Adaptive real time ECG triggering and uses thereof
View Patent ↗The present invention provides methods and apparatus for generating a trigger from the R wave of an electrocardiogram (ECG) waveform using a threshold that adapts to the slope of the R wave while still within the leading edge of the R wave.
1. A method of generating a trigger from an R wave of an electrocardiogram (ECG) waveform using a threshold that adapts to the slope of the R wave during a leading edge of the R wave, the method comprising using a processing unit for:
a) setting a threshold for the trigger, where the threshold is a percentage of the amplitude of the expected R wave;
b) measuring slopes of the R wave over successive small time periods during the leading edge of the R wave; where slopes corresponding to waveforms that include frequencies greater than the expected R wave prevent generation of a trigger;
c) adjusting the threshold for the trigger for the R wave during the leading edge of the R wave, where the threshold is increased if the slopes measured in b) are greater than expected for the R wave;
d) applying a scalar value to the slopes measured in b) to set a frequency above which signal frequencies are not considered valid for recognition as an R wave; and
e) generating a trigger during the leading edge of the R wave when the amplitude of the R wave reaches the threshold.
2. The method of claim 1 , wherein the amplitude of the expected R wave is normalized based on preceding R waves recorded from the same subject.
3. The method of claim 2 , wherein more recently occurring R waves are weighted more heavily in determining the amplitude of the expected R wave than less recently occurring R waves.
4. The method of claim 1 , wherein the threshold in step a) is set at ⅓ rd of the amplitude of the expected R wave.
5. The method of claim 1 , wherein the threshold in step a) is set at ½ of the amplitude of the expected R wave.
6. The method of claim 1 , wherein individual time periods in step b) are 1 msec to 5 msec in duration.
7. The method of claim 1 , wherein individual time periods in step b) are at least 4 msec in duration.
8. The method of claim 1 , wherein the successive time periods in step b) have a total duration of 16-40 msec.
9. The method of claim 1 , wherein slopes corresponding to waveforms that predominately have frequencies greater than or equal to 40 Hz are excluded from generating a trigger.
10. The method of claim 1 , wherein slopes corresponding to waveforms that predominately have frequencies greater than or equal to 30 Hz are excluded from generating a trigger.
11. The method of claim 1 , wherein the adjusted threshold is not allowed to exceed a maximum percentage of the amplitude of the expected R wave.
12. The method of claim 1 , wherein the adjusted threshold is not allowed to exceed ⅔ rd of the amplitude of the expected R wave.
13. The method of claim 1 , which further comprises excluding slopes corresponding to waveforms that predominately have frequencies less than or equal to 5 Hz from generating a trigger.
14. The method of claim 1 , which further comprises excluding slopes corresponding to waveforms that predominately have frequencies less than or equal to 10 Hz from generating a trigger.
15. The method of claim 1 , which further comprises requiring that a minimum number of changes in amplitude of the R wave measured over successive time periods in step b) are in the same direction of change in order to generate a trigger.
16. The method of claim 1 , which further comprises requiring that a change in amplitude of the R wave measured over a time period of the successive small time periods in step b) has a minimum change with respect to the change in amplitude measured over a preceding time period of the successive small time periods in order to generate a trigger.
17. The method of claim 1 , which further comprises increasing the threshold for the trigger in the presence of ECG Signals having a frequency component in the higher range expected for the R wave.
18. The method of claim 1 , which further comprises triggering an intra-aortic balloon pump (IABP) by the trigger generated during the leading edge of the R wave in step e).
19. The method of claim 1 , which further comprises triggering deflation of an intra-aortic balloon (IAB) by an intra-aortic balloon pump (IABP) by the trigger generated during the leading edge of the R wave in step e).
20. The method of claim 1 , which further comprises triggering a cardiac device by the trigger generated during the leading edge of the R wave in step e).
