Right ventricle to pulmonary artery conduit improves outcome after stage I Norwood for hypoplastic left heart syndrome

Surgical Modulation of Pulmonary Artery Shear Stress: A Patient-Specific CFD Analysis of the Norwood Procedure

PURPOSR

This study created 3D CFD models of the Norwood procedure for hypoplastic left heart syndrome (HLHS) using standard angiography and echocardiogram data to investigate the impact of shunt characteristics on pulmonary artery (PA) hemodynamics. Leveraging routine clinical data offers advantages such as availability and cost-effectiveness without subjecting patients to additional invasive procedures.

METHODS

Patient-specific geometries of the intrathoracic arteries of two Norwood patients were generated from biplane cineangiograms. "Virtual surgery" was then performed to simulate the hemodynamics of alternative PA shunt configurations, including shunt type (modified Blalock-Thomas-Taussig shunt (mBTTS) vs. right ventricle-to-pulmonary artery shunt (RVPAS)), shunt diameter, and pulmonary artery anastomosis angle. Left-right pulmonary flow differential, Qp/Qs, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) were evaluated.

RESULTS

There was strong agreement between clinically measured data and CFD model output throughout the patient-specific models. Geometries with a RVPAS tended toward more balanced left-right pulmonary flow, lower Qp/Qs, and greater TAWSS and OSI than models with a mBTTS. For both shunt types, larger shunts resulted in a higher Qp/Qs and higher TAWSS, with minimal effect on OSI. Low TAWSS areas correlated with regions of low flow and changing the PA-shunt anastomosis angle to face toward low TAWSS regions increased TAWSS.

CONCLUSION

Excellent correlation between clinically measured and CFD model data shows that 3D CFD models of HLHS Norwood can be developed using standard angiography and echocardiographic data. The CFD analysis also revealed consistent changes in PA TAWSS, flow differential, and OSI as a function of shunt characteristics.

Clinical Characteristics and Potential Pathogenesis of Cardiac Necrotizing Enterocolitis in Neonates with Congenital Heart Disease: A Narrative Review

Neonates with congenital heart disease (CHD) are at an increased risk of developing necrotizing enterocolitis (NEC), an acute inflammatory intestinal injury most commonly associated with preterm infants. The rarity of this complex disease, termed cardiac NEC, has resulted in a dearth of information on its pathophysiology. However, a higher incidence in term infants, effects on more distal regions of the intestine, and potentially a differential immune response may distinguish cardiac NEC as a distinct condition from the more common preterm, classical NEC. In this review, risk factors, differentiated from those of classical NEC, are discussed according to their potential contribution to the disease process, and a general pathogenesis is postulated for cardiac NEC. Additionally, biomarkers specific to cardiac NEC, clinical outcomes, and strategies for achieving enteral feeds are discussed. Working towards an understanding of the mechanisms underlying cardiac NEC may aid in future diagnosis of the condition and provide potential therapeutic targets.

Impact of Left Ventricular Morphology on Adverse Outcomes Following Stage 1 Palliation for Hypoplastic Left Heart Syndrome: 20 Years of National Data From Sweden

Background

Hypoplastic left heart syndrome is associated with significant morbidity and mortality. We aimed to assess the influence of left ventricular morphology and choice of shunt on adverse outcome in patients with hypoplastic left heart syndrome and stage 1 palliation.

Methods and Results

This was a retrospective analysis of patients with hypoplastic left heart syndrome with stage 1 palliation between 1999 and 2018 in Sweden. Patients (n=167) were grouped based on the anatomic subtypes aortic‐mitral atresia, aortic atresia‐mitral stenosis (AA‐MS), and aortic‐mitral stenosis. The left ventricular phenotypes including globular left ventricle (Glob‐LV), miniaturized and slit‐like left ventricle (LV), and the incidence of major adverse events (MAEs) including mortality were assessed. The overall mortality and MAEs were 31% and 41%, respectively. AA‐MS (35%) was associated with both mortality (all other subtypes versus AA‐MS: interstage‐I: hazard ratio [HR], 2.7; P =0.006; overall: HR, 2.2; P =0.005) and MAEs (HR, 2.4; P =0.0009). Glob‐LV (57%), noticed in all patients with AA‐MS, 61% of patients with aortic stenosis‐mitral stenosis, and 19% of patients with aortic atresia‐mitral atresia, was associated with both mortality (all other left ventricular phenotypes versus Glob‐LV: interstage‐I: HR, 4.5; P =0.004; overall: HR, 3.4; P =0.0007) and MAEs (HR, 2.7; P =0.0007). There was no difference in mortality and MAEs between patients with AA‐MS and without AA‐MS with Glob‐LV ( P >0.15). Patients with AA‐MS (35%) or Glob‐LV (38%) palliated with a Blalock‐Taussig shunt had higher overall mortality compared with those palliated with Sano shunts, irrespective of the stage 1 palliation year (AA‐MS: HR, 2.6; P =0.04; Glob‐ LV: HR, 2.1; P =0.03).

Conclusions

Glob‐LV and AA‐MS are independent morphological risk factors for adverse short‐ and long‐ term outcome, especially if a Blalock‐Taussig shunt is used as part of stage 1 palliation. These findings are important for the clinical management of patients with hypoplastic left heart syndrome.

Comparison of shunt types in the neonatal Norwood procedure for single ventricle

OBJECTIVES

The ideal shunt for pulmonary blood flow, modified Blalock-Taussig shunt (MBTS) or right ventricular-pulmonary artery conduit (RVPAC) is yet to be determined. This study aimed to evaluate outcomes after the Norwood procedure according to the type of shunt.

METHODS

A total of 322 neonates with hypoplastic left heart syndrome and related anomalies who underwent the Norwood procedure at our institution between 2001 and 2019 were divided into MBTS and RVPAC groups and the outcomes after the Norwood procedure were compared between the groups with respect to mortality after each staged procedure.

RESULTS

We identified 322 consequent patients who underwent neonatal Norwood procedure for hypoplastic left heart syndrome (271 patients, 84.2%) and its variant (51 patients, 15.8%). RVPAC was performed in 163 (50.6%) patients and MBTS was performed in 159 (49.4%). There were no differences in the rate of early death (11.0% vs 12.6%, P = 0.69) or late death (7.4% vs 6.9%, P = 0.87) between the 2 groups after the Norwood procedure, and no significant difference in the number of patients who reached bidirectional cavopulmonary shunt (77.9% vs 76.1%, P = 0.69), and there was no difference in mortality after bidirectional cavopulmonary shunt (12.3% vs 7.5%, P = 0.15) or Fontan completion rate (54.0% vs 52.2%, P = 0.42) between the 2 groups. Survival at 0.5, 1, 3 and 6 years after the Norwood procedure was 81.0%, 73.8%, 67.9% and 67.0% in patients with RVPAC and 77.1%, 73.3%, 69.1% and 67.9% in patients with MBTS. There was no significant difference in the survival between the 2 groups during the median follow-up of 2.6 (interquartile ranges: 0.3-8.4, maximal 18.8) years (P = 0.97).

CONCLUSIONS

In neonates undergoing the Norwood procedure, our available data of maximal 18.8 years follow-up showed no significant difference in early mortality, inter-stage attritions, or overall survival, between MBTS and RVPAC.

Periscopic technique in Norwood operation is associated with better preservation of early ventricular function

Objective

Although the right ventricle (RV) to pulmonary artery conduit in stage 1 Norwood operation results in improved interstage survival, the long-term effects of the ventriculotomy used in the traditional technique remain a concern. The periscopic technique (PT) of RV to pulmonary artery conduit placement has been described as an alternative technique to minimize RV injury. A retrospective study was performed to compare the effects of traditional technique and PT on ventricular function following Norwood operation.

