The Macrophage Landscape Across the Lifespan of a Human Cardiac Allograft.

BACKGROUND: Much of our knowledge of organ rejection after transplantation is derived from rodent models. METHODS: We used single-nucleus RNA sequencing to investigate the inflammatory myocardial microenvironment in human pediatric cardiac allografts at different stages after transplantation. We distinguished donor- from recipient-derived cells using naturally occurring genetic variants embedded in single-nucleus RNA sequencing data. RESULTS: Donor-derived tissue resident macrophages, which accompany the allograft into the recipient, are lost over time after transplantation. In contrast, monocyte-derived macrophages from the recipient populate the heart within days after transplantation and form 2 macrophage populations: recipient MP1 and recipient MP2. Recipient MP2s have cell signatures similar to donor-derived resident macrophages; however, they lack signatures of pro-reparative phagocytic activity typical of donor-derived resident macrophages and instead express profibrotic genes. In contrast, recipient MP1s express genes consistent with hallmarks of cellular rejection. Our data suggest that recipient MP1s activate a subset of natural killer cells, turning them into a cytotoxic cell population through feed-forward signaling between recipient MP1s and natural killer cells. CONCLUSIONS: Our findings reveal an imbalance of donor-derived and recipient-derived macrophages in the pediatric cardiac allograft that contributes to allograft failure.

Organizational Culture as a Determinant of Outcome in Teams: Implications for the Pediatric Cardiac Specialist.

Although enormous effort has focussed on how to build an effective culture in the business community, relatively little effort has addressed how to achieve this in the hospital environment, specifically related to the field of congenital heart disease teams. The examination of culture in pediatric cardiac care is particularly important for several key reasons: first, it represents high-stakes medicine, second, there are multiple stakeholders requiring collaboration between cardiologists, surgeons, anaesthesiologists, perfusionists, nursing staff, and allied health care professionals, and finally, both the patient and the family are intimately involved in the care pathway. This review article investigates some of the critical components to building an effective culture, drawing upon similarities in other disciplines, thereby fostering high performance multidisciplinary teams in congenital cardiology care. Strategies to change culture such as Kotter's model of change are also discussed. High performance teams share one common vital characteristic: psychological safety for team members to speak their minds, thereby fostering an open culture, in which creativity can flourish to facilitate major breakthroughs. Adoption of the "Flight Plan" review promotes patient centric care and champions a psychologically safe culture.

Retrograde cerebral perfusion for intracardiac air embolism in Fontan procedure.

We report the case of a 5-year-old boy who suffered from an intracardiac air influx with suspected cerebral air embolism during the Fontan procedure. We immediately transformed the cardiopulmonary bypass circuit to perform a retrograde cerebral perfusion, which resulted in successful neuroprotection. He was extubated in the operating room without any neurological defects.

Mechanical Circulatory Support for the Failing Sub-Aortic Right Ventricle in Adults.

Patients with ccTGA or d-TGA managed via atrial switch (Mustard or Senning operations) have biventricular circulations with a sub-aortic right ventricle (2V-RV). Other than in a tiny percentage of ccTGA patients, premature heart failure (HF) is common, driven by chronic RV dilatation and dysfunction and/or tricuspid regurgitation. These patients are different from the general HF population in that they are younger, more heterogeneous, are predisposed to pulmonary hypertension and present unique and complex surgical challenges. Despite their young age, they experience disproportionately poor access to advanced therapies and are often disqualified for transplant by pulmonary hypertension, HLA sensitization, program risk-tolerance and psychosocial issues. Mechanical support of the subaortic RV with ventricular assist device (subaortic RVAD, also known as SVAD), although technically challenging, can be an effective alternative to palliative care and offers high likelihood of bridging patients to heart transplant candidacy. In addition, temporary trans-catheter SVAD Impella support has been advantageous for stabilization of decompensated 2V-RV patients or as bridge to durable SVAD support. Improved awareness of and access to specialist ACHD-HF teams offering mechanical support (and transplantation) for 2V-RV patients is increasingly urgent for this aging population, and will improve options and outcomes for these patients as HF emerges.

Associations Between Age at Arterial Switch Operation, Brain Growth, and Development in Infants With Transposition of the Great Arteries.

