Introduction
Single ventricle cardiac physiology, as a result of an inadequate right or left ventricle, Reference Rao1 has a reported prevalence of 0.16 per 1000 live births in the United Kingdom. Reference Coats, O’Connor, Wren and O’Sullivan2 In efforts to reduce mortality in the surgical perioperative journey, and improve the quality of life for infants and parents, home monitoring programmes were first introduced as part of a paediatric quality improvement initiative in the United States of America (USA). These programmes focussed on monitoring of oxygen saturations, weight gain and hydration status during the shunt dependent period between stage 1 and stage 2 surgical palliation, commonly referred to as the “interstage period.” Reference Ghanayem, Hoffman and Mussatto5 These programmes have generally been accepted to be of benefit in reducing the risk of interstage death. Reference Rudd, Ghanayem and Hill6–Reference Hehir and Ghanayem7 The impact and role of the home monitoring programme in reducing associated growth failure (deemed to be modifiable) has been a more recent focus, with some positive findings for its impact on interstage weight gain. Reference Hehir and Ghanayem7
A 2022 systematic review mapped the growth of single ventricle patients, and identified that the most intense somatic growth faltering, with a fall in z score of>1 for both height and weight, occurred from birth until stage 2 palliation, which encompassed the high-risk interstage period. Reference Van den Eynde, Bartelse and Rijnberg8 Risk factors for growth failure include inadequate caloric intake, increased metabolic demands due to cardiac dysfunction, and gastrointestinal dysfunction, as well as poor feeding and haemodynamic instability. Reference Rudd, Ghanayem and Hill6 In addition, impaired somatic growth has been identified as a risk factor for poor surgical outcomes, Reference Hehir, Cooper, Walters and Ghanayem9 affected neurodevelopment, and increased risk of mortality. Reference Murni, Patmasari and Wirawan10–Reference Trivedi, Carmo, James-Nunez, Jatana and Gordon11
There are ten paediatric cardiac surgical centres in the United Kingdom, and most have developed an individualised approach to a home monitoring service; largely, the service focuses on monitoring oxygen saturations and weight gain, based on the premise of enabling recognition of deterioration and initiating early interventions during the interstage period. Reference Hehir, Rudd and Slicker12 The aim of this retrospective evaluation is to describe the growth of infants with single ventricle physiology when supported by a home monitoring programme in the South of England. To date, the impact of interstage surveillance via the home monitoring programme has not been widely described in the United Kingdom.
Materials and Method
A retrospective review of two epochs of infants with single ventricle physiology—cohort 1: before, and cohort 2: following the implementation of a home monitoring programme—was carried out. Cohort 1 (pre-home monitoring era): March 2013 – March 2017 and cohort 2 (post-home monitoring programme era): April 2017 to January 2023. Those eligible for inclusion were identified via hospital patient records, with inclusion dependent on a single ventricle diagnosis, and dependence on a systemic to pulmonary shunt during the interstage (Fig 1).
Cohort inclusion/exclusion pathway. HMP = Home Monitoring Programme.
The included diagnoses of single ventricle infants were: Hypoplastic left heart syndrome, pulmonary valve atresia, double outlet right ventricle, double inlet left ventricle, tricuspid valve atresia, pulmonary and tricuspid valve atresia and unbalanced atrioventricular septal defect.
Exclusion criteria included: infants currently in the interstage period, infants who were not shunt dependent during the interstage (a pre-requisite for home monitoring enrolment), and infants whose families opted for comfort-focussed care, as opposed to surgical palliation.
The local home monitoring programme enlists multi-disciplinary reviews from clinicians, dietitians, and local services, with a cardiology nurse specialist team leading. Compliance with the centre-specific home monitoring protocol begins prior to discharge, with consensus on suitability of infant for interstage home discharge discussed within the cardiac multi-disciplinary team, following the stage 1 procedure. Successful completion of the protocol checklist is mandatory for discharge, which includes a period of solo caregiving whilst on the ward. Upon discharge, parents receive bi-weekly phone call check-ins and are provided with a hotline number to ring if they have any concerns or hit any “red flag” parameters. Parents are expected to take a daily weight and oxygen saturation and record daily fluid intake. All equipment is provided to parents.
