Introduction
Hypoplastic Left Heart Syndrome occurs in approximately 2.6 of every 10,000 live births in the United States. Reference Mai, Isenburg and Canfield1 While risk of early mortality remains high in this complex condition, improvements in medical and surgical care have resulted in improved survival over recent decades. Reference Siffel, Riehle-Colarusso, Oster and Correa2 The current classical three-stage palliation approach, leading to a total cavopulmonary connection (Fontan), results in significant circulatory derangements. Known long-term complications and risks for these patients include risk for arrythmias, liver disfunction, thromboembolism, and heart failure. Reference Pundi, Johnson and Dearani3–Reference Egbe, Connolly and Khan6 All patients with Fontan circulation including those with Hypoplastic Left Heart Syndrome have a significant burden of hospitalisations particularly in adulthood. Reference Egbe, Khan, Al-Otaibi, Said and Connolly7 The long-term trajectories of this patient population are continuously evolving and continue to encompass significant uncertainty.
While previous reports have looked at trends in hospitalisations of all adults with CHD, the Hypoplastic Left Heart Syndrome population is unique with a different hospitalisation profile compared to the overall adults with CHD population. Reference Well, Mizrahi and Johnson8 This study aims to evaluate hospitalisation characteristics and outcomes of children and adults with Hypoplastic Left Heart Syndrome as well as assess for trends in these characteristics over an 11-year span.
Methods
Data source
Data were obtained from the Texas Inpatient Discharge Dataset from 2009 to 2019. 9 The Texas Inpatient Discharge Dataset is an administrative database that captures most discharges in the state of Texas with exception of hospitals located in a county with a population less than 35,000, or those located in a county with a population more than 35,000 and with fewer than 100 licensed hospital beds and not located in an area that is delineated as an urbanised area by the United States Bureau of the Census. The data are collected and maintained by the Texas Department of State Health Services, Center for Health Statistics. Data are deidentified when it is submitted to the dataset from the hospitals. The Institutional Review Board for the University of Texas at Austin Dell Medical School waived the need for approval of this study as it consisted of existing, deidentified data.
Study population
The Texas Inpatient Discharge Dataset provides an admitting diagnosis, a principle diagnosis, up to 24 other diagnoses, a principle procedure and up to 24 other procedures for each hospitalisation record. From 2009 through the third quarter of 2015, diagnoses and procedures were coded using the standard International Classification of Diseases, 9th edition (ICD-9). Records from the fourth quarter of 2015–2019 were coded using the 10th edition (ICD-10).
Discharges of patients ≥5 years of age at discharge and diagnosis of Hypoplastic Left Heart Syndrome (ICD-9: 746.7, ICD-10: Q23.4) were included. We excluded from analysis; discharges from long-term care, mental and behavior health facilities, substance abuse centers, and unknown center type, discharges with missing information on the type of admission, sex, age, race, ethnicity, length of stay, discharge status, admitting diagnosis, or principle diagnosis, and interim entries. Additionally, discharges with an ICD-9/10 procedure codes consistent with Fontan completion (ICD-9: 39.21, ICD-10: 02160** or 02170**) in those aged 5–9 years were excluded as the focus of the analysis was post-Fontan hospitalisations.
Study outcomes
The primary aim of the study was to assess indications for hospitalisation, procedures performed, and outcomes by age and over time.
The Texas Inpatient Discharge Dataset categorises age into 16 groups. These were further collated into 5–9 years, 10–14 years, 15–19 years, 20–24 years, and 25+ years. Insurance status was grouped into private insurance, Medicare, Medicaid, uninsured, other, and unknown. Admitting and principle diagnoses were grouped into 24 categories for analysis. Procedures were identified by ICD-9 and ICD-10 procedure codes and are listed in Supplemental Table 1. Hospitalisation outcomes included in-hospital mortality and length of stay.
Statistical analysis
Descriptive statistics were reported for demographics, hospitalisation characteristics, and outcomes. Length of stay is reported in median [interquartile range] days. All other variables are presented as proportions. Chi-square and Fisher’s exact test were utilised to analyse discrete variables. Kruskal–Wallis test was utilised to analyse length of stay. Statistical analyses were performed using R and RStudio. 10 All statistical tests were 2-tailed and a p-value < 0.05 was considered significant.
