Statistical shape modeling reveals the link between right ventricular shape, hemodynamic force, and myocardial function in patients with repaired tetralogy of Fallot.

Patients with repaired tetralogy of Fallot (rTOF) can develop chronic pulmonary insufficiency (PI) with right ventricular (RV) dilation, progressive RV dysfunction, and decreased exercise capacity. Pulmonary valve replacement (PVR) can help reduce the amount of PI and RV dilation; however, optimal timing remains controversial; a better understanding of rTOF pathophysiology is of fundamental importance to inform clinical management of patients with rTOF and optimal timing of PVR. In this study, we hypothesize a tight interplay between RV shape, intracardiac biomechanics, and ventricular function in patients with rTOF. To explore this hypothesis and derive quantitative measures, we combined statistical shape modeling with physics-based analysis of in vivo 4D flow data in 36 patients with rTOF. Our study demonstrated for the first time a correlation between regional RV shape variations, hemodynamic forces (HDF), and clinical dysfunction in patients with rTOF. The main findings of this work include 1) general increase in RV size, due to both volume overload and physiological growth, correlated with decrease in strain magnitude in the respective directions, and with increased QRS; 2) regional PI-induced remodeling accounted for ∼10% of the shape variability of the population, and was associated with increased diastolic HDF along the diaphragm-to-right ventricular outflow tract (RVOT) direction, resulting in a net RV deformation along the same direction and decreased tricuspid annular plane systolic excursion (TAPSE); and 3) three shape modes independently correlated with systolic HDF and exercise capacity. Identification of patients based on the shape variations described in this study could help identify those at risk for irreversible dysfunction and guide optimal timing of PVR.NEW & NOTEWORTHY We combine statistical shape modeling with physics-based analysis of 4D flow data to elucidate the interplay between RV shape, hemodynamic forces, and clinical dysfunction in repaired tetralogy of Fallot. We are the first to show that ventricular remodeling is related to hemodynamic force magnitude and direction, global and regional functional parameters, and exercise intolerance. Identification of patients based on the shape variations described in this study could help identify those at risk for irreversible dysfunction.

Impact of ferumoxytol vs gadolinium on 4D flow cardiovascular magnetic resonance measurements in small children with congenital heart disease.

BACKGROUND: Cardiovascular magnetic resonance (CMR) allows for time-resolved three-dimensional phase-contrast (4D Flow) analysis of congenital heart disease (CHD). Higher spatial resolution in small infants requires thinner slices, which can degrade the signal. Particularly in infants, the choice of contrast agent (ferumoxytol vs. gadolinium) may influence 4D Flow CMR accuracy. Thus, we investigated the accuracy of 4D Flow CMR measurements compared to gold standard 2D flow phase contrast (PC) measurements in ferumoxytol vs. gadolinium-enhanced CMR of small CHD patients with shunt lesions. METHODS: This was a retrospective study consisting of CMR studies from complex CHD patients less than 20 kg who had ferumoxytol or gadolinium-enhanced 4D Flow and standard two-dimensional phase contrast (2D-PC) flow collected. 4D Flow clinical software (Arterys) was used to measure flow in great vessels, systemic veins, and pulmonary veins. 4D Flow accuracy was defined as percent difference or correlation against conventional measurements (2D-PC) from the same vessels. Subgroup analysis was performed on two-ventricular vs single-ventricular CHD, arterial vs venous flow, as well as low flows (defined as < 1.5 L/min) in 1V CHD. RESULTS: Twenty-one ferumoxytol-enhanced and 23 gadolinium-enhanced CMR studies were included, with no difference in age (2.1 ± 1.6 vs. 2.3 ± 1.9 years, p = 0.70), patient body surface area (0.50 ± 0.2 vs. 0.52 ± 0.2 m2, p = 0.67), or vessel diameter (11.4 ± 5.2 vs. 12.4 ± 5.6 mm, p = 0.22). Ten CMR studies with single ventricular CHD were included. Overall, ferumoxytol-enhanced 4D flow CMR measurements demonstrated less percent difference to 2D-PC when compared to gadolinium-enhanced 4D Flow CMR studies. In subgroup analyses of arterial vs. venous flows (high velocity vs. low velocity) and low flow in single ventricle CHD, ferumoxytol-enhanced 4D Flow CMR measurements had stronger correlation to 2D-PC CMR. The contrast-to-noise ratio (CNR) in ferumoxytol-enhanced studies was higher than the CNR in gadolinium-enhanced studies. CONCLUSIONS: Ferumoxytol-enhanced 4D Flow CMR has improved accuracy when compared to gadolinium 4D Flow CMR, particularly for infants with small vessels in CHD.