As part of each review, parents report the weight of their infant to a member of the multi-disciplinary team, who records the new weight within the child’s electronic growth chart. This is completed in real time to provide parents with immediate feedback on the child’s growth, including any required changes to the nutrition care plan. Each child will have an acceptable oxygen saturation range and will trigger a “red flag” when outside of this range. “Red flag” weight parameters are triggered if the infant does not gain 20g each day for three days, loses more than 30g in one day, or is feeding less than 100mls/kg/day of fluid. An urgent in-person health assessment by a cardiac specialist and dietitian would then be completed.
Weight and age were identified from electronic patient health records at birth, stage 1 procedure and discharge (where applicable for cohort 1 infants), stage 2 procedure and discharge, and 12–23 months. Secondary variables were collected for the entirety of a cohort to allow for comparison between cohorts and account for confounding variables for growth. These variables included sex, single ventricle diagnosis, age at stage 1 and 2 palliations, procedure type, mean length of paediatric ICU and hospital stays post-procedure, interstage feeding regime, and interstage mortality, defined as death between stage 1 and stage 2 palliation (see Table 1 for complete secondary variables).
Infant characterstics: Cohort 1 and Cohort 2. HMP - Home Monitoring Programme. Both subtypes of Double Outlet Right Ventricle = DORV with noncommitted VSD
World Health Organisation AnthroPlus software version 1.0.4 was used to calculate z-scores for weight. Moderate undernutrition was defined as a z score of < −2. 13 Infants born before <37 weeks gestational age were defined as being preterm with weight-for-age z scores corrected using Intergrowth-21st Preterm Tools. 14 Chi-squared and Fisher’s exact tests were used for cohort comparison of secondary variables. Weight-for-age z scores were compared across time points using an independent sample t-test for each individual cohort. Unpaired t-test was utilised for weight-for-age z-score comparison between cohorts, and multiple linear regression to control for confounding variables in dataset. IBM SPSS Statistics, (Version 29.0.2.0 (2023) Armonk, NY: IBM Corp.) was used for the analysis of this data, with statistical significance defined as a p-value of<0.05.
Results
Infant characteristics
Demographic characteristics were collected for all infants in cohort 1 and cohort 2 (Table 1). Hypoplastic left heart syndrome was the most common single-ventricle diagnosis, occuring in 59.3% (n = 16/27) of cohort 1 and 50% (n = 15/30) of cohort 2, with no significant differences in the prevalence of diagnosis between cohorts. For both cohorts, the Norwood with Sano modification was the most common procedure for stage 1, and Bidirectional Glenn for stage 2. The introduction of the patent ductus arteriosus stent as a stage 1 procedure from 2017 onwards for seven infants was responsible for the significant difference in procedure types between cohorts (p < 0.05).
Number of infants discharged home
In cohort 1, 38% (n = 10/26) infants were discharged home with outpatient medical follow up during the interstage in the pre-home monitoring programme era, compared to cohort 2, where 75% (n = 21/28) discharged home in the home monitoring programme era (p < 0.05). Five additional infants in cohort 2 were also initially transferred to a local hospital and were also discharged onto a home monitoring programme, resulting in 93% (n = 26/28) infants being discharged home.
Single ventricle infant growth
Weight-for-age z-score initially faltered in both cohorts when compared to birthweight (Table 2). The peak fall in weight-for-age z-score for both cohorts was at stage 1 discharge. Cohort 1 had the largest deceleration and crossing down of centile lines. Weight-for-age z-scores started to recover subsequent to stage 1 discharge. Cohort 1 did not reach its baseline weight-for-age z-score by 12–23 months. In cohort 2, weight-for-age z score is higher at 12–23 months than at birthweight: 0.18 ± 1.63 indicating achievement of catch-up growth.
Cohort comparison, change in mean WAZ score. Cohort 1: pre-home monitoring programme. Cohort 2: home monitoring programme enrolment. *Significant falter from baseline WAZ, p < 0.05. ∼ only discharged infants contribute to this data point. WAZ = weight-for-age z-score
Pre-home monitoring versus home monitoring
Both cohorts of infants with single ventricle physiology experienced weight faltering post-birth. Fig 2 shows decelerations and accelerations in weight-for-age across the surgical journey. Comparison of weight changes between the cohort 1 and cohort 2 showed no statistically significant differences. Interstage growth velocity, calculated as [ (S2P weight – S1P discharge weight)/(age at S2P – age at S1P discharge)], was 23.98 ± 11.7 g/day in the pre-home monitoring cohort (n = 17) and 23.82 ± 8.3 g/day in the home monitoring cohort (n = 21) (p = 0.964).
