Publications (28)88 Total impact
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Article: A fully-adaptive multiresolution algorithm for atrial arrhythmia simulation on anatomically-realistic unstructured meshes.
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ABSTRACT: Biophysically-detailed and anatomically-realistic atrial models are emerging as a valuable tool in the study of atrial arrhythmias, nevertheless clinical use of these models would be favored by a reduction of computational times. This paper introduces a novel adaptive mesh algorithm, based on multiresolution representation (MR), for the efficient integration of cardiac ODE-PDE systems on unstructured triangle meshes. The algorithm applies a dynamically-adapted node-centered FVM scheme for integration of diffusion. The method accuracy and efficiency were evaluated by simulating propagation scenarios of increasing complexity levels (pacing, stable spirals, atrial fibrillation) on tomography-derived 3D monolayer atrial models, based on a monodomain reaction-diffusion formulation coupled with the Courtemanche atrial ionic model. All simulated propagation patterns were accurately reproduced with substantially reduced computational times (10 - 30% of the fullresolution simulation time). The proposed algorithm, combining the MR computational efficiency with the geometrical flexibility of unstructured meshes, may favor the development of patientspecific multiscale models of atrial arrhythmias and their application in the clinical setting.IEEE transactions on bio-medical engineering 05/2013; · 2.15 Impact Factor -
Article: Autosomal Recessive Atrial Dilated Cardiomyopathy with Standstill Evolution Associated with Mutation of Natriuretic Peptide Precursor A.
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ABSTRACT: BACKGROUND: -Atrial dilatation and atrial standstill are etiologically heterogeneous phenotypes with poorly defined nosology. In 1983 we described 8-years follow-up of idiopathic atrial dilatation with standstill evolution in 8 patients from 3 families. We later identified 5 additional patients with identical phenotypes: 1 member of the largest original family and 4 unrelated to the 3 original families. All families are from a same geographic area in the North-East Italy. METHODS AND RESULTS: -We followed-up the 13 patients for up to 37 years, extended the clinical investigation and monitoring to living relatives and investigated the genetic basis of the disease. The disease was characterized by: 1) clinical onset in adulthood; 2) bi-atrial dilatation up to giant size; 3) early supraventricular arrhythmias with progressive loss of atrial electrical activity to atrial standstill; 4) thromboembolic complications; 5) stable, normal left ventricular function and NYHA functional class during the long-term course of the disease. By linkage analysis we mapped a locus at 1p36.22 containing the natriuretic precursor A (NPPA) gene. By sequencing NPPA we identified a homozygous missense mutation (p.Arg150Gln) in all living affected individuals of the 6 families. All patients showed low serum levels of Atrial Natriuretic Peptide (ANP). Heterozygous mutation carriers were healthy and demonstrated normal levels of ANP. CONCLUSIONS: -Autosomal recessive Atrial Dilated Cardiomyopathy is a rare disease associated with homozygous mutation of the NPPA gene and characterized by extreme atrial dilatation with standstill evolution, thromboembolic risk, preserved left ventricular function and severely decreased levels of ANP.Circulation Cardiovascular Genetics 12/2012; · 6.11 Impact Factor -
Article: Anatomic Localization of Rapid Repetitive Sources in Persistent Atrial Fibrillation: Fusion of Biatrial CT Images With Wave Similarity/Cycle Length Maps.
