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Despite its potential prognostic value concurrent atrial ischemia is often overlooked in patients with acute myocardial infarction (AMI). There is no study concerning the relationship between atrial coronary circulation and dynamic PR-segment changes in patients with AMI. We evaluated dynamic PR-segment changes in 37 patients with AMI. The flow in the principal atrial coronary branches was diminished in 14 (38%) patients. Dynamic changes in the PR-segment level [median 47 (inter quartile range 19–55) μV vs. 23 (18–30) μV, P = 0.005] and PR-segment area [3.15 (1.75-3.69) nVs vs. 1.62 (1.18-2.04) nVs, P = 0.005] were significantly greater in patients with compromised than in those with normal flow in the atrial coronary branches. Our findings support the concept that atrial ischemia produces similar changes in the PR-segment as ventricular ischemia in the ST-segment. Given the possible deleterious consequences of atrial ischemia these data may have important clinical implications in evaluation of patient with AMI.

Background Novel small and wearable electrocardiogram (ECG) devices offer new means of recording cardiac activity in different applications. Our objective was to evaluate the performance of closely separated (6 cm) bipolar leads in differentiating subjects with left ventricular hypertrophy (LVH) from healthy subjects. Methods The material contained body surface ECG of 236 healthy and 116 LVH subjects. A total of 36 vertical, 30 horizontal, and 66 diagonal bipolar leads located on the anterior thorax were analyzed. The QRS amplitudes were calculated, and the leads' overall diagnostic performance was assessed by receiver operating characteristic (ROC) analysis. Results The best overall diagnostic performances were obtained from 2 areas: one near the precordial electrodes of standard leads V1 to V3 and the other on lower anterior thorax. Vertical and diagonal bipolar leads located at lower anterior thorax provided the highest ROC areas (≥0.79). These bipolar leads also provided similar sensitivities than the traditional Sokolow-Lyon method. Conclusion The new short distance vertical and diagonal bipolar leads are efficient in discriminating subjects with LVH from healthy subjects based on QRS amplitude.

Modern devices such as wearable and implantable systems provide new methods for bioelectric measurement while creating new needs to assess the efficacy of the measurements. A modeling related analysis method, called the region of interest sensitivity ratio (ROISR), has been developed and applied hitherto in analyzing EEG measurements. ROISR describes how well the sensitivity of a measurement is concentrated within the region of interest (ROI). The objectives of the present study were to demonstrate and evaluate the applicability of this method in analyzing the specificity of ECG leads and to compare the results with those previously published. Here the specificities of the 117 leads of a Dalhousie body surface ECG mapping system to different segments of the left ventricular myocardium and the whole right ventricular free wall were analyzed. The ROISR method was also validated with epicardial dipole simulations. The results are consistent with those from previous clinical studies, and the ROISR method is thus applicable in future studies where, e.g., sensitivity distributions of implantable ECG measurements are analyzed.

The hydrolytic degradation of oriented poly( L -lactide-co-glycolide) 85L/15G (PLGA 85/15) sample materials with various amounts of lactide monomer was monitored in vitro at 37 °C. The materials were manufactured from medical grade PLGA 85/15 by a two-step melt extrusion-die drawing process. Results showed that the hydrolytic degradation rate depended highly on the lactide monomer content, which in turn influenced the retention of mechanical properties, mass loss, crystallinity, and dimensional stability. Even small quantities of lactide monomer (0.05–0.20 wt%) affected especially the retention of mechanical properties, which started to decline rapidly upon the inherent viscosity reaching 0.6–0.8 dl/g due to hydrolytic degradation. Based on our hydrolytic degradation data, we constructed a simplified mathematical model of degradation-related strength retention and recommend it as a functional quality control tool for melt-processed biodegradable medical devices manufactured from poly( L -lactide-co-glycolide) 85L/15G.