Combining patient-specific, digital 3D models with tele-education for adolescents with CHD.

INTRODUCTION: Adolescents with CHD require transition to specialised adult-centred care. Previous studies have shown that adolescents' knowledge of their medical condition is correlated with transition readiness. Three-dimensional printed models of CHD have been used to educate medical trainees and patients, although no studies have focused on adolescents with CHD. This study investigates the feasibility of combining patient-specific, digital 3D heart models with tele-education interventions to improve the medical knowledge of adolescents with CHD. METHODS: Adolescent patients with CHD, aged between 13 and 18 years old, were enrolled and scheduled for a tele-education session. Patient-specific digital 3D heart models were created using images from clinically indicated cardiac magnetic resonance studies. The tele-education session was performed using commercially available, web-conferencing software (Zoom, Zoom Video Communications Inc.) and a customised software (Cardiac Review 3D, Indicated Inc.) incorporating an interactive display of the digital 3D heart model. Medical knowledge was assessed using pre- and post-session questionnaires that were scored by independent reviewers. RESULTS: Twenty-two adolescents completed the study. The average age of patients was 16 years old (standard deviation 1.5 years) and 56% of patients identified as female. Patients had a variety of cardiac defects, including tetralogy of Fallot, transposition of great arteries, and coarctation of aorta. Post-intervention, adolescents' medical knowledge of their cardiac defects and cardiac surgeries improved compared to pre-intervention (p < 0.01). CONCLUSIONS: Combining patient-specific, digital 3D heart models with tele-education sessions can improve adolescents' medical knowledge and may assist with transition to adult-centred care.

Moving beyond size: vorticity and energy loss are correlated with right ventricular dysfunction and exercise intolerance in repaired Tetralogy of Fallot.

BACKGROUND: The global effect of chronic pulmonary regurgitation (PR) on right ventricular (RV) dilation and dysfunction in repaired Tetralogy of Fallot (rTOF) patients is well studied by cardiovascular magnetic resonance (CMR). However, the links between PR in the RV outflow tract (RVOT), RV dysfunction and exercise intolerance are not clarified by conventional measurements. Not all patients with RV dilation share the same intracardiac flow characteristics, now measurable by time resolved three-dimensional phase contrast imaging (4D flow). In our study, we quantified regional vorticity and energy loss in rTOF patients and correlated these parameters with RV dysfunction and exercise capacity. METHODS: rTOF patients with 4D flow datasets were retrospectively analyzed, including those with transannular/infundibular repair and conduit repair. Normal controls and RV dilation patients with atrial-level shunts (Qp:Qs > 1.2:1) were included for comparison. 4D flow was post-processed using IT Flow (Cardioflow, Japan). Systolic/diastolic vorticity (ω, 1/s) and viscous energy loss (VEL, mW) in the RVOT and RV inflow were measured. To characterize the relative influence of diastolic vorticity in the two regions, an RV Diastolic Vorticity Quotient (ωRVOT-Diastole/ωRV Inflow-Diastole, RV-DVQ) was calculated. Additionally, RVOT Vorticity Quotient (ωRVOT-Diastole/ωRVOT-Systole, RVOT-VQ) and RVOT Energy Quotient (VELRVOT-Diastole/VELRVOT-Systole, RVOT-EQ) was calculated. In rTOF, measurements were correlated against conventional CMR and exercise stress test results. RESULTS: 58 rTOF patients, 28 RV dilation patients and 12 controls were included. RV-DVQ, RVOT-VQ, and RVOT-EQ were highest in rTOF patients with severe PR compared to rTOF patients with non-severe PR, RV dilation and controls (p < 0.001). RV-DVQ positively correlated with RV end-diastolic volume (0.683, p < 0.001), PR fraction (0.774, p < 0.001) and negatively with RV ejection fraction (- 0.521, p = 0.003). Both RVOT-VQ, RVOT-EQ negatively correlated with VO2-max (- 0.587, p = 0.008 and - 0.617, p = 0.005) and % predicted VO2-max (- 0.678, p = 0.016 and - 0.690, p = 0.001). CONCLUSIONS: In rTOF patients, vorticity and energy loss dominate the RVOT compared to tricuspid inflow, correlating with RV dysfunction and exercise intolerance. These 4D flow-based measurements may be sensitive biomarkers to guide surgical management of rTOF patients.

