Abstract

Computational fluid dynamics (CFD) can have a complementary predictive role alongside the exquisite visualization capabilities of 4D cardiovascular magnetic resonance (CMR) imaging. In order to exploit these capabilities (e.g., for decision-making), it is necessary to validate computational models against real world data. In this study, we sought to acquire 4D CMR flow data in a controllable, experimental setup and use these data to validate a corresponding computational model. We applied this paradigm to a case of congenital heart disease, namely, transposition of the great arteries (TGA) repaired with arterial switch operation. For this purpose, a mock circulatory loop compatible with the CMR environment was constructed and two detailed aortic 3D models (i.e., one TGA case and one normal aortic anatomy) were tested under realistic hemodynamic conditions, acquiring 4D CMR flow. The same 3D domains were used for multi-scale CFD simulations, whereby the remainder of the mock circulatory system was appropriately summarized with a lumped parameter network. Boundary conditions of the simulations mirrored those measured in vitro. Results showed a very good quantitative agreement between experimental and computational models in terms of pressure (overall maximum % error = 4.4% aortic pressure in the control anatomy) and flow distribution data (overall maximum % error = 3.6% at the subclavian artery outlet of the TGA model). Very good qualitative agreement could also be appreciated in terms of streamlines, throughout the cardiac cycle. Additionally, velocity vectors in the ascending aorta revealed less symmetrical flow in the TGA model, which also exhibited higher wall shear stress in the anterior ascending aorta.

Highlights

  • Gathering insight into local hemodynamics of patients with congenital heart defects is crucial for improving general understanding of the physiology of such diseases, often associated with complex anatomies and intricate “plumbing,” and for refining assessment of individual patients

  • Excellent qualitative agreement was verified between the cardiovascular magnetic resonance (CMR) and the computational fluid dynamics (CFD) data (Figures 4 and 5): the CFD simulation was able to reproduce the same flow jet impinging at the top of the the great arteries (TGA) aortic root wall, and the surrounding whirls visible in the 4D flow images

  • This study presented methodological considerations with regards to setting up a CMR-compatible mock circulatory system

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Summary

Introduction

Gathering insight into local hemodynamics of patients with congenital heart defects is crucial for improving general understanding of the physiology of such diseases, often associated with complex anatomies and intricate “plumbing,” and for refining assessment of individual patients In this context, the role of cardiovascular magnetic resonance (CMR) imaging is unquestionable, and four dimensional phase-contrast magnetic resonance (4D PCMR) flow imaging, in particular, has been shown to provide exquisite data. 4D PCMR has been proven helpful in assessing systemic-to-pulmonary collateral flow in Fontan physiology [1] or evaluating blood flow characteristics after repair of tetralogy of Fallot [2, 3] This imaging technique, providing a 3D flow map of the blood circulation, can replace the attempts of computational fluid dynamics (CFD) simulations to explain complex hemodynamic scenarios. This is where CFD analyses can have a complementary, and potentially clinically relevant, role

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