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Biomedical subjects

G Calcagnini

Publications and source records attributed to G Calcagnini.

At least 37 records · Page 2Linked to original sources
PubMed2001

Management of patients with atrial fibrillation: different therapeutic options and role of electrophysiology-guided approaches.

At present the approach to atrial fibrillation treatment is based on the electrophysiological patterns of atrial fibrillation (on the basis of multiple intra-atrial recordings or sophisticated new mapping techniques) only in a restricted minority of patients, those who are candidate to ablation of the substrate and/or of the triggers. Atrial fibrillation has a broad spectrum of clinical presentations and a heterogeneous electrophysiological pattern. The treatment of this arrhythmia, both with drugs and non pharmacological treatments, has been based, classically, on empirical basis and on a clinically-guided staged-approach. The limitations of pharmacological treatment led in recent years to the development of a wide spectrum of non pharmacological treatments. This implies a change in the approach to atrial fibrillation and the need to identify potentially ideal candidates to complex and expensive treatments. In this view it is currently under investigation the possibility to identify potential responders to a definitive treatment or a combination of treatments (both pharmacological and non-pharmacological) on the basis of the electrophysiological pattern.

Anti-Arrhythmia Agents↗
PubMed2000

Transient phase locking patterns among respiration, heart rate and blood pressure during cardiorespiratory synchronisation in humans.

The interactions between respiration, heart rate and blood pressure variability (HRV, BPV), are considered to be of paramount importance for the study of the functional organisation of the autonomic nervous system (ANS). The aim of the reported study is to detect and classify the intermittent phase locking (PL) phenomena between respiration, HRV and BPV during cardiorespiratory synchronisation experiments, by using the following time-domain techniques: Poincaré maps, recurrence plots, time-space separation plots and frequency tracking locus. The experimental protocol consists of three stages, with normal subjects in paced breathing at 15, 12 and 8 breaths min-1. Transient phenomena of coordination between respiration and the major rhythms of HRV and BPV (low and high frequency, LF and HF) have been detected and classified: no interaction between LF and HF rhythms at 15 breaths min-1; short time intervals of stable 1:2 frequency and phase synchronisation during the 12 breaths min-1 stage; 1:1 PL during the 8 breaths min-1 stage. 1:1 and 1:2 PL phenomena occurred when the respiration frequency was quite close to the LF frequency or when it was about twice the LF frequency, respectively. The complex organisation of the ANS seems to provoke transient rather than permanent PL phenomena between the co-ordinating components of respiration and cardiovascular variability series.

Adult↗
PubMed2000

Automated classification of human atrial fibrillation from intraatrial electrograms.

The assessment of the degree of organization and the classification of atrial fibrillation (AF) according to the types defined by Wells usually resorts to the visual inspection of bipolar intraatrial electrograms. The focus of this study was to test seven parameters aimed to quantify the degree of organization of the electrograms, and then to design a final classification scheme based on a multidimensional, minimum-distance analysis. The following parameters were tested: mean atrial period (AP) and its coefficient of variation (CV); number of points lying at the baseline (NO) and the Shannon entropy (EN) of the amplitude probability density function (APDF); depolarization width (F-WIDTH); and correlation waveform analysis (CWA) and electrogram bandwidth (BW). The signal database consisted in a set of 160 AF strips of Type I, II, and III AF, scored by an expert cardiologist (60 Type I, 40 Type II, 60 Type III) and further divided in a training set (60) and a test set (100). Strips were 6 seconds long and were recorded with 5-mm interspace bipolar catheters from electrically induced (n = 13) and chronic (n = 10) patients. A classification algorithm based on a minimum-distance (Mahalanobis distance) discriminant analysis was tested. Using a single parameter, the best discriminations were provided by NO, F-WIDTH, and CV. F-WIDTH was found strongly inversely correlated to NO (r = -0.90). Of all the two-parameter combinations, CV-NO provided the best classification: 92 of 100 segments were correctly classified with sensitivity > 90% and specificity > 92%. A further improvement was obtained by including BW as a third parameter (93/100 correctly classified). The use of more than three parameters not only failed to improve, but even degraded the classification.

Algorithms↗
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↗
PubMed2000

Effects of sleep stage and age on short-term heart rate variability during sleep in healthy infants and children.

