MEASUREMENT OF CARDIAC CYCLE LENGTH AND PRESSURE METRICS FROM PULMONARY ARTERIAL PRESSURE

• US 20120029365A1
• Filed: 04/25/2011
• Published: 02/02/2012
• Est. Priority Date: 07/28/2010
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Greenhut, Saul E., Bloem, David R., Cho, Yong K., Taepke, Robert T., Salmi, Donna M.
• Granted Patent: US 9,254,091 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/6847 mounted on an invasive device
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/6869 Heart
• CPC Class Codes: A61B 5/6876 Blood vessel
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61M 2205/054 with electrotherapy
• CPC Class Codes: A61M 2210/125 Heart
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/1723 using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: A61N 1/37247 User interfaces, e.g. input or presentation means
• CPC Class Codes: A61N 1/3962 in combination with another heart therapy
• CPC Class Codes: A61N 1/39622 Pacing therapy
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

Various techniques for measuring cardiac cycle length and pressure metrics based on pulmonary artery pressures are described. One example method described includes identifying a point within a derivative signal of a cardiovascular pressure signal without reference to electrical activity of a heart, initiating a time window from the identified point in the derivative signal, identifying a point within the cardiovascular signal within the time window, and determining at least one of a systolic pressure or diastolic pressure based on the identified point.

Claims

1. A method of monitoring a cardiovascular pressure signal in a medical device, comprising:

identifying, by a medical device, a plurality of fiducial points within a derivative signal of a cardiovascular pressure signal without reference to cardiovascular electrical activity; and

identifying, by the medical device, a length of time between consecutive ones of the fiducial points as a cardiac cycle length,

wherein identifying the plurality of fiducial points comprises;

comparing the derivative signal to a threshold;

identifying a point within the derivative signal that satisfies the threshold;

identifying the fiducial point within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold; and

initiating a blanking period that begins at the identified point that satisfies the threshold, and

wherein comparing the derivative signal to the threshold comprises not comparing the derivative signal to the threshold for identification of a subsequent one of the fiducial points during the blanking period.

2. The method of claim 1, wherein identifying the plurality of fiducial points further comprises at least one of:

when the point within the derivative signal satisfies the threshold, verifying that a value of a second derivative signal of the cardiovascular pressure signal is greater than zero; and

prior to the point within the derivative signal satisfying the threshold, verifying that at least one value of the derivative signal of the cardiovascular pressure signal is below the threshold.

3. The method of claim 1, wherein the consecutive ones of the fiducial points comprise one of:

a first sense and a second sense;

a first end-diastolic pressure and a second end-diastolic pressure;

a first peak-systolic pressure and a second peak-systolic pressure;

or

a first maximum value of the first derivative signal of the cardiovascular pressure signal and a second maximum value of the first derivative signal of the cardiovascular pressure.

4. The method of claim 1,

wherein identifying the plurality of fiducial points further comprises initiating, by the medical device, a time window from the identified point within the derivative signal that satisfies the threshold, the time window extending forward in time, and

wherein identifying the fiducial point within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold comprises identifying a point of maximum slope within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold.

5. The method of claim 4, wherein the time window has a length that is fixed.

6. The method of claim 4, wherein the threshold is a fixed value.

7. The method of claim 4, wherein the threshold is adaptive.

8. The method of claim 4, further comprising:

controlling delivery of at least one of electrical stimulation and a therapeutic agent based on the identified cardiac cycle length.

9. The method of claim 4, wherein the blanking period is terminated based on a time of a peak-systolic pressure.

10. A medical device system for monitoring a cardiovascular pressure signal, comprising:

at least one pressure sensor to generate a cardiovascular pressure signal; and

at least one pressure analysis module configured to;

identify a plurality of fiducial points within a derivative signal of a cardiovascular pressure signal without reference to electrical activity; and

identify a length of time between consecutive ones of the fiducial points as a cardiac cycle length,

wherein the at least one pressure analysis module configured to identify the plurality of fiducial points is further configured to;

compare the derivative signal to a threshold;

identify a point within the derivative signal that satisfies the threshold;

identify the fiducial point within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold; and

initiate a blanking period that begins at the identified point that satisfies the threshold, and wherein at least one pressure analysis module configured to compare the derivative signal to the threshold is configured to not compare the derivative signal to the threshold for identification of a subsequent one of the fiducial points during the blanking period.

