Faculty Bibliography

Rapid prototyping is quickly gaining utility in various complex forms of CHD. In properly selected cases, these printed models provide detailed anatomical understanding that help guide potential surgical and cardiac catheterisation interventions. We present a case of a tunnel-like ventricular septal defect referred for surgical repair, where the decision to obtain a three-dimensional printed model helped in better understanding of the anatomy, leading to delaying, and hopefully avoiding altogether, surgical repair.

We report an unusual presentation of a large left atrial myxoma in an eight-year-old girl who presented with the sudden onset of chorea. This case illustrates the fact that the presentation of chorea in nonendemic areas for rheumatic fever should raise suspicion for a myxoma. The chorea resolved soon after removal of the myxoma, supporting the hypothesis of an immune-mediated mechanism, or manifestation of paraneoplastic syndrome secondary to the myxoma.

Rapid prototyping facilitates comprehension of complex cardiac anatomy. However, determining when this additional information proves instrumental in patient management remains a challenge. We describe our experience with patient-specific anatomic models created using rapid prototyping from various imaging modalities, suggesting their utility in surgical and interventional planning in congenital heart disease (CHD). Virtual and physical 3-dimensional (3D) models were generated from CT or MRI data, using commercially available software for patients with complex muscular ventricular septal defects (CMVSD) and double-outlet right ventricle (DORV). Six patients with complex anatomy and uncertainty of the optimal management strategy were included in this study. The models were subsequently used to guide management decisions, and the outcomes reviewed. 3D models clearly demonstrated the complex intra-cardiac anatomy in all six patients and were utilized to guide management decisions. In the three patients with CMVSD, one underwent successful endovascular device closure following a prior failed attempt at transcatheter closure, and the other two underwent successful primary surgical closure with the aid of 3D models. In all three cases of DORV, the models provided better anatomic delineation and additional information that altered or confirmed the surgical plan. Patient-specific 3D heart models show promise in accurately defining intra-cardiac anatomy in CHD, specifically CMVSD and DORV. We believe these models improve understanding of the complex anatomical spatial relationships in these defects and provide additional insight for pre/intra-interventional management and surgical planning.