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ABSTRACT: The aim of this study was to investigate the anatomic distribution of critical sources in patients with atrial fibrillation (AF) by fusion of biatrial computed tomography (CT) images with cycle length (CL) and wave similarity (WS) maps. Experimental and clinical studies show that atrial fibrillation (AF) may originate from rapid and repetitive (RR) sources of activation. Localization of RR sources may be crucial for an effective ablation treatment. Atrial electrograms showing rapid and repetitive activations can be identified by combining WS and CL analysis. Patients with persistent AF underwent biatrial electroanatomic mapping and pre-procedural CT cardiac imaging. WS and CL maps were constructed in 17 patients by calculating the degree of repetitiveness of activation waveforms (similarity index [S]) and the cycle length at each atrial site. WS/CL maps were then integrated with biatrial 3-dimensional CT reconstructions by a stochastic approach. Repetitive sources of activation (S ≥0.5) were present in most patients with persistent AF (94%) and were mainly located at the pulmonary veins (82% of patients), at the superior caval vein (41%), on the anterior wall of the right atrium (23%), and at the left atrial appendage (23%). Potential driver sources showing both rapid and repetitive activations (CL = 140.7 ± 25.1 ms, S = 0.65 ± 0.15) were present only in a subset of patients (65%) and were confined to the pulmonary vein region (47% of patients) and left atrial appendage (12%). Differently, the repetitive activity of the superior caval vein was characterized by a slow activation rate (CL = 184.7 ± 14.6 ms). The identification and localization of RR sources is feasible by fusion of biatrial anatomic images with WS/CL maps. Potential driver sources are present only in a subset of patients with persistent AF and are mainly located in the pulmonary vein region.JACC. Cardiovascular imaging 12/2012; 5(12):1211-20. · 14.29 Impact Factor -
Article: Propagation pattern analysis during atrial fibrillation based on the adaptive group LASSO.
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ABSTRACT: The present study introduces sparse modeling for the estimation of propagation patterns in intracardiac atrial fibrillation (AF) signals. The estimation is based on the partial directed coherence (PDC) function, derived from fitting a multivariate autoregressive model to the observed signals. A sparse optimization method is proposed for estimation of the model parameters, namely, the adaptive group least absolute selection and shrinkage operator (aLASSO). In simulations aLASSO was found superior to the commonly used least-squares (LS) estimation with respect to estimation performance. The normalized error between the true and estimated model parameters dropped from 0.20 ± 0.04 for LS estimation to 0.03 ± 0.01 for aLASSO when the number of available data samples exceeded the number of model parameters by a factor of 5. The error reduction was more pronounced for short data segments. Propagation patterns were also studied on intracardiac AF data, the results showing that the identification of propagation patterns is substantially simplified by the sparsity assumption.Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:5535-8. -
Article: A novel approach to propagation pattern analysis in intracardiac atrial fibrillation signals.
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ABSTRACT: The purpose of this study is to investigate propagation patterns in intracardiac signals recorded during atrial fibrillation (AF) using an approach based on partial directed coherence (PDC), which evaluates directional coupling between multiple signals in the frequency domain. The PDC is evaluated at the dominant frequency of AF signals and tested for significance using a surrogate data procedure specifically designed to assess causality. For significantly coupled sites, the approach allows also to estimate the delay in propagation. The methods potential is illustrated with two simulation scenarios based on a detailed ionic model of the human atrial myocyte as well as with real data recordings, selected to present typical propagation mechanisms and recording situations in atrial tachyarrhythmias. In both simulation scenarios the significant PDCs correctly reflect the direction of coupling and thus the propagation between all recording sites. In the real data recordings, clear propagation patterns are identified which agree with previous clinical observations. Thus, the results illustrate the ability of the novel approach to identify propagation patterns from intracardiac signals during AF, which can provide important information about the underlying AF mechanisms, potentially improving the planning and outcome of arrhythmia ablation.Annals of biomedical engineering 01/2011; 39(1):310-23. · 2.41 Impact Factor -
Article: Acute atrial dilatation slows conduction and increases AF vulnerability in the human atrium.