Altered hemodynamics by 4D flow cardiovascular magnetic resonance predict exercise intolerance in repaired coarctation of the aorta: an in vitro study.

BACKGROUND: Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair. Altered flow patterns have been identified due to abnormal aortic arch geometry. Our previous work demonstrated aorta size mismatch to be associated with exercise intolerance in this population. In this study, we studied aortic flow patterns during simulations of exercise in repaired CoA using 4D flow cardiovascular magnetic resonance (CMR) using aortic replicas connected to an in vitro flow pump and correlated findings with exercise stress test results to identify biomarkers of exercise intolerance. METHODS: Patients with CoA repair were retrospectively analyzed after CMR and exercise stress test. Each aorta was manually segmented and 3D printed. Pressure gradient measurements from ascending aorta (AAo) to descending aorta (DAo) and 4D flow CMR were performed during simulations of rest and exercise using a mock circulatory flow loop. Changes in wall shear stress (WSS) and secondary flow formation (vorticity and helicity) from rest to exercise were quantified, as well as estimated DAo Reynolds number. Parameters were correlated with percent predicted peak oxygen consumption (VO2max) and aorta size mismatch (DAAo/DDAo). RESULTS: Fifteen patients were identified (VO2max 47 to 126% predicted). Pressure gradient did not correlate with VO2max at rest or exercise. VO2max correlated positively with the change in peak vorticity (R = 0.55, p = 0.03), peak helicity (R = 0.54, p = 0.04), peak WSS in the AAo (R = 0.68, p = 0.005) and negatively with peak WSS in the DAo (R = - 0.57, p = 0.03) from rest to exercise. DAAo/DDAo correlated strongly with change in vorticity (R = - 0.38, p = 0.01), helicity (R = - 0.66, p = 0.007), and WSS in the AAo (R = - 0.73, p = 0.002) and DAo (R = 0.58, p = 0.02). Estimated DAo Reynolds number negatively correlated with VO2max for exercise (R = - 0.59, p = 0.02), but not rest (R = - 0.28, p = 0.31). Visualization of streamline patterns demonstrated more secondary flow formation in aortic arches with better exercise capacity, larger DAo, and lower Reynolds number. CONCLUSIONS: There are important associations between secondary flow characteristics and exercise capacity in repaired CoA that are not captured by traditional pressure gradient, likely due to increased turbulence and inefficient flow. These 4D flow CMR parameters are a target of investigation to identify optimal aortic arch geometry and improve long term clinical outcomes after CoA repair.

Society for Cardiovascular Magnetic Resonance 2020 Case of the Week series.

The Society for Cardiovascular Magnetic Resonance (SCMR) is an international society focused on the research, education, and clinical application of cardiovascular magnetic resonance (CMR). Case of the week is a case series hosted on the SCMR website ( https://www.scmr.org ) that demonstrates the utility and importance of CMR in the clinical diagnosis and management of cardiovascular disease. Each case consists of the clinical presentation and a discussion of the condition and the role of CMR in diagnosis and guiding clinical management. The cases are all instructive and helpful in the approach to patient management. We present a digital archive of the 2020 Case of the Week series of 11 cases as a means of further enhancing the education of those interested in CMR and as a means of more readily identifying these cases using a PubMed or similar search engine.

Normal right and left ventricular volumes prospectively obtained from cardiovascular magnetic resonance in awake, healthy, 0- 12 year old children.

