Tracking progression of congestive heart failure via a force-frequency relationship

• US 20070043299A1
• Filed: 08/19/2005
• Published: 02/22/2007
• Est. Priority Date: 08/19/2005
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Wariar, Ramesh, Carlson, Gerrard
• Granted Patent: US 7,634,309 B2
• Time in Patent Office: Days
• US Class Current: 600/514
• 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 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/023 for introduction into the body, e.g. into the oesophagus oesophageal ECG probes A61B5/285
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy

Abstract

A system, method, or device monitor a force-frequency relationship exhibited by a patient'"'"'s heart. A contractility characteristic, such as a heart sound characteristic of an S1 heart sound, is measured. The contractility characteristic indicates the forcefulness of a contraction of the heart. The frequency at which the heart is contracting is determined. A group of (contractility characteristic, heart rate) pairs is stored in a memory device. The group of pairs defines a force-frequency relationship for the heart. The method may be implemented by an implantable device, or by a system including a implantable device.

Claims

1. A machine-assisted method comprising:

chronically measuring a contractility characteristic of a heart using an implanted medical device, the contractility characteristic indicating forcefulness of a contraction of a heart;

determining a corresponding heart rate indicating how frequently the heart is contracting; and

recording a group of (contractility characteristic, heart rate) pairs, the group of pairs defining a force-frequency relationship for the heart.

2. The method of claim 1, wherein the contractility characteristic of the heart is a heart sound characteristic of an S1 heart sound.

3. The method of claim 2, wherein the heart sound characteristic of the S1 heart sound comprises at least one of:

a peak-to-peak amplitude of the S1 heart sound; and

a quotient of energy contained in the S1 heart sound and energy contained in all heart sounds in a cardiac cycle in which the S1 heart sound is situated.

4. The method of claim 2, wherein the heart sound characteristic of the S1 heart sound is the quotient of energy contained in the S1 heart sound and a pulmonary artery pressure.

5. The method of claim 1, comprising:

measuring a left ventricular diastolic volume characteristic; and

adjusting the contractility characteristic using the left ventricle diastolic volume characteristic.

6. The method of claim 1, comprising:

measuring a left ventricular diastolic pressure characteristic;

adjusting the contractility characteristic using a left ventricle diastolic pressure characteristic.

7. The method of claim 1, comprising:

measuring a pulmonary capillary wedge pressure characteristic; and

adjusting the contractility characteristic using the pulmonary capillary wedge pressure characteristic.

8. The method of claim 1, comprising:

measuring a pulmonary artery pressure characteristic; and

adjusting the contractility characteristic using the pulmonary artery pressure characteristic.

9. The method of claim 1, comprising:

measuring an S3 amplitude characteristic; and

adjusting the contractility characteristic using the S3 amplitude characteristic.

10. The method of claim 1, comprising:

altering the heart rate, over a period during which the measuring, determining, and recording acts take place, by pacing the heart at different rates during the period.

11. The method of claim 10, comprising:

executing the measuring, determining, and recording in response to receiving a command at an implantable medical device from a remote external system.

12. The method of claim 11, wherein the measuring, determining, recording, and altering acts are inhibited unless the command from the remote external system is received.

13. The method of claim 1, comprising:

transmitting the group from an implantable medical device to an external computing system or to an external access point to a network.

14. A machine-assisted method comprising:

receiving, at a first point in time, a first set of (contractility characteristic, heart rate) pairs defining a first force-frequency relationship for a patient'"'"'s heart;

receiving, at a second point in time, a second set of (contractility characteristic, heart rate) pairs defining a second force-frequency relationship for the patient'"'"'s heart; and

presenting a trend using the first and second force-frequency relationships for the patient'"'"'s heart.

15. The method of claim 14, wherein the act of presenting a trend comprises:

displaying the first and second force-frequency relationships on an output device.

16. The method of claim 14, wherein the act of presenting a trend comprises:

calculating a first approximate slope exhibited by the first force-frequency relationship over a given frequency range;

calculating a second approximate slope exhibited by the second force-frequency relationship over the given frequency range; and

presenting information about the first and second approximate slopes on an output device.

17. The method of claim 14, wherein the act of presenting a trend comprises:

determining a first frequency at which the first force-frequency relationship departs from substantial linearity;

determining a second frequency at which the second force-frequency relationship departs from substantial linearity; and

presenting information about the first and second frequencies on an output device.

18. An implantable device comprising:

a transducer to convert a heart contraction into an electrical signal that includes contractility information;

a memory device; and

a control circuit coupled to the transducer, and memory device, the control circuit configured to receive the electrical signal and extract a contractility characteristic that relates to forcefulness of a contraction of a heart, the control circuit also configured to determine a heart rate, and the control circuit also configured to store in the memory device a force-frequency relationship for the heart, using the heart rate and the contractility characteristic.

19. The device of claim 18, further including a sense amplifier to detect heart depolarizations and, wherein the control circuit is further configured to determine the heart rate using a signal received from the sense amplifier.

20. The device of claim 18, wherein the control circuit is configured to determine the contractility characteristic using a heart sound characteristic.

21. The device of claim 20, in which the control circuit is configured to determine the contractility characteristic using at least one of:

an S1 heart sound amplitude; and

a quotient of energy contained in the S1 heart sound and energy contained in all heart sounds in a cardiac cycle in which the S1 heart sound is situated.

22. The device of claim 18, further comprising a pressure sensor in data communication with the control circuit, and wherein the control circuit is configured to determine the contractility characteristic using a quotient of energy contained in an S1 heart sound and pulmonary artery pressure measured by the pressure sensor.

23. The device of claim 18, further comprising a stimulating circuit coupled to the control circuit, and wherein the control circuit is further configured to alter the heart rate over a period during which the S1 heart sounds are obtained by pacing the heart with the stimulating circuit at varying rates throughout the period.

24. The device of claim 18, further comprising an I/O interface, and wherein the control circuit is further configured to communicate the force-frequency relationship to an external device via the I/O interface.

25. A system comprising:

an I/O interface;

a memory device; and

a control circuit coupled to the I/O interface and the memory device, the control circuit configured to receive via the I/O interface first and second force-frequency relationships for a patient'"'"'s heart, and to present via an output device a trend between the first and second force-frequency relationships for the patient'"'"'s heart.

26. The computing system of claim 25, wherein the control circuit is configured to present a trend by displaying the first and second force-frequency relationships on the output device.

27. The computing system of claim 25, wherein the control circuit is configured to present a trend by using a first approximate slope exhibited by the first force-frequency relationship over a given frequency range, and using a second approximate slope exhibited by the second force-frequency relationship over the given frequency range, and presenting an indication of the first and second approximate slopes on the output device.

28. The computing system of claim 25, wherein the control circuit is configured to present a trend by using a first frequency at which the first force-frequency relationship substantially departs from linearity, and using a second frequency at which the second force-frequency relationship substantially departs from linearity, and presenting an indication of first and second frequencies on the output device.