SYSTEM AND METHOD FOR DISCRIMINATING HYPERVOLEMIA, HYPOVOLEMIA AND EUVOLEMIA USING AN IMPLANTABLE MEDICAL DEVICE

• US 20130165802A1
• Filed: 12/21/2011
• Published: 06/27/2013
• Est. Priority Date: 12/21/2011
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Rosenberg, Stuart, Dalal, Yousuf
• Granted Patent: US 9,332,913 B2
• Time in Patent Office: Days
• US Class Current: 600/486
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: A61N 1/3962 in combination with another heart therapy
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Techniques are provided for use by an implantable medical device or diagnostic sensor for detecting and discriminating euvolemia, hypervolemia and hypovolemia. In one example, the device detects a pressure signal within the patient representative of changes in cardiac pressure overall several cardiac cycles. The device generates separate time-domain and frequency-domain representations of the pressure signal and then discriminates among euvolemia, hypervolemia and hypovolemia within the patient based on an analysis of the time-domain and the frequency-domain representations of the signal. Depending upon the capabilities of the device, suitable warnings may be generated to alert the patient or caregiver. Diuretics or other medications can be titrated to address abnormal fluid conditions such as a fluid overload during hypervolemia. Techniques for detecting a pressure alternans pattern indicative of imminent decompensation are also described.

Claims

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

detecting a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

generating separate time-domain and frequency-domain representations of the pressure signal; and

discriminating among euvolemia, hypervolemia and hypovolemia within the patient based on the time-domain and the frequency-domain representations of the pressure signal.

2. The method of claim 1 wherein detecting the time-varying pressure signal includes detecting one or more of left ventricular pressure (LVP), left atrial pressure (LAP) or pulmonary artery pressure (PAP.)

3. The method of claim 1 wherein discriminating euvolemia, hypervolemia and hypovolemia includes:

identifying an ejection period of the cardiac cycle within the time-domain representation of the pressure signal;

assessing a shape of the time-domain representation of the pressure signal during the ejection period; and

discriminating hypervolemia from hypovolemia and euvolemia based on the shape of the time-domain representation of the pressure signal during the ejection period.

4. The method of claim 3 wherein discriminating hypervolemia from hypovolemia and euvolemia includes:

generating an indication of hypervolemia if the time-domain representation of the pressure signal during the ejection period has a relatively peaked shape; and

generating an indication of lack of hypervolemia if the time-domain representation of the pressure signal during the ejection period has a relatively more rounded shape.

5. The method of claim 3 wherein identifying the ejection period includes:

determining first order derivatives (dP/dt) and second order derivatives (d²P/dt²) of the time-domain representation of the pressure signal;

identifying fiducial markers within the time-domain representation of the pressure signals based on the first and second order derivatives including;

a maximum magnitude of dP/dt (dP/dt max);

a time of dP/dt max;

a minimum magnitude of dP/dt (dP/dt min);

a time of dP/dt min;

a peak magnitude of the pressure (P max);

a time of P max; and

a minimum magnitude of d²P/dt²; and

identifying the ejection period as the interval between the time of minimum d²P/dt² after dP/dt max and the time of minimum d²P/dt² before dP/dt min.

6. The method of claim 3 wherein assessing the shape of the time-domain representation of the pressure signal during the ejection period includes generating a shape index representative of a degree of roundness to the time domain representation of the pressure signal during the ejection period.

7. The method of claim 6 wherein the shape index is generated based on one or more of a best-fit quadratic curve or a best-fit cosine curve.

8. The method of claim 1 wherein discriminating euvolemia, hypervolemia and hypovolemia includes:

identifying a maximum rate of change (dP/dt max) of the time domain representation of the pressure signal;

identifying a minimum rate of change (dP/dt min) of the time domain representation of the pressure signal;

identifying a maximum pressure value (P max) within the time domain representation of the pressure signal;

determining a time of P max relative to dP/dt max and dP/dt min; and

discriminating hypervolemia from hypovolemia and euvolemia based on the time of P max relative to dP/dt max and dP/dt min.

9. The method of claim 8 wherein discriminating hypervolemia from hypovolemia and euvolemia includes:

generating an indication of hypervolemia if P max is relatively early; and

generating an indication of lack of hypervolemia if P max is relatively late.

10. The method of claim 1 wherein discriminating euvolemia, hypervolemia and hypovolemia includes:

identifying power spectra peaks within the frequency-domain representation of the pressure signals associated with the heart rate and its harmonics;

assessing a distribution of signal power relative to the peaks; and

discriminating euvolemia from hypovolemia and hypervolemia based on the distribution of signal power relative to the peaks.

11. The method of claim 10 wherein euvolemia from hypovolemia and hypervolemia includes:

generating an indication of euvolemia if signal power is relatively diffused from the peaks; and

generating an indication of an abnormal volemic state if the signal power is relatively concentrated at the power spectra peaks.