INTRODUCTION: Pediatric z scores are necessary to describe size and structure of the heart in growing children, however, development of an accurate z score calculator requires robust normal datasets, which are difficult to obtain with cardiovascular magnetic resonance (CMR) in children. Motion-corrected (MOCO) cines from re-binned, reconstructed real-time cine offer a free-breathing, rapid acquisition resulting in cines with high spatial and temporal resolution. In combination with child-friendly positioning and entertainment, MOCO cine technique allows for rapid cine volumetry in patients of all ages without sedation. Thus, our aim was to prospectively enroll normal infants and children birth-12 years for creation and validation of a z score calculator describing normal right ventricular (RV) and left ventricular (LV) size. METHODS: With IRB approval and consent/assent, 149 normal children successfully underwent a brief noncontrast CMR on a 1.5 T scanner including MOCO cines in the short axis, and RV and LV volumes were measured. 20% of scans were re-measured for interobserver variability analyses. A general linear modeling (GLM) framework was employed to identify and properly represent the relationship between CMR-based assessments and anthropometric data. Scatter plots of model fit and Akaike's information criteria (AIC) results were used to guide the choice among alternative models. RESULTS: A total of 149 subjects aged 22 days-12 years (average 5.1 ± 3.6 years), with body surface area (BSA) range 0.21-1.63 m2 (average 0.8 ± 0.35 m2) were scanned. All ICC values were > 95%, reflecting excellent agreement between raters. The model that provided the best fit of volume measure to the data included BSA with higher order effects and gender as independent variables. Compared with earlier z score models, there is important additional growth inflection in early toddlerhood with similar z score prediction in later childhood. CONCLUSIONS: Free-breathing, MOCO cines allow for accurate, reliable RV and LV volumetry in a wide range of infants and children while awake. Equations predicting fit between LV and RV normal values and BSA are reported herein for purposes of creating z scores. TRIAL REGISTRATION: clinicaltrials.gov NCT02892136, Registered 7/21/2016.

Computational Study of Pulmonary Flow Patterns After Repair of Transposition of Great Arteries.

Patients that undergo the arterial switch operation (ASO) to repair transposition of great arteries (TGA) can develop abnormal pulmonary trunk morphology with significant long-term complications. In this study, cardiovascular magnetic resonance was combined with computational fluid dynamics to investigate the impact of the postoperative layout on the pulmonary flow patterns. Three ASO patients were analyzed and compared to a volunteer control. Results showed the presence of anomalous shear layer instabilities, vortical and helical structures, and turbulent-like states in all patients, particularly as a consequence of the unnatural curvature of the pulmonary bifurcation. Streamlined, mostly laminar flow was instead found in the healthy subject. These findings shed light on the correlation between the post-ASO anatomy and the presence of altered flow features, and may be useful to improve surgical planning as well as the long-term care of TGA patients.

Usage of 3D models of tetralogy of Fallot for medical education: impact on learning congenital heart disease.

BACKGROUND: Congenital heart disease (CHD) is the most common human birth defect, and clinicians need to understand the anatomy to effectively care for patients with CHD. However, standard two-dimensional (2D) display methods do not adequately carry the critical spatial information to reflect CHD anatomy. Three-dimensional (3D) models may be useful in improving the understanding of CHD, without requiring a mastery of cardiac imaging. The study aimed to evaluate the impact of 3D models on how pediatric residents understand and learn about tetralogy of Fallot following a teaching session. METHODS: Pediatric residents rotating through an inpatient Cardiology rotation were recruited. The sessions were randomized into using either conventional 2D drawings of tetralogy of Fallot or physical 3D models printed from 3D cardiac imaging data sets (cardiac MR, CT, and 3D echocardiogram). Knowledge acquisition was measured by comparing pre-session and post-session knowledge test scores. Learner satisfaction and self-efficacy ratings were measured with questionnaires filled out by the residents after the teaching sessions. Comparisons between the test scores, learner satisfaction and self-efficacy questionnaires for the two groups were assessed with paired t-test. RESULTS: Thirty-five pediatric residents enrolled into the study, with no significant differences in background characteristics, including previous clinical exposure to tetralogy of Fallot. The 2D image group (n = 17) and 3D model group (n = 18) demonstrated similar knowledge acquisition in post-test scores. Residents who were taught with 3D models gave a higher composite learner satisfaction scores (P = 0.03). The 3D model group also had higher self-efficacy aggregate scores, but the difference was not statistically significant (P = 0.39). CONCLUSION: Physical 3D models enhance resident education around the topic of tetralogy of Fallot by improving learner satisfaction. Future studies should examine the impact of models on teaching CHD that are more complex and elaborate.

Unplanned admissions to a pediatric cardiac critical care unit: a review of 2 years' experience.