STUDY DESIGN: Power spectrum analysis of heart rate variability (HRV) is a noninvasive technique that provides a quantitative assessment of cardiovascular neural control. Using this technique, we studied the autonomic nervous system changes induced by sleep in 14 healthy subjects: 7 infants (mean age, 9.40 +/- 2.32 months) and 7 children (mean age, 8.93 +/- 0.65 years) during a standard all-night polysomnographic recording. Our primary aim was to assess the effect of sleep stage and age on short-term HRV during sleep in healthy infants and children. Power spectral density was estimated by autoregressive modeling over 250 consecutive R-R intervals. In this study, we mainly considered two spectral components: the high-frequency (HF) component (0.15 to 0.40 Hz), which reflects parasympathetic cardiovascular modulation; and the low-frequency (LF) component (0.04 to 0.15 Hz), generally considered due to both parasympathetic and sympathetic modulation. RESULTS: Heart rate was higher (p < 0.01 in all sleep stages) and total power lower (p < 0. 02) in infants than in children. HF power was higher in children than in infants (p < 0.05). In infants and children, the ratio between LF and HF powers changed with the various sleep stages (p < 0.02 in infants; p < 0.01 in children): it decreased during deep sleep and increased during rapid eye movement sleep. However, it was invariably lower in children than in infants. CONCLUSION: These findings show that the sleep stage and age both significantly influence short-term HRV during sleep in healthy infants and children. Hence, to provide unbiased results, HRV studies investigating the effects of age on autonomic nervous system activity should segment sleep into the five stages. In addition, despite a relatively small study sample, our data confirm greater parasympathetic control during sleep in children than in infants.

Autonomic Nervous System↗
PubMed2000

Spontaneous fluctuations of human pupil reflect central autonomic rhythms.

Aim of this study is to assess whether and to what extent LF and HF rhythms contribute to spontaneous pupil diameter fluctuations at rest and during sympathetic activation by Head-Up Tilt Test 70 degrees. ECG, Finapres and Respiration data from 10 normal subjects were recorded simultaneously to spontaneous pupil diameter fluctuations (SPDF). The respiratory rhythm and the LF component were clearly detected in all the SPDF series. The cross-spectrum analysis gave significant results (> 0.5) in HF band. During tilt, a reduction in the total variability with a relative increase of the LF component was observed in HR, BP and SPDF signals. The multivariate analysis of the SPDF and of the cardiovascular variability series allows new insights into the physiology of pupil neural control. The effect of tilting on SPDF spectra and the physiological background of the pupil control are consistent with the hypothesis that pupil fluctuations reflect a generalized increase of the sympathetic tone.

Adult↗
PubMed2000

Microvascular blood flow fluctuations during tilt table induced syncope.

Aim of this study is to investigate the changes, in the frequency domain, of microvasculature blood flow (BF) occurring in neurally mediated syncope. We studied 20 patients with history of recurrent syncope and 10 control subjects. Peripheral BF was measured (laser Doppler technique) in the palmar region (PBF) and the manubrium sterni (SBF), together with ECG, respiration activity (RA) and blood pressure (BP), at rest (5 minute) and during 70 degrees head-up tilt test. SBF and PBF appear to be characterized by oscillations around 0.16 Hz (0.15-0.19 Hz), that do not have correspondence in the other cardiovascular variability signals. Mean BF was not significantly altered in tilt negative, control and tilt positive groups (11 patients) during tilt. In the tilt positive group a decrease of mean PBF and SBF and an increase of the oscillation frequency of PBF and SBF was observed in close proximity of the development of symptoms.

Blood Flow Velocity↗
PubMed1999

Comparing the effects of nasal synchronized intermittent positive pressure ventilation (nSIPPV) and nasal continuous positive airway pressure (nCPAP) after extubation in very low birth weight infants.

