Transcatheter Axial Pump Use in Pediatric Patients on Veno-Arterial Extracorporeal Membrane Oxygenation: An ACTION Collaborative Experience.

We report the largest pediatric multicenter experience with Impella pump use and peripheral veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support. Utilizing the Advanced Cardiac Therapies Improving Outcomes Network (ACTION) collaborative database, we conducted a retrospective, multicenter study of all patients with cardiogenic shock requiring VA-ECMO support with subsequent Impella implant between October 2014 and December 2021. The primary outcome was defined as death while on Impella support. Secondary outcomes were recovery, transplantation, and transition to durable ventricular assist device (VAD) at the time of Impella explantation. Adverse events were defined according to the ACTION registry criteria. Twenty subjects were supported with Impella; Impella 2.5 (n = 3), CP (n = 12), 5.0/5.5 (n = 5). The median Interquartile range (IQR) age, weight, and body surface area at implantation were 15.6 years (IQR = 13.9-17.2), 65.7 kg (IQR = 53.1-80.7), and 1.74 m2 (IQR = 1.58-1.98). Primary cardiac diagnoses were dilated cardiomyopathy/myocarditis in nine (45%), congenital heart disease in four (20%), graft failure/rejection in four (20%), and three (15%) others. Most common adverse events included hemolysis (50%) and bleeding (20%). There were two deaths (10%) in the cohort. Nine patients (45%) were explanted for recovery, eight (40%) were transitioned to a durable VAD, and one (5%) underwent heart transplantation. Impella percutaneous pump support should be considered in the older pediatric population supported with peripheral VA-ECMO, as a means of left heart decompression, and a strategy to come off ECMO to achieve endpoints of myocardial recovery, transition to a durable VAD, or transplantation.

Chylothorax related to acute SARS-CoV-2 infection in a patient with Noonan syndrome with prior uncomplicated cardiac surgeries.

SARS-CoV-2 is a novel coronavirus that has rarely been associated with chylothorax. Patients with Noonan syndrome are at risk for developing chylothorax, especially after cardiothoracic interventions. We present the case of SARS-CoV-2 infection triggering the underlying tendency of a patient with Noonan syndrome to develop chylothorax who did not develop it even after prior cardiothoracic interventions. Patient presented in respiratory distress without hypoxia and was found, on imaging, to have a large right-sided pleural effusion, which was eventually classified as chylothorax. The patient was then started on a low-fat diet. Chest tube drainage substantially reduced the effusion in size, and it remained stable. Our report highlights that SARS-CoV-2 infection can cause the development of a chylothorax or a chylous effusion in patients with Noonan syndrome or among populations with a similar predisposition. A high index of suspicion in vulnerable patients or those not responding to traditional therapy should exist with providers, thus leading to the testing of the fluid to confirm the diagnosis.

Uncertain benefit of statins in pediatric heart transplant recipients: A PHTS analysis.

BACKGROUND: Cardiac allograft vasculopathy (CAV) is a leading cause of graft failure in pediatric heart transplant recipients (HTRs). Early statin use has been shown to reduce CAV incidence and all-cause mortality in adult HTRs. We sought to evaluate the contemporary prevalence and trends of statin use in pediatric HTRs and the association between statin use with CAV development and graft failure. METHODS: Patients aged <17 years at the time of primary heart transplant who survived to ≥3 years without CAV were identified from the Pediatric Heart Transplant Society database (2001-2018). Statin use in the first 3 years posttransplant was defined as consecutive, intermediate, or absent. Kaplan-Meier survival, multivariable modeling, and propensity score-matched analyses evaluated associations between statin use and CAV incidence and graft survival, with subanalyses performed on subjects aged ≥10 years at transplant. RESULTS: Among 3,485 (of which 1,086 aged ≥10 years) HTRs, 584 (17%) received consecutive statin therapy, 647 (19%) received intermediate use, and 2,254 (65%) received no statin therapy. Statin use varied widely between sites, with increasing use in the ≥10-year-old cohort over time. By multivariate analysis, statin use was not associated with graft loss. Consecutive statin use was also not associated with graft survival or freedom from CAV development when compared to absent statin use in unmatched or propensity-matched analyses. CONCLUSIONS: While statins remain commonly utilized in pediatric HTRs, early consecutive statin therapy did not decrease CAV incidence or graft loss. The differing effects of statins on CAV development and progression in pediatric vs adult HTRs suggest differing risk and mediating factors and require further study.