OBJECTIVES: Unplanned admissions to the pediatric cardiac ICU may be a large and high-risk group. Our study describes the frequency of unplanned pediatric cardiac ICU admissions, their admission data, and outcomes. DESIGN: All admissions to a pediatric cardiac ICU over 2 years were reviewed and those that were unplanned were identified for a detailed chart abstraction. Demographic, laboratory, diagnostic, and outcome data were collected. Readmission or admission for adverse event was noted. SETTING: Single, tertiary, pediatric cardiac center. PATIENTS: All patients admitted unexpectedly to the pediatric cardiac critical care unit between May 2008 and May 2010. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: There were 1,203 admissions to the cardiac ICU, and 426 (35%) were unplanned. The most common reasons for admission were new heart disease (25%), infection (19%), arrhythmia (13%), and congestive heart failure (11%). The majority of unplanned admissions (62%) occurred at night. Shock was present at admission in 18.5% of patients. Structural heart disease was present in 79%, and 39% of those were patients with single ventricle. Overall mortality among unplanned admissions was 7.3%, which is higher than that reported for elective surgical admissions. Mortality for the subset of patients readmitted within 30 days was 5.5%. Mean creatinine at admission was higher among nonsurvivors (0.7) than survivors (0.5). CONCLUSIONS: Unplanned admissions accounted for over one third of all admissions and had a high mortality rate. The majority of these occur at night, which may affect staffing models. Acute deterioration leading to unplanned admission, rather than readmission status, may be the driving factor in increased mortality. However, the risk of readmission, lower renal function, or other indices may identify patients at higher risk of an unplanned admission. Continued efforts to identify patients at risk for unplanned admissions are warranted given the outcomes in this cohort.

Discordance interpretation of left ventricular size between echocardiography and cardiac magnetic resonance in pediatric patients with aortic/mitral regurgitation.

PURPOSE: This study investigated discordance between echocardiography (echo) and cardiac magnetic resonance (CMR) measurements of the left ventricle (LV) in pediatric patients with aortic and/or mitral regurgitation (AR/MR). METHODS: Retrospective cohort study of pediatric patients. The cohorts were comprised of patients with AR/MR vs. non-AR/MR. Left ventricular end diastolic volume (LVEDV) by CMR and left ventricular internal diameter diastolic (LVIDd) by echo were obtained from clinical reports then echo images were reviewed to remeasure LVEDV by bullet method. Left ventricular internal diameter systolic (LVIDs) and left ventricular ejection fraction (LVEF) measurements by echo and LVEF by CMR were obtained from clinical reports. Fractional shortening (FS%) was recalculated. Z-scores were calculated using normative data. Correlation between echo and CMR LV measurements was assessed using correlation coefficients. Bland-Altman plots assessed bias between imaging modalities. Receiver operator characteristic (ROC) analysis was performed for detection of LV enlargement and LV dysfunction. RESULTS: AR/MR patients had greater discrepancy in LV size interpretation by Z-score compared to non-AR/MR patients. This discrepancy persisted when the bullet method short axis measurements were incorporated. There was negative bias in echo-based measurements compared to CMR. The diagnostic performance of echo in identifying moderate LV enlargement was worse for AR/MR pediatrics patients. CONCLUSION: The discordant interpretation of LV size by echo compared to CMR is worse in pediatric patients with AR/MR when compared to patients without AR/MR even when short axis measurements are incorporated. This finding suggests non-uniform geometrical changes in the LV as it enlarges due to AR/MR.

Tetralogy of Fallot regurgitation energetics and kinetics: an intracardiac flow analysis of the right ventricle using computational fluid dynamics.

