Abstract P339: Clinical Characteristics of ‘Microsize’ Myocardial Infarctions in the REasons for Geographic and Racial Differences in Stroke-Myocardial Infarction (REGARDS-MI) Study
Background: New, more sensitive troponin assays have increased the detection of small or ‘microsize’ myocardial infarctions (MIs). The clinical characteristics of individuals presenting with these ‘microsize’ MIs are unknown.
Methods: REGARDS is following 30,239 individuals >45 years of age living in 48 states recruited from 2003-7. To ascertain events, participants are telephoned every 6 months with expert adjudication of potential MIs following national consensus recommendations and based on review of medical records, including laboratory data on troponin levels. We divided all adjudicated definite or probable MIs as of December 31, 2009 into 3 groups based on the peak troponin: 1) microsize MI (peak troponin <0.5 μg/L), 2) intermediate MI (peak troponin >0.5 - <1.5 μg/L), and 3) usual MI (peak troponin >1.5 μg/L). We compared the clinical characteristics of those with microsize and intermediate MIs to those with usual MIs using multivariable adjusted prevalence ratios.
Results: A total of 478 participants experienced a definite or probable MI. Of these, 259 were usual MIs, 95 were intermediate MIs, and 124 were microsize MIs. Mean age was 69+/-9 years, 33% were women, and 32% were African American. Although individuals with microsize MI were more likely to be female and have and elevated body mass index (BMI) than those with usual MI, only BMI remained significant after multivariable adjustment. Compared to those with usual MI, individuals with microsize MI, after multivariable adjustment, were less likely to present with chest pain or symptoms of acute coronary syndrome, less like to have obstructive CHD or undergo percutaneous revascularization, and more likely to have congestive heart failure (Table).
Conclusion: The characteristics of people suffering very small MIs detected by newer, more sensitive troponin assays differ from those with larger MIs, including less obstructive CHD. Further work to elucidate the pathophysiology and optimal clinical management of these individuals is needed.
- © 2013 by American Heart Association, Inc.