Hybrid versus Norwood procedure for hypoplastic left heart syndrome: contemporary series from a single center

Hybrid stage 1 palliation for HLHS: the experience of a tertiary center in a developing country

Background

Hypoplastic left heart syndrome (HLHS) accounts for 2.6% of congenital heart disease and is an invariably fatal cardiac anomaly if left untreated. Approximately 33,750 babies are born annually with HLHS in developing countries. Unfortunately, the majority will not survive due to the scarcity of resources and the limited availability of surgical management.

Aim

To describe and analyze our experience with the hybrid approach in the management of HLHS in a developing country.

Methods

We performed a retrospective single-center study involving all neonates born with HLHS over five years at the Children's Heart Center at the American University of Beirut. The medical records of patients who underwent the hybrid stage 1 palliation were reviewed, and data related to baseline characteristics, procedure details and outcomes were collected to describe the experience at a tertiary care center in a developing country.

Results

A total of 18 patients were diagnosed with HLHS over a five-year period at our institution, with male to female ratio of 1:1. Of those, eight patients underwent the hybrid stage I procedure. The mean weight at the time of the procedure was 3.3 ± 0.3 kg with an average age of 6.4 ± 4 days. The mean hospital length of stay was 27.25 days, with an interquartile range of 33 days. The cohort's follow-up duration averaged 5.9 ± 3.5 years. The surgical mortality was zero. Only one mortality was recorded during the interstage period between stage I and II and was attributed to sepsis. Notably, all surviving patients maintained preserved and satisfactory cardiac function with good clinical status.

Conclusion

Our limited experience underscores the potential of developing countries with proper foundations to adopt the hybrid procedure for HLHS, yielding outcomes on par with those observed in developed countries. This demonstrates the viability of establishing a more balanced global landscape for children with congenital heart disease.

Applying the Hybrid Concept as a Bridge to Transplantation in Infants Without Hypoplastic Left Heart Syndrome

Therapies to support small infants in decompensated heart failure that are failing medical management are limited. We have used the hybrid approach, classically reserved for high-risk infants with single ventricle physiology, in patients with biventricular physiology with left ventricular failure. This approach secures systemic circulation, relieves left atrial hypertension, protects the pulmonary vasculature, and allows the right ventricle to support cardiac output. This approach can be used as a bridge to transplantation in select individuals. Infants without single ventricle congenital heart disease who were treated with the hybrid approach between 2008 and 2021 were included in analysis. Eight patients were identified. At the time of hybrid procedure, the median weight was 3.2 kg (range 2.4-3.6 kg) and the median age was 18 days (range 1-153 days). Seventy five percent were mechanically ventilated and 88% were on inotropic support. The median duration from hybrid procedure to transplant was 63 days (range 4-116 days). All patients experienced a good outcome (delisted for improvement or transplanted). The hybrid procedure is an appropriate therapeutic bridge to transplantation in a carefully selected subset of critically ill infants without single ventricle congenital heart disease in whom alternate therapies may confer increased risk for morbidity and mortality.

From Surgical to Total Transcatheter Stage I Palliation: Exploring Evidence and Perspectives

Neonates with single ventricle physiology and ductal-dependent systemic circulation, such as those with hypoplastic left heart syndrome, undergo palliation in the first days of life. Over the past decades, variations on the traditional Stage 1 palliation, also known as Norwood operation, have emerged. These include the hybrid palliation and the total transcatheter approach. Here, we review the current evidence and data on different Stage 1 approaches, with a focus on their advantages, challenges, and future perspectives. Overall, although controversy remains regarding the superiority or inferiority of one approach to another, outcomes after the Norwood and the hybrid palliation have improved over time. However, both procedures still represent high-risk approaches that entail exposure to sternotomy, surgery, and potential cardiopulmonary bypass. The total transcatheter Stage 1 palliation spares patients the surgical and cardiopulmonary bypass insults and has proven to be an effective strategy to bridge even high-risk infants to a later palliative surgery, complete repair, or transplant. As the most recently proposed approach, data are still limited but promising. Future studies will be needed to better define the advantages, challenges, outcomes, and overall potential of this novel approach.

