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Background: Scientific research on atrial fibrosis in atrial fibrillation (AF) has mainly focused on quantitative or molecular features. The purpose of this study was to perform a clinicoarchitectural/structural investigation of fibrosis to provide one key to understanding the electrophysiological/clinical aspects of AF. Methods: We characterized the fibrosis (amount, architecture, cellular components, and ultrastructure) in left atrial biopsies from 121 patients with persistent/long-lasting persistent AF (group 1; 59 males; 60±11 years; 91 mitral disease–related AF, 30 nonmitral disease–related AF) and from 39 patients in sinus rhythm with mitral valve regurgitation (group 2; 32 males; 59±12 years). Ten autopsy hearts served as controls. Results: Qualitatively, the fibrosis exhibited the same characteristics in all cases and displayed particular architectural scenarios (which we arbitrarily subdivided into 4 stages) ranging from isolated foci to confluent sclerotic areas. The percentage of fibrosis was larger and at a more advanced stage in group 1 versus group 2 and, within group 1, in patients with rheumatic disease versus nonrheumatic cases. In patients with AF with mitral disease and no rheumatic disease, the percentage of fibrosis and the fibrosis stages correlated with both left atrial volume index and AF duration. The fibrotic areas mainly consisted of type I collagen with only a minor cellular component (especially fibroblasts/myofibroblasts; average value range 69–150 cells/mm 2 , depending on the areas in AF biopsies). A few fibrocytes—circulating and bone marrow-derived mesenchymal cells—were also detectable. The fibrosis-entrapped cardiomyocytes showed sarcolemmal damage and connexin 43 redistribution/internalization. Conclusions: Atrial fibrosis is an evolving and inhomogeneous histological/architectural change that progresses through different stages ranging from isolated foci to confluent sclerotic zones which—seemingly—constrain impulse conduction across restricted regions of electrotonically coupled cardiomyocytes. The fibrotic areas mainly consist of type I collagen extracellular matrix and, only to a lesser extent, mesenchymal cells.

Compressed sensing (CS) is often applied at the digital level. We consider the case where CS follows a $\Delta \Sigma$ data converter and we show that CS can be practiced directly on the $\Delta \Sigma$ stream. In the proposed scheme, an appropriate sensing matrix incorporates the ability to get rid of the quantization noise from the $\Delta \Sigma$ modulator. We also show that a suitable sparsity basis enables the CS information recovery to be practiced directly at the Nyquist rate and that decimation, which is typically inherent in $\Delta \Sigma$ data acquisition, is not needed. Furthermore, the low depth of $\Delta \Sigma$ streams allows CS measures to be taken without multipliers, streamlining arithmetic blocks. A test case based on electrocardiograms is used to validate the approach.

Strategies for the adaptation of $\Delta \!\Sigma $ modulators ( $\Delta \!\Sigma $ Ms) to the embedding environment with respect to the ability of the latter to remove quantization noise have recently been introduced. They rely on formal optimization techniques to deliver finely tuned values for the coefficients of the $\Delta \!\Sigma \text{M}$ internal filters. However, in digital $\Delta \!\Sigma $ Ms, coefficients will necessarily be quantized to short wordlengths, the shorter the better, cost-wise. Unfortunately, this can severely hinder optimality. In this brief, a strategy is proposed to re-use the very optimization framework to minimize the effects of coefficient quantization. The technique is discussed by a practical design example based on a $\Delta \!\Sigma \text{M}$ for a wideband fractional- ${N}$ phase locked loop (PLL).

Inherited cardiac diseases inducing structural remodeling of the myocardium sometimes develop arrhythmias of various kinds. Among these rhythm disturbances, atrial fibrillation is well known to frequently worsen the prognosis of the primary disorder by increasing morbidity and mortality, especially because of a higher rate of heart failure. In this manuscript, we have reviewed the literature on the most important inherited structural cardiac diseases in whose clinical history atrial fibrillation may occur fairly often.

We follow up with recent proposals of using inductors working in weak and deep-saturation region to improve the features of switching mode power supplies. To this aim, we use a constant on-time (COT) converter including a saturable inductor as a test vehicle. The inductor model takes into account both hysteresis and dependence on the working temperature of the core and windings. The digital controller of the COT converter is considered too. Electro-thermal simulations are performed to analyse the performances of the overall analog mixed-signal circuit. It is shown that using a proper saturable inductor positively impacts on the design of the converter by mitigating its main drawback of having a working frequency largely dependent on the load conditions and input supply voltage. Some weak points of proposed design are also identified.