21. The method of claim 20 , wherein the cardiac device is a cardiac stimulator, a defibrillator, or an ECG monitor.
22. An apparatus for generating a trigger from an R wave of an electrocardiogram (ECG) waveform using a threshold that adapts to the slope of the R wave during a leading edge of the R wave, the apparatus comprising a processing unit for:
a) setting a threshold for the trigger, where the threshold is a percentage of the amplitude of the expected R wave;
b) measuring slopes of the R wave over successive small time periods during the leading edge of the R wave, where slopes corresponding to waveforms that include frequencies greater than the expected R wave prevent generation of a trigger;
c) adjusting the threshold for the trigger for the R wave during the leading edge of the R wave, where the threshold is increased if the slopes measured in b) are greater than expected for the R wave;
d) applying a scalar value to the slopes measured in b) to set a frequency above which signal frequencies are not considered valid for recognition as an R wave; and
e) generating a trigger during the leading edge of the R wave when the amplitude of the R wave reaches the threshold.
23. The apparatus of claim 22 , wherein the apparatus comprises an input from the electrocardiogram (ECG) of a subject.
24. The apparatus of claim 23 , wherein the apparatus comprises an input from the subject's arterial pressure.
25. The apparatus of claim 22 , wherein the apparatus comprises a processing unit for detecting cardiac arrhythmia from a subject's electrocardiogram (ECG) and/or from a subject's arterial pressure.
26. The apparatus of claim 22 , wherein the amplitude of the expected R wave is normalized based on preceding R waves in the ECG.
27. The apparatus of claim 26 , wherein more recently occurring R waves are weighted more heavily in determining the amplitude of the expected R wave than less recently occurring R waves.
28. The apparatus of claim 22 , wherein the threshold in a) is set at ⅓rd of the amplitude of the expected R wave.
29. The apparatus of claim 22 , wherein the threshold in a) is set at ½ of the amplitude of the expected R wave.
30. The apparatus of claim 22 , wherein individual time periods in b) are 1 msec to 5 msec in duration.
31. The apparatus of claim 22 , wherein individual time periods in b) are at least 4 msec in duration.
32. The apparatus of claim 22 , wherein the successive time periods in b) have a total duration of 16-40 msec.
33. The apparatus of claim 22 , wherein slopes corresponding to waveforms that predominately have frequencies greater than or equal to 40 Hz are excluded from generating a trigger.
34. The apparatus of claim 22 , wherein slopes corresponding to waveforms that predominately have frequencies greater than or equal to 30 Hz are excluded from generating a trigger.
35. The apparatus of claim 22 , wherein the adjusted threshold is not allowed to exceed a maximum percentage of the amplitude of the expected R wave.
36. The apparatus of claim 22 , wherein the adjusted threshold is not allowed to exceed ⅔ rd of the amplitude of the expected R wave.
37. The apparatus of claim 22 , wherein the processing unit excludes slopes corresponding to waveforms that predominately have frequencies less than or equal to 5 Hz from generating a trigger.
38. The apparatus of claim 22 , wherein the processing unit excludes slopes corresponding to waveforms that predominately have frequencies less than or equal to 10 Hz from generating a trigger.
39. The apparatus of claim 22 , wherein the processing unit requires that a minimum number of changes in amplitude of the R wave measured over successive time periods in step b) are in the same direction of change in order to generate a trigger.
40. The apparatus of claim 22 , wherein the processing unit requires that a change in amplitude of the R wave measured over a time period of the successive small time periods in step b) has a minimum change with respect to the change in amplitude measured over a preceding time period of the successive small time periods in order to generate a trigger.
41. The apparatus of claim 22 , wherein the processing unit increases the threshold for the trigger in the presence of ECG signals having a frequency component in the higher range expected for the R wave.
42. The apparatus of claim 22 , wherein the apparatus comprises an output that triggers an intra-aortic balloon pump (IABP).
43. The apparatus of claim 22 , wherein the apparatus comprises an output that triggers deflation of an intra-aortic balloon (IAB) by an intra-aortic balloon pump (IABP).
44. The apparatus of claim 22 , wherein the apparatus is incorporated in an intra-aortic balloon pump console system.