Slow conduction within infarct scars as a source of high-frequency oscillations in the QRS signal

We propose a detailed explanation of increased variability of high-frequency (> 100 Hz) components within the QRS observed in post-myocardial infarction patients, reported in recent studies of real high-resolution ECGs. Using mathematical models of single, branching and tortuous cardiac strands, based on cellular experimental data, we simulated effects of conduction slowing, characteristic for regions bordering infarcts, on spectral properties of the depolarization signal, assessed by means of wavelet transform and wavelet variance. Calculated extracellular potentials contained oscillations with frequencies related to propagation velocity and cellular dimensions by simple mathematical formulas. We conclude that slow AP propagation at 3-20 cm/s within infarct scars is a possible source of high-frequency (100-300 Hz) micropotentials and, with unstable activation wavefront and/or trigger jitter contributes to the increased beat-to-beat variability in the QRS.