Representation of Women and Minority Faculty and Fellows in Academic Pediatric Cardiology Training Programs.

BACKGROUND: Studies have shown that diverse care teams optimize patient outcomes. Describing the current representation of women and minorities has been a critical step in improving diversity across several fields. OBJECTIVES: To address the lack of data specific to pediatric cardiology, the authors conducted a national survey. METHODS: U.S. academic pediatric cardiology programs with fellowship training programs were surveyed. Division directors were invited (July 2021 to September 2021) to complete an e-survey of program composition. Underrepresented minorities in medicine (URMM) were characterized using standard definitions. Descriptive analyses at the hospital, faculty, and fellow level were performed. RESULTS: Altogether, 52 of 61 programs (85%) completed the survey, representing 1,570 total faculty and 438 fellows, with a wide range in program size (7-109 faculty, 1-32 fellows). Although women comprise approximately 60% of faculty in pediatrics overall, they made up 55% of fellows and 45% of faculty in pediatric cardiology. Representation of women in leadership roles was notably less, including 39% of clinical subspecialty directors, 25% of endowed chairs, and 16% of division directors. URMM comprise approximately 35% of the U.S. population; however, they made up only 14% of pediatric cardiology fellows and 10% of faculty, with very few in leadership roles. CONCLUSIONS: These national data suggest a "leaky pipeline" for women in pediatric cardiology and very limited presence of URRM overall. Our findings can inform efforts to elucidate underlying mechanisms for persistent disparity and reduce barriers to improving diversity in the field.

Paediatric cardiology training: burnout, fulfilment, and fears.

BACKGROUND: Burnout is well characterised in physicians and residents but not in paediatric cardiology fellows, and few studies follow burnout longitudinally. Training-specific fears have been described in paediatric cardiology fellows but also have not been studied at multiple time points. This study aimed to measure burnout, training-specific fears, and professional fulfilment in paediatric cardiology fellows with the attention to time of year and year-of-training. METHODS: This survey-based study included the Professional Fulfillment Index and the Impact of Events Scale as well as an investigator-designed Fellow Fears Questionnaire. Surveys were distributed at three-time points during the academic year to paediatric cardiology fellows at a large Midwestern training programme. Fellow self-reported gender and year-of-training were collected. Descriptive analyses were performed. RESULTS: 10/17 (59%) of fellows completed all surveys; 60% were female, 40% in the first-year class, 40% in the second-year class, and 20% in the third-year class. At least half of the fellows reported burnout at each survey time point, with lower mean professional fulfilment scores. The second-year class, who rotate primarily in the cardiac ICU, had higher proportions of burnout than the other two classes. At least half of fellows reported that they "often" or "always" worried about not having enough clinical knowledge or skills and about work-life balance. CONCLUSIONS: Paediatric cardiology fellows exhibit high proportions of burnout and training-specific fears. Interventions to mitigate burnout should be targeted specifically to training needs, including during high-acuity rotations.

Hemodynamic and Echocardiographic Predictors of Mortality in Pediatric Patients on Venoarterial Extracorporeal Membrane Oxygenation: A Multicenter Investigation.

BACKGROUND: Venoarterial extracorporeal membrane oxygenation (ECMO) supports patients with advanced cardiac dysfunction; however, mortality occurs in a significant subset of patients. The authors performed a multicenter, prospective study to determine hemodynamic and echocardiographic predictors of mortality in children placed on ECMO for cardiac support. METHODS: Over 8 years, six heart centers prospectively assessed echocardiographic and hemodynamic variables on full and minimum ECMO flow. Sixty-three patients were enrolled, ranging in age from 1 day to 16 years. Hemodynamic measurements included heart rate, vasoactive inotropic score, arteriovenous oxygen difference, pulse pressure, and lactate. Echocardiographic variables included shortening fraction, ejection fraction (EF), right ventricular fractional area change, outflow tract Doppler-derived stroke distance (velocity-time integral [VTI]), and degree of atrioventricular valve regurgitation. Patients were stratified into two groups: those who were able to wean within 48 hours of assessment and survived without ventricular assist devices or orthotopic heart transplantation (successful wean group) and those with unsuccessful weaning. For each patient, variables were compared between full and minimum ECMO flow for each group. RESULTS: Thirty-eight patients (60%) formed the unsuccessful group (two with ventricular assist devices, four with orthotopic heart transplantation, 24 deaths), and 25 constituted the successful wean group. At minimum flow, higher EF (53 ± 16% vs 40 ± 20%, P = .0094), less mitral regurgitation (0.8 ± 0.9 vs 1.4 ± 0.9, P = .0329), and lower central venous pressure (12.0 ± 3.9 vs 14.7 ± 5.4 mm Hg), along with higher VTI (9.0 ± 2.9 vs 6.8 ± 3.7 cm, P = .0154), correlated successful weaning. A longer duration of ECMO (8 vs 5 days, P < .0002) was associated with unsuccessful weaning. Multivariate logistic regression predicted minimum-flow EF and VTI to independently predict successful weaning with cutoff values by receiver operating characteristic analysis of EF > 41% (area under the curve, 0.712; P = .0005) and VTI > 7.9 cm (area under the curve, 0.729; P = .0010). CONCLUSIONS: Diminished VTI or EF during ECMO weaning predicts the need for orthotopic heart transplantation or ventricular assist device support or death in children on ECMO for cardiac dysfunction. Increased postwean central venous pressure or mitral regurgitation along with a prolonged ECMO course also predicted these adverse outcomes. These measurements should be used to help discriminate which patients will require alternative methods of circulatory support for survival.

