Design and implementation of multicenter pediatric and congenital studies with cardiovascular magnetic resonance: Big data in smaller bodies

Cardiovascular magnetic resonance (CMR) has become the reference standard for quantitative and qualitative assessment of ventricular function, blood flow, and myocardial tissue characterization. There is a preponderance of large CMR studies and registries in adults; However, similarly powered studies are lacking for the pediatric and congenital heart disease (PCHD) population. To date, most CMR studies in children are limited to small single or multicenter studies, thereby limiting the conclusions that can be drawn. Within the PCHD CMR community, a collaborative effort has been successfully employed to recognize knowledge gaps with the aim to embolden the development and initiation of high-quality, large-scale multicenter research. In this publication, we highlight the underlying challenges and provide a practical guide toward the development of larger, multicenter initiatives focusing on PCHD populations, which can serve as a model for future multicenter efforts.

Surgical Modulation of Pulmonary Artery Shear Stress: A Patient-Specific CFD Analysis of the Norwood Procedure

PURPOSR

This study created 3D CFD models of the Norwood procedure for hypoplastic left heart syndrome (HLHS) using standard angiography and echocardiogram data to investigate the impact of shunt characteristics on pulmonary artery (PA) hemodynamics. Leveraging routine clinical data offers advantages such as availability and cost-effectiveness without subjecting patients to additional invasive procedures.

METHODS

Patient-specific geometries of the intrathoracic arteries of two Norwood patients were generated from biplane cineangiograms. "Virtual surgery" was then performed to simulate the hemodynamics of alternative PA shunt configurations, including shunt type (modified Blalock-Thomas-Taussig shunt (mBTTS) vs. right ventricle-to-pulmonary artery shunt (RVPAS)), shunt diameter, and pulmonary artery anastomosis angle. Left-right pulmonary flow differential, Qp/Qs, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) were evaluated.

RESULTS

There was strong agreement between clinically measured data and CFD model output throughout the patient-specific models. Geometries with a RVPAS tended toward more balanced left-right pulmonary flow, lower Qp/Qs, and greater TAWSS and OSI than models with a mBTTS. For both shunt types, larger shunts resulted in a higher Qp/Qs and higher TAWSS, with minimal effect on OSI. Low TAWSS areas correlated with regions of low flow and changing the PA-shunt anastomosis angle to face toward low TAWSS regions increased TAWSS.

CONCLUSION

Excellent correlation between clinically measured and CFD model data shows that 3D CFD models of HLHS Norwood can be developed using standard angiography and echocardiographic data. The CFD analysis also revealed consistent changes in PA TAWSS, flow differential, and OSI as a function of shunt characteristics.

A Deep Learning Pipeline for Assessing Ventricular Volumes from a Cardiac MRI Registry of Patients with Single Ventricle Physiology

Purpose To develop an end-to-end deep learning (DL) pipeline for automated ventricular segmentation of cardiac MRI data from a multicenter registry of patients with Fontan circulation (Fontan Outcomes Registry Using CMR Examinations [FORCE]). Materials and Methods This retrospective study used 250 cardiac MRI examinations (November 2007-December 2022) from 13 institutions for training, validation, and testing. The pipeline contained three DL models: a classifier to identify short-axis cine stacks and two U-Net 3+ models for image cropping and segmentation. The automated segmentations were evaluated on the test set (n = 50) by using the Dice score. Volumetric and functional metrics derived from DL and ground truth manual segmentations were compared using Bland-Altman and intraclass correlation analysis. The pipeline was further qualitatively evaluated on 475 unseen examinations. Results There were acceptable limits of agreement (LOA) and minimal biases between the ground truth and DL end-diastolic volume (EDV) (bias: -0.6 mL/m2, LOA: -20.6 to 19.5 mL/m2) and end-systolic volume (ESV) (bias: -1.1 mL/m2, LOA: -18.1 to 15.9 mL/m2), with high intraclass correlation coefficients (ICCs > 0.97) and Dice scores (EDV, 0.91 and ESV, 0.86). There was moderate agreement for ventricular mass (bias: -1.9 g/m2, LOA: -17.3 to 13.5 g/m2) and an ICC of 0.94. There was also acceptable agreement for stroke volume (bias: 0.6 mL/m2, LOA: -17.2 to 18.3 mL/m2) and ejection fraction (bias: 0.6%, LOA: -12.2% to 13.4%), with high ICCs (>0.81). The pipeline achieved satisfactory segmentation in 68% of the 475 unseen examinations, while 26% needed minor adjustments, 5% needed major adjustments, and in 0.4%, the cropping model failed. Conclusion The DL pipeline can provide fast standardized segmentation for patients with single ventricle physiology across multiple centers. This pipeline can be applied to all cardiac MRI examinations in the FORCE registry. Keywords: Cardiac, Adults and Pediatrics, MR Imaging, Congenital, Volume Analysis, Segmentation, Quantification Supplemental material is available for this article. © RSNA, 2023.

Statistical modeling of extracellular vesicle cargo to predict clinical trial outcomes for hypoplastic left heart syndrome

Cardiac-derived c-kit+ progenitor cells (CPCs) are under investigation in the CHILD phase I clinical trial (NCT03406884) for the treatment of hypoplastic left heart syndrome (HLHS). The therapeutic efficacy of CPCs can be attributed to the release of extracellular vesicles (EVs). To understand sources of cell therapy variability we took a machine learning approach: combining bulk CPC-derived EV (CPC-EV) RNA sequencing and cardiac-relevant in vitro experiments to build a predictive model. We isolated CPCs from cardiac biopsies of patients with congenital heart disease (n = 29) and the lead-in patients with HLHS in the CHILD trial (n = 5). We sequenced CPC-EVs, and measured EV inflammatory, fibrotic, angiogeneic, and migratory responses. Overall, CPC-EV RNAs involved in pro-reparative outcomes had a significant fit to cardiac development and signaling pathways. Using a model trained on previously collected CPC-EVs, we predicted in vitro outcomes for the CHILD clinical samples. Finally, CPC-EV angiogenic performance correlated to clinical improvements in right ventricle performance.

