Intensive care use and mortality among patients with ST elevation myocardial infarction: retrospective cohort study

OBJECTIVE: To evaluate the effect of intensive care unit (ICU) admission on mortality among patients with ST elevation myocardial infarction (STEMI). DESIGN: Retrospective cohort study. SETTING: 1727 acute care hospitals in the United States. PARTICIPANTS: Medicare beneficiaries (aged 65 years or older) admitted with STEMI to either an ICU or a non-ICU unit (general/telemetry ward or intermediate care) between January 2014 and October 2015. MAIN OUTCOME MEASURE: 30 day mortality. An instrumental variable analysis was done to account for confounding, using as an instrument the additional distance that a patient with STEMI would need to travel beyond the closest hospital to arrive at a hospital in the top quarter of ICU admission rates for STEMI. RESULTS: The analysis included 109 375 patients admitted to hospital with STEMI. Hospitals in the top quarter of ICU admission rates admitted 85% or more of STEMI patients to an ICU. Among patients who received ICU care dependent on their proximity to a hospital in the top quarter of ICU admission rates, ICU admission was associated with lower 30 day mortality than non-ICU admission (absolute decrease 6.1 (95% confidence interval -11.9 to -0.3) percentage points). In a separate analysis among patients with non-STEMI, a group for whom evidence suggests that routine ICU care does not improve outcomes, ICU admission was not associated with differences in mortality (absolute increase 1.3 (-0.9 to 3.4) percentage points). CONCLUSIONS: ICU care for STEMI is associated with improved mortality among patients who could be treated in an ICU or non-ICU unit. An urgent need exists to identify which patients with STEMI benefit from ICU admission and what about ICU care is beneficial.