Echocardiographic Findings Associated with Transplantation-Free Survival and Left Ventricular Systolic Function at Midterm Follow-Up after Ross Procedure in Infants with Critical Aortic Stenosis.

BACKGROUND: The Ross operation is an important option for children with critical aortic stenosis with residual disease, but operation in infancy is associated with significant morbidity and mortality. The aim of this study was to evaluate echocardiographic correlates of transplantation-free survival, reintervention, and left ventricular (LV) function in midterm follow-up. METHODS: This retrospective, single-center study included all infants with critical aortic stenosis who underwent Ross by 1 year of age from January 2000 to September 2018. Serial echocardiograms were analyzed for LV ejection fraction (LVEF) and systolic and diastolic longitudinal strain. The primary outcome was mortality or transplantation; secondary outcomes were reintervention and abnormal LVEF (≤55%). RESULTS: Among 40 infants (30 male [75%]; median age at Ross, 51 days) with median follow-up duration of 3.3 years (interquartile range, 1.0-9.4 years), the primary outcome was met in 11 (28%). Rates of transplantation-free survival was 79%, 77%, and 69% at 1, 5, and 10 years after Ross. Predictors of transplantation or death included neonatal surgery, cross-clamp time, and preoperative left atrial dilatation and lower LVEF. Median freedom from reintervention was 7.1 years after Ross, with no identified associations. LV longitudinal strain improved 1 year after Ross (-21.1 ± 3.8% vs -17.4 ± 5.1%, P = .02), although LVEF did not reach significance. Lower LVEF at 1 year was related to pre-Ross left atrial dilatation (P = .02), abnormal LVEF (P = .04), and lower early diastolic longitudinal strain rate (P = .03). LVEF remained stable 3 years after Ross. CONCLUSIONS: Both transplantation-free survival and normalization of LV function after Ross in infancy are associated with preoperative LV systolic and diastolic measures, highlighting the prognostic value of echocardiography in this population. Further data are necessary in a larger, multicenter cohort to allow more precise risk stratification.

Gestational Age, Birth Weight, and Outcomes Six Years After the Norwood Procedure.

BACKGROUND: Preterm delivery and low birth weight (LBW) are generally associated with worse outcomes in hypoplastic left heart syndrome (HLHS), but an individual preterm or small neonate may do well. We sought to explore the interactions between gestational age, birth weight, and birth weight for gestational age with intermediate outcomes in HLHS. METHODS: We analyzed survival, growth, neurodevelopment, length of stay, and complications to age 6 years in subjects with HLHS from the Single Ventricle Reconstruction trial. Univariate and multivariable survival and regression analyses examined the effects and interactions of LBW (<2500 g), weight for gestational age, and gestational age category. RESULTS: Early-term delivery (n = 234) was more common than term (n = 219) delivery. Small for gestational age (SGA) was present in 41% of subjects, but only 14% had LBW. Preterm, compared with term, delivery was associated with an increased risk of death or transplant at age 6 years (all: hazard ratio = 2.58, confidence interval = 1.43-4.67; Norwood survivors: hazard ratio = 1.96, confidence interval = 1.10-3.49) independent of LBW and weight for gestational age. Preterm delivery, early-term delivery, LBW, and SGA were each associated with lower weight at 6 years. Neurodevelopmental outcomes were worst in the LBW cohort. CONCLUSIONS: Preterm delivery in HLHS was associated with worse survival, even beyond Norwood hospitalization. LBW, SGA, and early-term delivery were associated with worse growth but not survival. LBW was associated with worse neurodevelopment, despite similar length of stay and complications. These data suggest that preterm birth and LBW (although often concomitant) are not equivalent, impacting clinical outcomes through mechanisms independent of perioperative course complexity.

