R-wave detector circuit for sensing cardiac signals

• US 6,377,844 B1
• Filed: 03/13/1999
• Issued: 04/23/2002
• Est. Priority Date: 03/13/1999
• Status: Expired due to Fees

• Current Assignee: Dave Graen
• Original Assignee: Dave Graen
• Inventors: Graen, Dave
• Primary Examiner(s): Bockelman, Mark
• Application Number:
  US09/268,092
• Time in Patent Office: 1,137 Days
• Field of Search: 600/508-528
• US Class Current: 600/521
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

Method and apparatus for measuring the heart rate in a human body. A first and second derivative of an electrical signal from the heart known as the QRS complex or R-wave is measured, and the values of the peak of the R-wave, the peak of the first derivative of the R-wave, and the peak of the second derivative of the R-wave are determined. The three peak values are then multiplied together to provide an output responsive to the occurrence of the R-wave which is greater than either the value of the peak of the R-wave, the value of the peak of the first derivative of the R-wave, or the value of the peak of the second derivative of the R-wave.

Claims

1. An apparatus for detecting an electrical cardiac voltage signal, comprising:

a. signal conditioner adapted to be coupled to the electrical cardiac voltage signal for providing a number of conditioned voltage signals; and

b. signal combiner coupled to the signal conditioner for combining the number of conditioned voltage signals to provide a combined voltage signal being distinguishable from each one of the number of conditioned voltage signals wherein the signal conditioner is a differentiator which calculates a number of derivatives of the electrical cardiac voltage signal and provides each one of the number of derivatives as one of the number of conditioned voltage signals, each one of the number of conditioned voltage signals having a magnitude which corresponds to a different order derivative of the electrical cardiac voltage signal than every other one of the number of derivatives.

2. An apparatus according to claim 1 wherein the magnitude of each one of the number of conditioned voltage signals corresponds to a peak value of the corresponding one of the number of derivatives.

3. An apparatus according to claim 1 wherein the signal combiner combines the number of conditioned voltage signals algebraically to provide the combined voltage signal, the combined voltage signal having a magnitude which is distinguishable from a magnitude of each one of the number of conditioned voltage signals.

4. An apparatus according to claim 3 wherein the signal combiner is a multiplier which combines the number of conditioned voltage signals by multiplying the number of conditioned voltage signals together to produce a product voltage which corresponds to a product of the number of conditioned voltage signals, the product voltage having a magnitude which is greater than a magnitude of any one of the number of conditioned voltage signals.

5. An apparatus according to claim 1 wherein the magnitude of each one of the number of conditioned voltage signals corresponds to a fraction of the peak value of the corresponding one of the number of derivatives.

6. An apparatus according to claim 1 wherein one of the number of derivatives of the electrical cardiac voltage signal is a zero order derivative of the electrical cardiac voltage signal.

7. An apparatus according to claim 1 wherein one of the number of derivatives of the electrical cardiac voltage signal is a first order derivative of the electrical cardiac voltage signal.

8. An apparatus according to claim 1 wherein one of the number of derivatives of the electrical cardiac voltage signal is a second order derivative of the electrical cardiac voltage signal.

9. An apparatus according to claim 1 wherein the electrical cardiac voltage signal is an R-wave.

10. An apparatus for detecting an electrical cardiac signal, comprising:

a. differentiator means adapted to be coupled to the cardiac signal for providing a number of voltage values, each one of the number of voltage values corresponding to a different order derivative of the cardiac signal than every other one of the number of voltage values; and

b. algebraic means coupled to the differentiator means for performing one or more operations on the number of voltage values to produce a result which has a greater magnitude than any one of the number of voltage values.

11. An apparatus according to claim 10 wherein the one or more operations are one or more multiplication operations and the result is a product of the number of voltage values.

12. An apparatus according to claim 10 wherein at least one of the number of voltage values corresponds to a zero order derivative of the cardiac signal.

