All these devices are fully computerized.
The 12-lead electrocardiogram is acquired synchronously, stored in computer
memory and then analyzed. Artefacts and noise are detected automatically
and reported. Wave identification (P-QRS-T) is automatic. The most important
ECG parameters are measured automatically for all 12 leads - wave amplitudes
and durations, P-Q, R-R and Q-T intervals, ST level, QRS and T frontal
plane axes, QT/RR ratio etc. The parameters measured are interpreted diagnostically
according to the Minnesota code. Signal traces and parameter/diagnostic
reports are printed onto thermosensitive paper using penless dot-matrix
high resolution printers. Long-lasting strips (up to 2 min) of one or two
channels can also be recorded and printed, for rhythm analysis purposes.
Other features include effective filtering of powerline and mains interference
using phaseless digital filters without distortions (patented method).
Orthogonal Frank leads can be computed from the standard 12 leads, thus
avoiding electrode relocation and use of back and "C" electrodes. Vectorcardiographic
loops in the three planes can be plotted and measured, for better P, QRS
and T-wave analysis. All devices can be linked to a PC using an isolated
serial interface (preserving the safety class). Additional features include:
flat membrane keyboard, different effective recording speed (12.5,
25 and 50 mm/s),tremor filter (30 Hz lowpass), etc.
All cardiographs comply with the
IEC 601/1 and TUV 750, and have effective defibrillation protection.
Over 5000 units of the above three
types of ECG machines were produced and sold in Bulgaria for the period
1985-1995. These devices are still the main electrocardiographs in Bulgarian
hospitals all over the country.
Related Publications:
Gramatikov, B. I. Isolated input
sections of multichannel ECG amplifiers. Second Youth Conference
on Biomedical Engineering with International Participation. Bulgaria, Varna,
Oct., 1985. (in Bulg.); In Abstracts: Abstr. No. 7, p 7.
Gramatikov, B. I. Microprocessor
Hardware of a three-channel digital storage electrocardiograph 1231.
(in Bulg.). Fourth National Conference on Biomedical Physics
and Engineering with International Participation, Sofia, Nov., 1984. In
Proceedings, pp. 52-54.
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