Background Acute myocardial infarction (AMI) with in-hospital onset (AMI-IHO) has poor prognosis but is clinically underappreciated. Whether its occurrence has changed over time is uncertain. Methods and Results Since 1987, the ARIC (Atherosclerosis Risk in Communities) study has conducted adjudicated surveillance of AMI hospitalizations in 4 US communities. Our analysis was limited to patients aged 35 to 74 years with symptomatic AMI. Patients with symptoms initiating after hospital arrival were considered AMI-IHO. A total of 26 678 weighted hospitalizations (14 276 unweighted hospitalizations) for symptomatic AMI were identified from 1995 to 2014, with 1137 (4%) classified as in-hospital onset. The population incidence rate of AMI-IHO increased in the 4 ARIC communities from 1995 through 2004 to 2005 through 2014 (12.7-16.9 events per 100 000 people; P for 20-year trend <0.0001), as did the proportion of AMI hospitalizations with in-hospital onset (3.7%-6.1%; P for 20-year trend =0.03). The 10-year proportions were stable for patients aged 35 to 64 years (3.0%-3.4%; P for 20-year trend =0.3) but increased for patients aged ≥65 years (4.6%-7.8%; P for 20-year trend =0.008; P for interaction by age group =0.04). AMI-IHO had a more severe clinical course with lower use of AMI therapies or invasive strategies and higher in-hospital (7% versus 3%), 28-day (19% versus 5%), and 1-year (29% versus 12%) mortality (P<0.0001 for all). Conclusions In this population-based community surveillance, AMI-IHO increased from 2005 to 2014, particularly among older patients. Quality initiatives to improve recognition and management of AMI-IHO should be especially focused on hospitalized patients aged >65.
Keywords: acute myocardial infarction; inpatient onset; outcomes; surveillance.