The Role of Home Monitoring in Interstage Management of Infants Following the Norwood Procedure

Introduction

Hypoplastic left heart syndrome (HLHS) is a potentially fatal congenital heart abnormality that results in a characteristically underdeveloped left ventricle, ascending aorta, and both mitral and aortic valves. ¹ Despite tremendous advancements in surgical techniques, infants born with HLHS face a significant risk of mortality and morbidity during the staged surgical process, which includes three palliative procedures. ^1,2 The first stage, the Norwood operation, is typically performed soon after birth. ¹ The second stage, the Bidirectional Glenn or hemi-Fontan procedure, is typically performed at four to six months, and the third stage, the Fontan procedure, is performed at 18 to 30 months. The period between the first stage Norwood discharge and stage 2 palliation (S2P), commonly referred to as the “interstage” phase, is associated with mortality rates as high as 10% to 15%. ^3,4 Interstage mortality in the multicenter single ventricle reconstruction trial was 12%. ⁵ The cause of interstage mortality is often difficult to determine. Potential causes of death that have been described include inadequate coronary perfusion, residual or recurrent anatomic lesions, shunt stenosis or thrombosis, low cardiac output, arrhythmia, viral illness, and sepsis. ^{6 –8} In 2003, Ghanayem and colleagues reported that a coordinated home monitoring program (HMP) can lead to a dramatic decrease in interstage mortality. ⁹ Their center showed a decline in mortality from 15% to 0%, following initiation of the program. ⁹ Since then, several other cardiovascular centers across the country have implemented HMPs ^{3,10 –16} In addition, the National Pediatric Cardiology Quality Improvement Collaborative (NPC-QIC) was established by the Joint Council on Congenital Heart Disease and currently represents a collaboration of more than 50 centers that gather and share data on interstage practices with the goal of reducing interstage mortality and improving quality of life and outcomes in this patient population. ^17,18 An important strategy advocated by the NPC-QIC is interstage home surveillance or HMPs, resulting in more widespread initiation of HMPs across the country. The purpose of this review is to describe potential risk factors or causes of interstage mortality and the role of home monitoring in early detection and potential prevention of adverse outcomes.

A search of electronic databases (Medline and PubMed Central) from 2003 to present utilizing the search terms “Norwood home monitoring,” “Norwood home surveillance,” and “interstage home monitoring” identified 11 studies from 8 sites reporting outcomes, including interstage “red flag” events, hospitalizations, interventions, and/or mortality in infants with single ventricle discharged with home monitoring. Five studies/sites included patients with single ventricle who had undergone Stage 1 palliation with a non-Norwood strategy (hybrid procedure and systemic pulmonary shunt). Program components and outcomes are summarized in Table 1. Two studies focused on growth outcomes associated with home monitoring. In addition, 10 articles were identified including 2 review articles and 8 articles on post-Norwood management strategies and/or outcomes, which contained no/inadequate information regarding outcomes specific to home monitoring.

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Table 1.

Interstage Events and Outcomes in Patients With Home Monitoring Following the Norwood Procedure.

Study Program components		Events/readmissions			Interventions		Mortality
	HMP, n	# of patients with events	# of patients readmitted (# of admissions)	Red flags (# of patients)	# of patients (# of interventions)	Types of interventions	HMP% (pre/no HMP)
Rudd et al, 10 2014 (Norwoods only) – Daily weights and O2 saturation – Weekly telephone contact, dedicated interstage clinic (added in 2004) – Red flags: O2 saturation <75%, any weight loss of 30 g, failure to gain 20 g over three days. Also, O2 saturation >90% and enteral intake <100 cm3/kg/d (added in 2005) Ghanayem et al, 9 2004—previous report at same program Ghanayem et al, 4 2002—previous report at the same program	157	93	90 (137)	Low O2 saturation (69), weight gain/loss (38), both (8)	(127)	Supportive care (110), remained inpatient to S2P (31), cardiac catheterization (17) with intervention (8), remained inpatient to S2P (6)	2% (15.5%)
Knirsch et al, 16 2014 (included hybrids) – Daily weights and O2 saturation – Red flags: O2 saturation <70% or >85% or as defined individually by the pediatric cardiologist, weight loss >50 g within two days, weight gain <20 g or >150 g for two consecutive days – Clinic visits every two weeks with cardiologist	14	7	7	Low O2 saturation (6), congestive heart failure (4), weight gain (1)	6	Cardiac catheterization (6), earlier S2P (3), stent surgery (2)	7.1%
Siehr et al, 11 2014 (Norwoods only) – Daily weight, heart rate, enteral intake, and O2 saturation – Weekly telephone contact – Red flags: O2 saturation <75%, weight loss of ≥30 g over two to three day span, lack of a 10-20 g weight gain over three day, respiratory distress or fussiness	46	–	19 (27)	Low O2 saturation (15), growth failure (6), other (6)	17	Major interventions (8), cardiac catheterization (4), early surgery or shunt (4), IV therapy (8), supplemental oxygen (3), feeding adjustment (2)	0% (7%)
Hansen et al, 3 2012 (Norwoods only) – “Rooming in” prior to discharge Daily weight, O2 saturation, heart and respiratory rates – Weekly telephone contact – Red flags: O2 saturation <75%, weight gain <20-30 g in three days, weight loss > 30 g in a day Furck, 32 2010—previous report at the same program	45	14	13	Low O2 saturation (7), poor weight gain (2), both (4)	8	Cardiac catheterization (8), earlier S2P (6), shunt replacement (2)	2.2% (12.4%)
Miller-Tate et al, 15 2013 (hybrids only) – Daily weights and O2 saturation – Weekly phone contact – Red flags: O2 saturation <75%, weight gain <0.02 kg over three days, total formula intake <100 mL/kg/d, loss of 0.03 kg over three-day span Husain et al, 19 2012 [Abstract]—previous report at the same program	24	15	8	–	–	–	21% (26%)
Öhman et al, 13 2013 (included non-Norwood shunt dependent lesions) – Daily O2 saturation – Outpatient visits at local hospital every two weeks – Red flags: O2 saturation <70%	28	7	–	–	5	Shunt replacement (1), balloon dilatation (2), earlier S2P (1), LMWH (1)	14% (10%)
Dobrolet et al, 14 2011 (included non-Norwood shunt dependent lesions) – Daily weights and O2 saturation – Telephone contact every other week – Visit one month postdischarge at high-risk clinic	59	–	–	–	–	–	3% (6%)
Petit et al, 12 2011 (included non-Norwood single ventricle lesions) – Daily weight and O2 saturation – Weekly phone contact – Dedicated single ventricle clinic – Weekly meetings of single ventricle team. – Red flags: O2 saturation <75%, failure to gain weight on at least three successive days	88	–	–	–	–	–	8% (12%)

