Patients with single-ventricle (SV) anatomy now live to adulthood. Little is known about the cost of care and outcomes for patients with SV anatomy, especially those who develop heart failure (HF) cared for in adult hospitals in the United States. We analyzed the Nationwide Inpatient Sample from 2000 to 2011 for patients >14 years admitted to adult hospitals with the International Classifications of Diseases, Ninth Revision , codes for SV anatomy. Demographics, outcomes, co-morbidities, and cost were assessed. From 2000 to 2011, the number of SV admissions was stable with a trend toward increased cost per admission over time. Coexistent hypertension, obesity, and liver, pulmonary, and renal diseases significantly increased over time. The most common reason for admission was atrial arrhythmia followed by HF. Patients with SV with HF had significantly higher inhospital mortality, length of stay, and more medical co-morbidities than those with SV and without HF. In conclusion, the cohort of patients with SV admitted to adult hospitals has changed in the modern era. Patients with SV have medical co-morbidities including renal and liver diseases, hypertension, and obesity at a surprisingly young age. Aggressive and proactive management of HF and arrhythmia may reduce cost of care for this challenging population. Patients with SV with HF have particularly high mortality, more medical co-morbidities, and increased cost of care and deserve more focused attention to improve outcomes.
Patients with congenital heart disease are now living into adulthood because of improved palliative surgical techniques used in infancy and early childhood. Patients with palliated single-ventricle (SV) anatomy are a particularly vulnerable population with significant medical co-morbidities and high utilization of health care resources. The prevalence of heart failure (HF) in particular has increased in the adult congenital heart disease (ACHD) population as more of these patients are surviving into adulthood. Patients with SV after Fontan procedure are among the highest risk group for development of HF. Previous studies have shown that patients with ACHD with HF have increased hospital mortality and multiple medical co-morbidities, but those with SV were not included in these investigations. In this study, we use a comprehensive national sample of hospital admissions to assess trends in the population rate of SV admissions, reasons for hospitalization, rate of HF, and associated outcomes and resource utilization in adult hospitals in the United States.
Methods
We analyzed SV admissions from 2000 to 2011 using discharge data from the National Inpatient Sample and the Nationwide Inpatient Sample (NIS), Healthcare Cost and Utilization Project, and Agency for Healthcare Research and Quality (AHRQ). The NIS is a database of diagnostic codes and de-identified data from a stratified sample meant to approximate about 20% of inpatient admissions in the United States. The AHRQ, which supports the database, provides sampling weights that are then used to calculate national estimates.
Patients >14 years were included in our study if they were admitted to an adult acute care hospital during this time frame with an International Classification of Diseases, Ninth Revision ( ICD-9 ), code for SV commonly used in the literature, denoted by the particular underlying anatomy as defined by the following ICD-9 codes: common ventricle, 745.3; tricuspid atresia, 746.1; and hypoplastic left heart, 746.7. We analyzed demographic information available in the NIS that includes age at admission, gender, year of admission, and AHRQ co-morbidity measures and inhospital mortality.
We analyzed demographic information available in the NIS, which includes age at admission, gender, year of admission, and AHRQ co-morbidities, which are based on Elixhauser’s co-morbidity measures. These co-morbidities included HF, chronic pulmonary disease, coagulopathy, diabetes, hypertension, liver disease, obesity, and renal failure. Hospital characteristics including size and geographic location were also collected.
We investigated the following outcomes: trends in admissions for patients with SV by underlying anatomic diagnosis, inhospital mortality, patient co-morbidities, hospital charges per admission, and hospital characteristics. Patients with SV with and without HF were then compared.
From the year 2001 onward, data on hospital charges per admission were extracted from the NIS and converted to costs based on Healthcare Cost and Utilization Project Cost-to-Charges ratio files, which contain hospital- and year-specific data. Our cross-sectional study of observational data conforms with the Strengthening the Reporting of Observational Studies in Epidemiology guidelines.
Summary statistics were reported as means with SD for continuous variables or medians and interquartile ranges for non-normally distributed continuous data. We first estimated trends in total SV hospitalizations per year. Patient and hospital characteristics, inhospital mortality, and cost were analyzed separately for the subset of SV admissions that contained a code for HF. The primary diagnosis at admission was extracted for all patients, unless it was SV, in which case a secondary diagnosis was used.
To account for variation because of sampling, discharge weights were applied to the data set based on methods established by the Healthcare Cost and Utilization Project. National estimates are reported to facilitate comparisons.
