The population of adults with tetralogy of Fallot (TOF) is growing, and it is not known how the changes in age distribution, treatment strategies, and prevalence of co-morbidities impact their interaction with the health care system. We sought to analyze the frequency and reasons for hospital admissions over the past decade. We extracted serial cross-sectional data from the United States Nationwide Inpatient Sample on hospitalizations including the diagnostic code for TOF from 2000 to 2011. From 2000 to 2011, there were 20,545 admissions for subjects with TOF, with a steady increase in annual number. The most common primary admission diagnoses were heart failure (HF; 17%), arrhythmias (atrial 10% and ventricular 6%), pneumonia (9%), and device complications (7%). The rates of co-morbidities increased significantly, particularly diabetes (4.5% to 8.1%), obesity (2.1% to 6.5%), hypertension, and renal disease. The number of pulmonic valve replacements increased (6.8% to 11.3% of TOF admissions, p <0.001), with an increase in median age at surgery from 16 to 19 years old (p = 0.036). The cost per TOF admission was more than double that of noncongenital HF admissions and rose significantly, reaching $21,800 ± 46,000 in 2011. In conclusion, hospitalized patients with TOF have become significantly more medically complex and are growing in number. The increase in the prevalence of obesity, hypertension, and diabetes in this young population supports the need for prevention efforts focused on modifiable risk factors, in addition to HF and arrhythmia treatment. The increase in cost of care calls for further analysis of areas in which efficiency can be increased to ensure high quality of care and lifelong follow-up of patients with TOF.
Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect. Although surgical correction in infancy and childhood pioneered in the last 60 years leads to a high rate of event-free survival, adolescents and adults with TOF are at increased risk for hospital admission due to late sequelae of those operations, and they need to be cared for by both general and specialized congenital physicians. Care of adults with TOF was dramatically changed in the last 2 decades with recognition of the deleterious effect of chronic pulmonary valve regurgitation, timing of pulmonary valve replacement (PVR) based on right ventricular size and function, clinical heart failure (HF) and risk of sudden cardiac death, and the introduction of percutaneous PVR. The effects on hospital admissions and resource use of an aging TOF population, as well as new evidence regarding the optimal timing and methods for PVR, have not been investigated. In this study, we use a comprehensive national sample of hospital admissions to assess trends in the rate of TOF admissions, reasons for hospitalization, cost of care, and outcomes in the United States.
Methods
We extracted data on TOF admissions from 2000 to 2011 from the Nationwide Inpatient Sample (NIS), part of the Healthcare Cost and Utilization Project. The NIS is a database of diagnostic codes and deidentified data from a stratified sample approximating 20% of inpatient admissions in the United States. The Agency for Healthcare Research and Quality, which supports the database, provides sampling weights, which are then used to calculate national estimates. Adolescents and adults (over the age of 10) admitted between 2000 and 2011 with an International Classification of Diseases, Ninth Revision code for TOF (745.2) were included, similar to previous studies, and compared with the total number of admissions in the NIS. We analyzed demographic information available in the NIS, which includes age at admission, gender, year of admission, and Agency of Healthcare Research and Quality co-morbidities which are based on Elixhauser’s co-morbidity measures, which include HF, chronic pulmonary disease, coagulopathy, diabetes, hypertension, liver disease, obesity, and renal failure. PVR was assessed using the following surgical and percutaneous procedure codes: 33475, 35.07, 35.08, 35.25, 35.26; we excluded patients with a Rastelli procedure (35.83, 35.92). Electrophysiology procedures were selected according to the codes for pacemaker (37.80-37.89, 00.50-00.54, 33206-33208), lead revision (37.7), cardioversion (99.60-99.69, 92961), MAZE procedure (37.33-37.34), defibrillator (37.9-37.98, 33240-33249), electrophysiology testing (37.26-37.29, 93619-93624, 93285-93299), and ablation (37.34, 93650-93652). The primary diagnosis at admission was extracted for all patients; the secondary diagnosis was used for patients with TOF listed as primary. Admissions with the primary diagnosis code of HF (428) or arrhythmia (427) in patients with TOF were compared with admissions with the same primary admission code but without a congenital diagnosis code, in the same time period. 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 was reported as means with SD for continuous variables and medians and interquartile ranges (IQRs) for nonnormally distributed continuous data. p-Values for the summary measurements and estimates of the national counts were obtained using proc surveyfreq and surveyreg in SAS that accounts for the complex sampling of the NIS. Missing data were very rare for the measurements of interest (<1%). The linear trend and the Mantel-Haenszel trend tests were used respectively for continuous and categorical variables to compare annual trends between time periods of 2000 to 2003, 2004 to 2007, and 2008 to 2011. Multiple linear regression was used to analyze the relation between co-morbidities and admission cost. Analyses were conducted using SAS software, version 9.3 (SAS Institute Inc., Cary, North Carolina). A p value <0.05 was considered statistically significant.
