Implantable Systemic Blood Pressure Measurement Systems and Methods

• US 20090062667A1
• Filed: 08/31/2007
• Published: 03/05/2009
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Fayram, Timothy A., Fain, Eric S., Levine, Paul A.
• Granted Patent: US 8,147,416 B2
• Time in Patent Office: Days
• US Class Current: 600/486
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/355 Detecting T-waves
• CPC Class Codes: A61B 5/358 Detecting ST segments
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

Implantable systems, and methods for use therewith, for monitoring arterial blood pressure on a chronic basis are provided herein. A first signal indicative of electrical activity of a patient'"'"'s heart, and a second signal indicative of mechanical activity of the patient'"'"'s heart, are obtained using implanted electrodes and an implanted sensor. By measuring the times between various features of the first signal relative to features of the second signal, values indicative of systolic pressure and diastolic pressure can be determined. In specific embodiments, such features are used to determine a peak pulse arrival time (PPAT), which is used to determine the value indicative of systolic pressure. Additionally, a peak-to-peak amplitude at the maximum peak of the second signal, and the value indicative of systolic pressure, can be used to determine the value indicative of diastolic pressure.

Claims

1. For use with an implantable system, a method for monitoring a patient'"'"'s arterial blood pressure, the method comprising:

(a) using implanted electrodes to obtain a first signal indicative of electrical activity of the patient'"'"'s heart;

(b) using an implanted sensor to obtain a second signal indicative of mechanical activity of the patient'"'"'s heart;

(c) detecting a ventricular depolarization and a ventricular repolarization in a portion of the first signal corresponding to a cardiac cycle;

(d) detecting a maximum peak amplitude in a portion of the second signal corresponding to the same cardiac cycle;

(e) determining a time t₁ from the detected ventricular depolarization to the detected maximum peak amplitude in the second signal;

(f) determining a time t₂ from the detected ventricular repolarization to the detected maximum peak amplitude in the second signal;

(g) determining a peak pulse arrival time (PPAT) based on times t₁ and t₂; and

(h) determining a value indicative of systolic pressure (SP) based on the PPAT.

2. The method of claim 1, wherein:

step (g) comprises determining PPAT by determining a mean of times t₁ and t₂.

3. The method of claim 1, further comprising calibrating the implantable system by:

(i) obtaining accurate measures of the patient'"'"'s systolic (SP) pressure using a non-implanted device and/or an acutely implanted device;

(ii) using the implanted electrodes and the implanted sensor to determine a peak pulse arrival time (PPAT) corresponding each of a plurality of accurate measures of the patient'"'"'s SP; and

(iii) using the accurate measures of SP and the corresponding PPATs to determine one or more patient specific correlation factor that enables values indicative of the patient'"'"'s SP to be calculated based on PPAT; and

wherein step (h) includes using the one or more patient specific correlation factor when determining the value indicative of SP.

4. The method of claim 1, further comprising:

(i) determining a peak-to-peak amplitude a₁ in the second signal; and

(j) determining a value indicative of diastolic pressure (DP) based on the amplitude a1 and the value indicative of SP.

5. The method of claim 4, wherein step (j) includes:

(j.1) determining a value indicative of pulse pressure (PP) based on the amplitude a₁;

(j.2) determining the value indicative of DP by subtracting the value indicative of PP from the value indicative of SP.

6. The method of claim 4, further comprising calibrating the implantable system by:

(i) obtaining accurate measures of the patient'"'"'s systolic pressure (SP) and diastolic pressure (DP) using a non-implanted device and/or an acutely implanted device;

(ii) using the implanted electrodes and the implanted sensor to determine a peak pulse arrival time (PPAT) and a peak-to-peak amplitude a₁ corresponding each of a plurality of accurate measures of the patient'"'"'s SP and DP; and

(iii) using the accurate measures of SP and DP and the corresponding PPATs and peak-to-peak amplitudes a₁ to determine patient specific correlation factors that enable values indicative of the patient'"'"'s SP and values indicative of the patient'"'"'s DP to be to be calculated based on PPAT and a₁, and

wherein step (h) includes using at least one of the patient specific correlation factors when determining the value indicative of SP; and

wherein step (j) includes using at least one of the patient specific correlation factors when determining the value indicative of DP.

