Gianni D'Addio

Assessment of cardiovascular regulation through irreversibility analysis of heart period variability: a 24 hours Holter study in healthy and chronic heart failure populations.

We propose an approach based on time reversibility analysis to characterize the cardiovascular regulation and its nonlinearities as derived from 24 hours Holter recordings of heart period variability in a healthy population (n=12, age: median=43 years, range=34–55 years) and in a pathological group of age-matched chronic heart failure (CHF) patients (n=13, primarily in NYHA class II, age: median=37 years, range=33–56 years, ejection fraction: median=25%, range=13–30%). Two indices capable of detecting nonlinear irreversible dynamics according to different strategies of phase-space reconstruction (i.e. a fixed two-dimensional phase-space reconstruction and an optimal selection of the embedding dimension, respectively) are tested and compared with a more traditional nonlinear index based on local nonlinear prediction. Results showed that nonlinear dynamics owing to time irreversibility at short time scales are significantly present during daytime in healthy subjects, more frequently present in the CHF population and less frequently during night-time in both groups, thus suggesting their link with a dominant sympathetic regulation and/or with a vagal withdrawal. On the contrary, nonlinear dynamics owing to time irreversibility at longer, dominant time scales were insignificantly present in both groups. During daytime in the healthy population, irreversibility was mostly due to the presence of asymmetric patterns characterized by bradycardic runs shorter than tachycardic ones. Nonlinear dynamics produced by mechanisms different from those inducing temporal irreversibility were significantly detectable in both groups and more frequently during night-time. The present study proposes a method to distinguish different types of nonlinearities and assess their contribution over different temporal scales. Results confirm the usefulness of this method even when applied in uncontrolled experimental conditions such as those during 24 hours Holter recordings.

An application of symbolic dynamics for FHRV assessment.

Fetal heart rate variability is surely one of the most important parameters to monitor fetal wellbeing. Linear studies, widely employed to study fetal heart variability and its correlations with the development of the autonomous nervous system, have shown some limitations in highlight dynamics potentially relevant. During the last decades, therefore, nonlinear analysis methods have gained a growing interest to analyze the chaotic nature of cardiac activity. Techniques investigating nonlinear dynamics have been already successfully employed in adults, to analyze different physiological and pathological states. Concerning fetal monitoring, instead, a smaller number of papers is available in the literature; even if symbolic dynamics was recently employed to quantify fetal heart rate regularity, demonstrating that the use of this technique may lead to a better and more differentiated understanding of normal fetal physiological development. In this work, we applied the symbolic dynamics to analyze fetal heart rate variability in healthy fetuses at the end of a physiological pregnancy. Our results confirmed the potentiality of the technique to highlight differences between signals characterized by more or less variability.

Telemedicine fetal phonocardiography surveillance: An Italian satisfactory experience

In this paper we describe an Italian experience of fetal home monitor, organized using a portable phonocardiography system (product by Pentavox, Hungary), and the method utilized to evaluate its effectiveness in providing quality services and patient satisfaction. Patient satisfaction is an important dimension in the evaluation of quality care delivery. We used phonocardiography technique in our experience of fetal home monitoring as it is non invasive and passive in nature, low-cost and easy to use. A lightweight portable phonocardiograph (Fetaphon-home) was assigned to six selected patients, without effective pregnancy risk to monitor fetal heartbeat, uterine contractions and fetal movements at home or wherever they need it. The selected patients were instructed by trained personnel in the use of the monitoring device. Patients were asked to perform the recording two times a week and to transmit 20-min signal to the reference centre. The home monitoring sessions were performed in addition to the routine surveillance at a gynecologists office; thus, the home monitoring did not replace clinic visits. The women were requested to fill a satisfaction questionnaire in order to evaluate their quality of life and anxiety state. Preliminary results have shown that home fetal surveillance appreciably reduces the need of travel for patients and consequently their stress. Furthermore, our results suggest that, after a short training, pregnant women are able to record and transmit long traces without troubles. Use of telemedicine system was generally well accepted by pregnant women since it increased the possibility of fetal long-term home surveillance which in turn could increase the efficiency of the service offered to them.

New posturographic assessment by means of novel e-textile and wireless socks device

The quantitative assessment of the postural stability is allowed by means of the use of pressure or force plates which are able to record a CoP subjects trajectory during a quite standing. However, the pressure or force plates are commonly used in a clinical environment, due to their very complexity and expensiveness. So their applicability outside laboratories is extremely limited. New e-textile and wireless wearable sensor technologies enable to extend the posturography in new low-cost and home assessment contexts. Twenty posturographic tests has been performed on normal subjects at the same time both by pressure signals derived by Sensoria fitness (SF) e-textile socks and by a gold standard stabilometric Zebris platform (ZP). Preliminary results showed a significant agreement between SF and ZP COP measurements, suggesting a clinical use of Sensoria for low cost home care based balance impairment assessments.

Effects of wavelets analysis on power spectral distributions in posturographic signal processing

The preservation of stability and body coordination in humans is assured by the correct working of the postural control system. Usually, postural oscillations is measured by the magnitude of center of pressure (CoP) movement over time. The conventional parameters in frequency domain to quantify changes of the CoP dynamics are estimated using Fourier spectral methods. However, considering the non-stationarity of the CoP signals, the Fourier approach, which breaks a time series signal into various sine wave frequency components, is not adapt. Aim of this work is to compare the wavelet decomposition analysis and the Fourier analysis, in measuring the power spectral distribution of the CoP traces, derived by Sensoria fitness (SF) e-textile socks, in three different frequency bands. Although wavelets analysis (WLT) has shown as a better technique than Fourier (FFT) in the resolution of the CoP oscillatory components, the overall spectral power modifications in their principal frequency bands have not yet been described. Particularly, the spectral power has been calculated in bands I (0.02-0.1 Hz), II (0.2-0.3), III (0.3-0.6), in percent values of the total spectral power.

A new tool for foetal phonocardiography simulation.

Among diagnostic techniques for foetal monitoring, phonocardiography is gaining more and more interest for its low cost, passive nature and capability to detect some cardiac diseases. In spite of these characteristics, its use in clinical routine is still limited due to different troubles; for example, signals recorded through maternal abdomen show generally a quite low signal-to-noise ratio, so that detection and analysis of foetal heart sounds result very difficult. In this scenario, the availability of artificial phonocardiographic signals, simulated with conditions resembling different foetal conditions, week of gestation and noise amount, to name someone, can be a very useful tool to train medical staff. In this paper a software for phonocardiography simulation, updated to take account also of the split is presented. The software is completed with a user interface which allow to modify in a simple way simulation parameters. It is worth highlighting that this software can be useful also for testing performances of other analysis software and mathematical tools for recognising of valves components in the heart sounds.