Discussion

We report our experience using the KidsHeart mHealth app to monitor for high-risk “red flag” violations, to track feeding and growth, and to evaluate longitudinal outcomes. In this pilot analysis, patient engagement was good with most patients submitting daily red flag scores and daily weights/feeding data. More than half of all interstage interventions were precipitated by an app-generated red flag notification. In addition, we remotely tracked interstage weight gain and intervened with app-precipitated feeding and nutrition changes in more than a third of all enrolled participants. Finally, mHealth proved a useful means for tracking longitudinal post-discharge outcomes such as neurodevelopmental scores.

Mobile health improves both access to care and quality of care ^{Reference Borges do Nascimento, Abdulazeem and Vasanthan2} and has been shown to offer clinical impact across multiple populations. ^{Reference Borges do Nascimento, Abdulazeem and Vasanthan2,Reference Alhussein and Hadjileontiadis11–Reference Webb, Joseph, Yardley and Michie17} MHealth may be especially valuable for rare diseases and conditions, such as children with CHDs, where care is primarily delivered at regional referral centres. An estimated 25% of CHD patients live >100 miles from their surgical centre. ^{Reference Welke, Pasquali and Lin18} Although more intensive monitoring improves outcomes in these patients, ^{Reference Rudd, Ghanayem and Hill7} geographic isolation can be a major impediment. In other paediatric patient populations with complex medical needs, mHealth improves caregiver involvement and our experiences were similar with 100% of enrolled subjects submitting post-discharge data via the app. ^{Reference Bird, Li, Ouellette, Hopkins, McGillion and Carter19}

Our data add to a growing body of pilot data demonstrating the value of mHealth technology for interstage monitoring in children with single ventricle heart disease. ^{Reference Blair, Vergales, Peregoy, Seegal and Keim‐Malpass20–Reference Kauw, Koole and van Dorth23} The interstage period represents the time between the first and second stage of single ventricle surgical palliation. During this high-risk period, intensive surveillance monitoring significantly decreases the incidence of interstage mortality and other poor outcomes. ^{Reference Anderson, Beekman and Kugler24–Reference Staehler, Schaeffer and Wasner29} Our work expands this literature by performing interstage monitoring digitally as well as the addition of longitudinal remote neurodevelopmental tracking. Although we did not rely solely on mHealth interstage monitoring and continued our standard interstage monitoring programmes, over half of our interstage interventions were precipitated by an mHealth alert. These interventions included 34 hospital admissions with 15 of these leading to trans-catheter evaluation. These interventions’ clinical acuity suggests that our mHealth monitoring is not simply leading to increased detection of non-significant concerns. Our red flag monitoring checklist was custom designed for the KidsHeart app. While prior interstage monitoring studies have provided reasons to contact the medical team ^{Reference Hartman, Ebenroth and Farrell22} or a list of action plans, ^{Reference Anderson, Beekman and Kugler24} our red flag daily questionnaires automated the process to facilitate prompt intervention with an associated severity score. Our data validates the checklist with higher scores associated with higher acuity interventions.

Optimal feeding and growth are similarly important during the interstage period in patients with CHD. A meta-analysis including >1,400 pre-stage II single ventricle patients showed, on average, reduction of >1 z-score in both and weight during the interstage period. ^{Reference Van den Eynde, Bartelse and Rijnberg30} Growth concerns adversely impact both neurodevelopment and surgical outcomes, ^{Reference Williams, Zak and Ravishankar31} and the Joint Council on Congenital Heart Disease Quality Improvement Task Force highlighted optimising nutritional status as a key target for high-risk neonates. ^{Reference Kugler, Beekman Iii and Rosenthal32} In our pilot data, weight trajectory was measured reliably compared to EMR-documented growth but with more frequent monitoring, more data points, and automated notifications when weight gain is not meeting goals (20–30 g per day). This allows earlier intervention with more than one third of our patient population receiving feeding adjustments following an app notification. It also allowed for closer weight and feeding monitoring during the formula shortage.

Finally, our pilot data demonstrate a proof of principle that mHealth can function as a useful means for tracking longitudinal post-discharge outcomes. This is an unmet need in CHD care which has historically relied on robust in-patient registries yet lacks data on the longer-term post-discharge outcomes that matter most to families. In our analysis, 100% of KidsHeart app study participants submitted post-discharge data, thereby verifying vital status and providing information on important longitudinal outcomes such as growth and neurodevelopment. Our KidsHeart app incorporates a unique patient identifier that, in theory, can be used to link back to existing registry data, thereby providing a rich data source for longitudinal outcomes analyses.

There are important limitations to this analysis. As a pilot study, the sample size is small and overall duration of app usage relatively low. Our data was not intended to be directly compared to current standard of care but rather to augment existing care models. Moreover, we have limited data on longer-term neurodevelopment and growth outcomes which are needed to accurately validate the utility of mHealth neurodevelopmental surveys and feeding interventions. The KidsHeart app will continue to enrol permitting these analyses to be completed in the future. While mHealth offers an opportunity for equity of access to health resources in remote communities, there are limitations to this as well, including socio-economic barriers that may impact feasibility. ^{Reference Wali, Remtulla Tharani and Balmer-Minnes33}

In conclusion, the KidsHeart app pilot data demonstrates the utility of mHealth in CHD population and augments the clinical benefits of remote monitoring with success in red flag monitoring and subsequent implementation of interventions, growth monitoring, and longitudinal outcomes assessment. In terms of future directions, we aim to collect more robust and longer-term neurodevelopmental outcomes and to validate these data with standardised neurodevelopmental assessments. We intend to assess socio-economic barriers to mHealth monitoring and to develop a linkage methodology allowing mHealth longitudinal outcomes to be linked back to existing registry data. Accomplishing these goals will extend the value of mHealth technology by supporting research as well as clinical care.