In this study we hypothesized that nasal synchronized intermittent positive pressure ventilation (nSIPPV) would provide more ventilatory support than nasal continuous positive airway pressure (nCPAP) in the immediate post-extubation period in very low birth weight (VLBW) infants. We tested this hypothesis by comparing the effects of these two ventilatory techniques on ventilation, gas exchange, and patient inspiratory effort in 11 preterm infants immediately after extubation. All neonates studied (BW: 1141+/-(SEM) 53 g; GA: 28.1+/-(SEM) 0.5 wks) had received mechanical ventilation because of respiratory distress at birth and were extubated by day 14 of life. Nasal SIPPV and nCPAP were applied in random order to each infant after extubation so that each was his/her own control. Both nCPAP and nSIPPV were delivered at end-expiratory pressures (PEEP) of 3 cm H2O. Inspiratory times (Ti) and peak inspiratory pressures set during nSIPPV were the same as those used at the time of extubation. Recordings lasted 45 min in each mode of ventilation. Tidal volume (Vt), minute volume (Ve), respiratory rate (RR), airway pressure (Paw), transcutaneous PO2 (TcPO2) and PCO2 (TcPCO2) as well as phasic esophageal pressure deflections (Pe), as an estimate of inspiratory effort, were measured. The measurements obtained during both modes of ventilation indicated significant differences between the two techniques. Indeed, application of nSIPPV was associated with a statistically significant increase in Vt and Ve. In addition, Pe decreased by 30% during nSIPPV (P<0.01). TcPCO2 was statistically significantly lower during nSIPPV than nCPAP, and RR as well. These data therefore suggest that nSIPPV may provide more ventilatory support than nCPAP in the post-extubation period with less patient inspiratory effort.

Humans↗
PubMed1999

[Cardiovascular neuroregulation and rhythms of the autonomic nervous system: frequency domain analysis].

Studies using spectral analysis of cardiovascular variability series, as a non invasive tool for assessing the autonomic nervous system activity, have attracted growing interest in the last 20 years. Short-term recordings of heart rate variability distinguish two main spectral components: a high-frequency (HF) component (ranging between 0.15-0.40 Hz), and a low-frequency (LF) component (ranging between 0.04-0.15 Hz), respectively considered markers of parasympathetic and sympathetic control. Spectral analysis of microcirculatory blood flow, by using laser Doppler flowmetry, recently disclosed the presence of similar rhythms. Although a general agreement about the amplitude and frequency of these spectral components has not been gained yet, evidences of an autonomic nervous system role have been collected. Also the pupil diameter spontaneously fluctuates in the HF range. The aim of this study was to design an experimental set up for the simultaneous and continuous recording of heart rate, blood pressure, respiratory activity, peripheral blood flow, and pupil diameter fluctuations in order to investigate whether common spontaneous rhythms could be detected into the variability series. We enrolled 10 normal volunteers (range 24-28 years). The variability series of heart rate, blood pressure, respiratory activity, peripheral blood flow and pupil diameter were obtained at rest and during sympathetic activation by head-up tilt test 70 degrees. Subjects were instructed to breath at 15 breath/min following an audio signal and adjusting their tidal volume to a comfortable level. Peripheral blood flow was non invasively monitored with laser Doppler technique, with the two probes located in the palmar site of the hand and in the sternum. We continuously assess the pupil diameter fluctuations by a custom, portable, infrared TV pupillometer. Spectral density was estimated by autoregressive modeling on 250-point segments. The respiratory rhythm was clearly detected in all the variability series. Oscillations in the LF band were detected in heart rate, blood pressure and in the laser Doppler signals of the hand, as well as in the pupil diameter, but not always in the laser Doppler flow of the sternum. In this last signal an harmonic component at 0.16-0.17 Hz was detected. A reduction in the total variability, with a relative increase in the LF component was observed during head-up tilt test in the heart rate, blood pressure, peripheral blood flow and pupil diameter signals. These findings are consistent with the increased sympathetic modulation induced by the head-up tilt test. These data confirm previous findings and observations, collected with different techniques and for different purposes. Whether these rhythms can be expression of central common oscillators or reflex mechanical factors is of primary importance for possible clinical applications of this approach.

Adult↗
PubMed1998

Cardiac autonomic dysfunction in patients with Alzheimer disease: possible pathogenetic mechanisms.

