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M Villani

Publications and source records attributed to M Villani.

At least 19 recordsLinked to original sources
PubMed1998

Multipolar laminated electromagnet for low-field magnetic resonance imaging and electron paramagnetic resonance imaging.

A cylindrical 16-pole electromagnet (EM) for electron paramagnetic resonance imaging (EPRI) and low-field magnetic resonance imaging (MRI) has been designed by means of two-dimensional and three-dimensional (3-D) finite element analysis (FEA). The use of an automatic procedure that combines FEA with a minimization routine allowed the optimization of the design, in order to improve the homogeneity along the axis of the EM. A prototype has been built by using electrical steel sheets that were cut by laser; this solution reduced significantly the manufacturing cost. The EM operates with a maximum flux density, in the bore, of 0.08 T and has a homogeneity along the axis of about 40 parts per million (ppm) in a spherical region 10 cm in diameter. It generates the main field and two of the three field gradients required in the 3-D image reconstruction. Good agreement was found between the results of simulation and the measured values.

Electromagnetic Phenomena↗
PubMed1998

Intra-atrial defibrillation of human atrial fibrillation.

Low-energy intra-atrial defibrillation is a new therapeutic option for restoring sinus rhythm in patients with atrial fibrillation (AF). The success rate is quite high when right atrium-coronary sinus or right atrium-pulmonary artery electrode configurations are used, although the former is associated with a slightly lower defibrillation threshold. Several issues regarding the safety and tolerability of the procedure remain unresolved. Our experience and that of others indicate that low-energy intra-atrial cardioversion is safe even during exercise, provided the shock is well synchronized with the QRS and the preshock RR interval is > 500 msec. Reported defibrillation thresholds in patients with persistent AF range from 4 to 8 J, and shocks of this type inevitably are associated with some degree of discomfort. Measures aimed at lowering the defibrillation threshold (e.g., use of biphasic waveforms, antiarrhythmic pretreatment, and use of a single effective shock, as opposed to the multiple shocks delivered in research settings) can be expected to increase patient tolerance and extend the indications for low-energy intra-atrial cardioversion. The procedure currently is indicated for patients with persistent AF who are resistant to external defibrillation unable or unwilling to undergo general anesthesia. The procedure could be expanded to patients affected by obesity in whom the efficacy of external cardioversion is lower.

Atrial Fibrillation↗
PubMed1998

[The efficacy of high- and low-energy intracavitary cardioversion in chronic atrial fibrillation refractory to transthoracic cardioversion].

BACKGROUND: The purpose of our study was to evaluate the efficacy and safety of intracavitary cardioversion (IC) with either high (HEIC) or low (LEIC) energy in patients with chronic atrial fibrillation (AF) refractory to external cardioversion. METHODS: Forty patients underwent IC with either high (30 pts) or low energy (10 pts); HEIC was performed by delivering one or more shocks between one electrode of the lead positioned in the right atrium and a back plate. The following energy values were used in sequence: 100, 200, 300 joules. In LEIC shocks were delivered between two custom-made decapolar leads (one in the coronary sinus and another one in the right lateral atrial wall) beginning from 50 Volts and increasing the voltage by steps of 50 Volts. Another catheter in the right ventricular apex was used for ventricular synchronization. RESULTS: Sinus rhythm was restored in 24/30 (80%) patients undergoing HEIC and in 10/10 (100%) patients undergoing LEIC. No serious or permanent complications occurred. CONCLUSIONS: HEIC and LEIC are effective in patients with AF refractory to external cardioversion. Both the procedures seem to be safe.

Adult↗
PubMed1997

Modelling Bacterial Degradation of Organic Compounds with Genetic Networks

The bacterial degradation of organic compounds plays a crucial role in the biogeochemical cycles of the earth and in the clean-up of contaminated soils. The processes are carried out by bacterial consortia, rather than isolated strains, which are usually modelled by phenomenological kinetic equations which describe a fictitious, homogeneous bacterial species which mimics the behaviour of the consortium. An alternative modelling framework is presented here, where the bacterial consortia are considered as networks of genes interacting with other genes as well as with chemicals, which may be either introduced from outside or produced by bacterial metabolism. The model is based on an extension of the random Boolean network model of genetic networks, which makes use of continuous dynamical variables. Three different models are introduced, which differ in the way how they account for the existence of different species: (i) a single supercell model, where all the genes can interact strongly with each other; (ii) a graded interaction model, where genes interact strongly within a species, and weakly among different species; and (iii) a separate subsets model, where genes interact only within species. It is shown how this modelling framework is sound, as it is able to reproduce some of the generic behaviours of bacterial consortia, describing experimentally observed phenomena like population changes induced by contamination, and prey-predator dynamics.Copyright 1997 Academic Press Limited Copyright 1997 Academic Press Limited