Expanding use of the HeartMate 3 ventricular assist device in pediatric and adult patients within the Advanced Cardiac Therapies Improving Outcomes Network (ACTION).

BACKGROUND: We report current outcomes in patients supported with the HeartMate 3 (HM3) ventricular assist device in a multicenter learning network. METHODS: The Advanced Cardiac Therapies Improving Outcomes Network database was queried for HM3 implants between 12/2017 and 5/2022. Clinical characteristics, postimplant course, and adverse events were collected. Patients were stratified according to body surface area (BSA) (<1.4 m2, 1.4-1.8 m2, and >1.8 m2) at device implantation. RESULTS: During the study period, 170 patients were implanted with the HM3 at participating network centers, with median age 15.3years; 27.1% were female. Median BSA was 1.68 m2; the smallest patient was 0.73 m2 (17.7 kg). Most (71.8%) had a diagnosis of dilated cardiomyopathy. With a median support time of 102.5days, 61.2% underwent transplantation, 22.9% remained supported on device, 7.6% died, and 2.4% underwent device explantation for recovery; the remainder had transferred to another institution or transitioned to a different device type. The most common adverse events included major bleeding (20.8%) and driveline infection (12.9%); ischemic and hemorrhagic stroke were encountered in 6.5% and 1.2% of patients, respectively. Patients with BSA <1.4 m2 had a higher incidence of infection, renal dysfunction, and ischemic stroke. CONCLUSIONS: In this updated cohort of predominantly pediatric patients supported with the HM3 ventricular assist device, outcomes are excellent with <8% mortality on device. Device-related adverse events including stroke, infection, and renal dysfunction were more commonly seen in smaller patients, highlighting opportunities for improvements in care.

Solid Organ Transplantation for Children With Neurodevelopmental Disabilities-Ethical Considerations and a Call for Clarity.

Pediatric transplant centers are faced with the difficult task of maximizing the benefit of organs donated for transplantation while also ensuring that all patients undergoing transplant evaluation are fairly considered for this life-saving therapy. Children with neurodevelopmental disabilities are a complex patient population that on occasion may face the need for a solid organ transplant. Several concerns exist regarding transplantation in this population, yet standard transplant inclusion and exclusion criteria do not exist. Here we explore important factors regarding organ transplantation for children with neurodevelopmental disorders, including patient outcomes, quality of life considerations, and the fundamental ethical principles underlying this complex medical decision-making.

Risk of Sudden Death in Patients With RASopathy Hypertrophic Cardiomyopathy.

BACKGROUND: Genetic defects in the RAS/mitogen-activated protein kinase pathway are an important cause of hypertrophic cardiomyopathy (RAS-HCM). Unlike primary HCM (P-HCM), the risk of sudden cardiac death (SCD) and long-term survival in RAS-HCM are poorly understood. OBJECTIVES: The study's objective was to compare transplant-free survival, incidence of SCD, and implantable cardioverter-defibrillator (ICD) use between RAS-HCM and P-HCM patients. METHODS: In an international, 21-center cohort study, we analyzed phenotype-positive pediatric RAS-HCM (n = 188) and P-HCM (n = 567) patients. The between-group differences in cumulative incidence of all outcomes from first evaluation were compared using Gray's tests, and age-related hazard of all-cause mortality was determined. RESULTS: RAS-HCM patients had a lower median age at diagnosis compared to P-HCM (0.9 years [IQR: 0.2-5.0 years] vs 9.8 years [IQR: 2.0-13.9 years], respectively) (P < 0.001). The 10-year cumulative incidence of SCD from first evaluation was not different between RAS-HCM and P-HCM (4.7% vs 4.2%, respectively; P = 0.59). The 10-year cumulative incidence of nonarrhythmic deaths or transplant was higher in RAS-HCM compared with P-HCM (11.0% vs 5.4%, respectively; P = 0.011). The 10-year cumulative incidence of ICD insertions, however, was 5-fold lower in RAS-HCM compared with P-HCM (6.9% vs 36.6%; P < 0.001). Nonarrhythmic deaths occurred primarily in infancy and SCD primarily in adolescence. CONCLUSIONS: RAS-HCM was associated with a higher incidence of nonarrhythmic death or transplant but similar incidence of SCD as P-HCM. However, ICDs were used less frequently in RAS-HCM compared to P-HCM. In addition to monitoring for heart failure and timely consideration of advanced heart failure therapies, better risk stratification is needed to guide ICD practices in RAS-HCM.