Extracellular field potential (FP) recordings with microelectrode arrays (MEAs) from cardiomyocyte cultures offer a non-invasive way of studying the electrophysiological properties of these cells at the population level. Several studies have examined the FP properties of cardiomyocytes of various origins, including stem cell-derived cardiomyocytes. This focus reflects growing importance and interest in the field of MEA. High-quality cardiac FP signals are often difficult to obtain, especially from stem cell-derived cardiomyocyte cultures, which represent an important new field in cardiac electrophysiology. One way to improve the quality of these recordings is to average the cardiac FP signals. To date, however, no studies have examined the effect of averaging on cardiac FP signals. We report here that cardiac FP averaging can yield higher-quality signals than original individual FPs, and therefore promise more accurate detection of different phases and analysis of the cardiac FP signal. Averaged signals improved the signal-to-noise ratio (SNR), and obtaining reliable averages required approximately 50 cardiac cycles. We therefore propose that routine cardiac FP averaging can serve as a tool to compare the effects of different experimental conditions or stimuli on the properties of cardiac FPs.

Volume conductor head models contain thin tissue layers, some of which have highly contrasting conductivity values relative to neighboring tissues. We expound the cerebrospinal fluid (CSF) and the six cortical layers of the gray matter. The dual nature of the CSF competes with the well-known shunting behavior of the skull. The incorporation of the six ultra thin cortical layers demonstrate the significance of the electrical attraction and shunting of lead field currents in multilayered tissues owing to the inherent conductive properties of each tissue. We relate the similar effects of the CSF to the diploe, i.e., the soft bone between the two hard bone layers of the skull. A natural subsequence of this article will allow researchers and clinicians to conceptually understand the measurement sensitivity distribution of a bipolar electroencephalography (EEG) lead. We recommend including the highly conductive thin layers such as the diploe of the skull and the CSF into head models as well as further investigation into the cortical layers I-VI of the gray matter. Comprehensively, when a thin tissue layer differs in relative conductivity from its neighboring layers, it should be included in the model owing to its influence upon the EEG lead fields, i.e., the measurement sensitivity distributions.

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Mathematical models help to simulate and to study different phenomena related to the cardiac activation such as fibrillation and infarction. Even though the most realistic methods are the ones based on diffusion reaction, it has been proved that cellular automata approach can have good results with less computational load. The aim of this paper is to introduce software based on the cellular automata to simulate cardiac activation. This kind of tool is very useful for educational purpose as well as research purposes. It enables flexible studies with different geometries and cardiac activation parameters.

The present study applies modeling methods to study the simulated ECG of a subQ monitor with bipolar lead. The objective of the study was to analyze how different locations of ectopic activation affect the ECG obtained with horizontal and vertical electrode orientation. The ectopic activation was set to originate from 6 different locations and conduct through both ventricles. We had implants in 63 locations on anterior thorax. We analyzed the correlations between the ECG signals of horizontal and vertical orientations .The effects of activation origin on the correlation between vertical and horizontal orientations are smallest in the left thoracic region and right upper thorax. The effects of implantation and implant design on ECG should be studied by applying multiple activation sequences.

Modeling offers effective means of studying the effects of implant dimensions on the measured electrocardiograph (ECG) prior to any in vivo tests, and thus provides the designer with valuable information. Finite difference (FDM) and lead field approaches combined with cardiac activation models offer straightforward and effective methods for analyzing different ECG measurement configurations. In the present study such methods are applied in studying the effects of implant dimensions on the simulated ECG which describes an ectopic beat originating from the apex. The results indicated that the change in interelectrode distance has the largest effects on the ECG. Other parameters related implant dimensions have minor effect on the ECG. Teoría de la Señal y Comunicaciones

Lead design is a critical factor for detecting and redetecting lethal arrhythmias in electrograms (EGM) from Implantable Cardioverter Defibrillators (ICD). The estimation of the scope of a lead can help to elucidate the anatomical origin of recorded EGM and explain signal features. In this paper, we compare quantitatively the scope of true and integrated bipolar sensing leads by combining bioelectric signal modeling and numerical analysis. We define the scope in terms of the Mean Square Difference (MSD) between the EGM generated by the whole ventricular myocardium and the EGM generated by smaller regions within the ventricular myocardium. Results show that integrated bipolar leads have a wider scope than true bipolar leads, although narrower than unipolar leads. Further, the extent of myocardium within the scope is distributed for integrated bipolar leads along the septum and anteriorly, while for true bipolar leads is located close to the electrode site.

