Chaotic Activation Research Articles

Integrated Ultrasound and Photoacoustic-Guided Laser Ablation Theranostic Endoscopic System.

Advancements in ablation techniques have paved the way towards the development of safer and more effective clinical procedures for treating various maladies such as atrial fibrillation (AF). AF is characterized by rapid, chaotic atrial activation and is commonly treated using radiofrequency applicators or laser ablation catheters. However, the lack of thermal lesion formation and temperature monitoring capabilities in these devices prevents them from measuring the treatment outcome directly. In addition, poor differentiation between healthy and ablated tissues leads to incomplete ablation, which reduces safety and causes complications in patients. Hence, a novel photoacoustic (PA)-guided laser ablation theranostic device was developed around a traditional phased-array endoscope. The proposed technology provides lesion formation, tissue distinguishing, and temperature monitoring capabilities. Our results have validated the lesion monitoring capability of the proposed technology through PA correlation maps. The tissue distinguishing capability of the theranostic device was verified by the measurable differences in the PA signal between pre-and post-ablated mice myocardial tissue. The increase in the PA signal with temperature variations caused by the ablation laser confirmed the ability of the proposed device to provide temperature feedback.

A chaotic discrete-time continuous-state Hopfield network with piecewise-affine activation functions

We construct a chaotic discrete-time continuous-state Hopfield networkwith piecewise-affine nonnegative activation functions and weight matrix with small positive entries. More precisely, there exists a Cantor set $ C $ in the state space such that the network has sensitive dependence on initial conditions at initial states in $ C $ and the network orbit of each initial state in $ C $ has $ C $ as its $ \omega $-limit set. The approach we use is based on tools developed and employed recently in the study of the topological dynamics of piecewise-contractions. The parameters of the chaotic network are explicitly given.

Competitive Drivers of Atrial Fibrillation: The Interplay Between Focal Drivers and Multiwavelet Reentry.

BackgroundThere is debate whether human atrial fibrillation is driven by focal drivers or multiwavelet reentry. We propose that the changing activation sequences surrounding a focal driver can at times self-sustain in the absence of that driver. Further, the relationship between focal drivers and surrounding chaotic activation is bidirectional; focal drivers can generate chaotic activation, which may affect the dynamics of focal drivers.Methods and ResultsIn a propagation model, we generated tissues that support structural micro-reentry and moving functional reentrant circuits. We qualitatively assessed (1) the tissue’s ability to support self-sustaining fibrillation after elimination of the focal driver, (2) the impact that structural-reentrant substrate has on the duration of fibrillation, the impact that micro-reentrant (3) frequency, (4) excitable gap, and (5) exposure to surrounding fibrillation have on micro-reentry in the setting of chaotic activation, and finally the likelihood fibrillation will end in structural reentry based on (6) the distance between and (7) the relative lengths of an ablated tissue’s inner and outer boundaries. We found (1) focal drivers produced chaotic activation when waves encountered heterogeneous refractoriness; chaotic activation could then repeatedly initiate and terminate micro-reentry. Perpetuation of fibrillation following elimination of micro-reentry was predicted by tissue properties. (2) Duration of fibrillation was increased by the presence of a structural micro-reentrant substrate only when surrounding tissue had a low propensity to support self-sustaining chaotic activation. Likelihood of micro-reentry around the structural reentrant substrate increased as (3) the frequency of structural reentry increased relative to the frequency of fibrillation in the surrounding tissue, (4) the excitable gap of micro-reentry increased, and (5) the exposure of the structural circuit to the surrounding tissue decreased. Likelihood of organized tachycardia following termination of fibrillation increased with (6) decreasing distance and (7) disparity of size between focal obstacle and external boundary.ConclusionFocal drivers such as structural micro-reentry and the chaotic activation they produce are continuously interacting with one another. In order to accurately describe cardiac tissue’s propensity to support fibrillation, the relative characteristics of both stationary and moving drivers must be taken into account.

Catheter ablation for atrial tachycardias: How tointerpret the unclear activation map?

