Intensive Care Unit Utilization and Mortality Among Medicare Patients Hospitalized With Non–ST-Segment Elevation Myocardial Infarction

Importance: Intensive care unit (ICU) utilization may have important implications for the care and outcomes of patients with non-ST-segment elevation myocardial infarction (NSTEMI). Objectives: To examine interhospital variation in ICU utilization in the United States for older adults with hemodynamically stable NSTEMI and outcomes associated with ICU utilization among patients with low, moderate, or high mortality risk. Design, Setting, and Participants: This study was a retrospective analysis of 28 018 Medicare patients 65 years or older admitted with NSTEMI to 346 hospitals participating in the Acute Coronary Treatment and Intervention Outcomes Network (ACTION)-Get With the Guidelines from April 1, 2011, through December 31, 2012. Patients with cardiogenic shock or cardiac arrest on presentation were excluded. Data analysis was performed from May 7 through October 8, 2015. Exposures: Hospitals with high (>70% of patients with NSTEMI treated in an ICU during the index hospitalization), intermediate (30%-70%), or low (<30%) ICU utilization. Main Outcomes and Measures: Thirty-day mortality. Results: Of 28 018 patients with NSTEMI 65 years or older (median age, 77 years interquartile range, 71-84 years; female, 13 055 46.6%; nonwhite race, 3931 14.0%), 11 934 (42.6%) had an ICU stay. The proportion of patients with NSTEMI treated in the ICU varied across hospitals (median, 38%; interquartile range, 26%-54%), but no significant differences were found in hospital or patient characteristics among high, intermediate, or low ICU utilization hospitals. Compared with high ICU utilization hospitals, low or intermediate ICU utilization hospitals were only marginally more selective of higher-risk patients, as determined by ACTION in-hospital mortality risk score or initial troponin level. The median ACTION risk score for patients treated in the ICU at low and intermediate ICU utilization hospitals was 34 compared with 33 for patients not treated in the ICU; at high ICU utilization hospitals, the median ACTION mortality risk score was 33 for patients treated in the ICU and 34 for patients not treated in the ICU. Thirty-day mortality rates did not significantly differ based on hospital ICU utilization (high vs low: 8.7% vs 8.7%; adjusted odds ratio, 0.91; 95% CI, 0.76-1.08; intermediate vs low: 9.6% vs 8.7%; adjusted odds ratio, 1.06; 95% CI, 0.94-1.20). The association between hospital ICU utilization and mortality did not change when considered among patients with ACTION risk scores greater than 40, 30 to 40, and less than 30 (adjusted interaction P = .86). Conclusions and Relevance: Utilization of the ICU for older patients with NSTEMI varied significantly among hospitals. This variability was not explained by hospital characteristics or driven by patient risk. Mortality after myocardial infarction did not significantly differ among high, intermediate, or low ICU utilization hospitals.