New insights in magnetic resonance imaging evaluation of aortic valve hemodynamics

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Aortic stenosis (AS) is defined as the pathological narrowing of the aortic valve. It is the most frequent valvular heart disease and the most frequent cardiovascular disease after systemic hypertension and coronary artery disease in Europe and North America. Currently, cardiac catheterization and Doppler echocardiography are the most frequently used methods for the determination of aortic stenosis severity. However, cardiac catheterization has significant technical limitations and it is an invasive technique that may place the patient at unnecessary risk while Doppler echocardiography has several practical and theoretical limitations that limit its applicability in around 20% of the patients with aortic stenosis. In a recent in vitro study, we developed, using particle image velocimetry (PIV), a new accurate method to determine the severity of aortic stenosis from the velocity field. Although very promising, the applicability of this method was limited in vivo because PIV requires transparent structures. However, this is not the case for magnetic resonance phase contrast (MR PC). In fact, MR PC is a powerful non-invasive, non-ionizing technique, able to investigate the velocity field through human heart valves. The objective of the present study is, therefore, to determine in vitro and in vivo the feasibility and the accuracy of our new method applied to the velocity field measured by MR PC. Furthermore, we will investigate the ability of MR PC to compute turbulence characteristics downstream of an aortic stenosis. We expect that the results of this project will have a significant impact on the clinical evaluation of the severity of aortic stenosis.