Hybrid palliation versus nonhybrid management for a multi-institutional cohort of infants with critical left heart obstruction

OBJECTIVE

To compare patient characteristics and overall survival for infants with critical left heart obstruction after hybrid palliation (bilateral pulmonary artery banding with or without ductal stenting) versus nonhybrid management (eg, Norwood, primary transplantation, biventricular repair, or transcatheter/surgical aortic valvotomy).

METHODS

From 2005 to 2019, 1045 infants in the Congenital Heart Surgeons' Society critical left heart obstruction cohort underwent interventions across 28 institutions. Using a balancing score propensity analysis, 214 infants who underwent hybrid palliation and 831 infants who underwent nonhybrid management were proportionately matched regarding variables significantly associated with mortality and variables noted to significantly differ between groups. Overall survival between the 2 groups was adjusted by applying balancing scores to nonparametric estimates.

RESULTS

Compared with the nonhybrid management group, infants who underwent hybrid palliation had lower birth weight, smaller gestational age, and higher prevalence of in-utero interventions, noncardiac comorbidities, preoperative mechanical ventilation, absent interatrial communication, and moderate or severe mitral valve stenosis (all P values < .03). Unadjusted 12-year survival after hybrid palliation and nonhybrid management, was 55% versus 69%, respectively. After matching, 12-year survival after hybrid palliation versus nonhybrid management was 58% versus 63%, respectively (P = .37). Among matched infants born weighing <2.5 kg, 2-year survival after hybrid palliation versus nonhybrid management was 37% versus 51%, respectively (P = .22).

CONCLUSIONS

Infants born with critical left heart obstruction who undergo hybrid palliation have more high-risk characteristics and anatomy versus infants who undergo nonhybrid management. Nonetheless, after adjustment, there was no significant difference in 12-year survival after hybrid palliation versus nonhybrid management. Mortality remains high, and hybrid palliation confers no survival advantage, even for lower-birth-weight infants.

Norwood operation versus comprehensive stage II after bilateral pulmonary artery banding palliation for infants with critical left heart obstruction

OBJECTIVE

To determine patient characteristics and outcomes after Norwood versus comprehensive stage II (COMPSII) for infants with critical left heart obstruction who had prior hybrid palliation (bilateral pulmonary artery banding ± ductal stent).

METHODS

From 23 Congenital Heart Surgeons' Society institutions (2005-2020), 138 infants underwent hybrid palliation followed by either Norwood (n = 73, 53%) or COMPSII (n = 65). Baseline characteristics were compared between Norwood and COMPSII groups. Parametric hazard model with competing risk methodology was used to determine risk and factors associated with outcomes of Fontan, transplantation, or death.

RESULTS

Infants who underwent Norwood versus COMPSII had a higher prevalence of prematurity (26% vs 14%, P = .08), lower birth weight (median 2.8 vs 3.2 kg, P < .01) and less frequent ductal stenting (37% vs 99%; P < .01). Norwood was performed at a median age of 44 days and median weight of 3.5 kg, versus COMPSII at 162 days and 6.0 kg (both P < .01). Median follow-up was 6.5 years. At 5 years after Norwood and COMPSII, respectively; 50% versus 68% had Fontan (P = .16), 3% versus 5% had transplantation (P = .70), 40% versus 15% died (P = .10), and 7% versus 11% are alive without transition, respectively. For factors associated with either mortality or Fontan, only preoperative mechanical ventilation occurred more frequently in the Norwood group.

CONCLUSIONS

Higher prevalence of prematurity, lower birth weight, and other patient-related characteristics in the Norwood versus COMPSII groups may influence differences in outcomes that were not statistically significant for this limited risk-adjusted cohort. The clinical decision regarding Norwood versus COMPSII after initial hybrid palliation remains challenging.

Increasing Use of the Right Ventricle to Pulmonary Artery Shunt for Stage 1 Palliation

BACKGROUND

Stage 1 palliation of hypoplastic left heart syndrome entails use of the Norwood operation with either a modified Blalock-Taussig shunt or a right ventricle-to-pulmonary artery shunt, or the Hybrid procedure. Utilization trends and factors influencing palliation selection remain unclear. We aimed to evaluate these questions and to compare outcomes between types of stage 1 palliation.