Repaired Tetralogy of Fallot (rTOF) patients suffer from pulmonary regurgitation and may require pulmonary valve replacement (PVR). Cardiac magnetic resonance imaging (cMRI) guides therapy, but conventional measurements do not quantify the intracardiac flow effects from pulmonary regurgitation or PVR. This study investigates intracardiac flow parameters of the right ventricle (RV) of rTOF by computational fluid dynamics (CFD). cMRI of rTOF patients and controls were retrospectively included. Feature-tracking captured RV endocardial contours from long-axis/short-axis cine. Ventricular motion was reconstructed via diffeomorphic mapping, serving as domain boundary for CFD simulations. Vorticity (1/s), viscous energy loss (ELoss, mJ/L) and turbulent kinetic energy (TKE, mJ/L) were quantified in RV outflow tract (RVOT) and RV inflow. These parameters were normalized against total RV kinetic energy (KE) and RV inflow vorticity to derive dimensionless metrics. Vorticity contours by Q-criterion were qualitatively compared. rTOF patients (n = 15) had mean regurgitant fraction 38 ± 12% and RV size 162 ± 35 mL/m2. Compared to controls (n = 12), rTOF had increased RVOT vorticity (142.6 ± 75.6/s vs. 40.4 ± 11.8/s, p < 0.0001), Eloss (55.6 ± 42.5 vs. 5.2 ± 4.4 mJ/L, p = 0.0004), and TKE (5.7 ± 5.9 vs. 0.84 ± 0.46 mJ/L, p = 0.0003). After PVR, there was decrease in normalized RVOT Eloss/TKE (p = 0.0009, p = 0.029) and increase in normalized tricuspid inflow vorticity/KE (p = 0.0136, p = 0.043), corresponding to reorganization of the "donut"-shaped tricuspid ring-vortex. The intracardiac flow in rTOF patients can be simulated to determine the impact of PVR and improve the clinical indications guided by cardiac imaging.

Congenital Heart Disease Illustrated: Use of Cross-sectional Imaging in Pediatric Cardiology.

In the modern era of cardiac imaging, there is increasing use of cardiac computed tomography and cardiac magnetic resonance for visualization of congenital heart disease (CHD). Advanced visualization techniques such as virtual dissection, 3-dimensional modeling, and 4-dimensional flow are also commonly used in clinical practice. This review highlights such methods in five common forms of CHD, including double outlet right ventricle, common arterial trunk, sinus venosus defects, Tetralogy of Fallot variants, and heterotaxy, providing visualizations of pathology in both conventional and novel formats.

Enhanced echocardiographic assessment of intracardiac flow in congenital heart disease.

BACKGROUND: 4D flow magnetic resonance imaging (4D flow MRI) can assess and measure the complex flow patterns of the right ventricle (RV) in congenital heart diseases, but its limited availability makes the broad application of intracardiac flow assessment challenging. Color Doppler imaging velocity reconstruction from conventional echocardiography is an emerging alternative, but its validity against 4D flow MRI needs to be established. OBJECTIVE: To compare intracardiac flow parameters measured by color Doppler velocity reconstruction (DoVeR) against parameters measured from 4D flow MRI. METHODS: We analyzed 20 subjects, including 7 normal RVs and 13 abnormal RVs (10 with repaired Tetralogy of Fallot, and 3 with atrial-level shunts). Intracardiac flow parameters such as relative pressure difference, vortex strength, total kinetic energy, and viscous energy loss were quantified using DoVeR and 4D flow MRI. The agreement between the two methods was determined by comparing the spatial fields and quantifying the cross-correlation and normalized difference between time-series measurements. RESULTS: The hemodynamic parameters obtained from DoVeR and 4D flow MRI showed similar flow characteristics and spatial distributions. The time evolutions of the parameters were also in good agreement between the two methods. The median correlation coefficient between the time-series of any parameter was between 0.87 and 0.92, and the median L2-norm deviation was between 10% to 14%. CONCLUSIONS: Our study shows that DoVeR is a reliable alternative to 4D flow MRI for quantifying intracardiac hemodynamic parameters in the RV.

Pressure boundary conditions for immersed-boundary methods.

Immersed boundary methods have seen an enormous increase in popularity over the past two decades, especially for problems involving complex moving/deforming boundaries. In most cases, the boundary conditions on the immersed body are enforced via forcing functions in the momentum equations, which in the case of fractional step methods may be problematic due to: i) creation of slip-errors resulting from the lack of explicitly enforcing boundary conditions on the (pseudo-)pressure on the immersed body; ii) coupling of the solution in the fluid and solid domains via the Poisson equation. Examples of fractional-step formulations that simultaneously enforce velocity and pressure boundary conditions have also been developed, but in most cases the standard Poisson equation is replaced by a more complex system which requires expensive iterative solvers. In this work we propose a new formulation to enforce appropriate boundary conditions on the pseudo-pressure as part of a fractional-step approach. The overall treatment is inspired by the ghost-fluid method typically utilized in two-phase flows. The main advantage of the algorithm is that a standard Poisson equation is solved, with all the modifications needed to enforce the boundary conditions being incorporated within the right-hand side. As a result, fast solvers based on trigonometric transformations can be utilized. We demonstrate the accuracy and robustness of the formulation for a series of problems with increasing complexity.