Journal Article↗
PubMed1997

Local capture by atrial pacing in spontaneous chronic atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is considered to be maintained by multiple reentrant circuits without or with a very short excitable gap. However, the possibility of local atrial capture has been shown recently in experimental AF or induced AF in humans. METHODS AND RESULTS: This study was undertaken to evaluate the feasibility of atrial capture-suggestive of an excitable gap-in spontaneous chronic AF. Decremental pacing was performed in 47 right atrial sites in 14 patients with chronic AF, not taking antiarrhythmic drugs. A Franz catheter (for pacing and monophasic action potential recording) and a recording quadripolar catheter positioned about 10 mm apart were used. Local capture was achieved in 41 (87.2%) sites for a total of 100 captures. In 71 episodes the capture was lost within 15 seconds, while in the remaining 29, pacing was stopped after 15 seconds of stable capture. AF types immediately before capture were type 1 in 83 and type 2 in 17 episodes. Type 3 AF was never captured. Pacing cycle at capture was 175.7 +/- 20.9 ms. The baseline atrial interval (FF) was 185.4 +/- 24.5, significantly longer than the FF recorded during pacing immediately before capture (176.0 +/- 19.8 ms) (P < .02). CONCLUSIONS: During spontaneous chronic AF in humans, (1) local capture by atrial pacing is possible up to at least 15 mm from the pacing site, (2) regional entrainment is possible during type 1 and type 2 AF but not type 3 AF, and (3) pacing before capture accelerates AF, probably by transient or local capture. These findings suggest that an excitable gap is present in chronic AF, therefore supporting the hypothesis that leading circle reentry is not the unique electrophysiological mechanism maintaining the arrhythmia.

Aged↗
PubMed1997

Changes in intracardiac atrial cardioversion threshold at rest and during exercise.

OBJECTIVES: We sought to analyze in patients with chronic atrial fibrillation (AF) the change in the intracardiac atrial defibrillation threshold (ADT) at rest and during exercise, to quantify the effective risk of low energy endocavitary cardioversion during the effort and to compare the ADT of chronic and reinduced AF. BACKGROUND: Low energy endocavitary cardioversion is a new alternative to transthoracic shock in patients with chronic AF. Nevertheless, patient discomfort and possible induction of ventricular arrhythmias should be further evaluated. METHODS: Sixteen patients with chronic AF were included in the study. Two 6F custom-made catheters (Electro-Catheter, Inc.) were used for shock delivery and one tetrapolar lead for ventricular synchronization. Without sedation and in a random order, patients underwent two sequences of shocks to determine the ADT at rest and during exercise. Exercise was performed isometrically by the superior limbs. Atrial fibrillation was reinduced by atrial pacing. After each shock, the patients were requested to grade their discomfort with a score from 1 to 5. The power of the study was > 90% in detecting a 25% difference in the ADT between groups. RESULTS: Patients were classified into two groups: Nine patients (group A) underwent the first cardioversion during exercise; seven patients (group B) underwent the first cardioversion at rest. In total, the mean (+/-SD) ADT was 6.70 +/- 1.54 J during exercise and 7.02 +/- 1.82 J at rest (p = 0.59). A significantly lower ADT was observed in the second shock sequence than the first one (6.32 +/- 2.09 J vs. 7.40 +/- 0.87 J, p < 0.05). The discomfort score was 3.25 +/- 0.86 at rest and 2.94 +/- 0.77 during exercise (p = 0.09). No complications occurred. CONCLUSIONS: Low energy endocavitary cardioversion is a safe and effective procedure in patients with chronic AF. Discomfort is not generally severe enough to result in procedure termination. The ADT is not influenced by exercise and is higher in chronic than in reinduced AF.