7. The method of claim 4, further comprising:

repeating steps (a) through (j) over time to thereby track changes in SP and DP.

8. The method of claim 7, further comprising using an activity sensor and/or posture sensor to trigger the performance of at least some of steps (a) through (j).

9. The method of claim 7, further comprising:

triggering an alarm based on comparisons of the values indicative of SP, the values indicative of DP, the changes in SP and/or the changes in DP to corresponding thresholds.

10. The method of claim 7, wherein:

step (h) includes storing the value indicative of SP;

step (j) includes storing the value indicative of DP;

and further comprising wirelessly transmitting data indicative of the stored values indicative of SP and DP to a non-implanted device.

11. The method of claim 10, further comprising:

triggering a non-implanted alarm based on comparisons of the values indicative of SP, the values indicative of DP, the changes in SP and/or the changes in DP, received by the non-implanted device, to corresponding thresholds.

12. The method of claim 7, further comprising:

using the values indicative of SP and/or DP for pacing parameter adjustment.

13. The method of claim 7, further comprising:

monitoring for episodes of myocardial ischemia; and

correlating detected episodes of myocardial ischemia with values indicative of SP and/or DP.

14. The method of claim 1, wherein the first signal comprises:

an intracardiac electrogram (IEGM) obtained using one or more electrode of an endocardial lead;

or

an electrocardiogram (ECG) obtained using one or more subcutaneous or other ECG electrode.

15. The method of claim 1, wherein the second signal comprises a plethysmography signal.

16. The method of claim 15, wherein the plethysmography signal comprises a photoplethysmography signal obtained using an implanted extravascular photoplethysmography sensor.

17. The method of claim 15, wherein the plethysmography signal comprises an impedance plethysmography signal obtained using an implanted impedance sensor.

18. The method of claim 1, wherein the second signal comprises a signal obtained using an implanted sensor including a piezo-electric diaphragm.

19. The method of claim 1, wherein step (c) includes:

detecting the ventricular depolarization by detecting an R-wave in the portion of the first signal corresponding to the cardiac cycle; and

detecting the ventricular repolarization by detecting a T-wave in the portion of the first signal corresponding to the cardiac cycle.

20. The method of claim 1, wherein at least some of the steps are performed in response to a triggering event detected using an implanted sensor that detects posture and/or activity.

21. An implantable system configured to monitor a patient'"'"'s arterial blood pressure, comprising:

a first detector configured to detect ventricular depolarizations and ventricular repolarizations in cardiac cycles represented in a first signal that is indicative of electrical activity of a patient'"'"'s heart;

a second detector configured to detect maximum peak amplitudes in cardiac cycles represented in a second signal indicative of mechanical activity of the patient'"'"' heart;

an arterial blood pressure monitor configured to

determine a time t₁ from a detected ventricular depolarization to a detected maximum peak amplitude in the second signal;

determine a time t₂ from the detected ventricular repolarization to the detected maximum peak amplitude in the second signal;

determine a peak pulse arrival time (PPAT) based on times t₁ and t₂; and

determine a value indicative of systolic pressure (SP) based on the PPAT.

22. The implantable system of claim 21, wherein:

the first signal comprises an intracardiac electrogram (IEGM) or an electrocardiogram (ECG); and

the second signal comprises a plethysmography signal.

23. The implantable system of claim 22, further comprising:

a sensing circuit to obtain the first signal using implantable electrodes; and

an implantable plethysmography sensor to obtain the second signal.

24. The implantable system of claim 23, wherein the implantable plethysmography sensor comprises a photoplethymography sensor.

25. The implantable system of claim 21, wherein the arterial blood pressure monitor is also configured to:

determine a value indicative of pulse pressure (PP) based on the amplitude a₁; and

determine a value indicative of diastolic pressure (DP) by subtracting the value indicative of PP from the value indicative of SP.

26. The implantable system of claim 25, wherein the arterial blood pressure monitor can track changes in SP and DP over time.

