Identifying QRS point in ECG signal

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Stella Sim Jun Ni 2020-5-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/524664-identifying-qrs-point-in-ecg-signal

评论： Huy Le Van 2020-12-21

Hi guys, I'm trying to find the QRS point from the ECG signal that I had been given. I had found the R peak, however, I couldn't code the Q and S point. Can someone please help me to check my coding if there is something wrong with it?

load('Sample_1.mat')
%The recording were digitized at 360 seconds per second with 11 bits
%resolution over mV range.
length(Orig_Sig) = 3600;
D = 1:3600;
t = D./360;
Fs = 360;
%plot noisy signal 
figure
subplot(211), plot(t,Orig_Sig);
title('Original ECG Signal')
%lowpass Butterworth filter
fNorm = 25 / (Fs/2);
[b,a] = butter(10, fNorm, 'low');
y =filtfilt(b, a, Orig_Sig);
subplot(212), plot(t,y);
title('Filtered ECG Signal')
[R1,TR1] = findpeaks(y,t,'MinPeakHeight',1000);
[Q1,TQS1] = findpeaks(-y,t,'MinPeakHeight',-850,'MinPeakDistance',0.5);
figure
plot(t,y)
hold on
plot(TR1,R1,'^r')
plot(TQS1(1:2:end), -Q1(1:2:end), 'vg')
plot(TQS1(2:2:end), -Q1(2:2:end), 'vb')
hold off

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Huy Le Van 2020-12-21

Hi. Follow me, you can be reference this code.

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采纳的回答

Star Strider 2020-5-11

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/524664-identifying-qrs-point-in-ecg-signal#answer_431808

That is an interesting EKG. It displays frequent unifocal PVCs with obvious retrograde conduction, blocking the subsequent P-wave.

As much as I like findpeaks, the islocalmin function might be more appropriate, since you can use the ProminenceWindow name-value pair, and others not available in findpeaks. That might be easier with respect to locating the Q and S waves. In any event, the findpeaks MinPeakProminence parameter with or in place of MinPeakHeight may be more valuable than MinPeakHeight alone.

Also, the 25 Hz lowpass filter cutoff frequency is a bit restrictive and could obscure some detail. Experiment with a 45 Hz cutoff and see if that improves your ability to detect the Q and S deflections.