Purpose or Case Report: Morphological features including intramural course, high ostial location, and slit-like ostium are considered risk factors for sudden death in patients with AAOCA. Assessment of coronary blood flow at rest and hyperemia may contribute to understanding the cause of death, and to risk stratification and management. A patient-specific biomechanical 3D printed model incorporating morphological features derived from CTA was developed to quantify coronary blood flow in AAOCA.
Methods & Materials: IRB approval was obtained. Retrospectively ECG-gated CTA data from an AAOCA subject was used to segment the aortic valve, proximal aorta, and proximal right and left coronary arteries. 3D virtual models were created and exported as .STL format into CAD modeling software to create vessel walls and connections to inflow and outflow pipes. To determine material composition and properties, dog bone samples were designed per ASTM standards, printed with Agilus 30 on a CONNEX 350, and coated with Parylene (PY), polyurethane (PU) or silicone (SI) to create desirable optical and mechanical properties, and compared to fresh pediatric human aorta specimen stored in alcohol on an Instron machine to derive stress/strain curves and dynamic modulus and stiffness values. Aortocoronary pulsatile flow phantoms were designed and 3D printed with Agilus 30, Visijet S500, and silicon molding. The 3D printed model was filled with iodinated contrast, connected to a pulse duplicator, scanned using volumetric CT. Data was subjected to blinded standardized assessment for AAOCA by an expert reader, and compared to original patient dataset.
Results: Properties of Agilus 30 coated with polyurethane and silicon at 2mm thickness were found to closely mimic properties of native aorta, with tensile strength ranging between 2.4 and 3.1 MPa. A 0.8 mm intimal wall thickness (WT) for the intramural segment, 1mm WT for the mediastinal coronary, and 2mm WT for the aorta were assigned. There was complete agreement between the CT assessment of the 3D printed model and patient CTA for location of the ostia, branching pattern, ostial stenosis, presence of intramural course and length of intramurality. Dynamic cross-sectional measurements of proximal coronaries in the intramural and mediastinal segments were identical to patient CTA.
Conclusions: It is possible to transfer key morphological variables in AAOCA from CTA to a 3D printed model that can be used for biomechanical testing and flow analysis.