Body Surface Potential Mapping System Research Articles

Comparison of electrical dyssynchrony parameters between electrocardiographic imaging and a simulated ECG belt

AimsElectrocardiographic imaging (ECGi) and the ECG belt are body surface potential mapping systems which can assess electrical dyssynchrony in patients undergoing cardiac resynchronization therapy (CRT). ECGi-derived dyssynchrony metrics are calculated from reconstructed epicardial potentials based on body surface potentials combined with a thoracic CT scan, while the ECG belt relies on body surface potentials alone. The relationship between dyssynchrony metrics from these two systems is unknown. In this study we aim to compare intra-ventricular and inter-ventricular dyssynchrony metrics between ECGi and the ECG belt. MethodsSeventeen patients underwent ECGi after CRT. A subsample of 40 body surface potentials was used to simulate the ECG belt. ECGi dyssynchrony metrics, calculated from reconstructed epicardial potentials, and ECG belt dyssynchrony metrics, calculated from the sampled body surface potentials were compared. ResultsThere was a strong positive correlation between ECGi left ventricular activation time (LVAT) and ECG belt left thorax activation time (LTAT) (R = 0.88 ; P < 0.001) and between ECGi standard deviation of activation times (SDAT) and ECG belt-SDAT (R = 0.76; P < 0.001) during intrinsic rhythm. The correlation for both pairs was also strong during biventricular pacing. Ventricular electrical uncoupling, a well validated ECGi inter-ventricular dyssynchrony metric, correlated strongly with ECG belt-SDAT during intrinsic rhythm (R = 0.76; P < 0.001) but not biventricular pacing (R = 0.29; P = 0.26). Cranial or caudal displacement of the simulated ECG belt did not affect LTAT or SDAT. ConclusionECGi- and ECG belt-derived intra-ventricular and inter-ventricular dyssynchrony metrics were strongly correlated. The ECG belt may offer comparable dyssynchrony assessment to ECGi, with associated practical and cost advantages.

Optimized Electrode Locations for Wearable Single-Lead ECG Monitoring Devices: A Case Study Using WFEES Modules based on the LANS Method.

Body surface potential mapping (BSPM) is a valuable tool for research regarding electrocardiograms (ECG). However, the BSPM system is limited by its large number of electrodes and wires, long installation time, and high computational complexity. In this paper, we designed a wearable four-electrode electrocardiogram-sensor (WFEES) module that measures six-channel ECGs simultaneously for ECG investigation. To reduce the testing lead number and the measurement complexity, we further proposed a method, the layered (A, N) square-based (LANS) method, to optimize the ECG acquisition and analysis process using WFEES modules for different applications. Moreover, we presented a case study of electrode location optimization for wearable single-lead ECG monitoring devices using WFEES modules with the LANS method. In this study, 102 sets of single-lead ECG data from 19 healthy subjects were analyzed. The signal-to-noise ratio of ECG, as well as the mean and coefficient of variation of QRS amplitude, was derived among different channels to determine the optimal electrode locations. The results showed that a single-lead electrode pair should be placed on the left chest above the electrode location of standard precordial leads V1 to V4. Additionally, the best orientation was the principal diagonal as the direction of the heart’s electrical axis.

Leads Selection of Body Surface Potential Mapping During Atrial Fibrillation: A Sequential Selection Based on Adapted Botteron’s Approach

Atrial fibrillation (AF) is a common clinical arrhythmia with a lifetime risk and has become an attractive topic of clinical research and health management. Although the 12-lead classical ECG configuration is adequate for the detection of AF, its configuration is suboptimal for constructing surface potential mapping or extracting other diagnostic features during AF. Body surface potential mapping (BSPM) has a broad application prospect in AF study, but the electrode wiring is complicated and the hardware cost is high. This paper proposes a method to improve the performance of leads selection algorithm from a 128-lead BSPM system with equidistantly spaced electrodes. 128-lead BSPM data obtained from 8 AF patients were used in the study. Leads selection was performed by a sequential selection based on an adapted Botteron’s approach and multiple linear regression. The result showed that the proposed method has significant improvement on the performance of the accurate reconstruction of dominant frequency on the patient-specific dataset. The proposed method may not only improve the performance on the spectrum characteristic but also effectively improve the performance of time domain criteria when the number of selected leads is above 12.

