4D Flow vCath: virtual Catheter for assessing hemodynamics in bicuspid aortic valve

Bicuspid Aortic valve (BAV) is the most common congenital heart disease with an estimated prevalence of 1-2% in the general population and is frequently associated with severe aortopathy (aortic dilatation, aneurysm, dissection) where surgery remains the only treatment. Nevertheless, pathogeneses of aortopathy in BAV patients remains unknown and considerable debate exists regarding interventional timing and the type or extent of surgery. 4D Flow MRI studies by our group and others provide evidence that BAV-mediated changes in aortic hemodynamics significantly associate with aortopathy phenotype and aortic wall degeneration on tissue histopathology, suggesting a physiologic mechanism by which valve abnormalities can influence the development of BAV aortopathy. 4D flow MRI is now used as a clinical tool in diagnostic MRI exams at Northwestern University (NW) for patients with aortic valve disease such as BAV. Over the past 6 years, our group has assembled one of the largest databases world-wide with over 1200 patients with aortic 4D flow MRI exams (>800 BAV; n=200 with 1-5 year follow-up) and wide-age healthy controls (n=140, 9-87 years). However, current aortic 4D flow data analysis frameworks have limitations: 1) transvalvular pressure gradients ' an important clinical marker of valve disease severity' is not yet well established; 2) analysis adopts a 2D plane approach not fully utilizing its 4D nature (3D + time over the cardiac cycle); 3) manual, resulting in cumbersome, time-consuming analysis, hindering reproducibility and clinical translation. To address these challenges, we have recently developed a novel noninvasive 4D Flow virtual Catheter (vCath) technique from 4D Flow MRI that mimics the well-known invasive Catheter approach. vCath utilizes the full 4D flow MRI information for flexible quantification of different hemodynamic metrics and offers a high degree of automation. Results from the vCath pilot study showed its feasibility to identify longitudinal changes in different volumetric flow indices (kinetic energy, energy loss) in 44 BAV patients during 2-year follow-up. This proposal aims to employ our uniquely large 4D flow MRI database to further develop our novel noninvasive 4D Flow vCath technique to extend the utility of 4D Flow MRI to simultaneously assess transvalvular pressure gradients and advanced 3D time-resolved aortic hemodynamics in BAV towards better prediction of BAV outcome.