How to find the QRS complex for this ECG signal?

Question

Susan 2022-12-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1874382-how-to-find-the-qrs-complex-for-this-ecg-signal

评论： Susan 2022-12-13

采纳的回答： William Rose

ECG.mat

Hi all,

Could somebody please tell me how I can find the QRS complexes of this ECG signal? The signal is attached.

Thanks in advance!

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William Rose 2022-12-10

@Susan,

The 10 Hz spikes are basically the same height a a normal R wave in the absence of spikes, so it is not surprising that you might fail to identify an occasional lower-than-average-amplitude R wave. Of course you will want to identify and eliminate the source of the 10 Hz spikes if at all possible, in future recordings. Maybe that it impossible, for example if it is an indwelling stimulator or some other therapeutic device. You may have to live with a compromise in which you have occasional false positives (i.e. calling something an R wave when it is not) and false negatives (i.e. failing to identify real R waves). This occurs in many clinical scenarios. Finding the right balance depends on the costs of the different types of errors. You will have no better guide that @Star Strider in such matters.

I sympathize with your situation. I once recorded a very low quality EKG because I had not turned up the amplifier gain as normal, and did not catch the error. As a result, the R waves were almost buried in noise. But the experimental data was valuable, so I made quite an effort to filter out the noise to extract the R waves. And I added a checklist item to make sure I did not make that mistake again.

William Rose 2022-12-12

@Susan, I am not a cardiologist or a physician. But I am confident that the 10 Hz spikes would not be interpreted as a pathology. The physician would immediately recognize that there was a problem with the recording. Maybe the circuit used to amplify and record the ECG has a flaw in it that generates 10 Hz spikes. Maybe the spikes are due to crosstalk from another device in the room. Maybe the subject has some implantable device that generates pulses at 10 Hz. If that were true, the physician would know it, so the spikes would not be misinterpreted.

This ECG is not acceptable for clinical use. If the spikes were much narrower, they could be removed by signal processing, without too much risk of causing significant distortion of the true signal. But they are wide as well as tall.

I have not seen spikes like this at 2 or 10 or 40 Hz, but my experience is quite limited, with only a few hundred subjects. I have recorded ECGs with clinical-grade machines, with teaching machines, and with amplifiers I designed and built myself. I have recorded in the cardiac cath lab and in teaching labs and in research labs and in the field.

If you collected the data, then you probably have ideas about the possible source of the spikes.

Susan 2022-12-13

@William Rose Thank you so much for your response. It's helpful. Appreciate it!

William Rose 2022-12-13

@Susan, you're welcome. Good luck with your work.

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Answer 1

William Rose 2022-12-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1874382-how-to-find-the-qrs-complex-for-this-ecg-signal#answer_1127177

ECG.mat

@Susan,

Perhaps the comments above constitute an answer to your question.

ECGs=load('ECG');

ECG=ECGs.ECG;

L = numel(ECG);

t = linspace(0, L-1, L)/1024;

[pks,locs] = findpeaks(ECG,'MinPeakDistance',2,'MinPeakHeight',max(ECG)*0.6846);

%[pks,locs] = findpeaks(ECG,'MinPeakDistance',2,'MinPeakHeight',.48);

figure

subplot(311), plot(t, ECG, '-r',t(locs), pks, '^r')

xlabel('Time (s)'); grid on

subplot(312), plot(t, ECG, 'r-',t(locs), pks, '^k')

xlim([0 5]); xlabel('Time (s)'); grid on

subplot(313), plot(t, ECG, '.r-',t(locs), pks, '^k')

xlim([4 5]); xlabel('Time (s)'); grid on

The 10 Hz spikes are a bit narrower than the QRS complexes, so it should be possible to identify the QRS complexes based on that, plus the peak height excedigng approximately 0.4. This should allow you to find all of the R waves.

Was the subject paced? The R-R intervals appear to be too even for unpaced beats.

Good luck.

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William Rose 2022-12-13

@Susan, Let's continue the discussion offline. Please send me secure email by clicking the WR circle next to my name, then click on the envelope icon.

Susan 2022-12-13