Classification of Atrial Fibrillation Recurrence Based on a Convolution Neural Network With SVM Architecture

Although radio frequency ablation is the most effective treatment for atrial fibrillation (AF), there is still a high recurrence rate. The purpose of this paper was to initially assess the probability of the recurrence of AF based on the preoperative body surface potential mapping (BSPM) signals, in other words, to predict the efficiency of ablation and assist physicians in developing more effective treatment options. At present, deep learning methods based on convolutional neural networks (CNNs) do not require complex mathematical abstractions or manual interventions; thus, higher computation efficiency can be obtained in such research. However, the use of the fully connected multi-layer perceptron (MLP) algorithms has shown low classification performance. This paper proposes an improved CNN algorithm (CNN-SVM method) for the recurrence classification in AF patients by combining with the support vector machine (SVM) architecture. The algorithm is validated on the preoperative AF signals of 14 patients for classification. All postoperative patients are followed up for one year; ten of them remain in sinus rhythm, whereas the other four turn back to AF. The ECG data for these patients are obtained through the 128-Lead BSPM system. The results show that the proposed CNN-SVM method can automatically extract the characteristic information through the CNN network. The constructed model ultimately achieved an accuracy of 96%, a sensitivity of 88%, and a specificity of 96%. It is concluded that the CNN-SVM method solves the drawbacks of MLP only for separating linear data. It improves the overall performance of AF recurrence classification, thereby providing a valuable reference for doctors to develop personalized treatment plans.

Minimal configuration of body surface potential mapping for discrimination of left versus right dominant frequencies during atrial fibrillation.

Ablation of drivers maintaining atrial fibrillation (AF) has been demonstrated as an effective therapy. Drivers in the form of rapidly activated atrial regions can be noninvasively localized to either left or right atria (LA, RA) with body surface potential mapping (BSPM) systems. This study quantifies the accuracy of dominant frequency (DF) measurements from reduced-leads BSPM systems and assesses the minimal configuration required for ablation guidance. Nine uniformly distributed lead sets of eight to 66 electrodes were evaluated. BSPM signals were registered simultaneously with intracardiac electrocardiograms (EGMs) in 16 AF patients. DF activity was analyzed on the surface potentials for the nine leads configurations, and the noninvasive measures were compared with the EGM recordings. Surface DF measurements presented similar values than panoramic invasive EGM recordings, showing the highest DF regions in corresponding locations. The noninvasive DFs measures had a high correlation with the invasive discrete recordings; they presented a deviation of <0.5 Hz for the highest DF and a correlation coefficient of >0.8 for leads configurations with 12 or more electrodes. Reduced-leads BSPM systems enable noninvasive discrimination between LA versus RA DFs with similar results as higher-resolution 66-leads system. Our findings demonstrate the possible incorporation of simplified BSPM systems into clinical planning procedures for AF ablation.

Combined Cardiac Impairments in End-Stage Renal Disease

To the Editor,We were impresses by the article published in PediatricCardiology by Kobayashi et al. [1], The Impact of Changein Volume and Left-Ventricular Hypertrophy on Left-Ventricular Mechanical Dyssynchrony in Children WithEnd-Stage Renal Disease. The study provides an importantcontribution to the scarce data on functional/organic car-diac impairments in children with end-stage renal disease(ESRD).Kobayashi et al. detected left-ventricular dyssynchrony(LVD) using real-time three-dimensional echocardiogra-phy in children with ESRD undergoing renal replacementtherapy (peritoneal dialysis or hemodialysis). The authorsstated that dyssynchrony was significantly greater in ESRDchildren, especially those on hemodialysis therapy, com-pared with controls and improved after hemodialysis. Theauthors concluded that ESRD children presented volumeload and left-ventricular hypertrophy (LVH), which wereprobably associated with increased LVD. They assumedthat cardiac dyssynchrony could be an independent pre-dictor of serious cardiac events in patients with ESRD [1].Regarding cardiac impairments in such patients, wewould like to draw attention to our findings [2, 3] showingintraventricular conduction disturbances in ESRD childrenin whom no abnormalities were observed on 12-leadelectrocardiographic and echocardiographic examinations.In our study, a noninvasive multielectrode (87-lead) bodysurface potential mapping system (Fukuda Denshi Co Ltd,Tokyo, Japan) was applied to create isochrone maps toprecisely reflect a sequence of ventricular activation time(i.e., VAT maps).In our ESRD children treated conservatively [2] or withrenal replacement [3], abnormal maps with delayed VATvalues were noted, indicating some perturbations within theintraventricular conduction pathway. Patients on hemodi-alysis for\1 year demonstrated VAT maps typical for leftbundle branch block (LBBB), which was partially allevi-ated after renal transplantation, becoming left anteriorfascicle block. In children on hemodialysis for [1 year,VAT maps showed more serious disturbances in the formof complete LBBB that was normalized to incompleteLBBB due to kidney transplantation.According to Kobayashi et al. [1], disorders of electricalactivation, consequently leading to LVD, can occur inpatients with ESRD. Multifactoral damage of the ventric-ular myocardium probably causes spatiotemporal hetero-geneity and therefore LVD, which is additionally impairedby LVH. It is supposed that LVH can be a response ofthe myocardium to numerous ‘‘cross-talking networks’’appearing both as the result of ESRD and during renal-replacement therapy.Our findings [2, 3] suggest that disturbances of theintraventricular conduction system observed in childrenwith ESRD can be a significant component of LVD, whichinevitably leads to systolic left-ventricular dysfunction.