Cardiac Magnetic Resonance Imaging to Determine Single Ventricle Function in a Pediatric Population is Feasible in a Large Trial Setting: Experience from the Single Ventricle Reconstruction Trial Longitudinal Follow up

The Single Ventricle Reconstruction (SVR) Trial was a randomized prospective trial designed to determine survival advantage of the modified Blalock-Taussig-Thomas shunt (BTTS) vs the right ventricle to pulmonary artery conduit (RVPAS) for patients with hypoplastic left heart syndrome. The primary aim of the long-term follow-up (SVRIII) was to determine the impact of shunt type on RV function. In this work, we describe the use of CMR in a large cohort follow up from the SVR Trial as a focused study of single ventricle function. The SVRIII protocol included short axis steady-state free precession imaging to assess single ventricle systolic function and flow quantification. There were 313 eligible SVRIII participants and 237 enrolled, ages ranging from 10 to 12.5 years. 177/237 (75%) participants underwent CMR. The most common reasons for not undergoing CMR exam were requirement for anesthesia (n = 14) or ICD/pacemaker (n = 11). A total of 168/177 (94%) CMR studies were diagnostic for RVEF. Median exam time was 54 [IQR 40-74] minutes, cine function exam time 20 [IQR 14-27] minutes, and flow quantification time 18 [IQR 12-25] minutes. There were 69/177 (39%) studies noted to have intra-thoracic artifacts, most common being susceptibility artifact from intra-thoracic metal. Not all artifacts resulted in non-diagnostic exams. These data describe the use and limitations of CMR for the assessment of cardiac function in a prospective trial setting in a grade-school-aged pediatric population with congenital heart disease. Many of the limitations are expected to decrease with the continued advancement of CMR technology.

Cardiac Magnetic Resonance Findings of Coronavirus Disease 2019 (COVID-19) Vaccine-Associated Myopericarditis at Intermediate Follow-Up: A Comparison with Classic Myocarditis

OBJECTIVE

To report intermediate cardiac magnetic resonance (CMR) findings of coronavirus disease 2019 (COVID-19) vaccine-associated myopericarditis (C-VAM) and compare with classic myocarditis.

STUDY DESIGN

Retrospective cohort study including children diagnosed with C-VAM from May 2021 through December 2021 with early and intermediate CMR. Patients with classic myocarditis from January 2015 through December 2021 and intermediate CMR were included for comparison.

RESULTS

There were 8 patients with C-VAM and 20 with classic myocarditis. Among those with C-VAM, CMR performed at a median 3 days (IQR 3, 7) revealed 2 of 8 patients with left ventricular ejection fraction <55%, 7 of 7 patients receiving contrast with late gadolinium enhancement (LGE), and 5 of 8 patients with elevated native T1 values. Borderline T2 values suggestive of myocardial edema were present in 6 of 8 patients. Follow-up CMRs performed at a median 107 days (IQR 97, 177) showed normal ventricular systolic function, T1, and T2 values; 3 of 7 patients had LGE. At intermediate follow-up, patients with C-VAM had fewer myocardial segments with LGE than patients with classic myocarditis (4/119 vs 42/340, P = .004). Patients with C-VAM also had a lower frequency of LGE (42.9 vs 75.0%) and lower percentage of left ventricular ejection fraction <55% compared with classic myocarditis (0.0 vs 30.0%), although these differences were not statistically significant. Five patients with classic myocarditis did not receive an early CMR, leading to some selection bias in study design.

CONCLUSIONS

Patients with C-VAM had no evidence of active inflammation or ventricular dysfunction on intermediate CMR, although a minority had persistent LGE. Intermediate findings in C-VAM revealed less LGE burden compared with classic myocarditis.

Autologous Cardiac Stem Cell Injection in Patients with Hypoplastic Left Heart Syndrome (CHILD Study)

Mortality in infants with hypoplastic left heart syndrome (HLHS) is strongly correlated with right ventricle (RV) dysfunction. Cell therapy has demonstrated potential improvements of RV dysfunction in animal models related to HLHS, and neonatal human derived c-kit⁺ cardiac-derived progenitor cells (CPCs) show superior efficacy when compared to adult human cardiac-derived CPCs (aCPCs). Neonatal CPCs (nCPCs) have yet to be investigated in humans. The CHILD trial (Autologous Cardiac Stem Cell Injection in Patients with Hypoplastic Left Heart Syndrome) is a Phase I/II trial aimed at investigating intramyocardial administration of autologous nCPCs in HLHS infants by assessing the feasibility, safety, and potential efficacy of CPC therapy. Using an open-label, multicenter design, CHILD investigates nCPC safety and feasibility in the first enrollment group (Group A/Phase I). In the second enrollment group, CHILD uses a randomized, double-blinded, multicenter design (Group B/Phase II), to assess nCPC efficacy based on RV functional and structural characteristics. The study plans to enroll 32 patients across 4 institutions: Group A will enroll 10 patients, and Group B will enroll 22 patients. CHILD will provide important insights into the therapeutic potential of nCPCs in patients with HLHS.Clinical Trial Registration https://clinicaltrials.gov/ct2/home NCT03406884, First posted January 23, 2018.

Highlights of the Virtual Society for Cardiovascular Magnetic Resonance 2022 Scientific Conference: CMR: improving cardiovascular care around the world

The 25th Society for Cardiovascular Magnetic Resonance (SCMR) Annual Scientific Sessions saw 1524 registered participants from more than 50 countries attending the meeting virtually. Supporting the theme "CMR: Improving Cardiovascular Care Around the World", the meeting included 179 invited talks, 52 sessions including 3 plenary sessions, 2 keynote talks, and a total of 93 cases and 416 posters. The sessions were designed so as to showcase the multifaceted role of cardiovascular magnetic resonance (CMR) in identifying and prognosticating various myocardial pathologies. Additionally, various social networking sessions as well as fun activities were organized. The major areas of focus for the future are likely to be rapid efficient and high value CMR exams, automated and quantitative acquisition and post-processing using artificial intelligence and machine learning, multi-contrast imaging and advanced vascular imaging including 4D flow.

