Timothy C. Slesnick

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.

Current Outcomes of the Norwood Operation in Patients With Single-Ventricle Malformations Other Than Hypoplastic Left Heart Syndrome

Background: Subsequent to increased experience with the Norwood operation in children with hypoplastic left heart syndrome (HLHS), its application has expanded to allow palliation of single-ventricle (SV) malformations other than HLHS. We describe current palliation outcomes in this group of SV patients. Methods: Between 2002 and 2012, 65 of the 303 Norwood operations were performed in non-HLHS SV patients. Competing risk analysis modeled events after Norwood and after subsequent Glenn and examined risk factors affecting outcomes. Results: Competing risk analysis showed that one year following Norwood, 24% of patients had died or received transplantation, 72% had undergone Glenn, and 4% were alive awaiting Glenn/Kawashima. Five years following Glenn, 9% of patients had died, 68% had undergone Fontan, and 23% were alive awaiting Fontan. Overall seven-year survival following Norwood was 68%. On multivariable analysis, mortality risk factors were unplanned cardiac reoperation (hazard ratio [HR]: 4.0 [1.5-10.6], P = .006), right dominant ventricle morphology (HR: 3.3 [1.3-8.3], P = .012), and postoperative extracorporeal membrane oxygenation (HR: 3.1 [1.1-9.0], P = .035). Conclusions: Operative death and interstage mortality continue to be problematic following Norwood palliation for non-HLHS SV variants. Outcomes seem comparable to those reported for HLHS, however they are influenced by underlying pathology; children with dominant left ventricle morphology (tricuspid atresia and double inlet left ventricle) have superior survival compared to those with dominant right ventricle morphology (mitral atresia, unbalanced atrioventricular septal defect, and most patients with atrial isomerism). Unplanned reoperations for technical imperfections diminish survival. Large multicenter studies might be warranted to better identify high-risk patients and provide guidance toward improving their survival.

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.

Influence of Morphology and Initial Surgical Strategy on Survival of Infants With Tricuspid Atresia

BACKGROUND Tricuspid atresia (TA) is a heterogeneous single-ventricle anomaly in which initial presentation and, consequently, timing and mode of palliation vary based on morphology and degree of pulmonary or systemic outflow obstruction. We report current era palliation outcomes and examine whether morphologic and, subsequently, surgical factors influence survival. METHODS From 2002 to 2012, 105 infants with TA underwent surgical palliation. Competing risks analyses modeled events after first-stage surgery (Glenn versus death) and after Glenn (Fontan versus death) and examined risk factors affecting outcomes. RESULTS Seventy-eight patients (74%) required neonatal first-stage palliation, including modified Blalock-Taussig shunt (n = 46, 44%), Norwood (n = 18, 17%), and pulmonary artery band (n = 14, 13%), whereas 27 (26%) received primary Glenn as their initial surgery. Hospital mortality was 5 patients (4.8%). Competing risks models showed that by 1 year after first-stage surgery, 15% of patients had died and 83% had undergone Glenn. By 5 years after Glenn, 2% of patients had died and 80% had undergone Fontan. Overall 8-year survival was 84%. On multivariable analysis, risk factors for mortality were genetic/extracardiac anomalies (hazard ratio 7.0, 95% confidence interval: 2.4 to 20.6, p < 0.001) and pulmonary atresia (hazard ratio 4.4, 95% confidence interval: 1.6 to 12.2, p = 0.004). Survival was not affected by initial palliation type (p = 0.36), ventriculoarterial discordance (p = 0.25), systemic outflow obstruction (p = 0.84), or arch obstruction (p = 0.62). CONCLUSIONS Despite morphologic and physiologic variations necessitating different palliative sequences, multistage palliation outcomes of various TA subtypes are comparable and generally good, with the exception of patients with associated genetic/extracardiac anomalies. The bulk of mortality is interstage, indicating continued opportunity for improvement in monitoring and managing patients during this critical period.