METHODS

The National Pediatric Cardiology Quality Improvement Collaborative phase 1 (6/2008-8/2016) and phase 2 (8/2016-9/2019) databases were used. Procedure type was assessed by operation year. Baseline characteristics and annual hospital volume were evaluated. Post-surgical admission duration and outcomes were compared.

RESULTS

3,497 patients were included, 30.8% with modified Blalock-Taussig shunt, 59.7% with right-ventricle-to-pulmonary-artery shunt, and 9.5% with Hybrid. Use of the right-ventricle-to-pulmonary-artery shunt increased over time (p=0.02). This increase was similar among all hospital volumes. Higher hospital volume (OR 1.2 [95% CI 1.1-1.4], p=0.003), male sex (OR 1.3 [95% CI 1.1-1.6], p=0.01), and isolated cardiac disease (OR 1.33 [95% CI 1.01-1.55], p=0.05) were associated with relatively higher likelihoods of a modified Blalock-Taussig shunt. Mortality/transplant rates before stage 2 palliation were higher with the modified Blalock-Taussig shunt than the right-ventricle-to-pulmonary-artery shunt (12.3% vs 9.6%, p=0.03).

CONCLUSIONS

In stage one palliation, use of right-ventricle-to-pulmonary-artery shunts has increased over time, use of modified Blalock-Taussig shunts has decreased, and use of Hybrids was unchanged. The modified Blalock-Taussig shunt has a higher likelihood of use in higher volume centers, males, and less complex patients, but is associated with longer hospitalizations and lower transplant-free survival to stage 2 palliation.

New Aspects in the Diagnosis and Therapy of Fetal Hypoplastic Left Heart Syndrome

Fetal hypoplastic left heart syndrome (HLHS) is a severe congenital heart disease with a lethal prognosis without postnatal therapeutic intervention or surgery. The aim of this article is to give a brief overview of new findings in the field of prenatal diagnosis and the therapy of HLHS. As cardiac output in HLHS children depends on the right ventricle (RV), prenatal assessment of fetal RV function is of interest to predict poor functional RV status before the RV becomes the systemic ventricle. Prenatal cardiac interventions such as fetal aortic valvuloplasty and non-invasive procedures such as maternal hyperoxygenation seem to be promising treatment options but will need to be evaluated with regard to long-term outcomes. Novel approaches such as stem cell therapy or neuroprotection provide important clues about the complexity of the disease. New aspects in diagnostics and therapy of HLHS show the potential of a targeted prenatal treatment planning. This could be used to optimize parental counseling as well as pre- and postnatal management of affected children.

Early Outcomes of Hypoplastic Left Heart Syndrome Infants: Meta-Analysis of Studies Comparing the Hybrid and Norwood Procedures

The hybrid strategy is an alternative to the traditional Norwood procedure for initial palliation of infants with hypoplastic left heart syndrome (HLHS) who are deemed to be at high surgical risk. Numerous single-center studies have compared the two procedures, showing similar early outcomes, although the cohort sizes are likely insufficiently powered to detect significant differences. The current meta-analysis aims to explore the early morbidity and mortality associated with the hybrid compared to the Norwood procedure. MEDLINE, Cochrane Libraries, and Embase were systematically searched, and 14 studies were included for statistical synthesis, comprising 263 hybrid and 426 Norwood patients. Early mortality was significantly higher in the hybrid patients (relative risk [RR] = 1.54, P < .05, 95% confidence interval [CI]: 1.02-2.34), whereas interstage mortality was comparable between the two groups (RR = 0.88, P > .05, 95% CI: 0.46-1.70). Six-month (RR = 0.89, P < .05, 95% CI: 0.80-1.00) and one-year (RR = 0.88, P < .05, 95% CI: 0.78-1.00) transplant-free survival was also inferior among the hybrid patients. Furthermore, the hybrid patients required more reinterventions following initial surgical palliation (RR = 1.48, P < .05, 95% CI: 1.09-2.01), although the two groups had comparable length of hospital and intensive care unit stay postoperatively. In conclusion, our results suggest that the hybrid procedure is associated with worse early survival compared to the traditional Norwood when used for initial palliation of infants with HLHS. However, due to the hybrid being used preferentially for high-risk patients, definitive conclusions regarding the efficacy of the procedure cannot be drawn.