An implantable wireless, inductively powered ECG-monitoring device has been tested both in vitro and in vivo. Measurements were done in saline, on the body surface and in cows. Measurement results are reported and some considerations about the device suitability for a long-time monitoring are made.

The analysis of intracardiac Electrograms (EGM) recorded by transvenous lead systems in Implantable Cardioverter Defibrillators (ICD) often entails assumptions on the scope of the lead system. Based on bioelectric signal modeling and on numerical analysis, we studied quantitatively the scope of unipolar and bipolar lead configurations in ICD. We defined the scope in terms of the Mean Square Difference (MSD) between EGM generated by the whole myocardium, and EGM generated by different families of regions within the myocardium. For unipolar and bipolar lead systems, simulations showed that the smallest myocardial region involving a given value of MSD is characterized by the highest measurement sensitivity. Furthermore, the scope in the ventricles was found to be an order of magnitude smaller for bipolar leads than for unipolar leads. Bioelectric signal modeling combined with numerical analysis constitutes a powerful method to study quantitatively the scope of transvenous lead systems.

In this paper, we introduce a new modelling related parameter called region of interest sensitivity ratio (ROISR), which describes how well the sensitivity of an electroencephalography (EEG) measurement is concentrated within the region of interest (ROI), i.e. how specific the measurement is to the sources in ROI. We demonstrate the use of the concept by analysing the sensitivity distributions of bipolar EEG measurement. We studied the effects of interelectrode distance of a bipolar EEG lead on the ROISR with cortical and non-cortical ROIs. The sensitivity distributions of EEG leads were calculated analytically by applying a three-layer spherical head model. We suggest that the developed parameter has correlation to the signal-to-noise ratio (SNR) of a measurement, and thus we studied the correlation between ROISR and SNR with 254-channel visual evoked potential (VEP) measurements of two testees. Theoretical simulations indicate that source orientation and location have major impact on the specificity and therefore they should be taken into account when the optimal bipolar electrode configuration is selected. The results also imply that the new ROISR method bears a strong correlation to the SNR of measurement and can thus be applied in the future studies to efficiently evaluate and optimize EEG measurement setups.

To minimize time-consuming and expensive in vitro and in vivo testing, information regarding the effects of implantation and the implants on measurements should be available during the designing of active implantable devices measuring bioelectric signals such as electrocardiograms (ECG). Modeling offers a fairly inexpensive and effective means of studying and demonstrating the effects of implantation on ECG measurements prior to any in vivo tests, and can thus provide the designer with valuable information. Finite difference model (FDM) and lead field approaches offer straightforward and effective modeling methods supporting the designing of active implantable ECG devices. The present study demonstrates such methods in developing and studying ECG implants. They were applied in demonstrating the effects of implant dimensions and of electrode implantation on the measurement sensitivity of the ECG device. The results of the simulations indicated that the interelectrode distance is the factor of the implant design determining the lead sensitivity. Other parameters related implant dimensions and shape have minor effect on the morphology of the ECG or on the average sensitivity of the measurement. This is shown for example when the interelectrode distance was reduced to 1/3 of original the average lead sensitivity decreased by 69.1% while larger relative changes in other dimensions produced clearly smaller changes. It was also observed here that implanting the electrodes deeper under the skin has major effects on the local sensitivities in heart muscle and thus affect to the morphology of the ECG. The study indicated also that non-conducting medium (i.e. implant insulated body) between the electrodes increases the sensitivity on heart muscle compared to cases where only electrodes are implanted.

An ideal bioelectric measurement should be focused on and specific to the target region. Volume conductor effects such as the poorly conducting bones or the moderately conducting skin are known to affect the specificity and accuracy of the surface electroencephalography (EEG) measurements. This paper introduces a modeling study on the effect of bipolar EEG lead implantation on measurement sensitivity. The electrodes were implanted at two depths in the realistic human head, one on the skull and the other on the cortex. The effects on the measurement sensitivity were studied by means of the half-sensitivity volume (HSV) and the region of interest sensitivity ratio (ROISR). The results indicate that subcutaneous implantation notably enhances the accuracy and specificity of EEG measurement compared to the surface measurement. Deeper measurements i.e. implantation on the cortex enables specific monitoring of a small source volume in contrast to partial and whole regions such as the visual cortex. The results of the study implicate that in clinical practice the subcutaneous needle electrodes would provide more specific and accurate measurements of cortical activation than scalp measurements.