Heart ventricular activation in VAT difference maps from children with chronic kidney disease

Children with chronic kidney disease (CKD) are affected by cardiovascular complications, including disturbances in the intraventricular conduction system. Body surface potential mapping (BSPM) is a non-invasive method of assessing the cardioelectrical field. Our aim was to investigate conduction disturbances in young CKD patients using ventricular activation time (VAT) maps. Our study comprised 22 CKD children (mean age: 13.1 ± 2.5 years) treated conservatively and 29 control patients. For each child 12-lead electrocardiogram (ECG) readings were taken, and blood pressure and serum concentrations of iPTH, Pi, t-Ca, creatinine, Fe+3, ferritin, and Hb, as well as eGFR were measured. All children underwent registration in the 87-lead BSPM system, and group-mean VAT maps and a difference map, which presents statistically significant differences between the groups, were created. The VAT map distribution in CKD patients revealed abnormalities specific to left anterior fascicle block. The difference map displays the areas of intergroup VAT changes, which are of discriminative value in detecting intraventricular conduction disturbances. Intraventricular conduction impairments in the left bundle branch may occur in children with CKD. BSPM enables conduction disturbances in CKD children to be detected earlier than using 12-lead ECG. The difference map derived from the group-mean isochrone maps precisely localizes the sites of disturbed conduction in the heart intraventricular conduction system.

Epinephrine Bolus Test in Detecting Long QT Syndrome Mutation Carriers with Indeterminable Electrocardiographic Phenotype

In long QT syndrome (LQTS), prolonged and heterogeneous ventricular repolarization predisposes to serious arrhythmias. We examined how QT intervals are modified by epinephrine bolus in mutation carriers of three major LQTS subtypes with indefinite QT interval. Genotyped, asymptomatic subjects with LQTS type 1 (LQT1; n = 10; four different KCNQ1 mutations), type 2 (LQT2; n = 10; three different HERG mutations), and type 3 (LQT3; n = 10; four different SCN5A mutations), and healthy volunteers (n = 15) were examined. Electrocardiogram was recorded with body surface potential mapping system. After an epinephrine 0.04 μg/kg bolus QT end, QT apex, and T-wave peak-to-end (Tpe) intervals were determined automatically as average of 12 precordial leads. Standard deviation (SD) of the 12 channels was calculated. Heart rate increased 26 ± 10 bpm with epinephrine bolus, and similarly in all groups. QT end interval lengthened, and QT apex interval shortened in LQTS and normals, leading to lengthening of Tpe interval. However, the lengthening in Tpe was larger in LQTS than in normals (mean 32 vs 18 ms; P < 0.05) and SD of QT apex increased more in LQTS than in normals (mean 23 vs 7 ms; P < 0.01). The increase in Tpe was most pronounced in LQT2, and in SD of QT apex in LQT1 and LQT2. Abrupt adrenergic stimulation with a moderate dose of exogenous epinephrine affects ventricular repolarization in genotype-specific fashion facilitating distinction from normals. This delicate modification may help in diagnosing electrocardiographically silent mutation carriers when screening LQTS family members.

