Background:
Research on acute myocardial infarction (AMI) in medical claims largely focuses on hospitalizations where AMI is the primary discharge diagnosis (dx). Limited data are available on AMIs occurring as a secondary dx during hospitalization.
Hypothesis:
We hypothesized that mortality following AMI is higher when the primary dx is not AMI.
Methods:
We examined REasons for Geographic And Racial Differences in Stroke (REGARDS) study participants with definite or probable AMIs adjudicated using published guidelines. Participants were categorized by hospital discharge dx from the discharge summary: primary dx, secondary dx, or no dx of AMI. All-cause and cardiovascular mortality after AMI, detected though active follow-up and the National Death Index, were compared using Kaplan-Meier curves with log-rank tests and Cox proportional hazard models adjusted for sociodemographics, medical history, and characteristics of the AMI (clinical evidence of ischemia, peak troponin, and heart failure during hospitalization).
Results:
Of 877 participants with AMI, 37% had AMI as primary dx, 12% had AMI as a secondary dx, and 51% had no dx of AMI. All-cause mortality (n = 284) was higher among participants with AMI as a secondary dx or without a dx of AMI than among participants with AMI as primary dx, but cardiovascular mortality (n = 150) was similar across groups (
Figure
). Compared to participants with AMI as primary dx, adjusted hazard ratios for all-cause mortality were 1.03 (95% CI 0.68-1.57) and 1.17 (95% CI 0.84-1.62) and for cardiovascular mortality were 0.79 (95% CI 0.46-1.37) and 0.91 (95% CI 0.60-1.38) for participants with AMI as a secondary dx and without a dx of AMI, respectively.
Conclusions:
Studies of AMI based on primary discharge dx likely under count the number of AMIs and exclude a population with similar prognosis in terms of all-cause and CVD mortality, once clinical differences considered. Further study into the characteristics, in-hospital and post-discharge management of these patients may be warranted.
Ten-year mortality for patients discharged after hospitalization for chest pain or other symptoms raising suspicion of acute myocardial infarction in relation to hospital discharge diagnosis
