Determination of left atrial wall thickness and its influence on electroanatomic properties in the human atrium

点击翻译按钮获取中文摘要

Atrial fibrillation ('AF') is a common heart condition affecting around 2% of the UK population. When a patient suffers from AF the 'atria' (the upper chambers in their heart) stop pumping. This alters the heart rhythm, and can make the heart beat quickly and erratically. It happens because the electrical signals that normally control the atria are disturbed. AF usually begins as short 'stop - start' episodes lasting minutes to hours. Gradually these episodes become longer and occur more frequently.AF is a serious condition that can cause stroke and heart failure. Patients with AF are more likely to be admitted to hospital, have a lower life expectancy and can experience severe symptoms. Drugs designed to prevent AF are frequently ineffective and can be dangerous, so procedures that negate or reduce the need for drug treatment are of great importance.'Catheter ablation' (CA) procedures are 'keyhole' procedures designed to treat AF, which involve cauterisation of parts of the heart responsible for AF. To be effective, the cauterisation must create a scar that crosses the full thickness of the atrial wall. The thickness of the atrial wall varies from under 1mm to over 8mm, so the amount of cauterisation required to form an effective scar varies significantly. CA treatment of the early form of AF ('paroxysmal AF') is effective in up to 90% of patients, while for those with the longer lasting 'persistent' form, the overall success rate is lower (60 - 70%) and up to half of patients require multiple procedures. The most serious complications of CA result from excessive cauterisation that damages the atrial wall, other heart structures or even structures outside the heart. These complications are more likely where the atrial wall is thinnest. Each procedure carries approximately a 5% risk of complication, so there is an urgent need to improve their safety and reduce the number of patients requiring repeat procedures.Variation in the atrial wall thickness is a significant cause of CA treatment failure. No tool exists to measure wall thickness throughout the atrium. Such a tool would provide the operator with information regarding the necessary - and safe - amount of cauterisation to apply in different areas. We have developed a technique to measure atrial wall thickness from computed tomography (CT or 'CAT') scans which provides a map of atrial wall thickness in three dimensions. We believe that providing the operator with information regarding wall thickness during procedures would allow safer and more effective treatment of AF. This tool may also help us to understand the processes that cause AF. Evidence from laboratory experiments suggests that electrical properties of the heart change with atrial wall thickness. We have experience of testing these electrical properties by measuring electrical signals inside the heart. By comparing these measurements with atrial wall thickness we will be able to understand how atrial wall thickness affects the electrical properties of the heart and gain insights into the causes of AF. We are planning two studies. The first study will include patients with AF who are not planned for CA procedures. We will perform a CT scan of their heart and then collect and monitor clinical information. This will allow us to understand the effect of changes in atrial wall thickness on the clinical features and progression of the condition. The second study will include AF patients who are planned for CA procedures. We will perform a CT scan of the patient's heart. At the time of their CA procedure, we will measure electrical signals in their heart and examine how these measurements are affected by variations in wall thickness. Our work has the potential to form the basis for a tool to improve the safety and effectiveness of CA procedures for AF. Such a tool could be used around the world. Our work will also address some of the many outstanding questions about the causes of AF.