The Effect of Antihistamine Cetirizine on Ventricular Repolarization in Congenital Long QT Syndrome

Many drugs are known to block cardiac potassium channels, thus prolonging QT interval and predisposing to malignant arrhythmias. Patients with congenital long QT syndrome are particularly vulnerable, but usually electrophysiological effects of drugs have not been assessed in these patients at risk. Fifteen asymptomatic patients with type 1 (LQT1), 15 patients with type 2 (LQT2) long QT syndrome, and 15 healthy volunteers took a placebo and cetirizine 10 mg. In addition, healthy volunteers took cetirizine 50 mg. The study was single-blinded and randomized. Exercise tests were performed during stable plasma concentrations. The electrocardiogram was recorded with a body surface potential mapping system (BSPM). Data were analyzed with an automated analyze program. QT intervals to the T wave apex and T wave end and their difference (Tp-e) were determined at rest and at specified heart rates during and after exercise. Cetirizine did not lengthen the QT intervals at rest or during exercise and recovery in any group. It shortened Tp-e at rest in LQT1 and LQT2 patients and during exercise test in LQT1 patients, thus slightly decreasing electrocardiographic transmural dispersion of repolarization. Cetirizine does not adversely modify ventricular repolarization in types 1 and 2 long QT syndrome, suggesting that it might be used safely in these long QT syndrome patients.

Reproducibility of Computerized Measurements of QT Interval from Multiple Leads at Rest and During Exercise

Accurate measurement of the QT interval is important for diagnosing long QT syndrome (LQTS), and in research on determinants of ventricular repolarization time. We tested automatic analysis of QT intervals from multiple ECG leads on chest. Eleven healthy volunteers and 10 genotyped LQTS patients were tested at rest and during exercise with a bicycle ergometer twice 1-31 months apart. Electrocardiograms were recorded with the body surface potential mapping system, and 12 precordial channels were selected for analysis. Averaged QT peak and QT end intervals were determined with an automated algorithm, and the difference QT end minus QT peak (Tp-e) was calculated. Repeatability was assessed by coefficient of variation (CV) between measurements. Within one test at rest the QT end intervals were highly repeatable with CV 0.6%. In repeated tests CV was 4.4% for QT end interval and 3.5% when the QT interval was corrected for heart rate. In exercise test at specified heart rates, mean CV was 3.0% for QT end and 2.9% for QT peak interval. The CV of Tp-e interval was 10.2% at rest, and 9.3% in exercise test. Reproducibility was comparable between healthy subjects and LQTS patients. The BSPM system with automated analysis produced accurate and highly repeatable QT interval measurements. Reproducibility was adequate also over prolonged time periods both at rest and in exercise stress test. The method can be applied in studying duration of ventricular repolarization time in different physiologic and pharmacologic interventions.

Diagnosing Old MI by Searching for a Linear Boundary in the Space of Principal Components

Body surface potential mapping (BSPM) is a technique employing multiple electrodes to capture, via noninvasive means, an indication of the heart's condition. An inherent problem with this technique is the resulting high-dimensional recordings and the subsequent problems for diagnostic classifiers. A data set, recorded from a 192-lead BSPM system, containing 74 records is investigated. QRS isointegral maps, offering a summary of the information obtained during ventricular depolarization, were derived from 30 old inferior myocardial infarction and 44 normal recordings. Principal component analysis was applied to reduce the dimensionality of the recordings and a linear classifier was employed for classification. This perceptron-based classifier has been adapted so that the final weight and bias values are estimated prior to the learning process. This estimation process, referred to as the linear hyperplane approach (LHA), derives the estimated weights from a bisector hyperplane, placed orthogonal to the means of two class distributions in an n-dimensional Euclidean space. Estimating weights encourages a network to exhibit better generalization ability. Utilizing a number of different principal components as input features, the LHA achieved an average sensitivity and specificity of 79.58% and 76.45%, respectively, across all experiments. The average accuracy of 76.73% achieved with this approach was significantly better than the other benchmark classifiers evaluated against it.