In vitro investigation of axial mechanical support devices implanted in the novel convergent cavopulmonary connection Fontan.

OBJECTIVES: The 2 opposing inflows and 2 outflows in a total cavopulmonary connection make mechanical circulatory support (MCS) extremely challenging. We have previously reported a novel convergent cavopulmonary connection (CCPC) Fontan design that improves baseline characteristics and provides a single inflow and outflow, thus simplifying MCS. This study aims to assess the feasibility of MCS of this novel configuration using axial flow pumps in an in vitro benchtop model. METHODS: Three-dimensional segmentations of 12 single-ventricle patients (body surface area 0.5-1.75 m2) were generated from cardiovascular magnetic resonance images. The CCPC models were designed by connecting the inferior vena cava and superior vena cava to a shared conduit ascending to the pulmonary arteries, optimized in silico. The 12 total cavopulmonary connection and their corresponding CCPC models underwent in vitro benchtop characterization. Two MCS devices were used, the Impella RP® and the PediPump. RESULTS: MCS successfully and symmetrically reduced the pressure in both vena cavae by >20 mmHg. The devices improved the hepatic flow distribution balance of all CCPC models (Impella RP®P = 0.045, PediPump P = 0.055). CONCLUSIONS: The CCPC Fontan design provides a feasible MCS solution for a failing Fontan by balancing hepatic flow distribution and symmetrically decompressing the central venous pressure. Cardiac index may also improve with MCS. Additional studies are needed to evaluate this concept for managing Fontan failure.

Aortic arch shape after arch repair predicts exercise capacity: a multicentre analysis.

Aims: Coarctation of the aorta is associated with long-term morbidity including decreased exercise capacity, despite successful repair. In the absence of discrete recoarctation, the haemodynamic mechanism remains unknown. This multicentre study evaluated the relationship between aorta shape, flow, and exercise capacity in patients after arch repair, specifically through the lens of aortic size mismatch and descending aortic (DAo) flow and their association with exercise. Methods and results: Cardiac magnetic resonance, cardiopulmonary exercise test, and echocardiogram data within 1 year were analysed from 58 patients (age 28 ± 10 years, 48% male) across four centres with history of isolated arch repair. Aortic arch measurements were correlated with % predicted VO2max with subgroup analyses of those with residual arch obstruction, bicuspid aortic valve, and hypertension. Ascending aorta (AAo) to DAo diameter ratio (DAAo/DDAo) was negatively correlated with % predicted VO2max. %DAo flow positively correlated with VO2max. Sub-analyses demonstrated that the negative correlation of DAAo/DDAo with VO2max was maintained only in patients without arch obstruction and with a bicuspid aortic valve. Smaller aortic arch measurements were associated with both hypertension and exercise-induced hypertension. Conclusion: Aorta size mismatch, due to AAo dilation or small DAo, and associated decreased %DAo flow, correlated significantly with decreased exercise capacity after aortic arch repair. These correlations were stronger in patients without arch obstruction and with a bicuspid aortic valve. Aorta size mismatch and %DAo flow capture multiple mechanisms of altered haemodynamics beyond blood pressure gradient or discrete obstruction and can inform the definition of a successful repair.

Patient-specific tissue engineered vascular graft for aortic arch reconstruction.