Results
Overall discharges
A total of 1024 eligible discharges were identified. Of these, 402 (39.3%) were of female patients, 777 (75.9%) were white, 395 (38.6%) were Hispanic, 379 (37.0%) had private insurance, and 25 (2.4%) were uninsured. Overall, 504 (49.2%) discharges were of patients between 5 and 9 years of age and 819 (80.0%) discharges were from freestanding children’s hospitals. In 2009, there were 50 discharges which rose to 143 discharges in 2019 (Fig 1). This represents a 186% total increase and a 16.9% annual increase over the study period. Median length of stay was 4 [2–8] days and there were 17 (1.7%) in-hospital mortalities. Complete discharge demographics are presented in Table 1. Discharges occurred from 67 different hospitals with 4 (6.0%) hospitals representing 71.4% of all discharges while 56 (83.6%) hospitals had 10 or fewer discharges over the study period representing an average of less than 1 discharge per year over that time (Fig 2). A density map of discharges by patient location is shown in Figure 3.
Figure 1. Number of discharges of Hypoplastic Left Heart Syndrome patient by year.
Figure 2. Number of Hypoplastic Left Heart discharges by hospital.
Figure 3. Density map of Hypoplastic Left Heart Syndrome discharges by location of residence.
Table 1. Overall discharge demographics and outcomes.
Admitting and principle diagnoses
The most frequent admitting diagnoses were related to CHD with 174 (17.0%) followed by gastrointestinal diagnoses with 142 (13.9%) and pulmonary diagnoses with 102 (10.0%). The most frequent primary diagnoses were also related to CHD with 167 (16.3%) followed by infectious diagnoses with 159 (15.5%) and gastrointestinal diagnoses with 149 (14.6%). The breakdown of admitting and primary diagnosis categories are presented in Tables 2 and 3. The most frequent primary diagnosis for in-hospital mortalities was CHD with 4 (23.5%) followed by infection with 3 (17.6%), neurologic with 2 (11.8%), and gastrointestinal with 2 (11.8%).
Table 2. Frequency of admitting diagnoses overall and by age group.
Table 3. Frequency of principle diagnoses overall and by age group.
Procedures performed
A total of 224 (21.9%) discharges included a surgical or catheter-based procedure. There were 23 (2.2%) heart transplants representing 10.3% of all discharges with procedures and 5 (0.5%) VAD placements representing 2.2% of all discharges with procedures. The 23 heart transplants represented 0.8% (23/3046) of all heart transplants performed in Texas over the same period. 11 Additionally, 26 (2.5%) discharges included a gastrointestinal intervention and 12 (1.2%) discharges included a musculoskeletal intervention. Discharges of patients with a cardiac intervention had a longer length of stay (6 [2–12] days vs. 3 [2–6] days, p < 0.001) but no difference in in-hospital mortality (2.2% vs. 1.5%, p = 0.552).
Characteristics by ages
All age groups had an increase in numbers of discharges across the study period (Fig 4). The highest proportion of discharges throughout the entire study period was in the 5–9 year age group. However, the proportion fell from 56% of discharges in 2009 to 42.7% of discharges in 2019. This was offset by a rise in proportion of discharges in the 20–24 year age group which rose from 0% in 2009 and 1.5% in 2010 to 10.5% in 2019 (Fig 4). The 25+ years group was most likely to be female (n = 25 (61%)) and most likely to be uninsured (n = 7 (17.1%)). The percentage of discharges from children’s hospital decreased from >80% in all age groups 19 year and younger to 52.9% in the 20–24 year age group and 17.1% in the 25+ year group. No differences were seen across age groups for length of stay or in-hospital mortalities. (Table 4) Forty-three hospitals had at least one discharge of a patient 20 years of age or older, 2 (4.7%) centres accounted for 29.7% of the discharges, with no other centre representing more than 5.4% of the discharges (Fig 5).
Figure 4. Hypoplastic Left Heart Syndrome discharges by age group over time.
Figure 5. Number of Hypoplastic Left Heart Discharges of patients 20 years and older by hospital.
Table 4. Demographics and outcomes by age group.
