A numerical study of the hemodynamic effect of the aortic valve on coronary flow.

During diastole, coronary perfusion depends on the pressure drop between the myocardial tissue and the coronary origin located at the aortic root. This pressure difference is influenced by the flow field near the closing valve leaflets. Clinical evidence is conclusive that patients with severe aortic stenosis (AS) suffer from diastolic dysfunction during hyperemia, but show increased coronary blood flow (CBF) during rest. Transcatheter aortic valve implantation (TAVI) was shown to decrease rest CBF along with its main purpose of improving the aortic flow and reducing the risk of heart failure. Physiological or pathological factors do not provide a clear explanation for the increase in rest CBF due to AS and its decrease immediately after TAVI. In this manuscript, we present a numerical study that examines the impact of AS and TAVI on CBF during rest conditions. The study compares the hemodynamics of five different 2D numerical models: a baseline "healthy valve" case, two AS cases and two TAVI cases. The analysis used time-dependent computational fluid-structure interaction simulations of blood flow in the aortic root including the dynamics of the flexible valve leaflets and the varying resistance of the coronary arteries. Despite its simplifications, our 2D model succeeded to capture the major effects that dominate the hemodynamics in the aortic root and to explain the hemodynamic effect that leads to the changes in CBF found in in vitro and clinical studies.