Methods

A retrospective study of all patients who underwent Norwood operation from 2012 to 2019 was performed. Patients with baseline RV dysfunction and significant tricuspid valve regurgitation were excluded. Prestage 2 echocardiograms were reviewed by a blinded experienced imager for quantification of RV function (sinus and infundibular RV fractional area change) as well as for regional conduit site wall dysfunction (normal or abnormal, including hypokinesia, akinesia, or dyskinesia). Wilcoxon rank-sum tests were used to assess differences in RV infundibular and RV sinus ejection fraction and the Fisher exact test was used to assess differences in regional wall dysfunction.

Results

Twenty-two patients met inclusion criteria. Eight underwent traditional technique and 14 underwent PT. Median infundibular RV fractional area change was 49% and 37% (P = .02) and sinus RV fractional area change was 50% and 41% for PT and traditional technique (P = .007) respectively. Similarly qualitative regional RV wall function was better preserved in PT (P = .002).

Conclusions

The PT for RV to pulmonary artery conduit in Norwood operation results in better preservation of early RV global and regional systolic function. Whether or not this benefit translates to improved clinical outcome still needs to be studied.

Characterization of Post-Operative Hemodynamics Following the Norwood Procedure Using Population Data and Multi-Scale Modeling

Children with hypoplastic left heart syndrome (HLHS) must undergo multiple surgical stages to reconstruct the anatomy to a sustainable single ventricle system. Stage I palliation, or the Norwood procedure, provides circulation to both pulmonary and systemic vasculature. The aorta is reconstructed and attached to the right ventricle and a fraction of systemic flow is redirected to the pulmonary arteries (PAs) through a systemic-to-PA shunt. Despite abundant hemodynamic data available 4-5 months after Norwood palliation, data is very scarce immediately following stage I. This data is critical in determining post-operative success. In this work, we combined population data and computational fluid dynamics (CFD) to characterize hemodynamics immediately following stage I (post-stage I) and prior to stage II palliation (pre-stage II). A patient-specific model was constructed as a baseline geometry, which was then scaled to reflect population-based morphological data at both time-points. Population-based hemodynamic data was then used to calibrate each model to reproduce blood flow representative of HLHS patients. The post-stage I simulation produced a PA pressure of 22 mmHg and high-frequency oscillations within the flow field indicating highly disturbed hemodynamics. Despite PA mean pressure dropping to 14 mmHg, the pre-stage II model also produced high-frequency flow components and PA wall shear stress increases. These suboptimal conditions may be necessary to ensure adequate PA flow throughout the pre-stage II period, as the shunt becomes relatively smaller compared to the patient's somatic growth. In the future, CFD can be used to optimize shunt design and minimize these suboptimal conditions.

Geometry of the pulmonary arteries before the Fontan operation: can we influence it during the Norwood procedure?

OBJECTIVES

The right ventricle-to-pulmonary artery (RV-PA) shunt provides stable haemodynamics after the Norwood procedure but can influence development of the central pulmonary arteries (PAs). The goal of this study was to analyse the geometry of the central PAs in children with hypoplastic left heart syndrome before the Fontan operation with respect to the RV-PA shunt site and the type of the second-stage operation.

METHODS

A total of 161 children with hypoplastic left heart syndrome, median age 2.7 (range 1.3-9.8) years and median weight 12.7 (range 7.6-26.1) kg, underwent the Fontan operation after having had the Norwood procedure with an RV-PA shunt. The patients were divided into 2 groups: left-sided RV-PA (L-RV-PA) (n = 129) with the shunt on the left and right-sided RV-PA (n = 32) with the shunt on the right side of the neoaorta. Angiographic data obtained before the Fontan and all cardiac catheterization interventions were analysed retrospectively.

RESULTS

Between the second and third stages, as well as directly before the Fontan operation, the L-RV-PA group required more PA catheter interventions (P = 0.001 and P = 0.03). In this group, the minimal left PA diameter was smaller than that in the R-RV-PA group (P = 0.021). Leaving the shunt open until the Fontan operation increased the rate of PA interventions in the L-RV-PA group (P = 0.001), but there is no evidence of the impact on the development of the left PAs (P = 0.075). There is also no evidence that the type of the second-stage procedure influences the intervention rate before the Fontan procedure (P = 0.14).

CONCLUSIONS

Children who have the L-RV-PA shunt require more PA catheter interventions. The right-sided RV-PA shunt and the subsequent Glenn anastomosis in the place of the shunt are associated with distortion-free and more symmetrical development of the central PAs.

Outcomes of hybrid and Norwood Stage I procedures for the treatment of hypoplastic left heart syndrome and its variants

Background

In this study, we present the outcomes of hybrid and Norwood Stage I procedures for the treatment of hypoplastic left heart syndrome and its variants.

Methods

In this study, a total of 97 pediatric patients who were operated due to hypoplastic left heart syndrome and its variants between March 2011 and October 2018 were retrospectively analyzed. Thirty-two of the patients (28 males, 4 females; median age 5 days; range, 1 to 25 days) underwent Norwood Stage I operation (Group N), while the remaining 65 patients (44 males, 21 females; median age 6 days; range, 1 to 55 days) underwent a hybrid procedure (Group H). Both treatment strategies were compared.

Results

The median body weight in Group H was significantly lower and the number of patients with a low birth weight (<2,500 g) was significantly higher than Group N (p=0.002 and 0.004, respectively). The postoperative early mortality rate was similar between the groups. Univariate and multivariate analyses revealed that the need for preoperative mechanical ventilation was a significant factor for mortality (p=0.004 and 0.003, respectively). Syndromic appearance was also a significant factor the multivariate analysis (p=0.03). There was a statistically significant difference between the groups in terms of the inter-stage mortality rates (p=0.0045). Second-stage procedure was performed in 32 patients. The early mortality rate after the Glenn operation was 7.6%. Six patients died after comprehensive Stage II operation. Five patients underwent biventricular repair and 8 patients had third-stage fenestrated extracardiac Fontan operation (Group N, n=7 and Group H, n=1). The Kaplan-Meier survival curve demonstrated that Group N had a higher survival rate at both one and five years than Group H, although the difference was not statistically significant (p=0.15). Subgroup analysis showed that the Norwood procedure with Sano modification had the highest survival rate with 40% at five years.

Conclusion

Our study results show that patients undergoing the Norwood procedure have a more uneventful course of inter-stage period and Stage II and III, despite drawbacks early after Stage I procedure. Based on our experiences, we recommend performing the hybrid intervention in patients with a poor clinical condition and a body weight of <2,500 g.

Hypoplastic left heart syndrome [HLHS]: treatment options in present era

Hypoplastic left heart syndrome (HLHS) is the most severe form of congenital heart defect (CHD). The first successful intervention for it was undertaken by Norwood in 1983. Since then, there have been much development in the pre, intra, and postoperative treatment option in staged palliative surgical procedures. Early diagnostic management, prenatal interventions, innovative diagnostic methods, constantly modified surgical techniques, and hybridization contribute to a significant progress in treatment options. This will allow for defining an optimal strategy of improving survival and quality of life in HLHS patients. The development of intervention cardiology makes possible the stepwise treatment of the defect with one operation only. The first and third stage may be done by hybrid or interventional methods, then only the second stage of treatment needs to be done surgically. The world experience and all the available literature says that the 1st-stage procedure could be done now safely either directly or with a bridge to Norwood followed by the stage 2 with a Glen or Hemi-Fontan and followed by a Fontan down the lane surgically.