Adult↗
PubMed1997

[Electrophysiologic characteristics of the atrium during chronic atrial fibrillation in man].

AIM OF THE STUDY: To evaluate the electrophysiologic characteristics of human atria during chronic atrial fibrillation. METHODS: The study was performed in 24 patients who underwent low energy intracardiac atrial cardioversion for chronic atrial fibrillation before the procedure itself. No patients have been assuming antiarrhythmic drugs for a period of at least 5 half-lives of the drug. In 10 patients the possibility of local capture in several atrial sites (7 tested) by means of high-rate atrial pacing was evaluated. A Franz catheter for recording of monophasic action potential (MAP) and for atrial stimulation was positioned in the right atrium at a distance of 1 cm from a quadripolar catheter which was also positioned for the recording of the bipolar electrogram by the distal and proximal pairs and of the unipolar electrogram by the distal electrode. A decapolar catheter for shock delivery was positioned in the coronary sinus as well. In the remaining 14 patients an additional quadripolar catheter for His recording was positioned but atrial stimulation was not performed. Furthermore, recordings of the bipolar and unipolar electrograms were obtained in several sites and the correlation between MAP and bipolar electrogram morphology was evaluated. The existence of a difference in fibrillation cycle-length in different sites suggestive of a dispersion of refractory periods was also screened. Wells' and Waldo's classification was used for bipolar electrograms whereas MAP was classified into type 1 (regular), type 2 (partially irregular), and type 3 (totally irregular). RESULTS: In 10 patients submitted to atrial stimulation, local capture was obtained in 37 out of 43 stimulation sites (86%). Local capture was more frequently obtained in the lateral wall than in other sites (p < 0.05). The capture was obtained only in type 1 and type 2 atrial fibrillation. In the remaining 14 patients a perfect correlation (100%) between type 1 and 3 atrial fibrillation and type 1 and 3 MAP respectively was observed. In type 2 atrial fibrillation the correspondence was lower (67%). Fibrillation cycle-length contemporary recorded in the 6 different atrial sites were significantly different in 8 patients out of 12 (67%) in whom a stable recording could be obtained in basal conditions. CONCLUSIONS: 1) In chronic atrial fibrillation an excitable gap allowing local capture is present in the majority of patients and in most atrial sites, at least in the right atrium. 2) The morphology of bipolar and MAP recordings are fairly correlated and they reflect the complexity and the degree of synchronization of the arrhythmia. 3) A dispersion of refractoriness seems to contribute to the maintainance of the arrhythmia.

Action Potentials↗
PubMed1996

Cardiovascular reactivity of mitral valve prolapse patients during experimental stress exposure: evidence for a functional nature of cardiovascular symptoms.

We studied a group of 18 patients with mitral valve prolapse (MVP) and a group of 20 healthy controls. Subjects in both groups were subjected to a 1-h experimental stress exposure during which Holter-ECG monitoring was performed and was then continued for the following 24 h. MVP patients complained of significant cardiac palpitation during the stress session, but ECG examination did not reveal significant inter-group differences. However, the two groups did show statistically significant differences in some psychometric measurements (Toronto Alexithymia Scale, Anxiety Sensitivity Index, Fear Questionnaire, Beck Depression Inventory, and Harm Avoidance subscale of Tridimensional Personality Questionnaire) that underlie personality traits known to be important in the process fostering functional somatic symptoms, according to the somatosensory amplification model. As no objective signs of cardiac rhythm modification were found in MVP patients under stress, we postulate that the symptoms for which these patients were referred have a functional nature, and that there is no pathogenetic link with the underlying valvular defect.

Adult↗
PubMed1996

[Ventricular nodal reentry tachycardia without ventricular dilatation: diagnosis and treatment by radiofrequency catheter ablation].