BACKGROUND: Brain injury, impaired brain growth, and long-term neurodevelopmental problems are common in children with transposition of the great arteries. We sought to identify clinical risk factors for brain injury and poor brain growth in infants with transposition of the great arteries undergoing the arterial switch operation, and to examine their relationship with neurodevelopmental outcome. METHODS: The brains of 45 infants with transposition of the great arteries undergoing surgical repair were imaged pre- and postoperatively using magnetic resonance imaging. Brain weight z scores were calculated based on brain volume and autopsy reference data. Brain injury scores were determined as previously described. Neurodevelopment was assessed at 18 months using the Bayley-III scores of infant development. The relationships between clinical variables, brain injury, perioperative brain growth, and 18-month Bayley-III scores were analyzed. RESULTS: On preoperative imaging, moderate or severe white matter injury was present in 10 of 45 patients, whereas stroke was seen in 4 of 45. A similar prevalence of injury was seen on postoperative imaging, and we were unable to identify any clinical risk factors for brain injury. Brain weight z scores decreased perioperatively in 35 of 45 patients. The presence of a ventricular septal defect ( P=0.009) and older age at surgery ( P=0.007) were associated with impaired perioperative brain growth. When patients were divided into those undergoing surgery during the first 2 weeks of life (32/45) versus those being repaired later (13/45), infants repaired later had significantly worse perioperative brain growth (late repair postoperative brain weight z = -1.0±0.90 versus early repair z = -0.33±0.64; P=0.008). Bayley-III testing scores fell within the normal range for all patients, although age at repair ( P=0.03) and days of open chest ( P=0.03) were associated with a lower composite language score, and length of stay was associated with a lower composite cognitive score ( P=0.02). CONCLUSIONS: Surgery beyond 2 weeks of age is associated with impaired brain growth and slower language development in infants with transposition of the great arteries cared for at our center. Although the mechanisms underlying this association are still unclear, extended periods of cyanosis and pulmonary overcirculation may adversely impact brain growth and subsequent neurodevelopment.

Anomalous origins of the coronary arteries: current knowledge and future perspectives.

PURPOSE OF REVIEW: The purpose of this review is to survey the contemporary literature surrounding congenital anomalies of origin of the coronary arteries and to identify remaining gaps in knowledge. RECENT FINDINGS: In recent years, lineage tracing analyses and mechanistic studies in model organisms have enhanced our understanding of the normal embryologic development of the coronary arteries, and how disruption of this intricate process can lead to congenital coronary anomalies. The true incidence of these anomalies remains unknown. Although a majority of cases are believed to be clinically silent, clinical presentation varies widely, from asymptomatic to sudden cardiac death. Cardiac computed tomography angiography and/or magnetic resonance angiography are the mainstay diagnostic modalities. Management of anomalous coronary arteries depends on the morphology and clinical presentation. Surgery is the gold-standard treatment for anomalous left coronary artery arising from the pulmonary artery and anomalous aortic origin of a coronary artery with intramural or interarterial course. SUMMARY: Several large multicenter initiatives are currently underway and should help address some of the numerous knowledge gaps surrounding the evaluation and management of anomalous coronary arteries.

The Optimal Timing of Stage 2 Palliation for Hypoplastic Left Heart Syndrome: An Analysis of the Pediatric Heart Network Single Ventricle Reconstruction Trial Public Data Set.

