A spline Laplacian ECG estimator in a realistic geometry volume conductor

Evaluation of Bipolar, Tripolar, and Quadripolar Laplacian Estimates of Electrocardiogram via Concentric Ring Electrodes

Surface Laplacian estimates via concentric ring electrodes (CREs) have proven to enhance spatial resolution compared to conventional disc electrodes, which is of great importance for P-wave analysis. In this study, Laplacian estimates for traditional bipolar configuration (BC), two tripolar configurations with linearly decreasing and increasing inter-ring distances (TC_LDIRD and TC_LIIRD, respectively), and quadripolar configuration (QC) were obtained from cardiac recordings with pentapolar CREs placed at CMV1 and CMV2 positions. Normalized P-wave amplitude (NAP) was computed to assess the contrast to study atrial activity. Signals were of good quality (20-30 dB). Atrial activity was more emphasized at CMV1 (NAP ≃ 0.19-0.24) compared to CMV2 (NAP ≃ 0.08-0.10). Enhanced spatial resolution of TC_LIIRD and QC resulted in higher NAP values than BC and TC_LDIRD. Comparison with simultaneous standard 12-lead ECG proved that Laplacian estimates at CMV1 outperformed all the limb and chest standard leads in the contrast to study P-waves. Clinical recordings with CRE at this position could allow more detailed observation of atrial activity and facilitate the diagnosis of associated pathologies. Furthermore, such recordings would not require additional electrodes on limbs and could be performed wirelessly, so it should also be suitable for ambulatory monitoring, for example, using cardiac Holter monitors.

Computer simulation comparison of tripolar, bipolar, and spline Laplacian electrocadiogram estimators

A comparison of the performance of the tripolar and bipolar concentric as well as spline Laplacian electrocardiograms (LECGs) and body surface Laplacian mappings (BSLMs) for localizing and imaging the cardiac electrical activation has been investigated based on computer simulation. In the simulation a simplified eccentric heart-torso sphere-cylinder homogeneous volume conductor model were developed. Multiple dipoles with different orientations were used to simulate the underlying cardiac electrical activities. Results show that the tripolar concentric ring electrodes produce the most accurate LECG and BSLM estimation among the three estimators with the best performance in spatial resolution.

Non-invasive Laplacian electrocardiography and moment of activation mapping

Laplacian Electrocardiogram (LECG) is a non-invasive approach providing high spatiotemporal distributed information of cardiac electrical activity. Recently researchers have recorded surface potentials from monopolar disc electrodes to estimate the Laplacian using finite difference algorithms or spline surface Laplacian estimators. Bipolar and quasi-bipolar electrodes have also been used to record LECG directly. Here based on the "Nine Point Method" (NPM), Laplacian tripolar concentric ring electrode active sensors were designed. High spatiotemporal resolution body surface LECG using the new tripolar active sensors was recorded. Moment of activation (MOA) isochronal maps used to detect cardiac electrical activation patterns exhibited on the body surface was also generated.

Tripolar Laplacian electrocardiogram and moment of activation isochronal mapping

The electrocardiogram (ECG) provides useful global temporal assessment of the cardiac activity, but has limited spatial capabilities. The Laplacian electrocardiogram (LECG), an improvement over the ECG, provides high spatiotemporal distributed information about cardiac electrical activation. We designed and developed LECG tripolar concentric ring electrode active sensors based on the finite element algorithm 'nine-point method' (NPM). The active sensors were used in an array of 6 by 12 (72) locations to record bipolar and tripolar LECG from the body surface over the anterolateral chest. Compared to bipolar LECG, tripolar LECG showed significantly higher spatial selectivity which may be helpful in inferring information about cardiac activations detected on the body surface. In this study the moment of activation (MOA), an indicator of a depolarization wave passing below the active sensors, was used to surmise possible timing information of the cardiac electrical activation below the active sensors' recording sites. The MOA on the body surface was used to generate isochronal maps that may some day be used by clinicians in diagnosing arrhythmias and assessing the efficacy of therapies.

Body surface Laplacian electrocardiogram of ventricular depolarization in normal human subjects

INTRODUCTION

The body surface Laplacian electrocardiogram (ECG) mapping provides a noninvasive means for spatiotemporal mapping of cardiac electrical events. The aim of the present study was to explore the relationship between the Laplacian ECG and the underlying cardiac activities during ventricular depolarization in healthy human subjects.

METHODS AND RESULTS

A 95-channel body surface potential ECG was recorded over the anterolateral chest from 11 healthy male subjects. The surface Laplacian (SL) ECG was estimated from the recorded potentials during QRS complex by means of a novel spline SL estimator, as well as by the conventional 5-point SL estimator for comparison purpose. A simulation study was also conducted using a realistic geometry heart-torso model in an attempt to qualitatively interpret the experimental results. For all subjects, more spatial details were observed in the SL ECG maps compared with the potential ECG maps, with spline SL more robust against noise than the 5-point SL. In total, three positive activities (denoted as P1, P2, P3) and four negative activities (denoted as N1, N2, N3, N4) in the spline SL ECG maps were observed during ventricular depolarization. Initial localized P1 and N1 activities were observed in 11 and 8 subjects, respectively. Then, the initial P1 was divided into three positive activities (P1, P2, P3) in 9 subjects. After the appearance of multiple positive activities, three negative activities (N2, N3, N4) appeared in 11, 8, and 9 subjects, respectively. Similar findings were obtained in the computer simulation study.

CONCLUSION

The present study demonstrates that the SL ECG provides more spatial details than the potential ECG, and multiple simultaneously active ventricular activities could be revealed in the SL ECG maps. The results suggest that the SL ECG may provide an alternative for noninvasive mapping of cardiac electrical activity.

Body surface Laplacian mapping of atrial depolarization in healthy human subjects

In the present study, we report body surface Laplacian mapping of atrial depolarization under sinus rhythm in 8 healthy male subjects. For each subject, 95 unipolar disk electrodes with inter-electrode distance of 2 cm were used to record simultaneously potential ECGs over the anterior chest. The Laplacian ECG was then estimated during the P wave using a novel spline Laplacian technique. The body surface potential map (BSPM) and body surface Laplacian map (BSLM) at different time instants or time intervals of the P wave were constructed and compared. The present results showed that the BSPMs during the P wave were characterized by the rotation of a pair of positive/negative potential distribution from right to left around the anterior torso. On the other hand, the corresponding BSLMs revealed more spatial details, including two positive activities (denoted as P1 and P2, appeared in all 8 subjects), and three negative activities (denoted as N1, N2, and N3, appeared in 7, 7, and 4 subjects, respectively). The separation of these activities and their evolving patterns were also compared and confirmed by computer simulation using a realistic geometry heart-torso model. The above findings may be directly related to the underlying activation sequence during atrial depolarization in healthy subjects, suggesting the potential clinical applications of the Laplacian ECG technique.