Unifocalization cannot rely exclusively on native pulmonary arteries: the importance of recruitment of major aortopulmonary collaterals in 249 cases†

OBJECTIVES

We sought to define the early and late outcomes of unifocalization based on a classification of the native pulmonary artery (nPA) system and major aortopulmonary collateral arteries (MAPCAs) with a policy of combined recruitment and rehabilitation and to analyse the role of unifocalization by leaving the ventricular septal defect (VSD) open with a limiting right ventricle-pulmonary artery (RV-PA) conduit in borderline cases.

METHODS

An analysis of 271 consecutive patients assessed for unifocalization at a single institution between 1988 and 2016 was performed. Patients were classified according to the pulmonary blood supply: group A, unifocalization based on nPA only; group B, based on nPA and MAPCAs; group C, MAPCAs only (absent nPAs).

RESULTS

Unifocalization was achieved in 249 (91.9%) cases with an early mortality of 2.8%. Group A included 72 (28.9%) patients, group B 119 (47.8%) patients and group C 58 (23.3%) patients with no difference in early survival between groups. Survival at 5, 10 and 15 years was 90.0% (85.9-94.3), 87.2% (83.5-91.2) and 82.3% (75.2-89.9), respectively. Late survival in groups A and B was similar but 10- and 15-year survival in group C decreased to 79.2% (68.2-92.1) and 74.3% (61.1-90.4) (P = 0.02), respectively. A mean of 1.9 (±0.6) MAPCAs were recruited per patient (range 0-6). The VSD was left open with a limiting RV-PA conduit in 97 (39.0%) cases, but subsequently closed in 48 patients, giving a total of 200 (80.3%) patients achieving VSD closure (full repair). Delaying VSD closure was not associated with increased risk for early or late survival. A central shunt to rehabilitate the nPAs was used in 56 (22.5%) cases. This was associated with a reduction in the number of MAPCAs recruited, but still required a mean of 1.8 (±0.5) MAPCAs recruited per patient to achieve unifocalization. In multivariate risk analysis, those suitable for single-stage full repair had the best long-term outcomes. Group C anatomy was associated with poor late survival compared to groups A and B (hazard ratio 2.7).

CONCLUSIONS

Survival is maximized by a combined approach of rehabilitation and recruitment. MAPCAs should always be recruited if they supply areas with absent nPA supply. A strategy of leaving the VSD open with a limiting RV-PA conduit is a safe and effective way of managing borderline cases.

Tetralogy of Fallot: morphological variations and implications for surgical repair

OBJECTIVES

Tetralogy of Fallot is characterized by anterocephalad deviation of the outlet septum, along with abnormal septoparietal trabeculations, which lead to subpulmonary infundibular stenosis. Archives of retained hearts are an important resource for improving our understanding of congenital heart defects and their morphological variability. This study aims to define variations in aortic override, coronary arterial patterns and ventricular septal defects in tetralogy of Fallot as observed in a morphological archive, highlighting implications for surgical management.

METHODS

The Birmingham Children's Hospital archive contains 211 hearts with tetralogy of Fallot, of which 164 were analysed [69 (42.1%) unrepaired and 95 (57.9%) operated specimens]. A detailed morphological and geometric analysis was performed using a rigorous 5-layer review process.

RESULTS

Anomalies were observed in the orifices, origins and course of the coronary arteries: 20 hearts (13.0%) had more than 2 orifices and 3 hearts (1.9%) had a single orifice. In 7 hearts (4.3%), a coronary artery crossed the right ventricular outflow tract. The extent of aortic override ranged from 31.0% to 100% (median of 59.5%). The ventricular septal defect was most often perimembranous (139, 84.8%), but we also found muscular (14, 8.5%), atrioventricular (7, 4.3%) and doubly committed juxta-arterial (2, 1.2%) variants.

CONCLUSIONS

Anatomical variations are common and can impact surgical management. Anomalous coronary arteries may require a conduit rather than a transannular patch. Variability in aortic override determines the size of patch used to baffle blood to the aorta. The type of ventricular septal defect affects patch closure and the risk of postoperative conduction defects.

