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S Cerutti

Publications and source records attributed to S Cerutti.

At least 19 recordsLinked to original sources
PubMed2000

Evaluation of respiratory influences on left ventricular function parameters extracted from echocardiographic acoustic quantification.

This study was designed to assess, using the echocardiographic acoustic quantification technique, the influence of respiration on left ventricular (LV) function and its modifications connected with the ageing process, quantifying in a non-invasive way the respiratory contribution to the LV volume variability. An automated algorithm is applied to extract the beat-to-beat measurements of LV function parameters from the LV volume signal, obtained from recordings lasting a few minutes. Mean values, amount of variability and spectral content were studied in a population of 17 normal young (mean age 25 +/- 1 years) and 12 normal old (mean age 64 +/- 2 years) subjects. Mean values of the beat-to-beat measurements of LV function parameters were able to point out alterations connected with the ageing process in peak filling rate, peak atrial filling rate and peak ejection rate. Spectral analysis, applied to the extracted variability series, displayed a predominance of the high-frequency (HF) component corresponding to respiration in all LV function parameters; moreover, age related changes of HF variability were observed in peak ejection rate. The HF power spectrum component of beat to beat series extracted from the LV signal can provide a non-invasive assessment of the fluctuations in ventricular parameters associated with respiration.

Adult↗
PubMed2000

Recurrent patterns of atrial depolarization during atrial fibrillation assessed by recurrence plot quantification.

The aim of this study was to determine the presence of organization of atrial activation processes during atrial fibrillation (AF) by assessing whether the activation sequences are wholly random or are governed by deterministic mechanisms. We performed both linear and nonlinear analyses based on the cross correlation function (CCF) and recurrence plot quantification (RPQ), respectively. Recurrence plots were quantified by three variables: percent recurrence (PR), percent determinism (PD), and entropy of recurrences (ER). We recorded bipolar intra-atrial electrograms in two atrial sites during chronic AF in 19 informed subjects, following two protocols. In one, both recording sites were in the right atrium; in the other protocol, one site was in the right atrium, the other one in the left atrium. We extracted 19 episodes of type I AF (Wells' classification). RPQ detected transient recurrent patterns in all the episodes, while CCF was significant only in ten episodes. Surrogate data analysis, based on a cross-phase randomization procedure, decreased PR, PD, and ER values. The detection of spatiotemporal recurrent patterns together with the surrogate data results indicate that during AF a certain degree of local organization exists, likely caused by deterministic mechanisms of activation.

Adult↗
PubMed1999

Conditional entropy approach for the evaluation of the coupling strength.

A method that enables measurement of the degree of coupling between two signals is presented. The method is based on the definition of an uncoupling function calculating, by means of entropy rates, the minimum amount of independent information (i.e. the information carried by one signal which cannot be derived from the other). An estimator of the uncoupling function able to deal with short segments of data (a few hundred samples) is proposed, thus enabling the method to be used for usual experimental recordings. A synchronisation index is derived from the estimate of the uncoupling function by means of a minimisation procedure. It quantifies the maximum amount of information exchanged between the two signals. Simulations in which non-linear coordination schemes are produced and changes in the coupling strength are artificially induced are used to check the ability of the proposed index to measure the degree of synchronisation between signals. The synchronisation analysis is utilised to measure the coupling strength between the beat-to-beat variability of the sympathetic discharge and ventilation in decerebrate artificially ventilated cats and the degree of synchronisation between the beat-to-beat variability of the heart period and ventricular repolarisation interval in normal subjects and myocardial infarction patients. The sympathetic discharge and ventilation are strongly coupled and the coupling strength is not affected by manoeuvres capable of increasing or depressing sympathetic activity. The synchronisation is lost after spinalisation. The synchronisation analysis confirms that the heart period and ventricular repolarisation interval are well coordinated. In normal subjects, the synchronisation index is not modified by experimental conditions inducing changes in the sympathovagal balance. On the contrary, it strongly decreases after myocardial infarction, thus detecting and measuring the uncoupling between the heart period and ventricular repolarisation interval.

Animals↗
PubMed1999

Differential patterns of bone turnover in relation to bone pain and disease extent in bone in cancer patients with skeletal metastases.