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ABSTRACT: The mechanisms by which atrial stretch favors the development of a substrate for atrial fibrillation (AF) are not fully understood. In this study, the role of stretch-induced conduction changes in the creation of a proarrhythmic substrate has been investigated by quantifying the spatial distribution of local conduction velocities (CVs) in the human atrium during acute atrial dilatation. Electroanatomic mapping of right atrial activation was performed in 10 patients during coronary sinus pacing under control condition and during acute atrial dilatation. Atrial stretch was obtained by simultaneous atrioventricular (AV) pacing at a cycle length of 450-500 ms. Local CVs were accurately estimated by applying the principle of triangulation and spatially mapped over the whole right atrial endocardial surface. Simultaneous AV pacing significantly increased right atrial volume from 72.0 ± 29.0 to 86.3 ± 31.3 mL (P < 0.001). The 23% increase in atrial volume resulted in an overall decrease in atrial CV from 65.8 ± 5.9 to 55.2 ± 7.2 cm/s (P < 0.001) and an increased incidence of slow conduction sites or local conduction blocks from 10.3 ± 4.2% to 15.9 ± 7.7% (P < 0.01). Acute atrial dilatation concurrently increased AF vulnerability, with 6 of 10 patients developing AF episodes under stretch condition. Quantification of stretch-induced conduction changes in the human atrium is feasible by combining simultaneous AV pacing and CV map construction. Acute atrial dilatation results in conduction slowing and significant increase in AF vulnerability, suggesting the role of stretch-induced conduction disturbances in the creation of a substrate for AF.Journal of Cardiovascular Electrophysiology 11/2010; 22(4):394-401. · 3.06 Impact Factor -
Chapter: Mechanical Modulation of a Reentrant Arrhythmia: The Atrial Flutter Case
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ABSTRACT: Atrial flutter (AFL) is a supraventricular arrhythmia, based on a reentrant mechanism, which presents small fluctuations in cycle length. We report on studies in humans and animals which disclosed the nature of these variations and supported their mechanical origin. The sources of the spontaneous variability of atrial flutter cycle length have been identified in ventricular contraction and respiration, which cause phasic variations in atrial interval. The phase-response curves have been shown to be closely related to atrial volume changes during ventricular and respiratory activities and oscillations in cycle length have been reported to be independent of autonomic tone. All this evidence has led to the formulation of the mechano-electrical feedback (MEF) paradigm, which suggests that changes in atrial volume directly affect atrial flutter cycle length variability via direct alteration of the reentrant circuit size and mechano-electrical modulation of conduction velocity. Theoretical predictions of experimental variability patterns by a closed-loop mathematical model of AFL variability, including a MEF branch, provided additional evidence in favour of a mechanically-mediated mechanism at the basis of atrial flutter cycle length variability. KeywordsAtrial flutter-Cycle length variability-Mechano-electrical feedback-Reentry-Mathematical modelling12/2009: pages 301-325; -
Article: Cardiorespiratory interactions in patients with atrial flutter.
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ABSTRACT: Respiratory sinus arrhythmia (RSA) is generally known as the autonomically mediated modulation of the sinus node pacemaker frequency in synchrony with respiration. Cardiorespiratory interactions have been largely investigated during sinus rhythm, whereas little is known about interactions during reentrant arrhythmias. In this study, cardiorespiratory interactions at the atrial and ventricular level were investigated during atrial flutter (AFL), a supraventricular arrhythmia based on a reentry, by using cross-spectral analysis and computer modeling. The coherence and phase between respiration and atrial (gamma(AA)(2), phi(AA)) and ventricular (gamma(RR)(2), phi(RR)) interval series were estimated in 20 patients with typical AFL (68.0 +/- 8.8 yr) and some degree of atrioventricular (AV) conduction block. In all patients, atrial intervals displayed oscillations strongly coupled and in phase with respiration (gamma(AA)(2)= 0.97 +/- 0.05, phi(AA) = 0.71 +/- 0.31 rad), corresponding to a paradoxical lengthening of intervals during inspiration. The modulation pattern was frequency independent, with in-phase oscillations and short time delays (0.40 +/- 0.15 s) for respiratory frequencies in the range 0.1-0.4 Hz. Ventricular patterns were affected by AV conduction type. In patients with fixed AV conduction, ventricular intervals displayed oscillations strongly coupled (gamma(RR)(2)= 0.97 +/- 0.03) and in phase with respiration (phi(RR) = 1.08 +/- 0.80 rad). Differently, in patients with variable AV conduction, respiratory oscillations were secondary to Wencheback rhythmicity, resulting in a decreased level of coupling (gamma(RR)(2)= 0.50 +/- 0.21). Simulations with a simplified model of AV conduction showed ventricular patterns to originate from the combination of a respiratory modulated atrial input with the functional properties of the AV node. The paradoxical frequency-independent modulation pattern of atrial interval, the short time delays, and the complexity of ventricular rhythm characterize respiratory arrhythmia during AFL and distinguish it from normal RSA. These peculiar features can be explained by assuming a direct mechanical action of respiration on AFL reentrant circuit.Journal of Applied Physiology 12/2008; 106(1):29-39. · 3.75 Impact Factor -
Article: An automatic system for the analysis and classification of human atrial fibrillation patterns from intracardiac electrograms.