INTRODUCTION Melody transcatheter pulmonary valve (TPV) implantation is frequently considered in patients with Right Ventricle Outflow Tract (RVOT) conduit obstruction, as a minimally invasive alternative to open-heart surgery.1 However, TPV implantation is associated to a risk of coronary artery (CA) compression.2 In this work, an innovative Finite Element (FE) balloon dilatation model has been built to predict CA compression in order to avoid patient exposure to unnecessary risks. In this study four patients, who underwent MRI or CT in anticipation to receive TPV, were considered. Images were segmented to generate 3D models. A balloon dilatation FE simulation was implemented for each of the models. The balloon was represented as a deformable 3D cylinder positioned at the center of mass at the narrowest point of the conduit lumen. Then, radial displacement was applied uniformly until the balloon reached the dimension of a fully inflated balloon. A linear elastic constitutive model was chosen to describe all the vasculature, and parameters for it were retrieved from literature. A frictionless contact algorithm was implemented between the balloon and the conduit and between the conduit and the surrounding structures. The results of the simulations allowed analysis of important parameters that could play an active role in the determination of the angioplasty procedure outcome in terms of CA compression. MATERIALS AND METHODS Patient-Specific Models Patients who were candidates for Transcatheter Pulmonary Valve Replacement (TPVR) were included (n = 4). The investigators from Tandon School of Engineering were blinded to the results of the procedure. Each patient underwent pre-catheterization Magnetic Resonance Imaging (MRI) or Computerized Tomography scan (CT scan) and patient-specific models were created from these images using Mimics (Materialize, Belgium), Meshmixer (Autodesk, California) and Cubit (C Sim Software, Utah) software. Each model was constituted by the components of the cardiovascular system affected by the angioplasty procedure, the pulmonary artery (PA), the aorta and the coronary arteries (CA). A 60 mm long segment of PA was selected from the right ventricle outflow tract (RVOT) to the PA bifurcation so that the conduit was included. Similarly, a 60 mm long segment of aorta was selected from the aortic root to the aortic arch. Finally, left and right CAs were selected where visible. Our protocol required the CA branches to be at least 20 mm in length to be included in the study. The model thus obtained, was manipulated using 3D CAD tools available in Meshmixer to smooth the model and to generate a 3D hollow geometry from a model representing only the blood pool. The hollowing procedure required the definition of the thickness of the arterial wall, which was chosen to be 2 mm for the aorta and the RVOT conduit, and 1 mm for the CA branches,3 see Fig. 1A-D. Finally, the model was meshed using Cubit. The PA model was divided in three parts: a 30 mm long central section that defined the contact surfaces, internally with the balloon and externally with the aorta and CAs; and the two remaining parts, each 15 mm long, extending before and after the contact area. Tetrahedral elements where used for meshing the models, and in average, the number of elements used was 14,406 +/- 5875. The model thus obtained was then exported in ABAQUS (Dassault Systemes, RI) for the finite element simulations. Balloon Models In this study, two separate approaches were used to model the angioplasty balloon. In one case an analytical rigid surface is used to simulate the balloon, and the results of this approach are compared with a deformable balloon model. * Rigid Balloon In order to replicate folding of the angioplasty balloon into a catheter, the rigid balloon model was composed by 5 analytical rigid surfaces made in such a way that, after the applied radial displacement, the shells were forming a cylinder with a diameter matching that of an inflated angioplasty balloon, see Fig. 1E. * Deformable Balloon The deformable balloon model was created in ABAQUS. In this case, the balloon was modeled as a deformable 3D cylinder of 20 mm length, 1 mm of external diameter and 0.2 mm thickness.1 A mesh of 63 quadrilateral elements was generated and solved by employing reduced integration algorithms and large-strain formulation, see Fig. 1F. Material Models Human arterial tissue was modeled as a linear-elastic isotropic material with Young's modulus of 2.7 MPa and Poisson ratio of 0.49.4Duetothe lack of data on thematerialproperties of the conduit after implantation, the material properties of the conduit were assumed to be similar to those of the arterial tissue. Based on literature, the balloon was modeled as an isotropic, linear-elastic material, with a Young's modulus of 900 MPa and Poisson's ratio of 0.3.5-6 Contact Definition Each model surface was defined and surface-to-surface frictionless hard contact was imposed between the external surface of the balloon model and the internal surface of the conduit. Surface to surface frictionless hard contact was also imposed between the external pulmonary artery surface external surface of the aorta and the CA. The contact model used assumed that: (1) the surfaces transmit no contact pressure unless the nodes of the slave-surface contact the master-surface; (2) no penetration is allowed at each surface; (3) there is no limit to the magnitude of contact pressure that can be transmitted when the surfaces are in contact. The direct method was chosen as contact constraint enforcement method. Surface to surface contact was used such that the master role was given to the surface with the coarser mesh and/or larger area. For the analyses with analytical rigid surfaces, the master role was always given to the rigid shell. Boundary Conditions All the extremities of the conduit and of the aorta are constrained through an encastre. The extremity at the end of the CA is constrained as well through an encastre. Displacement Protocol The angioplasty intervention was simulated by displacing the balloon to the diameter used during the intervention. Although the TPVR standard protocol, states that the angioplasty balloon can be inflated to 110% of the original conduit diameter or 24 mm,1,2 whichever is greater, this protocol could be applied only to patient 2, see Fig. 1G. RESULTS For all the simulations, the balloon expanded under the imposed displacement conditions causing the conduit to deform. As the balloon displacement was increased, the central part of the conduit also expanded. It was also noticeable that once the balloon had reached its nominal diameter, the maximum stress value was localized in the portion of the conduit with the highest curvature for all four models. Rigid Balloon vs Deformable Balloon By comparing the two different approaches to model angioplasty, it was found that more stable results were obtained using the meshed cylinder balloon model rather than the one made of analytically rigid surfaces. However, it was possible to compare the results of the two models for deformations up to the 80% of the complete final angioplasty balloon diameter. Results on the conduit in terms of stress and deformation were strongly comparable. In fact, the average Von Mises stress varied by 0.76%, while the average displacement varied by 0.3%. In both cases the values obtained in the deformable model were smaller than the ones obtained in the rigid one. Angioplasty Outcomes For all the patient-specific models we evaluated whether CA compression could be modeled with this approach. The results show that in two cases the CA deforms, but there is no contact with the conduit. In these cases, we defined the CA to be distorted and not compressed as it deforms as a consequence of compression at the level of the aortic root, see Fig. 2A-D. DISCUSSION Segmentation of the patient geometries generated regular models, which made possible to complete the computational analysis. Overall, 50% of the sample population analyzed showed the risk of coronary deformation as a result of the angioplasty balloon expansion. Computational methods, such as the finite element method, represent an interesting alternative to the state-of-art catheterization lab evaluation, which have been found to have a low prediction value. The results of the four expansion simulations presented similar values of the maximum Von Mises stresses on the pulmonary arteries, while they present different results in terms of displacement and stresses in the coronary arteries, showing that coronary compression is strictly dependent on the specific geometry on the specific patient. CONCLUSIONS In this study, the effect of the balloon expansion during pre- TPV Angioplasty procedure was investigated by means of the FE method. Data of four patients who underwent attempted MelodyTM valve implantation were used. A deformable cylindrical balloon model was developed and compared with a balloon model constituted by analytical rigid shells to evaluate whether the choice of a different balloon model can be significant in terms of displacement results in the artery. The developed models allowed analysis of important parameters that could play a role in the determination on the angioplasty procedure outcome in terms of coronary compression. Finally, this work successfully identified a method to simulate a pre-TPVR procedure. Future work includes the analysis of a pressure based balloon expansion. This approach would be closer to the actual procedure and make possible the realization of a folded balloon model obtained by applying a negative pressure from a cylindrical configuration.(Table Presented)

