Development of a Holter ECG

OData support
Supervisor:
Dr. Jobbágy Ákos Andor
Department of Measurement and Information Systems

The commonly used ECG recordings usually contain less than one minute of data. However, in most cases cardiac disorders are episodic. This is why 24-hour ECG recordings are needed to be made by a so called Holter ECG recorder. The device influences the daily routine only slightly, this way makes it possible to gather realistic data of the electric activity of the heart in different physiological statuses.

The devices available on the market are usually AC coupled. This attribute implies the slow settling of the signal and the distortion of the low frequency components of the signal, particularly the P and T waves. In the first part of the thesis, the introduction of a Holter ECG instrument that I designed will take place. The instrument is capable of recording the ECG data using one or two channels. The relatively high, 24 bit resolution data registration of the instrument allows for the elimination of the analog highpass filtering of the incoming signal, this way DC coupling is used. The instrument is capable of detecting of the falling off of the electrodes. In this case the instrument warns with sound signal. The device records the ECG signal without preprocessing and compresses it without loss. The records are read by a PC program. The instrument is rechargeable through the USB port of the PC.

In the second part of the thesis, the description of the automatic processing of the recorded signals takes place. The algorithm that I constructed detects the most important characteristic points of the waves of the ECG. After the throwaway of the misdetected ECG segments, the results are used for the calculation of clinically useful diagnostic parameters: heart rate, QT interval, R and T amplitudes. After that, a number describing the self-similarity of the ECG cycles and it's variation through the recording takes place. The construction of a mean ECG cycle from the records is shown, that can serve as a basis for comparing the records of a person acquired at different times.

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