The effect of the quantization noise introduced by $\Delta \Sigma $ modulators in fractional- $N$ phase locked loop is studied in the time domain through a variational model of the corresponding analog mixed signal circuits. The latter can be interpreted as hybrid dynamical systems involving discontinuity boundaries and switching in the vector field. Discontinuity mapping is used to define an accurate high order model to propagate perturbations at discontinuity boundaries. This novel approach is more efficient than computing power spectral density of large-signal waveforms from long lasting time domain simulations. Furthermore, with respect to established macro-modeling techniques, it provides a better understanding of how electric elements influence the noise performance. The inherent features of the circuit components turn out to be directly embedded both in the system fundamental matrix and in the discontinuity mapping involved in its dynamical evolution. The validity of the approach is verified through numerical simulations.

Digital ΔΣ modulators can be conveniently implemented as multi-stage noise shaping (MASH) architectures whenever some power of the first-difference differentiator is acceptable as the noise transfer function (NTF). Yet, other types of NTF can be more performant in some applications. In fact, strategies for a full adaptation of the NTF to the modulator environment have recently been studied. In this work, the possibility of implementing such optimized NTFs with MASH setups is considered. Although stability cannot be guaranteed as in conventional MASH designs, splitting the modulator in stages can still provide advantages. The case of fractional frequency synthesizers is taken as an example. Through the discussion, an empirical invariant on the overall number of output levels required for stable operation is identified.

The inadequate long-term efficacy of anti-arrhythmic therapy has been one of the main reasons for the development of non-pharmacological interventions for patients with atrial fibrillation such as catheter and surgical ablation. This has greatly increased interest in the functional morphology and electrophysiological properties of the atria and related anatomical structures. This article is the second of a two-part review that aims to provide anatomical and functional details concerning some of the principal anatomical sites commonly targeted by ablative procedures for treating atrial fibrillation, and covers pulmonary veins, ganglionated plexi, caval veins, and the ligament of Marshall. It also provides some general information about site-specific ablation procedures.

Minimally invasive atrial fibrillation surgery (MIAFS) has become a well established and increasingly used option for managing patients with stand-alone arrhythmia. Pulmonary veins (PVs) isolation continues to be the cornerstone of ablation strategies. Indeed, in most cases, atrial fibrillation (AF) is triggered in or near the PVs. Nevertheless, ectopic beats initiating AF may occasionally arise from non-PV foci. The knowledge of the anatomy and underlying morphology of PVs and non-PV foci is essential for cardiac surgeons treating AF patients with epicardial minimally invasive procedures. The anatomical structures relevant to the pathogenesis and the epicardial treatment of AF include the PVs, the pericardial space, the pericardial sinuses, the phrenic nerve, the left atrium, the retro-atrial and caval ganglionated plexuses, the ligament of Marshall, the caval veins and the left atrial appendage. In this review, we briefly describe the basic anatomy of these structures and discuss their specific correlations for cardiac surgeons interested in performing MIAFS.

Single high-intensity premature stimuli when applied to the ventricles during ventricular drive of an ectopic site, as in Winfree's “pinwheel experiment,” usually induce reentry arrhythmias in the normal heart, while single low-intensity stimuli barely do. Yet ventricular arrhythmia vulnerability during normal sinus rhythm remains largely unexplored. With a view to define the role of anisotropy on ventricular vulnerability to unidirectional conduction block and reentry, we revisited the pinwheel experiment with reduced constraints in the in situ rat heart. New features included single premature stimulation during normal sinus rhythm, stimulation and unipolar potential mapping from the same high-resolution epicardial electrode array, and progressive increase in stimulation strength and prematurity from diastolic threshold until arrhythmia induction. Measurements were performed with 1-ms cathodal stimuli at multiple test sites ( n = 26) in seven rats. Stimulus-induced virtual electrode polarization during sinus beat recovery phase influenced premature ventricular responses. Specifically, gradual increase in stimulus strength and prematurity progressively induced make, break, and graded-response stimulation mechanisms. Hence unidirectional conduction block occurred as follows: 1) along fiber direction, on right and left ventricular free walls ( n = 23), initiating figure-eight reentry ( n = 17) and tachycardia ( n = 12), and 2) across fiber direction, on lower interventricular septum ( n = 3), initiating spiral wave reentry ( n = 2) and tachycardia ( n = 1). Critical time window (55.1 ± 4.7 ms, 68.2 ± 6.0 ms) and stimulus strength lower limit (4.9 ± 0.6 mA) defined vulnerability to reentry. A novel finding of this study was that ventricular tachycardia evolves and is maintained by episodes of scroll-like wave and focal activation couplets. We also found that single low-intensity premature stimuli can induce repetitive ventricular response ( n = 13) characterized by focal activations. NEW & NOTEWORTHY We performed ventricular cathodal point stimulation during sinus rhythm by progressively increasing stimulus strength and prematurity. Virtual electrode polarization and recovery gradient progressively induced make, break, and graded-response stimulation mechanisms. Unidirectional conduction block occurred along or across fiber direction, initiating figure-eight or spiral wave reentry, respectively, and tachycardia sustained by scroll wave and focal activations.