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ABSTRACT: This paper presents an automatic system for the analysis and classification of atrial fibrillation (AF) patterns from bipolar intracardiac signals. The system is made up of: 1) a feature-extraction module that defines and extracts a set of measures potentially useful for characterizing AF types on the basis of their degree of organization; 2) a feature-selection module (based on the Jeffries-Matusita distance and a branch and bound search algorithm) identifying the best subset of features for discriminating different AF types; and 3) a support vector machine technique-based classification module that automatically discriminates the AF types according to the Wells' criteria. The automatic system was applied on 100 intracardiac AF signal strips and on a selection of 11 representative features, demonstrating: a) the possibility to properly identify the most significant features for the discrimination of AF types; b) higher accuracy (97.7% using the seven most informative features) than the traditional maximum likelihood classifier; and c) effectiveness in AF classification also with few training samples (accuracy = 88.3% with only five training signals). Finally, the system identifies a combination of indices characterizing changes of morphology of atrial activation waves and perturbation of the isoelectric line as the most effective in separating the AF types.IEEE transactions on bio-medical engineering 10/2008; 55(9):2275-85. · 2.15 Impact Factor -
Article: A model for mechano-electrical feedback effects on atrial flutter interval variability.
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ABSTRACT: Atrial flutter is a supraventricular arrhythmia, based on a reentrant mechanism mainly confined to the right atrium. Although atrial flutter is considered a regular rhythm, the atrial flutter interval (i.e., the time interval between consecutive atrial activation times) presents a spontaneous beat-to-beat variability, which has been suggested to be related to ventricular contraction and respiration by mechano-electrical feedback. This paper introduces a model to predict atrial activity during atrial flutter, based on the assumption that atrial flutter variability is related to the phase of the reentrant activity in the ventricular and respiratory cycles. Thus, atrial intervals are given as a superimposition of phase-dependent ventricular and respiratory modulations. The model includes a simplified atrioventricular (AV) branch with constant refractoriness and conduction times, which allows the prediction of ventricular activations in a closed-loop with atrial activations. Model predictions are quantitatively compared with real activation series recorded in 12 patients with atrial flutter. The model predicts the time course of both atrial and ventricular time series with a high beat-to-beat agreement, reproducing 96+/-8% and 86+/-21% of atrial and ventricular variability, respectively. The model also predicts the existence of phase-locking of atrial flutter intervals during periodic ventricular pacing and such results are observed in patients. These results constitute evidence in favor of mechano-electrical feedback as a major source of cycle length variability during atrial flutter.Bulletin of Mathematical Biology 08/2008; 70(5):1326-47. · 1.85 Impact Factor -
Article: Image fusion shows the role of incomplete ablation lines in creating a substrate for left atrial flutter occurring after atrial fibrillation ablation.
Heart Rhythm 02/2008; 5(1):163-4. · 4.10 Impact Factor -
Article: Isolation of the left atrial surface from cardiac multi-detector CT images based on marker controlled watershed segmentation.