Post-ablation atrial tachycardias (ATs) are characterized by low-voltage signals that challenge current mapping methods. In this study, we analyzed common mistakes during activation mapping and delineated a mapping strategy for correct interpretation of tachycardia mechanisms in patients with challenging underlying substrate. Thirty-one patients referred for AT ablation were selected for the study. Three types of incorrect activation patterns were identified, which were referred to as unrecognized block line (pseudo-macroreentry and pseudo-fig-8 reentry), incorrect activation timing window of interest (WOI) (chaotic activation), and mis-annotation of complex signals (multiple sites of "early meets late"). Pseudo-macroreentry and chaotic activation occur in focal or localized reentry AT with the error related to the WOI selection (four cases), incorrect annotation of local activation time (six cases), or a previous line of atrial block in (seven cases). Pseudo-fig-8 reentry (five cases) and multiple sites of "early meets late" (nine cases) occur in macroreentrant AT with blocked areas and low-voltage atrial substrate. All ATs were successfully eliminated at the origin site. We delineated a series of ATs in the setting of a disordered pattern of activation mapping encountered in patients after previous extensive ablation or atriotomy. The algorithm proposed rapidly corrects the activation map and identifies the mechanism of the AT.

Chaotic activation of developmental signalling pathways drives idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is characterised by an important remodelling of lung parenchyma. Current evidence indicates that the disease is triggered by alveolar epithelium activation following chronic lung injury, resulting in alveolar epithelial type 2 cell hyperplasia and bronchiolisation of alveoli. Signals are then delivered to fibroblasts that undergo differentiation into myofibroblasts. These changes in lung architecture require the activation of developmental pathways that are important regulators of cell transformation, growth and migration. Among others, aberrant expression of profibrotic Wnt-β-catenin, transforming growth factor-β and Sonic hedgehog pathways in IPF fibroblasts has been assessed. In the present review, we will discuss the transcriptional integration of these different pathways during IPF as compared with lung early ontogeny. We will challenge the hypothesis that aberrant transcriptional integration of these pathways might be under the control of a chaotic dynamic, meaning that a small change in baseline conditions could be sufficient to trigger fibrosis rather than repair in a chronically injured lung. Finally, we will discuss some potential opportunities for treatment, either by suppressing deleterious mechanisms or by enhancing the expression of pathways involved in lung repair. Whether developmental mechanisms are involved in repair processes induced by stem cell therapy will also be discussed.

A Hybrid Chaotic Oscillatory Neural Network (HCONN) Based Financial Time Series Prediction System

Financial time series prediction is one of the most complex and challenging problems in both AI and finance engineering. In our research, we proposed a Hybrid Chaotic Oscillatory Neural Network (HCONN) model by replacing the traditional sigmoid-based activation function with chaotic oscillatory activation function, which provides significant performance in the global minimum convergence through the application of Adaptive Moment Estimation optimizer. In addition, by integrating the latest R&D on Quantum Finance Theory (QFT) and its Quantum Price Level (QPL) as the deep features’ extraction, we add the daily 8 nearest QPLs together with the time series price variables as the input of our HCONN. In terms of system implementation, 12 different forex products including the AUDCHF, AUDUSD, CADCHF, EURAUD, EURCHF, EURGBP, EURUSD, GBPAUD, GBPCAD, GBPUSD, USDCAD and USDCHF are used. System performance results reveal that HCONN outperforms other financial models including: Feedforward Backpropagation Neural Network (FFBPN) and Chaotic Oscillatory Neural Network (CONN) in terms of training performance and forecast accuracy.

Endocardial Activation Drives Activation Patterns During Long-Duration Ventricular Fibrillation and Defibrillation.

Understanding the mechanisms that drive ventricular fibrillation is essential for developing improved defibrillation techniques to terminate ventricular fibrillation (VF). Distinct organization patterns of chaotic, regular, and synchronized activity were previously demonstrated in VF that persisted over 1 to 2 minutes (long-duration VF [LDVF]). We hypothesized that activity on the endocardium may be driving these activation patterns in LDVF and that unsuccessful defibrillation shocks may alter activation patterns. The study was performed using a 64-electrode basket catheter on the left ventricle endocardium and 54 6-electrode plunge needles inserted into the left ventricles of 6 dogs. VF was induced electrically, and after short-duration VF (10 seconds) and LDVF (7 minutes), shocks of increasing strengths were delivered every 10 seconds until VF was terminated. Endocardial activation patterns were classified as chaotic (varying cycle lengths and nonsynchronous activations), regular (highly repeatable cycle lengths), and synchronized (activation that spreads rapidly over the endocardium with diastolic periods between activations). The results showed that the chaotic pattern was predominant in early VF, but the regular pattern emerges as VF progressed. The synchronized pattern only emerged occasionally during late VF. Failed defibrillation shocks changed chaotic and regular activation patterns to synchronized patterns in LDVF but not in short-duration VF. The regular and synchronized patterns of activation were driven by rapid activations on the endocardial surface that blocked and broke up transmurally, leading to an endocardial to epicardial activation rate gradient as LDVF progressed.