Bentall procedure for the repair of a neoaortic aneurysm after the Norwood procedure in a patient with tricuspid atresia and a discordant ventriculo-arterial connection

Neoaortic root dilation is a common phenomenon after the Norwood procedure, but the real incidence and its natural history are unclear. Regular surveillance in these patients after the operation is necessary. Herein, we present an 11-year-old boy born with tricuspid atresia, a discordant ventriculo-arterial connection and a hypoplastic aortic arch, who was palliated initially with a hybrid stage I procedure involving a reversed Blalock-Taussig shunt, followed by comprehensive stage II and then, an extra-cardiac fenestrated Fontan operation. The patient developed an aortic root aneurysm and severe aortic regurgitation. He was electively taken into the operating room, where cardiopulmonary bypass was established through a peripheral cannulation of the femoral vessels due to the high risk nature of the reoperation. A mechanical Bentall procedure was performed without residual lesions and the native ascending aorta was anastomosed as a single coronary button to the anterior wall of the graft.

Defining transposition: What have we learnt?

Understanding transposition is important for all who hope to effectively treat patients with the condition. The variants of the condition are frequently debated in the literature. We describe an unusual variant of transposition, in which despite the arterial roots being supported by morphologically inappropriate ventricles, the roots themselves were normally related, with the intrapericardial arterial trunks spiraling as they extended into the mediastinum. The specimen was identified following the re-categorization of our archive, and we subsequently conducted a detailed analysis of the underlying morphology. Using the principles of sequential segmental analysis, we compared the morphology with standard examples previously described. We show how it was the recognition of such hearts that promoted that concept that the combination of connections across the atrioventricular and ventriculo-arterial junctions was the essence of transposition. In the most common variant, the arrangements are concordant at the atrioventricular junctions, but discordant at the ventriculo-arterial junctions. We suggest that the overall arrangement of discordant ventriculo-arterial connections is best described simply as “transposition.” When the discordant ventriculo-arterial connections are combined with similarly discordant connections at the atrioventricular junctions, the transposition is congenitally corrected. We point out that the use of “d” and “l” as prefixes does not distinguish between transposition and its congenitally corrected variant. For those using segmental notations, the correct description for the rare variant found in the setting of a posteriorly located aortic root with the usual atrial arrangement is transposition (S, D, NR).

Early morbidities following paediatric cardiac surgery: a mixed-methods study

Background

Over 5000 paediatric cardiac surgeries are performed in the UK each year and early survival has improved to > 98%.

Objectives

We aimed to identify the surgical morbidities that present the greatest burden for patients and health services and to develop and pilot routine monitoring and feedback.

Design and setting

Our multidisciplinary mixed-methods study took place over 52 months across five UK paediatric cardiac surgery centres.

Participants

The participants were children aged < 17 years.

Methods

We reviewed existing literature, ran three focus groups and undertook a family online discussion forum moderated by the Children’s Heart Federation. A multidisciplinary group, with patient and carer involvement, then ranked and selected nine key morbidities informed by clinical views on definitions and feasibility of routine monitoring. We validated a new, nurse-administered early warning tool for assessing preoperative and postoperative child development, called the brief developmental assessment, by testing this among 1200 children. We measured morbidity incidence in 3090 consecutive surgical admissions over 21 months and explored risk factors for morbidity. We measured the impact of morbidities on quality of life, clinical burden and costs to the NHS and families over 6 months in 666 children, 340 (51%) of whom had at least one morbidity. We developed and piloted methods suitable for routine monitoring of morbidity by centres and co-developed new patient information about morbidities with parents and user groups.

Results

Families and clinicians prioritised overlapping but also different morbidities, leading to a final list of acute neurological event, unplanned reoperation, feeding problems, renal replacement therapy, major adverse events, extracorporeal life support, necrotising enterocolitis, surgical infection and prolonged pleural effusion. The brief developmental assessment was valid in children aged between 4 months and 5 years, but not in the youngest babies or 5- to 17-year-olds. A total of 2415 (78.2%) procedures had no measured morbidity. There was a higher risk of morbidity in neonates, complex congenital heart disease, increased preoperative severity of illness and with prolonged bypass. Patients with any morbidity had a 6-month survival of 81.5% compared with 99.1% with no morbidity. Patients with any morbidity scored 5.2 points lower on their total quality of life score at 6 weeks, but this difference had narrowed by 6 months. Morbidity led to fewer days at home by 6 months and higher costs. Extracorporeal life support patients had the lowest days at home (median: 43 days out of 183 days) and highest costs (£71,051 higher than no morbidity).