Cardiac Magnetic Resonance Findings after Multisystem Inflammatory Syndrome in Children

OBJECTIVE

To describe the cardiac magnetic resonance (MR) findings of children recovered from multisystem inflammatory syndrome in children (MIS-C) longer than 3 months after acute illness.

STUDY DESIGN

We performed a retrospective cohort study of children hospitalized with MIS-C at a single institution receiving cardiac MR imaging between July 2020 and May 2021. Patient demographics, echocardiogram data from diagnosis through follow-up, and cardiac MR data obtained at approximately 3 months after hospitalization were recorded.

RESULTS

In total, 51 children with a median age of 11.3 years were included; 80% of patients had left ventricular ejection fraction <55%, 65% of patients developed valvular regurgitation, and 20% of patients developed coronary artery dilation during acute illness. Cardiac MR was performed at a median time of 105 days after diagnosis; 8% of patients had left ventricular ejection fraction <55%; 1 patient had residual valvular regurgitation; and 2 patients had residual coronary artery dilation. Two of 51 patients were found to have late gadolinium enhancement, T1 mapping abnormalities, and abnormal or borderline extracellular volume calculations suggesting myocardial fibrosis. No patient had T2 mapping abnormalities corresponding with edema, and no patient met the modified Lake Louise criteria for acute myocarditis; 10 of 51 patients had isolated elevated T1 values.

CONCLUSIONS

At 3-5 months following diagnosis, cardiac MR reveals no evidence of acute myocarditis as described by the modified Lake Louise criteria in patients with MIS-C. Two patients were observed to have myocardial fibrosis without regional wall motion abnormalities, and 10 had isolated imaging changes (elevated T1 values) in the absence of macroscopic fibrosis.

Factors Influencing Temporal Trends in Pediatric Inpatient Imaging Utilization

BACKGROUND

Concern exists over exponential growth in cardiac imaging in adults, but there is paucity of such data for cardiac imaging trends in pediatric patients. The aims of this study were to determine temporal trends in the use of noninvasive cardiac imaging and compare these with trends in the use of noncardiac imaging and to identify factors influencing those trends using the Pediatric Health Information Service database.

METHODS

Pediatric inpatient encounter data from January 2004 to December 2017 at 35 pediatric hospitals were extracted from the Pediatric Health Information Service database. Temporal imaging utilization trends in cardiac and noncardiac ultrasound or echocardiography, magnetic resonance imaging (MRI), and computed tomography (CT) were assessed using linear mixed-effects models. Models were adjusted for case-mix index, complex chronic conditions, patient age, length of stay, payer source, and cardiac surgical volume.

RESULTS

A total of 5,869,335 encounters over 14 years were analyzed (median encounters per center per year, 11,411; median patient age, 4 years; median length of stay, 3 days). From 2004 to 2017, the rates of pediatric inpatient cardiac and noncardiac ultrasound and MRI increased, whereas the rate of noncardiac CT decreased. Cardiac CT use increased beginning in 2014 (+0.264 cardiac CT encounters per 1,000 encounters per year), surpassing the rate of rise of cardiac MRI. Case-mix index, cardiac surgical volume, and payer source affected the largest number of imaging trends.

CONCLUSIONS

Among pediatric inpatients, utilization of cardiac and noncardiac ultrasound and MRI has steadily increased. Noncardiac CT use declined and cardiac CT use increased after 2014. Factors influencing imaging trends include case-mix index, cardiac surgical volume, and payer source. This study lays a foundation for investigations of imaging-related resource utilization and outcomes among pediatric inpatients.

Impact of Initial Shunt Type on Echocardiographic Indices in Children After Single Right Ventricle Palliations

Background Heart size and function in children with single right ventricle (RV) anomalies may be influenced by shunt type at the Norwood procedure. We sought to identify shunt-related differences during early childhood after staged surgical palliations using echocardiography. Methods We compared echocardiographic indices of RV, neoaortic, and tricuspid valve size and function at 14 months, pre-Fontan, and 6 years in 241 subjects randomized to a Norwood procedure using either the modified Blalock-Taussig shunt or RV-to-pulmonary-artery shunt. Results At 6 years, the shunt groups did not differ significantly in any measure except for increased indexed neoaortic area in the modified Blalock-Taussig shunt. RV ejection fraction improved between pre-Fontan and 6 years in the RV-to-pulmonary artery shunt group but was stable in the modified Blalock-Taussig shunt group. For the entire cohort, RV diastolic and systolic size and functional indices were improved at 6 years compared with earlier measurements, and indexed tricuspid and neoaortic annular area decreased from 14 months to 6 years. The prevalence of ≥moderate tricuspid and neoaortic regurgitation was uncommon and did not vary by group or time period. Diminished RV ejection fraction at the 14-month study was predictive of late death/transplant; the hazard of late death/transplant when RV ejection fraction was <40% was tripled (hazard ratio, 3.18; 95% CI, 1.41-7.17). Conclusions By 6 years after staged palliation, shunt type has not impacted RV size and function, and RV and valvar size and function show beneficial remodeling. Poor RV systolic function at 14 months predicts worse late survival independent of the initial shunt type. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT00115934.

Y-graft modification to the Fontan procedure: Increasingly balanced flow over time

OBJECTIVE

The use of Y-grafts for Fontan completion is hypothesized to offer more balanced hepatic flow distribution (HFD) and decreased energy losses. The purpose of this study was to evaluate the hemodynamic performance of Y-grafts over time using serial cardiac magnetic resonance data and to compare their performance with extracardiac Fontan connections.

METHODS

Ten Fontan patients with commercially available Y-graft connections and serial postoperative cardiac magnetic resonance data were included in this study. Patient-specific computational fluid dynamics simulations were used to estimate HFD and energy losses. Y-graft performance was compared with 3 extracardiac conduit Fontan groups (n = 10 for each) whose follow-up times straddle the Y-graft time points.

RESULTS

Y-graft HFD became significantly more balanced over time (deviation from 50% decreased from 18% ± 14% to 8% ± 8%; P = .015). Total cavopulmonary connection resistance did not significantly change. Y-grafts at 3-year follow-up showed more balanced HFD than the extracardiac conduit groups at both the earlier and later follow-up times. Total cavopulmonary connection resistance was not significantly different between any Y-graft or extracardiac conduit group.

