Method and apparatus for determining information indicative of cardiac malfunctions and abnormalities
An apparatus for determining information indicative of cardiac malfunctions and abnormalities includes a processing device ( 402 ) configured to extract, from a signal indicative of electromagnetic phenomena related to cardiac activity, a first wave pattern repeating on a heart-beat rate and, from a signal indicative of cardiovascular motion, a second wave pattern repeating on the heart-beat rate. The processing device is configured to form timing data such that each timing value of the timing data is indicative of a time period from a reference point of the first wave pattern belonging to one heart-beat period to a reference point of the second wave pattern belonging to the same heart-beat period. The processing device is configured to determine, at least partly on the basis of the timing data, an indicator of cardiac malfunction and abnormality.
1. An apparatus comprising:
a signal interface for receiving a first signal indicative of electromagnetic cardiac activity and a second signal indicative of cardiovascular motion, and
a processing device coupled to the signal interface,
the processing device being arranged and configured to:
extract from the first signal a first wave pattern repeating on a heart-beat rate and from the second signal a second wave pattern repeating on the heart-beat rate,
form timing data, each timing value of which being indicative of a time period from a reference point of the first wave pattern belonging to one heart-beat period to a reference point of the second wave pattern belonging to the same heart-beat period,
determine a correlation between the timing data and pacing data indicative of the heart-beat rate,
produce, on the basis of the correlation, a third signal indicative of cardiac malfunction and abnormality, and
make the third signal available to a user external to the processing device,
wherein the processing device is configured to compute a correlation coefficient indicative of the degree of the correlation between the timing data and the pacing data:
C ( j )= E {( TD−μ T )×( PD−μ P )},
where C(j) is the correlation coefficient, E is the expected value operator, TD is the timing data, μ T is the mean of the timing data, PD is the pacing data, μ P is the mean of the pacing data, and j is an integer expressing a time-lag of the pacing data with respect to the timing data in heart-beat periods.
2. The apparatus according to claim 1 , wherein the apparatus further comprises a first sensor element for measuring the first signal and a second sensor element for measuring the second signal.
3. The apparatus according to claim 2 , wherein the second sensor element comprises one of the following: an accelerometer, a piezo-electronic sensor, an inclinometer, a pressure sensor.
4. The apparatus according to claim 1 , wherein the processing device is configured to extract from the first signal the R-peak and from the second signal the AO-peak, the R-peak being caused by depolarization of the ventricular muscle tissue and representing the first wave pattern repeating on the heart-beat rate on the first signal, and the AO-peak being caused by opening of the aortic valve and representing the second wave pattern repeating on the heart-beat rate on the second signal.
5. The apparatus according to claim 4 , wherein the processing device is configured to use the top of the R-peak as the reference point of the first wave pattern and the top of the AO-peak, the top of the J-peak, or the deepest point of the valley between the MC-peak and the AO-peak as the reference point of the second wave pattern.
6. The apparatus according to claim 4 , wherein the processing device is configured to low-pass filter the second signal indicative of the cardiovascular motion and to detect the AO-peak from the low-pass filtered signal.
7. The apparatus according to claim 6 , wherein an upper limit frequency of the low-pass filtering is 30 Hz.
8. The apparatus according to claim 4 , wherein the processing device is configured to band-pass filter the second signal indicative of the cardiovascular motion and to detect AC-peaks from the band-pass filtered signal, the AC-peaks being caused by closures of the aortic valve.
9. The apparatus according to claim 8 , wherein a pass-band of the band-pass filtering is from 40 Hz to 100 Hz.
10. The apparatus according to claim 8 , wherein the processing device is configured to detect temporal lengths of AC-AO intervals and to compute a time variation quantity indicative of strength of variation of the detected temporal lengths of the AC-AO intervals, each of the AC-AO intervals being a time interval from one of the AC-peaks to the following one of the AO-peaks and the time variation quantity being indicative of cardiac malfunction and abnormality.