We studied a possible correlation between autonomic cardiac activity and the level of the red blood cell acetylcholinesterase (AChE) in patients with probable Alzheimer disease (AD). The influence of cholinesterase inhibitor treatment on this autonomic activity was evaluated. Twelve patients satisfying the NINCDS-ADRDA criteria of probable AD and 10 healthy controls were studied. Autonomic cardiac activity was evaluated by means of power spectral analysis (PSA) of heart rate variability (HRV) using an autoregressive algorithm on 250 consecutive electrocardiographic R-R intervals. All patients received oral eptastigmine, a new cholinesterase inhibitor, for 1 month. Before treatment, a simultaneous recording of the electrocardiographic and respiratory activities was performed at rest and subsequently during head-up tilt test at 700. Recording was repeated on the last day of treatment. The level of AChE activity during each recording was also evaluated. Spectrum power was calculated in three main frequency bands: high frequency (HF), 0.15-0.4 Hz; low frequency (LF), 0.04-0.15 Hz; very low frequency (VLF), <0.04 Hz. In addition, we calculated the total spectrum power (TSP) and the LF/HF ratio. The TSP and the absolute value of each spectral component were significantly lower in AD patients than in controls. In contrast with controls, AD patients did not show any significant change before treatment in either the LF and HF components or in the LF/HF ratio during the tilt test. However, the modification in the LF component, induced by tilting, showed a significant correlation with the level of AChE activity (p < 0.03). During the tilt test, the treatment caused changes in LF and HF components and in the LF/HF ratio similar to those observed in controls. These results suggest that the presence of autonomic cardiac dysfunction in AD patients might be due to a cholinergic deficit in the peripheral autonomic nervous system. Some aspects of this autonomic dysfunction can be normalized by cholinesterase inhibitor treatment.

Acetylcholinesterase↗
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↗
PubMed1995

Sympathetic-parasympathetic activation during spontaneous attacks of cluster headache: evaluation by spectral analysis of heart-rate fluctuations.

Twenty-four hour ECG Holter and blood-pressure monitorings were performed in eight patients suffering from cluster headache. Spectral analysis of heart-rate fluctuation was used to assess the autonomic balance under basal conditions, after head-up tilt, and during a spontaneous attack. Normal autonomic balance was found at rest and during sympathetic activation obtained with head-up tilt in the interparoxysmal period. Before the onset of headache, an increase in the low-frequency (LF) component of the power spectrum was apparent in all patients. This sign of sympathetic activation was followed by an increase in the high-frequency (HF) component that developed about 2000 beats after the onset of headache and rapidly overcame the LF component until the end of pain. Significant differences were found when comparing the spectral parameters [total spectral values (TP), power of the LF and HF components and LF/HF ratio] obtained before, during and after headache. During the attack, blood pressure increased and heart rate decreased in all subjects. There appears to be a primary activation of both sympathetic and parasympathetic functions in cluster headache attacks. The sympathetic component seems to be involved mostly in the development of the attack, whereas the parasympathetic activation seems to occur, following the onset of the attack, independently of the pain.

Adult↗
PubMed1992

[Modification of the sympatho-vagal interaction in mitral valve prolapse syndrome. Evaluation of heart rate variability by spectrum analysis].

To determine whether clinical manifestations in patients with mitral valve prolapse (MVP) are associated with altered sympatho-vagal tone, 46 patients (mean age 27 +/- 6, range 20-45 years; 18 males and 28 females) were studied by power spectrum analysis of RR variability. Patients were divided in 2 groups, according to echocardiographic criteria: Group A: 11 patients with classical MVP; Group B: 35 patients with non classical MVP. These patients were compared with 30 healthy subjects (Group C) well matched for age, body surface area and heart rate. Our findings indicate that at rest there is a significant difference in the high-frequency component between Group A and Group C. Similarly, during the increase in sympathetic activity induced by 70 degrees head-up tilt all groups showed an increase in the low-frequency component, that was more evident in Group A. The data generated from our laboratory suggest that mitral regurgitation (Group A) is a probable cause of vagal tone increase and that there is an adaptive long-term mechanism towards sympathetic conditions. In addition, probably the normalization, demonstrable by the effect of sympathetic activity in tilt, can mask a dysfunction that may be differently evoked.

Adult↗
PubMed1989

[Effects of acute loading of alcohol on platelet aggregation in normal subjects].

Ten healthy subjects were submitted to alcohol loading (0.8 g/kg body weight; average alcohol blood level 0.97 g 0/00). The number of platelets, hematocrit and ADP-induced platelet aggregation curves did not show any variation from baseline. Significant changes (p less than 0.05) were observed as regards latent period (increased) and maximum amplitude (reduced) for collagen-induced platelet aggregation. In agreement with others, the authors conclude that alcohol definitely inhibits platelet aggregation.

Adult↗