Abbreviations: HMP, home monitoring program; O₂, oxygen; S2P, stage 2 palliation; LMWH, low-molecular-weight heparin; IV, intravenous.

Interstage Events

Following a successful Norwood procedure, infants with HLHS still remain at risk for acute hemodynamic decompensation during the interstage period. ²⁰ The fragility intrinsic to the post-Norwood circulation leaves infants susceptible to various morbidities that can occur between the first and second surgeries. As reported by Hanke and colleagues, 55% of post-Norwood infants have at least one readmission during the interstage period. ²¹ Among the centers that have implemented HMPs and published data on their impact, most have reported complications and subsequent readmissions that involve hypoxemia and/or growth failure, potential manifestations of increased cardiovascular risk (Table 1). Specifically, hypoxemia was listed as the most common reason for readmission followed by poor weight gain or feeding problems. ^{3,9 –11,16}

Role of Home Monitoring

Home monitoring programs are based on the theory that recognizing signs such as worsening oxygen saturation from baseline or poor weight gain/acute weight loss can foretell serious anatomic lesions or a developing illness, which would then allow for a potentially lifesaving intervention (Figure 1). ²² Home monitoring program participants are provided with the equipment and resources needed to both identify signs of distress and decide on an appropriate action plan. All HMPs reviewed (Table 1) discharged patients with a pulse oximeter that enables parents to track their infant’s daily oxygen saturation levels at home. Parents receive guidance on how to use equipment as well as education on the importance of changes in oxygen saturations and respiratory status. ³ In addition, parents are counseled on who to contact (eg, HMP team and local cardiologist) when saturation levels fluctuate significantly from baseline. Generally, parents are instructed to call the HMP team immediately upon witnessing any respiratory or desaturation-related issues and the action taken by the team varies depending on the severity of symptoms observed.

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Figure 1.

Identification of infants at risk during the interstage period.

Similarly, of the identified care centers participating in some form of HMP, most (seven of eight sites) send parents home with a scale that is used for weight measurements typically done daily to monitor their child’s growth. ³⁵ Typically, if the infant’s weight changes are below the identified parameters, the family contacts the nursing team, a dietician, or a pediatric cardiologist who can then create an action plan that may include adjustments to the feeding plan (eg, increased caloric concentration) or other nutritional intervention or may prompt further evaluation by the medical team. Thus, the monitoring of weight by both parents at home and trained staff at the cardiac center facilitates the detection of deteriorating health including dehydration and enables interventions that can help promote weight gain and prevent growth failure.

Home monitoring program participants are also discharged with a list of reportable signs or “red flag” events to look out for that relate to the compromise of the infant’s cardiopulmonary or nutritional status (Table 1 and Figure 1). These red flags typically include decreasing oxygen saturation (especially below 70%-75%), signs of cyanosis, weight loss, increased work of breathing, fussiness, and other signs of respiratory distress. Home monitoring of oxygen saturations has been shown to be effective in the detection of life threatening shunt occlusions particularly when the thrombosis/stenosis develops gradually. ¹³ In addition, anemia, respiratory illness, and myocardial dysfunction with a fall in cardiac output can manifest as a desaturation from baseline. ^4,9 Similarly, red flags enable caregivers to identify weight loss, insufficient weight gain, feeding issues, decreased intake, and vomiting. Most parents are asked to record daily weights and/or volume consumption, and fluctuations that fall below specified criteria are “flagged” and reported to either the HMP team or a local physician. The goal weight gain is 20 to 30 g/d. ³⁰ Red flags generally include weight loss greater than 30 g/d, failure to gain at least 20 to 30 g over three days, and an intake of less than 100 mL/kg/d. ³⁰ Interstage infants often require numerous unscheduled clinic visits and readmissions to address the morbidities that arise following discharge, ¹³ often prompted by parental detection of red flags.