The objective of the study was to evaluate the effects of bipolar ECG lead orientation on the morphology and amplitudes of the ECG. We studied the differences between horizontal and vertical bipolar leads by analyzing body surface measurements of 236 normal patients. In this study we had 42 horizontal and vertical bipolar leads located on the anterior thorax. We calculated correlations and mean square differences (MSD) between horizontal and vertical lead orientations. The results of the study show that there are only a few lead locations in the left mid-thoracic region where horizontal and vertical orientations provide similar ECG morphology. There are also leads which produce high negative correlation which implies that only the phase of the signal changed. The study also shows that in most of the leads in the thoracic region the correlation between horizontal and vertical orientation is poor.

Non-invasive electrocardiographic (ECG) techniques for assessing the electrical activity of selected regions within the cardiac muscle can benefit from suitable positioning of surface electrodes. This positioning is usually guided heuristically and complemented by clinical and experimental studies, but there is a lack of general methods to characterize quantitatively the ability of a given electrode configuration to focus on selected regions of the heart. In this study we explore an approach to the characterization of the resolution of surface ECG systems based on the concept of Resolution Mass (RM). By integrating bioelectric signal modeling and numerical methods, we explore, in an application example, the location and size of the RM for a multielectrode ECG system. The concept of RM combined with bioelectric signal modeling and numerical methods constitutes a powerful tool to investigate the resolution properties of surface ECG systems. Teoría de la Señal y Comunicaciones

The present paper describes a study where effects of anterior myocardium on body surface potentials were investigated. The study combines numerical lead field analysis combined with cardiac automata model. Electric fields are calculated with finite difference method in a 3-D model of male thorax. The cardiac activation applied in the study is an ectopic beat originating in the apex. The correlations and mean differences between signal generated by anterior segments of left ventricle and signal generated by both ventricles were analysed for 117 leads. The results show that there are leads which have high correlation (>0.9) with low the relative mean difference (

The objective in bioelectric measurements such as ECG and EEG is to register the signal arising from sources in the region of interest. It is also desired that signal-to-noise ratio (SNR) of a measurement is high. The sensitivity of an ideal measurement should focus on and be greater on the target areas in comparison to other areas of the volume conductor. Previously the half-sensitivity volume (HSV) has been applied to describe how focused the measurement is. In this paper we introduce a concept of the half-sensitivity ratio (HSR) which describes how well the sensitivity is concentrated in HSV compared to other source regions i.e. how specific the measurement is to the sources in HSV. Further we may have different region of interests (ROI) to which the measurements are wanted to be specific. Then the concept is called region of interest sensitivity ratio (ROISR). We present here an application of the HSR in analysing sensitivity distributions of bioelectric measurements. We studied the effects of interelectrode distance and the scalp/skull/brain resistivity ratio on the HSR of a bipolar EEG measurement with a three- layer spherical head model. The results indicate that when the focus of interest is on cortical activity more specified and concentrated sensitivity distributions are achieved with smaller interelectrode distances. Further a preliminary measurement with visual evoked potentials provides evidence of the relationship between HSR and SNR of a measurement.