11. The apparatus according to claim 8 , wherein the processing device is configured to detect temporal lengths of AC-AO intervals and temporal lengths of AO-AO intervals and to compute a first ratio quantity indicative of a ratio between the temporal length of the AC-AO interval and the temporal length of the AO-AO interval within a same heart-beat period, each of the AC-AO intervals being a time interval from one of the AC-peaks to the following one of the AO-peaks, each of the AO-AO intervals being a time interval from one of the AO-peaks to the following one of the AO-peaks, and the first ratio quantity being indicative of cardiac malfunction and abnormality.
12. The apparatus according to claim 8 , wherein the processing device is configured to configured to detect temporal lengths of AC-R intervals and temporal lengths of R-R intervals and to compute a second ratio quantity indicative of a ratio between the temporal length of the AC-R interval and the temporal length of the R-R interval within a same heart-beat period, each of the AC-R intervals being a time interval from one of the AC-peaks to the following one of the R-peaks, each of the R-R intervals being a time interval from one of the R-peaks to the following one of the R-peaks, and the second ratio quantity being indicative of cardiac malfunction and abnormality.
13. The apparatus according to claim 1 , wherein the processing device is configured to determine variation of the timing data corresponding to a substantially constant heart-beat rate, the degree of the variation being indicative of cardiac malfunction and abnormality.
14. The apparatus according to claim 13 , wherein the processing device is configured to determine a variation-quantity indicative of the degree of the variation of the timing data:
V
=
E
{
TD
-
μ
T
)
2
}
μ
T
,
where V is the variation-quantity, E is the expected value operator, TD is the timing data, and μ T is the mean of the timing data at the heart-beat rate under consideration.
15. The apparatus according to claim 1 , wherein the processing device is configured to detect time periods between successive R-peaks on the first signal in order to obtain the pacing data, the detected time periods being indicative of the heart-beat rate as being inversely proportional to the heart-beat rate.
16. The apparatus according to claim 1 , wherein the processing device is configured to form the pacing data so that each value of the pacing data represents an instantaneous value of the heart-beat rate, and produce a signal expressing atrial fibrillation in response to a situation in which the correlation coefficient is greater than a threshold.
17. The apparatus according to claim 16 , wherein the processing device is configured to use zero as the threshold.
18. A method comprising a processing device performing the steps of:
extracting, from a first signal indicative of electromagnetic cardiac activity, a first wave pattern repeating on a heart-beat rate, and extracting, from a second signal indicative of cardiovascular motion, a second wave pattern repeating on the heart-beat rate,
forming timing data, each timing value of which being indicative of a time period from a reference point of the first wave pattern belonging to one heart-beat period to a reference point of the second wave pattern belonging to the same heart-beat period, determining a correlation between the timing data and pacing
data indicative of the heart-beat rate,
producing, on the basis of the correlation, a third signal indicative of cardiac malfunction and abnormality,
making the third signal available to a user external to the processing device, and
computing a correlation coefficient indicative of the degree of the correlation between the timing data and the pacing data:
C ( j )= E {( TD−μ T )×( PD−μ P )},
where C(j) is the correlation coefficient, E is the expected value operator, TD is the timing data, μ T is the mean of the timing data, PD is the pacing data, μ P is the mean of the pacing data, and j is an integer expressing a time-lag of the pacing data with respect to the timing data in heart-beat periods.
19. The method according to claim 18 , wherein the method comprises extracting from the first signal the R-peak and from the second signal the AO-peak, the R-peak being caused by depolarization of the ventricular muscle tissue and representing the first wave pattern repeating on the heart-beat rate on the first signal, and the AO-peak being caused by opening of the aortic valve and representing the second wave pattern repeating on the heart-beat rate on the second signal.
20. The method according to claim 19 , wherein the top of the R-peak is the reference point of the first wave pattern and the top of the AO-peak, the top of the J-peak, or the deepest point of the valley between the MC-peak and the AO-peak is the reference point of the second wave pattern.
21. The method according to claim 19 , wherein the method comprises low-pass filtering the second signal indicative of the cardiovascular motion and detecting the AO-peak from the low-pass filtered signal.