Objectives: The complexity of aortic arch reconstruction due to diverse 3-dimensional geometrical abnormalities is a major challenge. This study introduces 3-dimensional printed tissue-engineered vascular grafts, which can fit patient-specific dimensions, optimize hemodynamics, exhibit antithrombotic and anti-infective properties, and accommodate growth. Methods: We procured cardiac magnetic resonance imaging with 4-dimensional flow for native porcine anatomy (n = 10), from which we designed tissue-engineered vascular grafts for the distal aortic arch, 4 weeks before surgery. An optimal shape of the curved vascular graft was designed using computer-aided design informed by computational fluid dynamics analysis. Grafts were manufactured and implanted into the distal aortic arch of porcine models, and postoperative cardiac magnetic resonance imaging data were collected. Pre- and postimplant hemodynamic data and histology were analyzed. Results: Postoperative magnetic resonance imaging of all pigs with 1:1 ratio of polycaprolactone and poly-L-lactide-co-ε-caprolactone demonstrated no specific dilatation or stenosis of the graft, revealing a positive growth trend in the graft area from the day after surgery to 3 months later, with maintaining a similar shape. The peak wall shear stress of the polycaprolactone/poly-L-lactide-co-ε-caprolactone graft portion did not change significantly between the day after surgery and 3 months later. Immunohistochemistry showed endothelization and smooth muscle layer formation without calcification of the polycaprolactone/poly-L-lactide-co-ε-caprolactone graft. Conclusions: Our patient-specific polycaprolactone/poly-L-lactide-co-ε-caprolactone tissue-engineered vascular grafts demonstrated optimal anatomical fit maintaining ideal hemodynamics and neotissue formation in a porcine model. This study provides a proof of concept of patient-specific tissue-engineered vascular grafts for aortic arch reconstruction.

The current state and potential innovation of fetal cardiac MRI.

Fetal cardiac MRI is a rapidly evolving form of diagnostic testing with utility as a complementary imaging modality for the diagnosis of congenital heart disease and assessment of the fetal cardiovascular system. Previous technical limitations without cardiac gating for the fetal heart rate has been overcome with recent technology. There is potential utility of fetal electrocardiography for direct cardiac gating. In addition to anatomic assessment, innovative technology has allowed for assessment of blood flow, 3D datasets, and 4D flow, providing important insight into fetal cardiovascular physiology. Despite remaining technical barriers, with increased use of fCMR worldwide, it will become an important clinical tool to improve the prenatal care of fetuses with CHD.

Intracardiac Flow Analysis of the Right Ventricle in Pediatric Patients With Repaired Tetralogy of Fallot Using a Novel Color Doppler Velocity Reconstruction.

BACKGROUND: Repaired tetralogy of Fallot (RTOF) patients will develop right ventricular (RV) dysfunction from chronic pulmonary regurgitation (PR). Cardiac magnetic resonance sequences such as four-dimensional flow can demonstrate altered vorticity and flow energy loss (FEL); however, they are not as available as conventional echocardiography (echo). The study determined whether a novel, vendor-independent Doppler velocity reconstruction (DoVeR) could measure RV intracardiac flow in conventional echo of RTOF patients. The primary hypothesis was that DoVeR could detect increased vorticity and diastolic FEL in RTOF patients. METHODS: Repaired tetralogy of Fallot patients with echo were retrospectively paired with age-/size-matched controls. Doppler velocity reconstruction employed the stream function-vorticity equation to approximate intracardiac flow fields from color Doppler. A velocity field of the right ventricle was reconstructed from the apical 4-chamber view. Vortex strength (VS, area integral of vorticity) and FEL were derived from DoVeR. Cardiac magnetic resonance and exercise stress parameters (performed within 1 year of echo) were collected for analysis. RESULTS: Twenty RTOF patients and age-matched controls were included in the study. Mean regurgitant fraction was 40.5% ± 7.6%, and indexed RV end-diastolic volume was 158 ± 36 mL/m2. Repaired tetralogy of Fallot patients had higher total, mean diastolic, and peak diastolic VS (P = .0013, P = .0012, P = .0032, respectively) and higher total, mean diastolic, and peak diastolic body surface area-indexed FEL (P = .0016, P = .0022, P < .001, respectively). Peak diastolic indexed FEL and peak diastolic VS had weak-to-moderate negative correlation with RV ejection fraction (r = -0.52 [P = .019] and r = -0.49 [P = .030], respectively) and left ventricular ejection fraction (r = -0.47 [P = .034] and r = -0.64 [P = .002], respectively). Mean diastolic indexed FEL and VS had moderate-to-strong negative correlation with percent predicted maximal oxygen consumption (r = -0.69 [P = .012] and r = -0.75 [P = .006], respectively). CONCLUSIONS: DoVeR can detect alterations to intracardiac flow in RTOF patients from conventional color Doppler imaging. Echo-based measures of diastolic VS and FEL correlated with ventricular function. DoVeR has the potential to provide serial evaluation of abnormal flow dynamics in RTOF patients.