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Complexity of Heart Rate Variability
ComplexHRV
- data analysis and modeling
Complex rhythmic processes are typical for living organisms. The human cardiovascular
system is a paradigmatic source of the fundamental physiological rhythm - the heart rate, and
is controlled by several neural and hormonal mechanisms. Blood pressure and
electrocardiogram (ECG) are the easiest measures of signals originating in the cardiovascular
system. The continuous ECG can be transformed into a discrete signal of normal beat-to-beat
cardiac periods, called NN-intervals. It has been demonstrated that NN-intervals fluctuate in a
complex manner: they show the long-range temporal autocorrelations, multifractal scaling
properties, and share characteristics of a physical system in a critical state.
The variation in NN series is termed the heart rate variability (HRV). The HRV represents the
most promising marker in recognition of the relationship between the autonomic nervous
system and cardiovascular mortality. The heart rate is raised by slow acting sympathetic
activity and decreased by fast acting parasympathetic (vagal) activity. The balance between
the effects of the sympathetic and parasympathetic nervous systems is believed to be reflected
in the beat-to-beat changes of the fundamental cardiac cycle.
The ECG is the most commonly prescribed examination by physicians for their patients. The
24-hour ECG Holter monitoring provides information on electrical activity of a heart during a
long time. Therefore there is a vast amount of data and research on HRV is conducted in
many scientific centers. This strong interest resulted in implementing the methods to
medical routine. In 1996 results were collected in a paper published in European Heart
Journal 17 ( in pages 354-381): Heart rate variability. Standards of measurement,
physiological interpretation, and clinical use, prepared as Task Force of The European
Society of Cardiology and The North American Society of Pacing and Elecrophysiology.
However, two types of technical difficulties make the analysis of HRV not as reliable as it
could be. The first type of difficulties arises from the size of the data sets. These sets are huge,
hence dealing with them requires high skills in computer science. The second difficulty is
related to the lack of stationary features in a single series what strongly misleads standard
tools. Careful pre-analysis of statistical properties of each series is necessary.
Multifractal formalism is a proposition to determine statistical features of series by its
scaling properties. Scaling properties related to the long-range memory allow to estimate
interdependences in the system while singularity statistics provides insights into short-term
relations. Many types of real signals are investigated by multifractal analysis such as fully
developed turbulence, financial time series, load of network traffic and physiological signals.
A key issue in the classification and modeling of empirical data as well as in the analysis of
the physical mechanism producing scaling phenomena is the accurate measure of scaling
exponents. Existing methods are far from working as a black box. Therefore there is a
pressing need both to standardize existing estimators and to design new ones.
Description of partners :
UNIVERSITY OF GDAŃSK (Poland)
Institute of Theoretical Physics and Astrophysics (ITP&A).
The research group in complex systems will be coordinated by: Dr hab Danuta Makowiec,
prof UG (vice Dean of Faculty of Mathematics, Physics and computer Science). The
research group in complex systems consists of dr hab Wieslaw Miklaszewski (ITP&A – vice
Director), dr Piotr Gnaciński (ITP&A), dr Marceli Krogulec (ITP&A), mgr Aleksandra
Dudkowska ( PhD student) and mgr Michal Posiewnik (ITP&A).
The group has successfully cooperated with cardiologists coordinated by Prof. dr hab.
Andrzej Rynkiewicz from 1st Department of Cardiology of Medical Academy of Gdańsk for
last two years. So far by multifractal analysis of signals collected from carefully selected
groups of patients we could separate heart rates of healthy people from heart rates of people
diagnosed with reduced left ventricular systolic function. We also proposed new indicators
(related to fractal statistics) of HRV. Our results on HRV were published in following papers:
(1) A. Dudkowska , D. Makowiec, Physica A 336 (2004) 174-180: Sleep and wake phase of
hart beat dynamics by artficial insymmetrised patterns
(2) A. Dudkowska, D. Makowiec, Folia Cardiologica 12, suppl. D, (2005): Modeling of the
human cardiorespiratory system — the influence of the stochastic input
(3) A. Dudkowska, R.Gałąska, J. Wdowczyk-Szulc, A. Koprowski, D. Makowiec, A.
Rynkiewicz, Folia Cardiologica 12, suppl. D, (2005): Heart rate variability analysis by
artificial insymmetrised pattern
(4) D. Makowiec, R. Gałąska, A. Dudkowska, A. Rynkiewicz, M. Zwierz, Physica A 369,
632-644 (2006) : Long-range dependencies in heart rate signals - revisited,
(5) D. Makowiec, A. Dudkowska, M. Zwierz, R. Gałąska, A. Rynkiewicz, Acta Phys.Pol B
37 1627-1639 (2006): Scale invariant properties in heart rate signals
and presented both to the medical audience by R. Gałąska (MAG) on World Congress in
Cardiology in Barcelona, September 2006, and to physicists' audience by D.Makowiec (UG)
during Symposium on Marian Smoluchowski Symposium on Statistical Physics, Zakopane
2005. There are two doctoral thesis being prepared ( R.Galąska, A.Dudkowska) which
closely relate to the project subject.