12. The method of claim 10 wherein assessing the distribution of signal power includes determining widths of the power spectra peaks and associating relatively narrow widths with a concentration of power and associating relatively greater widths with a diffusion of power.

13. The method of claim 1 wherein discriminating euvolemia, hypervolemia and hypovolemia includes:

identifying a first power spectra peak within the frequency-domain representation of the pressure signals associated with heart rate;

determining a frequency of the first power spectra peak;

associating a higher frequency of the first power spectra peak with hypervolemia; and

associating a lower frequency of the heart rate peak with a lack of hypervolemia.

14. The method of claim 1 wherein discriminating euvolemia, hypervolemia and hypovolemia includes:

identifying first and second power spectra peaks within the frequency-domain representation of the pressure signals;

determining relative magnitudes of the first and second peaks; and

detecting pressure alternans based on the relative magnitudes of the first and second peaks.

15. The method of claim 14 wherein detecting pressure alternans based on the relative magnitudes of the first and second peaks includes:

determining a ratio of the magnitude of the second peak to the first peak; and

detecting pressure alternans if the ratio exceeds a threshold indicative of pressure alternans.

16. The method of claim 15 further including generating a warning indicative of heart failure decompensation in response to detection of pressure alternans.

17. The method of claim 1 wherein discriminating among euvolemia, hypervolemia and hypovolemia includes:

identifying an ejection period of the cardiac cycle within the time-domain representation of the pressure signals and assessing a characteristic shape of the pressure signal during the ejection period;

identifying power spectra peaks within the frequency-domain representation of the pressure signals associated with the heart rate and its harmonics and assessing a distribution of signal power relative to the peaks;

detecting hypervolemia based on a relatively peaked shape to the time-domain representation of the pressure signal during the ejection period along with a concentration of signal power at the power spectra peaks of the frequency-domain representation of the pressure signal; and

detecting hypovolemia based on a relatively rounded shape to the time-domain representation of the pressure signal during the ejection period along with a concentration of signal power at the power spectra peaks of the frequency-domain representation of the pressure signal; and

detecting euvolemia based on a relatively rounded shape to the time-domain representation of the pressure signal during the ejection period along with a relatively more diffused signal power within the frequency-domain representation of the pressure signal.

18. The method of claim 1 wherein discriminating among euvolemia, hypervolemia and hypovolemia includes generating a likelihood score based on the time-domain and the frequency-domain representations of the pressure signal.

19. The method of claim 1 further including controlling at least one device function in response to the discrimination among euvolemia, hypervolemia and hypovolemia.

20. The method of claim 19 wherein controlling at least one device function includes titrating a dosage of diuretics in response to the discrimination among euvolemia, hypervolemia and hypovolemia.

21. The method of claim 19 herein controlling at least one device function includes generating warning signals in response to an abnormal volemic state.

22. The method of claim 1 further including detecting an indication of one or more of fluid overload, pulmonary edema and heart failure based on the discrimination of euvolemia, hypervolemia and hypovolemia.

23. The method of claim 22 wherein, in response to an indication of significant hypervolemia, the device performs one of or more of:

adjusting pacing vectors;

preparing for delivery of a defibrillation shock;

adjusting pacing therapy parameters including one or more of pacing location, pacing mode, pacing sequence, number of ventricular pulses, atrioventricular delay, interventricular delay, and intraventricular delay.

24. The method of claim 1 wherein all of the steps are performed by th 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 cardiac pressure detector operative to detect a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

a time-domain and frequency-domain processing system operative to generate separate time-domain and frequency-domain representations of the pressure signal; and

a discrimination system operative to discriminate among euvolemia, hypervolemia and hypovolemia within the patient based on the time-domain and frequency-domain representations of the pressure signal.

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

means for detecting a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

means for generating separate time-domain and frequency-domain representations of the pressure signal; and

means for discriminating among euvolemia, hypervolemia and hypovolemia within the patient based on the time-domain and the frequency-domain representations of the pressure signal.

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

detecting a time-varying pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

identifying an ejection period of the cardiac cycle within the pressure signal;

assessing a shape of the pressure signal during the ejection period; and

discriminating hypervolemia from a lack of hypervolemia within the patient based on the shape of the pressure signal during the ejection period.

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

detecting a time-varying pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

generating a frequency-domain representation of the pressure signal;

identifying power spectra peaks within the frequency-domain representation of the pressure signal associated with the heart rate and its harmonics and assessing a distribution of signal power relative to the peaks; and

discriminating abnormal volemic states from euvolemia within the patient based on the distribution of signal power within the frequency-domain representation of the pressure signal.

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

detecting a time-varying pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

generating a frequency-domain representation of the pressure signal;

identifying first and second power spectra peaks within the frequency-domain representation of the pressure signals;

determining relative magnitudes of the first and second peaks; and

detecting pressure alternans based on the relative magnitudes of the first and second peaks.