Results
There were 20,545 admissions for subjects with TOF overall between 2000 and 2011, indexed to the population of the United States ( Table 1 ). The number of admissions increased over the study period at a similar pace as the overall admission rate in the NIS. The most common admission diagnoses were HF, arrhythmias, and pulmonary disease, when excluding TOF itself and other anatomic diagnoses (such as “pulmonary valve disease”; Table 2 ). The most common co-morbidity (which is listed in a distinct field from the primary diagnosis at admission) was HF. There was, however, a significant increase in the rate of arrhythmias, hypertension, diabetes, obesity, renal, and hepatic disease ( Figure 1 ), and the Charlson Comorbidity Index (from 0.7 ± 0.9 to 0.9 ± 1.0, p <0.001). The rates of obesity increased in adolescents and adults up to age 65; the population of young adults, aged 18 to 40 years, had the most marked increase in co-morbidities ( Figure 1 ).
| Characteristics | Overall | 2000-2003 | 2004-2007 | 2008-2011 | p-value |
|---|---|---|---|---|---|
| Number of admissions, indexed to U.S. population | 20,545 | 6260 | 7113 | 7172 | 0.46 ∗ |
| Mean age at admission (95% CI) | 31.9 (15-48.8) | 30.6 (15.2-46) | 32.3 (15.8-48.8) | 32.5 (16.3-48.7) | 0.002 |
| Proportion of adults (age ≥ 18) | 75.7% | 72.4% | 76.1% | 78.1% | < 0.001 |
| Female gender | 52.1% | 54.0% | 52.1% | 50.4% | 0.062 |
| Elective admission | 33.7% | 34.6% | 33.4% | 33.6% | 0.74 |
| Mortality during the admission | 3.1% | 3.2% | 3.4% | 2.8% | 0.58 |
| Location and teaching status of hospital | 0.036 | ||||
| Rural | 6.8% | 9.3% | 5.9% | 5.4% | |
| Urban non-teaching | 21% | 20% | 23% | 20% | |
| Urban Teaching | 72% | 70% | 71% | 74% | |
| Disposition of patient | 0.62 | ||||
| Home | 79.6% | 80.9% | 79.0% | 79.1% | |
| Home with services | 7.0% | 5.8% | 7.0% | 8.1% | |
| Transfer to short term hospital or rehab | 9.6% | 9.7% | 9.8% | 9.3% | |
| Discharge against medical advice | 0.6% | 0.5% | 0.6% | 0.6% | |
| Comorbidities | |||||
| Hypertension | 13.4% | 8.8% | 12.2% | 16.4% | < 0.001 |
| Diabetes mellitus | 5.9% | 4.5% | 4.3% | 8.1% | < 0.001 |
| Obesity † | 4.0% | 2.1% | 2.2% | 6.5% | < 0.001 |
| Congestive heart failure | 24.3% | 25.3% | 23.3% | 24.6% | 0.74 |
| Procedures during hospitalization | |||||
| PVR (% of total TOF admissions) | 9.1% | 6.8% | 9.0% | 11.3% | < 0.001 |
| Mean age at surgery (years, 95% CI) | 23.5 (10.6-36.4) | 20.7 (9.5-31.9) | 24.9 (11-38.8) | 23.7 (10.9-36.5) | 0.075 |
| Age>18 at PVR | 52% | 41% | 54% | 66% | 0.037 |
| Mortality during the PVR admission | 0.8% | 2.3% | 0% | 0.6% | NS |
| Proportion of PVR performed in urban academic hospital with >325 beds | 66.8% | 45.5% | 60.8% | 82.6% | <0.001 |
| Electrophysiology procedure performed during admission | 11.2% | 10.4% | 12.1% | 11.0% | NS |
∗ p-Value for comparison with all admissions in the NIS, which are increasing as well.
