Methods:
The Kids’ Inpatient Database (KID) for the years 2000, 2003, 2006, 2009, 2012 and 2016 was used to identify all ICD related hospitalizations. The KID is part of the Healthcare Cost and Utilization Project (HCUP), managed by the Agency for Healthcare Research and Quality (AHRQ) and is the only all-payer inpatient care database for pediatric admissions (defined as age at discharge ≤20 years) in the United States that. It represents 2-3 million discharges per year from public hospitals, specialty hospitals and academic medical centers. Weighted totals were used for analysis. Specific details regarding data in the KID databases are provided in the supplemental section.
For the purposes of this study, ICD admissions were included, defined as patients with existing ICDs at the time of admission. Admissions related to new ICD implantation based on ICD-9 and ICD-10 procedure codes (listed in supplemental information) during the admission were excluded. Procedural codes for replacement of leads or generators without new implant ICD codes were included in ICD admissions. Diagnostic codes were used to categorize admissions into one of four mutually exclusive primary diagnostic categories of underlying disease which were defined as primary 1) CHD (e.g. Tetralogy of Fallot) 2) cardiomyopathy (CM, e.g. hypertrophic CM), 3) arrhythmia disorder (e.g. Long QT syndrome) and 4) Other (e.g. muscular dystrophy or patients in whom diagnostic category could not be determined based on ICD codes available). Coding was hierarchical, with CHD before cardiomyopathy and cardiomyopathy before arrhythmia. As an example, a discharge with Tetralogy of Fallot and cardiomyopathy diagnostic codes was considered primary congenital heart disease. Minor defects such as atrial septal defects (ASD), patent ductus arteriosus (PDA) and patent foramen ovale (PFO) were not included in the CHD category. Secondary cardiomyopathy due to nutritional deficiencies (e.g beri beri) and alcoholic cardiomyopathy were not included in the cardiomyopathy category.
The first aim of the study was to evaluate trends over time in pediatric admissions with ICDs. Rates of hospitalization were calculated by using included hospitalizations < 21 years of age as the numerator and total hospitalizations < 21 years as the denominator, and were calculated by year. The second aim was to determine rates of in-hospital death among admissions with ICDs. All deaths during ICD hospitalizations were identified and compared to total ICD hospitalizations by year. Discharges resulting in hospice care were excluded from this analysis. Our third aim was to evaluate factors associated with in-hospital death in pediatric admissions with ICDs. Data collection included patient demographics and hospital characteristics [hospital region (Northeast, Midwest, South, West) and hospital type (rural, urban non-teaching, and urban teaching)]. Patient characteristics included age, sex, race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, or other which included Asian/Pacific Islander, American Indian, and other), and primary payor (government included Medicare and Medicaid, private insurance company including health maintenance organization, and self-pay, no charge, or other), admission season (fall-September, October, November; winter – December, January, February; spring – March, April, May; Summer – June, July, August). Specific details regarding categorization by diagnosis are provided in the supplemental data. Data regarding other admission factors including whether the admission was elective, whether there was a code for heart failure, cardiac surgery or procedure, ICD complication (consisting of diagnostic codes for mechanical complications, ICD infection, pneumothorax, hemothorax or procedural codes of ICD-revisions) or cardiac arrest were collected. Specific ICD codes used are provided in the supplemental section.