Risk factors for 30-day readmissions after acute myocardial infarction retrospective cohort study in Dallas Texas, USA

Abstract

Background: The hospital readmission rate has been thought to reflect the quality of patient care. Understanding the risk factors for these can guide strategies to reduce them. Methods Retrospective cohort design that included all the admissions for AMI from October 2011 to September 2014. Primary outcome was 30-day readmission rate. Secondary outcomes were 7-day readmission rate, reasons for readmission and cardiac-related readmission rate. Univariate and multivariate logistic regression were conducted with Hosmer-Lemeshow goodness-of-fit statistics for model calibration and ROC curve for model discrimination. Results We identified 2958 cases of AMI and 334 readmissions (11.3%). The final sample for analysis included 310 readmitted and 652 non-readmitted patients. The principal causes of readmission were cardiac related (42%), followed by respiratory (15%) and gastrointestinal (11%). Separate analysis for the early readmissions showed the same pattern. 42% of the readmissions happened during the first week and 68% in the first 2 weeks after discharge. Median time for readmission was 10 days. Older age, days from admission to catheterization, complete medical therapy at discharge, diabetes, hypertension, stroke, major psychiatric disorders, insurance status, chronic kidney disease and congestive heart failure were independently associated with 30-day readmission. The final multivariate model discriminated well with a ROC of 0.753 (95% CI 0.72-0.79). Conclusion Reasons for readmission found in our study were consistent with previous studies. Absolute readmission rates reported in this study were lower than in some prior publications. We present novel and addressable patient risk factors derived from the index admission that can be used to predict readmission.

Keywords

• acute myocardial infarction
• 30-day readmission
• hospital readmission
• predictive model