BACKGROUND: In infants requiring 3-stage single-ventricle palliation for hypoplastic left heart syndrome, attrition after the Norwood procedure remains significant. The effect of the timing of stage 2 palliation (S2P), a physician-modifiable factor, on long-term survival is not well understood. We hypothesized that an optimal interval between the Norwood and S2P that both minimizes pre-S2P attrition and maximizes post-S2P survival exists and is associated with individual patient characteristics. METHODS: The National Institutes of Health/National Heart, Lung, and Blood Institute Pediatric Heart Network Single Ventricle Reconstruction Trial public data set was used. Transplant-free survival (TFS) was modeled from (1) Norwood to S2P and (2) S2P to 3 years by using parametric hazard analysis. Factors associated with death or heart transplantation were determined for each interval. To account for staged procedures, risk-adjusted, 3-year, post-Norwood TFS (the probability of TFS at 3 years given survival to S2P) was calculated using parametric conditional survival analysis. TFS from the Norwood to S2P was first predicted. TFS after S2P to 3 years was then predicted and adjusted for attrition before S2P by multiplying by the estimate of TFS to S2P. The optimal timing of S2P was determined by generating nomograms of risk-adjusted, 3-year, post-Norwood, TFS versus the interval from the Norwood to S2P. RESULTS: Of 547 included patients, 399 survived to S2P (73%). Of the survivors to S2P, 349 (87%) survived to 3-year follow-up. The median interval from the Norwood to S2P was 5.1 (interquartile range, 4.1-6.0) months. The risk-adjusted, 3-year, TFS was 68±7%. A Norwood-S2P interval of 3 to 6 months was associated with greatest 3-year TFS overall and in patients with few risk factors. In patients with multiple risk factors, TFS was severely compromised, regardless of the timing of S2P and most severely when S2P was performed early. No difference in the optimal timing of S2P existed when stratified by shunt type. CONCLUSIONS: In infants with few risk factors, progressing to S2P at 3 to 6 months after the Norwood procedure was associated with maximal TFS. Early S2P did not rescue patients with greater risk factor burdens. Instead, referral for heart transplantation may offer their best chance at long-term survival. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT00115934.

Long-Term Outcomes of the Ross Procedure Versus Mechanical Aortic Valve Replacement: Propensity-Matched Cohort Study.

BACKGROUND: The ideal aortic valve substitute in young and middle-aged adults remains unknown. We sought to compare the long-term outcomes of patients undergoing the Ross procedure and those receiving a mechanical aortic valve replacement (AVR). METHODS: From 1990 to 2014, 258 patients underwent a Ross procedure and 1444 had a mechanical AVR at a single institution. Patients were matched into 208 pairs through the use of a propensity score. Mean age was 37.2±10.2 years, and 63% were male. Mean follow-up was 14.2±6.5 years. RESULTS: Overall survival was equivalent (Ross versus AVR: hazard ratio, 0.91, 95% confidence interval, 0.38-2.16; P=0.83), although freedom from cardiac- and valve-related mortality was improved in the Ross group (Ross versus AVR: hazard ratio, 0.22; 95% confidence interval, 0.034-0.86; P=0.03). Freedom from reintervention was equivalent after both procedures (Ross versus AVR: hazard ratio, 1.86; 95% confidence interval, 0.76-4.94; P=0.18). Long-term freedom from stroke or major bleeding was superior after the Ross procedure (Ross versus AVR: hazard ratio, 0.09; 95% confidence interval, 0.02-0.31; P<0.001). CONCLUSIONS: Long-term survival and freedom from reintervention were comparable between the Ross procedure and mechanical AVR. However, the Ross procedure was associated with improved freedom from cardiac- and valve-related mortality and a significant reduction in the incidence of stroke and major bleeding. In specialized centers, the Ross procedure represents an excellent option and should be considered for young and middle-aged adults undergoing AVR.

Reduced fetal cerebral oxygen consumption is associated with smaller brain size in fetuses with congenital heart disease.

BACKGROUND: Fetal hypoxia has been implicated in the abnormal brain development seen in newborns with congenital heart disease (CHD). New magnetic resonance imaging technology now offers the potential to investigate the relationship between fetal hemodynamics and brain dysmaturation. METHODS AND RESULTS: We measured fetal brain size, oxygen saturation, and blood flow in the major vessels of the fetal circulation in 30 late-gestation fetuses with CHD and 30 normal controls using phase-contrast magnetic resonance imaging and T2 mapping. Fetal hemodynamic parameters were calculated from a combination of magnetic resonance imaging flow and oximetry data and fetal hemoglobin concentrations estimated from population averages. In fetuses with CHD, reductions in umbilical vein oxygen content (P<0.001) and failure of the normal streaming of oxygenated blood from the placenta to the ascending aorta were associated with a mean reduction in ascending aortic saturation of 10% (P<0.001), whereas cerebral blood flow and cerebral oxygen extraction were no different from those in controls. This accounted for the mean 15% reduction in cerebral oxygen delivery (P=0.08) and 32% reduction cerebral Vo2 in CHD fetuses (P<0.001), which were associated with a 13% reduction in fetal brain volume (P<0.001). Fetal brain size correlated with ascending aortic oxygen saturation and cerebral Vo2 (r=0.37, P=0.004). CONCLUSIONS: This study supports a direct link between reduced cerebral oxygenation and impaired brain growth in fetuses with CHD and raises the possibility that in utero brain development could be improved with maternal oxygen therapy.