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ABSTRACT: The delineation of left atrium (LA) and pulmonary veins (PVs) anatomy from high resolution images holds importance for atrial fibrillation (AF) investigation and treatment. In this study, a semiautomatic segmentation procedure for LA and PVs inner surface from contrast enhanced CT data was developed. The procedure consists of a three dimensional marker controlled watershed segmentation applied to the external morphological gradient, followed by variable threshold surface extraction from the original intensity image. A preliminary anisotropic non-linear filtering was implemented to improve the S/N ratio of CT images. The performance of segmentation was evaluated on cardiac CT scans of 12 AF patients both qualitatively and quantitatively. The qualitative evaluation by expert radiologist assessed the segmentation as overall successful in all patients and capable of extracting both the LA body and the connected vascular trees. The quantitative validation, by computing discrepancy measures with respect to a manually segmented gold standard, indicated an average of about 90% of voxels correctly classified and an average border mismatch lower than 1.5 voxels (1.2 mm). The accurate extraction of the inner LA-PVs walls provided by this method, along with the minimal required human intervention, should facilitate the use of anatomical atrial models for the non-pharmacological treatment of AF.Medical Engineering & Physics 01/2008; 30(1):48-58. · 1.62 Impact Factor -
Article: A stochastic approach for automatic registration and fusion of left atrial electroanatomic maps with 3D CT anatomical images.
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ABSTRACT: The integration of electroanatomic maps with highly resolved computed tomography cardiac images plays an important role in the successful planning of the ablation procedure of arrhythmias. In this paper, we present and validate a fully-automated strategy for the registration and fusion of sparse, atrial endocardial electroanatomic maps (CARTO maps) with detailed left atrial (LA) anatomical reconstructions segmented from a pre-procedural MDCT scan. Registration is accomplished by a parameterized geometric transformation of the CARTO points and by a stochastic search of the best parameter set which minimizes the misalignment between transformed CARTO points and the LA surface. The subsequent fusion of electrophysiological information on the registered CT atrium is obtained through radial basis function interpolation. The algorithm is validated by simulation and by real data from 14 patients referred to CT imaging prior to the ablation procedure. Results are presented, which show the validity of the algorithmic scheme as well as the accuracy and reproducibility of the integration process. The obtained results encourage the application of the integration method in post-intervention ablation assessment and basic AF research and suggest the development for real-time applications in catheter guiding during ablation intervention.Physics in Medicine and Biology 11/2007; 52(20):6323-37. · 2.83 Impact Factor -
Article: Small-sample characterization of stochastic approximation staircases in forced-choice adaptive threshold estimation.
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ABSTRACT: Despite the widespread use of up-down staircases in adaptive threshold estimation, their efficiency and usability in forced-choice experiments has been recently debated. In this study, simulation techniques were used to determine the small-sample convergence properties of stochastic approximation (SA) staircases as a function of several experimental parameters. We found that satisfying some general requirements (use of the accelerated SA algorithm, clear suprathreshold initial stimulus intensity, large initial step size) the convergence was accurate independently of the spread of the underlying psychometric function. SA staircases were also reliable for targeting percent-correct levels far from the midpoint of the psychometric function and performed better than classical up-down staircases with fixed step size. These results prompt the utilization of SA staircases in practical forced-choice estimation of sensory thresholds.Perception & Psychophysics 03/2007; 69(2):254-62. · 1.37 Impact Factor -
Article: Deterioration of organization in the first minutes of atrial fibrillation: a beat-to-beat analysis of cycle length and wave similarity.
