The project was aimed at facilitating examinations of patients with previous Myocardial Infarctions (MI) with the aim of stratifying risk of developing life-threatening ventricular tachycardia (VT) due to increased likelihood of reentry. The HIS-potential detection software was enabled the follow-up of patients at risk of developing AV block [5].

Dr. Gramatikov developed a front-end module, hardware and software for detection of His- and Late potentials in the high resolution signal-averaged ECG. Specialized software was written in Forth programming language. Program functions like data logging, filetring, analysis, archival and printing, are called from a main menu, which also contains a help for each item. The software also facilitates interactive mode of analysis, in which the operator can select time points, treshold values etc. by using graphical traces and cursors.

The system is able to record and calculate the high-resolution signal averaged XYZ vector magnitude. This signal is beieved to give a generalized idea of the late stage of the depolarization process of the myocardium. If the so called "late potentials" (fractionation of the depolarization front due to the existence of tissue with altered propagation properties) are present, the XYZ vector magnitude decays more slowly during the late QRS complex. Our computer system displays the high resolution ECG of a normal patient and a patient with late potentials (hard copy of the computer screen). Along with other helpful information, the three standard parameters for time-domain analysis are displayed: 1) QRS duration;  2) V40(=RMS40=the root mean square voltage of the terminal 40 ms of the QRS complex in microvolts);   and    3) LAS (the duration in ms of the low amplitude signal after sinking below 40 microvolts and before QRS offset). The QRS ends abruptly with a normal subject, and is decaying slowly in patients who are prone to VT.  The system was tested on 30 post MI-patients, 4 of them with VT, and delivered very good results [7].

In addition, Boris developed improved methods for combined measurements and analysis in the time- and frequency domain simultaneously [3]. Within this project, Dr. Gramatikov also examined the effect of different types of digital filters [4,6]. The potential of time-frequency distributions obtained by means of the Wavelet transform to identify late potentials was also examined [1,2].

Dr. Gramatikov was responsible for the clinical probation of the front-end module and software.

Related Publications:

[1] Gramatikov, B., Georgiev, I.   Wavelets as an Alternative to STFT in signal-averaged electrocardiography.    Medical and Biological Engineering and Computing, Vol.33, No.3, May 1995, pp. 482-487.

[2] Nikolov, Z., Georgiev, I., Gramatikov, B., Daskalov, I.   Use of the Wavelet Transform for Time-Frequency Localization of Late Potentials.  Biomedizinische Technik, Suppl.38 (1993), pp. 87-89.

[3] Gramatikov, B.   Detection of late potentials in the signal-averaged ECG - combining time and frequency domain analysis.   Medical and Biological Engineering and Computing, Vol.31, No.4, July 1993, pp.333-339.

[4] Gramatikov, B.    Digital filters for the detection of late potentials.   Medical and Biological Engineering and Computing, Vol.31, No.4, July 1993, pp.416-420.

[5] Gramatikov, B.   Non-invasive recording of His-bundle activity by means of high-resolution signal-averaged electrocardiography.   Sixth National Conference on biomedical Physics and Engineering with international Participation. Sofia, 22-24 October 1992., (in English), In Proceedings, pp.3-8.

[6] Gramatikov, B.   Comparison of some linear phase FIR-filters for real-time ECG processing.   Sixth National Conference on biomedical Physics and Engineering with international Participation. Sofia, 22-24 October 1992 (in Engl.)   In Proceedings - pp.27-31.

[7] Shachov, B., Gramatikov, B., Petkov, A., Dimitrov, E.    Late potentials in patients with ventricular tachychardia - initial successful clinical experience with the new technology of CLEMA.   Fourth National Congress in Cardiology. Plovdiv, Bulgaria, June 4-5, 1992. In Abstracts - p.28, Abstract 62. ( in Bulg.).

[8] Gramatikov, B.   Methods of generating and testing of digital filters for biological signals (Bulg.)   Fourth national scientific session Automation in biotechnological processes and biomedical research, Sofia, 17-19 Sept. 1991; in Proceedings, pp. 210-217.