How to filter the noise out from the ECG signal

The original ECG signal looks like this, the sampling frequency is 360Hz.

I try to design a FIR filter to filter the noise out so that i can get a clear view of PQRST complex of the heart beat. I plot this signal in the frequency domain and it looks like this:

So, how should I fiind the frequency where the noise locates?

[Jonas]

you want only the high peaks? you could just use thresholding and set values that are smaller as e.g. 100mV to 0

[YanBo Liu]

Hi, Jonas. For exmaple, this is the one of the parts of my original signal:

And this is what PQRST should look like:

Obviously, there are some noises in the original signal and i just want to filter these noises out to get "P Q R S T" from the first figure(R Q S are clear enough but P T are not).

[Jonas]

i suggest you play around using the signal analyzer app.

https://de.mathworks.com/help/signal/ug/using-signal-analyzer-app.html

tomorrow i will have a closer look!

[Star Strider]

There is obvious 60 Hz line noise. Use a bandstop filter with a very narrow stopband to eliminate it.

Beyond that, it appears to represent normal sinus rhythm with left ventricular hypertophy with non-specific ST-T changes and one notable PVC. If this is a Lead II EKG, the origin of the PVC appears to be near the apex. There are Q-waves, however without a specific voltage calibration, it is difficult to interpret their significance.

Answer 1

[M.B]

I would also recommend a zero-phase filter using filtfilt function to avoid the introduction of phase lag after filtering the signal.

https://au.mathworks.com/help/signal/ref/filtfilt.html

Answer 2

[Ganesh]

mat lab code

Answer 3

[Ganesh]

Code for that