Date of Award

Summer 2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

Walter Besio

Abstract

The electrocardiogram (ECG) provides useful global temporal assessment of cardiac activity, but has limited spatial capabilities. Laplacian electrocardiogram (LECG) and body surface Laplacian mapping (BSLM), improvements over ECG provides high spatiotemporal distributed information about cardiac electrical activation.

This project was divided into two parts: computer simulation and human experiment. In the computer simulation, a comparison of the performance of the tripolar and bipolar as well as spline LECG and BSLMs for localizing and imaging the cardiac electrical activation has been investigated. A simple planar surface model and 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. The three estimates of LECG and BSLMs were numerically computed from the induced electrical activity in the two models. For the human experiments, we designed and developed LECG tripolar concentric ring electrode (TCE) active sensors based on the finite element algorithm "nine-point method" (NPM). The active sensors were used in an array of six by twelve (72) locations to record bipolar and tripolar LECG from the body surface over the anterolateral chest.

Results show that the TCE produce the most accurate LECG and BSLM estimation among the tripolar, bipolar and spline LECG estimators with the best performance in noise attenuation and spatial resolution. 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. 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 were used to generate isochronal maps that may some day be used by clinicians to help diagnose arrhythmias and assessing the efficacy of therapies.

Keywords. Laplacian electrocardiogram (LECG); Tripolar and bipolar concentric ring electrode (TCE and BCE); Nine-point method (NPM); Spatial selectivity; Active sensor; Body surface Laplacian mapping (BSLM); Spline LECG; Heart-torso sphere-cylinder model.

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