Bundle branch reentry tachycardia has been reported in patients with left ventricular dilatation, especially in those with dilated cardiomyopathy and aortic regurgitation. These patients show aspecific intraventricular conduction delay on the ECG and a prolonged H-V interval at the electrophysiologic study. We report 2 cases of bundle branch reentry tachycardia in patients without left ventricular enlargement to help the correct diagnosis of the arrhythmia. A correct diagnosis is very important because bundle branch reentry tachycardia is easily and safely treated by right bundle transcatheter radiofrequency ablation. We also report electrophysiologic characteristics we found during the study and the ablation: -contrary to the data reported in literature, at ventricular tachycardia starting, modifications of the V-V interval are not always preceded by similar variations in the H-H interval. -during right bundle radiofrequency ablation, a QRS narrowing may precede right bundle branch block appearance. This QRS normalisation should induce to continue and not to stop energy delivering.

Aged↗
PubMed1995

LGANN: a parallel system combining a local genetic algorithm and neural networks for the prediction of secondary structure of proteins.

In this work we describe a parallel system consisting of feed-forward neural networks supervised by a local genetic algorithm. The system is implemented in a transputer architecture and is used to predict the secondary structures of globular proteins. This method allows a wide search in the parameter space of the neural networks and the determination of their optimal topology for the predictive task. Different neural network topologies are selected by the genetic algorithm on the basis of minimal values of mean square errors on the testing set. When the alpha-helix, beta-strand and random coil motifs of secondary structures are discriminated, the maximal efficiency obtained is 0.62, with correlation coefficients of 0.35, 0.31 and 0.37 respectively. This level of accuracy is similar to that previously attained by means of neural networks without hidden layers and using single protein sequences as input. The results validate the neural network topologies used for the prediction of protein secondary structures and highlight the relevance of the input information in determining the limit of their performance.

Algorithms↗
PubMed1995

[Human dirofilariasis in southern Italy. III. The Molise region].

A case of subcutaneous human dirofilariasis associated with Dirofilaria repens in the arm of a 9-year-old child resident in Campobasso is described. It is the first report of the nematode in the Molise region. Blood samples taken from dogs in the same region, confirmed the presence of D. repens microfilariae in the natural reservoir, few km from the clinical case.

Animals↗
PubMed1994

[Immigrant child: cognitive research on the state of health in Rome].

Surveying and assessing chemical statistic data on the state of health of immigrant children in Rome, the authors wish a greater engagement of political administrative authorities. In this way children, whose families find integration in our society hard, could at least have an effective medical assistance.

Adolescent↗
PubMed1993

Automatic analysis of high resolution atrial activation in mitral valve stenosis.

High resolution P-waves of 28 patients having a mean age of 45 years and affected by isolated mitral valve stenosis (nine of whom showed paroxysmal atrial fibrillation) have been compared with those obtained from 30 healthy subjects about 35 years old. Our primary aim was to characterize the signal-averaged P-wave in mitral valve stenosis. Parameters which differed between the two groups in time domain analysis were the P-wave duration, the abscissa of the maximum positive voltage amplitude, the peak-to-peak amplitude and the integrated voltage-time product, which turned out to be greater in the patient class than in the healthy set; furthermore, in the frequency domain analysis, amplitudes in the range from 37 to 60 Hz were greater in healthy subjects than in patients. A successive analysis carried out to predict those patients with mitral valve stenosis who are at risk of developing paroxysmal atrial fibrillation showed that the P-wave duration and the amplitudes (in the range 60-106 Hz) were the most distinctive parameters, but, unfortunately, without any significant difference with respect to those of patients with mitral valve stenosis alone. Finally, some correlations between the age, the P-wave duration and the left atrial diameter of patients, were revealed to exist only in patients affected by episodes of atrial fibrillation.

Adult↗
PubMed1993

[Cor triatriatum associated with inter-atrial defect: diagnosis by transesophageal echocardiography].