The Evolution of Therapeutic Strategies: Niche Apportionment for Hybrid Palliation

Hybrid palliation, the concept to stabilize univentricular circulation with bilateral pulmonary artery banding and maintenance of ductal patency, has significantly widened the therapeutic spectrum for patients with single-ventricle malformations or borderline hypoplasia. The concept has already been a part of early attempts to improve outcome in hypoplastic left heart syndrome but has not attracted much attention initially. Technical refinement and expertise have led to results that ultimately allowed the palliative strategy to gain traction and to be selectively adopted. By now, we have gained almost 2 decades of experience, and as much as hybrid palliation has changed our approach to single-ventricle management, new strategies and indications have been formed by this experience. We therefore review concepts and patterns of use of hybrid palliation as well as benefits and challenges of the respective pathways to highlight the current status of the hybrid procedure.

Hybrid Strategy for Neonates With Ductal-Dependent Systemic Circulation at High Risk for Norwood

BACKGROUND

Hypoplastic left heart syndrome and other cardiac lesions with ductal-dependent systemic circulation continue to be challenging to manage, especially in high-risk (HR) populations (those with prematurity, multiple congenital anomalies, moderate to severe tricuspid regurgitation, hemodynamic instability, intact atrial septum).

METHODS

A retrospective study on our institution's experience implementing a hybrid strategy as initial palliation in HR patients with ductal-dependent systemic circulation in HR patients undergoing Norwood versus hybrid procedure. From July 2004 to May 2008, 16 HR patients underwent stage I Norwood procedure. After implementation of a hybrid strategy in 2008, 24 HR patients underwent hybrid procedure from May 2008 to November 2015.

RESULTS

There was no difference in gestational age, age at procedure, or hospital length of stay. The HR Hybrid group had lower mean weight (2.6 kg vs 3.1 kg, p = 0.026). Thirty-day mortality was lower in the HR Hybrid group (4% vs 31%, p = 0.019), although there was no difference in interstage mortality (17% vs 9%, p = 0.396). Catheter-based reintervention was more prevalent in the HR Hybrid group, but did not have a negative impact on survival. One-year transplant-free survival was similar (p = 0.416). HR Hybrid patients weighing less than 2.6 kg had higher overall survival (83% vs 25%, p = 0.013), as did patients who were premature (70% vs 0%, p = 0.003).

CONCLUSIONS

In high-risk patients, the hybrid procedure appears to have lower 30-day mortality and may have a survival benefit in premature patients and those less than 2.6 kg. Long-term attrition in this high-risk population is ongoing regardless of early strategy.

Ventricular function and vascular dimensions after Norwood and hybrid palliation of hypoplastic left heart syndrome

Objective

Norwood and hybrid procedure are two options available for initial palliation of patients with hypoplastic left heart syndrome (HLHS). Our study aimed to assess potential differences in right ventricular (RV) function and pulmonary artery dimensions using cardiac magnetic resonance (CMR) in survivors with HLHS.

Methods

42 Norwood (mean age 2.4±0.8) and 44 hybrid (mean age 2.0±1.0 years) patients were evaluated by CMR after stage II palliation prior to planned Fontan completion. Initial stage I Norwood procedure was performed using a modified Blalock-Taussig shunt, while the hybrid procedure consisted of bilateral pulmonary artery banding and arterial duct stenting. Need for reinterventions and subsequent outcomes were also assessed.

Results

Norwood patients had larger RV end-diastolic dimensions (91±23 vs 80±31 mL/m2, p=0.004) and lower heart rate (90±15 vs 102±13, p<0.001) than hybrid patients. Both Norwood and hybrid patients showed preserved global RV pump function (59±9 vs 59%±10%, p=0.91), while RV strain, strain rate and intraventricular synchrony were superior in the Norwood group. Pulmonary artery size was reduced (lower lobe index 135±74 vs 161±62 mm2/m2, p=0.02), and reintervention rate was significantly higher in the hybrid group whereas subsequent outcome did not differ significantly (p=0.24).