Limitations

Monitoring of morbidity is more complex than mortality, and hence this requires resources and clinician buy-in.

Conclusions

Evaluation of postoperative morbidity provides important information over and above 30-day survival and should become the focus of audit and quality improvement.

Future work

National audit of morbidities has been initiated. Further research is needed to understand the implications of feeding problems and renal failure and to evaluate the brief developmental assessment.

Funding

This project was funded by the NIHR Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 8, No. 30. See the NIHR Journals Library website for further project information.

Anatomical Studies of Transposition - An Argument for a Unifying Morphological Classification

In the setting of transposition, recognition of the variability in the morphology of the outflow tracts and the arterial trunks is essential for surgical repair. Presence of a unifying system for classification would minimize the risk of misunderstanding. We examined an archive of 142 unrepaired hearts with transposition, defined as the combination of concordant atrioventricular and discordant ventriculoarterial connections, combined with the clinical records of 727 patients undergoing the arterial switch procedures. In the setting of usual atrial arrangement, we found the aortic root in leftward or posterior location in up to 5% of our cohorts, making the common term "d-transposition" ambiguous. Variability in the relationship of the trunks was commoner in the setting of deficient ventricular septation, especially when the trunks were side-by-side (14% vs 5.5% when the ventricular septum was intact). Bilateral infundibulums were present in 14% of cases, and bilaterally deficient infundibulums in 3.5%. Both of these findings were more common with deficient ventricular septation. Fibrous continuity between the tricuspid and pulmonary valves was not always seen with perimembranous defects, particularly when there were bilateral infundibulums. Fibrous continuity between the leaflets of the tricuspid and mitral valves, in contrast, proved a unifying characteristic of the perimembranous defect. The combination of concordant atrioventricular and discordant ventriculoarterial connections is best described simply as "transposition," with precision provided when details are given of atrial arrangement and the relationships of the arterial trunks.

What are the important morbidities associated with paediatric cardiac surgery? A mixed methods study

OBJECTIVES

Given the current excellent early mortality rates for paediatric cardiac surgery, stakeholders believe that this important safety outcome should be supplemented by a wider range of measures. Our objectives were to prospectively measure the incidence of morbidities following paediatric cardiac surgery and to evaluate their clinical and health-economic impact over 6 months.

DESIGN

The design was a prospective, multicentre, multidisciplinary mixed methods study.

SETTING

The setting was 5 of the 10 paediatric cardiac surgery centres in the UK with 21 months recruitment.

PARTICIPANTS

Included were 3090 paediatric cardiac surgeries, of which 666 patients were recruited to an impact substudy.

RESULTS

Families and clinicians prioritised:Acute neurological event, unplanned re-intervention, feeding problems, renal replacement therapy, major adverse events, extracorporeal life support, necrotising enterocolitis, postsurgical infection and prolonged pleural effusion or chylothorax.Among 3090 consecutive surgeries, there were 675 (21.8%) with at least one of these morbidities. Independent risk factors for morbidity included neonatal age, complex heart disease and prolonged cardiopulmonary bypass (p<0.001). Among patients with morbidity, 6-month survival was 88.2% (95% CI 85.4 to 90.6) compared with 99.3% (95% CI 98.9 to 99.6) with none of the morbidities (p<0.001). The impact substudy in 340 children with morbidity and 326 control children with no morbidity indicated that morbidity-related impairment in quality of life improved between 6 weeks and 6 months. When compared with children with no morbidities, those with morbidity experienced a median of 13 (95% CI 10.2 to 15.8, p<0.001) fewer days at home by 6 months, and an adjusted incremental cost of £21 292 (95% CI £17 694 to £32 423, p<0.001).

CONCLUSIONS

Evaluation of postoperative morbidity is more complicated than measuring early mortality. However, tracking morbidity after paediatric cardiac surgery over 6 months offers stakeholders important data that are of value to parents and will be useful in driving future quality improvement.

Ethnic-specific mortality of infants undergoing congenital heart surgery in England and Wales

PURPOSE

To investigate ethnic differences in mortality for infants with congenital heart defects (CHDs) undergoing cardiac surgery or interventional catheterisation.

