Virtual Therapy Planning of Aortic Valve Replacement: The Effect of Different Valve Sizes at Rest and during Stress

Background: Surgical aortic valve replacement (AVR) aims to normalize left ventricular pressure and blood flow profiles in the ascending aorta. The impact of different valve sizes on pressure gradient and flow profiles and possible differences between resting and physical stress condition are not yet known for the individual patient anatomy. The present study aims to demonstrate a methodological approach to preoperatively predict the hemodynamic effects of different valve sizes at rest and under simulated physical stress condition on aortic hemodynamics after AVR by computational fluid dynamic (CFD) based virtual therapy planning.

Methods: In 10 patients with severe aortic valve stenosis (AS) preoperative magnetic resonance imaging (MRI) data were used for performing virtual AVR (CFD based on preoperative 4D flow MRI data) with a biological prosthesis, which was also actually inserted surgically. Additionally, simulations were performed using one valve size larger and one valve size smaller. Simulations using preoperative left ventricular outflow tract stroke volumes were used for assessing hemodynamic data at rest and an increase of 25% was used for simulating physical stress condition. Hemodynamic parameters such as maximum velocity (Vmax) and pressure gradient (DPmax) and aortic blood flow profiles were calculated for each valve size and physical stress was simulated.

Results: The different valve sizes led to significantly different velocities across the left ventricular outflow tract and none of the valves rendered velocities comparable to healthy control data. Stress simulation led to a significant increase in gradient across the aortic valve, but no changes in blood flow profiles. The comparison between the increase from rest to stress revealed that the smaller the inserted valve, the higher the mean increase of Vmax and DPmax (Vmaxrest vs. stress 0.95/1.0 /1.15 m/s and DPmax rest vs. stress 15/17.6/22.8 mm Hg for the larger/actual/smaller valve, respectively). When compared with a healthy cohort, pathological blood flow profiles in the ascending aorta persist after AVR (p < 0.001) and did not change significantly under simulated physical stress.

Conclusion: The effects of prosthesis size related hemodynamic changes at rest and under physical stress can be simulated based on preoperative data only. The methodological approach presented here holds the potential to preoperatively identify patients at risk of relevant stress induced patient prosthesis mismatch. Further validation studies are necessary.

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Artikel online veröffentlicht:
13. Februar 2024