MRI reveals hemodynamic changes with acute maternal hyperoxygenation in human fetuses with and without congenital heart disease.

OBJECTIVE: We investigated the physiologic impact of acute maternal hyperoxygenation (MH) in human fetuses with and without congenital heart disease (CHD) using fetal cardiac magnetic resonance (CMR) in order to explore the potential therapeutic benefits of chronic MH. METHODS: We examined 17 normal and 20 late gestation human fetuses with CHD on a 1.5 T CMR system. Flows were measured in major fetal vessels using phase contrast MRI. The T2 of umbilical venous blood was measured using T2 mapping. The measurements were repeated during acute MH. The results were compared using a Student's t-test, with p-value ≤0.05 considered statistically significant. RESULTS: At baseline, the umbilical venous T2 (oxygen saturation) was lower in CHD fetuses than in normals, with significant increase with MH (p = 0.01). Both groups showed significant increase in pulmonary blood flow during MH, which was more dramatic in CHD (p = 0.005). There was a reduction in ductus arteriosus flow in CHD during MH (p = 0.04). There was no significant difference in blood flow in any of the other major vessels. CONCLUSION: This study suggests that fetal MR identifies the expected hemodynamic changes associated with acute MH. MRI could be useful as a method for monitoring the impact of chronic MH in fetuses with CHD.

Single nucleus transcriptome of a "Super RV" shows increased insulin and angiogenesis signaling.

The right ventricle (RV) is one of the four pumping chambers of the heart, pumping blood to the lungs. In severe forms of congenital heart disease and pulmonary hypertension, the RV is made to pump into the systemic circulation. Such systemic RVs typically display early failure due to pressure overload. In rare cases a systemic RV persists into later decades of life - colloquially called a 'Super RV'. Here we present the single-nucleus transcriptome of a systemic RV from a 60-year-old with congenitally corrected transposition of great arteries (ccTGA). Our data shows two specific signaling pathways enriched in the ccTGA RV myocardium. First, we show increased insulin like growth factor (IGF1) signaling within the systemic RV myocardium: there is increased expression of the main receptor IGFR1 within the cardiomyocytes, and IGF1 ligands within the cardiofibroblasts and macrophages. Second, we find increased VEGF and Wnt9 ligand expression in cardiomyocytes and increased VEGF1R and Wnt9 receptors in endothelial cells, which are implicated in angiogenesis. We show that increased insulin and angiogenesis signaling are potentially beneficial RV adaptations to increased pressure overload. This study of an adult systemic RV provides an important framework for understanding RV remodeling to systemic pressures in congenital heart disease and pulmonary hypertension.

Long-term implantable ventricular assist device support in children.

BACKGROUND: In pediatrics, implantable continuous-flow ventricular assist devices (IC-VAD) are often used as a "temporary" support, bridging children to cardiac transplantation during the same hospital admission. METHODS: We conducted a retrospective review of our consecutive patients undergoing IC-VAD support at a tertiary pediatric heart center between 2008 and 2022. RESULTS: We identified 100 IC-VAD implant encounters: HeartWare HVAD (67; 67%), HeartMate II (17; 17%), and HeartMate 3 (16; 16%). The median (range) age, weight, and body surface area at implantation were 14.1 (3.0-56.5) years, 54.8 (13.3-140) kg, and 1.6 (0.6-2.6) m2, respectively. Cardiomyopathy (58; 58%) was the most common etiology, followed by congenital heart disease (37; 37%, including 13 single ventricle). At 6 months of IC-VAD support, 94 (94%) encounters achieved positive outcomes: ongoing support (59; 59%), transplant (33; 33%), and cardiac recovery (2; 2%). Eighty-two encounters (82%) resulted in home discharge with ongoing VAD support, including 38 (46%, out of 82) requiring readmission and 7 (9%, out of 82) resulting in death. There was a clinically significant decrease in morbidity rates before versus after home discharge: bleeding (1.55 vs 0.06), infection (0.84 vs 0.37), and stroke (0.84 vs 0.15 event per patient-year). Overall, 86 encounters (86%) reached positive end points at the latest follow-up (64 transplant, 15 ongoing support, and 7 recovery). Infection (29%; 4 of 14) was the most common cause of negative outcomes, followed by cerebrovascular accident (21%; 3), and unresolved frailty (21%; 3). The estimated overall survival at 1, 2, and 5 years was 90%, 86%, and 77%, respectively. CONCLUSIONS: This study suggests the feasibility of outpatient management of pediatric IC-VAD support. The ability to offer true long-term support maximizes the potential of IC-VAD support, not limited to a temporary bridging tool for heart transplantation.