The Prevalence and Association of Exercise Test Abnormalities With Sudden Cardiac Death and Transplant-Free Survival in Childhood Hypertrophic Cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) can be associated with an abnormal exercise response. In adults with HCM, abnormal results on exercise stress testing are predictive of heart failure outcomes. Our goal was to determine whether an abnormal exercise response is associated with adverse outcomes in pediatric patients with HCM. METHODS: In an international cohort study including 20 centers, phenotype-positive patients with primary HCM who were <18 years of age at diagnosis were included. Abnormal exercise response was defined as a blunted blood pressure response and new or worsened ST- or T-wave segment changes or complex ventricular ectopy. Sudden cardiac death (SCD) events were defined as a composite of SCD and aborted sudden cardiac arrest. Using Kaplan-Meier survival, competing outcomes, and Cox regression analyses, we analyzed the association of abnormal exercise test results with transplant and SCD event-free survival. RESULTS: Of 724 eligible patients, 630 underwent at least 1 exercise test. There were no major differences in clinical characteristics between those with or without an exercise test. The median age at exercise testing was 13.8 years (interquartile range, 4.7 years); 78% were male and 39% were receiving beta-blockers. A total of 175 (28%) had abnormal test results. Patients with abnormal test results had more severe septal hypertrophy, higher left atrial diameter z scores, higher resting left ventricular outflow tract gradient, and higher frequency of myectomy compared with participants with normal test results (P<0.05). Compared with normal test results, abnormal test results were independently associated with lower 5-year transplant-free survival (97% versus 88%, respectively; P=0.005). Patients with exercise-induced ischemia were most likely to experience all-cause death or transplant (hazard ratio, 4.86 [95% CI, 1.69-13.99]), followed by those with an abnormal blood pressure response (hazard ratio, 3.19 [95% CI, 1.32-7.71]). Exercise-induced ischemia was also independently associated with lower SCD event-free survival (hazard ratio, 3.32 [95% CI, 1.27-8.70]). Exercise-induced ectopy was not associated with survival. CONCLUSIONS: Exercise abnormalities are common in childhood HCM. An abnormal exercise test result was independently associated with lower transplant-free survival, especially in those with an ischemic or abnormal blood pressure response with exercise. Exercise-induced ischemia was also independently associated with SCD events. These findings argue for routine exercise testing in childhood HCM as part of ongoing risk assessment.

Current Practices in Treating Cardiomyopathy and Heart Failure in Duchenne Muscular Dystrophy (DMD): Understanding Care Practices in Order to Optimize DMD Heart Failure Through ACTION.

Cardiac disease has emerged as a leading cause of mortality in Duchenne muscular dystrophy in the current era. This survey sought to identify the diagnostic and therapeutic approach to DMD among pediatric cardiologists in Advanced Cardiac Therapies Improving Outcomes Network. Pediatric cardiology providers within ACTION (a multi-center pediatric heart failure learning network) were surveyed regarding their approaches to cardiac care in DMD. Thirty-one providers from 23 centers responded. Cardiac MRI and Holter monitoring are routinely obtained, but the frequency of use and indications for ordering these tests varied widely. Angiotensin converting enzyme inhibitor and aldosterone antagonist are generally initiated prior to onset of systolic dysfunction, while the indications for initiating beta-blocker therapy vary more widely. Seventeen (55%) providers report their center has placed an implantable cardioverter defibrillator in at least 1 DMD patient, while 11 providers (35%) would not place an ICD for primary prevention in a DMD patient. Twenty-three providers (74%) would consider placement of a ventricular assist device (VAD) as destination therapy (n = 23, 74%) and three providers (10%) would consider a VAD only as bridge to transplant. Five providers (16%) would not consider VAD at their institution. Cardiac diagnostic and therapeutic approaches vary among ACTION centers, with notable variation present regarding the use of advanced therapies (ICD and VAD). The network is currently working to harmonize medical practices and optimize clinical care in an era of rapidly evolving outcomes and cardiac/skeletal muscle therapies.

