System and Method for Estimating Cardiac Pressure Based on Cardiac Electrical Conduction Delays Using an Implantable Medical Device

• US 20090287267A1
• Filed: 07/18/2007
• Published: 11/19/2009
• Est. Priority Date: 04/04/2007
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Panescu, Dorin, Min, Xiaoyi, Wenzel, Brian Jeffrey, Bjorling, Anders, Naware, Mihir, Gutfinger, Dan E., Siou, Jeffery
• Granted Patent: US 8,504,153 B2
• Time in Patent Office: Days
• US Class Current: 607/9
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/02156 Calibration means
• CPC Class Codes: A61B 5/72 Signal processing specially adapted for physiological signals or for diagnostic purposes character recognition, recognising digital ink, document-oriented image-based pattern recognition G06V30/00; recognition or understanding of postal images G06V30/424
• 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 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone
• CPC Class Codes: A61N 1/3682 with a variable atrioventricular delay
• CPC Class Codes: A61N 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/36842 Multi-site stimulation in the same chamber
• CPC Class Codes: A61N 1/36843 Bi-ventricular stimulation
• CPC Class Codes: A61N 1/37258 Alerting the patient

Abstract

Techniques are provided for estimating left atrial pressure (LAP) or other cardiac performance parameters based on measured conduction delays. In particular, LAP is estimated based interventricular conduction delays. Predetermined conversion factors stored within the device are used to convert the various the conduction delays into LAP values or other appropriate cardiac performance parameters. The conversion factors may be, for example, slope and baseline values derived during an initial calibration procedure performed by an external system, such as an external programmer. In some examples, the slope and baseline values may be periodically re-calibrated by the implantable device itself. Techniques are also described for adaptively adjusting pacing parameters based on estimated LAP or other cardiac performance parameters. Still further, techniques are described for estimating conduction delays based on impedance or admittance values and for tracking heart failure therefrom.

Claims

1. A method for estimating cardiac pressure within a patient using an implantable medical device, the method comprising:

measuring an electrical conduction delay in the heart of the patient; and

estimating cardiac pressure within the patient from the electrical conduction delay.

2. The method of claim 1 wherein measuring the electrical conduction delay includes:

sensing an intrinsic electrical depolarization event at a first location within the heart;

sensing a responsive electrical depolarization event at a second location within the heart; and

measuring the time delay therebetween.

3. The method of claim 1 wherein estimating cardiac pressure within the patient includes measuring multiple conduction delay values and applying a regression model to conduction delay values obtained within the patient.

4. The method of claim 1 wherein estimating cardiac pressure within the patient includes measuring multiple conduction delay values and applying a neural network to conduction delay values obtained within the patient.

5. The method of claim 1 wherein estimating cardiac pressure within the patient includes estimating discrete intervals of cardiac pressure.

6. The method of claim 1 further including estimating end diastolic volume (EDV) within the patient based on the conduction delay.

7. The method of claim 6 wherein left ventricular (LV) end diastolic volume (EDV) is estimated within the patient based on an LV conduction delay.

8. The method of claim 1 further including estimating end diastolic pressure (EDP) within the patient based on the conduction delay.

9. The method of claim 8 wherein left ventricular (LV) end diastolic pressure (EDP) is estimated within the patient based on an LV conduction delay.

10. The method of claim 1 wherein measuring conduction delays includes measuring one or more of:

atrial sense and atrial pace wave duration;

ventricular sense based right ventricular (RV) to left ventricular (LV) conduction delays;

RV pace to LV pace delays;

LV to RV pace delay or differences therebetween;

P-wave to R-wave (PR) and atrial pace to R-wave (AR) atrio-ventricular delays; and

RV to LV pace delay minus pacing latency values.

11. A method for estimating cardiac pressure within a patient using an implantable medical device, the method comprising:

measuring an electrical conduction delay in the heart of the patient by delivering a pacing pulse to a first location within the heart and sensing a responsive electrical depolarization event at a second location within the heart and measuring the time delay therebetween; and

estimating cardiac pressure within the patient from the electrical conduction delay.

