Non-invasive Estimation of Pressure Drop Across Aortic Coarctations: Validation of 0D and 3D Computational Models with In Vivo Measurements.

Abstract

Blood pressure gradient ( <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Δ</mi> <mi>P</mi></mrow> </math> ) across an aortic coarctation (CoA) is an important measurement to diagnose CoA severity and gauge treatment efficacy. Invasive cardiac catheterization is currently the gold-standard method for measuring blood pressure. The objective of this study was to evaluate the accuracy of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Δ</mi> <mi>P</mi></mrow> </math> estimates derived non-invasively using patient-specific 0D and 3D deformable wall simulations. Medical imaging and routine clinical measurements were used to create patient-specific models of patients with CoA (N = 17). 0D simulations were performed first and used to tune boundary conditions and initialize 3D simulations. <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Δ</mi> <mi>P</mi></mrow> </math> across the CoA estimated using both 0D and 3D simulations were compared to invasive catheter-based pressure measurements for validation. The 0D simulations were extremely efficient ( <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>∼</mo></math> 15 s computation time) compared to 3D simulations ( <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>∼</mo></math> 30 h computation time on a cluster). However, the 0D <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Δ</mi> <mi>P</mi></mrow> </math> estimates, unsurprisingly, had larger mean errors when compared to catheterization than 3D estimates (12.1 ± 9.9 mmHg vs 5.3 ± 5.4 mmHg). In particular, the 0D model performance degraded in cases where the CoA was adjacent to a bifurcation. The 0D model classified patients with severe CoA requiring intervention (defined as <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Δ</mi> <mi>P</mi></mrow> </math> <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>≥</mo></math> 20 mmHg) with 76% accuracy and 3D simulations improved this to 88%. Overall, a combined approach, using 0D models to efficiently tune and launch 3D models, offers the best combination of speed and accuracy for non-invasive classification of CoA severity.