ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

[Ntsinjana et al., 2011], commonly treated with balloon angioplasty or stenting. Our
clinical experience showed a few cases with the flow-split between right and left
pulmonary arteries (RPA and LPA) in favour of the stenotic side, contrary to fluid
dynamics expectations. This may be explained by a mismatch in the distal pulmonary
vascular resistances (PVR) between the two lungs [Cohn et al., 1976]. Patient-specific
computational modelling could help finding an answer to clinical questions about the
fluid dynamics developed in the PAs after the surgical correction, the remodeling of the
PVR, and eventually to investigate the need for stenting the stenotic branch.
3. MATERIAL AND METHODS
3.1 Patients’ selection
Fifteen patients who had undergone ASO for the correction of TGA in their first week
of life had been retrospectively selected from our Centre database according to the
following inclusion criteria: (i) at least one cardiac MRI performed in their second
decade of life, (ii) continuity in the inflow-outflow PA balance from MR flow data, (iii)
absence of artifacts or blurring in the MR images. On the basis of clinical data, patients
were divided in 2 groups, according to the absence or the presence of pulmonary
stenosis. The former group included 5 patients, and was used as a Control group; the
latter included 10 patients (Stenotic group). No pulmonary hypertension was reported in
the selected patients. Average age at the scan was 15 years (9-18), while the average
body surface area index (BSA) was 1.64 (1.1-2). Informed consent for research use was
given by the patients or by their parents in case of minor age.
3.2 Geometry reconstructions
The reconstruction of the 3D pulmonary tree was performed post-processing MR
patients’ data with the commercial software Mimics (Materialise, Leuven, Belgium).
The models included the proximal RPA and LPA (outlets) cut before further branching
and the portion of MPA (inlet) distal to the pulmonary valve. Following a mesh
sensitivity analysis, a tetrahedral grid with 0.5 mm element size was chosen.
Fig. 1 – Reconstruction of one patient’s pulmonary tree (left), and model prepared for the CFD analysis
with the tetrahedral mesh.