CONCLUSIONS

Y-grafts showed significantly more balanced HFD over a 3-year follow-up without an increase in total cavopulmonary connection resistance, and therefore may be a valuable option for Fontan completion. Additional follow-up data at longer follow-up times are still needed to thoroughly characterize the potential advantages of Y-graft use.

The first cohort of prospective Fontan surgical planning patients with follow-up data: How accurate is surgical planning?

OBJECTIVE

Fontan surgical planning is an image-based, collaborative effort, which is hypothesized to result in improved patient outcomes. A common motivation for Fontan surgical planning is the progression (or concern for progression) of pulmonary arteriovenous malformations. The purpose of this study was to evaluate the accuracy of surgical planning predictions, specifically hepatic flow distribution (HFD), a known factor in pulmonary arteriovenous malformation progression, and identify methodological improvements needed to increase prediction accuracy.

METHODS

Twelve single-ventricle patients who were enrolled in a surgical planning protocol for Fontan surgery with pre- and postoperative cardiac imaging were included in this study. Computational fluid dynamics were used to compare HFD in the surgical planning prediction and actual postoperative conditions.

RESULTS

Overall, HFD prediction error was 17 ± 13%. This error was similar between surgery types (15 ± 18% and 18 ± 10% for revisions vs Fontan completions respectively; P = .73), but was significantly lower (6 ± 7%; P = .05) for hepatic to azygous shunts. Y-grafts and extracardiac conduits showed a strong correlation between prediction error and discrepancies in graft insertion points (r = 0.99; P < .001). Improving postoperative anatomy prediction significantly reduced overall HFD prediction error to 9 ± 6% (P = .03).

CONCLUSIONS

Although Fontan surgical planning can offer accurate HFD predictions for specific graft types, methodological improvements are needed to increase overall accuracy. Specifically, improving postoperative anatomy prediction was shown to be an important target for future work. Future efforts and refinements to the surgical planning process will benefit from an improved understanding of the current state and will rely heavily on increased follow-up data.

The utility of cardiac magnetic resonance imaging in post-Fontan surveillance

OBJECTIVE

Gated cardiac MRI offers the most detailed and accurate noninvasive method of assessing cardiac anatomy, particularly in patients with complex congenital heart disease. The proposed benefits of using cMRI as a routine screening tool in the Fontan population include early recognition of asymptomatic, postoperative anatomic and physiologic changes. In 2011, we therefore instituted at our center a recommended practice of cMRI screening in patients with Fontan physiology at 3 and 8 years post-Fontan operation. The purpose of this study was to determine the impact of this standardized practice of cMRI screening on the clinical management of a Fontan population.

DESIGN

We retrospectively reviewed charts from our institutional Fontan database to determine which patients were eligible for cMRI under the current guidelines and who underwent imaging from November 2002 to June 2015. We reviewed the frequency of cMRI and number of changes in management based on the results. Statistical significance was determined using a chi-square test.

RESULTS

There were 141 cMRIs performed on 121 patients who met inclusion criteria. The odds of a change in management were significantly greater after clinically indicated cMRI compared to screening cMRI (OR = 3.79, 95% CI: 1.48-9.66, P = .004). There were near significant odds of change in management if the cMRI occurred <8 years after Fontan regardless of whether it was for screening or clinically indicated purposes (OR = 2.43, 95% CI: 0.97-6.08, P = .052). The most frequent change in management was referral for catheterization with pulmonary artery angioplasty.

CONCLUSIONS

There is an important role for cMRI in routine surveillance of post-Fontan patients. Screening cMRI performed less than 8 years after Fontan palliation offers increased utility compared to studies performed later. The optimal timing of such imaging after Fontan palliation remains unclear.

The Impact of the Left Ventricle on Right Ventricular Function and Clinical Outcomes in Infants with Single-Right Ventricle Anomalies up to 14 Months of Age

BACKGROUND

Children with single-right ventricle anomalies such as hypoplastic left heart syndrome (HLHS) have left ventricles of variable size and function. The impact of the left ventricle on the performance of the right ventricle and on survival remains unclear. The aim of this study was to identify whether left ventricular (LV) size and function influence right ventricular (RV) function and clinical outcome after staged palliation for single-right ventricle anomalies.

METHODS

In the Single Ventricle Reconstruction trial, echocardiography-derived measures of LV size and function were compared with measures of RV systolic and diastolic function, tricuspid regurgitation, and outcomes (death and/or heart transplantation) at baseline (preoperatively), early after Norwood palliation, before stage 2 palliation, and at 14 months of age.

RESULTS

Of the 522 subjects who met the study inclusion criteria, 381 (73%) had measurable left ventricles. The HLHS subtype of aortic atresia/mitral atresia was significantly less likely to have a measurable left ventricle (41%) compared with the other HLHS subtypes: aortic stenosis/mitral stenosis (100%), aortic atresia/mitral stenosis (96%), and those without HLHS (83%). RV end-diastolic and end-systolic volumes were significantly larger, while diastolic indices suggested better diastolic properties in those subjects with no left ventricles compared with those with measurable left ventricles. However, RV ejection fraction was not different on the basis of LV size and function after staged palliation. Moreover, there was no difference in transplantation-free survival to Norwood discharge, through the interstage period, or at 14 months of age between those subjects who had measurable left ventricles compared with those who did not.

CONCLUSIONS

LV size varies by anatomic subtype in infants with single-right ventricle anomalies. Although indices of RV size and diastolic function were influenced by the presence of a left ventricle, there was no difference in RV systolic function or transplantation-free survival on the basis of LV measures.

Fontan Surgical Planning: Previous Accomplishments, Current Challenges, and Future Directions

The ultimate goal of Fontan surgical planning is to provide additional insights into the clinical decision-making process. In its current state, surgical planning offers an accurate hemodynamic assessment of the pre-operative condition, provides anatomical constraints for potential surgical options, and produces decent post-operative predictions if boundary conditions are similar enough between the pre-operative and post-operative states. Moving forward, validation with post-operative data is a necessary step in order to assess the accuracy of surgical planning and determine which methodological improvements are needed. Future efforts to automate the surgical planning process will reduce the individual expertise needed and encourage use in the clinic by clinicians. As post-operative physiologic predictions improve, Fontan surgical planning will become an more effective tool to accurately model patient-specific hemodynamics.