In addition to weight gain and oxygen monitoring, many HMP programs provide access to skilled staff members that offer additional surveillance during this time. Many HMPs provide families with access to a dietician who can provide expertise if and when an infant fails to grow on their correct trajectory. Even in the absence of a red flag, weekly check-ins with a dietician provide another layer of observation to ensure the infant is on track toward normal growth. Anderson and colleagues showed that “layers” such as these work synergistically in improving growth during the interstage phase by demonstrating greater weight gained in patients who had multiple aspects of the HMP (scales, red flags, phone contact, and feeding evaluations). ³⁶ A report from the NPC-QIC found fewer clinic visits with the primary cardiologist identified was associated with increased mortality risk. ³⁷ Complete information regarding the frequency of phone or in-person contact with the HMP team, including the availability of a dedicated, multidisciplinary interstage clinic, was not available for all HMPs reviewed, but these additional supports may further contribute to improved outcomes.

Efficacy and Future Directions of HMPs

Home monitoring programs represent an organized, coordinated approach that requires the vigilance of the cardiac care center, local cardiologist, and caregivers. Data from centers with HMPs indicate that they can be extremely successful in reducing mortality, with mortality as low as 3% or less reported in some centers. ^3,9,10,11,14 Interestingly, in a study by Hansen and colleagues, which demonstrated a reduction in mortality from 12.4% to 2.2%, the only post-HMP interstage death involved an infant of noncompliant participants. ³ In addition, many centers report that infants required a major or minor medical intervention (eg, early S2P and shunt replacement) during readmission, emphasizing the significance of the complications identified through HMP. ^{3,10,11,13,16} Siehr and colleagues noted that the percentage of infants in their cohort requiring major interventions (ie, surgery or an unscheduled interventional catheterization) was extremely close to previously reported interstage mortality rates indicating that these interventions may possibly represent “near-miss deaths.” ¹¹ Petit and colleagues found that despite close outpatient follow-up and home monitoring, interstage mortality in their cohort of infants with single ventricle was not significantly reduced but decreased from 12% to 8% and weight gain significantly improved. ¹² Similarly, Husain and colleagues showed only a slight mortality reduction from 24% to 21% in patients with single ventricle following the hybrid procedure. ¹⁹ As the hybrid procedure may be the intervention of choice for patients at higher risk for the standard Norwood operation, inclusion of this high-risk group may account for the higher mortality observed despite HMP. Other variations in practice and programmatic changes such as earlier catheterization and S2P and/or hospitalization of “high-risk” patients throughout the interstage period or following a readmission may have also contributed to differences in interstage survival outcomes. ^{3,10 –12,16} Srinivasan and colleagues found a multifaceted, standardized approach, which included an HMP, was associated with better survival to S2P. ³⁸

In addition to improved survival, numerous centers have published reports demonstrating an increase in weight gain of infants participating in a home surveillance program relative to a historical group. ^4,12,15,33 Petit and colleagues experienced an improvement of average daily weight gain in interstage infants from 17.9 to 22.5 g/d after the initiation of their HMP. ¹² Hehir and colleagues noted that interstage growth paralleled normal infant growth with a growth velocity of 26 ± 8 g/d. ³³ Similarly, a review of nutrition practices among sites participating in the NPC-QIC registry by Anderson and colleagues showed that those centers who closely monitored specific weight gain/loss red flags during the interstage period subsequently had better patient growth. ³⁶

Future directions of the HMP may involve research to improve communication with participants in remote areas using new innovative technology, identification and sharing of best practices, and potential expansion of the HMP model to other congenital disease populations. ^26,39 McCrossan and colleagues demonstrated that a telemedicine home support program for infants with major CHD, particularly those involving video-conferencing support, was well received by both clinicians and parents and may reduce health service utilization and costs. ³⁹ In addition, as more centers continue to collect and report data from their respective programs, the sharing of best practices can be facilitated by organizations such as the NPC-QIC, allowing for further refinement of the components of a successful HMP and identification of other practices associated with improved outcomes. ²⁶

The HMP is a multidisciplinary care model that requires compliance, patience, equipment, and significant effort on the part of the participants and health care providers involved. ¹¹ Caregivers must be educated on how to recognize the key signs of distress and enabled to contact their primary cardiologist or the surgical site when such disturbances occur. ¹⁴ Home monitoring programs have the potential to reduce interstage mortality and morbidity by allowing for the early detection of potentially life-threatening anatomic or physiologic abnormalities in this vulnerable infant population. Although lack of equipoise precludes conduct of a randomized controlled trial, future collaborative studies that allow further elucidation of best practices at high-performing centers may further improve outcomes.