MRI of Left Atrial Hemodynamic Disorders in Atrial Fibrillation

项目摘要/摘要：超过200万美国人患有心房颤动（AF），主要是 影响到老年人（平均年龄> 65岁），每年花费超过60亿美元。三种治疗方法 心房纤颤（AF）管理的目标是节律控制、心率控制和中风预防。 不幸的是，由临床特征指导的标准抗凝治疗与不可忽略的 大出血并发症（每年约3%）。这是因为目前使用的风险简介 基于上游临床因素（年龄、性别、糖尿病等）而不是个人的生理因素 涉及左心房（LA）或左心房附件（LAA）血栓形成。这种高风险高回报的 一项申请寻求开发一种新的成像测试，该测试是建立风险分层系统所需的 基于与血栓形成有关的生理因素。 这项研究的科学前提是基于对已知的非侵入性成像的日益增长的兴趣。 AF中心房病理学参数：LA/LAA体积、功能、几何结构和血瘀- Virchow三联征-作为心房血栓形成的贡献者。这是由经食管支持的 超声心动图（TEE）研究报告，左心耳排空峰值流速降低， 心房血流停滞的存在是房颤患者卒中的独立危险因素。 评估AF中的LA/LAA血流的诊断成像模式具有许多局限性。首先，TEE只能评估 3D LA/LAA血流动力学的孤立成分（例如，峰值排空LAA流速） 复杂心腔（复杂LA/LAA几何结构，流入4条肺静脉，二尖瓣快速流出 流动）。其次，TTE是一种侵入性手术，因此与不可忽视的并发症相关。 通过利用压缩感知（CS）前所未有的成像速度，该应用程序旨在 进一步推进心血管MRI，并制定15分钟MRI方案，以全面评估 AF中血流动力学（LA和LAA流量、功能和容量）的持续性和逐搏变化。 该应用的具体目标是：（1）联合收割机高加速的双文4D流和实时 采用CS的电影和流式MRI方法，（2）在患者特定模型中验证新的心房MRI方案， 脉动流泵在模拟规则和不规则的节奏条件下，和（3）测试是否有新的心房 MRI方案在AF患者中产生可重复的结果。 与传统的心血管MRI方案不同，这种快速全面的心房MRI方案（15分钟）是一种 MRI技术的一个重大进步，因为它消除了对患者屏气的要求，改善了 扫描效率高，简化了扫描操作，并且不需要钆基造影剂 局这些特征是筛选工具的重要先决条件。我们的提议影响很大 潜在的，因为如果成功，它将提供一个快速的，非对比MRI方案，用于表征心房肌 AF复杂环境中的血流动力学。该建议的长期临床目标是个性化 抗凝治疗和降低AF患者的出血风险。

Project Summary/Abstract: Over 2 million Americans suffer from atrial fibrillation (AF), predominantly affecting the elderly (mean age > 65 years), with over $6 billion expended annually. The three therapeutic goals of atrial fibrillation (AF) management are rhythm control, rate control, and stroke prevention. Unfortunately, standard anticoagulation therapies guided by clinical profiles are associated with non-negligible complications of major bleeding (~3% per year). This is due to the fact that currently used risk profiles are based on upstream clinical factors (age, sex, diabetes, etc.) rather than individual physiologic factors implicated in left atrium (LA) or LA appendage (LAA) thrombus formation. This high-risk, high-reward application seeks to develop a new imaging test that is needed for establishing a risk stratification system based on physiologic factors implicated in thrombus formation. The scientific premise of this study is based on a growing interest in non-invasive imaging of known parameters of atrial pathology in AF: LA/LAA volume, function, geometry, and blood stasis - one component of Virchow’s triad - as a contributor to atrial thrombus formation. This is supported by transesophageal echocardiography (TEE) studies which reported that decreased peak emptying LAA flow velocities and presence of atrial flow stasis are independent risk factors for stroke in AF. While TEE is a widely available diagnostic imaging modality to asses LA/LAA flow in AF, it has many limitations. First, TEE can only assess isolated components (e.g. peak emptying LAA flow velocities) of the 3D LA/LAA blood flow dynamics inside a complex cardiac chamber (complex LA/LAA geometry, in-flow through 4 pulmonary veins, rapid mitral-vale out flow). Second, TTE is an invasive procedure and is, therefore, associated with non-negligible complications. By leveraging an unprecedented imaging speed from compressed sensing (CS), this application seeks to further advance cardiovascular MRI and develop a 15-min MRI protocol for a comprehensive assessment of persistent and beat-to-beat variation in hemodynamics (LA and LAA flow, function, and volume) in AF. The specific objectives of this application are: (1) to combine highly-accelerated dual-venc 4D flow and real-time cine and flow MRI methods with CS, (2) to validate a new atrial MRI protocol in patient-specific models with a pulsatile flow pump in simulated regular and irregular rhythm conditions, and (3) to test whether a new atrial MRI protocol produces repeatable results in patients with AF. Unlike conventional cardiovascular MRI protocols, this rapid comprehensive atrial MRI protocol (15 min) is a major step forward in MRI technology, because it eliminates demands on patients for breath holding, improves scan efficiency, simplifies scan operation, and does not require gadolinium-based contrast agent administration. These features are important pre-requisites for a screening tool. Our proposal has high impact potential because, if successful, it will deliver a rapid, non-contrast MRI protocol for characterization of atrial hemodynamics in the complex setting of AF. The long-term clinical goal of this proposal is to personalize anticoagulation therapy and reduce the risk for bleeding in patients with AF.