BACKGROUND: The alteration of the bone microenvironment as a consequence of skeletal metastases is poorly understood. The aim of this study was to search for patterns of bone markers in relation to primary tumor type, bone pain, and number of sites involved in patients with bone metastases. METHODS: We studied 323 patients with bone metastases from various primary malignancies. We sequentially measured the serum concentrations of bone alkaline phosphatase [by an electrophoretic technique (BALP)], carboxy-terminal telopeptide of type I collagen (ICTP), calcium (CaS), intact parathyroid hormone (PTH), and the fasting urinary excretion of calcium (Ca:Cr). Immunoradiometric serum bone alkaline phosphatase (I-BALP) and urinary excretion of deoxypyridinoline (DPYD) were also assessed in the 175 cases. Data were analyzed as a function of bone pain (assessed by a validated pain questionnaire), the number of radiographically confirmed sites of bone involvement, and the most frequent primary tumor types: breast cancer (BC; 124 patients), prostate cancer (PC; 90 patients), and non-small cell lung cancer (LC; 49 patients). RESULTS: Serum BALP and I-BALP correlated with the number of radiologically identified blastic bone lesions. BALP and I-BALP were more frequently increased in PC (72% for both measurements) than in BC (50% and 60%, respectively) or LC (3% and 5%, respectively; P <0.001 for BALP and P = 0.001 for I-BALP). ICTP and DPYD values did not differ among PC, BC, and LC, but they did show a direct relationship with the disease extent in bone (P <0. 001). CaS and Ca:Cr did not vary significantly according to the bone tumor burden. Bone pain directly correlated with ICTP (P <0.001), DPYD (P = 0.002), CaS (P <0.002), and Ca:Cr (P = 0.001), whereas the relationship was inverse for serum PTH (P = 0.002). When patients were stratified according to the primary tumor, ICTP correlated with the bone pain in all subsets (P <0.005, <0.005, and <0.001 for BC, PC, and LC, respectively), as did CaS and Ca:Cr in LC patients (P = 0.01 and 0.02, respectively) but not in PC and BC patients. CONCLUSIONS: The patterns of bone turnover markers differ among the primary tumor types. Both resorption and formation markers reflect the number of radiographically identified sites of bone metastases, whereas resorption markers and serum calcium but not formation markers correlate with bone pain.

Adult↗
PubMed1999

Autonomic function and baroreflex sensitivity during a normal ovulatory cycle in humans.

OBJECTIVE AND DESIGN: Possible variations occurring in the autonomic function during a normal ovulatory cycle have been poorly investigated and it is not known whether the baroreflex sensitivity may change according to the different phases of the cycle. The aim of this study was to evaluate heart rate variability (power spectrum analysis), and baroreceptor sensitivity (alpha-low frequency coefficient) in 13 young women with regular menses during the two phases of the cycle (phase I: 5 +/- 1 days and phase II: 23 +/- 3 days from bleeding). RESULTS: The low frequency/high frequency ratio was significantly higher in the second phase of the cycle (phase I: 2.8 +/- 2.6; phase II: 5.6 +/- 5.8, p < 0.05), in the presence of increased low frequency and reduced high frequency expressed in normalized units-nu-(phase I: 59.8 +/- 16.7 nu and 32.6 +/- 15.6 nu for low frequency and high frequency, respectively; phase II: 67.7 +/- 18 nu and 25.7 +/- 17.5 nu for low frequency and high frequency, respectively; p < 0.05). The alpha-low frequency coefficient, index of baroreflex sensitivity, did not statistically differ in the two phases (phase I: 10.6 +/- 4.5 msec/mm Hg; phase II: 8.9 +/- 4.9 msec/mm Hg; ns). CONCLUSIONS: The power spectrum analysis suggests that the autonomic function may be affected by the ovulatory cycle, sympathetic activation being relatively increased in the second phase. On the contrary, the baroreceptor function seems to be scarcely influenced by the two phases of the menstrual cycle.

Adult↗
PubMed1998

Cardiac autonomic patterns preceding occasional vasovagal reactions in healthy humans.