Modern cryptographic protocols require good entropy sources. Unfortunately, many networked devices lack subsystems dedicated to this task, being potentially susceptible to random number generator (RNG) attacks. Yet, most of these systems allow software upgrades and host communication ports, providing the option of a retrofit. This work illustrates how chaotic dynamics can be used to design a sub-10$ entropy source capable of an over 48kbit/s rate and offering multiple serial communication abilities. Operation is based on a standard microcontroller and exploits a loop built around one of its analog to digital converters (ADCs). The design offers self-testing features and enables an experimental validation of some recent results on the choice of the best state quantization function to employ when using chaotic maps as RNGs.

Resonate and Fire (R+F) models were introduced to account for many phenomena occurring in biological neurons showing sub-threshold oscillations of the membrane potential. In information technology, they are at the basis of Chaotic Spiking Oscillators (CSOs), exploitable in Pulse Coupled Neural Networks (PCNNs). This paper illustrates how the R + F paradigm can also be used for the testing of analog signal processing structures (and specifically filters), extending the Oscillation Based Test (OBT) framework. The rich dynamics of the R + F model is used to encode the block under test features and faults into pulse trains directly processable at the digital level. Means to achieve a precise characterization of firing times are provided and used for parametric testing. Considerations about the trade-off between testing times and accuracy are provided together with a practical example and simulation data. Copyright © 2012 John Wiley & Sons, Ltd.

We show that ΔΣ modulators can be interpreted as heuristic solvers for a particular class of optimization problems. Then, we exploit this theoretical result to propose a novel technique to deal with very large unconstrained discrete quadratic programming (UDQP) problems characterized by quadratic forms entailing a circulant matrix. The result is a circuit-based optimization approach involving a recast of the original problem into signal processing specifications, then tackled by the systematic design of an electronic system. This is reminiscent of analog computing, where untreatable differential equations were solved by designing electronic circuits analog to them. The approach can return high quality suboptimal solutions even when many hundreds of variables are considered and proved faster than conventional empirical optimization techniques. Detailed examples taken from two different domains illustrate that the range of manageable problems is large enough to cover practical applications.

Pulse compression is often practiced in ultrasound Non Destructive Testing (NDT) systems using chirps. However, chirps are inadequate for setups where multiple probes need to operate concurrently in Multiple Input Multiple Output (MIMO) arrangements. Conversely, many coded excitation systems designed for MIMO miss some chirp advantages (constant envelope excitation, easiness of bandwidth control, etc.) and may not be easily implemented on hardware originally conceived for chirp excitations. Here, we propose a system based on random-FM excitations, capable of enabling MIMO with minimal changes with respect to a chirp-based setup. Following recent results, we show that random-FM excitations retain many advantages of chirps and provide the ability to frequency-shape the excitations matching the transducers features., 4 pages, 4 figures. Post-print from conference proceedings. Note that paper in conference proceedings at http://dx.doi.org/10.1109/ULTSYM.2012.0117 has some rendering issues

Various techniques to generate pseudo-orthogonal excitations for Ultrasonic Non Destructive Testing (UT-NDT) are discussed, with the constraint that they deliver constant-envelope waveforms and they are FM based. Pseudo-orthogonal excitations enable multiple Tx probes to be operated simultaneously so that many measurements can be taken at once. The constraints assure minimal disruption of conventional hardware arrangements and guarantee a good exploitation of the power conversion abilities of the Tx probes. The goal is to seek a progressive management of the trade-ofl' between contrasting merit factors.