Radiation dose management for pediatric cardiac computed tomography: a report from the Image Gently 'Have-A-Heart' campaign

Children with congenital or acquired heart disease can be exposed to relatively high lifetime cumulative doses of ionizing radiation from necessary medical imaging procedures including radiography, fluoroscopic procedures including diagnostic and interventional cardiac catheterizations, electrophysiology examinations, cardiac computed tomography (CT) studies, and nuclear cardiology examinations. Despite the clinical necessity of these imaging studies, the related ionizing radiation exposure could pose an increased lifetime attributable cancer risk. The Image Gently "Have-A-Heart" campaign is promoting the appropriate use of medical imaging studies in children with congenital or acquired heart disease while minimizing radiation exposure. The focus of this manuscript is to provide a comprehensive review of radiation dose management and CT performance in children with congenital or acquired heart disease.

Radiation Safety in Children With Congenital and Acquired Heart Disease: A Scientific Position Statement on Multimodality Dose Optimization From the Image Gently Alliance

There is a need for consensus recommendations for ionizing radiation dose optimization during multimodality medical imaging in children with congenital and acquired heart disease (CAHD). These children often have complex diseases and may be exposed to a relatively high cumulative burden of ionizing radiation from medical imaging procedures, including cardiac computed tomography, nuclear cardiology studies, and fluoroscopically guided diagnostic and interventional catheterization and electrophysiology procedures. Although these imaging procedures are all essential to the care of children with CAHD and have contributed to meaningfully improved outcomes in these patients, exposure to ionizing radiation is associated with potential risks, including an increased lifetime attributable risk of cancer. The goal of these recommendations is to encourage informed imaging to achieve appropriate study quality at the lowest achievable dose. Other strategies to improve care include a patient-centered approach to imaging, emphasizing education and informed decision making and programmatic approaches to ensure appropriate dose monitoring. Looking ahead, there is a need for standardization of dose metrics across imaging modalities, so as to encourage comparative effectiveness studies across the spectrum of CAHD in children.

Role of Computational Modelling in Planning and Executing Interventional Procedures for Congenital Heart Disease

Increasingly, computational modelling and numerical simulations are used to help plan complex surgical and interventional cardiovascular procedures in children and young adults with congenital heart disease. From its origins more than 30 years ago, surgical planning with analysis of flow hemodynamics and energy loss/efficiency has helped design and implement many modifications to existing techniques. On the basis of patient-specific medical imaging, surgical planning allows accurate model production that can then be manipulated in a virtual surgical environment, with the proposed solutions finally tested with advanced computational fluid dynamics to evaluate the results. Applications include a broad range of congenital heart disease, including patients with single-ventricle anatomy undergoing staged palliation, those with arch obstruction, with double outlet right ventricle, or with tetralogy of Fallot. In the present work, we focus on clinical applications of this exciting field. We describe the framework for these techniques, including brief descriptions of the engineering principles applied and the interaction between "benchtop" data with medical decision-making. We highlight some early insights learned from pioneers over the past few decades, including refinements in Fontan baffle geometries and configurations. Finally, we offer a glimpse into exciting advances that are presently being explored, including use of modelling for transcatheter interventions. In this era of personalized medicine, computational modelling and surgical planning allows patient-specific tailoring of interventions to optimize clinical outcomes.

Improved high-resolution pediatric vascular cardiovascular magnetic resonance with gadofosveset-enhanced 3D respiratory navigated, inversion recovery prepared gradient echo readout imaging compared to 3D balanced steady-state free precession readout imaging

BACKGROUND

Improved delineation of vascular structures is a common indication for cardiovascular magnetic resonance (CMR) in children and requires high spatial resolution. Currently, pre-contrast 3D, respiratory navigated, T2-prepared, fat saturated imaging with a bSSFP readout (3D bSSFP) is commonly used; however, these images can be limited by blood pool inhomogeneity and exaggeration of metal artifact. We compared image quality of pediatric vasculature obtained using standard 3D bSSFP to 3D, respiratory navigated, inversion recovery prepared imaging with a gradient echo readout (3D IR GRE) performed after administration of gadofosveset trisodium (GT), a blood pool contrast agent.

METHODS

For both sequences, VCG triggering was used with acquisition during a quiescent period of the cardiac cycle. 3D bSSFP imaging was performed pre-contrast, and 3D IR GRE imaging was performed 5 min after GT administration. We devised a vascular imaging quality score (VIQS) with subscores for coronary arteries, pulmonary arteries and veins, blood pool homogeneity, and metal artifact. Scoring was performed on axial reconstructions of isotropic datasets by two independent readers and differences were adjudicated. Signal- and contrast-to-noise (SNR and CNR) calculations were performed on each dataset.

RESULTS

Thirty-five patients had both 3D bSSFP and 3D IR GRE imaging performed. 3D IR GRE imaging showed improved overall vascular imaging compared to 3D bSSFP when comparing all-patient VIQS scores (n = 35, median 14 (IQR 11-15), vs 6 (4-10), p < 0.0001), and when analyzing the subset of patients with intrathoracic metal (n = 17, 16 (14-17) vs. 5 (2-9), p < 0.0001). 3D IR GRE showed significantly improved VIQS subscores for imaging the RCA, pulmonary arteries, pulmonary veins, and blood pool homogeneity. In addition, 3D IR GRE imaging showed reduced variability in both all-patient and metal VIQS scores compared to 3D bSSFP (p < 0.05). SNR and CNR were higher with 3D IR GRE in the left ventricle and left atrium, but not the pulmonary arteries.

CONCLUSIONS

Respiratory navigated 3D IR GRE imaging after GT administration provides improved vascular CMR in pediatric patients compared to pre-contrast 3D bSSFP imaging, as well as improved imaging in patients with intrathoracic metal. It is an excellent alternative in this challenging patient population when high spatial resolution vascular imaging is needed.