The linear trend and the Mantel-Haenszel trend tests were used respectively for continuous and categorical variables to compare annual trends. Analyses were conducted using SAS software, version 9.3 (SAS Institute Inc., Cary, North Carolina). Sample weights were used as described earlier for national estimates. A p value <0.05 was considered statistically significant.
Results
When indexed to the population of the United States, there were 11,068 individual admissions with SV anatomy from 2000 to 2011. The number of SV admissions per year was stable over time, and the average inhospital mortality for patients with SV was 3.8% and stable over the decade ( Table 1 ). The average age at admission was 29.1 years (±14.5), without a significant change over the study period. The percentage of admissions with underlying diagnosis of common ventricle did not change significantly over time ( Figure 1 ). The number of admissions with tricuspid atresia decreased over time, whereas the number of admissions with hypoplastic left heart syndrome increased significantly ( Table 1 ).
| Characteristics | Overall | 2000-2003 | 2004-2007 | 2008-2011 | p-value ∗ |
|---|---|---|---|---|---|
| Number of admissions | 11068 | 2926 | 3789 | 4353 | 0.629 |
| Age at admission | 29.1 ± 14.5 | 28.8 ± 14.4 | 28.8 ± 15.1 | 29.5 ± 14.0 | 0.398 |
| Age>=18 | 8677 (78.4%) | 2297 (78.5%) | 2959 (78.1%) | 3426 (78.7%) | 0.905 |
| Female gender | 5313 (48%) | 1404 (48%) | 1819 (48%) | 2089 (48%) | 0.995 |
| Common ventricle | 3940 (35.6%) | 1050 (35.9%) | 1500 (39.6%) | 1393 (32%) | 0.065 |
| Tricuspid atresia | 6087 (55%) | 1779 (60.8%) | 1997 (52.7%) | 2311 (53.1%) | 0.006 |
| Hypoplastic left heart | 1461 (13.2%) | 178 (6.1%) | 466 (12.3%) | 818 (18.8%) | < 0.001 |
| Discharge to home | 8976 (81.1%) | 2423 (82.8%) | 3077 (81.2%) | 3474 (79.8%) | 0.689 |
| Transfer to short term hospital | 410 (3.7%) | 88 (3.0%) | 144 (3.8%) | 174 (4%) | |
| Home with services | 797 (7.2%) | 155 (5.3%) | 280 (7.4%) | 366 (8.4%) | |
| Left against medical advice | 55 (0.5%) | 6 (0.2%) | 27 (0.7%) | 30 (0.7%) | |
| Elective admission | 3520 (31.8%) | 1021 (34.9%) | 1334 (35.2%) | 1201 (27.6%) | 0.002 |
| Rural hospital | 376 (3.4%) | 149 (5.1%) | 110 (2.9%) | 118 (2.7%) | 0.128 |
| Urban non-teaching hospital | 1538 (13.9%) | 427 (14.6%) | 565 (14.9%) | 540 (12.4%) | |
| Urban teaching hospital | 9153 (82.7%) | 2350 (80.3%) | 3115 (82.2%) | 3696 (84.9%) | |
| Cost (2011 Dollars) | 24204.4 ± 48436.2 | 20964.5 ± 44090.6 | 25090.1 ± 45824.5 | 25320.9 ± 52986.0 | 0.060 |
| Length of the admission (days) | 3.0 (2.0, 7.0) | 3.0 (2.0, 7.0) | 3.0 (2.0, 7.0) | 3.0 (2.0, 8.0) | 0.487 |
| Cardiac surgery | 1240 (11.2%) | 316 (10.8%) | 519 (13.7%) | 405 (9.3%) | .033 |
| Cardiac catheterization | 1184 (10.7%) | 331 (11.3%) | 421 (11.1%) | 431 (9.9%) | .728 |
| Electrophysiology study | 332 (3.0%) | 79 (2.7%) | 186 (4.9%) | 70 (1.6%) | .002 |
| In-hospital mortality | 421 (3.8%) | 140 (4.8%) | 140 (3.7%) | 139 (3.2%) | 0.123 |
| Comorbidities | |||||
| Hypertension | 885 (8%) | 184 (6.3%) | 277 (7.3%) | 431 (9.9%) | 0.010 |
| Heart Failure | 1118 (10.1%) | 228 (7.8%) | 330 (8.7%) | 531 (12.2%) | 0.010 |
| Liver Disease | 841 (7.6%) | 143 (4.9%) | 201 (5.3%) | 453 (10.4%) | < 0.001 |
