Nonlinear Methods of Cardiovascular Physics and Their Clinical Applicability

Abstract

In this tutorial we present recently developed nonlinear methods of cardiovascular physics and show their potentials to clinically relevant problems in cardiology. The first part describes methods of cardiovascular physics, especially data analysis and modeling of noninvasively measured biosignals, with the aim to improve clinical diagnostics and to improve the understanding of cardiovascular regulation. Applications of nonlinear data analysis and modeling tools are various and outlined in the second part of this tutorial: monitoring-, diagnosis-, course and mortality prognoses as well as early detection of heart diseases. We show, that these data analyses and modeling methods lead to significant improvements in different medical fields.Keywords: Cardiovascular physics; nonlinear data analysis and modeling; heart rate and blood pressure variability; baroreflex sensitivity. List of Abbreviations

Short-term couplings of the cardiovascular system in pregnant women suffering from pre-eclampsia

“…saturations and threshold effects or hysteresis. Because such transformations are usually unknown, in this study a coupling analysis based on a non-parametric model is used, which follows the idea of Granger causality (Granger 1969;Wessel et al 2007;Riedl et al 2009). …”

Quantification of heart beat nonstationarities by nonparametric segmentation

“…The series of time intervals between consecutive heart beats, the beatto-beat intervals, are extracted from the electrocardiograms. All resultant signals were filtered in order to avoid ectopic beats [7]. After that these time series are segmented as follows: given a segment of a time series, a sliding pointer is moved in order to compare the two fragments, on the left (L) and the right (R) side of the pointer i.…”

Tachycardia as "Shadow Play"

“…For example, some of the recent developments are described in (Loskutov & Mironyuk, 2007;Wessel et al, 2007). In general, there is an apparent tendency for science to become more and more mathematical.…”

“…"Similar changes in form of the QT interval and T waveform can be induced by very different molecular and cellular effects, some benign, others dangerous." Other authors (Wessel et al, 2007) state very decidedly: "There exists no 'golden parameter' whose measurement is able to reliably describe and estimate all risks. From time to time there is an excessive enthusiasm of some scientists claiming that their new developed parameter is better than previously used ones.…”

“…<…> Considering these rather system-theoretical characteristics, the development of nonlinear and also knowledge-based methods should lead to a diagnostic improvement in risk stratification. <…> A further aim, therefore, is, to go a qualitatively new step: the combination of data analysis and modeling" (Wessel et al, 2007). A cardiologist will be likely to gain the adequate diagnostic capacity of distinguishing the normal action of the heart from pathological one only, when having such a skilful knowledge-based model, realized either in computer or in the cardiologist's brain.…”