Mean cohort weight-for-age z-score changes compared to initial birth weight.
Although cohorts had comparable growth velocity during the interstage, cohort 2 infants maintained growth velocity closer to original centile line. This weight consistency contributed to the finding that only cohort 2 achieved catch-up growth at 12–23 months.
Nasogastric feeding and growth
Within the pre-home monitoring cohort, 10 infants had a feeding regime that included nasogastric feeding (38%) during the interstage period. In the home monitoring cohort, a total of 13 infants had equivalent nasogastric interventions (46%), p = 0.55.
Linear regression was utilised to adjust for the independent factors of cohort and nasogastric feeding with regard to growth. At stage 1 discharge, once adjusting for cohort, the requirement for an interstage nasogastric tube was associated with a deceleration in growth and fall in weight-for-age z-score of −0.57, 95% CI [−1.14, 0.001] compared to those who did not require one (p=<0.05). At stage 2 palliation, when controlling for these above variables, there was no significant impact on growth. At stage 2 discharge, the presence of a nasogastric feeding tube during the interstage was associated with a reduction in weight-for-age z-score of −0.57, 95% CI [−1.16, 0.018] (p = 0.057). This relationship continues; the presence of a nasogastric tube during the interstage was associated with a significant, persistent fall in weight-for-age z-score of −0.97, 95% CI [−1.75,−0.19](p = 0.17) at 12–23 months.
Mortality
Interstage death, death between stage 1 and stage 2 palliative procedures was 11.1% (n = 3) in the pre-home monitoring cohort, and 13.3% (n = 4) in the home monitoring cohort (Table 1). Mortality at 1 year was also comparable between both cohorts.
Discussion
This retrospective review assesses safety and impact of a home monitoring programme on the growth of infants with single ventricle physiology. The results suggest that enrolment in a home monitoring programme—using oxygen saturation, daily weights, and early nutrition support—significantly increases the number of infants safely discharged to their families during the interstage period. Home monitoring programmes are offered as a standard of care by some paediatric surgical centres in the United Kingdom, during the interstage period for infants with single ventricle physiology. However, evidence on the impact of these programmes with regard to growth, mortality, and quality of life measures for families remains limited. Reference Hehir and Ghanayem7
A key finding, especially given the considerable burden on single ventricle patients and their families, is the significant difference in discharge location for infants during the interstage period, following the introduction of the home monitoring programme. Reference Drury, Stoll, Bond, Patel, Hutchinson and Clift15 The majority of infants with single ventricle physiology were able to be discharged home into the care of their family or caregiver during the interstage period when enrolled on the home monitoring programme, compared to around one-third of infants before its introduction. This shift in discharge location was not associated with a change in interstage mortality. From the families’ perspective, qualitative research involving single ventricle families has shown that medicalisation of caring tasks for these infants whilst in hospital limits parental bonding and impairs parent identity. Reference Mery, Well and Taylor16–Reference Elliott, Erickson, Russell, Chrisman, Toalson and Emerson17 Benefits from the National Health Service perspective may include reduction in cost and capacity burden.
In terms of growth from birth, both cohorts had their peak weight faltering at stage 1 discharge, with the pre-home monitoring cohort having a greater degree of faltering than the home-monitoring cohort. Previous research has identified this period as high risk for growth failure, Reference Van den Eynde, Bartelse and Rijnberg8–Reference Shine, Foyle, Gentles, Ward and McMahon18 associated with adverse outcomes in the single ventricle population. Reference Gardner, Mercer-Rosa and Faerber19 However, the present findings suggest that the severity of weight faltering from birth to stage one discharge is modifiable, as the home monitoring cohort had a reduction in this falter compared to prior to its implementation. This finding, however, cannot be attributed to the home monitoring programme, given infants were yet to be enrolled; these improvements could reflect wider centre advancement, including the impact of a pre-surgical nutrition pathway implemented across a similar time frame. The nutrition pathway sought to support normal growth in the context of greater demand for infants with a range of CHD diagnoses, not solely single ventricle physiology. Pathway evaluations have shown improved growth outcomes following this implementation.