Adherence to clinical practice guidelines for pulmonary valve intervention after tetralogy of Fallot repair: A nationwide cohort study.

Objectives: To determine guideline adherence pertaining to pulmonary valve replacement (PVR) referral after tetralogy of Fallot (TOF) repair. Methods: Children and adults with cardiovascular magnetic resonance imaging scans and at least moderate pulmonary regurgitation were prospectively enrolled in the Comprehensive Outcomes Registry Late After TOF Repair (CORRELATE). Individuals with previous PVR were excluded. Patients were classified according to presence (+) versus absence (-) of PVR and presence (+) versus absence (-) of contemporaneous guideline satisfaction. A validated score (specific activity scale [SAS]) classified adult symptom status. Results: In total, 498 participants (57% male, mean age 32 ± 14 years) were enrolled from 14 Canadian centers (2013-2020). Mean follow-up was 3.8 ± 1.8 years. Guideline criteria for PVR were satisfied for the majority (n = 422/498, 85%), although referral for PVR occurred only in a minority (n = 167/498, 34%). At PVR referral, most were asymptomatic (75% in SAS class 1). One participant (0.6%) received PVR without meeting criteria (PVR+/indication-). The remainder (n = 75/498, 15%) did not meet criteria for and did not receive PVR (PVR-/indication-). Abnormal cardiovascular imaging was the most commonly cited indication for PVR (n = 61/123, 50%). The SAS class and ratio of right to left end-diastolic volumes were independent predictors of PVR in a multivariable analysis (hazard ratio, 3.33; 95% confidence interval, 1.92-5.8, P < .0001; hazard ratio, 2.78; 95% confidence interval, 2.18-3.55, P < .0001). Conclusions: Although a majority of patients met guideline criteria for PVR, only a minority were referred for intervention. Abnormal cardiovascular imaging was the most common indication for referral. Further research will be necessary to establish the longer-term clinical impact of varying PVR referral strategies.

A randomized controlled trial of prophylactic intra-aortic balloon counterpulsation in high-risk aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: To assess whether prophylactic postoperative intraaortic balloon counterpulsation (IABC) reduces the risk of poor outcome because of vasospasm following aneurysmal subarachnoid haemorrhage relative to conventional hypervolemic therapy (HT). METHODS: This was a single-center, parallel group randomized controlled trial. Patients suffering a subarachnoid hemorrhage at high risk of vasospasm were eligible. Patients were randomly allocated to receive prophylactic IABC (n=35) or HT (n=36). The primary end point was Glasgow Outcome and SF-36 scores assessed at 6 months by a blinded and independent observer and analyzed by intention to treat. Secondary analysis of physiological parameters was by treatment performed. RESULTS: Twenty-seven patients in each arm had a good outcome (P=0.55). There was no statistical difference in mean SF-36 score (t=0.39, P=0.70). There were no long-term complications secondary to IABC. There were no differences in preload (pulmonary artery wedge pressure, P=0.97) or afterload (mean arterial pressure, P=0.97). IABC was associated with a lower cardiac output (P=0.002) and higher systemic vascular resistance (P=0.005), although for both groups mean cardiac output was >6 L/min. Cerebral blood flow was not different between groups: HT=41.5 (SD 7.2), IABP=44.9 (SD 8.6) mL/100 g/min (P=0.14). CONCLUSIONS: In this study, prophylactic IABC did not improve perfusion indices or confer any clinical benefit following subarachnoid haemorrhage in patients with normal cardiac function. The study was small, however, and cannot be extrapolated to patients with cardiac failure and medically refractory symptomatic cerebral vasospasm. Clinical Trial Registration- This trial was not registered because enrolment began prior to July 1, 2005.