Perinatal Decision Making for Preterm Infants with Congenital Heart Disease: Determinable Risk Factors for Mortality.

For premature infants with congenital heart disease (CHD), it may be unclear when the burdens of treatment outweigh potential benefits. Parents may thus have to choose between comfort care at birth and medical stabilization until surgical repair is feasible. Better defined outcome data, including risk factors for mortality, are needed to counsel expectant parents who are considering intensive care for premature infants with CHD. We sought to evaluate outcomes in this population to inform expectant parents considering intensive versus palliative care at birth. We performed a retrospective cohort study of infants born <34 weeks who received intensive care with critical or moderately severe CHD predicted to require surgery in the neonatal period or the first 6 months of life. 46 % of 54 infants survived. Among non-survivors, 74 % died prior to surgery (median age 24 days). Of the infants that underwent surgery, 75 % survived. Survival was lower among infants <32 weeks gestational age (GA) (p = 0.013), with birth weight (BW) <1500 g (p = 0.011), or with extra-cardiac anomalies (ECA) (p = 0.015). GA and ECA remained significant risk factors for mortality in multiple logistic regression analysis. In summary, GA < 32 weeks, BW < 1500 g, and ECA are determinable prenatally and were significant risk factors for mortality. The majority of infants who survived to cardiac intervention survived neonatal hospitalization, whereas most of the infants who died did so prior to surgery. For some expectant parents, this early declaration of mortality may support a trial of intensive care while avoiding burdensome interventions.

Immune Abnormalities in Fontan Protein-Losing Enteropathy: A Case-Control Study.

OBJECTIVE: To comprehensively characterize the immunologic characteristics of patients with protein-losing enteropathy (PLE) post-Fontan and compare them with patients without PLE post-Fontan. STUDY DESIGN: Patients with PLE post-Fontan and age-matched controls post-Fontan were prospectively studied with laboratory markers of immune function. Infectious history was obtained by interview and chart review. The groups' demographics, cardiac history, immune characteristics, and infection history were compared using appropriate 2-group statistics. RESULTS: A total of 16 patients enrolled (8 patients with PLE and 8 controls). All patients with PLE had lymphopenia compared with 25% of controls (P = .01). All patients with PLE had markedly depressed CD4 T cell counts (median 58 cells/µL) compared with controls (median 450 cells/µL, P = .0002); CD4% was also low in the PLE group (12.3%) and normal in control (36.9%, P = .004). Both groups had mildly depressed CD8 T cells and normal to slightly elevated natural killer and B-cell subsets. A majority of patients with PLE (62.5%) had negative titers to measles, mumps, and rubella vaccination, compared with no control Fontan with a negative titer (P = .03). Despite profoundly low CD4 counts, the frequency of infection was not different between groups with no reported opportunistic infections. CONCLUSIONS: Patients with Fontan-associated PLE have extensive quantitative immune abnormalities, particularly CD4 deficiency. These immune abnormalities are similar to those found in non-Fontan patients with PLE caused by intestinal lymphangiectasia.

Biventricular Badness: Rare Images of Ebstein Anomaly of the Tricuspid Valve in a Patient with Hypoplastic Left Heart Syndrome.

We report a rare case of hypoplastic left heart syndrome coexisting in a patient with Ebstein anomaly of the tricuspid valve, which has previously been described only in pathological studies. A fetal echocardiogram at 27-weeks gestation showed severe aortic stenosis with evolving hypoplastic left heart syndrome, significant endocardial fibroelastosis, a dysplastic tricuspid valve with moderate regurgitation, right atrial and ventricular dilation, and signs of fetal congestive heart failure. Due to inadequate left heart size, the patient was not a candidate for fetal intervention for critical aortic stenosis, and repeat studies showed progression of the lesion through the pregnancy. The infant was delivered at 36-weeks gestation with signs of hydrops, and a postnatal echocardiogram confirmed hypoplastic left heart syndrome as well as severe Ebstein anomaly of the tricuspid valve. The infant did not survive to intervention.

