Transmural, interventricular, apicobasal and anteroposterior action potential duration gradients are all essential to the genesis of the concordant and realistic T wave: A whole-heart model study.

BACKGROUND: It has been reported that ventricular repolarization dispersion resulting from transmural, apicobasal and interventricular action potential duration (APD) gradients makes the T wave concordant with the QRS complex. METHOD AND RESULTS: A whole-heart model integrating transmural, apicobasal, interventricular and anteroposterior APD gradients was used, and the corresponding electrocardiograms were simulated to study the influence of these APD gradients on the T-wave amplitudes. The simulation results showed that changing a single APD gradient (e.g., interventricular APD gradient alone) only made substantial changes to the T-wave amplitudes in a limited number of leads and was not able to generate T waves with amplitudes comparable with clinical findings in all leads. A combination of transmural, apicobasal and interventricular APD gradients could simulate T waves with amplitudes similar to clinical values in the limb leads only. Adding the anteroposterior APD gradient into the model greatly improved the consistency between the simulated T-wave amplitudes and the clinical values. CONCLUSION: The simulation results support that the transmural, apicobasal, interventricular and the anteroposterior APD gradient are all essential to the genesis of the clinical T wave.

[Optimization of electrode location and size on simulation in electric field distribution of atrial defibrillation].

A distributed simulation method of electric field based on the atrial defibrillation of the heart modeling and finite element solution is proposed in this study. In order to solve the problem that ordinary clinical trials could not measure the actual distribution of the defibrillation electric field in the heart accurately, this method provides a research tool for electrical defibrillation. A complete atrial anatomical structure in the heart model is used in the research, the finite element method is proceeded to solve; Three parameters: defibrillation threshold voltage, the high field strength rate and the defibrillation threshold energy are set to evaluate the effect of defibrillation. The heart electric field distributions of transvenous atrial defibrillation with different electrode locations or sizes are simulated. The simulation results and the reported results match fairly well, which initially verify the feasibility of this method.

Computer simulation of clinical electrophysiological study.

BACKGROUND: Computer simulation is an important method for the basic researches of cardiac electrophysiology to prove the mechanisms and hypotheses of cardiac arrhythmias by reproducing body surface electrocardiograms. In this research, we extend the researches of heart models to the computer simulation of clinical electrophysiological study (EPS) as a clinical application of heart models. METHOD: Through setting the standard EPS pacing protocols, including extrastimuli and incremental pacing in the heart models, we simulated the corresponding excitation propagations in the heart and the intracardiac electrograms that would be measured with catheter electrodes. RESULTS: Examples of complicated cases observed during EPS are reproduced in this research, including the induction of a Wenckebach pattern, the induction and termination of supraventricular tachycardia due to the reentry loop of antidromic atrioventricular reentrant tachycardia for the Wolff-Parkinson-White (WPW) syndrome (Type A), and the localization of an accessory pathway for the WPW syndrome (Type A). CONCLUSION: This study demonstrates an application of whole-heart modeling and computer simulation to clinical EPS.

A multidifferentiator-based approach to the reliable determination of T-wave offset in electrocardiograms.

The determination of T-wave offset is still a very difficult task in the measurement of the QT interval. Several methods of determining the T-wave offset can be categorized into slope methods, threshold methods, or differential methods. The threshold- and slope-based methods are sensitive to low-frequency noise. The differential methods, in which a single differential operation is usually used for feature extraction, are susceptible to morphological variations in the range of the T-wave offset. In this study, a multidifferential filter comprising a series of simple multiscale differentiators with multiorders is proposed as a feature selector and extractor for T-wave offset in electrocardiograms (ECGs). This newly proposed approach was tested on artificial ECGs (the Conformance Testing Services for Computerized Electrocardiography Test data set: 1919 ECGs were generated with signal-to-noise ratios ranging from 10 to 60 dB, in increments of 0.5 dB, with 172,306 T waves with specified references) simulated at various noise levels and a set of clinical ECGs (3415 ECGs with 14,099 T waves, annotated by 3 cardiologists) and compared with existing detection methods. The accuracies achieved with the proposed approach were -0.269 ± 5.53 and 0.400 ± 9.89 milliseconds for the artificial and clinical ECGs, respectively. These test results indicate that the proposed method outperforms the other methods evaluated on both the artificial and clinical ECGs. The proposed approach is also more suitable for clinical applications in accordance with the performance requirements of the International Electrotechnical Commission.