BACKGROUND: The wide range of clinical presentation of orthostatic vasovagal syncope suggests different underlying changes in the cardiac autonomic modulation. METHODS AND RESULTS: To evaluate the beat-by-beat modifications in the neural control of heart period preceding a syncopal event, we studied RR interval variability in 22 healthy subjects who experienced fainting for the first time during a 90 degrees head-up tilt and in 22 control subjects by means of time-variant power spectral analysis. Sympathetic and vagal modulations to the sinoatrial node were assessed by the normalized power of the low-frequency (LF, approximately 0.1-Hz) and high-frequency (HF, approximately 0.25-Hz) oscillatory components of RR variability. When the patients were supine, no differences were observed in the hemodynamic and spectral parameters of the 2 groups. During the tilt procedure, RR, LFNU, and HFNU (NU=normalized units) values were relatively stable in control subjects. During early tilt (T1), subjects with syncope had reduced RR intervals compared with control subjects. In 13 subjects with syncope, RR decreased while LFNU and LF/HF increased in the last minute of tilt before syncope (T2). Conversely, in the remaining 9 fainters, LFNU and LF/HF decreased from T1 to T2 and HFNU increased slightly. CONCLUSIONS: Two different patterns may be recognized in the cardiac autonomic changes preceding an occasional vasovagal event, namely, one characterized by a progressive increase of the marker of cardiac sympathetic modulation up to the onset of syncope, the other by a sympathetic inhibition with an impending vagal predominance. The recognition of different pathophysiological mechanisms in fainters may have important therapeutic implications.

Adolescent↗
PubMed1998

Quantifying electrocardiogram RT-RR variability interactions.

A dynamic linear parametric model is designed to quantify the dependence of ventricular repolarisation duration variability on heart period changes and other immeasurable factors. The model analyses the beat-to-beat series of the RR duration and of the interval between R- and T-wave apexes (RT period). Directly from these two signals, a parametric identification procedure and spectral decomposition techniques allow RT variability to be divided into RR-related and RR-unrelated parts and allow the RT-RR transfer function to be calculated. RT variability is driven by RR changes at low frequency (LF, around 0.1 Hz) and high frequency (HF, at the respiratory rate), whereas, at very low frequencies, the RR-unrelated contribution to the total RT variability is remarkable. During tilt at LF the RR-related RT percentage power increases (p < 0.02), the RR-unrelated RT percentage power remains unchanged, the gain of the RT-RR relationship largely increases (p < 0.001), and the phase is not significantly modified. Both the RR-related and the RR-unrelated RT percentage powers at LF are not affected by controlled respiration, and an increase in the RT-RR gain at HF is observed (p < 0.02). The proposed analysis may help to describe the regulation of the ventricular repolarisation process and to extract indexes quantifying the coupling between heart period and ventricular repolarisation interval changes.

Electrocardiography↗
PubMed1998

Performance assessment of standard algorithms for dynamic R-T interval measurement: comparison between R-Tapex and R-T(end) approach.

Three automatic approaches to ventricular repolarisation duration measurement (R-Tapex, R-T(end threshold) and R-T(end fitting) methods) are compared on computer-generated and real ECG signals, in relation to their reliability in the presence of the most common electrocardiographic artefacts (i.e. additive broadband noise and additive and multiplicative periodical disturbances). Simulations permit the evaluation of the amount of R-T beat-to-beat variability induced by the artefacts. The R-T(end threshold) method performs better than the R-T(end fitting) one, and, hence, the latter should be used with caution when R-T(end) variability is addressed. Whereas the R-Tapex method is more robust with regard to broadband noise than the R-T(end threshold) one, the reverse situation is observed in the presence of periodical amplitude modulations. A high level of broadband noise dose not prevent the detection of the central frequency of underlying R-T periodical changes. Comparison between the power spectra of the beat-to-beat R-T variability series obtained from three orthogonal ECG leads (X,Y,Z) is used to assess the amount of real and artefactual variability in 13 normal subjects at rest. The R-Tapex series displays rhythms at high frequency (HF) with a percentage power on the Z lead (57.1 +/- 4.9) greater than that on the X and Y leads (41.9 +/- 4.6 and 46.1 +/- 4.9, respectively), probably because of respiratory-related artefacts affecting the Z lead more remarkably. More uniform HF power distributions over X,Y,Z leads are observed in the R-T(end threshold) series (31.8 +/- 3.8, 39.2 +/- 4.1 and 35.1 +/- 4.2, respectively), thus suggesting minor sensitivity of the R-T(end threshold) measure to respiratory-related artefacts.

Algorithms↗
PubMed1998

Measuring regularity by means of a corrected conditional entropy in sympathetic outflow.