Hypoplastic left heart syndrome: from fetus to fontan

The care of children with hypoplastic left heart syndrome is constantly evolving. Prenatal diagnosis of hypoplastic left heart syndrome will aid in counselling of parents, and selected fetuses may be candidates for in utero intervention. Following birth, palliation can be undertaken through staged operations: Norwood (or hybrid) in the 1st week of life, superior cavopulmonary connection at 4-6 months of life, and finally total cavopulmonary connection (Fontan) at 2-4 years of age. Children with hypoplastic left heart syndrome are at risk of circulatory failure their entire life, and selected patients may undergo heart transplantation. In this review article, we summarise recent advances in the critical care management of patients with hypoplastic left heart syndrome as were discussed in a focused session at the 12th International Conference of the Paediatric Cardiac Intensive Care Society held on 9 December, 2016, in Miami Beach, Florida.

Femoral vein homograft as Sano shunt results in improved pulmonary artery growth after Norwood operation

OBJECTIVE

To evaluate differences in interstage growth of pulmonary arteries between use of polytetrafluoroethylene and femoral vein homograft as Sano shunt during stage-I Norwood palliation.

METHODS

A retrospective review of all patients who survived to the second stage following Norwood-Sano operation at two institutions was performed. Either polytetrafluoroethylene or the valved segment of femoral vein homograft was used for construction of the Sano shunt. The size of pulmonary arteries was compared at pre-Glenn catheterisation.

RESULTS

A total of 48 neonates with the diagnosis of hypoplastic left heart syndrome or its variants comprised the study population. Femoral vein homograft of 5-6 mm diameter was used in 14 and polytetrafluoroethylene graft of 5 mm was used in 34 patients. The two groups were comparable in terms of preoperative demographics and age at time of pre-Glenn catheterisation (3.9±0.7 versus 3.4±0.8 months, p=0.06). Patients who received femoral vein homograft demonstrated a significantly higher pre-Glenn Nakata index [264 (130-460) versus 165 (108-234) mm2/m2, p=0.004]. The individual branch pulmonary arteries were significantly larger in the femoral vein group (right, 7.8±3.6 versus 5.0±1.2, p=0.014; left, 7.2±2.1 versus 5.6±1.9, p=0.02). There were no differences in cardiac index, Qp:Qs, ventricular end-diastolic pressure or systemic oxygen saturations.

CONCLUSIONS

Utilisation of a valved segment of femoral vein homograft as right ventricle to pulmonary artery conduit during Norwood-Sano operation confers better interstage growth of the pulmonary arteries. Further studies are needed to evaluate the impact of femoral vein homograft on single ventricle function.

Current Therapy for Hypoplastic Left Heart Syndrome and Related Single Ventricle Lesions

Universally fatal only 4 decades ago, the progress in the 3-stage palliation of hypoplastic left heart syndrome and related single right ventricular lesions has drastically improved the outlook for these patients. Although the stage II operation (hemi-Fontan or bidirectional Glenn) and stage III Fontan procedure have evolved into relatively low-risk operations, the stage I Norwood procedure remains one of the highest-risk and costliest common operations performed in congenital heart surgery. Yet, despite this fact, experienced centers now report hospital survivals of >90% for the Norwood procedure. This traditional 3-stage surgical palliation has seen several innovations in the past decade aimed at improving outcomes, particularly for the Norwood procedure. One significant change is a renewed interest in the right ventricle-to-pulmonary artery shunt as the source of pulmonary blood flow, rather than the modified Blalock-Taussig shunt for the Norwood. The multi-institutional Single Ventricle Reconstruction trial randomly assigned 555 patients to one or the other shunt, and these subjects continue to be followed closely as they now approach 10 years postrandomization. In addition to modifications to the Norwood procedure, the hybrid procedure, a combined catheter-based and surgical approach, avoids the Norwood procedure in the newborn period entirely. The initial hybrid procedure is then followed by a comprehensive stage II, which combines components of both the Norwood and the traditional stage II, and later completion of the Fontan. Proponents of this approach hope to improve not only short-term survival, but also potentially longer-term outcomes, such as neurodevelopment, as well. Regardless of the approach, traditional surgical staged palliation or the hybrid procedure, survivals have vastly improved, and large numbers of these patients are surviving not only through their Fontan in early childhood, but also into adolescence and young adulthood. As this population grows, it becomes increasingly important to understand the longer-term outcomes of these Fontan patients, not only in terms of survival, but also in terms of the burden of disease, neurodevelopmental outcomes, psychosocial development, and quality of life.

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.

Hypoplastic left heart syndrome: current perspectives

Since the first successful intervention for hypoplastic left heart syndrome (HLHS) was undertaken by Norwood in 1983, there have been many advancements in the pre-, intra-, and postoperative care of these children for a diagnosis that just 25 years ago was almost certainly a fatal one. This paper aims to describe the most recent trends and perspectives on the treatment of HLHS. In particular, we will discuss the five current options for HLHS, including Norwood stage I as the beginning to 3-stage palliation, transplant, true hybrid, hybrid-bridge-to-Norwood, and compassionate care.

Validation of a Simple Score to Determine Risk of Hospital Mortality After the Norwood Procedure

The ability to quantify patient-specific hospital mortality risk before the Norwood procedure remains elusive. This study aimed to develop an accurate and clinically feasible score to assess the risk of hospital mortality in neonates undergoing the Norwood procedure. All patients (n = 549) in the publically available Pediatric Heart Network Single Ventricle Reconstruction trial database were included in the analysis. Patients were randomly divided into a derivation (75%) and validation (25%) cohort. Preoperative factors found to be associated with mortality upon univariable analysis (P < 0.2) were included in the logistic regression model. The score was derived by including variables independently associated with mortality (P < 0.05). A 20-point score using 6 variables (birth weight, clinical syndrome or abnormal karyotype, surgeon Norwood volume or year, anatomic subtype, ascending aorta size, and obstructed pulmonary venous return) was developed using relative magnitudes of the covariates׳ odds ratio. The score was then tested in the validation cohort. In weighted regression analysis, model predicted risk of mortality correlated closely with actual rates of mortality in the derivation (R² = 0.87, P < 0.01) and validation cohorts (R² = 0.82, P < 0.01). Patients were classified as low (score: 0-5), medium (6-10), or high risk (>10). Mortality differed significantly between risk groups in both the derivation (6% vs 22% vs 77%, P < 0.01) and validation (4% vs 30% vs 53%, P < 0.01) cohorts. This mortality score is accurate in determining risk of hospital mortality in neonates undergoing planned Norwood operations. The score has the potential to be used in clinical practice to aid in risk assessment before surgery. Clinical trial registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT00115934.

Decision-Making for Surgery in the Management of Patients with Univentricular Heart

A series of technical refinements over the past 30 years, in combination with advances in perioperative management, have resulted in dramatic improvements in the survival of patients with univentricular heart. While the goal of single-ventricle palliation remains unchanged - normalization of the pressure and volume loads on the systemic ventricle, the strategies to achieve that goal have become more diverse. Optimal palliation relies on a thorough understanding of the changing physiology over the first years of life and the risks and consequences of each palliative strategy. This review describes how to optimize surgical decision-making in univentricular patients based on a current understanding of anatomy, physiology, and surgical palliation.

Challenges and controversies in fetal diagnosis and treatment: hypoplastic left heart syndrome

Today, almost 70% of babies with hypoplastic left heart syndrome (HLHS) will survive into adulthood, although significant long-term morbidity and mortality still exists. Prenatal diagnosis of HLHS is increasingly common, allowing improved counseling, and the potential for fetal intervention if indicated. Exciting progress continues to be made in the area of fetal diagnosis and intervention, specifically catheter intervention for intact atrial septum or severe aortic stenosis. Pediatric cardiologists should be keenly aware of the flaws of staged palliation for the treatment of HLHS, and need to keep abreast of the emerging data regarding fetal diagnosis and intervention.

Impact of initial shunt type on cardiac size and function in children with single right ventricle anomalies before the Fontan procedure: the single ventricle reconstruction extension trial

BACKGROUND

In children with single right ventricular (RV) anomalies, changes in RV size and function may be influenced by shunt type chosen at the time of the Norwood procedure.

