The scaling exponent, a quantitative descriptor of waveform structure, successfully distinguished early ventricular fibrillation (<4 minutes) from late ventricular fibrillation.
Does the scaling exponent of the ECG waveform distinguish between early and late ventricular fibrillation in a swine model?
The scaling exponent, a measure of fractal dimension, can characterize the time-dependent organization of ventricular fibrillation and distinguish early from late VF in a swine model.
Ventricular fibrillation (VF) is the most common arrhythmia causing sudden cardiac death. However, the likelihood of successful defibrillation declines with increasing duration of VF. Because the morphology of the electrocardiogram (ECG) waveform during VF also changes with time, this study examined a new measure that describes the VF waveform and distinguishes between early and late VF. Surface ECG recordings were digitized at 200 samples/s from nine swine with induced VF. A new measure called the scaling exponent was calculated by examining the power-law relationship between the summation of amplitudes of a 1,024-point (5.12 second) waveform segment and the time scale of measurement. The scaling exponent is a local estimate of the fractal dimension of the ECG waveform. A consistent power-law relationship was observed for measurement time scales of 0.005-0.040 seconds. Calculation of the scaling exponent produced similar results between subjects, and distinguished early VF ( or = 4-minute duration). The scaling exponent was dependent on the order of the data, supporting the hypothesis that the surface ECG during VF is a deterministic rather than a random signal. The waveform of VF results from the interaction of multiple fronts of depolarization within the heart, and may be described using the tools of nonlinear dynamics. As a quantitative descriptor of waveform structure, the scaling exponent characterizes the time dependent organization of VF.
Callaway et al. (Tue,) conducted a other in Ventricular fibrillation (n=9). Scaling exponent of ECG waveform was evaluated on Distinguishing early VF (< 4-minute duration) from late VF (≥ 4-minute duration). The scaling exponent, a quantitative descriptor of waveform structure, successfully distinguished early ventricular fibrillation (<4 minutes) from late ventricular fibrillation.