Computational modeling of Fontan physiology: at the crossroads of pediatric cardiology and biomedical engineering

The Fontan operation has evolved over the last four and a half decades and is now widely applied to patients with various forms of “single ventricle” congenital heart disease. Survival has greatly improved since the early years, but long-term morbidity and mortality continue to occur. Modeling of Fontan geometries, both in vitro and using computational fluid dynamics, has been instrumental in designing novel changes to Fontan’s operation, including the application of staged surgical procedures leading to a total cavopulmonary anastomosis, lateral tunnel, extracardiac conduit, and most recently bifurcated Y-graft modifications. In this review, the history of modeling of Fontan physiologies, current state-of-the-art methodologies, and future directions are explored. The application of these techniques to cardiac magnetic resonance imaging to construct patient specific anatomies offers the possibility of individualized surgical planning to optimize hemodynamics, including minimizing power loss, balancing hepatic factor distribution, and ultimately improving patient outcomes.

Quantitative Assessment of Ventricular Septal Contour for Estimation of Right Ventricular Pressure

Qualitative assessment of ventricular septal flattening is commonly used in pediatric patients with pulmonary hypertension (PH) who lack adequate tricuspid regurgitation (TR) Doppler signal. We sought to determine the relation between quantitative measures of septal flattening including the eccentricity index (EIs) and a novel marker, the septal flattening angle (SFA) with right ventricular systolic pressure (RVSP).

SURGEM: A solid modeling tool for planning and optimizing pediatric heart surgeries

Abstract Approximately 1% of children are born with a moderate to severe congenital heart defect, and half of them undergo one or more surgeries to fix it. SURGEM, a solid modeling environment, is used to improve surgical outcome by allowing the surgeon to design the geometry for several possible surgical options before the operation and to evaluate their relative merits using computational fluid simulation. We describe here the solid modeling and graphical user interface challenges that we have encountered while developing support for three surgeries: (1) repair of double-outlet right ventricle, which adds a graft wall within the cardiac chambers to split the solid model of the unique ventricle, (2) the Fontan procedure, which routes a graft tube to connect the inferior vena cava to the pulmonary arteries, and (3) stenosis repair, which adds a stent to expand a constricted artery. We describe several solutions that we have developed to address these challenges and to improve the performance, reliability, and usability of SURGEM for these tasks.

Temporal Trends in Utilization of Transthoracic Echocardiography for Common Outpatient Pediatric Cardiology Diagnoses over the Past 15 Years

Background: No data exist regarding the temporal trends in utilization of transthoracic echocardiography (TTE) in an outpatient pediatric cardiology setting. This study evaluates the trends in utilization of TTE for common diagnoses known to have low diagnostic yield and the factors influencing these trends. Methods: Patients evaluated at our pediatric cardiology clinics from January 2000 to December 2014 and discharged with final diagnoses of innocent murmur, noncardiac chest pain, benign syncope, and palpitations were included. Variables collected retrospectively included patient age, sex, insurance type, distance from clinic, and ordering physicians years of experience since fellowship. Results: Of the 74,881 patients seen by 35 physicians, 36,053 (48.1%) had a TTE. The TTE rates increased from the beginning of 2000 to the end of 2004 (5.2% per year; P < .001) and then steadily declined until the end of 2014 (1.6% per year; P < .001). Utilization for noncardiac chest pain remained the highest, and use in infants increased significantly during the study period (P < .001). After adjusting for all other factors, the following variables were associated with higher TTE utilization: younger age, males, Medicaid insurance, increased distance from clinic, and being seen by less experienced physicians. Temporal trends persisted after adjusting for all these factors. Conclusions: After an initial surge in TTE utilization from 2000 to 2004, there was a steady decline. This study identifies some important factors influencing these trends. This information could help design quality interventions, but additional factors need to be explored since the trends persist despite adjusting for these factors.

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.

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.