The Noise Transfer Function (NTF) of {\Delta}{\Sigma} modulators is typically designed after the features of the input signal. We suggest that in many applications, and notably those involving D/D and D/A conversion or actuation, the NTF should instead be shaped after the properties of the output/reconstruction filter. To this aim, we propose a framework for optimal design based on the Kalman-Yakubovich-Popov (KYP) lemma and semi-definite programming. Some examples illustrate how in practical cases the proposed strategy can outperform more standard approaches., Comment: 14 pages, 18 figures, journal. Code accompanying the paper is available at http://pydsm.googlecode.com

A design flow for {\Delta}{\Sigma} modulators is illustrated, allowing quantization noise to be shaped according to an arbitrary weighting profile. Being based on FIR NTFs, possibly with high order, the flow is best suited for digital architectures. The work builds on a recent proposal where the modulator is matched to the reconstruction filter, showing that this type of optimization can benefit a wide range of applications where noise (including in-band noise) is known to have a different impact at different frequencies. The design of a multiband modulator, a modulator avoiding DC noise, and an audio modulator capable of distributing quantization artifacts according to a psychoacoustic model are discussed as examples. A software toolbox is provided as a general design aid and to replicate the proposed results., Comment: 5 pages, 18 figures, journal. Code accompanying the paper is available at http://pydsm.googlecode.com

In humans, depression is often triggered by prolonged exposure to psychosocial stressors and is often associated with cardiovascular comorbidity. Mounting evidence suggests a role for endocannabinoid signaling in the regulation of both emotional behavior and cardiovascular function. Here, we examined cardiac activity in a rodent model of social stress-induced depression and investigated whether pharmacological inhibition of the enzyme fatty acid amide hydrolase (FAAH), which terminates signaling of the endocannabinoid anandamide, exerts antidepressant-like and cardioprotective effects. Male Wistar Kyoto rats were exposed to five weeks of repeated social stress or control procedure. Starting from the third week, they received daily administration of the selective FAAH inhibitor URB694 (0.1 mg/kg, i.p.) or vehicle. Cardiac electrical activity was recorded by radiotelemetry. Repeated social stress triggered biological and behavioral changes that mirror symptoms of human depression, such as (i) reductions in body weight gain and sucrose solution preference, (ii) hyperactivity of the hypothalamic-pituitary-adrenocortical axis, and (iii) increased immobility in the forced swim test. Moreover, stressed rats showed (i) alterations in heart rate daily rhythm and cardiac autonomic neural regulation, (ii) a larger incidence of spontaneous arrhythmias, and (iii) signs of cardiac hypertrophy. Daily treatment with URB694 (i) increased central and peripheral anandamide levels, (ii) corrected stress-induced alterations of biological and behavioral parameters, and (iii) protected the heart against the adverse effects of social stress. Repeated social stress in Wistar Kyoto rats reproduces aspects of human depression/cardiovascular comorbidity. Pharmacological enhancement of anandamide signaling might be a promising strategy for the treatment of these comorbid conditions.

In many application environments, it is not possible to practice nondestructive evaluation (NDE) by physically contacting the material under test with probes. Examples include the evaluation of objects that are moving (e.g., on an assembly line), hot materials, materials that cannot risk contamination, and more. Lack of contact means that, typically, the coupling material is air. This poses specific requirements, due to the acoustic impedance mismatch that an air layer can provoke and the consequent energy losses. In this chapter, some examples of setups, transducer arrangements, and signal processing strategies capable of addressing such requirements are illustrated, showing how concepts presented in the previous chapters can be deployed in this particular context. Furthermore, some typical achievable results are illustrated, with respect to a few different testing scenarios, such as the testing of composite materials, the inspection of concrete, imaging of surfaces or thin materials, and food inspection.

This book deals with a number of fundamental issues related to the practical implementation of ultrasonic NDT techniques in an industrial environment. The book discusses advanced academic research results and their application to industrial procedures. The text covers the choice and generation of the signals energizing the system to probe position optimization, from quality assessment evaluation to tomographic inversion. With a focus to deepen a number of fundamental aspects involved in the specific objective of designing and developing an ultrasonic imaging system for nondestructive testing, aimed to automatically classify the entire production of an industrial production line, targeted to the field of precision mechanics. The contents of this book is the result of the common effort of six University Research Groups that focused their research activities for two years on this specific objective, working in direct conjunction with primary industrial firms, in a research project funded by the Italian government as a Strategic Research Project.

