MATLAB: Plot inverse of ECG signal

ecgekgelectrocardiogramheart rateheart rate variabilityimage analysissignal processing

I have a 1×4000 vector of ECG data. The data seems to be plotted upside down with the R wave facing downwards. I would like to invert the plot/data for peak detection analysis but seem to be having trouble. When I use the flipud/inv/pinv commands I get no change in the data plots. What can I try next?

Thanks

Best Answer

That could be normal, depending on the lead, for example in aV_R or V_1.

If you want to invert it, the easiest way is simply to negate it, multiplying it by -1.

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It looks like a normal Lead II EKG 10 second rhythm strip with a regular rhythm and a rate of about 66. The S-wave is near the end of the QRS complex, so the easiest way to detect the S-wave is to first identify the preceding R wave, get the index (since this is most likely a data vector), and look for the minimum in the next 5 milliseconds. (It’s easiest to do this in terms of data vector indices, but you have to know the sampling rate to do the conversion. The sampling rate isn’t stated.) In this tracing, that minimum should be the S-wave. Store the indices of the S-waves in a vector, then plot your markers at the time and EKG values corresponding to the vector of S-wave indices.

MATLAB: ECG data heart rate

Here's an example from the documentation of how to get data from physionet. Here's another example of getting the data directly from GiHub.

You could try looking at some of the example data in MATLAB.

load arrhythmia.mat
load ecg_signals.mat
load ecgsignal_test.mat

You may also find this example helpful, as it discussed actually calculating heart rate.

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MATLAB: ECG data heart rate

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