MRI of Left Atrial Hemodynamic Disorders in Atrial Fibrillation

Project Summary/Abstract: The three therapeutic goals of AF management are rhythm control, rate control, and stroke prevention. The attributable risk of stroke from AF increases progressively with age. Anticoagulation therapies are effective, but regrettably associated with non-negligible complications of major bleeding (~3% per year). This is because currently used risk profiles such as the CHA2DS2-VASc score are based on upstream clinical factors (age, sex, diabetes, etc.) rather than individual physiologic mechanisms implicated in left atrium (LA) or LA appendage (LAA) thrombus formation. As a first step towards personalizing anticoagulation therapy, this application seeks to develop and validate a new imaging test for establishing a risk stratification system based on individual 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, contractile function, geometry, and blood stasis - one component of Virchow’s triad - as a contributor to atrial thrombogenesis. This is supported by transesophageal echocardiography (TEE) studies which reported that decreased peak emptying LAA flow velocities and the presence of atrial flow stasis are risk factors for stroke in AF. However, TEE is invasive and can only assess isolated components (e.g. peak emptying LAA blood velocities) of the 3D LA/LAA blood flow dynamics inside a complex cardiac chamber (geometry, in-flow through 4 pulmonary veins, rapid mitral-valve outflow). Cardiovascular MRI is an excellent modality for imaging atrial hemodynamics. 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