Atrial Fibrillation Dynamics and Ionic Block Effects in Six Heterogeneous Human 3D Virtual Atria with Distinct Repolarization Dynamics.

Atrial fibrillation (AF) usually manifests as reentrant circuits propagating through the whole atria creating chaotic activation patterns. Little is yet known about how differences in electrophysiological and ionic properties between patients modulate reentrant patterns in AF. The goal of this study is to quantify how variability in action potential duration (APD) at different stages of repolarization determines AF dynamics and their modulation by ionic block using a set of virtual whole-atria human models. Six human whole-atria models are constructed based on the same anatomical structure and fiber orientation, but with different electrophysiological phenotypes. Membrane kinetics for each whole-atria model are selected with distinct APD characteristics at 20, 50, and 90% repolarization, from an experimentally calibrated population of human atrial action potential models, including AF remodeling and acetylcholine parasympathetic effects. Our simulations show that in all whole-atria models, reentrant circuits tend to organize around the pulmonary veins and the right atrial appendage, thus leading to higher dominant frequency (DF) and more organized activation in the left atrium than in the right atrium. Differences in APD in all phases of repolarization (not only APD90) yielded quantitative differences in fibrillation patterns with long APD associated with slower and more regular dynamics. Long APD50 and APD20 were associated with increased interatrial conduction block and interatrial differences in DF and organization index, creating reentry instability and self-termination in some cases. Specific inhibitions of IK1, INaK, or INa reduce DF and organization of the arrhythmia by enlarging wave meandering, reducing the number of secondary wavelets, and promoting interatrial block in all six virtual patients, especially for the phenotypes with short APD at 20, 50, and/or 90% repolarization. This suggests that therapies aiming at prolonging the early phase of repolarization might constitute effective antiarrhythmic strategies for the pharmacological management of AF. In summary, simulations report significant differences in atrial fibrillatory dynamics resulting from differences in APD at all phases of repolarization.

Mapping of focal atrial tachycardia with an uninterpretable activation map after extensive atrial ablation: tricks and tips.

Atrial tachycardias (ATs) after extensive ablation are increasingly common and challenging arrhythmias. The prolonged intra-atrial conduction time (IACT) during ATs in the milieu may complicate the mapping of focal ATs. In this present study, we aim to characterize the electrophysiological features of ATs in this unique setting and to delineate an effective mapping strategy further. In total, 13 patients (average age, 59±7 years) in a cohort of 80 patients referred for AT ablation were selected for the study. The patients all demonstrated an undistinguishable map not ready to be interpreted the 3-dimensional mapping. A total of 13 ATs were mapped with mean tachycardia cycle length of 296±70 ms. Two activation patterns were identified, which were referred to as pseudo-macroreentry and chaotic activation. The former was a focal AT originating from the vicinity of an area of conduction block with the IACT less than the window of interest duration (4 cases; IACT/window of interest ratio range, 0.93-0.98). The latter refers to a focal AT exhibiting a disorderly color mapping display with IACT exceeding the window of interest duration (9 cases; IACT/window of interest ratio range, 1.02-1.29). The IACT was determined after resetting the annotation. All ATs were successfully eliminated at the originating site. We delineated a series of focal ATs in the setting of a significantly prolonged IACT encountered in patients after previous extensive ablation. Two activation patterns were identified, which may help facilitate the mapping of focal ATs in this setting.

