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Flavia Ravelli

Bio: Flavia Ravelli is an academic researcher from University of Trento. The author has contributed to research in topics: Atrial fibrillation & Atrial flutter. The author has an hindex of 27, co-authored 106 publications receiving 2541 citations. Previous affiliations of Flavia Ravelli include University of Bologna & Maastricht University.


Papers
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TL;DR: Increased atrial pressure in the isolated rabbit heart resulted in a significant increase in vulnerability to AF that was closely correlated to shortening of the AERP and no correlation was found with the spatial dispersion between right and left AERPs.
Abstract: Background Atrial fibrillation (AF) is frequently observed under conditions that are associated with atrial dilatation. The aim of this study was to investigate the effects of atrial dilatation on the substrate of AF. Methods and Results In 15 Langendorff-perfused rabbit hearts, the interatrial septum was perforated, and after occlusion of the caval and pulmonary veins, biatrial pressure was increased by raising the level of an outflow cannula in the pulmonary artery. Right and left atrial effective refractory periods (AERPs), monophasic action potentials (MAPs), and inducibility of AF by single premature stimuli were measured as a function of atrial pressure. Increasing the atrial pressure from 0.5±0.7 to 16.2±2.2 cm H2O resulted in a progressive shortening of the right AERP from 82.2±9.8 to 48.0±5.1 ms. In the left atrium, an increase in pressure up to 7.4±0.3 cm H2O had no effect on the AERP. At higher pressures, however, the left AERP also shortened, from 67.5±7.5 to 49.3±2.0 ms. The duration of MAPs ...

458 citations

Journal ArticleDOI
TL;DR: LGE is a powerful predictor of ventricular arrhythmic risk in patients with ventricular dysfunction, irrespective of ICM and NICM etiology, which suggests its potential to improve patient selection for ICD implantation.
Abstract: Objectives The authors performed a meta-analysis to evaluate the predictive value of late gadolinium enhancement (LGE) cardiac magnetic resonance for ventricular tachyarrhythmia in ischemic cardiomyopathy (ICM) and nonischemic cardiomyopathy (NICM) patients with ventricular dysfunction. Background The use of LGE to detect myocardial fibrosis and its related arrhythmic substrate is well established. Several recent studies have described the predictive value of LGE for ventricular tachyarrhythmias; however, their validity is limited by small sample size and low number of events. Methods MEDLINE and the Cochrane Library electronic databases were systematically searched to identify studies that applied LGE in ICM and NICM patients with ventricular dysfunction and reported arrhythmic clinical outcomes (sudden death, aborted sudden death, ventricular tachycardia, ventricular fibrillation, and appropriate implantable cardioverter-defibrillator [ICD] therapy, including antitachycardia pacing). A meta-analysis was performed to determine pooled odds ratios (ORs) for these arrhythmic events. Results Nineteen studies that evaluated 2,850 patients with 423 arrhythmic events over a mean/median follow-up of 2.8 years were identified. The composite arrhythmic endpoint was reached in 23.9% of patients with a positive LGE test (annualized event rate of 8.6%) versus 4.9% of patients with a negative LGE test (annualized event rate of 1.7%; p Conclusions LGE is a powerful predictor of ventricular arrhythmic risk in patients with ventricular dysfunction, irrespective of ICM and NICM etiology. The prognostic power of LGE is particularly strong in patients with severely depressed EF, which suggests its potential to improve patient selection for ICD implantation.

212 citations

Journal ArticleDOI
TL;DR: The analysis of the FF intervals demonstrates a strict correlation with atrial functional refractoriness, which is consistent with the presence of a gap of excitability during atrial fibrillation in the human atria.
Abstract: Background The aims of our study were to investigate the meaning of local atrial activation and its behavior during paroxysmal atrial fibrillation and to study the effect of overdrive pacing on local atrial activity. Methods and Results Twenty-five patients with lone paroxysmal atrial fibrillation underwent electrophysiological study. Functional and effective atrial refractoriness was determined. Mean and fifth percentile values of 100 consecutive atrial fibrillation intervals (FF) were evaluated at three atrial sites either at arrhythmia onset or at self-termination (or at minute 5). A high-voltage burst pacing was performed after 6 minutes of stable atrial fibrillation in 10 patients. Mean FF intervals were evaluated 5 seconds before and after atrial pacing. Forty-nine atrial fibrillation episodes were induced: 39 self-terminating within 5 minutes and 10 long-lasting. A significant correlation was found between mean FF and atrial functional refractory period (r=.73, P<.001) and between fifth percentile ...