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ABSTRACT: It has been recently suggested that many episodes of atrial fibrillation (AF) may be partially organized at the onset and thus more suitable for antitachycardia pacing therapy. Nevertheless, the time course of organization in the first minutes of AF has not been quantified yet. Twenty episodes of paroxysmal AF were studied. Electrograms were recorded from the right atrium (RA), distal (CSd), and proximal coronary sinus (CSp). The time course of AF cycle length (AFCL) and the regularity of wave morphology (similarity index S) were beat-to-beat measured at each recording site during the first 7 minutes of AF. AFCL and S showed a decreasing trend after the onset of AF. AFCL decreased from 208 +/- 31 to 171 +/- 21 msec (P < 0.001), from 206 +/- 40 to 169 +/- 23 msec (P < 0.001) and from 190 +/- 42 to 152 +/- 18 msec (P < 0.05), respectively, in RA, CSd, and CSp. Similarly, the similarity index decreased in CSd from 0.37 +/- 0.27 to 0.12 +/- 0.09 (P < 0.01) and in RA from 0.40 +/- 0.18 to 0.17 +/- 0.16 (P < 0.001). The 80% of the decrease occurred during the first 3 minutes of the arrhythmia, while after this time both cycle length and similarity index did not change significantly anymore. Conversely, the electrical activity in CSp was highly disorganized (S = 0.05 +/- 0.03) even in the first minute of AF, and no decreasing temporal trend was observed. Higher levels of organization and longer fibrillation intervals exist at the onset of AF. The degree of organization of the electrical activity decays within less than 3 minutes. Since antitachycardia pacing success rate increases with high levels of organization, these results suggest an early delivery of pacing treatment.Journal of Cardiovascular Electrophysiology 02/2007; 18(1):60-5. · 3.06 Impact Factor -
Article: Enormous bi-atrial enlargement in a persistent idiopathic atrial standstill.
European Heart Journal 12/2005; 26(21):2276. · 10.48 Impact Factor -
Article: Quantification of synchronization during atrial fibrillation by Shannon entropy: validation in patients and computer model of atrial arrhythmias.
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ABSTRACT: Atrial fibrillation (AF), a cardiac arrhythmia classically described as completely desynchronized, is now known to show a certain amount of synchronized electrical activity. In the present work a new method for quantifying the level of synchronization of the electrical activity recorded in pairs of atrial sites during atrial fibrillation is presented. A synchronization index (Sy) was defined by quantifying the degree of complexity of the distribution of the time delays between sites by Shannon entropy estimation. The capability of Sy to discriminate different AF types in patients was assessed on a database of 60 pairs of endocardial recordings from a multipolar basket catheter. The analysis showed a progressive and significant decrease of Sy with increasing AF complexity classes as defined by Wells (AF type I Sy = 0.73 +/- 0.07, type II Sy = 0.56 +/- 0.07, type III Sy = 0.36 +/- 0.04, p < 0.001). The extension of Sy calculation to the whole right atrium showed the existence of spatial heterogeneities in the synchronization level. Moreover, experiments simulated by a computer model of atrial arrhythmias showed that propagation patterns with different complexity could be the basis of different synchronization levels found in patients. In conclusion the quantification of synchronization by Shannon entropy estimation of time delay dispersion may facilitate the identification of different propagation patterns associated with AF, thus enhancing our understanding of AF mechanisms and helping in its treatment.Physiological Measurement 12/2005; 26(6):911-23. · 1.68 Impact Factor -
Article: Wave similarity mapping shows the spatiotemporal distribution of fibrillatory wave complexity in the human right atrium during paroxysmal and chronic atrial fibrillation.
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ABSTRACT: The complexity of waveforms during atrial fibrillation may reflect critical activation patterns for the arrhythmia perpetuation. In this study, we introduce a novel concept of map, based on the analysis of the wave morphology, which gives a direct evidence in the human right atrium on the spatiotemporal distribution of fibrillatory wave complexity in paroxysmal (PAF) and chronic (CAF) atrial fibrillation. Electrograms were recorded from a 64-electrode catheter in the right atrium of 15 patients during PAF (n = 8) and CAF (n = 7). Wave similarity maps were constructed by calculating the degree of morphological similarity of activation waves (S) at each atrial site and by following its temporal evolution. During PAF the spatiotemporal distribution of the waveforms was highly consistent across the subjects and was determined by the anatomic location. Wave similarity maps showed the existence of an extended area with low similarity index, which covered the low posteroseptal atrium (S = 0.28 +/- 0.09) and the septal region (S = 0.22 +/- 0.04), and the presence of a large tongue with high similarity index, which penetrated the lateral wall (S = 0.55 +/- 0.08) starting from the high anterolateral atrium (S = 0.54 +/- 0.06). A completely different spatiotemporal pattern was seen during CAF. No distinct regions with different similarity indexes were recognized, but a uniformly distributed low similarity index (S = 0.27 +/- 0.07) was found. The spatial pattern was highly stable in time with fluctuations of S < 0.04. Quantification of the spatiotemporal distribution of fibrillatory wave complexity is feasible in humans by wave similarity mapping. Anatomic anchoring of waveforms during PAF and pattern destruction during CAF was determined.Journal of Cardiovascular Electrophysiology 10/2005; 16(10):1071-6. · 3.06 Impact Factor -
Article: Exploring directionality in spontaneous heart period and systolic pressure variability interactions in humans: implications in the evaluation of baroreflex gain.