An architecture for cross-hospital access to electrocardiogram data.

Owing to a lack of easy access to an individual's electrocardiogram (ECG) data that may be distributed across multiple hospitals, medical practice using serial ECG analysis has not so far been extensively used. Motivated to address this problem, we design and implement an architecture for cross-hospital access to ECG data. The architecture provides a Web portal for retrieving a particular patient's ECG data distributed across a number of ECG data sources. Two important features of this architecture are (1) the distributed search mechanism that uses a master patient index to determine what ECG data sources are likely to contain the ECG data pertaining to a specified patient and (2) the Web service-based interoperable method for accessing disparate ECG data sources. We show that the architecture provides an effective search and retrieval facility for cross-hospital access to ECG data; we show this by implementing and employing a prototype in an experimental scenario consisting of two disparate ECG data sources located at two sites. Our study demonstrates a significant effort to improve the ease of cross-hospital access to ECG data.

Simulation of vaginal wall biomechanical properties from pelvic floor closure forces map.

We simulated the way that pelvic floor muscles (PFM) generate zonal compression on the vagina and urethra in order to maintain urinary continence. Raw data were obtained using a probe to map the distribution of vaginal closure forces. Simulation model was made using ordinary Spring-mass model. The biomechanical properties are applied to the spring of the model. We simulated four models that are applied to asymptomatic subjects as controls and patients based on information obtained from the measured force maps using a vaginal probe. PFM values are measured when subjects are relaxed and during voluntary PFM contraction. Results show that simulation clearly distinguished between controls and patents and demonstrates that in the controls, after a period of 0.075 sec from the time when the rest force was added, the model was deformed to a neutral shape, and after another period of 0.075 sec from the time when the contract force was added at intervals of 0.001 sec, the closure force reaches maximum. The results render the simulation of the vaginal wall deformations that was obtained directly by the force maps. It shows that in controls the wall model is significantly deformed compared to that from the patient's model. In this research we simulated the response of the vaginal walls using spring mass model and the force maps of vaginal closure forces applied to control subjects and patients. The process of deformation of the vaginal wall is thus visualized demonstrating the relative pathologic differences between the two groups.

Long-term monitoring of heart rate, respiration rhythm, and body movement during sleep based upon a network.

A method for accurately recording heart rate (HR), respiration rhythm (RR), and body movement (BM) during sleep using a network-based system is proposed in this article. Its application to the long-term monitoring of HR, RR, and BM during sleep was examined. HR, RR, and BM were detected by pressure variations corresponding to changes in the heartbeat and respiratory motion, which were measured by a sensor unit placed beneath a pillow during sleep under completely unconstrained conditions. The pressure signals were digitized and transmitted to a remote database server using transmission control protocol (TCP)/Internet protocol (IP) via a netbox. In the server, the data were processed to obtain HR, RR, and BM. The overall performance of the system was examined using data collected over a 13-month period from a female subject. Besides the long-term profiles of HR, RR, and the periods during which the HR and RR were undetectable owing to BMs during sleep, the average frequency of BM in a day varied from 4.4 to 22.4/h, and the mean frequency over 332 nights was 8.3/h with a standard deviation of 2.2/h. Periodic biorhythms can also be assessed using the profiles of the average HR and certain frequency-domain parameters of HR variability. The rhythmic property of these profiles was confirmed to coincide with the subject's menstrual cycle. The results of this 13-month trial operation show that this system can be installed in the home environment; used to monitor HR, RR, and BM during sleep; and analyze various physiological rhythms in humans over prolonged periods.

Computer simulation of atypical Brugada syndrome.