The possibility of taking advantage of multiprobe setups for ultrasound non-destructive testing (NDT) is introduced with reference to its physical and signal processing aspects. Preliminarily, a major distinction is made between phased-arrays and actual multi-transducer configurations. Then, most of the chapter is devoted to the latter type of setup. In this framework, the previously introduced channel model developed for single-probe operation, is extended to setups featuring multiple transmitting transducers (TXs) and receiving transducers (RXs) meant to be employed simultaneously in a so-called multiple input, multiple output (MIMO) configuration. It is also illustrated how this configuration relates to multi-user communication networks. Proper merit factors suitable for characterizing the performances of multiprobe systems are presented by taking advantage of the probabilistic system view introduced for single-probe systems. Finally, various classes of signals that can be adopted in MIMO NDT systems are described. These excitations may be designed according to random or deterministic approaches. In better detail, special techniques based on tessellation of the time-frequency (TF) plane are developed to design excitation signals capable of joining assuring contextually the good degree of appropriateness for MIMO setups and the good signal-to-noise (SNR) and resolution properties of chirps.

The pulse-echo (PuE) model based on short pulses is introduced as a starting point. Its limits in terms of signal-to-noise ratio (SNR) are reviewed, together with the tradeoff between the excitation energy and the time resolution. It is shown how signal processing can improve the overall performance in terms of system sensitivity and resolution as long as the exciting waveform is chosen taking into account the system characteristics and is in agreement with the adopted processing techniques. The degrees of freedom on which one can operate are the time evolution law of the excitation signal and the processing technique adopted on the receiving end. In their exploitation, the designer should consider the physical characteristics of the hardware devices being employed in order to optimize the overall performance. The importance of introducing merit factors is discussed. By offering a quantitative measure of system performance, they are indispensable tools to drive formal optimization strategies and for comparing different approaches. Application-related merit factors are introduced for trying to overcome some current limitations and to prepare the ground for the extension of ultrasonic techniques to multiple input, multiple output (MIMO) systems, which are considered in the following chapter.

Aims To describe atrial fibrillation (AF) management in member countries of the European Society of Cardiology (ESC) and to verify cardiology practices against guidelines. Methods and results Among 182 hospitals in 35 countries, 5333 ambulant and hospitalized AF patients were enrolled, in 2003 and 2004. AF was primary or secondary diagnosis, and was confirmed on ECG in the preceding 12 months. Clinical type of AF was reported to be first detected in 978, paroxysmal in 1517, persistent in 1167, and permanent in 1547 patients. Concomitant diseases were present in 90% of all patients, causing risk factors for stroke to be also highly prevalent (86%). As many as 69% of patients were symptomatic at the time of the survey; among asymptomatic patients, 54% were previously experienced symptoms. Oral anticoagulation was prescribed in 67 and 49% of eligible and ineligible patients, respectively. A rhythm control strategy was applied in 67% of currently symptomatic patients and in 44% of patients who never experienced symptoms. Conclusion This survey provides a unique snapshot of current AF management in ESC member countries. Discordance between guidelines and practice was found regarding several issues on stroke prevention and antiarrhythmic therapy.

True random sources are not implementable in digital hardware, so that many practical applications have historically relied on pseudo-random generators in order to avoid the potentially long prototyping times and the costs of dedicated analog design. However, pseudo-random sources have liabilities that make them hardly suitable for some tasks (notably security related ones). Previous attempts to conciliate security, cost-effectiveness, and rapid development included the exploitation of the analog accessory parts often present on programmable devices. In these designs some analog blocks are used for their side effects (noise amplification) rather than for their originally intended behaviour. Conversely, here we report a direct implementation of a true random source on programmable, low-cost, general-purpose hardware, where all blocks are used only for their nominal function. To the best of the authors' knowledge, this is the first proposal of this sort. The design exploits an FPAA, and is based on a non-linear system exhibiting chaotic behaviour. Measures confirm the correct operation, high throughput, and robustness of the system. Copyright © 2005 John Wiley & Sons, Ltd.