OBJECTIVES

The study sought to identify shunt-related differences in echocardiographic findings at 14 months and ≤6 months pre-Fontan in survivors of the Norwood procedure.

METHODS

We compared 2-dimensional and Doppler echocardiographic indices of RV size and function, neo-aortic and tricuspid valve annulus dimensions and function, and aortic size and patency at 14.1 ± 1.2 months and 33.6 ± 9.6 months in subjects randomized to a Norwood procedure using either the modified Blalock-Taussig shunt (MBTS) or right ventricle to pulmonary artery shunt (RVPAS).

RESULTS

Acceptable echocardiograms were available at both time points in 240 subjects (114 MBTS, 126 RVPAS). At 14 months, all indices were similar between shunt groups. From the 14-month to pre-Fontan echocardiogram, the MBTS group had stable indexed RV volumes and ejection fraction, while the RVPAS group had increased RV end-systolic volume (p = 0.004) and decreased right ventricular ejection fraction (RVEF) (p = 0.004). From 14 months to pre-Fontan, the treatment groups were similar with respect to decline in indexed neo-aortic valve area, >mild neo-aortic valve regurgitation (<5% at each time), indexed tricuspid valve area, and ≥moderate tricuspid valve regurgitation (<20% at each time).

CONCLUSIONS

Initial Norwood shunt type influences pre-Fontan RV remodeling during the second and third years of life in survivors with single RV anomalies, with greater RVEF deterioration after RVPAS. Encouragingly, other indices of RV function remain stable before Fontan regardless of shunt type. (Comparison of Two Types of Shunts in Infants with Single Ventricle Defect Undergoing Staged Reconstruction-Pediatric Heart Network; NCT00115934).

Shunt choice in single right ventricle patients: an update

Hypoplastic left heart syndrome, the most common complex congenital heart malformation, is characterized by underdeveloped left-sided heart structures. The Norwood procedure followed by two-staged operations has permitted the extended survival of many of these patients. Survival, however, remains suboptimal with most of the morbidity and mortality occurring during the Norwood procedure hospitalization. The modified Blalock-Taussig shunt has been implicated in contributing to the mortality risk due to decreased systemic diastolic blood pressure and coronary perfusion. Therefore, the right ventricle-to-pulmonary artery shunt was recently reevaluated as a lower-risk source of pulmonary blood flow in the Norwood procedure. The Pediatric Heart Network Single Ventricle Reconstruction trial, sponsored by the NIH National Heart, Lung and Blood Institute, evaluated the two types of shunts during the Norwood procedure. This randomized clinical trial has yielded important insight into the effects of shunt selection on morbidity, mortality, hemodynamics and overall current outcomes for hypoplastic left heart syndrome.

Effect of ventriculotomy on right-ventricular remodeling in hypoplastic left heart syndrome: a histopathological and echocardiography correlation study

The objective of this study was to compare histopathological changes in hypoplastic left heart syndrome right ventricles (RV) of patients undergoing Sano and modified Blalock-Taussig (MBT) shunt and correlate them with echocardiographic findings. Myocardial tissue samples were obtained from hearts with Sano or MBT shunts after transplantation or at autopsy. Histologic sections were reviewed manually and by automated digital image analysis. Velocity vector imaging was performed on echocardiogram images obtained before transplant or death. All of these parameters were compared between the Sano and MBT shunt cohorts. A total of 14 specimens (7 Sano and 7 MBT shunt) were studied. Median age at transplant/death of Sano and MBT shunt cohorts was 11 (range 2-41) and 8 months (range 2-200), respectively. All Sano specimens had a scar at ventriculotomy site, and the mean scar area was 6.2 ± 3.3 cm(2). Compared with remote RV free wall, myocardium bordering the scar showed increased fibrosis (34 ± 16 % vs. 28 ± 14 %, p = 0.04) and thinning (0.8 ± 0.9 vs. 5.3 ± 0.8 mm; p < 0.001), which did not regress with time. The Sano ventriculotomy site showed significantly decreased velocity, strain, and strain rate compared with the corresponding contralateral segment. No focal scarring or regional hypokinesia was seen in the MBT shunt cohort. This is the first study to demonstrate histopathological features of ventriculotomy-associated RV myocardial scarring and myocardial thinning. The scarred ventriculotomy site showed decreased segmental myocardial deformation after Norwood with Sano shunt.

Short-term outcome comparison of Norwood procedures with right ventricle to pulmonary artery conduit versus modified Blalock-Taussig shunt: A meta-analysis

A small number of nonrandomized and retrospective studies have compared outcomes of classical Norwood procedures for hypoplasticleft-heart syndrome and single ventricle lesions involving a Blalock-Taussig (BT) shunt to the modified procedure using a right ventricle to pulmonary artery conduit. Some of these studies reported data for the same outcomes and a meta-analysis was done to analyze pooled outcomes comparing in-hospital mortality, interstage mortality, cardiopulmonary bypass time, systolic and diastolic blood pressures 24 h postoperatively, length of intensive care and hospital stay, and need for postoperative extracorporeal membrane oxygenation. Right ventricle to pulmonary artery conduit was associated with an insignificant reduction of in-hospital mortality (odds ratio, 0.674, 95% confidence interval, 0.367 to 1.238), and in the length of hospital stay. There were significant reductions in cardiopulmonary bypass time, length of intensive care unit stay, and need for postoperative extracorporeal membrane oxygenation, postoperative ventilation times, and interstage mortality (odds ratio, 0.191, confidence interval, 0.0620 to 0.587). There was a significant increase in diastolic blood pressure and an insignificant increase in systolic blood pressure 24 h postoperatively. This pooled analysis demonstrates potential advantages associated with the right ventricle to pulmonary artery conduit when compared to the modified BT shunt in palliation and demonstrates the need for large randomized controlled trials that compare a number of outcomes in both procedures.

Cause, timing, and location of death in the Single Ventricle Reconstruction trial

OBJECTIVES

The Single Ventricle Reconstruction trial randomized 555 subjects with a single right ventricle undergoing the Norwood procedure at 15 North American centers to receive either a modified Blalock-Taussig shunt or right ventricle-to-pulmonary artery shunt. Results demonstrated a rate of death or cardiac transplantation by 12 months postrandomization of 36% for the modified Blalock-Taussig shunt and 26% for the right ventricle-to-pulmonary artery shunt, consistent with other publications. Despite this high mortality rate, little is known about the circumstances surrounding these deaths.

METHODS

There were 164 deaths within 12 months postrandomization. A committee adjudicated all deaths for cause and recorded the timing, location, and other factors for each event.

RESULTS

The most common cause of death was cardiovascular (42%), followed by unknown cause (24%) and multisystem organ failure (7%). The median age at death for subjects dying during the 12 months was 1.6 months (interquartile range, 0.6 to 3.7 months), with the highest number of deaths occurring during hospitalization related to the Norwood procedure. The most common location of death was at a Single Ventricle Reconstruction trial hospital (74%), followed by home (13%). There were 29 sudden, unexpected deaths (18%), although in retrospect, 12 were preceded by a prodrome.

CONCLUSIONS

In infants with a single right ventricle undergoing staged repair, the majority of deaths within 12 months of the procedure are due to cardiovascular causes, occur in a hospital, and within the first few months of life. Increased understanding of the circumstances surrounding the deaths of these single ventricle patients may reduce the high mortality rate.

The use of reconstructive surgery to improve quality of life and survival in prenatal hypoplastic left heart syndrome

Outcomes for hypoplastic left heart syndrome have improved substantially in the era of prenatal diagnosis. Current stage 1 survival rates are in excess of 90% in the absence of risk factors. However, fetuses with an intact atrial septum continue to have poor postnatal survival. Accurate diagnosis of these fetuses with an intact atrial septum relies upon careful assessment of the patent foramen ovale, pulmonary venous Doppler flow patterns and branch pulmonary artery Doppler flow patterns. Prenatal and perinatal interventions, such as the placement of an atrial stent in utero or delivery at a center where a stent may be placed immediately after birth to relieve left atrial hypertension, may improve survival in this particularly high-risk group.