Safety of Magnetic Resonance Imaging After Implantation of Stainless Steel Embolization Coils

Stainless steel embolization coils (SSEC) have been used for over four decades for vascular occlusion. Recently, the safety of these coils in a magnetic resonance environment has been called into question, with important ramifications for thousands of patients with existing coils in place. We performed a retrospective chart review at five tertiary care pediatric centers evaluating all children and young adults with implanted SSEC who underwent magnetic resonance imaging (MRI). Data reviewed included demographics, coil implantation, MRI studies, and follow-up evaluations. Complications such as heating, discomfort, or device migration were specifically sought. Two hundred and ninety-seven patients with implanted SSEC underwent 539 MRI examinations. The median age at SSEC implantation was 2.3 years (1 week-23.2 years). The MRI studies were performed a median of 7.4 years (4 days-23.1 years) after implantation. No patients experienced any reported complications associated with their MRI examinations during the study or at median follow-up post-MRI of 4.8 years (1 day-23 years). In this large, retrospective review of patients with implanted SSEC undergoing MRI, there were no reported adverse events. These findings support the recent change by Cook Medical Inc. of their standard embolization coils from a designation of magnetic resonance unsafe to conditional.

Hemodynamic Impact of Superior Vena Cava Placement in the Y-Graft Fontan Connection

BACKGROUND

A Fontan Y-shaped graft using a commercially available aortoiliac graft has been used to connect the inferior vena cava (IVC) to the pulmonary arteries. This modification of the Fontan procedure seeks to improve hepatic flow distribution (HFD) to the lungs. However, patient-specific anatomical restrictions might limit the space available for graft placement. Altering the superior vena cava (SVC) positioning is hypothesized to provide more space for an optimal connection, avoiding caval flow collision. Computational modeling tools were used to retrospectively study the effect of SVC placement on Y-graft hemodynamics.

METHODS

Patient-specific anatomies (N = 10 patients) and vessel flows were reconstructed from retrospective cardiac magnetic resonance (CMR) images after Fontan Y-graft completion. Alternative geometries were created using a virtual surgery environment, altering the SVC position and the offset in relation to the Y-graft branches. Geometric characterization and computational fluid dynamics simulations were performed. Hemodynamic factors (power loss and HFD) were computed.

RESULTS

Patients with a higher IVC return showed less sensitivity to SVC positioning. Patients with low IVC flow showed varied HFD results, depending on SVC location. Balanced HFD values (50% to each lung) were obtained when the SVC lay completely between the Y-graft branches. The effect on power loss was patient specific.

CONCLUSIONS

SVC positioning with respect to the Y-graft affects HFD, especially in patients with lower IVC flow. Careful positioning of the SVC at the time of a bidirectional Glenn (BDG) procedure based on patient-specific anatomy can optimize the hemodynamics of the eventual Fontan completion.

Lower extremity edema in a child due to pectus excavatum

A previously healthy 11-year-old girl was referred for pediatric cardiology evaluation because of the development of progressive bilateral lower extremity swelling over the course of 2 years. Her prior workup had included a negative result for proteinuria and a negative ultrasound for deep venous thrombosis. On physical examination, in addition to her edema, she was found to have a severe pectus excavatum deformity, which prompted cardiac magnetic resonance imaging. This study demonstrated compression of the inferior vena cava. She underwent uneventful pectus repair with use of a modified Ravitch procedure and experienced complete resolution of her lower extremity edema.

Impact of initial norwood shunt type on right ventricular deformation: the single ventricle reconstruction trial

BACKGROUND

The Single Ventricle Reconstruction trial demonstrated a transplantation-free survival advantage at 12-month follow-up for patients with right ventricle-pulmonary artery shunts (RVPAS) with the Norwood procedure compared with modified Blalock-Taussig shunts but similar survival and decreased global right ventricular (RV) function on longer term follow-up. The impact of the required ventriculotomy for the RVPAS remains unknown. The aim of this study was to compare echocardiography-derived RV deformation indices after stage 2 procedures in survivors with single RV anomalies enrolled in the Single Ventricle Reconstruction trial.

METHODS

Global and regional RV systolic longitudinal and circumferential strain and strain rate, ejection fraction, and short-axis percentage fractional area change were all derived by speckle-tracking echocardiography from protocol echocardiograms obtained at 14.3 ± 1.2 months. Student t tests or Wilcoxon rank sum tests were used to compare groups.

RESULTS

The cohort included 275 subjects (129 in the modified Blalock-Taussig shunt group and 146 in the RVPAS group). Longitudinal deformation could be quantified in 214 subjects (78%) and circumferential measures in 182 subjects (66%). RV ejection fraction and percentage fractional area change did not differ between groups. There were no significant differences between groups for global or regional longitudinal deformation. Circumferential indices showed abnormalities in deformation in the RVPAS group, with decreased global circumferential strain (P = .05), strain rate (P = .09), and anterior regional strain rate (P = .07) that approached statistical significance.

CONCLUSIONS

RV myocardial deformation at 14 months, after stage 2 procedures, was not significantly altered by the type of initial shunt placed. However, abnormal trends were appreciated in circumferential deformation for the RVPAS group in the area of ventriculotomy that may represent early myocardial dysfunction. These data provide a basis for longer term RV deformation assessment in survivors after Norwood procedures.

Impact of obesity on ventricular size and function in children, adolescents and adults with Tetralogy of Fallot after initial repair

Obesity is epidemic in congenital heart disease, with reported rates of 16% to 26% in children and 54% in adults. The aim of this study was to evaluate the impact of obesity on ventricular function and size in patients after initial repair for tetralogy of Fallot (TOF). Cardiac magnetic resonance studies in normal-weight (body mass index percentile <85th) and obese (body mass index percentile ≥95th) children and adults with repaired tetralogy of Fallot were reviewed. The left ventricular ejection fraction, the right ventricular ejection fraction, left and right ventricular end-diastolic volumes indexed to actual body surface area, to height, and to body surface area using ideal body weight were evaluated in 36 obese patients and 72 age-matched normal-weight patients. Compared with normal-weight patients, obese patients had lower right ventricular ejection fractions (mean 46 ± 9% vs 51 ± 7%, p = 0.003) and left ventricular ejection fractions (mean 57 ± 9% vs 61 ± 6%, p = 0.017), higher right ventricular end-diastolic volumes indexed to height (mean 160 ± 59 vs 135 ± 41 ml/m, p = 0.015) and left ventricular end-diastolic volumes indexed to height (mean 86 ± 25 vs 70 ± 20 ml/m, p = 0.001), and higher right ventricular end-diastolic volumes indexed to ideal body weight (mean 166 ± 55 vs 144 ± 38 ml/m², p = 0.020) and left ventricular end-diastolic volumes indexed to ideal body weight (mean 90 ± 22 vs 75 ± 15 ml/m², p <0.001). In conclusion, obesity is a modifiable risk factor associated with worsened biventricular systolic function and biventricular dilation in patients with repaired tetralogy of Fallot. The standard method of indexing ventricular volumes using actual body surface area may underestimate volume load in obese patients.

