Method for extracting timing parameters using a cardio-mechanical sensor

• US 7,569,020 B2
• Filed: 06/19/2006
• Issued: 08/04/2009
• Est. Priority Date: 06/19/2006
• Status: Active Grant

• Current Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Original Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Inventors: Noren, Kjell, Holmstrom, Nils
• Primary Examiner(s): Sykes; Angela D
• Assistant Examiner(s): PATTON, AMANDA K
• Application Number:
  US11/455,518
• Publication Number:
  US 20070293771A1
• Time in Patent Office: 1,142 Days
• Field of Search: 600/526
• US Class Current: 600/526
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone

Abstract

In a method and apparatus for measuring the ejection fraction in a mammalian heart, the opening and closing of a heart valve is sensed with an implanted sensor, and a pre-ejection period is measured as a function of the sensed opening and closing of the heart valve. The ventricular ejection time also is measured, and the ejection fraction is determined as a function of the measured pre-ejection period and the ejection time.

Claims

1. A method for measuring ejection fraction in a mammalian heart, comprising the steps of:

sensing opening and closing of a heart valve in the heart of a mammalian subject, and generating a sensor signal representing said opening and closing of said heart valve, said heart exhibiting a heartbeat rate;

filtering said sensor signal to extract a signal component therefrom, as a filtered signal, in a frequency range much higher than said heartbeat rate;

squaring said filtered signal to obtain a power signal representing power of said filtered signal;

providing said power signal to an electronic detection unit and, in said electronic detection unit, measuring, in said power signal, a pre-ejection period of said heart as a function of the sensed opening and closing of said heart valve;

additionally in said electronic detection unit, measuring, in said power signal, a ventricular ejection time of said heart;

in said electronic detection unit, automatically determining an ejection fraction of the heart as a function of the measured pre-ejection period and the measured ventricular ejection time; and

emitting an electronic output signal from said electronic detection unit representing said ejection function.

2. A method as claimed in claim 1 wherein the step of filtering said sensor signal comprises bandpass filtering said sensor signal to extract a signal component therefrom in a frequency range between approximately 20 and 40 Hz.

3. A method as claimed in claim 1 comprising bandpass filtering said sensor signal in a frequency range between 18 and 42 Hz.

4. A method as claimed in claim 1 comprising filtering said sensor signal in a second order, zero phase Butterworth filter.

5. A method as claimed in claim 1 wherein the step of filtering said sensor signal comprises:

filtering said sensor signal in a first filter to extract a signal component therefrom, as a first filtered signal, in said frequency range substantially higher than said heartbeat rate;

squaring said first filtered signal to obtain a squared signal;

filtering said squared signal in a second filter to obtain a second filtered signal;

differentiating said second filtered signal to obtain a first derivative with respect to time of said second filtered signal; and

providing said first derivative to said electronic detection unit as said power signal.

6. A method as claimed in claim 5 comprising employing a bandpass, second order, zero phase Butterworth filter as said first filter, and employing a low-pass, second order, zero phase Butterworth filter as said second filter.

7. A method as claimed in claim 1 comprising sampling said sensor signal before filtering said sensor signal.

8. A method as claimed in claim 1 comprising:

in said electronic detection unit, measuring the pre-ejection period a plurality of times during a predetermined time period;

in said electronic detection unit, measuring the ventricular ejection time said plurality of times during said predetermined time period;

in said electronic detection unit, determining the ejection fraction said plurality of times during said predetermined time period, to obtain a plurality of ejection fraction determinations that are represented in said output signal; and

supplying said output signal to a memory and storing said plurality of determined ejection fractions in said memory.

9. A method as claimed in claim 8 comprising reading out said plurality of determined ejection fractions from said memory from a location remote from said memory and said electronic detection unit.

10. A method as claimed in claim 1 comprising supplying said output signal to a therapy administration unit configured to interact with said mammalian subject to administer medical therapy to said mammalian subject, and automatically controlling administration of said medical therapy by said therapy administration unit dependent on the ejection fraction represented in said output signal.

11. An apparatus for measuring ejection fraction in a mammalian heart, comprising:

a sensor configured to sense opening and closing of a heart valve in the heart of a mammalian subject, and to generate a sensor signal representing said opening and closing of said heart valve, said heart exhibiting a heartbeat rate;

a filter supplied with said sensor signal that extracts a signal component therefrom, as a filtered signal, in a frequency range much higher than said heartbeat rate;

a squaring unit supplied with said filtered signal that squares said filtered signal to obtain a power signal; and

an electronic detection unit supplied with said power signal, said electronic detection unit being configured to measure, in said power signal, a pre-ejection period of said heart as a function of the sensed opening and closing of said heart valve, and to measure, in said power signal, a ventricular ejection time of said heart, and to automatically determine an ejection fraction of the heart as a function of the measured pre-ejection period and the measured ventricular ejection time, and to emit an electronic output signal representing said ejection function.

12. An apparatus as claimed in claim 11 wherein said filter is a bandpass filter that filters said sensor signal to extract a signal component therefrom in a frequency range between approximately 20 and 40 Hz.

13. An apparatus as claimed in claim 11 wherein said bandpass filtering filter passes said sensor signal in a frequency range between 18 and 42 Hz.

14. An apparatus as claimed in claim 11 wherein said filter is a second order, zero phase Butterworth filter.

15. An apparatus as claimed in claim 11 wherein said filter is a first filter that produces a first filtered signal, and comprising:

said squaring unit squaring said first filtered signal to obtain a squared signal;

a second filter that filters said squared signal to obtain a second filtered signal;

a differentiator that differentiates said second filtered signal to obtain a first derivative with respect to time of said second filtered signal and that provides said first derivative to said electronic detection unit as said power signal.

16. An apparatus as claimed in claim 15 wherein said first filter is a bandpass, second order, zero phase Butterworth filter, and said second filter is a low-pass, second order, zero phase Butterworth filter.

17. An apparatus as claimed in claim 11 comprising a sampling unit that samples said sensor signal before filtering said sensor signal in said filter.

18. An apparatus as claimed in claim 11 wherein said electronic detection unit is configured to measure the pre-ejection period a plurality of times during a predetermined time period, and to measure the ventricular ejection time said plurality of times during said predetermined time period, and to determine the ejection fraction said plurality of times during said predetermined time period, to obtain a plurality of ejection fraction determinations that are represented in said output signal, and wherein said apparatus comprises a memory supplied with said output signal to store said plurality of determined ejection fractions in said memory.

19. An apparatus as claimed in claim 18 comprising a telemetry unit configured to allow readout of said plurality of determined ejection fractions from said memory from a location remote from said memory and said electronic detection unit.

20. An apparatus as claimed in claim 11 comprising a therapy administration unit configured to interact with said mammalian subject to administer medical therapy to said mammalian subject, said therapy administration unit being supplied with said output signal and automatically controlling administration of said medical therapy dependent on the ejection fraction represented in said output signal.