The results show that the home monitoring cohort was the only group to surpass their initial birthweight growth centile and that growth was surpassed at 12–23 months. This suggests that infants were able to achieve catch-up growth after their first two surgical interventions when enrolled on the home monitoring programme, compared to before its introduction. Further work is required to understand whether accelerated weight gain during the first two years of life increases the risk of overweight and obesity later in childhood in this vulnerable cohort of children, or whether it supports improved linear growth outcomes over time. Reference Aguilar, Raff, Tancredi and Griffin20-Reference Marino, Johnson and Davies22
When focusing on growth solely during the interstage period, irrespective of prior growth falter, the mean growth velocity of each cohort is almost identical. Interstage growth velocity was within the considered normal daily weight gain of 20 to 30g/day for this age group. Reference Hehir, Rudd and Slicker12 The home monitoring cohort observed fewer extreme values for interstage growth velocity and maintained growth velocity on a centile closer to original birthweight.
Interstage feeding modalities between the cohorts were comparable. Interpretation of the impact of nasogastric feeding regimens on infant growth is challenging, given that poor weight gain would be an indicator for the placement of a feeding tube; and not achieving sufficient oral intake and growth may be markers of more severe illness. Reference Hill, Hehir and Bartz23 A nasogastric interstage feeding regime at stage 1 discharge was associated with a more significant growth falter. This likely identifies that we are correctly intervening in feeding regimes. Positively, this falter did not persist at stage 2 palliation, which suggests a nasogastric regime improved growth during the interstage, consistent with findings in larger studies. Reference Hill, Hehir and Bartz23–Reference Medoff-Cooper, Irving and Marino24 An important finding when looking at the growth of these infants at 12–23 months was that those who had a nasogastric feeding tube during the interstage remained significantly faltered in their growth compared to their counterparts. This suggests that the need for an interstage nasogastric tube is a positive predictor of poor growth, which persists to 23 months of age.
This review adds to the literature describing United Kingdom home monitoring programmes, and contributes to transparency in care nationally.
Limitations
This was a single-centre service evaluation, so the results identified may not be generalisable to all home monitoring programmes, especially given the heterogeneity in the setup of services. For example, interstage shunt dependence is a pre-requisite for enrolment in this home monitoring programme. The two cohorts (pre-home monitoring versus home monitoring) were treated across different timeframes, no control group could be identified for this evaluation due to a universal change in practice.
As this was a retrospective review, limitations surrounding missing data and the quality of data available impacted the conclusions drawn; in terms of growth data handling the entirety of the pre-home monitoring cohort were analysed; however, the growth data for stage 1 discharge only reflects those in the cohort who was discharged, as a pre-requisite for completion of data point. The analysis aimed to maximise data points that could be included, with the dataset impacted by missing data, but recognises that infants who were not discharged during the interstage may have been at higher risk of morbidity and mortality impacting on growth observed at this stage. As the growth of the pre-home monitoring cohort was compared to the growth of those only enrolled on the home monitoring programme, this limits the validity of the comparison that can be made across the cohorts.
Identification of the single ventricle cohort was reliant on the correct coding of the individual in the paediatric cardiac database. Growth analyses were reliant on the availability of this retrospective data. Due to insufficient data points available on height, these were excluded from the final analysis.
Conclusion
The introduction of a home monitoring programme enabled a significant increase in the number of infants who were safely able to be discharged home to caregivers during the interstage period. Infants enrolled on the home monitoring programme did not have any worse outcomes and achieved catch-up growth at 12–23 months. Interstage nasogastric feeding remains a positive predictor of poor growth at 23 months of age.
Acknowledgements
We would like to acknowledge the specialist cardiac nurses for their input and insight into the workings of the home monitoring programme. In addition, Research Dietitian Catarina Fandinga, and Mr Antoinio Ravaglioli, Paediatric and Adult congenital cardiac surgery for their assistance with the project.
Financial support
MJJ’s salary is support by the National Institue for Health and Care Research, Biomedical Research Centre Southampton. LM is supported by Southampton Academy of Research Leaders programme, University Hospital Southampton NHS Foundation Trust.
Competing interests
None.
Ethical Standard
The home monitoring programme for infants with single ventricle cardiac physiology was applied to all infants who met the criteria as part of a change in practice brought about by a National Health Service Commissioning for Quality and Innovation in 2017. It was therefore the study of a clinical practice change using clinical audit as part of a service evaluation and not an interventional study, with no ethical approval required.
Growth data were collected as part of a registered service evaluation of the new practice. Opinion regarding ethical review was sought from a local ethics committee regarding the use of growth data and felt to be unnecessary in the context of service evaluation. The project was registered on University Hospital Southampton NHS Foundation Trust clinical governance system Ulysess as a service evaluation [Number 7784].
Open access