27. For use with an implantable system, a method for monitoring a patient'"'"'s arterial blood pressure, the method comprising:

(a) using implanted electrodes to obtain a first signal indicative of electrical activity of the patient'"'"'s heart;

(b) using an implanted sensor to obtain a second signal indicative of mechanical activity of the patient'"'"'s heart;

(c) detecting a ventricular depolarization in a portion of the first signal corresponding to a cardiac cycle;

(d) detecting a maximum peak amplitude in a portion of the second signal corresponding to the same cardiac cycle;

(e) determining a pulse arrival time (PAT) by determining a time t₁ from detection of the ventricular depolarization to the detection of the maximum peak amplitude in the second signal; and

(f) determining a value indicative of systolic pressure (SP) based on the PAT.

28. The method of claim 27, further comprising calibrating the implantable system by:

(i) obtaining accurate measures of the patient'"'"'s systolic (SP) pressure using a non-implanted device and/or an acutely implanted device;

(ii) using the implanted electrodes and the implanted sensor to determine a pulse arrival time (PAT) corresponding each of a plurality of accurate measures of the patient'"'"'s SP; and

(iii) using the accurate measures of SP and the corresponding PATs to determine one or more patient specific correlation factor that enables values indicative of the patient'"'"'s SP to be calculated based on PAT; and

wherein step (h) includes using the one or more patient specific correlation factor when determining the value indicative of SP.

29. The method of claim 27, further comprising:

(g) determining a peak-to-peak amplitude a₁ in the second signal; and

(h) determining a value indicative of diastolic pressure (DP) based on the amplitude a1 and the value indicative of SP.

30. The method of claim 29, wherein step (h) includes:

(h.1) determining a value indicative of pulse pressure (PP) based on the amplitude a₁; and

(h.2) determining the value indicative of DP by subtracting the value indicative of PP from the value indicative of SP.

31. The method of claim 29, further comprising calibrating the implantable system by:

(i) obtaining accurate measures of the patient'"'"'s systolic pressure (SP) and diastolic pressure (DP) using a non-implanted device and/or an acutely implanted device;

(ii) using the implanted electrodes and the implanted sensor to determine a pulse arrival time (PAT) and a peak-to-peak amplitude a₁ corresponding each of a plurality of accurate measures of the patient'"'"'s SP and DP; and

(iii) using the accurate measures of SP and DP and the corresponding PATs and peak-to-peak amplitudes a₁ to determine patient specific correlation factors that enable values indicative of the patient'"'"'s SP and values indicative of the patient'"'"'s DP to be to be calculated based on PAT and a₁, and

wherein step (f) includes using at least one of the patient specific correlation factors when determining the value indicative of SP; and

wherein step (h) includes using at least one of the patient specific correlation factors when determining the value indicative of DP.

32. An implantable system configured to monitor a patient'"'"'s arterial blood pressure, comprising:

a first detector configured to detect ventricular depolarizations in cardiac cycles represented in a first signal that is indicative of electrical activity of a patient'"'"'s heart;

a second detector configured to detect maximum peak amplitudes in cardiac cycles represented in a second signal indicative of mechanical activity of the patient'"'"' heart;

an arterial blood pressure monitor configured to

determine a time t₁ from a detected ventricular depolarization to a detected maximum peak amplitude in the second signal;

determine a pulse arrival time (PAT) based on the time t₁; and

determine a value indicative of systolic pressure (SP) based on the PAT.

33. The implantable system of claim 32, wherein:

the first signal comprises an intracardiac electrogram (IEGM) or an electrocardiogram (ECG); and

the second signal comprises a plethysmography signal.

34. The implantable system of claim 33, further comprising:

a sensing circuit to obtain the first signal using implantable electrodes; and

an implantable plethysmography sensor to obtain the second signal.

35. The implantable system of claim 34, wherein the implantable plethysmography sensor comprises a photoplethymography sensor.

36. The implantable system of claim 32, wherein the arterial blood pressure monitor is also configured to:

determine a value indicative of pulse pressure (PP) based on the amplitude a₁; and

determine a value indicative of diastolic pressure (DP) by subtracting the value indicative of PP from the value indicative of SP.

37. The implantable system of claim 36, wherein the arterial blood pressure monitor can track changes in SP and DP over time.