DESIGN

Observational study of survival to age 1 year using linked records from routine national paediatric cardiac surgery and intensive care audits. Mortality risk was investigated using multivariable Poisson models with multiple imputation. Predictors included sex, ethnicity, preterm birth, deprivation, comorbidities, prenatal diagnosis, age and weight at surgery, preprocedure deterioration and cardiac diagnosis.

SETTING

All paediatric cardiac surgery centres in England and Wales.

PATIENTS

5350 infants with CHDs born from 2006 to 2009.

MAIN OUTCOME MEASURE

Survival at age 1 year.

RESULTS

Mortality was 83.9 (95% CI 76.3 to 92.1) per 1000 infants, with variation by ethnic group. Compared with those of white ethnicity, infants in British Asian (Indian, Pakistani and Bangladeshi) and 'all other' (Chinese, mixed and other) categories experienced significantly higher mortality by age 1 year (relative risk [RR] 1.52[95% CI 1.19 to 1.95]; 1.62[95% CI 1.20 to 2.20], respectively), specifically during index hospital admission (RR 1.55 [95% CI 1.07 to 2.26]; 1.64 [95% CI 1.05 to 2.57], respectively). Further predictors of mortality included non-cardiac comorbidities, prenatal diagnosis, older age at surgery, preprocedure deterioration and cardiac diagnosis. British Asian infants had higher mortality risk during elective hospital readmission (RR 1.86 [95% CI 1.02 to 3.39]).

CONCLUSIONS

Infants of British Asian and 'all other' non-white ethnicity experienced higher postoperative mortality risk, which was only partly explained by socioeconomic deprivation and access to care. Further investigation of case-mix and timing of risk may provide important insights into potential mechanisms underlying ethnic disparities.

Left Ventricular Re-training: Feasibility and Effectiveness-What Are the Limits?

The concept of 're-training' the morphologic left ventricle (mLV) is based on the crude principle of applying a fixed afterload by means of pulmonary artery banding. The complex physiological, molecular and structural responses to banding are poorly understood, and complicated by the fact that re-training is undertaken in a variety of different morphological settings and age-groups. This article reviews the evidence for re-training in different situations with particular focus on the age at banding and on the best ways to assess suitability for subsequent repair. Particular importance is placed on the role of re-training in congenitally corrected transposition as this is the commonest current indication - looking at better ways to train the mLV, the role of combined pressure and volume loading, and more sophisticated ways of assessing the adequacy of training. Current evidence suggests that age at banding has a fundamental impact on ability to re-train and long-term mLV function with the best results being achieved in infancy and concerns at any attempt beyond 2 years of age.

Late complication of intramural coronary transfer during the arterial switch operation

Intramural coronary arteries remain a major risk factor and technical challenge of the arterial switch operation for transposition of the great arteries. We report a 27-year-old woman who presented with acute coronary syndrome late after arterial switch with a complex coronary pattern (intramural left and right coronary from sinus 2). Computed tomography demonstrated that the pericardial 'saddle bag' used to reconstruct the intramural coronary was compressed between the neoaortic root and the neopulmonary trunk. During surgery, the coronary system was laid open into the neoaorta with patch enlargement, and the patient made an uneventful recovery.

Trends in surgical and catheter interventions for isolated congenital shunt lesions in the UK and Ireland

Objective

To evaluate time trends in the use of catheter and surgical procedures, and associated survival in isolated congenital shunt lesions.

Methods

Nationwide, retrospective observational study of the UK National Congenital Heart Disease Audit database from 2000 to 2016. Patients undergoing surgical or catheter procedures for atrial septal defect (including sinus venosus defect), patent foramen ovale, ventricular septal defect and patent arterial duct were included. Temporal changes in the frequency of procedures, and survival at 30 days and 1 year were determined.

Results

40 911 procedures were performed, 16 604 surgical operations and 24 307 catheter-based interventions. Transcatheter procedures increased over time, overtaking surgical repair in 2003–2004, while the number of operations remained stable. Trends in interventions differed according to defect type and patient age. Catheter closure of atrial septal defects is now more common in children and adults, although surgical interventions have also increased. Patent foramen ovale closure in adults peaked in 2009–2010 before falling significantly since. Surgery remains the mainstay for ventricular septal defect in infants and children. Duct ligation is most common in neonates and infants, while transcatheter intervention is predominant in older children. Excluding duct ligation, survival following surgery was 99.4% and ≈98.7%, and following catheter interventions was 99.7% and ≈99.2%, at 30 days and 1 year, respectively.