Revisiting heart activation-conduction physiology, part I: atria

This discussion paper re-examines the conduction-activation of the atria, based on observations, with respect to the complexity of the heart as an organ with a brain, and its evolution from a peristaltic tube. The atria do not require a specialized conduction system because they use the subendocardial layer to produce centripetal transmural activation fronts, regardless of the anatomical and histological organization of the transmural atrial wall. This has been described as "two-layer" physiology which provides robust transmission of activation from the sinus to the AV node via a centripetal transmural activation front. New productive insights can come from re-examining the physiology, not only during sinus rhythm but also during atrial tachycardias, in particular atrial flutter and atrial fibrillation (AF). During common flutter, the areas of slow conduction, in the isthmus and following trabeculations, particularly the subendocardial layer confines conduction through the trabeculations which supports re-entry. During experimental or postoperative flutter, the circular 2D activation around the obstacle follows the physiological transmural activation. Understanding this physiology offers insights into AF. During acute or protracted AF, the presence of stationary or drifting rotors is characteristic and consistent with normal physiological 2D atrial activation, suggesting that suppressing physiological transmural activation of AF will permanently restore normal sinus node atrial activation. In contrast, during permanent AF, normal 2D activation is abolished; the presence of transmural, serpentine, and chaotic atrial activation suggests that the normal physiological activation pattern has been replaced by a new, irreversible variety of atrial conduction that is a new physiology, which is consistent with evolution of complex systems.

Epicardial wave mapping in human long-lasting persistent atrial fibrillation: transient rotational circuits, complex wavefronts, and disorganized activity

To characterize the nature of atrial fibrillation (AF) activation in human persistent AF (PerAF) using modern tools including activation, directionality analyses, complex-fractionated electrogram, and spectral information. The mechanism of PerAF in humans is uncertain. High-density epicardial mapping (128 electrodes/6.75 cm(2)) of the posterior LA wall (PLAW), LA and RA appendage (LAA, RAA), and RSPV-LA junction was performed in 18 patients with PerAF undergoing open heart surgery. Continuous 10 s recordings were analysed offline. Activation patterns were characterized into four subtypes (i) wavefronts (broad or multiple), (ii) rotational circuits (≥2 rotations of 360°), (iii) focal sources with centrifugal activation of the entire mapping area, or (iv) disorganized activity [isolated chaotic activation(s) that propagate ≤3 bipoles or activation(s) that occur as isolated beats dissociated from the activation of adjacent bipole sites]. Activation at a total of 36 regions were analysed (14 PLAW, 3 RSPV-LA, 12 LAA, and 7 RAA) creating a database of 2904 activation patterns. In the majority of maps, activation patterns were highly heterogeneous with multiple unstable activation patterns transitioning from one to another during each recording. A mean of 3.8 ± 1.6 activation subtypes was seen per map. The most common patterns seen were multiple wavefronts (56.2 ± 32%) and disorganized activity (24.2 ± 30.3%). Only 2 of 36 maps (5.5%) showed a single stable activation pattern throughout the 10-s period. These were stable planar wavefronts. Three transient rotational circuits were observed. Two of the transient circuits were located in the posterior left atrium, while the third was located on the anterior surface of the LAA. Focal activations accounted for 11.3 ± 14.2% of activations and were all short-lived (≤2 beats), with no site demonstrating sustained focal activity. Human long-lasting PerAF is characterized by heterogeneous and unstable patterns of activation including wavefronts, transient rotational circuits, and disorganized activity.

On the emergence of chaos in dynamical networks

We investigate how changes of specific topological features result on transitions among different bounded behaviours in dynamical networks. In particular, we focus on networks with identical dynamical systems, synchronised to a common equilibrium point, then a transition into chaotic behaviour is observed as the number of nodes and the strength of their coupling changes. We analyse the network's transverse Lyapunov exponents (tLes) to derive conditions for the emergence of bounded complex behaviour on different basic network models. We find that, for networks with a given number of nodes, chaotic behaviour emerges when the coupling strength is within a specific bounded interval; this interval is reduced as the number of nodes increases. Furthermore, the endpoints the emergence interval depend on the coupling structure of network. We also find that networks with homogeneous connectivity, such as regular lattices and small-world networks are more conducive to the emergence of chaos than networks with heterogeneous connectivity like scale-free and star-connected graphs. Our results are illustrated with numerical simulations of the chaotic benchmark Lorenz systems, and to underline their potential applicability to real-world systems, our results are used to establish conditions for the chaotic activation of a network of electrically coupled pancreatic β-cell models.

