Between-hospital variation of in-hospital mortality and 30-day readmissions after an acute myocardial infarction in Portugal: 2012-2014

Mariana Fernandes Lobo1, Vanessa Azzone2, Fernando Lopes1,3, Alberto Freitas1, Altamiro Costa-Pereira1, Sharon-Lise Normand2, Armando Teixeira-Pinto4

1CINTESIS – Center for Health Technology and Services Research, Faculty of Medicine University of Porto, 2Department of Health Care policy, Harvard Medical School, 3Health Decision Sciences, Faculty of Medicine of the University of Porto, 4School of Public Health, The University of Sydney

Aim: To study the variation of in-hospital mortality and readmission across Portuguese public hospitals after an AMI event using contemporary data, assessing the impact of hospital characteristics in between-hospital variability.

Methods: Retrospective cohort study of acute care hospital discharges occurring between January 2012 and December 2014 of adult inpatients admitted with a primary AMI. Two cohorts were define, one to study 30-day all-cause unplanned readmission and another to study in-hospital mortality after an AMI. Hospitalizations were characterized regarding patient and hospital characteristics. Crude readmission and mortality rates were computed overall, across years and across hospital characteristic levels. Hierarchical logistic regression models were implemented to incorporate the natural clustering of the data at the hospital level and to estimate between-hospital heterogeneity.

Results: 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 much higher in the mortality cohort. Patient characteristics explained most of this heterogeneity. Moreover, hospital characteristics additionally explained a residual portion of between-hospital heterogeneity in the readmission cohort, yet they increased heterogeneity in the mortality cohort.

Discussion: Marked disparities across hospitals in risk of in-hospital mortality remained after adjusting for hospital case-mix and hospital characteristics. Further investigation is necessary to explain source of this heterogeneity.

keywords: Hospital heterogeneity; Acute myocardial infarction

Presentation: Between-hospital variation of in-hospital mortality and 30-day readmissions after an acute myocardial infarction in Portugal: 2012-2014