Ablation of the left atrial free wall around the pulmonary vein ostia (LAFW) may be effective in the treatment of chronic atrial fibrillation associated with mitral disease (CAF-MVD). Using light and conventional electron microscopy analyses, we wanted to evaluate, in CAF-MVD, the interstitial remodeling in the LAFW as well as in a more remote region, such as the left atrial appendage (LAA). LAFW and LAA samples were obtained from 33 CAF-MVD patients during combined mitral surgery and radiofrequency ablation and from 16 autoptic controls. Interstitial fibrosis (IF) and perivascular fibrosis (PF), capillary densities and the maximal oxygen diffusion distance were morphometrically determined. In CAF-MVD patients, the LAFW, compared with the LAA, showed a higher percentage of IF (7.16+/-3.23% versus 2.51+/-1.40%, respectively), a lower myocardial capillary density per mm(2) (830+/-106 versus 989+/-173) and an increased oxygen maximal diffusion distance (19.70+/-1.27 microm versus 18.13+/-1.58 microm). All these values were also significantly different than controls. No differences were found in evaluating PF. At variance with the LAA, in CAF-MVD patients, the LAFW around the pulmonary vein ostia is a region characterized by a marked interstitial remodeling such that it may be morphologically indicated as an appropriate target for ablation treatment aimed at sinus rhythm restoration.

Acute myocardial infarction follows a circadian pattern, with a morning peak ascribed to sympathetic activation. However, about 20% of myocardial infarctions occur between midnight and 6 AM; these events may have different characteristics.We studied 1571 patients with acute myocardial infarction (866 anterior and 705 inferior myocardial infarctions) who were admitted to our coronary care units from January 1997 to February 2001. We noted the time of the infarction, its anatomic location, and the involved coronary arteries.Inferior myocardial infarctions were more frequent during the night (midnight to 6 AM) than during other periods of the day (n = 238, 34% of all inferior infarctions, P0.01). When coronary angiography was performed (795 patients), 92% (127/138) of inferior infarctions were due to right coronary artery occlusion, whereas only 54% (130/242) of the remaining inferior infarctions involved that artery.Inferior myocardial infarctions occur disproportionately at night, usually due to right coronary artery occlusion. This suggests that a protective role for sleep may be limited to left coronary artery-related events.

Constant-envelope wideband signals are useful excitations in many engineering tasks. Here, we consider their hardware-based generation, reviewing recent results and adding new ones. We focus on a synthesis technique based on FM modulators and discrete-time chaotic sources. The degrees of freedom offered by this approach are discussed and managed to satisfy common requirements. We show that good rate-of-mixing chaotic sources are highly desirable; then, given that most current-generation chaotic sources do not provide adequate values, we illustrate how their designs can be improved. We conclude by suggesting possible developments regarding weakly mixing chaotic sources.

We investigate the statistical properties of a process defined by summing the subsequent values assumed by the state of a chaotic map, and by constraining the result within a finite domain by means of a folding operation. It is found that the limit distribution is always uniform regardless of the chaotic map, that the folded sums tend to be independent of the future evolution of the chaotic trajectory, and that, whenever the map state is multidimensional, the folded sum vectors tend to be made of independent components. Numerical simulations are employed to show that practical finite-time behaviors are correctly approximated by the limit results herein provided. Finally, the theory is applied to give a formal ground to some key steps in the derivation of the spectrum of signals that are chaotically frequency modulated.

A chaotic-map random number generator (RNG) is defined using a chaotic map and a bit-generation function. When the map function is exactly known, for a given bit-generation function, the entropy-rate of the generated output bit sequence is asymptotically the highest rate at which truly random bits can be generated from the map. The supremum of the entropy-rate amongst all bit-generation functions is called the binary metric entropy, which is the highest rate at which information can be extracted from any given map using the optimal bit-generation function. In this paper, we provide converse and achievable bounds on the binary metric entropy. The achievability is based on a sequence of universal bit-generation functions in the sense that the bit-generation function is not dependent on the specific map. The proposed sequence of bit-generation functions offers a fairly simple implementation which can easily be realized on hardware for practical purposes.

Cardiovascular disease increases with age as well as alterations of cardiac electrophysiological properties, but a detailed knowledge about changes in cardiac electrophysiology relevant to arrhythmogenesis in the elderly is relatively lacking. The aim of this study was to determine specific age-related changes in electrophysiological properties of the ventricles which can be related to a structural-functional arrhythmogenic substrate. Multiple epicardial electrograms were recorded on the ventricular surface of in vivo control and aged rats, while arrhythmia vulnerability was investigated by premature stimulation protocols. Single or multiple ectopic beats and sustained ventricular arrhythmias were frequently induced in aged but not in control hearts. Abnormal ventricular activation patterns during sinus rhythm and unchanged conduction velocity during point stimulation in aged hearts suggest the occurrence of impaired impulse conduction through the distal Purkinje system that might create a potential reentry substrate.