Conclusions

Norwood and hybrid strategy were associated with equivalent and preserved global RV pump function while development of the pulmonary arteries and reintervention rate were superior using the Norwood approach. Impaired RV myocardial deformation as a potential marker of early RV dysfunction in the hybrid group may have a negative long-term impact in this population.

Mathematical Analysis and Physical Profile of Blalock-Taussig Shunt and Sano Modification Procedure in Hypoplastic Left Heart Syndrome: Review of the Literature and Implications for the Anesthesiologist

The first stage of surgical treatment for hypoplastic left heart syndrome (HLHS) includes the creation of artificial systemic-to-pulmonary connections to provide pulmonary blood flow. The modified Blalock-Taussig (mBT) shunt has been the technique of choice for this procedure; however, a right ventricle-pulmonary artery (RV-PA) shunt has been introduced into clinical practice with encouraging but still conflicting outcomes when compared with the mBT shunt. The aim of this study is to explore mathematical modeling as a tool for describing physical profiles that could assist the surgical team in predicting complications related to stenosis and malfunction of grafts in an attempt to find correlations with clinical outcomes from clinical studies that compared both surgical techniques and to assist the anesthesiologist in making decisions to manage patients with this complex cardiac anatomy. Mathematical modeling to display the physical characteristics of the chosen surgical shunt is a valuable tool to predict flow patterns, shear stress, and rate distribution as well as energetic performance at the graft level and relative to ventricular efficiency. Such predictions will enable the surgical team to refine the technique so that hemodynamic complications be anticipated and prevented, and are also important for perioperative management by the anesthesia team.

Interstage somatic growth in children with hypoplastic left heart syndrome after initial palliation with the hybrid procedure

Introduction The hybrid procedure is one mode of initial palliation for hypoplastic left heart syndrome. Subsequently, patients proceed with either the "three-stage" pathway - comprehensive second stage followed by Fontan completion - or the "four-stage" pathway - Norwood procedure, hemi-Fontan, or Fontan completion. In this study, we describe somatic growth patterns observed in the hybrid groups and a comparison primary Norwood group.

METHODS

A retrospective analysis of patients who have undergone hybrid procedure and Fontan completion was performed. Weight-for-age and height-for-age z-scores were recorded at each operation.

RESULTS

We identified 13 hybrid patients - eight in the three-stage pathway and five in the four-stage pathway - and 49 Norwood patients. Weight: three stage: weight decreased from hybrid procedure to comprehensive second stage (-0.4±1.3 versus -2.3±1.4, p<0.01) and then increased to Fontan completion (-0.4±1.5 versus -0.6±1.4, p<0.01); four stage: weight decreased from hybrid procedure to Norwood (-2.0±1.4 versus -3.3±0.9, p=0.06), then stabilised to hemi-Fontan. Weight increased from hemi-Fontan to Fontan completion (-2.7±0.6 versus -1.0±0.7, p=0.01); primary Norwood group: weight decreased from Norwood to hemi-Fontan (p<0.001) and then increased to Fontan completion (p<0.001). Height: height declined from hybrid procedure to Fontan completion in the three-stage group. In the four-stage group, height decreased from hybrid to hemi-Fontan, and then increased to Fontan completion. The Norwood group decreased in height from Norwood to hemi-Fontan, followed by an increase to Fontan completion.

CONCLUSION

In this study, we show that patients undergoing the hybrid procedure have poor weight gain before superior cavopulmonary connection, before returning to baseline by Fontan completion. This study identifies key periods to target poor somatic growth, a risk factor of morbidity and worse neurodevelopmental outcomes.

Is a hybrid strategy a lower-risk alternative to stage 1 Norwood operation?

BACKGROUND

For neonates with critical left ventricular outflow tract obstruction (LVOTO), hybrid procedures are an alternative to the Norwood stage 1 procedure. Despite perceived advantages, however, outcomes are not well defined. Therefore, we compared outcomes after stage 1 hybrid and Norwood procedures.