Risk factors for hospital morbidity and mortality after the Norwood procedure: A report from the Pediatric Heart Network Single Ventricle Reconstruction trial

OBJECTIVES

We sought to identify risk factors for mortality and morbidity during the Norwood hospitalization in newborn infants with hypoplastic left heart syndrome and other single right ventricle anomalies enrolled in the Single Ventricle Reconstruction trial.

METHODS

Potential predictors for outcome included patient- and procedure-related variables and center volume and surgeon volume. Outcome variables occurring during the Norwood procedure and before hospital discharge or stage II procedure included mortality, end-organ complications, length of ventilation, and hospital length of stay. Univariate and multivariable Cox regression analyses were performed with bootstrapping to estimate reliability for mortality.

RESULTS

Analysis included 549 subjects prospectively enrolled from 15 centers; 30-day and hospital mortality were 11.5% (63/549) and 16.0% (88/549), respectively. Independent risk factors for both 30-day and hospital mortality included lower birth weight, genetic abnormality, extracorporeal membrane oxygenation (ECMO) and open sternum on the day of the Norwood procedure. In addition, longer duration of deep hypothermic circulatory arrest was a risk factor for 30-day mortality. Shunt type at the end of the Norwood procedure was not a significant risk factor for 30-day or hospital mortality. Independent risk factors for postoperative renal failure (n = 46), sepsis (n = 93), increased length of ventilation, and hospital length of stay among survivors included genetic abnormality, lower center/surgeon volume, open sternum, and post-Norwood operations.

CONCLUSIONS

Innate patient factors, ECMO, open sternum, and lower center/surgeon volume are important risk factors for postoperative mortality and/or morbidity during the Norwood hospitalization.

Age- and chamber-specific differences in oxidative stress after ischemic injury

Each year, tens of thousands of children undergo cardiopulmonary bypass (CPB) to correct congenital heart defects. Although necessary for surgery, CPB involves stopping the heart and exposing it to ischemic conditions. On reoxygenation, the heart can experience effects similar to that of acute myocardial infarction. Although much is known about adult injury, little is known about the effects of global ischemia on newborn ventricles. We studied newborn (2 to 4 days old) and adult (>8 weeks old) rabbit hearts subjected to ischemia-reperfusion (30 min of ischemia and 60 min of reperfusion). Our data demonstrated chamber- and age-specific changes in oxidative stress. During ischemia, hydrogen peroxide (H(2)O(2)) increased in both right-ventricular (RV) and left-ventricular (LV) myocytes of the newborn, although only the RV change was significant. In contrast, there was no significant increase in H(2)O(2) in either RV or LV myocytes of adults. There was a fivefold increase in H(2)O(2) formation in newborn RV myocytes compared with adults (P = 0.006). In whole-heart tissue, superoxide dismutase activity increased from sham versus ischemia in the left ventricle of both adult and newborn hearts, but it was increased only in the right ventricle of the newborn heart. Catalase activity was significantly increased after ischemia in both adult ventricles, whereas no increase was seen in newborn compared with sham hearts. In addition, catalase levels in newborns were significantly lower, indicating less scavenging potential. Nanoparticle-encapsulated ebselen, given as an intracardiac injection into the right or left ventricle of newborn hearts, significantly increased functional recovery of developed pressure only in the right ventricle, indicating the potential for localized antioxidant therapy during and after pediatric surgical procedures.

Myocardial alternative RNA splicing and gene expression profiling in early stage hypoplastic left heart syndrome

Hypoplastic Left Heart Syndrome (HLHS) is a congenital defect characterized by underdevelopment of the left ventricle and pathological compensation of the right ventricle. If untreated, HLHS is invariably lethal due to the extensive increase in right ventricular workload and eventual failure. Despite the clinical significance, little is known about the molecular pathobiological state of HLHS. Splicing of mRNA transcripts is an important regulatory mechanism of gene expression. Tissue specific alterations of this process have been associated with several cardiac diseases, however, transcriptional signature profiles related to HLHS are unknown. In this study, we performed genome-wide exon array analysis to determine differentially expressed genes and alternatively spliced transcripts in the right ventricle (RV) of six neonates with HLHS, compared to the RV and left ventricle (LV) from non-diseased control subjects. In HLHS, over 180 genes were differentially expressed and 1800 were differentially spliced, leading to changes in a variety of biological processes involving cell metabolism, cytoskeleton, and cell adherence. Additional hierarchical clustering analysis revealed that differential gene expression and mRNA splicing patterns identified in HLHS are unique compared to non-diseased tissue. Our findings suggest that gene expression and mRNA splicing are broadly dysregulated in the RV myocardium of HLHS neonates. In addition, our analysis identified transcriptome profiles representative of molecular biomarkers of HLHS that could be used in the future for diagnostic and prognostic stratification to improve patient outcome.

Hypoplastic left heart syndrome: current considerations and expectations

In the recent era, no congenital heart defect has undergone a more dramatic change in diagnostic approach, management, and outcomes than hypoplastic left heart syndrome (HLHS). During this time, survival to the age of 5 years (including Fontan) has ranged from 50% to 69%, but current expectations are that 70% of newborns born today with HLHS may reach adulthood. Although the 3-stage treatment approach to HLHS is now well founded, there is significant variation among centers. In this white paper, we present the current state of the art in our understanding and treatment of HLHS during the stages of care: 1) pre-Stage I: fetal and neonatal assessment and management; 2) Stage I: perioperative care, interstage monitoring, and management strategies; 3) Stage II: surgeries; 4) Stage III: Fontan surgery; and 5) long-term follow-up. Issues surrounding the genetics of HLHS, developmental outcomes, and quality of life are addressed in addition to the many other considerations for caring for this group of complex patients.

Neonatal surgical reconstruction and peri-operative care for hypoplastic left heart syndrome: current strategies

The management of newborns with hypoplastic left heart syndrome has changed significantly over the past three decades, with an associated dramatic improvement in outcomes. The aim of this paper is to discuss current peri-operative and palliative surgical strategies. Owing to the fact that comparative outcomes for these strategies have been addressed in a limited number of prospective trials and extractions from multi-centred databases, the primary focus of this review is descriptive.

Norwood procedure with non-valved right ventricle to pulmonary artery shunt improves ventricular energetics despite the presence of diastolic regurgitation: a theoretical analysis

When the Norwood procedure is conducted for the hypoplastic left heart syndrome using a non-valved right ventricle (RV) to pulmonary artery (PA) shunt, diastolic regurgitation from PA to RV may have an adverse effect on postoperative hemodynamics. In this study, we examined the impact of the diastolic regurgitation on ventricular energetics by computational analysis using a combination of a time-varying elastance chamber model and a modified three-element Windkessel vascular model. This study revealed that use of the valved or non-valved RV-PA shunt eliminated pulmonary over-circulation which was observed when using the systemic to pulmonary artery shunt (modified Blalock-Taussig shunt). Although the valved RV-PA shunt improved pulmonary blood supply and consequently increased pulmonary artery flow and oxygen saturation compared to the non-valved RV-PA shunt, the non-valved RV-PA shunt improved ventricular energetics in spite of the presence of PA to RV regurgitation.

Congenital heart diseases: post-operative appearance on multi-detector CT-a pictorial essay

Echocardiography is considered as an initial imaging modality of choice in patients with congenital heart disease (CHD), and magnetic resonance (MR) imaging is preferred for detailed functional information. Multi-detector computed tomography (CT) plays an important role in clinical practice in assessing post-operative morphological and functional information of patients with complex CHD when echocardiography and MR imaging are not contributory. Radiologists should understand and become familiar with the complex morphology and physiology of CHD, as well as with various palliative and corrective surgical procedures performed in these patients, to obtain CT angiograms with diagnostic quality and promptly recognise imaging features of normal post-operative anatomy and complications of these complex surgeries.