Isolated anomalies of the branch pulmonary arteries are rare, more often occurring in the setting of complex congenital heart disease. These isolated anomalies are often not identified in the prenatal period. We describe two cases of isolated anomalies of the left pulmonary artery which were identified on fetal echocardiography and confirmed postnatally, an anomalous left pulmonary artery arising from the base of the left-sided brachiocephalic artery in the setting of a right-sided aortic arch, and a left pulmonary artery sling. These two cases support our current understanding of normal and abnormal development of the extrapericardial arterial vessels and highlight the importance of meticulous attention when sweeping from the three-vessel tracheal view.

Fluid overload (FO) is a common complication for pediatric patients in the intensive care unit. When conventional therapy fails, hemodialysis or peritoneal dialysis is classically used for fluid removal. Unfortunately, these therapies are often associated with cardiovascular or respiratory instability. Ultrafiltration, using devices such as the Aquadex system (Baxter Healthcare, Deerfield, IL, USA), is an effective tool for fluid removal in adult patients with congestive heart failure. As compared to hemodialysis, ultrafiltration can be performed using smaller catheters, and the extracorporeal volume and minimal blood flow rates are lower. In addition, there is no associated abdominal distension as is seen in peritoneal dialysis. Consequently, ultrafiltration may be better tolerated in critically ill pediatric patients. We present three cases of challenging pediatric patients with FO in the setting of congenital heart disease in whom ultrafiltration using the Aquadex system was successfully utilized for fluid removal while cardiorespiratory stability was maintained.

BACKGROUND: Bacterial infection (BI) after congenital heart surgery (CHS) is associated with increased morbidity and is difficult to differentiate from systemic inflammatory response syndrome caused by cardiopulmonary bypass (CPB). Procalcitonin (PCT) has emerged as a reliable biomarker of BI in various populations. AIM: To determine the optimal PCT threshold to identify BI among children suspected of having infection following CPB. SETTING AND DESIGN: Single-center retrospective observational study. MATERIALS AND METHODS: Medical records of all the patients admitted between January 2013 and April 2015 were reviewed. Patients in the age range of 0-21 years of age who underwent CHS requiring CPB in whom PCT was drawn between postoperative days 0-8 due to suspicion of infection were included. STATISTICAL ANALYSIS: The Wilcoxon rank-sum test was used for nonparametric variables. The diagnostic performance of PCT was evaluated using a receiver operating characteristic (ROC) curve. RESULTS: Ninety-eight patients were included. The median age was 2 months (25th and 75th interquartile of 0.1-7.5 months). Eleven patients were included in the BI group. The median PCT for the BI group (3.42 ng/mL, 25th and 75th interquartile of 2.34-5.67) was significantly higher than the median PCT for the noninfected group (0.8 ng/mL, 25th and 75th interquartile 0.38-3.39), P = 0.028. The PCT level that yielded the best compromise between the sensitivity (81.8%) and specificity (66.7%) was 2 ng/mL with an area under the ROC curve of 0.742. CONCLUSION: A PCT less than 2 ng/mL makes BI unlikely in children suspected of infection after CHS.