Different types of long-duration ventricular fibrillation: Can they be identified by electrocardiography

We tested the hypothesis that after 2 minutes of ventricular fibrillation (VF), periods of highly organized activations occur on the endocardium, arising from an intramural mother rotor or triggered activity originating in the Purkinje fibers. In 6 anesthetized dogs, we recorded electrically induced VF from two-thirds of the endocardium with a 64-electrode basket catheter. In another 12 dogs, the study was repeated with the addition of the early afterdepolarization blocker pinacidil in 6 animals and the delayed afterdepolarization blocker flunarizine in the other 6 animals. We found that, in addition to periods of disorganized chaotic activation (type I pattern), at between 3 and 7 minutes of VF, 2 highly organized patterns were observed (type II pattern, regular activity and type III pattern, triggered activity). When present, these patterns were observed in all 64 electrodes simultaneously. Type II arises from the apex and may be an intramural mother rotor and type III arises focally in Purkinje fibers and may be caused by early afterdepolarizations. The optimal defibrillation strategy may be different for the 3 different VF patterns. Therefore, it is important to determine if these 3 patterns can be differentiated from the body surface electrocardiogram.

DNA damage, discoordinated gene expression and cellular senescence in osteoarthritic chondrocytes

The initiation/progression factors of osteoarthritic (OA) cartilage degeneration and the involved biological mechanisms remain rather enigmatic. One core reason for this might be a cellular senescence-like phenotype of OA chondrocytes, which might show a fundamentally different behavior pattern unexpected from the biological mechanism established in young cells. This study was designed to investigate one core property of senescent cells, the heterogeneity of gene expression, in OA chondrocytes by double-labeling immunolocalization using two genes (vimentin, S-100 protein) as surrogates, which are constitutively expressed by (normal) chondrocytes. The level of genomic DNA damage in OA chondrocytes was compared to normal chondrocytes and in vitro experiments designed to demonstrate that stochastic genomic DNA damage is able to induce heterogeneity of gene expression in chondrocytes. We show a significantly increased heterogeneity of gene expression for vimentin and S-100 protein as well as a significantly increased genomic DNA damage in the OA compared to normal chondrocytes, whereas no evidence of critical telomere shortening was found. In vitro experiments demonstrated that stochastic genomic DNA damage induced by increased oxidative or genotoxic stress is able to induce the heterogeneity in gene expression found in the OA cells in situ. Our results suggest that OA chondrocytes show a special form of age-related cell degeneration, "progressive/stress-induced senescence", progressing over time due to accumulated DNA damage and subsequent chaotic gene activation pattern. This promotes increased malfunctioning of the cells and finally the loss of their capacity to keep up cell and tissue homeostasis, i.e., prevent OA.

Epicardial Atrial Mapping Can Predict Elimination of Chronic Atrial Fibrillation After the Box Pulmonary Vein Isolation During Mitral Valve Surgery

The pulmonary veins (PV) and posterior left atrium (LA) may contribute to the occurrence and maintenance of atrial fibrillation (AF). We evaluated whether simple epicardial electrophysiological mapping can predict elimination of chronic AF after the box PV isolation procedure. Using a computerized 48-channel mapping system, we performed intraoperative atrial mapping in 16 patients with chronic AF associated with mitral valve (MV) disease. Patients' ages ranged from 48 to 76 years (mean, 61.4 years). AF duration ranged from 1 to 16 years (mean, 7.5±5.4 years). Simple box PV isolation was performed during the MV operation. Regular and repetitive activation was found in the LA of 12 of 16 patients, and irregular and chaotic activation was found in both atria in 4 of 16 patients; 12 patients with regular and repetitive activation of the LA were treated by box PV isolation and the other 4 patients with irregular and chaotic activation in both atria did not recover sinus rhythm after this procedure. AF-free rate was significantly higher in patients with regular and repetitive activation of the LA (P<0.01). Box PV isolation was effective in the treatment of chronic AF associated with MV disease. Epicardial atrial mapping may predict elimination of AF after the box PV isolation.