Zic3 is required in the extra-cardiac perinodal region of the lateral plate mesoderm for left-right patterning and heart development

Mutations in ZIC3 cause human X-linked heterotaxy and isolated cardiovascular malformations. A mouse model with targeted deletion of Zic3 demonstrates an early role for Zic3 in gastrulation, CNS, cardiac and left-right axial development. The observation of multiple malformations in Zic3(null) mice and the relatively broad expression pattern of Zic3 suggest its important roles in multiple developmental processes. Here, we report that Zic3 is primarily required in epiblast derivatives to affect left-right patterning and its expression in epiblast is necessary for proper transcriptional control of embryonic cardiac development. However, cardiac malformations in Zic3 deficiency occur not because Zic3 is intrinsically required in the heart but rather because it functions early in the establishment of left-right body axis. In addition, we provide evidence supporting a role for Zic3 specifically in the perinodal region of the posterior lateral plate mesoderm for the establishment of laterality. These data delineate the spatial requirement of Zic3 during left-right patterning in the mammalian embryo, and provide basis for further understanding the molecular mechanisms underlying the complex interaction of Zic3 with signaling pathways involved in the early establishment of laterality.

Abstract 122: Global Longitudinal Peak Strain Detects Early Cardiac Damage in Hypertensive Children

Background: Childhood hypertension is increasingly common and likely contributes to the premature development of cardiovascular and renal disease. Early detection of hypertensive cardiac damage may allow for prompt therapy and reduce the risk of late morbidity and mortality. While left ventricular mass index (LVMI) has been used as a surrogate of hypertensive cardiac damage in children, its prognostic and diagnostic value is not completely understood in this population.

Objective: To test the hypothesis that strain assessment using automated function imaging (AFI) detects cardiac changes in hypertensive children earlier than standard 2D echocardiographic techniques.

METHODS: A cross-sectional study of hypertensive children < 19 years old between October 2010 and May 2012 was performed. Any patient who was newly diagnosed with hypertension and underwent echocardiographic examination including standard 2D, Doppler, and automated function imaging (AFI) modalities was included. Global peak longitudinal systolic strain (GLPSS) was measured using a 17 segment model of the left ventricle. All echocardiographic measures were compared to normative reference values for age.

Results: Twenty four patients (mean age 14.6 ± 2.7 years, 67% male) were identified. Mean systolic and diastolic blood pressure index was 1.1 ± 0.1 and 0.9 ± 0.1, respectively. Mean LVMI did not significantly differ from 95 th -percentile normative values (41.6 ± 11.2 g/m 2.7 vs. 39.3 ± 1.5 g/m 2.7 , p = 0.328). Mean GLPSS was significantly lower than 5 th -percentile normative values (-17.6 ± 2.5 vs. -19.5 ± 0.42, p = 0.001) and were decreased across all myocardial segments. Left atrial volume was significantly higher than reported normal values in children (27.6 ± 7.3 ml/m 2 vs. 22.0 ± 6.0 ml/m 2 , p = 0.002). No patient exhibited abnormal shortening or ejection fraction, mitral E-wave to A-wave ratio, or lateral mitral E-wave to e’-wave ratio.

Conclusions: A population of unselected, newly diagnosed hypertensive adolescents had atypically low GLPSS and increased left atrial volume. The use of GLPSS measured by AFI may be a more sensitive marker of early myocardial remodeling in hypertensive children and routine measurement of GLPSS should be considered.

Association between left ventricular mass index and cardiac function in pediatric dialysis patients

BACKGROUND

Left ventricular mass index (LVMI) is a surrogate of left ventricular hypertrophy and a predictor of cardiac morbidity and mortality in adults with hypertension. LVMI has not been linked to cardiovascular endpoints in children. The aim of this study was to identify an association between elevated LVMI and echocardiographic markers of systolic and diastolic function.

METHODS

The study was a retrospective review of chronic dialysis patients from June 1995 to December 2009 at a single tertiary care children's hospital. The upper limit cutoffs for LVMI were set at >38.6 g/m(2.7), >51 g/m(2.7), and by age and sex-based normative values. Sixty-three patients (mean age 14.1 years, 56% males) were enrolled in the study, with a total of 287 echocardiograms.

RESULTS

Post-dialysis hypertension was associated with elevated LVMI in both the >51 g/m(2.7) [odds ratio (OR) 2.9, 95% confidence interval (CI) 1.5-5.5] and normative (OR 3.4, 95% CI 1.5-7.7) models. Elevated LVMI, when defined by the >51 g/m(2.7) and normative models, was significantly associated with decreased shortening fraction (OR 4.1, 95% CI 1.7-9.8 and OR 5.4, 95% CI 1.3-22.9, respectively) and increased mitral E wave to lateral mitral tissue Doppler e' wave velocity ratio (E/e'; OR 3.5, 95% CI 1.1-11.2 and OR 4.5, 95% CI 1.0-21.6, respectively).

CONCLUSIONS

Elevated LVMI is associated with decreased systolic and diastolic cardiac function, justifying its use as a surrogate of hypertensive cardiomyopathy in children undergoing chronic dialysis.

