Background: The objective of this study was to assess case fatality and utilization of coronary revascularization for acute myocardial infarction (AMI) when coded in the primary vs. any secondary position at hospital discharge.
Methods: In the Atherosclerosis Risk in Communities (ARIC) Study, a continuous surveillance of hospital discharges for AMI among residents aged 35-74 years in 4 US communities between 2005-2013 was performed. Based on annual hospital discharges, residents with AMI (ICD9 code 410) were probability sampled and subcategorized based on AMI listed in the primary vs. any secondary position. Based on ARIC study criteria (using cardiac pain, electrocardiographic evidence, cardiac biomarkers), AMIs were further adjudicated as definite/probable AMI. Case fatality at 28 and 365 days was identified for AMIs coded in primary vs. secondary positions. Proportion undergoing coronary revascularization (percutaneous or surgical) during the index hospitalization was identified using prespecified ARIC study definitions.
Results: The study population was 53% men, 72% white. After weighting for sampling probabilities, 15097 AMI discharge codes were identified (n=9968 primary; n=5129 secondary positions). Proportions of AMI codes in primary vs. secondary positions for NSTEMI were 75% vs. 25% and for STEMI 90% vs. 10% respectively. 28 day case fatality was twofold higher for AMI in secondary vs. primary positions (9.6% vs. 4.5%). Similarly 365 day case fatality rate was almost twofold higher for AMI in secondary positions vs. primary position (15.2% vs. 8.2%). Proportion undergoing coronary revascularization within the index hospitalization for definite/probable AMI by ARIC criteria was higher for AMI coded in primary vs. secondary positions: 64% vs. 22%.
Conclusions: AMI in secondary position identifies a distinct high-risk group with higher short-term and long-term case fatality rates relative to AMI in the primary position. Rates of coronary revascularization during index hospitalization are lower in those with AMI in secondary vs. primary positions. Future studies should evaluate any correlation between high case fatality and lower coronary revascularization rates in those discharged with AMI in the secondary position.