Dopaminergic dysfunction in alcoholism and schizophrenia – psychopathological and behavioral correlates

Dysfunction of central dopaminergic neurotransmission has been implicated in the pathogenesis of schizophrenia as well as drug and alcohol dependence. Different drugs of abuse stimulate dopamine release in the ventral striatum and thus reinforce drug consumption. Increased subcortical dopamine release has also been associated with the pathogenesis of positive symptoms in schizophrenia and may be driven by a prefrontal dopaminergic dysfunction. These seemingly heterogeneous findings may be explained by recent research in non-human primates. According to these studies, reward anticipation but not anticipated reward consumption is accompanied by a phasic dopamine release in the striatum and prefrontal cortex. In the striatum, phasic dopamine release primarily affects motivation, psychomotor activation and reward craving, while in the prefrontal cortex, dopaminergic stimulation is involved in the activation of working memory and reward anticipation. In alcoholism, previously neutral stimuli that have been associated with alcohol intake can become conditioned cues which activate phasic dopamine release and reward craving. In schizophrenia, stress-induced or chaotic activation of dopamine release may attribute incentive salience to otherwise irrelevant stimuli and thus be involved in the pathogenesis of delusional mood and other positive symptoms. Studies in humans and non-human primates emphasize the role of dopaminergic neurotransmission in reward anticipation and its dysfunction in different neuropsychiatric diseases.

Another case of electromagnetic interference in the operating theatre

Electromagnetic interference in the operating theatre can be a hazard for patients. Understanding of the phenomena that can lead to it is of paramount importance. I highlight a form of interference that to my knowledge has not been reported before and which posed a risk of injury to the patient. A 61-year-old male patient with non-insulin-dependent diabetes mellitus was anaesthetised for evacuation of a right chronic subdural haematoma. There was no focal deterioration and the Glasgow Coma Scale (GCS) was 14–15. The anaesthetic technique consisted of induction with propofol, fentanyl and atracurium and maintenance of anaesthesia with a mixture of nitrous oxide and isoflurane in oxygen. Neuromuscular blockade was maintained with incremental doses of atracurium, as indicated by monitoring of the neuromuscular junction. The peripheral nerve stimulator used was a Dakmed 750 Digital, attached just below the lateral aspect of the right knee, over the common peroneal nerve. Train-of-four (TOF) stimulation was applied on demand for the assessment of neuromuscular blockade. During the intervals between testing, the stimulator was switched on but idle. The diathermy device used was a Valleylab Force 2 CEM Electrosurgical Generator. The indifferent electrode paddle was sited at the left thigh. During the course of the anaesthetic, it was noticed that the right foot was jerking vigorously and the peripheral nerve stimulator was discharging in an erratic way. Just prior to that, TOF stimulation had shown clinical recovery of only the first twitch and no additional muscle relaxant was used, because the operation was nearing an end. Triggering of chaotic peripheral nerve stimulator activation coincided with activation of the monopolar diathermy. On closer observation, it was noticed that the cable of the monopolar probe of the diathermy was lying behind the stimulator, almost in contact with it. Activation of the diathermy after the diathermy cable was moved away from the stimulator did not affect the stimulator or cause jerking of the foot; the malfunction of the stimulator and movements of the foot recurred if the cable was returned to its original position. Interference between diathermy equipment and almost any electronic device in use in the theatre environment has been described before. There is extensive literature on the effects and safety of pacemakers and implantable cardioverter-defibrillators when diathermy is used [1]. Interference between a peripheral nerve stimulator and pacemaker that led to cardiac arrest has been described [2]. In this case, the unintentional proximity of the cable of the monopolar diathermy with the peripheral nerve stimulator caused uncontrolled discharge from the stimulator. The vigorous jerking of the foot may have several explanations, one of which is post-tetanic potentiation. I am not able to say if the voltage output of the stimulator was also increased during the incident (transformer-like inductive coupling effect could explain such a phenomenon). The fact that neuromuscular function was recovering facilitated the diagnosis; however, we do not know if harmful current was applied over the peroneal nerve during earlier phases of the operation. Prolonged application of an excessive voltage over a nerve could result in transient or permanent nerve damage. The diathermy device uses frequencies of 0.5–10 MHz, well above the 100 Hz tetanic stimulus used by a peripheral nerve stimulator. This frequency could be applied indirectly by inductive coupling to the nerve stimulator and then directly to the nerve through the stimulator leads. We do not know what are the effects of prolonged application of such frequencies to human nerves. Clinical examination revealed no damage to the patient's peroneal nerve. Nerve conduction studies were not performed. This incident is an example of a potentially harmful event in the operating theatre environment. Electromagnetic interference is ‘invisible’ even to an otherwise experienced eye and can have catastrophic results [3]. Diathermy cables should always be kept well separated from any other electronic equipment. Separation criteria should be followed for all electronic devices [4]. Special care should be taken in the presence of implantable electronic devices. At present, health workers are not trained to be aware of problems arising due to electromagnetic interference. Standards on electromagnetic compatibility and interference prevention of electronic devices exist, i.e. the European standard EN55011 [5], but more attention needs to be given in healthcare practice and planning to minimise risks.

