System and method for discriminating hypervolemia, hypervolemia and euvolemia using an implantable medical device

• US 9,332,913 B2
• Filed: 12/21/2011
• Issued: 05/10/2016
• Est. Priority Date: 12/21/2011
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Dalal, Yousuf, Rosenberg, Stuart
• Primary Examiner(s): Kahelin, Michael
• Assistant Examiner(s): Alter, Mitchell E
• Application Number:
  US13/333,777
• Publication Number:
  US 20130165802A1
• Time in Patent Office: 1,602 Days
• US Class Current: 1/1
• 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:

applying a cardiac pressure detector to detect a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

applying a time-domain and frequency-domain processor to generate separate time-domain and frequency-domain representations of the pressure signal;

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

wherein applying a discrimination system to discriminate euvolemia, hypervolemia and hypovolemia comprises;

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; and

applying a controller unit to control at least one implantable medical device therapeutic function in response to applying a discrimination system to discriminate among euvolemia, hypervolemia and hypovolemia.

2. The method of claim 1 wherein applying a discrimination system to discriminate hypervolemia from hypovolemia and euvolemia comprises:

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

3. The method of claim 1 wherein identifying the ejection period comprises:

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.

4. The method of claim 1 wherein assessing the shape of the time-domain representation of the pressure signal during the ejection period comprises generating a shape index representative of a degree of roundness to the time domain representation of the pressure signal during the ejection period.

5. The method of claim 4 wherein the shape index is generated based on one or more of a best-fit quadratic curve or a best-fit cosine curve.

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

applying a cardiac pressure detector to detect a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

applying a time-domain and frequency-domain processor to generate separate time-domain and frequency-domain representations of the pressure signal; and

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

wherein applying a discrimination system to discriminate euvolemia, hypervolemia and hypovolemia comprises;

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; and

applying a controller unit to control at least one implantable medical device therapeutic function in response to applying a discrimination system to discriminate among euvolemia, hypervolemia and hypovolemia.

7. The method of claim 6 wherein applying a discrimination system to discriminate hypervolemia from hypovolemia and euvolemia comprises:

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

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

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

applying a cardiac pressure detector to detect a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

applying a time-domain and frequency-domain processor to generate separate time-domain and frequency-domain representations of the pressure signal; and

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

wherein applying a discrimination system to discriminate euvolemia, hypervolemia and hypovolemia comprises;

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; and

applying a controller unit to control at least one implantable medical device therapeutic function in response to applying a discrimination system to discriminate among euvolemia, hypervolemia and hypovolemia.

9. The method of claim 8 wherein applying a discrimination system to discriminate euvolemia from hypovolemia and hypervolemia comprises:

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

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

10. The method of claim 8 wherein assessing the distribution of signal power comprises determining widths of the power spectra peaks and associating narrow widths with a concentration of power and associating greater widths with a diffusion of power.

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

applying a cardiac pressure detector to detect a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

applying a time-domain and frequency-domain processor to generate separate time-domain and frequency-domain representations of the pressure signal; and

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

wherein applying a discrimination system to discriminate euvolemia, hypervolemia and hypovolemia comprises;

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; and

applying a controller unit to control at least one implantable medical device therapeutic function in response to applying a discrimination system to discriminate among euvolemia, hypervolemia and hypovolemia.

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

applying a cardiac pressure detector to detect a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

applying a time-domain and frequency-domain processor to generate separate time-domain and frequency-domain representations of the pressure signal; and

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

wherein applying a discrimination system to discriminate euvolemia, hypervolemia and hypovolemia comprises;

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; and

applying a controller unit to control at least one implantable medical device therapeutic function in response to applying a discrimination system to discriminate among euvolemia, hypervolemia and hypovolemia.

13. The method of claim 12 wherein detecting pressure alternans based on the relative magnitudes of the first and second peaks comprises:

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.

14. The method of claim 13 further comprising generating a warning indicative of heart failure decompensation in response to detection of pressure alternans.

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

applying a cardiac pressure detector to detect a pressure signal within the patient representative of changes in cardiac pressure during at least one cardiac cycle;

applying a time-domain and frequency-domain processor to generate separate time-domain and frequency-domain representations of the pressure signal; and

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

wherein applying a discrimination system to discriminate among euvolemia, hypervolemia and hypovolemia comprises;

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 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;

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

applying a controller unit to control at least one implantable medical device therapeutic function in response to applying a discrimination system to discriminate among euvolemia, hypervolemia and hypovolemia.