Impact of Genetic Testing for Cardiomyopathy on Emotional Well-Being and Family Dynamics: A Study of Parents and Adolescents.

BACKGROUND: Genetic testing is indicated for children with a personal or family history of hereditary cardiomyopathy to determine appropriate management and inform risk stratification for family members. The implications of a positive genetic result for children can potentially impact emotional well-being. Given the nuances of cardiomyopathy genetic testing for minors, this study aimed to understand how parents involve their children in the testing process and investigate the impact of genetic results on family dynamics. METHODS: A survey was distributed to participants recruited from the Children's Cardiomyopathy Foundation and 7 North American sites in the Pediatric Cardiomyopathy Registry. The survey explored adolescent and parent participants' emotions upon receiving their/their child's genetic results, parent-child result communication and its impact on family functionality, using the McMaster Family Assessment Device. RESULTS: One hundred sixty-two parents of minors and 48 adolescents who were offered genetic testing for a personal or family history of cardiomyopathy completed the survey. Parents whose child had cardiomyopathy were more likely to disclose positive diagnostic genetic results to their child (P=0.014). Parents with unaffected children and positive predictive testing results were more likely to experience negative emotions about the result (P≤0.001) but also had better family functioning scores than those with negative predictive results (P=0.019). Most adolescents preferred results communicated directly to the child, but parents were divided about whether their child's result should first be released to them or their child. CONCLUSIONS: These findings have important considerations for how providers structure genetic services for adolescents and facilitate discussion between parents and their children about results.

Fetal Echocardiography is Useful for Screening Fetuses with a Family History of Cardiomyopathy.

We screened all fetal echocardiograms performed at our institution for the past 5 years for the indication of family history of cardiomyopathy. Twenty-six patients were identified who had fetal echocardiograms performed due to a family history of cardiomyopathy. Three out of 26 patients (11.5%) had findings of decreased ventricular function and dilation consistent with cardiomyopathy. All who had cardiomyopathy on fetal echocardiography had parents with genetic mutations (2 maternal, 1 paternal), including one mother who had a cardiac transplant at age 8 for dilated cardiomyopathy. All 3 affected infants had prenatal planning for high level care and were transferred to our facility immediately after birth for cardiology evaluation and management. 2 patients required inotropic support in the newborn period. One patient was transplanted at age 2 months. One patient required ECMO support for one week and initially recovered, but subsequently required mechanical support and listing for heart transplant. We recommend patients with a strong family history of cardiomyopathy in either parent, especially those with known genetic mutations associated with cardiomyopathy, have fetal echocardiograms performed.

A Validated Model for Sudden Cardiac Death Risk Prediction in Pediatric Hypertrophic Cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy is the leading cause of sudden cardiac death (SCD) in children and young adults. Our objective was to develop and validate a SCD risk prediction model in pediatric hypertrophic cardiomyopathy to guide SCD prevention strategies. METHODS: In an international multicenter observational cohort study, phenotype-positive patients with isolated hypertrophic cardiomyopathy <18 years of age at diagnosis were eligible. The primary outcome variable was the time from diagnosis to a composite of SCD events at 5-year follow-up: SCD, resuscitated sudden cardiac arrest, and aborted SCD, that is, appropriate shock following primary prevention implantable cardioverter defibrillators. Competing risk models with cause-specific hazard regression were used to identify and quantify clinical and genetic factors associated with SCD. The cause-specific regression model was implemented using boosting, and tuned with 10 repeated 4-fold cross-validations. The final model was fitted using all data with the tuned hyperparameter value that maximizes the c-statistic, and its performance was characterized by using the c-statistic for competing risk models. The final model was validated in an independent external cohort (SHaRe [Sarcomeric Human Cardiomyopathy Registry], n=285). RESULTS: Overall, 572 patients met eligibility criteria with 2855 patient-years of follow-up. The 5-year cumulative proportion of SCD events was 9.1% (14 SCD, 25 resuscitated sudden cardiac arrests, and 14 aborted SCD). Risk predictors included age at diagnosis, documented nonsustained ventricular tachycardia, unexplained syncope, septal diameter z-score, left ventricular posterior wall diameter z score, left atrial diameter z score, peak left ventricular outflow tract gradient, and presence of a pathogenic variant. Unlike in adults, left ventricular outflow tract gradient had an inverse association, and family history of SCD had no association with SCD. Clinical and clinical/genetic models were developed to predict 5-year freedom from SCD. Both models adequately discriminated between patients with and without SCD events with a c-statistic of 0.75 and 0.76, respectively, and demonstrated good agreement between predicted and observed events in the primary and validation cohorts (validation c-statistic 0.71 and 0.72, respectively). CONCLUSION: Our study provides a validated SCD risk prediction model with >70% prediction accuracy and incorporates risk factors that are unique to pediatric hypertrophic cardiomyopathy. An individualized risk prediction model has the potential to improve the application of clinical practice guidelines and shared decision making for implantable cardioverter defibrillator insertion. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT0403679.