Fontan-associated protein-losing enteropathy and plastic bronchitis.

OBJECTIVE: To characterize the medical history, disease progression, and treatment of current-era patients with the rare diseases Fontan-associated protein-losing enteropathy (PLE) and plastic bronchitis. STUDY DESIGN: A novel survey that queried demographics, medical details, and treatment information was piloted and placed online via a Facebook portal, allowing social media to power the study. Participation regardless of PLE or plastic bronchitis diagnosis was allowed. Case control analyses compared patients with PLE and plastic bronchitis with uncomplicated control patients receiving the Fontan procedure. RESULTS: The survey was completed by 671 subjects, including 76 with PLE, 46 with plastic bronchitis, and 7 with both. Median PLE diagnosis was 2.5 years post-Fontan. Hospitalization for PLE occurred in 71% with 41% hospitalized ≥ 3 times. Therapy varied significantly. Patients with PLE more commonly had hypoplastic left ventricle (62% vs 44% control; OR 2.81, 95% CI 1.43-5.53), chylothorax (66% vs 41%; OR 2.96, CI 1.65-5.31), and cardiothoracic surgery in addition to staged palliation (17% vs 5%; OR 4.27, CI 1.63-11.20). Median plastic bronchitis diagnosis was 2 years post-Fontan. Hospitalization for plastic bronchitis occurred in 91% with 61% hospitalized ≥ 3 times. Therapy was very diverse. Patients with plastic bronchitis more commonly had chylothorax at any surgery (72% vs 51%; OR 2.47, CI 1.20-5.08) and seasonal allergies (52% vs 36%; OR 1.98, CI 1.01-3.89). CONCLUSIONS: Patient-specific factors are associated with diagnoses of PLE or plastic bronchitis. Treatment strategies are diverse without clear patterns. These results provide a foundation upon which to design future therapeutic studies and identify a clear need for forming consensus approaches to treatment.

Echocardiographic factors discriminating biventricular versus univentricular approach in the foetus with borderline left ventricle.

BACKGROUND: The term "borderline left ventricle" describes a small left heart that may be inadequate to provide systemic cardiac output and implies the potential need for a single-ventricle palliation. The aim of this study was to identify foetal echocardiographic features that help discriminate which infants will undergo single-ventricle palliation versus biventricular repair to aid in prenatal counselling. METHODS: The foetal database at our institution was searched to identify all foetuses with borderline left ventricle, as determined subjectively by a foetal cardiologist, from 2000 to 2011. The foetal images were retrospectively analysed for morphologic and physiologic features to determine which best predicted the postnatal surgical choice. RESULTS: Of 39 foetuses identified with borderline left ventricle, 15 were planned for a univentricular approach, and 24 were planned for a biventricular approach. There were significant differences between the two outcome groups in the Z-scores of the mitral valve annulus, left ventricular end-diastolic dimension, aortic valve annulus, and ascending aorta diameter (p<0.05). With respect to discriminating univentricular outcomes, cut-offs of mitral valve Z-score ⩽-1.9 and tricuspid:mitral valve ratio ⩾1.5 were extremely sensitive (100%), whereas a right:left ventricular end-diastolic dimension ratio ⩾2.1 provided the highest specificity (95.8%). CONCLUSION: In foetuses with borderline left ventricle, a mitral valve Z-score ⩾-1.9 or a tricuspid:mitral valve ratio ⩽1.5 suggests a high probability of biventricular repair, whereas a right:left ventricular end-diastolic dimension ratio ⩾2.1 confers a likelihood of single-ventricle palliation.

Development and validation of a fetal cardiovascular disease severity scale.