11. The system of claim 10, wherein the at least one pressure analysis module configured to identify the plurality of fiducial points is further configured to verify at least one of the following:

that a value of a second derivative signal of the cardiovascular pressure signal is greater than zero when the point within the derivative signal satisfies the threshold; and

that at least one value of the derivative signal of the cardiovascular pressure signal is below the threshold prior to the point within the derivative signal satisfying the threshold.

12. The system of claim 10, wherein the consecutive ones of the fiducial points comprise:

a first sense and a second sense;

a first end-diastolic pressure and a second end-diastolic pressure;

a first peak-systolic pressure and a second peak-systolic pressure;

or

a first maximum value of the first derivative signal of the cardiovascular pressure signal and a second maximum value of the first derivative signal of the cardiovascular pressure.

13. The system of claim 10,

wherein the at least one pressure analysis module configured to identify the plurality of fiducial points further is further configured to initiate a time window from the identified point within the derivative signal that satisfies the threshold, the time window extending forward in time, and

wherein the at least one pressure analysis module configured to identify the fiducial point within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold is configured to identify a point of maximum slope within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold.

14. The system of claim 13, wherein the time window has a length that is fixed.

15. The system of claim 13, wherein the threshold is a fixed value.

16. The system of claim 13, wherein the threshold is adaptive.

17. The system of claim 13, further comprising:

at least one medical device configured to deliver at least one of electrical stimulation and a therapeutic agent based on the identified cardiac cycle length.

18. The system of claim 10, wherein the blanking period is terminated based on a time of a peak-systolic pressure.

19. A computer-readable storage medium comprising instructions that, when executed, cause a cardiovascular pressure analysis module to:

identify a plurality of fiducial points within a derivative signal of a cardiovascular pressure signal without reference to cardiovascular electrical activity; and

identify a length of time between consecutive ones of the fiducial points as a cardiac cycle length,

wherein the instructions that, when executed, cause a pressure analysis module to identify the plurality of fiducial points comprise instructions that, when executed, cause the pressure analysis module to;

compare the derivative signal to a threshold;

identify a point within the derivative signal that satisfies the threshold;

identify the fiducial point within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold; and

initiate a blanking period that begins at the identified point that satisfies the threshold, and wherein the instructions that, when executed, cause a pressure analysis module to compare the derivative signal to the threshold comprise instructions that, when executed, cause the pressure analysis module to not compare the derivative signal to the threshold for identification of a subsequent one of the fiducial points during the blanking period.

20. The computer-readable storage medium of claim 19, wherein the instructions that, when executed, cause a pressure analysis module to identify the plurality of fiducial points comprise instructions that, when executed, cause the pressure analysis module, further comprises instructions to verify at least one of the following:

that a value of a second derivative signal of the cardiovascular pressure signal is greater than zero when the point within the derivative signal satisfies the threshold; and

that at least one value of the derivative signal of the cardiovascular pressure signal is below the threshold prior to the point within the derivative signal satisfying the threshold.

21. The computer-readable storage medium of claim 19, wherein the consecutive ones of the fiducial points comprise:

a first sense and a second sense;

a first end-diastolic pressure and a second end-diastolic pressure;

a first peak-systolic pressure and a second peak-systolic pressure;

or

a first maximum value of the first derivative signal of the cardiovascular pressure signal and a second maximum value of the first derivative signal of the cardiovascular pressure.

22. The computer-readable storage medium of claim 19,

wherein the instructions that, when executed, cause a pressure analysis module to identify the plurality of fiducial points further comprise instructions that, when executed, cause the pressure analysis module to initiate a time window from the identified point within the derivative signal that satisfies the threshold, the time window extending forward in time, and

wherein the instructions that, when executed, cause a pressure analysis module to identify the fiducial point within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold comprise instructions that, when executed, cause the pressure analysis module to identify a point of maximum slope within the derivative signal subsequent to the point within the derivative signal that satisfies the threshold.

23. The computer-readable storage medium of claim 22, further comprising instructions that, when executed, cause a processor to:

deliver at least one of electrical stimulation and a therapeutic agent based on the identified cardiac cycle length.