Celiac artery flow pattern in infants with single right ventricle following the Norwood procedure with a modified Blalock-Taussig or right ventricle to pulmonary artery shunt

A potential advantage of the right ventricle to pulmonary artery versus modified Blalock-Taussig shunt in patients undergoing the Norwood procedure is limitation of diastolic runoff from the systemic to pulmonary circulation. We evaluated mesenteric flow patterns and gastrointestinal outcomes following the Norwood procedure associated with either shunt type. Patients randomized to a right ventricle to pulmonary artery versus modified Blalock-Taussig shunt in the Pediatric Heart Network Single Ventricle Reconstruction Trial at centers participating in this ancillary study were eligible for inclusion; those with active necrotizing enterocolitis, sepsis, or end-organ dysfunction were excluded. Celiac artery flow characteristics and gastrointestinal outcomes were collected at discharge. Forty-four patients (five centers) were included. Median age at surgery was 5 days [interquartile range (IQR) = 4-8 days]. Median celiac artery resistive index (an indicator of resistance to perfusion) was higher in the modified Blalock-Taussig shunt group (n = 19) versus the right ventricle to pulmonary artery shunt group (n = 25) [1.00 (IQR = 0.84-1.14) vs. 0.82 (IQR = 0.74-1.00), p = 0.02]. There was no difference in interstage weight gain, necrotizing enterocolitis, or feeding intolerance episodes between the groups. The celiac artery resistive index was higher in patients with the modified Blalock-Taussig shunt versus the right ventricle to pulmonary artery shunt but was not associated with measured gastrointestinal outcomes.

Right ventricle and tricuspid valve function at midterm after the Fontan operation for hypoplastic left heart syndrome: impact of shunt type

This study aimed to evaluate clinical outcomes including hemodynamics, right ventricle (RV) function, and tricuspid valve (TV) function in patients with hypoplastic left heart syndrome (HLHS) at midterm after completion of staged palliation based on the source of pulmonary blood flow provided at stage 1. The records of all patients with HLHS who completed Fontan palliation between 2001 and 2007 were retrospectively reviewed. The outcome variables were RV dysfunction, TV, and neo-atrioventricular (neo-AV) regurgitation (from latest echocardiogram), cardiac index (CI), pulmonary vascular resistance (PVR), pulmonary artery pressure (PAp), and right ventricular end-diastolic pressure (RVEDp) (from latest catheterization). Clinical status was obtained from medical records and by contact with the referring cardiologist if necessary. Of 118 patients undergoing a Fontan for HLHS, 116 had a fenestrated lateral tunnel and 2 had an extracardiac conduit. At the time of stage 1 palliation, 36 patients had a right ventricle-to-pulmonary artery (RV-PA) conduit, and 82 patients had a modified Blalock-Taussig shunt (mBTS). All the patients except one who died of sepsis on extracorporeal membrane oxygenation (ECMO) survived the Fontan operation and were discharged home. At a mean follow-up post-Fontan period of 28.4 months (range, 0.16-95.3 months), three patients had died (2 on the transplantation list and 1 from pulmonary vein stenosis), and one patient had the Fontan circulation taken down. No patient had a heart transplantation. A follow-up echocardiogram was performed for 115 patients (after a mean of 15.6 months for RV-PA and 32.1 months for BTS), and 66 patients underwent a post-Fontan catheterization (after a mean of 15.8 months for RV-PA and 29.3 months for BTS). The hemodynamic results for RV-PA conduit versus BTS were a CI of 3.4 ± 0.8 versus 3.4 ± 1.2, a PVR of 1.8 ± 0.7 versus 1.7 ± 0.8, a PAp of 14.3 ± 3.1 versus 14.2 ± 4.5, and an RVEDp of 7.1 ± 3.3 versus 8.9 ± 5.3. No statistically significant differences were found between shunt types regarding survival or degree of RV dysfunction or in terms of neo-AV regurgitation, CI, PVR, PAp, RVEDp, or rhythm problems. Patients in the BTS group required more tricuspid valvuloplasties and had more tricuspid regurgitation at follow-up evaluation. The patients in the RV-PA group had more PA interventions. In conclusion, the contemporary results after Fontan palliation for HLHS were excellent. At the midterm follow-up evaluation, outcomes and hemodynamic data were similar between shunt types. However, the patients in the BTS group exhibited more tricuspid regurgitation, and the patients in the RV-PA group had increased pulmonary artery interventions.

Comparison of Norwood shunt types: do the outcomes differ 6 years later?

BACKGROUND

A modification to the Norwood procedure involving a right ventricle-to-pulmonary artery (RV-PA) shunt may improve early postoperative outcomes. Concerns remain about the effect of the right ventriculotomy required with this shunt on long-term ventricular function.

METHODS

Between January 2000 and April 2005, 76 patients underwent the Norwood procedure, 35 with a modified Blalock-Taussig shunt (mBTS) and 41 with a RV-PA shunt. Patients were monitored until death or September 1, 2009, with an average follow-up of 6.8 years. Cardiac catheterization, echocardiograms, perioperative Fontan courses, and need for cardiac transplantation were compared between groups.

RESULTS

Cumulative survival was 63% (22 of 35) in the mBTS group vs 78% (32 of 41) in the RV-PA group (p = 0.14). Pre-Fontan echocardiography revealed poorer ventricular function in RV-PA patients (p = 0.03). Cardiac transplantation was required in 6 of 32 (19%) patients with a prior RV-PA shunt vs 1 of 23 (4%) in the mBTS group (p = 0.06). This results in an almost identical cumulative transplant-free survival between groups; 60% (21 of 35) in the mBTS group and 63% (26 of 41) in the RV-PA group (p = 0.95).

CONCLUSIONS

Neither shunt offers a clear survival advantage through an average follow-up of 6.8 years. The RV-PA shunt results in impaired late ventricular function that may result in an increased need for cardiac transplantation.

Hard Choices for High-Risk Patients With Critical Left Ventricular Outflow Obstruction

Surgical management of high-risk newborns with critical left ventricular outflow tract obstruction (LVOTO) involves difficult decision making and complex procedures associated with significant morbidity and mortality. We sought to compare the outcomes of the hybrid and surgical strategies for the management of neonates with critical LVOTO considered at high risk in a contemporary nonrandomized cohort. This is a retrospective review of all patients undergoing management of critical LVOTO between January 2001 and December 2008. High-risk conditions included prematurity, low birth weight, and genetic or associated cardiac and noncardiac pathology. Analysis was performed based on intention to treat. Primary and secondary outcomes were operative and 6-month mortality. The cohort included 55 patients (21 hybrid and 34 surgical [31 Norwood, 3 biventricular repair]). The cohort had a median age of 4 (range, 1-62) days, mean weight of 2.7 ± 0.5 kg, and Aristotle comprehensive score of 18.6 ± 2.9. Low birth weight ( P = .0007), prematurity ( P = .004), and organ dysfunction ( P = .04) were risk factors for operative death. Six-month mortality was associated with need for reintervention ( P = .017) in the surgical group and history of organ dysfunction ( P = .02) or aortic atresia ( P = .03) in the hybrid group. Logistic regression identified low birth weight ( P = .05; odds ratio [OR], 5.6 [0.9-34.6]), organ dysfunction ( P = .05; OR, 4.7 [0.9-22.5]), and non–hypoplastic left heart syndrome (HLHS) diagnosis ( P = .03; OR, 0.06 [0.005-0.93]) as predictors of mortality for the entire cohort. No differences in operative and 6-month mortality were detected between management strategies. Although initial surgical insult is lessened by the hybrid palliation, important interstage mortality and ongoing morbidity result in similar 6-month survival with either strategy. Patient-related factors have a larger influence on outcome than the management strategy chosen.

