Focus Session 3: 3D+: State-of-the-Art Cardiac Visualization - Presentation of 3D Models
10 - MRI Based 3D Printed Model for Planning Transcatheter Device Closure of a Right Ventricular Outflow Tract Pseudoaneurysm in a Patient with Tetralogy of Fallot.
Saturday, February 15, 2020
10:20 AM – 11:00 AM
Location: Canary 2
Description of Clinical Presentation: A 20 year-old female with repaired tetralogy of Fallot (TOF) presented for evaluation of a right ventricular outflow tract (RVOT) pseudoaneurysm. Her surgical history consisted of complete TOF repair with a transannular patch as an infant, followed at 10 years of age by a surgical RVOT revision using a 24 mm pulmonary homograft. CMRI confirmed a large pulsatile pseudoaneurysm with mural thrombus arising from the proximal homograft patch. Options for intervention included surgical excision and transcatheter device closure. Feasibility of device closure was uncertain given the complex anatomy of the defect orifice and the potential interplay between a device, RVOT, and the homograft valve. Creation of a 3D printed model allowed for bench testing of multiple device occlusion strategies. A 28 mm atrial septal occluder was deployed in the model and effectively isolated the pseudoaneurysm without causing RVOT obstruction or interfering with the valve annulus. Based on these findings, the patient underwent successful transcatheter device closure of the pseudoaneurysm using a 28 mm device. Use of the printed 3D model allowed us to avoid surgery, and likely decreased the morbidity and cost of catheterization by decreasing the length of the procedure, the amount of radiation and contrast exposure, and the need for in-vivo testing of multiple devices.
Diagnostic Techniques and Their Most Important Findings: Cardiac MRI was performed on a 1.5T Scanner (Philips, Best, the Netherlands) using a standard TOF protocol. The pseudoaneurysm was imaged in axial and sagittal oblique planes using steady state free precession, T1-weighted black blood, gadolinium enhanced MRA, and delayed enhancement sequences. These demonstrated a 4.5 x 5.5 x 6 cm pulsatile pseudoaneurysm arising from the RVOT patch proximal to the homograft valve. The pseudoaneurysm was surrounded by fibrous tissue, and contained mural thrombus. The RVOT and homograft were unobstructed, with only mild (7%) homograft valve regurgitation. There was right ventricular enlargement (150ml/m2), and the right and left ventricular ejection fractions were 43% and 53%, respectively.
A 3D model was created from the MRA using commercially available software (Materialise, Leuven, Belgium) using the “hollow shell” method. First, the blood pool was segmented. Then, a 1.25 mm shell was created along the outer surface of the blood pool. The blood pool segmentation was then removed, leaving a hollow shell with an inner surface representing the endocardial surface of the heart and the vessel walls. Colored rings were created along the homograft valve annulus and the pseudoaneurysm orifice to aid in visualization. This model was then printed in actual size using a rigid material (Vero Clear, Objet Eden 260V Polyjet Printer, Stratysys, Eden Prarie MN). The inferior portion of the right ventricle and the outer half of the pseudoaneurysm were removed to allow for device access and visualization of the areas of interest.