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ABSTRACT: Although in physiological conditions RR interval and systolic arterial pressure (SAP) are likely to interact in a closed loop, the traditional cross-spectral analysis cannot distinguish feedback (FB) from feedforward (FF) influences. In this study, a causal approach was applied for calculating the coherence from SAP to RR (K(s-r)) and from RR to SAP (K(r-s)) and the gain and phase of the baroreflex transfer function. The method was applied, compared with the noncausal one, to RR and SAP series taken from 15 healthy young subjects in the supine position and after passive head-up tilt. For the low frequency (0.04-0.15 Hz) spectral component, the enhanced FF coupling (K(r-s) = 0.59 +/- 0.21, significant in 14 subjects) and the blunted FB coupling (K(s-r) = 0.17 +/- 0.17, significant in 4 subjects) found at rest indicated the prevalence of nonbaroreflex mechanisms. The tilt maneuver recovered FB influences (K(s-r) = 0.47 +/- 0.16, significant in 14 subjects), which were stronger than FF interactions (K(s-r) = 0.34 +/- 0.19, significant in 9 subjects). At the respiratory frequency, the RR-SAP regulation was balanced at rest (K(s-r) = 0.30 +/- 0.18 and K(r-s) = 0.29 +/- 0.20, significant in 11 and 8 subjects) and shifted toward FB mechanisms after tilt (K(s-r) = 0.35 +/- 0.19 and K(r-s) = 0.19 +/- 0.11, significant in 14 and 8 subjects). The causal baroreflex gain estimates were always lower than the corresponding noncausal values and decreased significantly from rest to tilt in both frequency bands. The tilt-induced increase of the phase lag from SAP to RR suggested a shift from vagal to sympathetic modulation. Thus the importance of nonbaroreflex interactions pointed out the necessity of accounting for causality in the cross-spectral analysis of the interactions between cardiovascular variables in healthy humans.AJP Heart and Circulatory Physiology 05/2005; 288(4):H1777-85. · 3.71 Impact Factor -
Chapter: Mechano-Electric Feedback and Atrial Arrhythmias
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ABSTRACT: Numerous clinical evidences as well as experimental studies show an increased vulnerability to atrial arrhythmias by acute stretch of the atrial walls. However, the mechanism by which atrial dilatation favours the development of sustained atrial tachyarrhythmias, such as atrial fibrillation (AF), is not fully understood. The effects of acute atrial dilatation on the substrate of atrial fibrillation were investigated in Langendorff-perfused rabbit heart. Increased atrial pressure resulted in a significant increase in vulnerability to AF, while release of the atrial stretch resulted in prompt cardioversion of AF. Atrial stretch has been shown to modulate the atrial vulnerable parameters. Stretch-induced shortening in atrial refractoriness and impairment of atrial conduction have been demonstrated. Atrial stretch through the modulation of the electrophysiological properties may not only favour the onset of arrhythmias but may also modulate the rate of reentrant arrhythmias. Cyclic variations in atrial volume following ventricular contraction modulate the atrial flutter cycle length and account for the spontaneous variability of the arrhythmia.01/2005; , ISBN: 5769525908
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2005–2012
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Università degli Studi di Trento
- Department of Physics
Trento, Trentino-Alto Adige, Italy
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