DFA on Heartbeat Fluctuation Dynamics in Animal Models and Humans: Alternans Lowers the Scaling Exponent

The aim of our study was to quantify the condition of the heart: sick or not in numerical order. "Alternans" is an arrhythmia exhibiting alternating amplitude/interval from beat to beat on the electrocardiogram and was first described in 1872 by Traube. Recently alternans was finally recognized as the harbinger of a cardiac disease, when an ischemic heart exhibited alternans. The pattern, alternans, arises spontaneously. As-yet-unidentified mechanisms must contribute. Probably it arises through a repeated application of a simple physical-mathematical role in a complex, nonlinearly connecting biological network, though we still do not know how. In animal models we detected alternans at various experimental conditions, including the heart with injury, the heart under emotional stress and the heart of a dying specimen. We have tested the detrended fluctuation analysis (DFA) on alternans and revealed that in both, animal models and humans, alternans rhythm lowers the scaling exponent that was computed by the DFA. We concluded that the scaling exponent can reflect a risk for the "failing" heart, especially when the low scaling exponent and alternans are concurrently present.