Most current Implantable Cardioverter Defibrillators (ICD) use intracardiac leads for electrogram (EGM) sensing and defibrillation (Belott & Reynolds, 2007). Intracardiac leads consist of several electrodes that for the basic functionality of ventricular tachyarrhythmia detection and termination, are inserted transvenously into the right ventricle (Gradaus et al., 2003; Swerdlow et al., 2007). In addition to intracardiac electrodes, ICD also use the casing of the implant as an indifferent, distant electrode. In ICD technology, three main intracardiac lead configurations are distinguished based on the combination of electrodes that they use, namely unipolar, dedicated bipolar and integrated bipolar. Unipolar leads, so-called because they use the casing of the implant as an indifferent electrode, consist of a single electrode located in the right ventricle, whereas bipolar leads, both dedicated and integrated, consist of two closely spaced electrodes located in the right ventricle. In general, unipolar lead configurations are used for cardiac defibrillation, while bipolar lead configurations are used for EGM sensing, i.e. they provide with the EGM signals from which heart rhythm can be extracted. Previous studies indicate that lead configuration can affect EGM sensing and ICD performance. For instance, it is well known that fundamental EGM features such as wave duration, wave amplitude and power spectrum, depend on the configuration of the recording leads (DeCaprio et al., 1977; Jenkins, 1992; Langberg et al., 1988; Parsonnet et al., 1980). Also, differences in ventricular fibrillation detection and redetection times have been reported when comparing ICD dedicated and integrated bipolar leads (Cooklin et al., 1999; Frain et al., 2007; Goldberger et al., 1998; Natale et al., 1996). Other studies have addressed the effects on EGM sensing, of artifacts originating from non-ventricular bioelectric sources. For example, inappropriate ICD discharges have been ascribed to myopotentials oversensing (Deshmukh & Anderson, 1998; Kowalski et al., 2008; Sandler & Kutalek, 1994; Schulte et al., 2001). Pacing stimulus artifacts, which are often associated to ICD undersensing, have been found to be greater in integrated than in dedicated bipolar leads (Menz et al., 1998). Finally, an optimized lead design for atrial sensing has been proposed, in order to facilitate rejection of artifacts such as R-waves and myopotentials (Nash et al., 2005). Therefore, the existing Analysis of the Lead Sensitivity Distribution in Implantable Cardioverter Defibrillator

In electroencephalography (EEG) measurements the highest possible signal-to-noise ratio is always sought in order to achieve measurement results of as high quality as possible. In an ideal measurement the sensitivity of the measurement should focus on the region of interest (ROI) in comparison to other source areas inside the volume conductor. A parameter called region of interest sensitivity ratio (ROISR) has been previously introduced by Vaisanen et al. for analyzing the sensitivity distribution of an EEG measurement. They have found that the ROISR parameter correlates with signal-to-noise ratio (SNR). The correlation is highest in an optimal case when all the signal sources are located within the ROI and all the noise sources are located outside the ROI in other parts of the volume conductor. In this paper we studied the effect of the size of the ROI on the correlation with multilead VEP measurements performed on three testees. The results show that when the ROI location and general measurement settings are chosen carefully, the ideal ROI radius in a VEP experiment is 20 mm. Further on, since the correlation is highest when the measurement parameters are ideally chosen the experiments indicate that the ROISR parameter could be used for optimising EEG measurement set-ups and it could also have applications in source localization.

We have been developing wearable and wireless impedance measurement device for monitoring impedance changes caused by change in lung conductivity. The measurement is conducted with tetrapolar electrode configuration. The distance of the electrodes is limited to 15 cm and thus there is need for optimization of the electrode locations. In the present study we studied the sensitivity of the electrode configurations on changes of impedance in the lungs by modeling and preliminary measurements. We studied the sensitivity distributions of impedance measurements by applying reciprocal lead field approach. We modeled 35 tetrapolar electrode combinations, 21 vertical and 14 horizontal, with a finite difference method in a realistic model of a human thorax. We analyzed the modeled impedance with two lung conductivities, deflated and inflated. We also measured impedances from two male testees with same 35 leads. The results of the study show lead configurations in upper thorax, both vertical and horizontal, are optimal to measure the impedance changes caused by conductivity changes of the lungs. The study also shows that results from modeling and measurements have fairly good correlation and thus the presented modeling methods are applicable in analyzing the sensitivity of leads to the changes of thoracic impedance.

In this study, we examined the effect of electrode locations to the motion artifacts during sports activities for impedance-based respiration measurement. The tests were performed with a previously developed wireless bioimpedance device. The aim was to discover which configurations would yield the maximum signal-to-artifact ratio (SAR). We had eight different electrode locations and 11 different configurations were compared. The test contained two parts, at first the measurements were performed by sitting in place on a chair and thereafter by running on a treadmill. The measurements show that the electrode locations which improve SAR can be determined but they slightly vary between the individuals.