Comparison of shunt types in the Norwood procedure for single-ventricle lesions

BACKGROUND

The Norwood procedure with a modified Blalock-Taussig (MBT) shunt, the first palliative stage for single-ventricle lesions with systemic outflow obstruction, is associated with high mortality. The right ventricle-pulmonary artery (RVPA) shunt may improve coronary flow but requires a ventriculotomy. We compared the two shunts in infants with hypoplastic heart syndrome or related anomalies.

METHODS

Infants undergoing the Norwood procedure were randomly assigned to the MBT shunt (275 infants) or the RVPA shunt (274 infants) at 15 North American centers. The primary outcome was death or cardiac transplantation 12 months after randomization. Secondary outcomes included unintended cardiovascular interventions and right ventricular size and function at 14 months and transplantation-free survival until the last subject reached 14 months of age.

RESULTS

Transplantation-free survival 12 months after randomization was higher with the RVPA shunt than with the MBT shunt (74% vs. 64%, P=0.01). However, the RVPA shunt group had more unintended interventions (P=0.003) and complications (P=0.002). Right ventricular size and function at the age of 14 months and the rate of nonfatal serious adverse events at the age of 12 months were similar in the two groups. Data collected over a mean (+/-SD) follow-up period of 32+/-11 months showed a nonsignificant difference in transplantation-free survival between the two groups (P=0.06). On nonproportional-hazards analysis, the size of the treatment effect differed before and after 12 months (P=0.02).

CONCLUSIONS

In children undergoing the Norwood procedure, transplantation-free survival at 12 months was better with the RVPA shunt than with the MBT shunt. After 12 months, available data showed no significant difference in transplantation-free survival between the two groups. (ClinicalTrials.gov number, NCT00115934.)

The Norwood procedure using a right ventricle-pulmonary artery conduit: comparison of the right-sided versus left-sided conduit position

OBJECTIVE

We proposed that a right-sided right ventricle-pulmonary artery conduit during the stage I Norwood procedure would facilitate pulmonary artery reconstruction during the stage II procedure.

METHODS

Between 2002 and 2006, 153 patients underwent Norwood stage I reconstruction with a right ventricle-pulmonary artery conduit (125 in the right-sided group and 28 in the left-sided group). The previous 150 consecutive classic Norwood procedures (1997-2002) were used as a control group. Outcomes from stages I and II were analyzed, including ventricular function and pulmonary artery morphology.

RESULTS

The 30-day survival was 88% (110/125) in the right-sided group, 75% (21/28) in the left-sided group, and 70% (105/150) in the control group (P < .001, right-sided vs control groups). The conduit length was 35 +/- 9 mm in the right-sided group and 26 +/- 8 mm in the left-sided group (P = .001). Survival at 6 months demonstrated a significant survival benefit in the right-sided right ventricle-pulmonary artery conduit group over the control group (P = .009, log-rank test). There was no difference in ventricular function between the groups and no regional dyskinesia associated with the right ventricle-pulmonary artery conduit. Despite larger branch pulmonary artery size in the right ventricle-pulmonary artery conduit groups (compared with the control group), central pulmonary artery stenoses were common (62% in the right conduit and 80% in the left conduit). Bypass and ischemic times at stage II were 49 +/- 10 and 23 +/- 13 minutes in the right-sided group compared with 61.5 +/- 9.5 and 31 +/- 14 minutes in the left-sided group (P < .001 and P = .03, respectively). The 30-day mortality after the stage II procedure was 1.3% (1/76) in the right-sided group, 0% (0/18) in the left-sided group, and 3.3% (3/90) in the control group.

CONCLUSION

The right-sided conduit is a safe technique and has improved 30-day and overall post-stage II survival compared with that seen with the classic Norwood procedure. The right ventricle-pulmonary artery conduit is associated with central pulmonary artery stenosis but good development of the branch pulmonary arteries and preservation of ventricular function. The right-sided conduit significantly reduces cardiopulmonary bypass times at stage II.

Two-Year Survival and Mental and Psychomotor Outcomes After the Norwood Procedure

Background— The Norwood procedure for stage 1 palliation of hypoplastic left heart syndrome is performed with either the modified Blalock-Taussig (MBTS) or the right ventricle–to–pulmonary artery (RVPA) shunt. In our institution, surgical practice changed from use of the MBTS to use of the RVPA shunt in 2002. We analyzed survival and mental and psychomotor outcomes of the 2 consecutive surgical eras.

Methods and Results— Between September 1996 and July 2005, 94 neonates with hypoplastic left heart syndrome underwent the Norwood procedure. Patients were recruited as neonates and followed up prospectively. Health, mental, and psychomotor outcomes (Bayley Scales of Infant Development-II) were assessed at 2 years. The study subjects were from the Norwood-MBTS era (n=62; 1996 to 2002) or the Norwood-RVPA era (n=32; 2002 to 2005). In the MBTS era, early and 2-year mortality rates were 23% (14/62) and 52% (32/62); the mean (SD) mental and psychomotor developmental indices were 79 (18) and 67 (19). In the RVPA era, early and 2-year mortality rates were 6% (2/32) and 19% (6/32); the mean (SD) mental and psychomotor developmental indices were 85 (18) and 78 (18). The 2-year mortality rate ( P =0.002) and the psychomotor developmental index ( P =0.029) were improved in the more recent surgical era. On multivariable Cox regression analysis, postoperative highest serum lactate independently predicted 2-year mortality in the MBTS and RVPA eras.

Conclusions— Analysis of 2 consecutive surgical eras of hypoplastic left heart syndrome patients undergoing the Norwood procedure showed a significant improvement in 2-year survival and psychomotor development in the more recent era. Adverse neurodevelopmental outcome in this patient population remains a concern.

Pathological changes and myocardial remodelling related to the mode of shunting following surgical palliation for hypoplastic left heart syndrome

BACKGROUND

The modification of placing the shunt from the right ventricle to the pulmonary arteries, also known as Sano procedure, has allegedly improved results over the short term in surgical palliation of hypoplastic left heart syndrome with the Norwood procedure. With this in mind, we reviewed autopsied specimens from neonates and children who did not survive after either a classic arterio-pulmonary shunt, or the modified procedure with the shunt placed from the right ventricle to the pulmonary arteries, so as to evaluate the pathological substrates of the remodelling of the systemic right ventricle, assessing any differences induced by the 2 techniques.

METHODS

We obtained the hearts from 11 patients with neonatal diagnosis of hypoplastic left heart syndrome who died after the first or second stages of the Norwood sequence of operations, comparing them with 6 normal hearts matched for age and weight. Macroscopic, microscopic and morphometric analysis were performed on each specimen, evaluating the diameter of the myocytes, extracellular matrix remodelling in terms of fibrosis and type of collagen, and vascularization in terms of capillary density.

RESULTS

Hypertrophy of the myocytes was significantly increased in the hearts from patients having either a classic arterio-pulmonary or the ventriculo-pulmonary modification of the shunt compared to controls (p < 0.05). Myocardial fibrosis was increased in those having a shunt placed from the right ventricle to the pulmonary arteries when compared to the other 2 groups. The ratio of collagen I to collagen III was similar in those undergoing a classic arterio-pulmonary shunt compared to controls (0.94), but was lower in those having a shunt placed from the right ventricle to the pulmonary arteries (0.61), with an increase in collagen type III. The density of capillaries was lower in those who had undergone a classic arterial shunt when compared to the others.

