Coronary artery bypass graft readmission rates and risk factors - A retrospective cohort study.

Background: Hospital readmissions contribute substantially to the overall healthcare cost. Coronary artery bypass graft (CABG) is of particular interest due to its relatively high short-term readmission rates and mean hospital charges.

Methods: A retrospective review was performed on 2007-2011 data from California, Florida, and New York from the State Inpatient Databases, Healthcare Cost and Utilization Project. All patients ≥18 years of age who underwent isolated CABG and met inclusion/exclusion criteria were included. Insurance status was categorized by Medicaid, Medicare, Private Insurance, Uninsured, and Other. Primary outcomes were unadjusted rates and adjusted odds of readmission at 30- and 90-days. Secondary outcomes included diagnosis at readmission.

Results: A total of 177,229 were included in the analyses after assessing for exclusion criteria. Overall 30-day readmission rate was 16.1%; rates were highest within Medicare (18.4%) and Medicaid (20.2%) groups and lowest in the private insurance group (11.7%; p < 0.0001). Similarly, 90-day rates were highest in Medicare (27.3%) and Medicaid (29.8%) groups and lowest in the private insurance group (17.6%), with an overall 90-day rate of 24.0% (p < 0.0001). The most common 30-day readmission diagnoses were atrial fibrillation (26.7%), pleural effusion (22.5%), and wound infection (17.7%). Medicare patients had the highest proportion of readmissions with atrial fibrillation (31.7%) and pleural effusions (23.3%), while Medicaid patients had the highest proportion of readmissions with wound infections (21.8%). Similar results were found at 90 days. Risk factors for readmission included non-private insurance, age, female sex, non-white race, low median household income, non-routine discharge, length of stay, and certain comorbidities and complications.

Conclusions: CABG readmission rates remain high and are associated with insurance status and racial and socioeconomic markers. Further investigation is necessary to better delineate the underlying factors that relate racial and socioeconomic disparities to CABG readmissions. Understanding these factors will be key to improving healthcare outcomes and expenditure.