SYSTEM AND METHOD FOR DETECTING PULMONARY CONGESTION BASED ON STROKE VOLUME USING AN IMPLANTABLE MEDICAL DEVICE

• US 20130184545A1
• Filed: 01/12/2012
• Published: 07/18/2013
• Est. Priority Date: 01/12/2012
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Blomqvist, Andreas, Soriano, Alex
• Granted Patent: US 9,049,995 B2
• Time in Patent Office: Days
• US Class Current: 600/325
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/29 for permanent or long-term implantation
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36564 controlled by blood pressure

Abstract

Techniques are provided for detecting pulmonary congestion based on an increase in right ventricular (RV) stroke volume over left ventricular (LV) stroke volume. In one example, the device generates an index based on accumulated differences between RV stroke volume and LV stroke volume while RV stroke volume exceeds LV stroke volume, such that the index is indicative of an ongoing imbalance between RV and LV stroke volume. The index is compared to a suitable threshold to detect a severe imbalance indicative of pulmonary edema. Additionally, techniques are described for estimating RV and LV stroke volumes based on pulmonary artery pressure, left atrial pressure, aortic pressure, LV strain or on various intracardiac or extracardiac impedance measurements.

Claims

1. A method for use with an implantable medical device for implant within a patient, the method comprising:

detecting values representative of right ventricular (RV) stroke volume within the patient;

detecting values representative of left ventricular (LV) stroke volume within the patient;

evaluating differences between the RV stroke volume values and the LV stroke volume values; and

detecting an indication of pulmonary congestion based on differences, if any, between the RV stroke volume values and the LV stroke volume values.

2. The method of claim 1 wherein detecting values representative of RV stroke volume within the patient includes detecting pulmonary artery pressure signals.

3. The method of claim 2 further including estimating RV stroke volume from the pulmonary artery pressure signals.

4. The method of claim 3 wherein estimating RV stroke volume from the pulmonary artery pressure signals includes calculating:

5. The method of claim 1 wherein detecting values representative of RV stroke volume within the patient includes detecting impedance signals affected by RV stroke volume and estimating RV stroke volume from the impedance signals.

6. The method of claim 5 wherein detecting impedance signals and estimating RV stroke volume from the impedance signals includes:

injecting current along a vector between a right atrial (RA) ring electrode and a RV ring vector;

measuring impedance along a vector between an RA tip electrode and a an RV tip electrode;

detecting peak-to-peak variations in the measured impedance; and

converting the peak-to-peak variations to RV stroke volume values using at least one predetermined conversion factor.

7. The method of claim 1 wherein detecting values representative of LV stroke volume within the patient includes detecting impedance signals affected by LV stroke volume and estimating LV stroke volume from the impedance signals.

8. The method of claim 7 wherein detecting impedance signals and estimating LV stroke volume from the impedance signals includes:

measuring impedance along a vector affected by blood flow through the aorta of the patient;

detecting variations in the measured impedance influenced by LV stroke volume; and

converting the variations in impedance to LV stroke volume using at least one predetermined conversion factor.

9. The method of claim 8 wherein the vector passing through the aorta of the patient is a vector between a superior vena cava (SVC) coil electrode and a device housing electrode.

10. The method of claim 1 wherein the detecting values representative of LV stroke volume includes detecting values representative of left atrial pressure (LAP) and detecting a maximum positive rate of change in the LAP values.

11. The method of claim 10 further including estimating LV stroke volume from the maximum positive rate of change in the LAP values using at least one predetermined conversion factor.

12. The method of claim 1 wherein the detecting values representative of LV stroke volume includes detecting strain gauge values from an LV strain gauge sensor representative of changes in the curvature of the ventricular epicardium.

13. The method of claim 12 further including estimating LV stroke volume from the strain gauge values using at least one predetermined conversion factor.

14. The method of claim 1 wherein the detecting values representative of LV stroke volume within the patient includes detecting S_VO₂ values from an oxygen saturation sensor.

15. The method of claim 14 further including estimating LV stroke volume from the S_VO₂ values using at least one predetermined conversion factor.

16. The method of claim 1 wherein the detecting values representative of LV stroke volume within the patient includes detecting aortic pressure signals.

17. The method of claim 16 further including estimating LV stroke volume from the aortic pressure signals.

18. The method of claim 1 wherein evaluating differences between the RV stroke volume values and the LV stroke volume values is performed during an interval of time while the RV stroke volume values exceed the LV stroke volume values.

19. The method of claim 18 wherein evaluating differences between the RV stroke volume values and the LV stroke volume values includes calculating an accumulated difference while the RV stroke volume values exceed the LV stroke volume values.

20. The method of claim 19 wherein calculating the accumulated difference between the RV stroke volume values and the LV stroke volume values includes generating an edema index representative of the accumulated difference while the RV stroke volume values exceed the LV stroke volume values by at least a minimal amount (δ

).

21. The method of claim 20 wherein detecting an indication of pulmonary congestion includes comparing the edema index to a threshold (Θ

) indicative of pulmonary congestion and generating an indicator signal if the index exceeds the threshold.

22. The method of claim 20 further including:

tracking an interval of time (T) during which the RV stroke volume values exceed the LV stroke volume values by at least a minimal amount (δ

); and

comparing the interval of time (T) against a time threshold (Γ

) and generating an indicator signal if the interval of time exceeds the time threshold.

23. The method of claim 1 further including controlling at least one device function in response to the indication of pulmonary congestion including one or more of:

recording diagnostics, generating a warning, controlling device therapy, controlling delivery of medications, and detecting and trending heart failure.

24. The method of claim 1 wherein all of the steps are performed by the implantable medical device.

25. The method of claim 1 wherein at least some of the steps are performed by an external device in communication with the implantable medical device.

26. A system for use with an implantable medical device for implant within a patient, the system comprising:

a right ventricular (RV) stroke volume detector operative to detect values representative of RV stroke volume within the patient;

a left ventricular (LV) stroke volume detector operative to detect values representative of LV stroke volume within the patient;

an RV/LV stroke volume difference evaluation system operative to evaluate differences between the RV stroke volume values and the LV stroke volume values; and

a pulmonary congestion indicator system operative to detect an indication of pulmonary congestion based on differences, if any, between the RV stroke volume values and the LV stroke volume values.

27. A system for use with an implantable medical device for implant within a patient, the system comprising:

means for detecting values representative of right ventricular (RV) stroke volume within the patient;

means for detecting values representative of left ventricular (LV) stroke volume within the patient;

means for evaluating differences between the RV stroke volume values and the LV stroke volume values; and

means for detecting an indication of pulmonary congestion based on differences, if any, between the RV stroke volume values and the LV stroke volume values.