Implantable monitoring systems: Design considerations and challenges

The use of electrocardiographic (ECG) information in the diagnosis and follow-up evaluation of cardiac patients has evolved from the simple limb lead surface ECG to more sophisticated instruments using advanced recording and diagnostic methods. Advances in electronic technology have provided continued improvement in the performance of ECG monitoring equipment such as the i2-1ead resting and stress ECG, the interpretive electrocardiograph, the signal-averaged ECG, ambulatory ECG monitors, and body surface potential mapping systems. Holter I reported in 1961 the use of a portable ECG recording device. With the introduction of this first ambulatory monitor, clinicians had the opportunity to identify the presence of various cardiac rhythms while the patient was performing his or her normal daily activities. Applications of these ambulatory monitors have included identification of arrhythmias, evaluation of patient symptoms, quantification of ischemia (for both anginal and silent episodes), and performance evaluation of implantable pacemakers and defibrillators. 2 Ambulatory monitors are presently available with magnetic tape, digital random access memory, or min i -ha rd disk drives as their data storage medium. Some digital recorders also include real-time E C G analysis,3 which allows the ambulatory monitor to store higher-resolution ECG data during detected events. Variants of ambulatory monitors include event recorders and loop monitors. These monitors are typically used by the patients over longer periods of time, primarily for the identification of less frequent arrhythznias. However, their operation requires that any cardiac events be symptomatic to be recorded, because the patient must direct the storage of the event into memory for future retrieval and clinical review. In a similar manner, pacemaker technology has evolved from the simple nonprogrammable single-chamber pulse generators to dual-chamber rate-modulated pacemakers. The 1970s saw the introduction of the first programmable pacemakers, the use of the long-life lithium batteries, and basic memory storage with the storage of paced and sensed events. The 1980s were highlighted by the introduction

Some imaging parameters of the oblique dipole layer cardiac generator derivable from body surface electrical potentials.

The goal of noninvasively imaging the cardiac electrical generator is considerably complicated by the conductive anistropy of the cardiac muscle which, as featured in the oblique dipole layer model of ventricular depolarization, introduces muscle fiber geometry and a conductivity tensor as additional unknowns. The ventricular surface activation map has been previously presented as a description of the cardiac generator in image form, but the integral equation defining its relationship to the body surface potentials is valid only under the less accurate uniform dipole layer hypothesis. Using an argument from differential geometry, which allows the integral equation approach to be bypassed, we show that the critical points of this map can still be localized on the heart surface from the body surface potentials in a manner fully consistent with the oblique dipole layer model. Thus, in principle, a realistic and useful "image-like" output is possible in a limited way even without explicit information regarding conductivity anisotropy. The realization of this output will require improvements in the temporal resolution presently available from existing body surface potential mapping systems.

Level-crossing approach to the compression of body surface potential maps

Body Surface Potential Mapping (BSPM) is a technique for the high-resolution study and analysis of the electrical events in the heart. The technical complications and the high cost of custom-designed systems have limited the use of BSPM to a small number of laboratories. Almost all efforts to simplify BSPM systems have concentrated so far on the reduction of the number of the electrodes employed with subsequent extrapolation of the measured information to the whole thoracic surface. In this report a new approach for simplifying the BSPM system is suggested. The system uses a different type of electrodes, which do not record the ECG signal, but only detect the time instants when the incoming ECG signal crosses some given threshold level (Level-Crossings (LC)). Different threshold levels may be attributed to different subsets of electrodes. An algorithm for the reconstruction of complete BSPM information from those LC is proposed, based on utilization of the Karhunen-Loeve expansion method. This approach is justified by treating the BSPM signals as samples of a three-dimensional random process. The complete recordings of 200 BSPMs (training set) with different cardiac pathologies is used to derive the set of basis functions for the reconstruction procedure. The reconstructions are then performed on the LC of 81 subjects (test set) with a distribution of pathologies similar to that of the training set. Best performance is found when four threshold levels (± 100, ± 500 μV) are selected, for four intermittent grids of 45 electrodes, thus comprising a whole net of 180 electrodes. The average RMS reconstruction error for a member of the rest set is about 136 μV, whereas the correlation between the original and estimated BSPMs is around 0.91. These results suggest that by implementing an efficient signal compression scheme, even with the limited information provided by the LC, a clinically useful reconstruction of the BSPM is obtained.

Body surface potential mapping system equipped with a microprocessor for the dynamic observation of potential patterns.

A body surface potential mapping system equipped with a microprocessor has been developed. It enables high-speed real-time and simultaneous observation of e.c.g. data of 96 lead points in a character display mode. The machine has functions not only to perform basic data processing such as baseline correction and linear interpolation for malfunctioned electrodes but also to generate an isopotential contour map, record data onto a floppy disc, make hard copies of displayed patterns and characters, etc. To increase the operation speed, all the assembler programs were put in one module. Thus, an operator can easily recognise the spatial motion pattern of the body surface potential map and, in addition, find malfunctioned channels by observing the pattern. A belt type electrode system allows quick and adaptable attachment. The practical usefulness of the system has been proved with the co-operation of cardiologists with over 120 cases of cardiac disease.

A Body Surface Potential Mapping System Equipped with a Microprocessor for the Dynamic Observation of Potential Pattern

A Body Surface Potential Mapping System Equipped with a Microprocessor for the Dynamic Observation of Potential Pattern