TLR-3 receptor activation protects the very immature brain from ischemic injury.

BACKGROUND: We have shown that preconditioning by lipopolysaccharide (LPS) will result in 90% reduction in ischemic brain damage in P7 rats. This robust LPS neuroprotection was not observed in P3 or P5 pups (corresponding to human premature infant). LPS is a known Toll-like receptor 4 (TLR-4) ligand. We hypothesized that TLRs other than TLR-4 may mediate preconditioning against cerebral ischemic injury in the developing brain. METHODS: TLR-2, TLR-3, TLR-4, and TLR-9 expression was detected in brain sections from P3, P5, and P7 rats by immuno-staining. In subsequent experiments, P5 rats were randomly assigned to TLR-3 specific agonist, poly I:C, or saline treated group. At 48 h after the injections, hypoxic-ischemic (HI) injury was induced by unilateral carotid artery ligation followed by hypoxia for 65 min. Brains were removed 1 week after HI injury and infarct volumes were compared in H&E stained sections between the two groups. RESULTS: TLR-2 and TLR-3 were highly expressed in brains of P3 and P5 but not in P7 rats. The number of TLR-4 positive cells was lower in P3 and P5 compared to P7 brains (P <0.05). TLR-3 was predominately expressed in P5 pups (P <0.05). There was no significant difference in TLR-9 expression in the three age groups. There was a significant reduction in infarct volume (P=0.01) in poly I:C compared to saline pre-treated P5 pups. Pre-treatment with poly I:C downregulated NF-κB and upregulated IRF3 expression in P5 rat ischemic brains. Pre-treatment with poly I:C did not offer neuroprotection in P7 rat brains. CONCLUSION: TLRs expression and function is developmentally determined. Poly I:C-induced preconditioning against ischemic injury may be mediated by modulation of TLR-3 signaling pathways. This is the first study to show that TLR-3 is expressed in the immature brain and mediates preconditioning against ischemic injury.

Foetal echocardiographic assessment of borderline small left ventricles can predict the need for postnatal intervention.

BACKGROUND: We sought to prospectively determine foetal echocardiographic factors associated with neonatal interventions in borderline hypoplastic left ventricles. METHODS: Foetuses were included who had a left ventricle that was 2-4 standard deviations below normal for length or diameter and had forward flow across the mitral and aortic valves. Factors associated with an intervention in the first month of life or no need for intervention were sought using univariate and multivariate logistic regression models. RESULTS: From 2005 to 2008, 47 foetuses meeting the criteria had an additional diagnosis (+foetal coarctation/+transverse arch hypoplasia): atrioventricular septal defect 7 (+2/+0), double outlet right ventricle 2 (+0/+0), Shone's complex 19 (+9/+4), and ventricular disproportion 19 (+13/+11; 4 both). There were seven pregnancies terminated, three foetal demises, and five had compassionate care. There were 32 livebirths that either had a biventricular repair (n = 20, n = 2 dead), univentricular palliation (n = 2, both alive), or no intervention (n = 9). Overall survival of livebirths to 6 months of age was 79%. Factors associated with early intervention on first foetal echocardiogram were: obstructed or retrograde arch flow (p = 0.08, odds ratio 3.3), coarctation (p = 0.05, odds ratio 11.4), and left ventricle outflow obstruction (p = 0.05, odds ratio 12.5). Neonatal factors included: Shone's diagnosis (p = 0.02, odds ratio 4.9), bicuspid aortic valve (p = 0.005, odds ratio 11.7), and larger tricuspid valve z-score (p = 0.05, odds ratio 3.6). A neonatal factor associated with no intervention was a larger mitral valve z-score (mean 23.8 versus 24.2 intervention group, p = 0.04, odds ratio 2.8). DISCUSSION: The need for early intervention in foetuses with borderline hypoplastic left ventricle can be predicted by foetal echocardiography.

Impact of a quality improvement initiative with a dedicated anesthesia team on outcomes after surgery for adult congenital heart disease.