METHODS

In a critical LVOTO inception cohort (2005-2014; 20 institutions), a total of 564 neonates underwent stage 1 palliation with the Norwood operation with a modified Blalock-Taussig shunt (NW-BT; n = 232; 41%), Norwood operation with a right ventricle-to-pulmonary artery conduit (NW-RVPA; n = 222; 39%), or a hybrid procedure (n = 110; 20%). Post-stage 1 outcomes were analyzed via competing-risks and parametric hazard analyses and compared among all 564 patients and between patients who underwent propensity-matched hybrid and those who underwent NW-BT/NW-RVPA.

RESULTS

By 6 years after the stage 1 operation, 50% ± 3%, 7% ± 2%, and 4% ± 1% of patients transitioned to Fontan, transplantation, and biventricular repair, respectively, whereas 7% ± 2% were alive without transition and 32% ± 2% died. Risk factors for death without transition included procedure type, smaller ascending aorta, aortic valve atresia, and lower birth weight. Risk-adjusted 4-year survival was better after NW-RVPA than after NW-BT or hybrid (76% vs 60% vs 61%; P < .001). Furthermore, for neonates with lower birth weight (<∼2 kg), an interaction between birth weight and hybrid resulted in a trend toward better survival after hybrid compared with NW-BT or NW-RVPA. For propensity-matched neonates between hybrid and NW-BT (88 pairs), 4-year survival was similar (62% vs 57%; P = .58). For propensity-matched neonates between hybrid and NW-RVPA (81 pairs), 4-year survival was better after NW-RVPA (59% vs 75%; P = .008).

CONCLUSIONS

For neonates with critical LVOTO undergoing single-ventricle palliation, NW-RVPA was associated with the best overall survival. Hybrid strategies are not a lower-risk alternative to Norwood operations overall; however, the impact of lower birth weight on survival may be mitigated after hybrid procedures compared with Norwood operations.

Hybrid Palliation for Ductal-Dependent Systemic Circulation

We reviewed our hybrid palliation experience for 91 neonates, with ductal-dependent systemic circulation, born between August 2007 and October 2015. For analysis, we stratified the 91 patients by a risk factor (RF) score and divided them into three groups: (1) high-risk two-functional ventricles (2V) median RF score of 3 (N = 20); (2) low-risk one-functional ventricle (1V) RF score 0-1 (N = 32); and (3) high-risk 1V RF score ≥2 (N = 39). Midterm survival (median 4 years) by group was: (1) 95 %, (2) 91 %, and (3) 15 %, (p = 0.001). In conclusion, hybrid palliation was associated with excellent midterm results for high-risk 2V and low-risk 1V patients with ductal-dependent systemic circulation. In contrast, high-risk 1V patients had significantly worse outcomes.

"Functionally" univentricular hearts: impact of pre-natal diagnosis

Within the last few decades the pre-natal echocardiographic diagnosis of congenital heart defects has made substantial progresses, particularly for the identification of complex malformation. "Functionally" univentricular hearts categorize a huge variety of heart malformations. Since no one of the patients with these congenital heart defects can ever undergo a bi-ventricular type of repair, early recognition and decision-making from the neonatal period are required in order to allow for appropriate multiple-step diagnostic and treatment procedures, either of interventional cardiology and/or surgery, on the pathway of "univentricular" heart. In the literature strong disagreements exist about the potential impact of the pre-natal diagnosis on the early and late outcomes of complex congenital heart defects. This review of the recent reports has been undertaken to better understand the impact of pre-natal diagnosis in "functionally" univentricular hearts taking into consideration the following topics: pre-natal screening, outcomes and survival, general morbidity, neurologic and developmental consequences, pregnancy management and delivery planning, resources utilization and costs/benefits issues, ethical implications, parents counseling, and interruption of pregnancy versus treatment.

Hypoplastic left heart syndrome - unresolved issues

Hypoplastic left heart syndrome (HLHS) is one of the most challenging congenital heart defects. At present, it is expected that - at best - 70% of newborns with HLHS will reach adulthood. This review addresses the problems of right ventricular (RV) failure and insufficient growth of pulmonary vasculature in these patients. In order to further improve long-term prognosis translational research to control RV function, growth of pulmonary arteries and progress in chronic circulatory support are clearly needed to provide a further improvement for adults with HLHS.