HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 542/2/619    most recent 2001.013389v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Francis, D. P. Articles by Piepoli, M. Search for Related Content PubMed PubMed Citation Articles by Francis, D. P. Articles by Piepoli, M.

Physiological basis of fractal complexity properties of heart rate variability in man

Darrel P. Francis *†, Keith Willson †, Panagiota Georgiadou *, Roland Wensel †, L. Ceri Davies *†, Andrew Coats *† and Massimo Piepoli *†

The diagnostic and prognostic power of the fractal complexity measure '' of detrended fluctuation analysis (DFA) has remained mysterious because there has been no explanation of its meaning, particularly in relation to spectral analysis. First, we present a mathematical analysis of the meaning of , in weighted power-spectral terms. Second, we test this hypothesis and observe correlations between DFA-based and weighted spectral methods of 0.97 (P < 0.0001) for ₁ and 0.98 (P < 0.0001) for ₂. Third, we predict mathematically that even in conventional (unweighted) spectral analysis there should be approximate counterparts to DFA, namely that ₁ and ₂ behave broadly in proportion to the conventional (unweighted) ratios LF/(HF + LF) and VLF/(LF + VLF), respectively, where HF is high frequency, LF is low frequency and VLF is very low frequency. Fourth, we test this hypothesis by physiologically manipulating spectral ratios in healthy volunteers in two ways. The effect of 0.1 Hz controlled breathing on LF/(HF + LF) correlates markedly with the effect on ₁ (r = 0.73, P = 0.01); the effect on VLF/(LF + VLF) correlates markedly with that on ₂ (r = 0.76, P < 0.01). Likewise, with voluntary periodic breathing the reduction in ₂ correlates strongly with that in VLF/(LF + VLF) (r = 0.88, P < 0.001); effects on ₁ and LF/(HF + LF) again clearly correlate (r = 0.73, P = 0.01). Finally, we examine published literature to identify previously undiscussed evidence of the relationship between ₁ and LF/(HF + LF). We conclude that the ₁ and ₂ indices are simply frequency-weighted versions of the spectral ratios LF/(HF + LF) and VLF/(LF + VLF), respectively, multiplied by two (giving a range of 0-2). We can now understand fractal manifestations of physiological abnormalities: depressed baroreflex sensitivity low LF/HF low LF/(HF + LF) low ₁, while periodic breathing high VLF/LF high VLF/(LF + VLF) high ₂. Prognostic associations of are no longer mysterious.