System and method for evaluating diastolic function based on cardiogenic impedance using an implantable medical device

Patent metadata

Field	Value
Publication number	US-9433792-B2
Application number	US-201313898931-A
Country	US
Kind code	B2
Filing date	May 21, 2013
Priority date	May 21, 2013
Publication date	Sep 6, 2016
Grant date	Sep 6, 2016

Abstract

Diastolic function is monitored within a patient based on dynamic cardiogenic impedance as measured by a pacemaker or other implantable medical device. In one example, the device uses ventricular cardiogenic impedance values to detect E-wave parameters representative of passive filling of the ventricles. Atrial cardiogenic impedance values are used to detect A-wave parameters representative of active filling of the ventricles. Diastolic function is then assessed or evaluated based on the E-wave and A-wave parameters. Various functions of the implantable device are then controlled based on the assessment of diastolic function, such as by adjusting atrioventricular delay parameters to improve diastolic function. In some examples, the detection of E- and A-wave parameters is achieved by aligning impedance signals to atrial activation, and separately to ventricular activation, during asynchronous VOO pacing or while artificially inducing a 2:1 block.

First claim

What is claimed is:

1. A method for use with an implantable medical device for implant within a patient, the method comprising:
measuring values representative of ventricular cardiogenic impedance and deriving E-wave parameters representative of passive filling of the ventricles of the heart of the patient from the ventricular cardiogenic impedance values, wherein deriving E-wave parameters from the ventricular cardiogenic impedance values includes:
generating an E-wave impedance template representative of passive filling of the ventricles based on ventricular cardiogenic impedance values measured during an initial period of non-demand pacing, with the period of non-demand pacing including atrial pacing at a rate sufficient to trigger an artificial 2:1 block to emphasize active and passive filling contributions to diastolic function;
measuring additional values representative of ventricular impedance during a subsequent cardiac cycle to be examined; and
determining a convolution of the E-wave impedance template with the additional ventricular impedance values to derive E-wave parameters representative of passive filling contributions to diastolic function within the subsequent cardiac cycle;

measuring values representative of atrial cardiogenic impedance and deriving A-wave parameters representative of active filling of the ventricles from the atrial cardiogenic impedance values;
assessing diastolic function based on the E-wave parameters and the A-wave parameters; and
controlling at least one device function based on the assessment of diastolic function.

2. The method of claim 1 wherein measuring values representative of ventricular cardiogenic impedance includes measuring cardiogenic impedance along a vector between a right ventricular (RV) electrode and a housing of the device.

3. The method of claim 1 wherein measuring values representative of atrial cardiogenic impedance includes measuring cardiogenic impedance along a vector between a right atrial (RA) electrode and a housing of the device.

4. The method of claim 1 wherein the E-wave parameters representative of passive filling contributions to diastolic function include a parameter representative of the timing of the E-wave.

5. The method of claim 4 wherein the timing of the E-wave of the subsequent cardiac cycle is determined based on a time shift resulting in a greatest correlation coefficient between the E-wave impedance template and the ventricular impedance values of the subsequent cardiac cycle.

6. The method of claim 5 wherein the E-wave parameters include parameters representative of an amount of blood received by the ventricles during the particular cardiac cycle due to passive filling.

7. The method of claim 6 wherein the parameters representative of the amount of blood received by the ventricles during passive filling are determined based on a peak metric value of the greatest correlation coefficient between the E-wave impedance template and the additional ventricular impedance values of the subsequent cardiac cycle.

8. The method of claim 6 wherein the parameters representative of the amount of blood received by the ventricles during passive filling are determined based on a metric value obtained by calculating an integral of the ventricular impedance values of the subsequent cardiac cycle for samples where a correlation coefficient between the E-wave impedance template and the ventricular impedance values of the subsequent cardiac cycle exceeds a predetermined threshold.

9. The method of claim 1 wherein generating the E-wave impedance template includes:
measuring values representative of ventricular cardiogenic impedance during a period of non-demand pacing comprising a plurality of cardiac cycles;
detecting ventricular activation events within the cardiac cycles;
aligning the measured ventricular cardiogenic impedance values to the detected ventricular activation events of corresponding cardiac cycles such that any corresponding atrial activation events are approximately uniformly distributed so a contribution from active atrial filling sums to a substantially negligible level;
ensemble averaging the aligned ventricular cardiogenic impedance values;
detecting corresponding ventricular repolarization events within the cardiac cycles;
identifying a segment of decreasing impedance within the ensemble averaged ventricular cardiogenic impedance values following corresponding ventricular repolarization events within the cardiac cycles; and
storing the segment of decreasing impedance as the E-wave template.

10. The method of claim 1 wherein the period of non-demand pacing includes VOO pacing.

11. The method of claim 1 wherein the period of non-demand pacing includes DOO pacing with a selected atrioventricular (AV) pacing delay.

12. The method of claim 1 wherein the period of non-demand pacing includes ventricular pacing during one or more of atrial fibrillation and during automatic mode switch.

13. The method of claim 1 wherein deriving A-wave parameters from the atrial cardiogenic impedance values includes:
generating an A-wave impedance template representative of active filling of the ventricles based on atrial cardiogenic impedance values measured during an initial period of non-demand pacing;
measuring additional values representative of atrial impedance during a subsequent cardiac cycle; and
determining a convolution of the A-wave impedance template with the additional atrial impedance values to derive A-wave parameters representative of active filling contributions to diastolic function within the subsequent cardiac cycle.

14. The method of claim 13 wherein the A-wave parameters representative of active filling contributions to diastolic function include a parameter representative of the timing of the A-wave.

15. The method of claim 14 wherein the timing of the A-wave of the subsequent cardiac cycle is determined based on a time shift resulting in a greatest correlation coefficient between the A-wave impedance template and the atrial impedance values of the subsequent cardiac cycle.

16. The method of claim 13 wherein the A-wave parameters include parameters representative of an amount of blood received by the ventricles during the particular cardiac cycle due to active filling.

17. The method of claim 16 wherein the parameters representative of the amount of blood received by the ventricles during active filling are determined based on a peak metric value of the greatest correlation coefficient between the A-wave impedance template and the additional atrial impedance values of the subsequent cardiac cycle.

18. The method of claim 16 wherein the parameters representative of the amount of blood received by the ventricles during active filling are determined based on a metric value obtained by calculating an integral of the atrial impedance values of the subsequent cardiac cycle for samples where a correlation coefficient between the A-wave impedance template and the atrial impedance values of the subsequent cardiac cycle exceeds a predetermined threshold.

19. The method of claim 13 wherein generating the A-wave impedance template includes:
measuring values representative of atrial cardiogenic impedance during a period of non-demand pacing comprising a plurality of cardiac cycles;
detecting atrial activation events within the cardiac cycles;
aligning the measured atrial cardiogenic impedance values to the detected atrial activation events of corresponding cardiac cycles such that any corresponding ventricular activation events are approx

Assignees

• Pacesetter Inc

Inventors

• Rosenberg Stuart
• Gupta Kritika
• Shah Riddhi
• Bharmi Rupinder
• Karst Edward
• Bornzin Gene A

Classifications

• A61B5/0295

  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 title

• A61N1/3688

  configured for switching the pacing mode, e.g. from AAI to DDD · CPC title

• A61N1/3682

  with a variable atrioventricular delay · CPC title

• A61B5/7246

  using correlation, e.g. template matching or determination of similarity · CPC title

• A61B5/0538

  invasively, e.g. using a catheter · CPC title