CONCLUSION

We have shown greater remodelling of the ventricular myocardial extracellular matrix in patients having a shunt from the right ventricle to the pulmonary arteries when compared to those having a classic arterio-pulmonary shunt, with this remodelling progressing even after the neonatal period. This may influence a later suboptimal ventricular performance.

Principles of antegrade cerebral perfusion during arch reconstruction in newborns/infants

Antegrade cerebral perfusion (ACP) is a cardiopulmonary bypass technique that uses special cannulation procedures to perfuse only the brain during neonatal and infant aortic arch reconstruction. It is used in lieu of deep hypothermic circulatory arrest (DHCA), and thus has the theoretical advantage of protecting the brain from hypoxic ischemic injury. Despite this, recent comparative studies have shown no difference in neurodevelopmental outcomes with ACP versus DHCA for neonatal arch repair. This article presents animal and human data demonstrating that ACP flows less than 30 mL/kg/min are inadequate for many patients, and may be the explanation for lack of outcome difference versus DHCA. A technique for ACP, its physiologic basis, and a neuromonitoring strategy are presented, and then the results of an outcome study are reviewed, showing that with ACP technique at higher flows of 50 to 80 mL/kg/min guided by neuromonitoring, periventricular leukomalacia is eliminated on postoperative brain magnetic resonance imaging after neonatal cardiac surgery.

Cardiovascular magnetic resonance of pulmonary artery growth and ventricular function after Norwood procedure with Sano modification

For hypoplastic left heart syndrome (HLHS), there have been concerns regarding pulmonary artery growth and ventricular dysfunction after first stage surgery consisting of the Norwood procedure modified with a right ventricle-to-pulmonary artery conduit. We report our experience using cardiovascular magnetic resonance (CMR) to determine and follow pulmonary arterial growth and ventricular function in this cohort. Following first stage palliation, serial CMR was performed at 1 and 10 weeks post-operatively, followed by cardiac catheterization at 4-6 months. Thirty-four of 47 consecutive patients with HLHS (or its variations) underwent first stage palliation. Serial CMR was performed in 20 patients. Between studies, ejection fraction decreased (58 +/- 9% vs. 50 +/- 5%, p < 0.05). Pulmonary artery growth occurred on the left (6 +/- 1 mm vs. 4 +/- 1 mm at baseline, p < 0.05) but not significantly in the right. This trend continued to cardiac catheterization 4-6 months post surgery, with the left pulmonary artery of greater size than the right (8.8 +/- 2.2 mm vs. 6.7 +/- 1.9 mm, p < 0.05). By CMR, 5 had pulmonary artery stenoses initially, and at 2 months, 9 had stenoses. Three of the 9 underwent percutaneous intervention prior to the second stage procedure. In this cohort, reasonable growth of pulmonary arteries occurred following first stage palliation with this modification, although that growth was preferential to the left. Serial studies demonstrate worsening of ventricular function for the cohort. CMR was instrumental for detecting pulmonary artery stenosis and right ventricular dysfunction.

Stage I palliation for hypoplastic left heart syndrome: Is a right ventricle to pulmonary artery conduit associated with improved outcomes? Critical appraisal of Cua et al: Early postoperative outcomes in a series of infants with hypoplastic left heart syndrome undergoing stage I palliation operation with either modified Blalock-Taussig shunt or right ventricle to pulmonary artery conduit (Pediatr Crit Care Med 2006; 7:238-244)

OBJECTIVE

To review the findings and discuss the implications of studies comparing Norwood procedure with either modified Blalock-Taussig shunt (NW-BT) or right ventricle to pulmonary artery conduit (NW-RVPA) in stage I palliation of hypoplastic left heart syndrome (HLHS).

DESIGN

A critical appraisal of "Early postoperative outcomes in a series of infants with hypoplastic left heart syndrome undergoing stage I palliation operation with either modified Blalock-Taussig shunt or right ventricle to pulmonary artery conduit" by Cua et al. (Pediatr Crit Care Med 2006; 7:238-244) with literature review.

FINDINGS

Several retrospective studies using historical controls have reported improved results with NW-RVPA compared with NW-BT for stage I palliation of HLHS. The study by Cua et al. is one of a few recent articles with concurrent series that have found no difference in early postoperative mortality or morbidity, although in comparison with the NW-BT group, the NW-RVPA group had significantly shorter duration of mechanical ventilation, decreased length of intensive care unit stay and hospital stay, and shorter time to sternal closure and to establishment of enteral feeds.

CONCLUSIONS

NW-RVPA has theoretical advantages over NW-BT and is associated with excellent outcome results. However, available data are insufficient to prove benefit in terms of mortality or morbidity. A multicenter randomized trial is currently being conducted, which should provide more conclusive information.

Design and rationale of a randomized trial comparing the Blalock-Taussig and right ventricle-pulmonary artery shunts in the Norwood procedure

OBJECTIVE

The initial palliative procedure for patients born with hypoplastic left heart syndrome and related single right ventricle anomalies, the Norwood procedure, remains among the highest risk procedures in congenital heart surgery. The classic Norwood procedure provides pulmonary blood flow with a modified Blalock-Taussig shunt. Improved outcomes have been reported in a few small, nonrandomized studies of a modification of the Norwood procedure that uses a right ventricle-pulmonary artery shunt to provide pulmonary blood flow. Other nonrandomized studies have shown no differences between the two techniques.

METHODS

The Pediatric Heart Network designed a randomized clinical trial to compare outcomes for subjects undergoing a Norwood procedure with either the right ventricle-pulmonary artery or modified Blalock-Taussig shunt. Infants with a diagnosis of single, morphologically right ventricle anomaly who are undergoing a Norwood procedure are eligible for inclusion in this study. The primary outcome is death or cardiac transplant 12 months after random assignment. Secondary outcomes include postoperative morbidity after Norwood and stage II palliation procedures, right ventricular function and pulmonary arterial growth at stage II palliation, and neurodevelopmental outcomes at 14 months old. Incidence of adverse events will also be compared between treatment groups.

CONCLUSION

This study will make an important contribution to the care of patients with hypoplastic left heart syndrome and related forms of single, morphologically right ventricle. It also establishes a model with which other operative interventions for patients with congenital cardiovascular malformations can be evaluated in the future.

Outcomes of surgical treatment of infants with hypoplastic left heart syndrome: an institutional experience 1983-2004

AIM

To determine outcomes of surgical treatment of infants with hypoplastic left heart syndrome (HLHS).

METHODS

Retrospective analysis of medical records of infants with HLHS.

RESULTS

129 of 206 (63%) infants with HLHS were managed surgically over the period 1983-2004. Survival from all stages of surgical repair was 52 (40%) patients with significantly different (P < 0.001) survival according to surgical techniques and post-operative intensive care management recognisable in three eras. During 1983-1995 a classical Norwood stage 1 operation with a systemic-pulmonary shunt was performed for 61 infants with 13 (21%) survivors. From 1996 to 2002, pulmonary vasoconstriction and systemic vasodilatation after stage 1 operation were used to optimise systemic blood flow yielding a survival of 22 of 46 (48%) infants. From 2002 to 2004 a ventricular-pulmonary conduit was used with survival of 17 of 22 (77%) infants. Survival at 1, 6, 12 months and at 5, 10 and 15 years was 65%, 53%, 48%, 38%, 38% and 25%, respectively. The mean +/- SD number of surgical procedures was 4.5 +/- 3.7; duration of hospitalisation 53 +/- 52 days (median 38); number of hospital admissions 3.0 +/- 3.5; duration in intensive care 18 +/- 20 days (median 11); hours of mechanical ventilation 278 +/- 398 (median 151).

CONCLUSION

Short-term survival of HLHS has improved substantially over recent years with a ventricular-pulmonary conduit while long-term survival has been mediocre after arterial systemic-pulmonary shunts. Irrespective of type of primary surgery, infants undergo many operations and spend long periods in hospital and intensive care.