MESI mTABLET ECG is designed to adapt to your professional environment. Various filter settings intended for removing unwanted artifact and noise are capable of improving the legibility of the signal without modifying its morphology of the ECG measurements you perform.
During the ECG measurement with MESI mTABLET ECG, the recording screen is comprised from the 12-lead signal displayed in real time and recording settings. At the same time, it displays the electrode connection status which will notify you if the applied electrode has good or a bad signal strength. If the patient has a pacemaker, the PACE indicator will light up next to electrode status.
Fast buttons are there to change between most common filters, recording speed and sensitivity. By pressing on the button repeatedly, you can switch between the following options:
- Myogram filter button rotates between 25 Hz, 35 Hz and “off” options
- Sensitivity button changes the amplitude settings between 5, 10, 20 mm/mV
- Recording speed button rotates between 12, 25, 50 mm/s values
All the devices come with default settings which we deem to be best for general use; these settings can be adapted at any time or restored by selecting “default settings” in the ECG settings screen.
Activation of the filters influences both the displayed and the printed signal. To guarantee a correct and accurate analysis, any automatic interpretation of the trace is performed always and only on the non-filtered ECG signal.
The low-pass filter filters various high frequency muscle artifact and external interference – noise generated by nearby electronic devices. The 150Hz setting clears most of the signal. If, however, you require less filtering, the setting should be set to 250Hz.
High-pass filter (baseline filter)
Baseline filter is used to remove low-frequency components such as motion artifact, respiratory variation, and baseline wander. Three settings (0.5Hz, 0.2Hz, 0.05Hz) could be linked to the following use-cases:
- 0.5Hz – strongest filtering, usually used for extended observations where the most important observation is, i.e. rhythm. It can also be used when the baseline drift occurs with 0.2Hz filter.
- 0.2Hz – general practice use
- 0.05Hz – weakest filtering – cardiology where every little detail matters (since it is the weakest filter it is also most susceptible to baseline drift)
Notching filter (mains filter)
Notching filter can be used for filtering mains interference without distorting the ECG signal. The filter should be enabled and set to local mains frequency: for example, 50Hz for Europe.
Myogram filter – muscle filter
The myogram filter filters muscle tremor – usually seen when the electrodes are placed on large muscle masses. You can see on the image below how the noise from muscles can be seen. Similarly, to Low-pass filter, the setting should be increased if the noise comes through. A recorded ECG is stored unfiltered. It is therefore possible to print the stored ECG either with or without passing the myogram filter.
MESI Signal enhancement
Since the ECG trace can drift a bit before it stabilizes, selecting the Progressive mode with either 0.2 or 0.5 High pass filter ensures faster and greater stability from the beginning of the measurement and provides good quality signal with all types of electrodes, including self-adhesive electrodes.
When the Progressive mode is enabled, the lead-off detection window will be shown prior to the measurement, letting you know which leads are connected and which are not. When all leads are successfully attached, the measurement will automatically continue.
The example of the filter settings that should be enabled for a clear and stable signal capture:
- Low-pass: 150Hz
- High-pass: 0.2Hz or 0.5Hz if baseline drift occurs
- Notching: 50Hz (if in e.g., EU)
- Myogram: 25Hz
- Signal enhancement: Progressive
If the problems persist make sure that:
- the electrodes aren’t placed directly on the large muscle masses,
- the skin was abraded prior to replacing the electrode,
- you check all electrode, lead wire and ECG cable connections,
- you check if the electrode gel dried out,
- you replace ECG cable and/or lead wires.
Read more about the relation of the modern digital electrocardiograph to its technology in the paper titled Recommendations for the Standardization and Interpretation of the Electrocardiogram here.
Individual features of ECG processing and recording are considered in terms of their clinical implications. Recommendations focus on progress toward optimal use of the ECG. It is hoped that the standards set out in this document will provide a further stimulus to the improvement of ECG recording and interpretation.