Bold value represents p < 0.05.
Admitting diagnoses, principle diagnoses, procedures, and age
The frequency of admitting and principle diagnosis categories by age group is displayed in Tables 2 and 3. Of note, pregnancy was the most frequent admitting and principle diagnosis category for the 25+ year age group representing 36.6% of discharges. No differences were found in procedures across the age groups (Table 5). The 20 heart transplants that occurred in patients <18 years of age constituted 5.0% (20/399) of all paediatric heart transplants in Texas during the study period. 11
Table 5. Interventions by age group.
Discussion
From 2009 through 2019 discharges of patients with Hypoplastic Left Heart Syndrome 5 years and older increased at a rapid rate and increases were seen across all evaluated age groups. This increase was coupled with an increase in proportion of discharges of older Hypoplastic Left Heart Syndrome patients, with the proportion of discharges of patients between 5 and 9 years old declining from 56 to 43% and a commensurate increase from 2 to 14% in the proportion of discharges of patients 20 years and older. Over that time CHD diagnoses were the most frequent reason for admission. More than 20% of these discharges involved an invasive procedure. Expectedly, cardiac-related surgical and catheter-based procedures represented the majority of procedures performed. In-hospital mortality was 1.7% with one of the mortalities following a heart transplant that admission. No other mortalities followed an elective cardiac procedure.
The 186% growth in discharges from 2009 through 2019 far outstrips the 17.1% growth of the Texas population over the same period of time. 12 O’Leary et al. identified a 32.8% and 87.8% growth in all paediatric and adult CHD hospitalisations, respectively, nationally from 1998 through 2010, far lower than the growth seen in in this study. Reference O’Leary, Siddiqi, de Ferranti, Landzberg and Opotowsky13 The growth is also significantly more than the overall ACHD hospitalisations in Texas (41%) during the same time. Reference Well, Mizrahi and Johnson8 This substantially larger increase likely is a product of relatively greater improvements in survival, with improved medical and surgical techniques, in patients with Hypoplastic Left Heart Syndrome compared to other CHD diagnoses. The increased proportion of discharges of adult patients with Hypoplastic Left Heart Syndrome found over the study period supports this hypothesis. However, this increase also points to a continued complexity and care need in this population.
The most frequent admitting and primary diagnoses in this population were cardiac-related. This supports the lifelong complexities of living with Hypoplastic Left Heart Syndrome. While CHD, arrythmias, and heart failure contributed to a significant portion of principle diagnoses, other Fontan-related complications, such as cerebrovascular accident, hepatic dysfunction, and protein-losing enteropathy, were less common each with fewer than 10 discharges represented. It should be noted, however, a significant portion of discharges was for other indications. This was also seen in the procedures performed during the hospitalisations, most were cardiac, however many involved other organ systems. As the Hypoplastic Left Heart Syndrome population continues to grow and age, it will be important to study the interaction of Hypoplastic Left Heart Syndrome and the Fontan circulation with other cardiac and non-cardiac conditions which occur within the general population. Greater understanding of these interactions will not only improve clinical care for the Hypoplastic Left Heart Syndrome population, but will also provide more clarity to individuals with Hypoplastic Left Heart Syndrome and their families as to what to expect and anticipate over time, reducing the uncertainty in the condition.
The complexity of Hypoplastic Left Heart Syndrome results in an increased healthcare resource utilisation particularly prior to Fontan completion. Reference Hansen, Madsen, Bishop, Morales and Anderson14,Reference Zielonka, Snarr and Liu15 Despite an inability to track patients over time in this dataset, the increased resource utilisation is alluded to. The Hypoplastic Left Heart Syndrome population represents approximately 2–3% of all CHD births. Reference Liu, Chen and Zühlke16 However, in this study, the 5–17-year-old Hypoplastic Left Heart Syndrome population accounted for 5% of all paediatric heart transplants and 7% (20/284) of heart transplants of patients 1–17 years of age. This percentage disparity is likely larger as the 2–3% proportion is at birth, where there is significant attrition over time with a 59–64% survival at 6 years of age. Reference Newburger, Sleeper and Gaynor17 Overall, this resource utilisation was focussed on hospitals which represented more than 70% of the discharges. However, 12.7% (n = 130) of discharges were from 1 of 56 hospitals with fewer than 1 Hypoplastic Left Heart Syndrome discharge per year and 2.8% (n = 29) discharged came from hospitals with a single Hypoplastic Left Heart Syndrome discharge over the study period. This dispersion of resource utilisation is magnified in adults with Hypoplastic Left Heart Syndrome with only two hospitals having at least an average of one adult Hypoplastic Left Heart Syndrome discharge per year. Additionally, 24 (20.5%) of the adult Hypoplastic Left Heart Syndrome discharges came from a hospital with only a single adult Hypoplastic Left Heart Syndrome discharge over the study period. This dispersion illustrates the need for robust mechanisms by which to care for this population and allow timely access to specialists familiar with Hypoplastic Left Heart Syndrome management across far-flung hospitals.