A new method for measuring the regularity of a process over short data sequences is reported. This method is based on the definition of a new function (the corrected conditional entropy) and on the extraction of its minimum. This value is taken as an index in the information domain quantifying the regularity of the process. The corrected conditional entropy is designed to decrease in relation to the regularity of the process (like other estimates of the entropy rate), but it is able to increase when no robust statistic can be performed as a result of a limited amount of available samples. As a consequence of the minimisation procedure, the proposed index is obtained without an a-priori definition of the pattern length (i.e. of the embedding dimension of the reconstructed phase space). The method is validated on simulations and applied to beat-to-beat sequences of the sympathetic discharge obtained from decerebrate artificially ventilated cats. At control, regular, both quasiperiodic and periodic (locked to ventilation) dynamics are observed. During the sympathetic activation induced by inferior vena cava occlusion, the presence of phase-locked patterns and the increase in regularity of the sympathetic discharge evidence an augmented coupling between the sympathetic discharge and ventilation. The reduction of complexity of the neural control obtained by spinalization decreases the regularity in the sympathetic outflow, thus pointing to a weaker coupling between the sympathetic discharge and ventilation.

Animals↗
PubMed1998

Respiratory sinus arrhythmia and cardiovascular neural regulation in athletes.

Studies using spectral analysis of cardiovascular variability as a noninvasive means for assessing autonomic nervous system activity have provided controversial results in athletes. One reason is that a slow breathing rate--a common feature in athletes--affects spectral estimation because it causes the low-frequency (LF) and high-frequency (HF) components to overlap. Low-frequency power increases during sympathetic activation; high-frequency corresponds to respiratory sinus arrhythmia. In this study, to assess how controlled respiration influences autonomic nervous system activity, we determined the effect of controlled and uncontrolled breathing conditions on cardiovascular variability. Our aim was to identify a standard respiratory rate for spectral estimation of cardiovascular neural control in athletes. During electrocardiographic recordings, subjects lay supine and breathed at their spontaneous frequency and at rates of 15, 12, and 10 to 14 (random) breaths x min(-1). Uncontrolled and random breathing rates significantly altered spectral sympathetic indices; conversely, 15 and 12 breaths x min(-1) redistributed respiratory related power through the HF, thus yielding correct LF power estimation. None of the breathing conditions significantly changed mean heart rate, arterial blood pressure, or spectral total power of cardiovascular variability. In conclusion, when power spectral analysis is used for assessing autonomic activity in athletes, respiration should be standardized at 15 breaths x min(-1). Controlled respiration at this rate leaves autonomic nervous system activity unchanged.

Adolescent↗
PubMed1998

Assessment of the coupling between RTapex and RR interval as an index of temporal dispersion of ventricular repolarization.

To evaluate the dynamic characteristics of the relationship between the RT and RR intervals we analyzed the RR/RTapex variability interaction with a dynamic parametric model whose parameters can be directly estimated from the beat-to-beat series RR and RTapex intervals. The model is designed to separate the fraction of RTapex variability driven by RR changes from that independent of RR variations and to quantify the gain and phase of the relationship between RR and RTapex intervals. The percentage of RTapex variability driven by RR variability was significantly greater in young normal subjects in comparison with postmyocardial infarction patients as well as with age-matched control subjects. This new approach based on the quantification of the RTapex variability dependent and independent of beat-to-beat RR interval changes could be used to quantify the degree of uncoupling between the two signals thus providing a new and noninvasive index of temporal dispersion of ventricular repolarization.

Adult↗
PubMed1997

Individual recognition by heart rate variability of two different autonomic profiles related to posture.

BACKGROUND: Power spectrum analysis of heart rate variability (HRV) can estimate the state of sympathovagal balance modulating sinus node activity. In view of the large distribution of spectral variables, a recognition of well-defined physiological conditions has never been attempted on an individual basis. METHODS AND RESULTS: We considered 10 spectral variables extracted from short segments (200 to 500 cardiac cycles) of 350 ECG tracings recorded in normal subjects in both supine and upright positions (700 patterns). The tracings were first ordered consecutively and subsequently assigned alternatively to a training or to a test set (each consisting of 175 cases, providing 350 patterns considered to be independent). A forecasting linear method estimated a normalized activation index (ranging from -1 for supine to +1 for upright) that concentrated the information derived from spectral variables and that identified, in the test set, individual by individual, approximately 84% of corresponding body postures. CONCLUSIONS: The combined use of spectral methodology and forecasting analysis has revealed an information content embedded, per se, in a short series of RR intervals capable of recognizing, individual by individual, two different autonomic profiles related to posture.