Efficacy of pulmonary vein isolation for the elimination of chronic atrial fibrillation in cardiac valvular surgery

Background. Haissaguerre and colleagues emphasize the importance of the pulmonary veins as a source of ectopic foci for initiating paroxysmal atrial fibrillation (AF). We hypothesized that ectopic foci from the pulmonary veins could also act as drivers for maintaining chronic AF, and that surgical ablation of the pulmonary vein orifices could terminate chronic AF. Methods. Using a computerized 48-channel mapping system, we performed intraoperative atrial mapping in 12 patients with chronic AF associated with mitral valve disease. Patient age ranged from 24 to 82 years (mean, 60.4 years). AF duration ranged from 3 to 240 months (mean, 92 ± 84 months). Simple surgical isolation of the pulmonary vein orifices was performed during the mitral valve operation. Results. Regular and repetitive activation was found in the left atria of 9 out of 12 patients, and irregular and chaotic activation was found in both atria of 3 out of 12 patients. Chronic AF in the 9 patients (75%) with regular and repetitive activation of their left atria was successfully treated by a simple surgical isolation of the pulmonary vein orifices. The other 3 patients did not recover sinus rhythm after this procedure. In 1 case of recurrent AF, the patient recovered sinus rhythm during the follow-up period (AF-free rate, 83%). Conclusions. Surgical ablation of the pulmonary vein orifices was effective in the treatment of chronic AF associated with mitral valve disease. Intraoperative mapping may be useful in predicting the efficacy of a single pulmonary vein orifice isolation procedure.

The case against memory consolidation in REM sleep: Balderdash!

Unfortunately, some researchers think a good scientific theory is one that has been repeatedly confirmed, and a bad theory is one that has not received consistent confirmation. However, confirmation of a theory depends on the extent to which a hypothesis exposes itself to disconfirmation. One confirmation of a highly specific, falsifiable experiment can have a far greater impact than the disconfirmation of twenty experiments that are virtually unfalsifiable. This commentary (1) counteracts misleading biases regarding the REM sleep/memory consolidation theory, and (2) demonstrates how chaotic cerebral activation during sleep is an essential component of long-term memory storage processes.[Vertes &amp; Eastman]

Characteristics of atrial activation sequence of atrial fibrillation and flutter in a canine model

In order to induce either atrial fibrillation (af) or atrial flutter (AF) in 22 dogs under pentobarbital anesthesia, a right atriotomy parallel to the sulcus terminalis was performed, but closed with running sutures. Effective refractory periods (ERP) were measured in the sites of the appendages and the bodies in both atria. Further, we developed a computerised mapping system which enabled us to reveal sequential activation of various parts of the heart. As a result, we could assess the circuit of excitation which gave rise to AF. AF occurred in 7 of the 22 dogs, and af in the remaining 15 dogs. It was revealed that during AF there was a counterclockwise (5 dogs) or clockwise (2 dogs) reentrant pathway involving the right atrial free wall and superior vena caval orifice with consequent left atrial activation. Although standard limb lead electrocardiogram showed af, all dogs with sustained af had a regular activation sequence in the left atrium [at a cycle length (period) of 140.1 +/- 16.9 msec, arising either in the left atrial appendage (8 dogs) or adjacent to the left pulmonary vein (7 dogs)]. However, 12 of the 15 dogs had a chaotic activation sequence whereas the other 3 dogs showed a regular activation sequence in the right atrium. Statistically, during AF there was no significant difference between RA ERP (153.2 +/- 12.6 msec), LA ERP (146.4 +/- 14.4 msec) and LA cycle length (period) (140.1 +/- 16.9 msec). During af, there was no significant difference between LA ERP (131.7 +/- 15.2 msec) and LA cycle length (period) (125.7 +/- 9.1 msec), but RA ERP (165.4 +/- 15.5 msec) was significantly longer than the LA cycle length (period) (p < 0.0001). Although in the present experiment regular left atrial activation and complex right atrial activation were observed predominantly, the activation sequence of af was different in each dog. These results clearly indicate that to employ a mapping system like ours is necessary to determine relevant surgical procedures to stop af and AF.