Background Microsize myocardial infarction (MI) is a recently described phenomenon that meets rigorous criteria for MI with very low peak troponin elevations. We aim to compare the risk for cardiovascular events and mortality following microsize versus usual MIs.
Methods and results Prospective cohort analysis of REasons for Geographic And Racial Differences in Stroke (REGARDS) study participants without a history of coronary heart disease (CHD) who had an incident MI between 2003 and 2015. Incident MIs were classified as microsize MI (peak troponin <0.5 ng/mL) or usual MI (peak troponin ≥0.5 ng/mL). Participants were followed for a composite of cardiovascular events that included recurrent MI, coronary revascularisation, fatal CHD and heart failure, and all-cause mortality. Overall, 1024 participants with an incident MI were included in the analysis (328 with microsize MI and 696 with usual MI). Participants with microsize MI were more likely to be older and black. The multivariable-adjusted adjustment HR for cardiovascular events among participants with microsize versus usual MI after a median follow-up of 1.7 years was 1.11 (95% CI 0.86 to 1.44). The multivariable-adjusted HR for all-cause mortality after 28 days from incident MI among participants with microsize versus usual MI after a median follow-up of 3.6 years was 1.09 (95% CI 0.81 to 1.45).
Conclusion Microsize MIs have a prognostic value for future cardiovascular events and mortality comparable to usual MIs. These findings should encourage clinicians to initiate secondary prevention strategies in patients with microsize MI until this emerging clinical entity is better understood.
- acute myocardial infarction
- quality and outcomes of care
- coronary artery disease
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Contributors ZIA and MMS contributed to the idea of the study. All authors contributed to the planning, design and implementation of the study. JB contributed to the statistical analysis of the study. ZIA, MMS and JB contributed to the writing of the manuscript. All authors contributed to the critical review and revision of the manuscript. Substantial contributions to the conception or design of the work, or the acquisition, analysis or interpretation of data: ZIA, LDC, PMO, JSR, TMB, EBL, JB, MMS. Drafting the work or revising it critically for important intellectual content: ZIA, LDC, PMO, JSR, TMB, EBL, JB, MMS. All authors have approved of the final version and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Funding This work was supported by a cooperative agreement U01 NS041588 from the National Institute of Neurological Disorders and National Heart Lung and Blood Institute R01 HL80477 of the National Institutes of Health, Department of Health and Human Service. Representatives of the funding agency have been involved in the review of the manuscript but not directly involved in the collection, management, analysis or interpretation of the data.
Disclaimer The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Neurological Disorders and Stroke, the National Heart Lung and Blood Institute or the National Institutes of Health.
Competing interests MMS receives salary support from Amgen for investigator-initiated research. TMB receives salary support from Amgen for investigator-initiated research and serves as the site primary investigator for a clinical trial funded by Omthera Pharmaceuticals. EBL has received research support from Amgen, honoraria for Amgen advisory boards and consulting fees from Novartis. LDC receives research grant from Amgen.
Patient consent for publication Not required.
Ethics approval The University of Alabama at Birmingham Institutional Review Board approved the study and informed consent was acquired from all participants.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available on reasonable request. The data that support the findings of this study are available from the corresponding author on reasonable request.
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