Successful Allogeneic Stem Cell Transplant in Pediatric Patients With Diminished Left Ventricular Ejection Fractions.

Chemotherapy-associated cardiotoxicity may delay or impair the ability to administer fully myeloablative chemotherapy for stem cell transplant in those with reduced left ventricular ejection fraction. Studies in adults have been inconsistent regarding the value of ejection fraction in predicting cardiotoxicity in the posttransplant period. Recent publications, however, have demonstrated successful stem cell transplantation in adults despite low ejection fractions. This case series highlights 2 pediatric patients who were successfully treated with stem cell transplantation without posttransplant cardiac complications, despite pretransplant ejection fractions of 38% and 29%.

An adult female with 5q34-q35.2 deletion: A rare syndromic presentation of left ventricular non-compaction and congenital heart disease.

Terminal and interstitial deletions of the 5q35 region have been rarely reported in the literature. While a delineated phenotype has been suggested, the range of clinical presentations is unknown due to overall rarity. Cardiac features are of interest because haploinsufficiency of the NKX2-5 gene, located at 5q35.1, has been implicated in congenital heart defects with or without conduction disease. Previous case reports of similar deletions included primarily infants and young children and longitudinal clinical and developmental phenotypic data are currently lacking. We report on a 24-year-old female, the first described adult case with an interstitial 5q34-q35.2 deletion and the third reported case where the cytogenetic abnormality is specified using chromosomal microarray analysis. We include details of her cardiac, developmental, and craniofacial phenotypes. The patient is diagnosed with mild intellectual disability, autism spectrum disorder, limitations in fine and gross motor skills, minor malformations of facial features, and a cardiac phenotype with conduction disease, congenital heart disease, and left ventricular non-compaction dilated cardiomyopathy. This report also reviews the overlapping features in previously published 5q35 deletions and, importantly, provides deeper insight into distal 5q deletions.

Clinical characterisation of a novel SCN5A variant associated with progressive malignant arrhythmia and dilated cardiomyopathy.

INTRODUCTION: The SCN5A gene is implicated in many arrhythmogenic and cardiomyopathic processes. We identified a novel SCN5A variant in a family with significant segregation in individuals affected with progressive sinus and atrioventricular nodal disease, atrial arrhythmia, dilated cardiomyopathy, and early sudden cardiac arrest. METHODS: A patient pedigree was created following the clinical evaluation of three affected individuals, two monozygotic twins and a paternal half-brother, which lead to the evaluation of a paternal half-sister (four siblings with the same father and three mothers) all of whom experienced varying degrees of atrial arrhythmias, conduction disease, and dilated cardiomyopathy in addition to a paternal history of unexplained death in his 50s with similar autopsy findings. The index male underwent sequencing of 58 genes associated with cardiomyopathies. Sanger sequencing was used to provide data for bases with insufficient coverage and for bases in some known regions of genomic segmental duplications. All clinically significant and novel variants were confirmed by independent Sanger sequencing. RESULTS: All relatives tested were shown to have the same SCN5A variant of unknown significance (p. Asp197His) and the monozygotic twins shared a co-occurring NEXN (p. Glu575*). Segregation analysis demonstrates likely pathogenic trait for the SCN5A variant with an additional possible role for the NEXN variant in combination. CONCLUSIONS: There is compelling clinical evidence suggesting that the SCN5A variant p. Asp197His may be re-classified as likely pathogenic based on the segregation analysis of our family of interest. Molecular mechanism studies are pending.