Objectives: A quality improvement initiative was introduced to the adult congenital cardiac surgery program at Toronto General Hospital in January 2016. A dedicated Adult Congenital Anesthesia and intensive care unit team was introduced within the cardiac group. The use of factor concentrates was introduced. The study compares perioperative mortality, adverse events, and transfusion burden before and after this process change. Methods: We performed a retrospective analysis of all adult congenital cardiac surgeries from January 2004 to July 2019. Two groups were analyzed: patients undergoing operation before and after 2016. The primary outcome was in-hospital mortality. One-year mortality and prevalence of key morbidities were analyzed as secondary outcomes. A separate analysis looked at patients who had and had not attended an anesthesia-led preassessment clinic. Results: In-hospital mortality was significantly reduced in patients undergoing operation after 2016 (1.1% vs 4.3%, P = .003) despite a higher risk profile. One-year mortality (1.3% vs 5.8%, P = .003) and ventilation times (5.5 hours [3.4-13.0] vs 6.3 hours [4.2-16.2], P = .001) were also reduced. The incidence of stroke and renal failure was similar between groups. Blood product exposure was comparable, but the incidence of chest reopening decreased (1.8% vs 4.8%, P = .022), despite more patients with multiple previous chest wall incisions, on anticoagulation, and with more complex cardiac anatomy. There were no significant outcome differences between those who did or did not attend the preassessment clinic. Conclusions: Both in-hospital and 1-year mortality were significantly reduced after the introduction of a quality improvement program, despite a higher risk profile. Blood product exposure remained unchanged, but there were less chest reopenings.

The Congenital Heart Surgeons' Society Kirklin/Ashburn Fellowship: The Fellows' Perspective.

Since its establishment in 2001, the Congenital Heart Surgeons' Society John W. Kirklin/David Ashburn Fellowship has contributed substantially to the field of congenital heart surgery research while simultaneously training the next generation of surgeon- scientists. To date, ten fellows (and counting) have successfully completed this rigorous training, producing over 40 published articles focused on longitudinal outcomes from the various Congenital Heart Surgeons' Society cohorts. As the Kirklin/Ashburn Fellowship expands and additional fellows matriculate, its legacy, the network of support, and the contribution to congenital heart surgery research will undoubtedly hold strong.

Machine Learning for Prediction of Adverse Cardiovascular Events in Adults With Repaired Tetralogy of Fallot Using Clinical and Cardiovascular Magnetic Resonance Imaging Variables.

BACKGROUND: Existing models for prediction of major adverse cardiovascular events (MACE) after repair of tetralogy of Fallot have been limited by modest predictive capacity and limited applicability to routine clinical practice. We hypothesized that an artificial intelligence model using an array of parameters would enhance 5-year MACE prediction in adults with repaired tetralogy of Fallot. METHODS: A machine learning algorithm was applied to 2 nonoverlapping, institutional databases of adults with repaired tetralogy of Fallot: (1) for model development, a prospectively constructed clinical and cardiovascular magnetic resonance registry; (2) for model validation, a retrospective database comprised of variables extracted from the electronic health record. The MACE composite outcome included mortality, resuscitated sudden death, sustained ventricular tachycardia and heart failure. Analysis was restricted to individuals with MACE or followed ≥5 years. A random forest model was trained using machine learning (n=57 variables). Repeated random sub-sampling validation was sequentially applied to the development dataset followed by application to the validation dataset. RESULTS: We identified 804 individuals (n=312 for development and n=492 for validation). Model prediction (area under the curve [95% CI]) for MACE in the validation dataset was strong (0.82 [0.74-0.89]) with superior performance to a conventional Cox multivariable model (0.63 [0.51-0.75]; P=0.003). Model performance did not change significantly with input restricted to the 10 strongest features (decreasing order of strength: right ventricular end-systolic volume indexed, right ventricular ejection fraction, age at cardiovascular magnetic resonance imaging, age at repair, absolute ventilatory anaerobic threshold, right ventricular end-diastolic volume indexed, ventilatory anaerobic threshold % predicted, peak aerobic capacity, left ventricular ejection fraction, and pulmonary regurgitation fraction; 0.81 [0.72-0.89]; P=0.232). Removing exercise parameters resulted in inferior model performance (0.75 [0.65-0.84]; P=0.002). CONCLUSIONS: In this single-center study, a machine learning-based prediction model comprised of readily available clinical and cardiovascular magnetic resonance imaging variables performed well in an independent validation cohort. Further study will determine the value of this model for risk stratification in adults with repared tetralogy of Fallot.