ANALYSIS OF BEAT-TO-BEAT VARIABILITY OF FREQUENCY CONTENTS IN THE ELECTROCARDIOGRAM USING 2-DIMENSIONAL FOURIER-TRANSFORMS

Late potentials are very small signals (1-20 mu V) in the surface ECG with high-frequency components, which are found in patients prone to s ustained ventricular tachycardia, Evaluation of these signals requires either very sophisticated recording techniques for single-beat analys is or signal averaging, Signal averaging, however, might disregard inf ormation about risk stratification. Therefore, me developed the Single -Beat Spectral Variance (SBSV) based on two-dimensional (2-D) Fourier transform of 80 ms segments of 128 consecutive beats, This approach de picts the beat-to-beat variability of the frequency contents of these ECG segments. An index function enables an objective detection of late potentials, We investigated 35 patients after myocardial infarction a nd sustained ventricular tachycardia (Group 1), 50 patients after myoc ardial infarction without ventricular arrhythmias (Group 2) and ten he althy volunteers, SBSV classified 29 of 35 patients (83%) of Group 1 a s pathologic, 14 of these 29 patients (48%) exclusively on the basis o f marked Wenckebach-like conduction pattern, In Group 2, only five of 50 patients showed abnormal SBSV, In Group 3, we found no pathologic r esult, Thus, SBSV is a promising new method to investigate late potent ials in patients after myocardial infarction, SBSV contains not only t he results of frequency analysis after signal averaging, but also eval uates variable ECG components.