Adolescent↗
PubMed1997

Matching a computerized brain atlas to multimodal medical images.

A method for matching a digital brain anatomical atlas to multimodal medical images (MRI, PET, and SPET) was implemented. The digital atlas was derived from anatomical templates of the brain, cut according to the orbitomeatal orientation. The atlas consists of a set of contiguous slices schematically describing the brain as anatomical contours and of a set of regions of interest (ROIs) classifying the brain into functionally homogeneous areas. The matching procedure includes (a) an edge detection method for the extraction of anatomical contours and (b) a warping algorithm based on contour matching to fit the atlas to the individual brain anatomy, as described by MRI. Once the atlas is matched to MRI, the associated templates of ROI can be overlapped with functional PET/SPET studies, individually registered to MRI. The method was tested on MRI studies. The efficacy of the warping algorithm in overlapping atlas and MRI contours was assessed by calculating for each slice an index representing the extent of overlapping (I). Values of I in the range 0.8-0.9 were found (I = 1 complete overlapping). Local accuracy was also verified by comparing the position of correspondent anatomical ROI in the atlas and MRI images before and after warping. The atlas-matching procedure was applied to representative MRI/PET clinical images for an objective regional analysis of functional data.

Algorithms↗
PubMed1997

Total and partial coherence analysis of spontaneous and evoked EEG by means of multi-variable autoregressive processing.

The joint use of total and partial coherence between pairs of EEGs simultaneously recorded in a standard set, is shown to enhance what is caused by direct correlation between cortical subsystems and what is instead related to the spread of the electromagnetic field. A multi-variable autoregressive approach is employed in the computation, giving results even for a very short time window, thus allowing coherence to be investigated at the main cortical latencies of evoked potentials. In particular, when a combined visual and somatosensory stimulation is applied, cortical interactions are captured in the frequency domain.

Adult↗
PubMed1997

Autonomic function in narcolepsy: power spectrum analysis of heart rate variability.

Ten narcoleptic patients that had never been treated previously and ten healthy volunteers of comparable age underwent 48-h polygraphic recording to assess the effects of wakefulness and sleep on beat-to-beat heart rate variability by means of power spectrum analysis. The study revealed decreased power in the low frequencies (LF) during sleep (whereby an increase of the power in this band is associated with sympathetic activation) compared with wakefulness, with minimal values during stage 3-4 non-REM sleep and higher levels during REM sleep, both in patients and controls. Significantly reduced power in high frequencies (HF; mainly expression of parasympathetic control) and a significantly increased LF/HF ratio during wakefulness before sleep in narcoleptics compared with controls were found. Our study excludes a primary disturbance of cardiac autonomic nervous system in narcoleptics but suggests an altered circadian autonomic function in these patients.

Adult↗
PubMed1997

Vegetative background of sleep: spectral analysis of the heart rate variability.

Phasic events during sleep, either arousal or REM-burst related, and the associated transient cardiovascular responses have been the subject of intensive research in previous studies. However, nontransient (stationary) fluctuations in heart rate have been studied less extensively in the past. They allow a differentiation of the sympathetic and parasympathetic activation, which are related to a low-frequency (LF) and a high-frequency (HF) component of the heart rate variability (HRV) signal, respectively. The resulting LF/HF ratio is a quantitative index of the sympatho-vagal balance. Sleep polygrams from 20 healthy volunteers were recorded in a sleep laboratory. Standard vegetative tests (orthostatic and Valsalva tests) were evaluated. A segmentation procedure, performed on the HRV signal, separated 70-130 transients during the night from the records of stationary heart rate fluctuations. From these periods the sympatho-vagal balance, quantified by the LF/HF, was computed by means of spectral analysis. The more synchronized the sleep was, the more the LF/HF decreased, whereas the LF/HF was significantly increased during REM sleep, indicating a sympathetic predominance during this period. Such an increase was also evident during the last 15 min before REM sleep onset. Results suggest that spectral analysis of the HRV provides additional information of the ultradian rhythmic behavior of the autonomic nervous system function beyond the traditional cardiovascular measurements (mean heart rate, blood pressure, etc.). In contrast to these measurements, which generally show a continuously decreasing cardiovascular activity, as the night proceeds, the results of this study reveal a high sympathetic peak activity during the later REM sleep periods, which is comparable in magnitude to that found in the upright position in wakefulness. This activity may be associated to the well-known incidence peak of ischemic events in the early morning hours.

Arousal↗