Between-Hospital Variation of In-Hospital Mortality and 30-Day Readmissions in Acute Myocardial Infarction in Portugal: 2012-2014

To study the variation of in-hospital mortality and readmission across Portuguese public hospitals after an acute myocardial infarction (AMI) using contemporary data, assessing the impact of hospital characteristics in between-hospital variability. Retrospective study of acute care hospital discharges occurring between 2012 and 2014 of adult inpatients admitted with a primary AMI. Two cohorts were defined, one to study 30-day all-cause unplanned readmission and another to study in-hospital mortality after an AMI. Patient-Level (demographic and comorbidities) and hospital-level (teaching status, provision revascularization procedures, size and geographical location) characteristics were described for each hospitalization. Crude readmission and mortality rates were computed overall, across years and across hospital characteristic levels. Logistic mixed models were implemented to incorporate the natural clustering of the data at the hospital level and to estimate between-hospital heterogeneity. We used a step-up strategy starting with an empty model and incrementing patient and hospital characteristics to assess their impact on between-hospital variation. We identified 25642 index events in the readmission cohort and 28512 in the mortality cohort. While 8% of patients were readmitted with an unplanned event within 30 days after an AMI, 10% of patients died in hospital after being admitted with a primary AMI. Between-hospital heterogeneity was observed for the two cohorts, but was higher in the mortality cohort. A patient’s odds of dying in a high mortality hospital were more than twice than that in a low mortality hospital. Relative to the empty model, patient characteristics explained most of the heterogeneity (55%). Moreover, hospital characteristics explained an additional 10% of this heterogeneity in the readmission cohort, yet they increased heterogeneity in the mortality cohort. Hospital characteristics partially contribute to the heterogeneity in readmissions across hospitals. However, marked disparities across hospitals in terms of the risk of in-hospital mortality remained after adjusting for hospital case-mix and hospital characteristics.