Electrocardiograph is a harmful instrument. However, it is a potentially harmful medical device to users, and the existing methods can provide sufficient guarantee. Only after passing the test of implementing standardized management and the review of 5 10K (pre-listing notice) can it be put on the market for sale.
The harm of ECG machine to people is controlled within an acceptable range, but it is beneficial to check and treat heart disease.
Any examination has different degrees of influence or damage to the human body. Relatively speaking, the benefits of inspection must far outweigh the damage. For example, X-ray, CT and nuclear magnetic resonance have great radiation to human body. If you are afraid of radiation and don't check it, many diseases will not be found, and finally treatment will be delayed.