Conclusions

Trends in catheter and surgical techniques for isolated congenital shunt lesions plot the evolution of the specialty over the last 16 years, reflecting changes in clinical guidelines, technology, expertise and reimbursement, with distinct patterns according to lesion and patient age.

Exploring communication between parents and clinical teams following children's heart surgery: a survey in the UK

OBJECTIVE

To explore communication between clinicians and families of children undergoing heart surgery.

DESIGN

This study was part of a larger study to select, define and measure the incidence of postoperative complications in children undergoing heart surgery. Parents of children recruited to a substudy between October 2015 and December 2017 were asked to complete a questionnaire about communication during their child's inpatient stay. We explored all responses and then disaggregated by the following patient characteristics: presence of a complication, length of stay, hospital site, ethnicity and child's age. This was a descriptive study only.

SETTING

Four UK specialist hospitals.

RESULTS

We recruited 585 children to the substudy with 385 responses (response rate 66%).81% of parents reported that new members of staff always introduced themselves (18% sometimes, 1% no). Almost all parents said they were encouraged to be involved in decision-making, but often only to some extent (59% 'yes, definitely'; 37% 'to some extent'). Almost two-thirds of parents said they were told different things by different people which left them feeling confused (10% 'a lot'; 53% 'sometimes'). Two-thirds (66%) reported that staff were definitely aware of their child's medical history (31% 'to some extent'). 90% said the operation was definitely explained to them (9% 'to some extent') and 79% that they were definitely told what to do if they were worried after discharge (17% 'to some extent').Parents of children with a complication tended to give less positive responses for involvement in decision-making, consistent communication and staff awareness of their child's medical history. Parents whose children had longer stays in hospital tended to report lower levels of consistent communication and involvement in decision-making.

CONCLUSIONS

Our results emphasise the need for consistent communication with families, particularly where complications arise or for children who have longer stays in the hospital.

Acceptability of a parental early warning tool for parents of infants with complex congenital heart disease: a qualitative feasibility study

AIM

To explore the acceptability and feasibility of a parental early warning tool, called the Congenital Heart Assessment Tool (CHAT), for parents going home with their infant between first and second stage of surgery for complex congenital heart disease.

BACKGROUND

Home monitoring programmes were developed to aid early recognition of deterioration in fragile infants between first and second surgical stage. However, this necessitates good discharge preparation to enable parents to develop appropriate knowledge and understanding of signs of deterioration to look for and who to contact.

DESIGN

This was a longitudinal qualitative feasibility study, within a constructivist paradigm. Parents were taught how to use the CHAT before taking their infant home and asked to participate in semistructured interviews at four time points: before discharge (T0), 2 weeks after discharge (T1), 8 weeks after discharge (T2) and after stage 2 surgery (T3). Interviews were transcribed verbatim and thematically analysed.

SETTING

One tertiary children's cardiac centre in the UK.

SUBJECTS

Twelve parents of eight infants who were discharged following first stage cardiac surgery for complex congenital heart disease, between August 2013 and February 2015.

RESULTS

Four main themes emerged: (1) parental preparation and vigilance, (2) usability, (3) mastery, and (4) reassurance and support.

CONCLUSIONS

The study highlighted the benefit of appropriately preparing parents before discharge, using the CHAT, to enable identification of normal infant behaviour and to detect signs of clinical deterioration. The study also demonstrated the importance of providing parents with information about when and who to call for management advice and support.

Randomized controlled trials in children's heart surgery in the 21st century: a systematic review

OBJECTIVES

Randomized controlled trials are the gold standard for evaluating health care interventions, yet are uncommon in children's heart surgery. We conducted a systematic review of clinical trials in paediatric cardiac surgery to evaluate the scope and quality of the current international literature.

METHODS

We searched MEDLINE, CENTRAL and LILACS, and manually screened retrieved references and systematic reviews to identify all randomized controlled trials reporting the effect of any intervention on the conduct or outcomes of heart surgery in children published in any language since January 2000; secondary publications and those reporting inseparable adult data were excluded. Two reviewers independently screened studies for eligibility and extracted data; the Cochrane Risk of Bias tool was used to assess for potential biases.