| Diabetes Mellitus | 454 (4.1%) | 123 (4.2%) | 110 (2.9%) | 226 (5.2%) | 0.163 |
| Obesity | 387 (3.5%) | 59 (2%) | 80 (2.1%) | 244 (5.6%) | < 0.001 |
| Pulmonary disease | 421 (3.8%) | 73 (2.5%) | 110 (2.9%) | 218 (5%) | 0.015 |
| Renal Disease | 476 (4.3%) | 32 (1.1%) | 114 (3%) | 283 (6.5%) | < 0.001 |
| Coagulopathy | 1018 (9.2%) | 310 (10.6%) | 250 (6.6%) | 479 (11%) | 0.191 |
| Valvular disease | 564 (5.1%) | 187 (6.4%) | 174 (4.6%) | 226 (5.2%) | 0.643 |
The top 10 most common admitting diagnoses are depicted in Figure 2 . Atrial arrhythmias and HF make up the majority of admitting diagnoses for patients with SV. The major co-morbidities in patients with SV by time period are depicted in Figure 3 . Rates of obesity, hypertension, and pulmonary, liver, and renal diseases increased significantly over the study period (p ≤0.001, 0.010, 0.015, <0.001, and <0.001, respectively). There was an increase in the Charlson Comorbidity Index (CCI) over time: the percentage of SV admissions with a CCI score of ≥2 increased from 12.7% from 2000 to 2003, to 15.3% from 2004 to 2007, and to 24.4% from 2008 to 2011 (p ≤0.001).
There were 3,157 admissions for patients with SV and a diagnosis of HF during the study time period. The inhospital mortality for patients with HF was significantly higher than those without ( Table 2 ). Patients with SV with HF were more likely to be older than those without HF and had significantly increased rates of medical co-morbidities including hypertension, diabetes, obesity, liver, pulmonary, and renal diseases and coagulopathies ( Figure 4 ).
| Characteristics | Heart Failure | No Heart Failure | p-value ∗ |
|---|---|---|---|
| Number of admissions | 3157 | 7912 | |
| Age at admission | 34.1 ± 16.5 | 27.1 ± 13.1 | < 0.001 |
| Age>=18 | 2778 (88%) | 5902 (74.6%) | < 0.001 |
| Female gender | 1566 (49.6%) | 3742 (47.3%) | 0.333 |
| Common ventricle | 1165 (36.9%) | 2785 (35.2%) | 0.454 |
| Tricuspid atresia | 1796 (56.9%) | 4296 (54.3%) | 0.277 |
| Hypoplastic left heart | 328 (10.4%) | 1131 (14.3%) | 0.014 |
| Discharge to home | 2298 (72.8%) | 6678 (84.4%) | <.0001 |
| Transfer to short term hospital | 123 (3.9%) | 277 (3.5%) | |
| Home with services | 319 (10.1%) | 483 (6.1%) | |
| Against medical advice | 25 (0.8%) | 32 (0.4%) | |
| Elective admission | 764 (24.2%) | 2761 (34.9%) | < 0.001 |
| Rural hospital | 155 (4.9%) | 222 (2.8%) | 0.013 |
| Urban non-teaching hospital | 470 (14.9%) | 1068 (13.5%) | |
| Urban teaching hospital | 2532 (80.2%) | 6622 (83.7%) | |
| Cost (2011 Dollars) | 31947.3 ± 670 | 21142.9 ± 3828 | < 0.001 |
| Length of admission (days) | 5.0 (2.0, 10.0) | 3.0 (1.0, 6.0) | < 0.001 |
| In-hospital Mortality | 224 (7.1%) | 198 (2.5%) | < 0.001 |
| Comorbidities | |||
| Hypertension | 451 (14.3%) | 720 (9.1%) | < 0.001 |
| Diabetes Mellitus | 227 (7.2%) | 229 (2.9%) | < 0.001 |
| Liver Disease | 470 (14.9%) | 364 (4.6%) | < 0.001 |
| Obesity | 205 (6.5%) | 174 (2.2%) | < 0.001 |
| Pulmonary disease | 360 (11.4%) | 451 (5.7%) | < 0.001 |
| Renal Disease | 290 (9.2%) | 190 (2.4%) | < 0.001 |
| Coagulopathy | 360 (11.4%) | 657 (8.3%) | 0.033 |
| Valvular disease | 170 (5.4%) | 396 (5%) | 0.696 |
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