Background: Patient prosthesis mismatch after aortic valve replacement (AVR) can be a serious burden for the left ventricle leading to increased morbidity and mortality. Computational simulation of surgical procedures can be used to predict postoperative hemodynamics and might be a tool to improve individual treatment planning and therapy outcome. This study aims to demonstrate a methodological approach to simulate the influence of different biological AVR sizes on postoperative hemodynamics (pressure gradients and aortic blood flow profiles) under resting and stress conditions.  

Methods: Computational simulation of hemodynamic outcome after biological AVR was performed for 10 patient anatomies using a computational fluid dynamics (CFD) approach based on real preoperative anatomic and hemodynamic data derived from cardiac magnet resonance imaging (MRI) of patients with severe aortic valve stenosis. For each patient anatomy, 3 different AVR sizes were analyzed. Physical stress was simulated based on a 0D-stress model that was informed by a previous meta-analysis and existing literature. Hemodynamic parameters such as maximum velocity (Vmax) and pressure gradient (DPmax) and aortic blood flow profiles were calculated for each AVR size under resting and stress conditions. 

Results: The computational simulations showed, like expected, that the smaller the inserted AVR size, the higher Vmax und DPmax, both at rest and under physical stress (r>0.7, p≤0.005; for each parameter). The comparison between rest and stress simulation revealed that the smaller the inserted valve, the higher the mean difference of Vmax and DPmax (Vmax_{rest vs. stress} 0.95/1.0 /1.15 m/s and DPmax_{rest vs. stress} 15/17.6/22.8 mmHg for the large/medium/small AVRs, respectively). Moreover, in 3 of 10 patient anatomies (30%), the stress simulation revealed a disproportionately high increase in DPmax, although simulations at rest predicted acceptable postoperative results (percent increase 200% in n=7 vs 600% in n=3). All patient simulations rendered abnormal blood flow profiles in the ascending aorta after AVR irrespective of aortic valve size and stress condition.

Conclusion: The methodological approach to include physical stress conditions into computational AVR planning holds the potential to preoperatively identify patients at risk for patient prosthesis mismatch. Further validation studies are necessary.