Prenatal heart disease spans the spectrum of severity from very mild to severe life-threatening conditions. An accepted scale for grading fetal cardiovascular disease severity would aid in anomaly standardization, counseling, and future research. The Fetal Cardiovascular Disease Severity Scale with seven severity grades ranging from mild (grade 1) to severe (grade 7) disease was developed. Severity grade relates to the cardiovascular condition diagnosed by fetal echocardiography, with factors including postnatal intervention, number of interventions anticipated, likelihood of two-ventricle repair versus single-ventricle palliation, and overall prognosis. A survey describing 25 cardiac anomalies was offered to fetal cardiologists at six institutions for validation of scale reliability among practitioners. The study participants graded defects using this scale. A smaller group graded anomalies again more than 2 weeks after the initial survey. The intraclass correlation coefficient (ICC) was used to assess agreement of the respondents. The survey participants were 14 experienced fetal cardiologists: 9 from the Children's Hospital of Philadelphia (CHOP) and 5 from five additional institutions in the United States. The initial survey ICC was high [0.93; 95 % confidence interval (CI) 0.88-0.96]. The subanalysis showed a higher ICC for the participants outside CHOP (0.95; 95 % CI 0.91-0.98 vs. 0.92; 95 % CI 0.86-0.96, respectively). The ICCs were high for all the fetal cardiologists participating in the repeat evaluation, ranging from 0.92 to 0.99 (95 % CI 0.65-1.00). The Fetal Cardiovascular Disease Severity Scale demonstrated good inter- and intrarater reliability among experienced fetal cardiologists and is a valid tool for standardization of prenatal cardiac diagnostic assessment across institutions. The scale has applications for parental counseling and research in fetal cardiovascular disease.

Social media methods for studying rare diseases.

For pediatric rare diseases, the number of patients available to support traditional research methods is often inadequate. However, patients who have similar diseases cluster "virtually" online via social media. This study aimed to (1) determine whether patients who have the rare diseases Fontan-associated protein losing enteropathy (PLE) and plastic bronchitis (PB) would participate in online research, and (2) explore response patterns to examine social media's role in participation compared with other referral modalities. A novel, internet-based survey querying details of potential pathogenesis, course, and treatment of PLE and PB was created. The study was available online via web and Facebook portals for 1 year. Apart from 2 study-initiated posts on patient-run Facebook pages at the study initiation, all recruitment was driven by study respondents only. Response patterns and referral sources were tracked. A total of 671 respondents with a Fontan palliation completed a valid survey, including 76 who had PLE and 46 who had PB. Responses over time demonstrated periodic, marked increases as new online populations of Fontan patients were reached. Of the responses, 574 (86%) were from the United States and 97 (14%) were international. The leading referral sources were Facebook, internet forums, and traditional websites. Overall, social media outlets referred 84% of all responses, making it the dominant modality for recruiting the largest reported contemporary cohort of Fontan patients and patients who have PLE and PB. The methodology and response patterns from this study can be used to design research applications for other rare diseases.

Echocardiographic evaluation of ventricular function in children with pulmonary hypertension.

Although described in adults, it remains unclear whether ventricular dysfunction exists in pediatric patients with pulmonary hypertension (PHN). The goal of this study was to identify differences in echocardiographic indices of ventricular function among pediatric PHN patients. From 2009 to 2011, pediatric PHN patients with normal intracardiac anatomy and age-matched controls (1:3 ratio) were enrolled in this retrospective case-control study. Diagnosis of PHN was based on tricuspid regurgitation velocity or septal position estimating right-ventricular (RV) pressure >50 % systemic. Measures of RV and left ventricular systolic and diastolic function, including tissue Doppler imaging (TDI) of the mitral annulus (MA) and tricuspid annulus (TA), were compared. Enrollees included 25 PHN patients and 75 age-matched controls (mean age 7.5 years [range 1 day to 19 years]). Parameters of RV systolic and diastolic function were worse in PHN patients. Compared with controls, PHN patients had significantly decreased tricuspid valve inflow ratio, decreased TA TDI early diastolic velocities, decreased systolic velocities, increased tricuspid E/E' ratio (all p < 0.01) and increased myocardial performance index. In an age-stratified analysis, TDI measures in PHN patients <1 year of age were similar to controls, whereas differences in TA TDI velocities and MA TDI velocities were noted in patients ≥1 year of age. Abnormalities in Doppler echocardiographic indices of ventricular systolic and diastolic function were identified in pediatric PHN patients and were more prominent with older age. These indices are promising for serial noninvasive monitoring of disease severity, but further correlation with catheterization-derived measures is needed.

Utility of a clinical practice guideline in treatment of chylothorax in the postoperative congenital heart patient.

