Thesis Format
Integrated Article
Degree
Master of Science
Program
Medical Biophysics
Supervisor
Drangova, Maria
Abstract
Atrial fibrillation (AF) is characterized by rapid irregular contraction in the upper heart chambers. Radiofrequency (RF) ablation is a curative procedure for AF burns tissues with an electrode-tipped catheter, isolating sources of AF with patterns of scar tissue. These procedures have a high (
One poorly studied contributor to AF recurrence is catheter slipping. Cardiac anatomy often forces the catheter to approach tissues at angles, where cardiac/respiratory motion pushes the catheter tip along the endocardium, creating shallow non-transmural lesions that allow for AF to persist. This work aimed to quantify the impacts of catheter slipping.
In the first part of this thesis, I describe the development and validation of a quantitative atrial tissue ablation phantom – required to study catheter slipping. In the second, I describe the use of these phantoms to study catheter slipping. Our studies demonstrated that slipping demonstrated an angle-dependent impact on lesion durability.
Summary for Lay Audience
Atrial fibrillation (AF) is the most common arrhythmia – a type of heart rhythm disorder – and is commonly treated by radiofrequency (RF) catheter ablation. In this procedure, a catheter is used to heat volumes of cardiac tissue. When heated beyond 50°C, cardiac tissue cells die, forming a volume of non-conductive scar tissue called a lesion. Forming contiguous patterns of these lesions – each through the thickness of the heart wall – electrically isolates the sources of AF, ending the arrhythmia. While ablation is an effective treatment for AF, upwards of 30% of first-time procedures fail. Many factors, such as contact stability, are known contributors to failure to isolate. Catheter slipping is one such factor that is poorly studied.
Catheters are introduced to the left atrium – the chamber of the heart that most commonly initiates AF – through a small hole in the wall separating the left and right atria. This forces the catheter to approach tissues at angles, where cardiac contraction and respiratory motion push the catheter tip along the tissue surface. Ablation during this motion spreads heating over large areas, theoretically resulting in long, shallow lesions that do not block electrical signals. Slipping is poorly studied in the literature, though known to occur, due to the difficulty of studying slipping in vivo.
The aim of this thesis was to measure the impact of slipping on ablation lesions using a novel cardiac tissue mimic and a mechanical motion stage to replicate cardiac and respiratory motion. The first chapter of this thesis describes the development and validation of our cardiac tissue mimic (phantom). The second chapter of this thesis explores the effects of slipping on ablation lesion formation.
Our studies demonstrate that our phantom matches important tissue properties – such as stiffness and friction – that are important to the dynamics of slipping. Furthermore, we show iv that our phantoms mimic cardiac ablation lesions. We also show that the impact of slipping on ablation lesion formation worsens with angle. This information could help reduce the failure rate of RF ablation, improving clinical outcomes for ablation therapy.
Recommended Citation
Chu, Victor A., "Impact of Catheter Slipping on Radiofrequency Catheter Ablation Lesion Formation: A Phantom Study" (2024). Electronic Thesis and Dissertation Repository. 9977.
https://ir.lib.uwo.ca/etd/9977
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