Measurement of vital physiological parameters related to pulmonary and cardiac function during physical exercise provides well understood signs of the physical condition of a person. Most of the commercially available minimally intrusive breathing measurement techniques only assess respiration rate, though minute ventilation is a much more reliable meter of the metabolic rate. Thus, usually a bulky, static pneumotachograph system is used in more serious studies. Previously, we have developed a small wearable bioimpedance based breathing measurement system and in this study we further examined algorithms to estimate breathing parameters during exercise. A previous study to assess the accuracy of the system for volumic parameters was conducted with an ergometer exercise, but to gain wider acceptance the system has to work accurately also during more motion intensive activities like running generating large motion artefacts. Unfortunately, running produces strong motion artefacts that distort the breathing signal. To establish accurate breathing minute ventilation measurement despite the artefact, we developed two different robust signal processing approaches. We tested the algorithms on nine subjects running on a treadmill with gradually increasing speed comparing the results with a commercial spirometer. The mean relative error values in ventilation estimation for the two techniques are 12.1% and 11.3%, but there is great variance in the accuracy between subjects. Further investigations are needed to reach methods with better individual accuracy of the system. However, the methods developed have the potential to produce a small wearable breathing assessment device capable of accurately measuring volumic parameters of respiration.

There is currently no approved clinical method for monitoring of pulmonary flow and volume without highly obtrusive instrumentation like a mask. Impedance pneumography (IP) seems to be the most promising method to establish accurate Holter type breathing measurement. We measured IP and spirometer volume signal from 14 subjects in static conditions from six different tetrapolar electrode configurations using a chest band with textile silver electrodes. We compared the continuous waveforms from spirometer and IP with Pearson linear correlation coefficients ρ and found clear differences between the six configurations. For the best configuration the difference between the impedance and spirometer signals at ρ> 0.98 was almost insignificant for all subjects. In these static conditions the IP method was found to be both comfortable and accurate for continuous lung volume measurement.

New implantable ECG devices may provide more stable and noiseless measurements compared to body surface ECG measurements. When the electrodes are moved to inside of the body the way the ECG measurement is done is changing. Modeling can be an effective way to study effects of implantation to the capacity of electrodes to measure ECG compared to surface measurements. This work introduces a project where effects of electrode implantation to the magnitude and direction of lead sensitivity to detect cardiac source, lead field, was studied with a model of the thorax as a volume conductor. The study was based on 3D finite difference method (FDM) featuring visible human man. The results of the study indicate that the effect of electrode implantation under the skin (5-15 mm) to the way they measure ECG is rather small. Magnitude change is dependent of the studied lead and the change of the sensitivity to heart's equivalent sources in direction of lead field is minor.

� Abstract—The purpose of the present study was to evaluate how the brain sources located at different depths can be most effectively measured with bipolar EEG leads. The specificity of an EEG lead to detect sources was studied with a new parameter called region of interest sensitivity ratio (ROISR) by employing a spherical head model. We studied the specificity as a function of electrode distance and further as a function of scalp:skull:brain resistivity ratio. The simulations indicate that the closer to the surface of the brain the source is located, the shorter is the interelectrode distance in the optimal lead. Also in the case of superficial sources, the small misplacement of the electrodes results in a substantial decrease in specificity. The resistivity ratio has the largest effect on the specificity, when the source is located close to the surface of the brain. However in the case of deep sources, the resistivity ratio has only minimal effect on the specificity.

The objective of the study was to evaluate the performance of closely separated bipolar ECG leads in differentiating subjects with left ventricular hypertrophy from normal cases. We studied the horizontal, vertical and diagonal bipolar leads by analyzing body surface measurements of 236 normal and 305 LVH subjects. In this study we had 42 vertical, 35 horizontal and 36 diagonal leads located on the anterior thorax. We calculated the QRS amplitudes for each patient and applied ROC analysis to amplitude data. The results of the study show that there are only a few locations in the mid-thoracic region where diagonal and vertical orientations provide good or fair performance in differentiating LVH from normal based on QRS amplitude.