
• Filed: 11/17/2000
• Issued: 06/22/2004
• Est. Priority Date: 12/01/1999
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Jensen, Donald N., Ruetz, Linda L., Davie, Scott, Strobel, Ulla, Condie, Catherine R., Cho, Yong Kyun
• Primary Examiner(s): Schaetzle, Kennedy
• Assistant Examiner(s): DROESCH, KRISTEN L
• Application Number:
  US09/715,637
• Time in Patent Office: 1,313 Days
• Field of Search: 600/483-484, 600/509, 600/510, 600/513, 600/519, 600/529, 600/534, 600/536, 600/547, 607/4-6, 607/9, 607/17-20, 607/25, 607/27
• US Class Current: 600/536
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

An implantable device having enhanced capabilities for monitoring a patient'"'"'s heart rate and respiration trends over extended periods of time is disclosed. The information collected by the implantable device may be stored and telemetered to an associated external device such as a device programmer for display and analysis. Heart rates are measured by measuring the time intervals between sensed depolarizations of a chamber of the patient'"'"'s heart and preceding sensed depolarizations or delivered pacing pulses. Intervals may be measured in the ventricle and/or atrium of the patient'"'"'s heart. According to another aspect of the invention, an implanted impedance sensor is employed to monitor minute ventilation. The heart rate and minute ventilation data is used to develop long-term trend data used for diagnostic purposes. In one embodiment of the invention, heart interval and minute ventilation measurements are taken only during defined time periods of the night and/or day when the patient is at rest. A sensor such as an activity sensor or metabolic rate sensor may be used to confirm patient inactivity.

Claims

1. A method for diagnosing patient condition using an implantable medical device, comprising the steps of:

a.) obtaining intra-thoracic tissue impedance measurements utilizing an implanted impedance sensor;

b.) generating numerical values indicative of trends in minute ventilation from the impedance measurements

c.) measuring cardiac intervals; and

d.) correlating said measured cardiac intervals to said generated numerical values to provide an initial assessment of a cardiac status of the patient;

wherein method step a.) includes obtaining tissue impedance measurements only during at least one predetermined time period each day.

2. The method of claim 1, wherein the at least one predetermined time period of method a.) is approximately from 12:

00 am to 2;

00 am.

8. The device according to claim 1, wherein the processing circuit includes a timing circuit to define monitoring periods during at least a part of the predetermined schedule and for which the processing circuit will use the signal indicative of tissue impedance to generate the numerical values indicative of trends in minute ventilation;

and wherein said measured intervals further comprise at least one of the following;

a P-P interval, a P-R interval, an R-P interval, an R-R interval.

9. The device according to claim 8, wherein the timing circuit includes means to define the monitoring periods as occurring during successive nights substantially between 12:

00 a.m. and 2;

00 a.m.

10. The device according to claim 1, and further including a storage device coupled to the processing circuit to store the numerical values indicative of trends in minute ventilation and the measured values indicative of heart rate.

11. The device according to claim 1, and further including a pulse generator coupled to the processing circuit to generate electrical stimulation signals to be provided to the patient, and whereby the pulse generator is capable of modifying the electrical stimulation signals in response to the numerical values indicative of trends identified from the correlation of minute ventilation to the measured intervals indicative of heart rate and wherein said pulse generator comprises at least a one of the following:

a bi-ventricular pacing engine, a single-chamber pacemaker, a dual-chamber pacemaker.

12. The device according to claim 1, further comprising means for determining if the numerical values correlate the measured intervals to the presence of breathing trends.

13. The device according to claim 12, and further including a communication circuit coupled to the processing circuit to transfer any of the correlated numerical values indicative of trends in minute ventilation or any of the measured intervals indicative of heart rate to a location external to the device.

14. The device according to claim 13, and further including a programmer coupled to the device and wherein the programmer includes a display to display any of the numerical values indicative of trends in minute ventilation, any of the measured intervals indicative of heart rate, or any correlation therebetween, to a user.

15. The device according to claim 14, wherein at least a portion of the analyzing means is provided by the programmer.

16. The device according to claim 15, wherein the analyzing means includes means for identifying Cheyne-Stokes respiration based at least in part upon any of the numerical values indicative of trends in minute ventilation, any of the measured intervals indicative of heart rate, or any correlation therebetween.

17. The device according to claim 1, and further including an alarm coupled to the processing circuit to provide a notification that the numerical values indicative of trends in minute ventilation, and any of the measured intervals indicative of heart rate, or any correlation therebetween appear to be indicative of one or more predetermined conditions.

18. The device according to claim 1, and further including a metabolic sensor to measure metabolic demand for the patient, and wherein the processing circuit further includes means to generate from the measured metabolic demand numerical values indicative of a cardiac condition.

19. The device according to claim 1, and further including an activity-based sensor to indicate when a patient is relatively stationary, said activity-based sensor coupled to the processing circuit, and whereby the numerical values indicative of trends in minute ventilation are generated only for an impedance signal measured when the patient is at rest.

20. The device according to claim 19, wherein the processing circuit further includes means to discard any ones of the measured heart intervals that have a temporal length tending to indicate the presence of a tachycardia condition.

21. The device according to claim 1, wherein the trends correspond to a first time period of increased minute ventilation relative to a second time period of reduced minute ventilation, and wherein the patient is determined to be undergoing a predetermined breathing pattern in response to the trends.

22. The device according to claim 21, wherein the predetermined breathing pattern corresponds to a Cheyne-Stokes respiration pattern.

3. A method for diagnosing patent condition using an implantable medical device, comprising the steps of:

a.) obtaining intra-thoracic tissue impedance measurements utilizing an implanted impedance sensor;

b.) generating numerical values indicative of trends in minute ventilation from the impedance measurements

c.) measuring cardiac intervals;

d.) correlating said measured cardiac intervals to said generated numerical values to provide an initial assessment of a cardiac status of the patient; and

further including the step of

e.) obtaining a determination that the patient relatively stationary, and wherein method step a.) is performed only for time periods when the patient is determined to be relatively stationary.

4. A method for diagnosing patient condition using an implantable medical device, comprising the steps of:

a.) obtaining intra-thoracic tissue impedance measurements utilizing an implanted impedance sensor;

b.) generating numerical values indicative of trends in minute ventilation from the impedance measurements

c.) measuring cardiac intervals;

d.) correlating said measured cardiac intervals to said generated numerical values to provide an initial assessment of a cardiac status of the patient;

and further including the steps of

e.) utilizing the initial assessment of step d.) to determine whether to perform the following additional step;

f.) activating an alert apparatus about the initial assessment.

5. The method of claim 4, and further including the step of:

g.) displaying information derived from the initial assessment.

6. The method of claim 5, and further including the steps of:

h.) obtaining a measurement of a present state of metabolic demand for the patient; and

i.) porting said measurements to the processing circuit to obtain at least one piece of data indicative of whether any correlation exists between the initial assessment and the present state of metabolic demand for the patient.

7. A device, comprising:

an impedance sensor to provide an impedance signal indicative of tissue impedance pursuant to a predetermined schedule;

a processing circuit coupled to the impedance sensor to receive the signal indicative of tissue impedance, and to generate therefrom, numerical values indicative of temporal trends in minute ventilation based at least in part on the predetermined schedule; and

a means for measuring intervals indicative of a heart rate of a patient and for correlating said measured intervals to the numerical values or the temporal trends in minute ventilation.