METHODS AND SYSTEMS TO MONITOR CARDIAC CONTRACTILITY

• US 20110125208A1
• Filed: 12/30/2009
• Published: 05/26/2011
• Est. Priority Date: 11/20/2009
• Status: Abandoned Application

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Keel, Allen J., Karst, Edward, Wenzel, Brian Jeffrey, Hou, Wenbo, Farazi, Taraneh Ghaffari
• Application Number:
  US12/649,632
• Publication Number:
  US 20110125208A1
• Time in Patent Office: Days
• US Class Current: 607/17
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• 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 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: A61N 1/3686 configured for selecting the electrode configuration on a lead A61N1/3688 takes precedence
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/371 Capture, i.e. successful stimulation

Abstract

An implanted sensor produces a signal that is indicative of changes in arterial blood volume, such as a photoplethysmography signal or an impedance plethysmography signal. A metric is determined from the signal for each of the plurality of periods. Changes in cardiac contractility are monitored based on changes in the determined metric.

Claims

1. For use with an implanted system, a method for monitoring cardiac contractility, comprising:

(a) for each of a plurality of periods, using an implanted sensor to produce a signal that is indicative of changes in arterial blood volume;

(b) determining a metric from the signal for each of the plurality of periods; and

(c) monitoring changes in cardiac contractility based on changes in the determined metric.

2. The method of claim 1, wherein:

step (a) comprises using an implanted photoplethysmography (PPG) sensor to produce a photoplethysmography signal that is indicative of changes in arterial blood volume.

3. The method of claim 1, wherein:

step (a) comprises using an implanted impedance plethysmography sensor to produce an impedance plethysmography (IPG) signal that is indicative of changes in arterial blood volume.

4. The method of claim 1, wherein:

the metric determined at step (b) is indicative of an upward slope of the signal; and

detecting an increase in the metric at step (c) is indicative of an increase in the cardiac contractility; and

detecting a decrease in the metric of step (c) is indicative of a decrease of the cardiac contractility.

5. The method of claim 1, wherein:

the metric determined at step (b) is indicative of a time between two features of a cycle of the signal, the two features occurring between and inclusive of a foot indicative of beginning of systole and a dicrotic notch indicating closing of the aortic valve during the cycle of the signal;

detecting a decrease in the metric at step (c) is indicative of an increase in the cardiac contractility; and

detecting an increase in the metric at step (c) is indicative of a decrease in the cardiac contractility.

6. The method of claim 1, wherein:

the metric determined at step (b) is indicative of an amplitude of the signal where a dicrotic notch of the signal occurs;

detecting an increase in the metric at step (c) is indicative of an increase in the cardiac contractility; and

detecting a decrease in the metric at step (c) is indicative of a decrease of cardiac contractility.

7. The method of claim 1, wherein:

the metric determined at step (b) is determined from a derivative of the signal.

8. The method of claim 1, further comprising:

(d) adjusting at least one pacing parameter based on the monitored cardiac contractility.

9. The method of claim 8, wherein:

step (d) comprises adjusting the at least one pacing parameter to modify the monitored cardiac contractility be closer to a desired cardiac contractility.

10. The method of claim 1, further comprising:

(d) adjusting at least one pacing parameter and determining a change in the monitored cardiac contractility; and

(e) using the change in monitored cardiac contractility to determine a presence of dyssynchrony or a change in dyssynchrony.

11. The method of claim 1, further comprising:

(d) providing therapy based on the determined cardiac contractility.

12. An implantable system for monitoring cardiac contractility comprising:

an implantable sensor configured to produce a signal that is indicative of changes in arterial blood volume for each of a plurality of periods; and

a monitor configured to determine a metric from the signal for each of the plurality of periods; and

monitor changes in cardiac contractility based on changes in the metric.

13. The implantable system of claim 12, wherein:

the implantable sensor comprises an implantable photoplethysmography sensor configured to produce a photoplethysmography (PPG) signal that is indicative of changes in arterial blood volume.

14. The implantable system of claim 12, wherein:

the implantable sensor comprises an implantable impedance plethysmography sensor configured to produce an impedance plethysmography (IPG) signal that is indicative of changes in arterial blood volume.

15. The implantable system of claim 12, wherein:

the monitor is configured to determine the metric such that the metric is indicative of an upward slope of the signal;

detect an increase in the metric as indicative of an increase in the cardiac contractility; and

detect a decrease in the metric as indicative of a decrease in the cardiac contractility.

16. The implantable system of claim 12, wherein:

the monitor is configured to determine the metric such that the metric is indicative of a time between two features of a cycle of the signal, the two features occurring between and inclusive of a foot indicative of beginning of systole and a dicrotic notch indicative of the closing of the aortic valve during the cycle of the signal;

detect a decrease in the metric as indicative of an increase in the cardiac contractility; and

detect an increase in the metric as indicative of a decrease in cardiac contractility.

17. The implantable system of claim 12, wherein:

the monitor is configured to determine the metric such that the metric is indicative of a signal amplitude of where a dicrotic notch occurs expressed in terms of a fraction of a difference between a maximum and a minimum amplitude;

detect an increase in the metric as indicative of an increase in the cardiac contractility; and

detect a decrease in the metric as indicative of a decrease in the cardiac contractility.

18. The implantable system of claim 12, wherein:

the monitor is configured to determine the metric from a derivative of the signal.

19. The implantable system of claim 12, further comprising:

a pulse generator configured to produce cardiac pacing pulses; and

a pacing controller configured to control pacing parameters of the pacing pulses produced by the pulse generator;

wherein the pacing controller is configured to adjust at least one pacing parameter based on the monitored cardiac contractility.

20. The implantable system of claim 12, further comprising:

a component to provide therapy based on the determined cardiac contractility.

21. The implantable system of claim 12, further comprising:

a pulse generator configured to produce cardiac pacing pulses; and

wherein the monitor is configured to determine lack of capture by one or more of the pulses based on the monitored cardiac contractility.

22. For use with an implanted system, a method for monitoring cardiac contractility, comprising:

(a) using an implanted sensor to produce a plethysmography signal that is indicative of changes in arterial blood volume; and

(b) monitoring changes in cardiac contractility based on changes in the plethysmography signal.

23. The method of claim 22, further comprising determining a metric from the signal.

24. The method of claim 23, wherein step (b) includes monitoring changes in cardiac contractility based on changes in the determined metric.