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Artefacts on ECG making it difficult to interpret!!!


One of the probably most commonly seen pattern on ecg is the above! 

“A regular & high-frequency "caterpillar" pattern, making it almost difficult to interpret the true underlying electrical activity of the heart!!!”

This is also known as 60 hz or 60 cycle interference on ecg! 

This is Common to areas where the source of electricity is “AC”With frequency of 60 hz !!! There electrical current can leak into other circuits and can results in this pattern on ecg .

To help minimize 60 cycle interference one can set the mode of the 12-lead ECG monitor to 0.05 – 40 Hz!!!!!

Electromagnetic interference (EMI) is defined as unwanted noise / artifacts/ interference in an electrical path or circuit caused by an outside of heart source. 


Most Drs especially the jnr Drs do not have an understanding of the issue or how to resolve the problem and unfortunately accept ECG interference as something like normal !!!!

Fatal arrhythmias may therefore go unnoticed! , and one can be confused or misled to believe that this information is accurate or May even result in unnecessary interventions!!!


The standard ECG machine is designed though to pick up only the electrical activity within the heart but it can pick up any electrical activity from any nearby sources like machinery, Pumps, TV.


In spite of many improvements in the latest patient monitors & ECG machines, but EMI has been a problem for last so many decades! and unfortunately continues to be an issue

Even today. 


EMI artifacts usually results from the foll sources!!!

A. Electrical equipment like 

Power lines 

electrical wires in walls/ceilings, any other electrical devices 
B.Mobile phones

Cell phones, especially when activated and near the ECG machine, can produce EMI. 
C.Wireless devices 

Wireless local area networks (WLAN) 

other wireless technologies
D.Medical equipment

intravenous infusion pumps dialysis machines

E. Poor grounding: 

Inadequate grounding can always allow stray currents to enter the circuit, resulting in noise and further artifacts. 



Several Methods to reduce/minimise/eradicate EMI !!!


A. Better use of Filters! 

All ECG machines have filters (like high-pass, low-pass, and notch filters) to eradicate the unwanted frequencies and improve signal the clarity. 

If the low frequency / high pass filter (the lowest number) is set to 0.05 Hz one may be able to get near clean ST-segments !!!

B. Devices removal: 

Turning off or removing devices causing EMI, such as cell phones, can help. 
making sure to keep ECG machines and patients away from sources of EMI! 
C. Signal conditioning

Signal conditioning techniques can help remove noise and improve ECG signal quality. 

If possible, running the recording equipment off batteries to avoid picking up line noise.


Thanks


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