Read about the latest news on ECG / EKG Machines

Did you ever notice that there seem to be almost two EKGs? There is the constant beeping that becomes an eerie whine when the patient heart stops beating. And then there is the report format that can be charted, argued over, and with dramatic pause, becomes the exciting conclusion of the latest medical drama.

Both of these are based on real medical science. As the signals come in from the leads on a patient, they pass through filters as the signals are processed. A low frequency filter is set at the low end of the hertz scale. Hertz is the number of waves a signal has. While this scale can measure sound waves, here is used for measurement of electric waves. Alternatively, the high frequency filter is set at the high end of the scale.

To further complicate a simple discussion of the subject, the low frequency filter is called the high pass filter; this means that only signals above a certain setting are allowed to pass on through to the computer. The high frequency filter is called the low pass filter; this means that only signals below a certain setting are allowed to pass on through to the computer. For the purpose of this article, they will be called low frequency and high frequency filters.

How these filters are set determines the two most common settings of an EKG machine. The monitor mode has the low frequency filter set at either 0.5 hertz or 1 hertz. The high frequency filter is set at 40 hertz. These settings not only decrease the detail of the parts of the heart beat, but also decrease the extraneous noise that comes across the electric leads and the circuits within the machine itself. For a cycle of continuous monitoring, this is more than acceptable.

On the other hand, the diagnostic mode has the low frequency filter set even lower (0.05 hertz,) allowing more detail to be recorded, especially in the ST segment of the heart stimulatory cycle. The high frequency filter is set at 40, or 100 or even higher to catch greater variations in the signals of the heart across the range of the signals.

This means that the monitoring mode display is more filtered than the diagnostic mode. A higher level of interference is the price to be paid for the greater detail. Remember, an EKG is a tool. It is the interpretation of the results that is key to the value of the test.

Technorati Tags: EKG, ekg machine, medical equipment