[A computerized system for the detection of fragmentations in depolarization. I]

It was developed a computer system which allows the amplification, digitalization, signal averaging and analysis of the: time domain, first derivative and fast Fourier transform of the ECG signal. Through this methods it was possible to detect late-potentials that arise from morphologically altered myocardium with abnormalities in the conduction velocity. To validate the system 28 studies were done in 15 normal subjects (Group 1), ten in patients with recent or old myocardial infarction (Group 2), and 3 studies in patients with myocardial infarction and sustained ventricular tachycardia during the coronary care unit stay or documented by ambulatory electrocardiogram (Group 3). Of the 31 variables documented of the time domain, first derivative and frequency domain, the RMS voltage of the last 40 msegs. of the filtered QRS al 25 Hz., the crossings through the base line of the first derivative in lead Y and the RMS voltage of the last 40 msegs. with the fast Fourier Transform analysis, from 3.9 to 304.7 Hz., allowed the identification of patients in group 3 from group 1 (p less than 0.0001). By the other hand, the RMS voltage of the first derivative in lead Y, the peak to peak amplitude of the first derivative in lead Z and the RMS voltage of the first derivative in lead Z differentiate group 3 from group 2 (p less than 0.002). It is concluded that the first derivative, the frequency domain and the time domain, in this sequence, are useful in the identification of late potentials in the terminal portions of the filtered QRS.