BACKGROUND: Chylothorax after congenital heart surgery is a common complication with associated morbidities, but consensus treatment guidelines are lacking. Variability exists in the duration of medical treatment and timing for surgical intervention. METHODS: After institution of a clinical practice guideline for management of postoperative chylothorax at a single center, pediatric cardiothoracic intensive care unit (ICU) in June 2010, we retrospectively analyzed 2 cohorts of patients: those with chylothorax from January 2008 to May 2010 (early cohort; n=118) and from June 2010 to August 2011 (late cohort; n=45). Data collected included demographics, cardiac surgical procedure, treatments for chylothorax, bloodstream infections, hospital mortality, length of hospitalization, duration of mechanical ventilation, and device utilization. RESULTS: There were no demographic differences between the cohorts. No differences were found in octreotide use or surgical treatments for chylothorax. Significant differences were found in median times to chylothorax diagnosis (9 in early cohort versus 6 days in late cohort, p=0.004), ICU length of stay (18 vs 9 days, p=0.01), hospital length of stay (30 vs 23 days, p=0.005), and total durations of mechanical ventilation (11 vs 5 days, p=0.02), chest tube use (20 vs 14 days, p=0.01), central venous line use (27 vs 15 days, p=0.001), and NPO status (9.5 vs 6 days, p=0.04). CONCLUSIONS: Institution of a clinical practice guideline for treatment of chylothorax after congenital heart surgery was associated with earlier diagnosis, reduced hospital length of stay, mechanical ventilation, and device utilization for these patients.

Immunophenotyping and protein profiling of Fontan-associated plastic bronchitis airway casts.

RATIONALE: Plastic bronchitis (PB) is a rare and deadly condition that is characterized by the formation of airway casts. It most frequently occurs in children with underlying congenital heart disease that has been surgically palliated by the Fontan procedure. The Fontan circulation results in above-normal central venous pressure, and it has been hypothesized that the formation of airway casts is due to lymph leak. Knowledge of plastic bronchitis pathogenesis is poor and stems mostly from published case reports. OBJECTIVES: To garner information about cast pathogenesis by characterizing inflammatory cell phenotypes in existing formalin-preserved, paraffin-embedded samples and generating protein and cytokine-chemokine profiles of airway cast homogenates. METHODS: We used immunofluorescence confocal microscopy, state-of-the-science proteomics, and a cytokine array assay to immunophenotype cellular content and to generate protein and cytokine profiles of plastic bronchitis airway casts, respectively. MEASUREMENTS AND MAIN RESULTS: Neutrophils, eosinophils, macrophages, and B lymphocytes were identified in cast samples; there were notably fewer T lymphocytes. Fibrin(ogen) was an abundant protein in the cast proteome. Histone H4 was also abundant, and immunofluorescence microscopy demonstrated it to be mostly extracellular. The cytokine profile of plastic bronchitis casts was proinflammatory. CONCLUSIONS: Plastic bronchitis airway casts from children with Fontan physiology are composed of fibrin and are cellular and inflammatory in nature, providing evidence that their formation cannot be explained simply by lymph leak into the airways. Consequences of cellular necrosis including extracellular histones and the apparent low number of T cells indicate that a derangement in inflammation resolution likely contributes to cast formation.

Developmental impact and lesion maturation of histotripsy-mediated non-invasive tissue ablation in a fetal sheep model.

Non-invasive histotripsy therapy has previously been used to achieve precise fetal tissue ablation in a sheep model. To further assess the clinical viability of the technique, this study investigated potential effects of histotripsy therapy during the remaining gestation and its local impact on fetal development. Five ewes (six lambs) at 95-107 d of gestation were treated and allowed to complete the full gestation period of 150 d. A 1-MHz focused transducer was used to treat the fetal kidney and liver with 5-µs pulses at 500-Hz repetition rates and 10- to 16-MPa peak negative pressures; ultrasound imaging provided real-time treatment guidance. The lambs were euthanized after delivery and treated organs were harvested. Samples were examined by magnetic resonance imaging and histopathologic analysis. These data were compared with results from four other ewes (four lambs) that underwent similar treatments but were sacrificed immediately after the procedure. The sheep tolerated the treatment well, and acute lesion samples displayed well-defined ablated regions characterized by the presence of fractionated tissue and hemorrhage. All fetuses that were allowed to continue gestation survived and were delivered at full term. The lambs were healthy on delivery, with no signs of external injury. A minor indentation was observed in each of the treated kidneys with minimal presence of fibrous tissue, while no discernible signs of lesions were detected in treated livers. In a sheep model, histotripsy-mediated fetal tissue ablation caused no acute or pregnancy-related complications, supporting the potential safety and effectiveness of histotripsy therapy as a tool in fetal intervention procedures.