12. The method of claim 11 wherein the first and second locations are in different chambers of the heart such that the conduction delay is an inter-chamber delay.

13. The method of claim 12 wherein the first and second locations are in different ventricular chambers of the heart such that the conduction delay is an interventricular delay.

14. The method of claim 11 wherein the first and second locations are in the same chamber of the heart such that the conduction delay is an intra-chamber delay.

15. The method of claim 14 wherein the first and second locations are in the same ventricular chamber of the heart such that the conduction delay is an intraventricular delay.

16. The method of claim 11 wherein the first location is in the atria and the second location is in the ventricles such that the conduction delay is an atrioventricular (AV) delay.

17. A method for estimating cardiac pressure within a patient using an implantable medical device, the method comprising:

measuring an electrical conduction delay in the heart of the patient;

inputting predetermined conversion factors for converting the conduction delay to cardiac pressure; and

estimating cardiac pressure within the patient from the electrical conduction delay by applying the conversion factors to the conduction delay.

18. The method of claim 17 wherein inputting predetermined conversion factors includes inputting slope and baseline values representative of a linear relationship between cardiac pressure and the conduction delays.

19. The method of claim 18 wherein estimating cardiac pressure includes calculating:

Cardiac Pressure=Delay*Slope+Baseline.

20. The method of claim 19 wherein the delay is measured between the left ventricle (LV) and the right ventricle (RV) and wherein the resulting cardiac pressure value is an estimated left atrial pressure (LAP_LV-RV) value obtained by calculating:

LAP_LV-RV=Delay_LV-RV*Slope_LAP/LV-RV+Baseline_LAP/LV-RV;

wherein Slope_LAP/LV-RV and Baseline_LAP/LV-RV are slope and baseline values specifically calibrated for use in estimating LAP from LV-RV delays.

21. The method of claim 19 further including an initial calibration step for determining the slope and baseline values that are representative of the linear relationship between the conduction delay and cardiac pressure for the particular patient.

22. The method of claim 21 wherein determining the slope and baseline values includes:

inputting a first conduction delay calibration value (D₁) and a corresponding first cardiac pressure calibration value (Pressure₁) measured at a first time within the patient; and

inputting a second conduction delay calibration value (D₂) and a corresponding second cardiac pressure calibration value (Pressure₂) measured at a second time within the patient, wherein the first and second cardiac pressure values (Pressure₁, Pressure₂) differ substantially.

23. The method of claim 22 wherein determining the slope is performed by calculating:

Slope=(Pressure₂−

Pressure₁)/(D₂−

D₁).

24. The method of claim 23 wherein determining the baseline is performed by calculating:

Baseline=Pressure₂−

Slope*D₁.

25. The method of claim 22 further including the calibration steps of:

detecting the first cardiac pressure value (Pressure₁) and the first conduction delay calibration value (D₁) while the patient is at rest; and

detecting the second cardiac pressure value (Pressure₂) and the second conduction delay calibration value (D₂) while the patient is subject to a condition significantly affecting cardiac pressure within the patient.

26. The method of claim 25 wherein the first and second cardiac pressure values (Pressure₁, Pressure₂) are measured within the patient using a Swan-Ganz catheter equipped to measure pulmonary capillary wedge pressure (PCWP).

27. The method of claim 25 wherein the condition significantly affecting cardiac pressure within the patient includes one or more of:

isometric muscle contraction, vasodilatation, vasoconstriction, rapid pacing, performance of the Valsalva maneuver and performance of the handgrip maneuver.

28. The method of claim 22 wherein the cardiac pressure value to be estimated is an effective pressure value and wherein the method further includes the calibration steps of:

detecting the first cardiac pressure value (Pressure₁) and the first conduction delay calibration value (D₁) within the patient at device implant; and

detecting an additional conduction delay calibration value (D_N) during performance of a Valsalva maneuver by the patient at a time subsequent to implant.