MEDICAL UNIVERSITY OF GDANSK (Poland)
The research group in cardiology will be coordinated by: Professor Andrzej Rynkiewicz
List of participants:
Prof. Andrzej Rynkiewicz, MD, PhD head of the department
Joanna Wdowczyk-Szulc, MD - assistant, non-invasive cardiology, Holter monitoring
Monika Stołychwo, MD- PhD student, non-invasive cardiology
Krystyna Żelechowska, MD, PhD- non-invasive cardiology
Marcin Gruchała, MD, PhD- assistant, invasive and noninvasive cardiology
Rafał Dworakowski, MD- assistant, invasive and non-invasive cardiology, intensive care
Wojciech Sobiczewski, MD, PhD- assistant, invasive and non-invasive cardiology
Andrzej Koprowski, MD, PhD- assistant, non-invasive cardiology, echocardiography
Marcin Fijałkowski, MD- PhD student, non-invasive cardiology, echocardiography
Bartosz Curyłło, MD- PhD student, non-invasive cardiology
Rafał Gałaska, MD- assistant, invasive and non-invasive cardiology, Holter monitoring
Krzysztof Chlebus, MD- assistant, invasive and non-invasive cardiology
UNIVERSITY OF OULU (Finland)
Department of Electrical and Information Engineering
The Biosignal processing research group is coordinated by Prof. Tapio Seppanen and has an
extensive experience in signal processing and pattern recognition methods and applications.
The most important application area is the ECG signal analysis and classification. Important
topics are heart rate variability research and T-wave morphology classification.
Ospedale S. Camillo, Dipartimento di cardiologia (Italy)
S. Camillo is the largest hospital in Rome; the Department of cardiology will participate to the
present project to provide the consortium with the great experience in cardiology for the
definition of the requirements of the technology and to execute field tests on the prototype and
final assessment activities.
ACTA SERVICE – (Italy)
ACTA Service was born in December 1988 by a group of technicians coming up from various
experiences in other companies of the biomedical sector. The specific competencies of the
people engaged are several by the meaning of offering devices related to instruments in the
laboratory, in particular meaning for hi-tech aspects and related problems to be solved. After
more than 15 years ACTA Service developed its own method in projecting and producing
computerised instruments for biomedical instruments.
There are six lines of products and a large variety of customised possibilities. This customer’s
care allows ACTA SERVICE to cover a large part of need of small and medium laboratories
in Italy.
ESA S.C. (Poland)
ESA S.C. was founded in 1993 in Katowice. The team consists of IT professionals with
extensive scientific background in Computer Science and a long-term professional experience
in the most demanding areas of IT technology market.
Industrial Innovation Design SA (I2M - Spain)
I2M is a start-up company created in February 2002 and for this reason its own track of
records is limited. On the other hand, I2M is a joint venture between 3 partners who worked
in collaboration during the last 10 years on development of microtechnology for biomedical
applications.
T-Connect (Italy)
T-Connect, established in Italy, by May 2002, is constituted by experienced professionals in
the field of wireless communication applications and INNOVA Italian leader in launching and
financing of European and International R&D projects.
T-Connect is set up in AREA Science Park, in Trieste, one of the leading multi-sectorial
Science Parks in Europe (http://www.area.trieste.it/).
The location enjoys one of the highest concentrations of IT and Telecommunication Research
competencies in Italy and is the ideal working environment for R&D activities also because of
the local incentives and availability of highly qualified personnel.
DUNVEGAN Ltd (UK)
Dunvegan is involved in the design and manufacture of telecommunications and industrial
electronic systems. The Company can offer a full service from assistance with initial system
specification through to volume production.
In addition, Dunvegan has expertise in bringing new products to market with efficient
marketing, sales and product distribution divisions. Dunvegan's hardware expertise
encompasses both analogue and digital electronics and includes low noise audio design, low
power consumption techniques, microprocessor, microcontroller, Digital Signal Processing
(DSP) and programmable logic and ASIC based technologies.
AGT (Italy)
AGT is an engineering company active in the design of innovative electrical and energy
systems, technology transfer and application of advanced and innovative material and
mechanical technologies, sourced worldwide, purposely designed and integrated according tot
users’ requirements, and introduced into the Italian and European advanced industrial,
aerospace and transportation markets.
LABOR (Italy)
LABOR is an industrial research laboratory set up with the support of a group of university
professors from the Department of Industrial Chemistry and Department of Applied
Mechanics of the Faculty of Engineering of the University La Sapienza of Rome.
Company's mission is to carry out R&D activities and projects in close co-operation with
industry and public research bodies, establishing with them long term research and
cooperation agreements, for the access to research structures and the employment of research
personnel.
Experimental design is a very powerful and comprehensive methodology, allowing to plan
and carry out experiments in such a way that maximum possible information is gained. It is
very useful in the investigation of several aspects in the course of knowledge acquisition from
experimental data like:
 Determination of the absolute importance that variables have in generating responses in
complex systems
 Identification and elimination of irrelevant variables
 Creation of simple mathematical models for experimental optimisation
 Reduction of costs of experiments
 Enhancements of quality of products and processes
 Abatement of noise effects
ED is of paramount importance in application fields where financial considerations are
crucial: it provides an effective shortcut to obtaining knowledge, assuring product quality
robustness and product performance.
The Project Manager in charge of the project co-ordination will be Mr. Alfredo PICANO
IAITI (Portugal)
The Institute AGILUS for Innovation in Information Technologies (IAITI) is a research
centre established in the North of Portugal by initiative of a group of companies and research
organizations with the mission to bridge the gap between academic research institutions and
industrial fabric in the field of Information and Communication Research. IAITI is therefore
specifically oriented for applied research and development projects in association with
industrial users, and was created based upon the experience of the organization AGILUS,
Lda, created in 1995 by a group of researchers. IAITI has specific competences and expertise
in the following areas:
- Development of Executive Information Systems (EIS) / Decision Support Systems
(DSS);
- Development of Knowledge and Document Management Systems and Workflow.
-Implementation and management of Information Technology projects ;
- Information Systems auditing and diagnosis;