† Defined with diagnostic codes 286.0-286.9, 278-278.03, 649.1-649.14, 793.91, V85.3-85.39, V85.41-85.45, V85.54.
| Diagnosis | % of TOF admissions |
|---|---|
| Valvular or structural disease ∗ | 16.6% |
| Heart failure | 10.1% |
| Pulmonary disease | 9.7% |
| Complication of surgery or device | 6.8% |
| Supraventricular tachycardia | 6.8% |
| Ventricular tachycardia | 3.2% |
| Neurological disease | 2.8% |
| Pregnancy and delivery | 1.8% |
| Endocarditis | 1.5% |
| Syncope | 1.3% |
| Renal disease | 1.1% |
| Chest pain | 1.0% |
| History of cardiac surgery | 0.8% |
| Gastrointestinal disease | 0.6% |
| Hematologic disease | 0.5% |
| Coronary artery disease | 0.5% |
| DiGeorge syndrome | 0.5% |
| Other † | 34.4% |
∗ Includes pulmonary valve disease, pulmonary artery anomaly, pulmonary heart disease, atrial septal defect, and ventricular septal defect.
There were 1,891 admissions for PVR, with a doubling of the annual rate (compared with the total number of TOF admissions, trend p value <0.001) during the interval studied ( Table 1 ). There were no patients with billing codes for percutaneous PVR (35.07, 35.08) captured in this time period as these codes were implemented in October 2011; percutaneous PVR before then were done as part of clinical trials, and possibly used the surgical PVR codes. Patients admitted for PVR were less medically complex, as measured by the Charlson Comorbidity Index, than the general TOF population, but their complexity did increase over the study period (0.15 ± 0.39 to 0.31 ± 0.62, p = 0.031). There was a significant shift toward PVR being performed in large hospitals ( Table 1 ; as defined by the NIS, specific to region and academic status ).
The average inflation-adjusted cost per admission increased from $17,500 ± 27,200 in 2000 to $21,800 ± 46,000 in 2011 (p = 0.016; expressed in 2011 US dollars) in the population overall ( Figure 2 ), double the cost of admissions for arrhythmia, or HF in the noncongenital population in the NIS (which respectively were $10,200 ± 15,000 to $11,000 ± 16,000, and $9,800 ± 15,000 to $11,000 ± 17,000 in 2000 to 2011). The charges billed per admission were greater and had an increasing gap compared with the actually reimbursed costs described previously ($35,000 to nearly $70,000 from 2000 to 2011). The median length of stay was stable at 3 days (IQR 2 to 6) for overall TOF hospitalizations and 5 days (IQR 5 to 7) for PVR admissions, with a trend toward decreased postoperative length of stay over the study period that did not reach statistical significance. A regression analysis showed that PVR was the most strongly correlated factor with an increase in cost of the admission in the population overall; on average, it added $32,403 (95% CI $27,826 to $36,979, p <0.001) to the total cost of the admission. In an exploratory multivariate analysis of adults aged between 18 and 40 years, an admission for arrhythmia, surgery during the admission and coagulopathy were correlated with an increase in cost, whereas a history of lung disease was inversely related to cost, and admission for HF, a history of diabetes, or hypertension were not significantly independently associated with cost.