As patients with Hypoplastic Left Heart Syndrome require lifelong medical follow-up, access to adequate health insurance is imperative. A significant transition point for health insurance is at the age of 26 years when children can no longer be covered as dependents under parental insurance. In the general population, it is estimated that 2.5–5.3% of individuals lose coverage when they turn 26 years old with resultant decreases in outpatient physician and dental visits. Reference Yörük18 The current study revealed relatively low rates of discharges of uninsured patients for all age groups aside from the 25 years and older group with 17.1% being uninsured. This rate of uninsured discharges is significantly higher than the 6% rate of uninsured in all forms of adults with CHD discharges in a national sample. Reference Salciccioli, Salemi, Broda and Lopez19 Further work on understanding the full impact of the lack of insurance, along with the development of solutions to prevent this situation, is urgently needed.
Limitations
The limitations of this study should be noted. As a retrospective analysis of an administrative dataset, there are the usual limitations including the lack of complete clinical data for individual patients. Further, as the unit of analysis is a hospital discharge without any unique patient identifiers, there is a possibility that a single patient may be represented multiple times if they had multiple hospitalisations during the study period.
There is the potential for misclassification of admitting and principle diagnoses as these are reliant on accurate coding of the actual diagnoses at the reporting hospitals. This risk is reduced by grouping these diagnoses into larger categories for analysis, as it is less likely the diagnoses would be misclassified into the wrong organ system. It is further possible that discharges with Hypoplastic Left Heart Syndrome diagnoses were not of true Hypoplastic Left Heart Syndrome patients and conversely, that some discharges of Hypoplastic Left Heart Syndrome patients were not identified as the Hypoplastic Left Heart Syndrome diagnosis was not recorded. This is likely a small risk given that Hypoplastic Left Heart Syndrome has a unique diagnosis code and it is a condition that is quite unique and unlikely to be confused with others.
This analysis only captures patients who are discharged from a hospital and is unable to assess the experience of these patients outside of the hospital setting or to assess the experiences of those who have not been hospitalised during the study period.
Conclusion
Discharges of children and adults with Hypoplastic Left Heart Syndrome continue to rise at a rapid pace, particularly in the adult age groups. While many of these hospitalisations are secondary to cardiac diagnoses and procedures, this patient population is also impacted by many other conditions, similar to the general population. Further, the rates of uninsured Hypoplastic Left Heart Syndrome adults surpass the rates in general adults with CHD hospitalisations and the general population. This rate of uninsured is likely exacerbated by the loss of parental insurance coverage at 26 coupled with their underlying complex CHD potentially limiting employment opportunities. Further work must be done to understand the interplay between Hypoplastic Left Heart Syndrome and other conditions and experiences that occur within the general population. These conditions and experiences will become more common as the Hypoplastic Left Heart Syndrome population ages and grows in size. As the Hypoplastic Left Heart Syndrome population evolves, it provides a unique opportunity to develop creative solutions to the challenges faced by these patients and their families.
Supplementary material
To view supplementary material for this article, please visit https://doi.org/10.1017/S1047951122003146
Acknowledgements
None.
Financial support
This research received no specific grant from any funding agency, commercial, or not-for-profit sectors.
Conflicts of interest
None.
Ethical standards
The Institutional Review Board of the University of Texas at Austin Dell Medical School deemed this as not human subjects research as the study involved de-identified, publicly available data.