The impact of a dedicated single-ventricle home-monitoring program on interstage somatic growth, interstage attrition, and 1-year survival

OBJECTIVE

There has been considerable improvement in survival after the first stage of palliation for single-ventricle heart disease. Yet, interstage mortality continues to plague this population. Home monitoring has been proposed to reduce interstage mortality. We review our experience after creation of a Single Ventricle Program.

METHODS

All infants with a single ventricle heart defect who were admitted to Texas Children's Hospital from the inception of the Single Ventricle Program on September 1, 2007, to January 1, 2010, were included in the Single Ventricle Program cohort. Infants with a single ventricle presenting between January 1, 2002, and August 31, 2007, comprised the pre-Single Ventricle Program group. Anatomic, operative, and postoperative details were noted for all patients. End points included in-hospital death after the first stage of palliation, interstage death (defined as after discharge from the first stage of palliation and before the second stage of palliation), and death or heart transplantation by 1 year of age. Interstage weight gain was also compared.

RESULTS

A total of 137 infants with a single ventricle were included in the pre-Single Ventricle Program cohort, and 93 infants were included in the Single Ventricle Program cohort. Anatomic subtypes were similar between groups. There was significant improvement in rate of interstage weight gain, whereas age at the second stage of palliation was significantly reduced in the Single Ventricle Program group. In-house mortality decreased during the Single Ventricle Program era (P = .021). Interstage mortality did not significantly decrease in the Single Ventricle Program group. However, 1-year transplant-free survival improved during the Single Ventricle Program era (P = .002).

CONCLUSIONS

The Single Ventricle Program improved interstage weight gain, thereby allowing for early second-stage palliation at an equivalent patient weight. Interstage mortality was not significantly reduced by our program. However, 1-year transplant-free survival was significantly improved in patients in the Single Ventricle Program.

ALCAPA: the role of myocardial viability studies in determining prognosis

BACKGROUND

ALCAPA is optimally treated by coronary artery reimplantation early in neonatal life. Delayed diagnosis, however, is not infrequent, because symptoms often do not manifest until about 3 months of age, coinciding with the physiological nadir in pulmonary vascular resistance. With delayed diagnosis, there is potential for coronary steal and irreversible myocardial injury, which worsens outcome.

OBJECTIVE

To assess the utility of MRI in determining prognosis in children with surgically corrected ALCAPA.

MATERIALS AND METHODS

A retrospective chart review was performed in two children with ALCAPA who underwent coronary reimplantation and postoperative cardiac MRI. Both children subsequently underwent cardiac transplantation. The imaging findings and pathological findings at explant are presented.

RESULTS

In both children, there was severe, globally depressed left ventricular systolic function and abnormal delayed enhancement in a predominantly subendocardial distribution. Pathological examination of the cardiac explants showed extensive fibrotic tissue, which correlated with areas of abnormal delayed enhancement on MRI.

CONCLUSION

Severe reduction in systolic function and presence of delayed enhancement indicate extensive myocardial injury and pathologically correlate with irreversible fibrotic changes, which may help identify a subgroup of children who will not recover ventricular function and ultimately require heart transplantation.

Anomalous left coronary artery from the pulmonary artery in a preterm infant: presentation after ligation of ductus arteriosus

Surgical or medical closure of a patent ductus arteriosus (PDA) is a very common practice in premature infants in the neonatal intensive care unit, but often the coronary arteries are not delineated prior to closure. In this report, a 32-week gestational age premature infant who underwent surgical ligation of a PDA developed new-onset left ventricular systolic dysfunction. A repeat echocardiogram noted an anomalous left coronary artery from the pulmonary artery. Successful left coronary artery reimplantation with rapid normalization of left ventricular systolic function occurred. As previously not reported, ligation of a PDA in a premature infant can unmask anomalous left coronary artery from the pulmonary artery. Surgical left coronary artery reimplantation is the mainstay of therapy and should be performed to establish normal coronary blood flow, even in a premature, low birth weight infant.

Isolated sinus node dysfunction in an infant with developmental delay

We present a case of an infant with developmental delay, a structurally normal heart, and prolonged sinus pauses that suffered an unmonitored cardiac arrest while in the hospital. An investigation into the etiology of her sinus pauses did not reveal a definitive cause, and she continued to have pauses up to 15 s in duration. Her history of the cardiac arrest and the duration of the pauses guided the physicians' recommendations and the family's decision to undergo pacemaker implantation prior to discharge from the hospital.

Transient complete atrioventricular block after placement of a central venous catheter in a neonate

OBJECTIVE

We present a case of trauma-induced complete atrioventricular block (transient) after placement of a central venous catheter.

DESIGN

Case report.

SETTING

Neonatal intensive care unit in a tertiary care children's hospital.

PATIENT

Review of the medical record and clinical course of a single premature infant.

INTERVENTIONS

Removal of central venous catheter, monitoring of the cardiac output exam, and serial monitoring of the arrhythmia profile.

MEASUREMENTS AND MAIN RESULTS

Trauma-induced complete atrioventricular block from placement of the central venous catheter resolved in 9 days, obviating the need for pacemaker placement.

CONCLUSIONS

Complete atrioventricular block is an infrequent complication of central venous catheter placement and may require several days to resolve.

Captopril-induced pulmonary infiltrates with eosinophilia in an infant with congenital heart disease

We report a case of an infant with complex congenital heart disease who was placed on captopril for afterload reduction following cardiac surgery and subsequently developed pulmonary infiltrates with eosinophilia. The patient was readmitted with symptoms of rhinorrhea, poor feeding, and decreased activity level. She was found to have diffuse pulmonary infiltrates on chest radiograph and a marked peripheral eosinophilia without leukocytosis. After discontinuing captopril and starting systemic steroids, her symptomatology rapidly improved, and her eosinophilia and radiographic abnormalities both resolved.

Characteristics and outcomes of fetuses with pericardial effusions

Little is known about the characteristics and outcomes of fetuses with pericardial effusions (PEs); therefore, this study sought to identify factors associated with fetal PEs and the natural histories and outcomes of fetuses with PEs. Large PEs are associated with a greater likelihood of structural heart disease, impaired cardiac function, and chromosomal abnormalities, and PEs with hydrops or extracardiac malformations are associated with death. Most fetal PEs resolve, and fetuses with isolated PEs have a very good prognosis.