Abstract

Coarctation of the aorta (COA) is an obstruction of the aorta and is usually associated with bicuspid and tricuspid aortic valve stenosis (AS). The main objective of this work is to understand the hemodynamic of COA from different perspectives. This was performed using a global approach including: numerical simulations, mathematical lumped parameter modeling and experimental measurements.
Numerous investigations pointed to a relationship between the genesis and the progression of cardiovascular disease and the locally irregular flow occurring at the diseased zone. Therefore, to examine the relationship between arterial disease and hemodynamics conditions, a joint experimental and numerical investigation was performed to understand physics of fluid flow of COA.
When COA coexists with AS, the left ventricle faces a double hemodynamic load: a valvular load plus a vascular load. First, a formulation describing the instantaneous net pressure gradient through COA was introduced and the predictions compared to in vitro results. The model was then used to determine left ventricular work induced by coexisting aortic stenosis and coarctation with different severities. The suggested model can be used to guide the choice of optimal operative procedure (aortic valve replacement and/or coarctation repaired surgery) and to predict the potential outcome for such patients.
Early detection and accurate estimation of COA severity is the most important predictor of successful long-term outcome. However, current clinical parameters used for the evaluation of the severity of COA have several limitations. In this study, first, we evaluated the limitations of current existing parameters (Catheter trans-COA pressure gradients and Doppler echocardiographic trans-COA pressure gradients) for the evaluation of the severity of COA. Then, we suggested a new approach based on COA Doppler velocity index and COA effective orifice area capable of predicting more accurately the severity of COA. An original in-vitro study was performed using a mock flow circulation model with different COA severities and various aortic valve conditions under different flow rates.
In conclusion, this study investigated the flow dynamics of COA and development of a lumped parameter model, based on non-invasive measurements, capable of accurately investigating the impact of coexisting AS and COA on left ventricular workload. In addition, this study proposed two innovative approaches to evaluate the severity of COA correctly.