Analysis of beat-to-beat variability of frequency contents in the electrocardiogram using two-dimensional Fourier transforms

Abstract

Late potentials are very small signals (1-20 microV) in the surface ECG with high-frequency components, which are found in patients prone to sustained ventricular tachycardia. Evaluation of these signals requires either very sophisticated recording techniques for single-beat analysis or signal averaging. Signal averaging, however, might disregard information about risk stratification. Therefore, we 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 depicts 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 and sustained ventricular tachycardia (Group 1), 50 patients after myocardial infarction without ventricular arrhythmias (Group 2) and ten healthy volunteers. SBSV classified 29 of 35 patients (83%) of Group 1 as pathologic, 14 of these 29 patients (48%) exclusively on the basis of marked Wenckebach-like conduction pattern. In Group 2, only five of 50 patients showed abnormal SBSV. In Group 3, we found no pathologic result. Thus, SBSV is a promising new method to investigate late potentials in patients after myocardial infarction. SBSV contains not only the results of frequency analysis after signal averaging, but also evaluates variable ECG components.

Quantitative evaluation of a wavelet-based method in ventricular late potential detection

“…After generating three basic VLP waveforms for each basic HRECG record, each of them was added to the QRS complex end part of every heartbeat [1,20] of its corresponding lead (X, Y , or Z). The position of the additive VLPs waveforms is varied randomly from beat-to-beat, and this simulates the VLP variability due to the physiological causes [1,18,21]. The position of the additive VLP waveforms for each basic HRECG record was determined as follows [1,6]:…”

Image and Signal Processing

“…The lastpaperpertains to the "analysis of beat-to-beat frequency variability of ECGs using 2-D fourier transforms" [4]. There are considerable difficulties in detecting very faint, fragmented, and delayed high frequency ECG signal components (late potentials) in patients with sustained ventricular tachychardia.…”

“…There are considerable difficulties in detecting very faint, fragmented, and delayed high frequency ECG signal components (late potentials) in patients with sustained ventricular tachychardia. The authors [ 4] have developed an analytical approach called Single-Beat Spectral Variance (SBSV) to characterize the beat-tobeat variability of the frequency components of these ECG segments, while taking advantage of signal averaging to improve the signal-to-noise ratio (SNR) of the measurements. The technique is based on two-dimensional Fourier transforms of 80 ms segments (the first dimension) of 128 consecutive beats each (the second dimension) at the end of the QRS-complex, with the J-point defmed as the peak of the autocorrelation function of the spatial velocity.…”