29. The method of claim 28 wherein the slope is assumed not to change significantly following device implant and wherein the baseline value is re-calibrated based on an additional conduction delay value (D_N):

Baseline=−

Slope*D_N.

30. The method of claim 28 wherein the slope might change significantly following device implant and wherein the slope and baseline values are re-calibrated based on an additional conduction delay value (D_N) and on a first effective cardiac pressure value (Pressure₁)

Slope=−

Pressure₁/(D_N−

D₁) and

Baseline=−

Slope*D_N.

31. The method of claim 28 wherein the effective cardiac pressure value might not drop to zero within the patient during Valsalva and wherein an additional correction factor is calculated at device implant.

32. The method of claim 19 further including an initial calibration step of determining the slope and baseline values that are representative of the linear relationship between conduction delay and cardiac pressure for any of a plurality of patients.

33. The method of claim 32 wherein determining the slope and baseline values includes:

inputting a plurality of conduction delay values (D) and corresponding cardiac pressure values (Pressure) measured within a plurality of test subjects; and

determining slope and baseline values by applying linear regression to the plurality of conduction delay values (D) and cardiac pressure values (Pressure) obtained from the test subjects.

34. The method of claim 33 wherein the conduction delay values (D) are measured between the LV and the RV of the test subjects and wherein the cardiac pressure values are obtained by temporary pressure sensors inserted within the test subjects.

35. A system for estimating cardiac pressure within a patient using an implantable medical device, the system comprising:

an electrical conduction delay measurement unit operative to measure conduction delays within the heart of the patient; and

a cardiac pressure estimation unit operative to estimate cardiac pressure within the patient based on the electrical conduction delay.

36. The system of claim 35 wherein the cardiac pressure estimation unit is operative to estimate left atrial pressure (LAP) from interventricular conduction delays.

37. The system of claim 35 further including a left ventricular (LV) end diastolic pressure (LV EDP) estimation system operative to estimate LV EDP from conduction delays.

38. The system of claim 35 further including an LV end diastolic volume (LV EDV) estimation system operative to estimate LV EDV from conduction delays.

39. The system of claim 35 further including a re-calibration system operative to re-calibrate the cardiac pressure estimation unit for use within the particular patient in which the device is implanted.

40. The system of claim 35 further including a heart failure detection system operative to detect heart failure based on estimated cardiac pressure.

41. The system of claim 40 further including an implantable warning device operative to generate a warning upon detection of heart failure.

42. The system of claim 40 further including an implantable warning device operative to generate a warning upon detection of heart failure.

43. A system for estimating cardiac pressure within a patient using an implantable medical device, the system comprising:

means for measuring an electrical conduction delay operative to measure conduction delays within the heart of the patient affected by cardiac pressure; and

means for estimating a cardiac pressure operative to estimate cardiac pressure within the patient based on the electrical conduction delay.

44. A method for calibrating a cardiac pressure estimation system of an implantable medical device for implant within a patient, the method comprising:

detecting a first cardiac pressure value (Pressure₁) and a first calibration value (D₁) while the patient is at rest, the first calibration value being a detected conduction delay within the heart of the patient;

detecting a second cardiac pressure value (Pressure₂) and a second calibration value (D₂) while the patient is subject to a condition significantly affecting cardiac pressure within the patient, the second calibration value also being a detected conduction delay within the heart of the patient;

determining conversion factors for converting additional detected conduction delays into cardiac pressure estimates based on the first and second cardiac pressure values (Pressure₁, Pressure₂) and the first and second calibration values (D₁, D₂); and

transmitting the conversion factors to the implantable medical device for use therein.

45. The method of claim 44 wherein a slope conversion factor is calculated by:

Slope=(Pressure₂−

Pressure₁)/(D₂−

D₁).

46. The method of claim 45 wherein determining a baseline conversion factor is calculated by:

Baseline=Pressure₂−

Slope*D₁.