Previously, we observed that a single low-intensity premature ventricular stimulation could occasionally induce spontaneous ectopic beats in normal rat hearts. Possible hypothesis for the arrhythmia is that a premature beat can encounter a zone of conduction block to initiate reentry. However, enhanced dispersion of repolarization, a necessary condition for initiation of reentry, is unlikely to be present in normal myocardium. Thus, the main objective of the present study was to perform detailed pace mapping measurements in normal ventricular myocardium with a view to identify pacing sites and critical coupling intervals which could induce spontaneous ectopic beats and to characterize the reentrant circuits.

Good quality entropy sources are indispensable in most modern cryptographic protocols. Unfortunately, many currently deployed networked devices do not include them and may be vulnerable to Random Number Generator (RNG) attacks. Since most of these systems allow firmware upgrades and have serial communication facilities, the potential for retrofitting them with secure hardware-based entropy sources exists. To this aim, very low-cost, robust, easy to deploy solutions are required. Here, a retrofittable, sub 10$ entropy source based on chaotic dynamics is illustrated, capable of a 32 kbit/s rate or more and offering multiple serial communication options including USB, I2C, SPI or USART. Operation is based on a loop built around the Analog to Digital Converter (ADC) hosted on a standard microcontroller., Comment: 4 pages, 6 figures. Pre-print from conference proceedings; IEEE 21th International Conference on Electronics, Circuits, and Systems (ICECS 2014), pp. 175-178, Dec. 2014

BACKGROUND The extent to which atrial myocardium is remodeled in patients with persistent lone atrial fibrillation (LAF) is largely unknown. OBJECTIVE The purpose of this study was to perform a clinicopathologic investigation in patients with persistent LAF. METHODS We characterized structural and molecular remodeling in atrial biopsies from 19 patients (17 males, mean age 49 years) with persistent (> 7 days; n = 8) or long-lasting persistent (> 1 year; n = 11) LAF who underwent surgical ablation. Atrial tissue from 15 autopsy samples without clinicopathologic evidence of heart disease served as controls. RESULTS Morphometric analysis showed cardiomyocyte hypertrophy and greater amounts of myolytic damage and interstitial fibrosis in persistent LAF patients compared to controls (P

Log-domain filters are a promising design paradigm for analog signal processing. They achieve tunability and operation up to high frequencies, with voltage and power requirements typically better than those of conventional filtering architectures. Implementation can be based only on capacitors, current sources and an exponential, differential V/I converter referred to as the E-cell. Non-idealities in the E-cell, like the presence of non-negligible input currents due to finite βF, can reduce system performance. The aim of this paper is to investigate E-cell-based design strategies and to introduce a duality principle whose exploitation can allow finite βF compensation. As a validation, HSPICE simulation results are illustrated for a second-order bandpass filter. Copyright © 2000 John Wiley & Sons, Ltd.

The inadequate long-term efficacy of anti-arrhythmic therapy has been one of the main reasons for the development of non-pharmacological interventions for patients with atrial fibrillation such as catheter and surgical ablation. This has greatly increased interest in the functional morphology and electrophysiological properties of the atria and related anatomical structures. This article is the second of a two-part review that aims to provide anatomical and functional details concerning some of the principal anatomical sites commonly targeted by ablative procedures for treating atrial fibrillation, and covers pulmonary veins, ganglionated plexi, caval veins, and the ligament of Marshall. It also provides some general information about site-specific ablation procedures.

We consider the use of {\Delta}{\Sigma} modulators in ac motor drives, focusing on the many additional degrees of freedom that this option offers over Pulse Width Modulation (PWM). Following some recent results, we show that it is possible to fully adapt the {\Delta}{\Sigma} modulator Noise Transfer Function (NTF) to the rest of the drive chain and that the approach can be pushed even to a fine adaptation of the NTF to the specific motor loading condition. We investigate whether and to what extent the adaptation should be pursued. Using a representative test case and extensive simulation, we conclude that a mild adaptation can be beneficial, leading to Signal to Noise Ratio (SNR) improvements in the order a few dB, while the advantage pushing the adaptation to the load tracking is likely to be minimal.