22. The method according to claim 21 , wherein an upper limit frequency of the low-pass filtering is 30 Hz.
23. The method according to claim 19 , wherein the method comprises band-pass filtering ( 211 ) the second signal indicative of the cardiovascular motion and detecting ( 212 ) AC-peaks from the band-pass filtered signal, the AC-peaks being caused by closures of the aortic valve.
24. The method according to claim 23 , wherein a pass-band of the band-pass filtering is from 40 Hz to 100 Hz.
25. The method according to claim 23 , wherein the method comprises detecting temporal lengths of AC-AO intervals and computing a time variation quantity indicative of strength of variation of the detected temporal lengths of the AC-AO intervals, each of the AC-AO intervals being a time interval from one of the AC-peaks to the following one of the AO-peaks and the time variation quantity being indicative of cardiac malfunction and abnormality.
26. The method according to claim 23 , wherein the method comprises detecting temporal lengths of AC-AO intervals and temporal lengths of AO-AO intervals and computing a first ratio quantity indicative of a ratio between the temporal length of the AC-AO interval and the temporal length of the AO-AO interval within a same heart-beat period, each of the AC-AO intervals being a time interval from one of the AC-peaks to the following one of the AO-peaks, each of the AO-AO intervals being a time interval from one of the AO-peaks to the following one of the AO-peaks, and the first ratio quantity being indicative of cardiac malfunction and abnormality.
27. The method according to claim 23 , wherein the method comprises detecting temporal lengths of AC-R intervals and temporal lengths of R-R intervals and computing a second ratio quantity indicative of a ratio between the temporal length of the AC-R interval and the temporal length of the R-R interval within a same heart-beat period, each of the AC-R intervals being a time interval from one of the AC-peaks to the following one of the R-peaks, each of the R-R intervals being a time interval from one of the R-peaks to the following one of the R-peaks, and the second ratio quantity being indicative of cardiac malfunction and abnormality.
28. The method according to claim 18 , wherein the determining ( 204 ) of the indicator of cardiac malfunction and abnormality comprises determining variation of the timing data corresponding to a substantially constant heart-beat rate, the degree of the variation being indicative of cardiac malfunction and abnormality.
29. The method according to claim 28 , wherein a variation-quantity indicative of the degree of the variation of the timing data is computed:
V
=
E
{
TD
-
μ
T
)
2
}
μ
T
,
where V is the variation-quantity, E is the expected value operator, TD is the timing data, and μ T is the mean of the timing data at the heart-beat rate under consideration.
30. The method according to claim 18 , wherein the method comprises detecting time periods between successive R-peaks on the first signal in order to obtain the pacing data, the detected time periods being indicative of the heart-beat rate as being inversely proportional to the heart-beat rate.
31. The method according to claim 18 , wherein each value of the pacing data represents an instantaneous value of the heart-beat rate and the method comprises producing a signal expressing atrial fibrillation in response to a situation in which the correlation coefficient is greater than a threshold.
32. The method according to claim 31 , wherein the threshold is zero.
33. A non-transitory computer readable medium encoded with a computer program comprising computer executable instructions for causing a programmable processor to:
extract, from a first signal indicative of electromagnetic cardiac activity, a first wave pattern repeating on a heart-beat rate,
extract, from a second signal indicative of cardiovascular motion, a second wave pattern repeating on the heart-beat rate,
form timing data, each timing value of which being indicative of a time period from a reference point of the first wave pattern belonging to one heart-beat period to a reference point of the second wave pattern belonging to the same heart-beat period,
determine correlation between the timing data and pacing data indicative of the heart-beat rate,
produce, on the basis of the correlation, a third signal indicative of cardiac malfunction and abnormality,
make the third signal available to a user external to the programmable processor, and
compute a correlation coefficient indicative of the degree of the correlation between the timing data and the pacing data:
C ( j )= E {( TD−μ T )×( PD−μ P )},
where C(j) is the correlation coefficient, E is the expected value operator, TD is the timing data, μ T is the mean of the timing data, PD is the pacing data, μ P is the mean of the pacing data, and j is an integer expressing a time-lag of the pacing data with respect to the timing data in heart-beat periods.