Method and apparatus for trending a physiological cardiac parameter

• US 8,340,747 B2
• Filed: 09/21/2010
• Issued: 12/25/2012
• Est. Priority Date: 06/25/2003
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Goode, Paul V. Jr.
• Primary Examiner(s): Holmes, Rex R
• Application Number:
  US12/887,273
• Publication Number:
  US 20110009767A1
• Time in Patent Office: 826 Days
• Field of Search: 600/509, 607/17, 607/27, 607/122
• US Class Current: 600/509
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/4035 Evaluating the autonomic nervous system

Abstract

The present invention relates to an implantable cardioverter-defibrillator or pacemaker whose standard circuitry is used to trend a physiological cardiac parameter using intra-cardiac impedance measurements. The trend information may be used to predict the onset of a sudden cardiac death (SCD) event. By being able to predict the onset of an SCD event, patients and their physicians may be forewarned of a life-threatening event allowing them to respond accordingly. The trend information may also be used to predict the efficacy of cardiac-related medications, monitor progress of congestive heart failure, detect the occurrence of myocardial infarction, or simply track changes in sympathetic tone.

Claims

1. A system for monitoring congestive heart failure, the system comprising:

a measuring device configured to measure, using a lead, intra-cardiac impedance of a patient when the patient is typically sleeping;

a derivation module configured to;

derive a physiologic cardiac parameter from the measured impedance, the derived parameter including at least one of stroke volume, ejection fraction, and pre-ejection period; and

derive sympathetic activity from the physiologic cardiac parameter;

a trending module configured to trend the derived sympathetic activity over spaced time intervals to create trended sympathetic activity data; and

an analyzing module configured to analyze the trended sympathetic activity data to monitor congestive heart failure status from the analysis.

2. The system of claim 1, wherein the analyzing module is configured to:

compare the trended sympathetic activity data; and

detect a difference between the trended sympathetic activity data.

3. The system of claim 1, comprising a reporting module configured to report the trended sympathetic activity data to an outside source.

4. The system of claim 1, wherein the derivation module and the trending module are packaged with an implantable device.

5. The system of claim 1, comprising an external device configured to store the trended sympathetic activity data.

6. The system of claim 1, comprising a separately located device, wherein the system is configured to download the trended sympathetic activity data to the separately located device.

7. The system of claim 6, wherein the separately located device includes an external patient management system.

8. The system of claim 1, wherein the measuring device is configured to measure intra-cardiac impedance using an implantable cardiac rhythm management device.

9. The system of claim 1, wherein the measuring device is coupled to at least two electrodes configured to measure a voltage resulting from a current applied between the at least two electrodes, wherein the voltage is used to determine the intra-cardiac impedance.

10. A device for trending sympathetic activity, the device comprising:

an impedance module configured to measure, using a lead, an intra-cardiac impedance of a patient at spaced time intervals when the patient is typically sleeping;

a derivation module configured to;

derive a physiologic cardiac parameter from the measured impedance, the derived parameter including at least one of stroke volume, ejection fraction, and pre-ejection period; and

derive the sympathetic activity using the physiologic cardiac parameter;

a trending module configured to generate trended sympathetic activity data using the derived sympathetic activity; and

an analyzing module configured to analyze the trended sympathetic activity data to monitor congestive heart failure status from the analysis.

11. The device of claim 10, comprising a reporting module configured to report the trended sympathetic activity data to an outside source.

12. The device of claim 10, wherein the impedance module is in communication with at least two electrodes, the at least two electrodes being configured to measure a voltage resulting from a current applied between the at least two electrodes, wherein the voltage is used to determine the intra-cardiac impedance.

13. The device of claim 10, wherein the device is configured to download the trended sympathetic activity data to an external storage device.

14. A device-readable medium comprising instructions that, when performed by a previously-implanted medical device, cause the device to perform acts comprising:

measuring, using a lead, an intra-cardiac impedance of a patient at spaced time intervals when the patient is typically sleeping;

deriving a physiologic cardiac parameter from the measured impedance, the derived parameter including at least one of stroke volume, ejection fraction, and pre-ejection period;

deriving sympathetic activity using the physiologic cardiac parameter;

generating trended sympathetic activity data using the derived sympathetic activity;

analyzing the trended sympathetic activity data; and

monitoring congestive heart failure status from the analysis.

15. The device-readable medium of claim 14, wherein analyzing the trended sympathetic activity data includes:

comparing the trended sympathetic activity data; and

detecting a difference between the trended sympathetic activity data.

16. The device-readable medium of claim 14, comprising instructions that, when performed by the previously-implanted medical device, cause the device to perform acts comprising reporting the trended sympathetic activity data to an outside source.

17. The device-readable medium of claim 14, comprising instructions that, when performed by the previously-implanted medical device, cause the device to perform acts comprising storing the trended sympathetic activity data on an external device.