Takotsubo cardiomyopathy secondary to non-accidental trauma presenting as an "unwitnessed" arrest.

Takotsubo cardiomyopathy is characterised by akinesis and ballooning of the left ventricular apex during contraction of the otherwise normal base of the heart. We describe the case of a 7-month-old previously healthy female who presented with an unwitnessed cardiac arrest. Workup raised suspicion for non-accidental trauma. Despite progression to brain death, the severely decreased ventricular function and apical akinesis of the left ventricle improved within 40 hours of admission. This report will familiarise paediatricians with this rare cardiomyopathy and emphasise the importance of considering non-accidental trauma as an inciting event for patients with unwitnessed cardiac arrest found to have decreased ventricular function.

Echocardiographic Guidance During Neonatal and Pediatric Jugular Cannulation for ECMO.

BACKGROUND: Internal jugular vein extracorporeal membrane oxygenation (ECMO) cannula position is traditionally confirmed via plain film. Misplaced cannulae can result in need for repositioning and increased morbidity. Echocardiography (ECHO) may be used during cannulation as a more accurate means of guiding cannula position. This study reviews the effect of a protocol encouraging the use of ECHO at cannulation. METHODS AND MATERIALS: Single institution retrospective review of patients who received ECMO support using jugular venous cannulation. We compared those who underwent ECHO (ECHO+) at the time of cannulation with those who did not (ECHO-). RESULTS: Eighty-nine patients were included: 26 ECHO+, 63 ECHO-. Most ECHO+ patients underwent dual-lumen veno-venous (VV) cannulation (65%); 32% of ECHO- patients had VV support (P = 0.003). There was no difference in the rate of cannula repositioning between the two groups: 8% ECHO+ and 10% ECHO-, P = 0.78. In the VV ECMO subgroup, ECHO+ patients required no repositioning (0/17), while 20% (4/20) of ECHO- VV patients did (P = 0.10). After cannulation, there were 0.58 ECHO studies per patient to verify cannula position in the ECHO+ group compared with 0.22 in the ECHO- group (P = 0.02). Each group had a major mechanical complication: atrial perforation from a guidewire during cannulation in ECHO+ and late atrial perforation from a loose cannula in ECHO-, and there was no difference in minor complications. CONCLUSIONS: ECHO guidance during neonatal and pediatric jugular cannulation for ECMO did not decrease morbidity or reduce the need for cannula repositioning. ECHO may still be a useful adjunct for precise placement of a dual-lumen VV cannula and during difficult cannulations.

Successful treatment of disseminated adenovirus infection with cidofovir and intravenous immunoglobulin in an infant following heart transplant.

For most patients, adenoviruses cause few acute health concerns and are often self-limiting. Patients who are immunocompromised or immunosuppressed, however, are at risk for disseminated adenovirus and suffer high morbidity and mortality, without well-defined treatment options. We report the case of a 9-month-old boy who was successfully treated for disseminated adenovirus infection with intravenous immunoglobulin and cidofovir 3 months post heart transplant, tailored to serum adenoviral load and clinical response. We emphasise the importance of early identification, monitoring, and a potentially novel treatment in the paediatric cardiac transplant population with disseminated adenovirus infection.

Management of Complications Caused by a Massive Left Ventricle Tumor in a Neonate.

We report the case of a neonate born with a giant fibroma occupying the entirety of her left ventricle. Owing to the extensive resection, her postoperative course was complicated by severely diminished left ventricular function and complete heart block necessitating extracorporeal support. Ultimately, cardiac resynchronization therapy was used, after which the infant's ventricular function gradually improved and she was successfully discharged to home.

Consideration of pyloric stenosis as a cause of feeding dysfunction in children with cyanotic heart disease.

Feeding difficulty has been reported at a higher incidence in infants with cyanotic heart disease and single ventricle physiology necessitating specialized feeding strategies. However, structural causes of feed intolerance in this subset of patients should not be ignored. This case series highlights three recent cases of pyloric stenosis in infants with left-sided obstructive lesions at our institution. In all three cases, the initial presumed diagnosis was feeding intolerance related to heart disease, and there was significant clinical improvement following identification and correction of pyloric stenosis.