RESULTS

We identified 333 trials from 34 countries randomizing 23 902 children. Most were early phase (313, 94.0%), recruiting few patients (median 45, interquartile range 28-82), and only 11 (3.3%) directly evaluated a surgical intervention. One hundred and nine (32.7%) trials calculated a sample size, 52 (15.6%) reported a CONSORT diagram, 51 (15.3%) were publicly registered and 25 (7.5%) had a Data Monitoring Committee. The overall risk of bias was low in 22 (6.6%), high in 69 (20.7%) and unclear in 242 (72.7%).

CONCLUSIONS

The recent literature in children's heart surgery contains few late-phase clinical trials. Most trials did not conform to the accepted standards of reporting, and the overall risk of bias was low in few studies. There is a need for high-quality, multicentre clinical trials to provide a robust evidence base for contemporary paediatric cardiac surgical practice.

Approaches to Pulmonary Atresia With Major Aortopulmonary Collateral Arteries

Pulmonary atresia with major aortopulmonary collateral arteries (MAPCAs) is one of the most challenging surgical conditions to manage-not only because of the technical complexity of the surgery but also in terms of defining the anatomy of the pulmonary vasculature, the timing of surgery, and decision making on staged vs complete repair. The importance of early definition of pulmonary blood supply is paramount, establishing which areas of the lung are supplied by MAPCAs alone and which have dual supply with the native system (noting that 20% of patients have absent intrapericardial native vessels). Early unifocalization (3-6 months) is ideal, with closure of the ventricular septal defect (VSD) performed if 15 or more out of 20 lung segments can be recruited. Leaving the ventricular septal defect open with a limiting right ventricle-pulmonary artery conduit can be a useful interim or even definitive circulation in patients with borderline vasculature. Rehabilitation of small native vessels with central shunts can be very effective, but best outcomes are achieved by a combination of unifocalization of MAPCAs together with the native vessels (if present). A variety of reconstructive techniques are necessary to be able to effect these complex repairs with careful choice of materials. Ideally, surgery can be completed through sternotomy alone, but separate thoracotomies may be necessary to control and access some MAPCAs.

Re-evaluation of hypoplastic left heart syndrome from a developmental and morphological perspective

Background

Hypoplastic left heart syndrome (HLHS) covers a spectrum of rare congenital anomalies characterised by a non-apex forming left ventricle and stenosis/atresia of the mitral and aortic valves. Despite many studies, the causes of HLHS remain unclear and there are conflicting views regarding the role of flow, valvar or myocardial abnormalities in its pathogenesis, all of which were proposed prior to the description of the second heart field. Our aim was to re-evaluate the patterns of malformation in HLHS in relation to recognised cardiac progenitor populations, with a view to providing aetiologically useful sub-groupings for genomic studies.

Results

We examined 78 hearts previously classified as HLHS, with subtypes based on valve patency, and re-categorised them based on their objective ventricular phenotype. Three distinct subgroups could be identified: slit-like left ventricle (24%); miniaturised left ventricle (6%); and thickened left ventricle with endocardial fibroelastosis (EFE; 70%). Slit-like ventricles were always found in combination with aortic atresia and mitral atresia. Miniaturised left ventricles all had normally formed, though smaller aortic and mitral valves. The remaining group were found to have a range of aortic valve malformations associated with thickened left ventricular walls despite being described as either atresia or stenosis. The degree of myocardial thickening was not correlated to the degree of valvar stenosis. Lineage tracing in mice to investigate the progenitor populations that form the parts of the heart disrupted by HLHS showed that whereas Nkx2–5-Cre labelled myocardial and endothelial cells within the left and right ventricles, Mef2c-AHF-Cre, which labels second heart field-derived cells only, was largely restricted to the endocardium and myocardium of the right ventricle. However, like Nkx2–5-Cre, Mef2c-AHF-Cre lineage cells made a significant contribution to the aortic and mitral valves. In contrast, Wnt1-Cre made a major contribution only to the aortic valve. This suggests that discrete cardiac progenitors might be responsible for the patterns of defects observed in the distinct ventricular sub-groups.

Conclusions

Only the slit-like ventricle grouping was found to map to the current nomenclature: the combination of mitral atresia with aortic atresia. It appears that slit-like and miniature ventricles also form discrete sub-groups. Thus, reclassification of HLHS into subgroups based on ventricular phenotype, might be useful in genetic and developmental studies in investigating the aetiology of this severe malformation syndrome.