Recently, the so-called atypical Brugada syndrome (BS) has been reported in few cases in literature. The typical BS is characterized by ST-segment elevation in the right precordial leads, whereas atypical forms of the disease are distinguished by electrocardiogram abnormalities of the J wave, and ST-segment elevation appeared in the inferior and lateral leads. In this work, we report a simulation of atypical BS based on a 3-dimensional whole-heart model. By setting the action potentials of Brugada model cells in different epicardial regions, we calculated 12-lead electrocardiogram and body surface potentials that are in good agreement with clinical data. Applying additional electrical stimuli, we obtained the induction of ventricular fibrillation in both typical and atypical BS forms. The calculated results confirm possibility of similar electrophysiological basis in both cases and suggest that BS can also be observed in inferior and lateral precordial leads.

Unconstrained monitoring of long-term heart and breath rates during sleep.

An unconstrained method for the long-term monitoring of heart and breath rates during sleep is proposed. The system includes a sensor unit and a web-based network module. The sensor unit is set beneath a pillow to pick up the pressure variations from the head induced by inhalation/exhalation movements and heart pulsation during sleep. The measured pressure signal was digitized and transferred to a remote database server via the network module. A wavelet-based algorithm was employed to detect the heart and breath rates, as well as body movement, during sleep. The overall system was utilized for a total six-month trial operation delivered to a female subject. The profiles of the heart and breath rates on a beat-by-beat and daily basis were obtained. Movements during sleep were also estimated. The results show that the daily average percentage of undetectable periods (UPs) during 881.6 sleep hours over a 180 day period was 17.2%. A total of 89.2% of sleep hours had a UP of not more than 25%. The profile of the heart rate revealed a periodic property that corresponded to the female monthly menstrual cycle. Our system shows promise as a long-term unconstrained monitor for heart and breath rates, and for other physiological parameters related to the quality of sleep and the regularity of the menstrual cycle.

A mobile network-based multimedia teleconference system for homecare services.

Because most research and development for homecare services have focused on providing connections between home and service centers, the goal of the present work is to develop techniques and create realtime communications to connect service centers and homecare workers in mobile environments. A key technical issue for this research is how to overcome the limitation of bandwidth in mobile media and networks. An effort has been made to balance performance of communication and basic demands in telehealth through optimized system design and technical implementation. Implementations using third generation (3G) Freedom Of Mobile multimedia Access (FOMA) and Personal Handyphone System (PHS) were developed and evaluated. We conclude that the system we developed based on 3G FOMA provides sufficient and satisfactory functions for use in homecare services.

Real-time monitoring of respiration rhythm and pulse rate during sleep.

A noninvasive and unconstrained real-time method to detect the respiration rhythm and pulse rate during sleep is presented. By employing the a trous algorithm of the wavelet transformation (WT), the respiration rhythm and pulse rate can be monitored in real-time from a pressure signal acquired with a pressure sensor placed under a pillow. The waveform for respiration rhythm detection is derived from the 26 scale approximation, while that for pulse rate detection is synthesized by combining the 2(4) and 2(5) scale details. To minimize the latency in data processing and realize the highest real-time performance, the respiration rhythm and pulse rate are estimated by using waveforms directly derived from the WT approximation and detail components without the reconstruction procedure. This method is evaluated with data collected from 13 healthy subjects. By comparing with detections from finger photoelectric plethysmograms used for pulse rate detection, the sensitivity and positive predictivity were 99.17% and 98.53%, respectively. Similarly, for respiration rhythm, compared with detections from nasal thermistor signals, results were 95.63% and 95.42%, respectively. This study suggests that the proposed method is promising to be used in a respiration rhythm and pulse rate monitor for real-time monitoring of sleep-related diseases during sleep.

The Macronova in GRB 050709 and the GRB-macronova connection.