Background: Three-dimensional (3D) virtual models are valuable tools that may help to better understand complex cardiovascular anatomy and facilitate surgical planning in patients with congenital heart disease (CHD). Although computed tomography (CT) images are used most commonly to create these models [1,2], Magnetic Resonance Imaging (MRI) may be an attractive alternative, since it offers superior soft-tissue characterization and flexible image contrast mechanisms, and avoids the use of ionizing radiation. However, segmentation on MRI images is inherently challenging due to noise/artifacts, magnetic field inhomogeneity, and relatively lower spatial resolution compared to CT. The purpose of this study was to evaluate the image quality and assess the feasibility of creating virtual 3D heart models using a novel prototype 3D whole heart self-navigated radial MRI technique. Methods: Free-breathing self-navigated whole heart MRI was performed on three pediatric patients: two with complex CHD (average age=17 months) and one with normal cardiac anatomy (age=17years), using a 3D radial, non-slice-selective, T2-prepared, fat-saturated bSSFP sequence on a 1.5T MRI scanner (MAGNETOM Aera, Siemens, Germany). The acquisition window (~50-55 ms) was placed in mid-diastole and was adapted for different heart rates. Imaging parameters were as follows: TR/TE=3.1/1.56 ms, FOV=200 mm3, voxel size=1 mm3, FA=115degree, and acquisition time=5-6 minutes (~12000 radial lines). Respiratory motion correction and image reconstruction was performed on the scanner as described in [3]. For comparison, conventional non-gated 3D FLASH or navigator-gated 3D bSSFP sequences were also performed. All results were blinded and randomized for image quality assessment by one pediatric cardiologist and one cardiac radiologist using a five-point scale (1=non-diagnostic, 2=poor, 3=adequate, 4=good, 5=excellent). Statistical analysis was performed to compare mean scores. DICOM images were imported to a 3D workstation (Mimics, Materialise, Leuven, Belgium) for 3D postprocessing. The cardiovascular anatomy was first segmented using a combination of automated and manual techniques; and volume rendering was performed to depict the anatomy of interest. Results: The free-breathing self-navigated 3D radial acquisition provided significantly improved image quality and myocardial wall-blood contrast (Figure 1). Mean scores were 4.58 and 2.67 for the 3D radial and FLASH/ bSSFP sequences respectively (p = 0.003). The cardiovascular anatomy was well depicted on all virtual 3D models (Figure 2). Conclusions: 3D virtual models are frequently being created to understand complex anatomy, influence surgical planning, and provide intra-operative guidance for patients with CHD. This novel free-breathing, self-navigated whole heart 3D radial sequence provided excellent image quality as compared to existing routine MR sequences. Furthermore, the (Figure Presented) superb image quality provided using this novel sequence makes it an excellent choice for the creation of 3D models

Background: Complex ventricular-arterial (VA) relationships in patients with double outlet right ventricle (DORV) make preoperative assessment of potential repair pathways challenging. The relationship of the ventricular septal defect (VSD) to one or both great arteries must be understood and this influences the choice of surgical procedure [1] In neonates and infants with DORV, Computed Tomography (CT) is often performed due to the ability to get high spatial resolution and ECG gated images [2], however it is possible to get the necessary information from Magnetic Resonance (MR) imaging with an added advantage of avoiding exposure to ionizing radiation. Both CT and MR allow image acquisition in three dimensions (3D) but traditional viewing of the anatomy using the multiplanar reformatting is actually done in two dimensions (2D). Volume rendering from either modality may also be performed, but typically only the external vascular anatomy is depicted. We hypothesized that it is possible to accurately define the intracardiac anatomy in infants with DORV using virtual and physical 3D printed (rapid prototyped) models created from either MR or CT and this can both aid in better defining potential VA pathways and may assist in surgical decision making. Methods: Virtual and physical 3D models were generated for three patients with DORV. Non-ECG-gated 3D spoiled fast gradient echo sequence MR angiography was used for two patients. Retrospective ECG gated CT angiography images acquired in diastole were used in the third patient (to better define the coronary arteries given the suspicion of a single coronary artery by echocardiography). Blood pool segmentation (Figure 1a) was performed in all the three patients (Mimics, Materialise, Leuven, Belgium). A 2 mm shell was added to the blood pool and it was hollowed to create a patient specific heart replica (3-matic, Materialise, Leuven, Belgium). All virtual models were cut to best demonstrate the VA relationships and the models were printed. Results: The VSD and VA relationships were well visualized in all three patients using both the virtual and physical models (Figure 1b,c). The models helped the surgeons better understand the anatomy in all patients: in two patients the surgical plan was altered while the plan was confirmed in the third patient (Table 1). Conclusions: Construction of 3D models in patients with DORV is feasible and allows for extensive examination and surgical planning. This may facilitate a focused and informed surgical procedure and improve the potential for successful outcome. For purposes of DORV, non-gated MRA is sufficient to delineate the VA relationships adequately for 3D printing and enhanced clinical decision-making. CT imaging should be reserved for only those patients where additional information like coronary artery anatomy is desired