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

心房颤动（AF）是一种常见的心脏疾病，约占英国人口的2%。当患者患有心房颤动时，“心房”（心脏的上腔）停止跳动。这会改变心律，使心脏跳动迅速而不规律。这是因为通常控制心房的电信号受到干扰。房颤通常以短暂的“停止-开始”发作开始，持续数分钟至数小时。逐渐地，这些发作变得越来越长，越来越频繁。房颤是一种严重的疾病，可导致中风和心力衰竭。房颤患者更容易住院，预期寿命较短，并可能出现严重症状。用于预防房颤的药物通常是无效的，而且可能是危险的，因此，消除或减少药物治疗需求的程序是非常重要的。“导管消融”（CA）是一种用于治疗房颤的“锁眼”治疗方法，包括烧灼导致房颤的心脏部分。为了有效，烧灼必须在心房壁的全厚度上形成疤痕。心房壁的厚度从1mm以下到8mm以上不等，因此形成有效疤痕所需的烧灼量差异很大。CA治疗早期房颤（“阵发性房颤”）对高达90%的患者有效，而对于那些持续时间较长的“持续性”房颤，总体成功率较低（60 - 70%），多达一半的患者需要多次手术。房颤最严重的并发症是过度烧灼导致心房壁、其他心脏结构甚至心脏外结构受损。这些并发症更可能发生在心房壁最薄的地方。每个手术都有大约5%的并发症风险，因此迫切需要提高其安全性并减少需要重复手术的患者数量。心房壁厚度的变化是房颤治疗失败的重要原因。没有工具可以测量整个心房的壁厚。这种工具将为作业者提供有关在不同区域应用的必要和安全烧灼量的信息。我们已经开发了一种通过计算机断层扫描（CT或“CAT”）测量心房壁厚度的技术，该技术可以提供三维心房壁厚度图。我们认为，在手术过程中向操作者提供有关心房壁厚度的信息，可以更安全、更有效地治疗房颤。该工具还可以帮助我们了解导致房颤的过程。实验室实验的证据表明，心脏的电特性随着心房壁厚度的变化而变化。我们有通过测量心脏内部电信号来测试这些电学特性的经验。通过将这些测量结果与心房壁厚度进行比较，我们将能够了解心房壁厚度如何影响心脏的电特性，并深入了解房颤的原因。我们正在计划进行两项研究。第一项研究将包括不计划进行CA手术的房颤患者。我们将对他们的心脏进行CT扫描，然后收集和监测临床信息。这将使我们了解心房壁厚度变化对临床特征和病情进展的影响。第二项研究将包括计划进行CA手术的房颤患者。我们将对病人的心脏进行CT扫描。在他们的CA过程中，我们将测量他们心脏中的电信号，并检查这些测量是如何受到壁厚变化的影响的。我们的工作有可能形成一个工具的基础，以提高AF的CA程序的安全性和有效性。这样的工具可以在世界各地使用。我们的工作也将解决一些关于房颤原因的许多悬而未决的问题。

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.