Date of Award

Spring 2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

Committee Director

Christian Zemlin

Committee Member

Shu Xiao

Committee Member

Michel Audette

Committee Member

Jiang Li

Abstract

Cardiac ablation for the treatment of cardiac arrhythmia is usually performed by heating tissue with radio-frequency (RF) electrical currents to create conduction-blocking lesions in order to stop the propagation of electrical waves. Problems associated with RF ablation are recurrence of arrhythmias after successful treatments, tissue loss beyond the targeted tissue, long duration of the ablation procedure, and thermal side effects including thrombus formation that may lead to stroke. Here, we propose a new, non-thermal ablation method using nanosecond pulsed electric fields (nsPEFs) with better-controlled ablation volume, shorter procedure time, and no thermal side effects. We demonstrate that we can create non-conductive transmural lesions using different electrode configurations. We also develop a numerical model of nsPEF ablation, which allows us to estimate the critical electric field which leads in cardiac tissue and helps to provide a guideline for clinical tissue ablation.

Our experimental model is a Langendorff-perfused rabbit heart. The heart is placed in a life-support system, and optical mapping is performed to study its electrical activity. We further developed the capability to apply short sequences of nanosecond pulses to tissue through pairs of customized electrodes. In order to characterize the 3D geometry of an ablated volume, we have adopted propidium iodide and TTC staining in conjunction with tissue sectioning. Our results obtained by optical mapping data and PI/TTC stained tissue show that fully transmural lesions can be obtained faster and with better control over the ablated volume than in conventional (RF) ablation, in the absence of thermal side effects.

In order to aid nsPEF ablation planning, we used the COMSOL finite element software to create a model of the electric field distribution in cardiac tissue, which has a complex anisotropic architecture, for different electrode configurations. The experimental and numerical results are consistent and suggest a critical electric field strength of 3kV/cm for the death of cardiac tissue. This threshold obtained by the numerical model can function as a guideline for future clinical nsPEF treatment of atrial fibrillation.

In summary, we have developed nsPEF ablation for the treatment of cardiac arrhythmia to provide better control over the ablated volume than conventional (RF) ablation, to reduce procedure time, and to avoid thermal side effects. Our ultimate goal is to bring this technology to the clinical practice.

DOI

10.25777/kn1z-b503

ISBN

9781321843422

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