13. An apparatus according to claim 12 wherein the at least one of the number of voltage value has a magnitude which corresponds to a peak value of the zero order derivative of the cardiac signal.

14. An apparatus according to claim 10 wherein at least one of the number of voltage values corresponds to a first order derivative of the cardiac signal.

15. An apparatus according to claim 14 wherein the at least one of the number of voltage values has a magnitude which corresponds to a peak value of the first order derivative of the cardiac signal.

16. An apparatus according to claim 10 wherein at least one of the number of voltage values corresponds to a second order derivative of the cardiac signal.

17. An apparatus according to claim 16 wherein the at least one of the number of voltage values has a magnitude which corresponds to a peak value of the second order derivative of the cardiac signal.

18. An apparatus according to claim 10 wherein the cardiac signal is an R-wave.

19. A sensing system for detecting an electrical cardiac signal, comprising:

a. a differentiator circuit adapted to be operably coupled to the cardiac signal for providing a number of derivatives of the cardiac signal;

b. a peak detector circuit operably coupled to an output of the differentiator circuit for providing a number of voltage values, each one of the number of voltage values corresponding to one on the number of derivatives of the cardiac signal; and

c. an algebraic circuit operably coupled to an output of the peak detector circuit for performing one or more operations on the number of voltage values to produce a voltage result having a magnitude which is greater than any one of the number of voltage values.

20. A sensing system according to claim 19 wherein the algebraic circuit is a multiplier circuit and the one or more operations are one or more multiplication operations, the multiplier circuit multiplying the number of voltage values together to provide a product of the number of voltage values, the product of the number of voltage values having a magnitude which is greater than any one of the number of voltage values.

21. A sensing system according to claim 19 wherein at least one of the number of voltage values is a peak voltage value of a zero order derivative of the cardiac signal.

22. A sensing system according to claim 19 wherein at least one of the number of voltage values is a peak voltage value of a first order derivative of the cardiac signal.

23. A sensing system according to claim 19 wherein at least one of the number of voltage values is a peak voltage value of a second order derivative of the cardiac signal.

24. A sensing system according to claim 19 further comprising a fraction of peak detection circuit coupled to an output of the algebraic circuit for providing a voltage output in response to the voltage output of the algebraic circuit when the voltage output of the algebraic circuit has a magnitude which is greater than a predetermined level.

25. A sensing system according to claim 19 wherein the cardiac signal is an R-wave.

26. A sensing system for detecting an electrical cardiac signal, comprising:

a. a first differentiator circuit adapted to be operably coupled to the cardiac signal for providing a first derivative of the cardiac signal;

b. a second differentiator circuit operably coupled to an output of the first differentiator circuit for providing a second derivative of the cardiac signal;

c. a first peak detector circuit adapted to be operably coupled to the cardiac signal for providing a peak voltage value to the cardiac signal;

d. a second peak detector circuit operably coupled to the output of the first differentiator circuit for providing a peak voltage value of the first derivative of the cardiac signal;

e. a third peak detector circuit operably coupled to an output of the second differentiator circuit for providing a peak voltage value of the second derivative of the cardiac signal; and

f. a multiplier circuit operably coupled to an output of the first peak detector circuit, an output of the second peak detector circuit, and an output of the third peak detector circuit for multiplying the peak voltage values of the cardiac signal, the second derivative of the cardiac signal together to provide a voltage output which is greater in magnitude than the peak voltage value of the cardiac signal, the peak voltage value of the first derivative of the cardiac signal, or the peak voltage value of the second derivative of the cardiac signal.

27. A sensing system according to claim 26 further comprising a fraction of peak detection circuit coupled to the output of the multiplier circuit for providing a voltage output in response to the voltage output of the multiplier circuit when the voltage output of the multiplier circuit is greater than a predetermined level.

28. A sensing system according to claim 26 wherein the cardiac signal is an R-wave.