RR interval extraction from ECG

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Luca Merolla 2020-8-27

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https://ww2.mathworks.cn/matlabcentral/answers/585227-rr-interval-extraction-from-ecg

评论： Star Strider 2020-9-7

Hello there!

I am approaching for the first time to ECG analysis to extract the RR interval and, ultimately, compute a PSD estimation using Welch's periodogram. As far as I know, the wavelet method is the most common and the most reliable, but I find it difficult to understand.

Can anyone give me some advice regarding how to analyse ECG data? For example, why do we need to decompose the signal into different levels? And what do those levels mean? Does anyone know other methods to extract the RR interval?

For the moment I am working with the MIT-BIH database.

Thanks to anyone who's willing to help!

Luca

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采纳的回答

Star Strider 2020-8-27

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https://ww2.mathworks.cn/matlabcentral/answers/585227-rr-interval-extraction-from-ecg#answer_485810

If you only want the locations of the R-waves in a normal EKG, use findpeaks or islocalmax.

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Luca Merolla 2020-9-7

在 MATLAB Online 中打开

Hello Star Strider!

Sorry that I keep coming back to this, but could you explain to me why, in this example, after recomposing the signal they plot the squared absolute values?

I plotted both the squared absolute values and the non-squared absolute values and I can't see any difference between the two.

The lines I am referring to are:

wt = modwt(ecgsig,5);
wtrec = zeros(size(wt));
wtrec(4:5,:) = wt(4:5,:);
y = imodwt(wtrec,'sym4');

Where they decompose the ECG waveform with modwt, and then recompose it with imodwt. Then they use findpeaks on the squared absolute values of the signal:

y = abs(y).^2;
[qrspeaks,locs] = findpeaks(y,tm,'MinPeakHeight',0.35,...
    'MinPeakDistance',0.150);

Star Strider 2020-9-7

That the squared absolute value does not make a difference in your EKG may simply mean that all the identified R-waves are all greater than 0. Note that in the EKG in that example, many of the R-waves are negative, and those same complexes show peaked T-waves. (This likely indicates an intraventricular conduction system pathology, with aberrant activation. I would have to know more to be sure.) Taking the squared absolute value may not be necessary for the EKGs you are studying.

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