GRB 050709 was the first short Gamma-ray Burst (sGRB) with an identified optical counterpart. Here we report a reanalysis of the publicly available data of this event and the discovery of a Li-Paczynski macronova/kilonova that dominates the optical/infrared signal at t>2.5 days. Such a signal would arise from 0.05 r-process material launched by a compact binary merger. The implied mass ejection supports the suggestion that compact binary mergers are significant and possibly main sites of heavy r-process nucleosynthesis. Furthermore, we have reanalysed all afterglow data from nearby short and hybrid GRBs (shGRBs). A statistical study of shGRB/macronova connection reveals that macronova may have taken place in all these GRBs, although the fraction as low as 0.18 cannot be ruled out. The identification of two of the three macronova candidates in the I-band implies a more promising detection prospect for ground-based surveys.

Ventricular fibrillation mechanisms and cardiac restitutions: An investigation by simulation study on whole-heart model.

BACKGROUND: The action potential duration (APD) and the conduction velocity (CV) restitution have been reported to be important in the maintenance and conversion of ventricular fibrillation (VF), whose mechanisms remain poorly understood. Multiple-wavelet and/or mother-rotor have been regarded as the main VF mechanisms, and APD restitution (APDR) and CV restitution (CVR) properties are involved in the mutual conversion or transition between VF and ventricular tachycardia (VT). METHODS AND RESULTS: The effects of APDR (both its slope and heterogeneity) and CVR on VF organization and conversion were examined using a "rule-based" whole-heart model. The results showed that different organizations of simulated VF were manifestations of different restitution configurations. Multiple-wavelet and mother-rotor VF mechanisms could recur in models with steep and heterogeneous APDR, respectively. Suppressing the excitability either decreased or increased the VF complexity under the steep or shallow APDR, respectively. The multiple-wavelet VF changed into a VT in response to a flattening of the APDR, and the VT degenerated into a mother-rotor VF due to the APDR heterogeneity. CONCLUSIONS: Our results suggest that the mechanisms of VF are tightly related to cardiac restitution properties. From a viewpoint of the "rule-based" whole-heart model, our work supports the hypothesis that the synergy between APDR and CVR contributes to transitions between multiple-wavelet and mother-rotor mechanisms in the VF.

A possible macronova in the late afterglow of the long-short burst GRB 060614.

Long-duration (>2 s) γ-ray bursts that are believed to originate from the death of massive stars are expected to be accompanied by supernovae. GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very stringent limits and its physical origin is still debated. Here we report the discovery of near-infrared bump that is significantly above the regular decaying afterglow. This red bump is inconsistent with even the weakest known supernova. However, it can arise from a Li-Paczynski macronova--the radioactive decay of debris following a compact binary merger. If this interpretation is correct, GRB 060614 arose from a compact binary merger rather than from the death of a massive star and it was a site of a significant production of heavy r-process elements. The significant ejected mass favours a black hole-neutron star merger but a double neutron star merger cannot be ruled out.

Understanding the impact of TV commercials: electrical neuroimaging.

Today, there is a greater interest in the marketing world in using neuroimaging tools to evaluate the efficacy of TV commercials. This field of research is known as neuromarketing. In this article, we illustrate some applications of electrical neuroimaging, a discipline that uses electroencephalography (EEG) and intensive signal processing techniques for the evaluation of marketing stimuli. We also show how the proper usage of these methodologies can provide information related to memorization and attention while people are watching marketing-relevant stimuli. We note that temporal and frequency patterns of EEG signals are able to provide possible descriptors that convey information about the cognitive process in subjects observing commercial advertisements (ads). Such information could be unobtainable through common tools used in standard marketing research. Evidence of this research shows how EEG methodologies could be employed to better design new products that marketers are going to promote and to analyze the global impact of video commercials already broadcast on TV.

Clinical significance of synthesized posterior/right-sided chest lead electrocardiograms in patients with acute chest pain.