Cor triatriatum (CT) is a rare malformation consisting of a fibromuscolar membrane that subdivides the left atrium in a postero-superior (or accessory) chamber and an antero-inferior chamber (true left atrium, containing the left atrial appendage). In its classic form, the accessory chamber receives the pulmonary veins and communication with the left atrium is accomplished by way of one or more fenestrations in the membrane. The malformation is usually isolated, but in about one in four patients is associated with other congenital defects of a complex nature. We describe a case of CT associated with atrial septal defect, in which transthoracic echocardiography failed to document the existence of CT membrane, while this abnormality was clearly seen and defined by use of transesophageal echocardiography. The patient was a 26 year-old girl, presented at our outpatient clinic after an episode of palpitations and dyspnea, which lasted for two hours. She suffered of mild dyspnea on exertion during the last three months. Physical examination revealed the typical findings of an atrial septal defect (ASD), and the electrocardiogram revealed right bundle branch block. The two-dimensional echocardiography disclosed an ostium secundum ASD with left to right shunt; dilatation of the right cavities; paradoxical movement of the interventricular septum. A small linear echo originating from the lateral wall of the left atrium, with no evidence of turbulent flow on pulsed wave Doppler and color flow examination, was interpreted as an artifact. Transesophageal echocardiography clearly visualized a tense, bulging membrane separating left atrium into two chambers.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Multiple↗
PubMed1992

[Ventricular late potentials in hypertrophic cardiomyopathy: personal contribution and analysis of the literature].

BACKGROUND: Patients with hypertrophic cardiomyopathy are at increased risk of sudden death. Recently it has been investigated whether late potentials can be useful markers of that risk in such patients, with discordant results. The aim of our study was to detect a correlation, if any, between late potentials, ventricular tachycardia and the hypertrophy extension. METHODS: Twenty-five patients were enrolled, 19 males and 6 females, mean age 40.40 +/- 15.02 years. Each underwent 24h Holter monitoring, averaged ECG, M-Mode and 2-D Echo. The hypertrophy was considered extensive (septum and free wall) or non extensive (septum and/or apex). RESULTS: Late potentials of a mean duration of 37 +/- 14.83 ms were recorded in 5/7 patients with documented ventricular tachycardia vs in none of the non tachycardia group. Sensibility was 100%, specificity 71% and predictive value 100%. Late potentials were present in 8.3% of patients with non extensive and in 30.8% of patients with extensive hypertrophy (p = NS). CONCLUSIONS: From our data it seems that extensive hypertrophy is present in about half of patients with hypertrophic cardiomyopathy, and this roughly correlates with a more frequent ventricular tachycardia and with late potentials. Furthermore, late potentials are strictly related to the incidence of ventricular tachycardia in this disease, just as in ischemic heart disease or in idiopathic dilated cardiomyopathy. The small number of our cases may not be sufficient to reach a significant statistical correlation between late potentials and hypertrophy, but we believe that the trend is very promising.

Action Potentials↗
PubMed1992

[Paroxysmal atrial fibrillation in patients with chronic ischemic cardiopathy: a study of high-resolution atrial activation].

BACKGROUND: Patients with ischemic heart disease and episodes of paroxysmal atrial fibrillation are at major risk of stroke. In order to prevent such episodes, through the identification of patients prone to atrial fibrillation, we investigated the high-resolution atriogram of 65 patients with chronic ischemic heart disease, 54 male and 11 female, mean age 60.22 +/- 9.04 years. Based on previous documented episodes of atrial fibrillation, the patients were divided into two groups: group A, 45 males and 3 females, mean age 58.92 +/- 7.68 years, without atrial fibrillation; group B, 9 males and 8 females, mean age 63.88 +/- 11.6 years, with atrial fibrillation. RESULTS: High resolution atrial duration (100-300 Hz) in group B (with atrial fibrillation) was higher than in group A (without atrial fibrillation) (140.59 +/- 16.85 ms vs 121.77 +/- 11.27 ms, p < 0.001); Non filtered atrial duration (0-300 Hz) was not different between the two groups, A and B (118.54 +/- 10.96 ms vs 123.53 +/- 18.77 ms, p = NS); The prevalence of late atrial potentials was higher in group B than in group A (60.8% vs 7.1%, p < 0.001); No relation was observed between high resolution atriogram data and echocardiographic measurements; Sensibility was 82%, specificity 81%, and predictivity 60%. CONCLUSIONS: Data from our study show that high resolution electrocardiography is a valid tool for identifying patients prone to atrial fibrillation. Such patients can be identified by the presence of "late atrial potentials" that, like late ventricular potentials for ventricular tachycardia, are correlated with atrial fibrillation. Nevertheless, a larger cohort of patients is necessary to confirm these results.

Aged↗