178 citations

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TL;DR: The capability to detect transient instances of AF complexity and to map the local regularity over the atrial surface was addressed by the dynamic and multisite evaluation of /spl rho/, suggesting that the algorithm could improve the understanding of AF mechanisms and become useful for its clinical treatment.
Abstract: A new method for quantifying the organization of single bipolar electrograms recorded in the human atria during atrial fibrillation (AF) is presented. The algorithm relies on the comparison between pairs of local activation waves (LAWs) to estimate their morphological similarity, and returns a regularity index (/spl rho/) which measures the extent of repetitiveness over time of the detected activations. The database consisted of endocardial data from a multipolar basket catheter during AF and intraatrial recordings during atrial flutter. The index showed maximum regularity (/spl rho/=1) for all atrial flutter episodes and decreased significantly when increasing AF complexity as defined by Wells (type I: /spl rho/=0.75/spl plusmn/0.23; type II: /spl rho/=0.35/spl plusmn/0.11; type III: /spl rho/=0.15/spl plusmn/0.08; P<0.01). The ability to distinguish different AF episodes was assessed by designing a classification scheme based on a minimum distance analysis, obtaining an accuracy of 85.5%. The algorithm was able to discriminate among AF types even in presence of few depolarizations as no significant /spl rho/ changes were observed by reducing the signal length down to include five LAWs. Finally, the capability to detect transient instances of AF complexity and to map the local regularity over the atrial surface was addressed by the dynamic and multisite evaluation of /spl rho/, suggesting that our algorithm could improve the understanding of AF mechanisms and become useful for its clinical treatment.

133 citations

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TL;DR: 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.
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 (F...

127 citations


Cited by
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TL;DR: A robust single-lead electrocardiogram (ECG) delineation system based on the wavelet transform (WT), outperforming the results of other well known algorithms, especially in determining the end of T wave.
Abstract: In this paper, we developed and evaluated a robust single-lead electrocardiogram (ECG) delineation system based on the wavelet transform (WT). In a first step, QRS complexes are detected. Then, each QRS is delineated by detecting and identifying the peaks of the individual waves, as well as the complex onset and end. Finally, the determination of P and T wave peaks, onsets and ends is performed. We evaluated the algorithm on several manually annotated databases, such as MIT-BIH Arrhythmia, QT, European ST-T and CSE databases, developed for validation purposes. The QRS detector obtained a sensitivity of Se=99.66% and a positive predictivity of P+=99.56% over the first lead of the validation databases (more than 980,000 beats), while for the well-known MIT-BIH Arrhythmia Database, Se and P+ over 99.8% were attained. As for the delineation of the ECG waves, the mean and standard deviation of the differences between the automatic and manual annotations were computed. The mean error obtained with the WT approach was found not to exceed one sampling interval, while the standard deviations were around the accepted tolerances between expert physicians, outperforming the results of other well known algorithms, especially in determining the end of T wave.

1,490 citations

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TL;DR: A translational overview on the biological basis of atrial remodeling and the proarrhythmic mechanisms involved in the fibrillation process is given.
Abstract: Atrial fibrillation (AF) is an arrhythmia that can occur as the result of numerous different pathophysiological processes in the atria. Some aspects of the morphological and electrophysiological al...

1,051 citations

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TL;DR: Research into risk factors and genetics of stroke has not only identified those at risk for stroke but also identified ways to target at-risk populations for stroke prevention.
Abstract: Stroke is a heterogeneous syndrome, and determining risk factors and treatment depends on the specific pathogenesis of stroke. Risk factors for stroke can be categorized as modifiable and nonmodifiable. Age, sex, and race/ethnicity are nonmodifiable risk factors for both ischemic and hemorrhagic stroke, while hypertension, smoking, diet, and physical inactivity are among some of the more commonly reported modifiable risk factors. More recently described risk factors and triggers of stroke include inflammatory disorders, infection, pollution, and cardiac atrial disorders independent of atrial fibrillation. Single-gene disorders may cause rare, hereditary disorders for which stroke is a primary manifestation. Recent research also suggests that common and rare genetic polymorphisms can influence risk of more common causes of stroke, due to both other risk factors and specific stroke mechanisms, such as atrial fibrillation. Genetic factors, particularly those with environmental interactions, may be more modifiable than previously recognized. Stroke prevention has generally focused on modifiable risk factors. Lifestyle and behavioral modification, such as dietary changes or smoking cessation, not only reduces stroke risk, but also reduces the risk of other cardiovascular diseases. Other prevention strategies include identifying and treating medical conditions, such as hypertension and diabetes, that increase stroke risk. Recent research into risk factors and genetics of stroke has not only identified those at risk for stroke but also identified ways to target at-risk populations for stroke prevention.

845 citations

Journal ArticleDOI
TL;DR: Altered of miRNAs following exercise, their association with diseases, and therapeutic potential will be explained, and miRNA bioinformatics tools and conventional methods for miRNA detection and quantification will be discussed.
Abstract: MicroRNAs (miRNAs) are a class of small noncoding RNAs, which function in posttranscriptional regulation of gene expression. They are powerful regulators of various cellular activities including cell growth, differentiation, development, and apoptosis. They have been linked to many diseases, and currently miRNA-mediated clinical trial has shown promising results for treatment of cancer and viral infection. This review provides an overview and update on miRNAs biogenesis, regulation of miRNAs expression, their biological functions, and role of miRNAs in epigenetics and cell-cell communication. In addition, alteration of miRNAs following exercise, their association with diseases, and therapeutic potential will be explained. Finally, miRNA bioinformatics tools and conventional methods for miRNA detection and quantification will be discussed.

804 citations