BACKGROUND: 12-lead electrocardiograms (ECGs) provide insufficient information for the accurate diagnosis of posterior and/or right ventricular acute myocardial infarction (AMI) in patients with acute chest pain. Posterior chest leads (V7-V9) and/or right-sided precordial leads (V3R-V5R) provide important information from those specific areas, but these additional ECGs are not routinely recorded because of the time-consuming procedure involved. The purpose of the present study was to evaluate a newly developed system to synthesize these 6 additional lead ECGs non-invasively using standard 12-lead ECG information. PATIENTS AND METHODS: Thirty patients (25 men, 5 women; mean age: 65 ± 11 years) complaining of acute chest pain were enrolled. Standard 12-lead and V3R, V4R, V5R, V7, V8, V9 lead ECGs were successively recorded and compared with synthesized ECGs mathematically derived from standard 12-lead signals. RESULTS: The synthesized and actual ECG waveforms were almost identical, and there were significant correlations in ECG variables, including the P, QRS, and T waves (correlation coefficients about total 1-cycle signals: 0.97 in V3R; 0.93 in V4R; 0.88 in V5R; 0.98 in V7; 0.92 in V8; and 0.88 in V9, p<0.001). Both in patients with AMI (N=16) and in patients with ST elevation at the extended leads (N=8), significant correlations were also found (correlation coefficients were over 0.88 at all leads, p<0.001). The reproducibility of the ST segment was as good as that of the other ECG variables, even in patients with significant ST elevation due to posterior and/or right ventricular AMI. CONCLUSION: Synthesized posterior and right-sided precordial lead ECGs appear to be highly reliable and useful in the rapid diagnosis of AMI, especially in the early detection of posterior and/or right ventricular involvement, thereby alleviating patient distress.

On the use of EEG or MEG brain imaging tools in neuromarketing research.

Here we present an overview of some published papers of interest for the marketing research employing electroencephalogram (EEG) and magnetoencephalogram (MEG) methods. The interest for these methodologies relies in their high-temporal resolution as opposed to the investigation of such problem with the functional Magnetic Resonance Imaging (fMRI) methodology, also largely used in the marketing research. In addition, EEG and MEG technologies have greatly improved their spatial resolution in the last decades with the introduction of advanced signal processing methodologies. By presenting data gathered through MEG and high resolution EEG we will show which kind of information it is possible to gather with these methodologies while the persons are watching marketing relevant stimuli. Such information will be related to the memorization and pleasantness related to such stimuli. We noted that temporal and frequency patterns of brain signals are able to provide possible descriptors conveying information about the cognitive and emotional processes in subjects observing commercial advertisements. These information could be unobtainable through common tools used in standard marketing research. We also show an example of how an EEG methodology could be used to analyze cultural differences between fruition of video commercials of carbonated beverages in Western and Eastern countries.

Derive right precordial leads at higher intercostal spaces from 12-lead system for diagnosis of Brugada syndrome.

Recording the right procordial leads at higher intercostal spaces (ICS) can raise the sensitivity of the diagnosis on Brugada syndrome using ECG. However, the directive measurement of the right precordial leads at the higher ICSs is tedious and impractical. In this paper, we proposed a derivation method based on the information redundancy in the 12-lead system to study the possibility of deriving the right precordial leads at the higher ICSs from the commonly used Mason-Likar 12-lead ECGs. Through the evaluation based on the simulated Brugada-type ECGs and recorded ECGs from BS subjects, we found that the BS characteristic J wave and coved type ST elevation in the right precordial leads at the higher ICSs could be satisfyingly derived from the 12-lead ECGs. It is concluded that the derived precordial leads at the higher ICSs may serve as an assistant diagnosis tool to unmask Brugada syndrome.

Influences of sites and protocols on inducing ventricular fibrillation: A computer simulation study.

In cardiac electrophysiological study, several electrical stimulation protocols have been employed to induce ventricular fibrillations (VF). In addition, sites of inducing may have different impacts on inducing results as well as different inducing protocols. To study whether VF inducing method is determinant of induced outcome, we simulated VFs induced with different protocols at different sites based on the Wei-Harumi whole heart model. Simulations showed that only certain combinations of pacing protocols and sites could induce sustainable VFs, which had similar frequency distributions. This result suggested that the interactions between protocols and sites determine the odds of successful inducing but once the VF was induced, the pattern was solely determined by inner cardiac properties.