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Brief Report
November 2018

Association of Unrecognized Myocardial Infarction With Long-term Outcomes in Community-Dwelling Older Adults: The ICELAND MI Study

Author Affiliations
  • 1National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
  • 2Department of Medicine, University of Iceland, Reykyavik, Iceland
  • 3Akureyri Hospital, Akureyri, Iceland
  • 4Heart and Vascular Institute of UPMC, University of Pittsburgh, Pittsburgh, Pennsylvania
  • 5The Heart Center, St Francis Hospital, State University of New York at Stony Brook, Stony Brook
  • 6Alaska Heart Institute, Anchorage
  • 7Icelandic Heart Association, Kópavogur, Iceland
  • 8National Institute on Aging, National Institutes of Health, Bethesda, Maryland
JAMA Cardiol. 2018;3(11):1101-1106. doi:10.1001/jamacardio.2018.3285
Key Points

Question  What is the long-term prognosis of individuals with unrecognized myocardial infarction (UMI) detected by cardiac magnetic resonance imaging compared with those with clinically recognized myocardial infarction (RMI) and those with no myocardial infaction (MI)?

Findings  In this cohort study of 935 participants, UMI mortality was similar to no MI mortality in the short term but higher than no MI on intermediate-term follow-up. In the long term, mortality associated with UMI was significantly higher than for no MI, but also not statistically different from RMI.

Meaning  The long-term mortality risk of UMI can be as high as RMI.

Abstract

Importance  Cardiac magnetic resonance (CMR) imaging can identify unrecognized myocardial infarction (UMI) in the general population. Unrecognized myocardial infarction by CMR portends poor prognosis in the short term but, to our knowledge, long-term outcomes are not known.

Objective  To determine the long-term outcomes of UMI by CMR compared with clinically recognized myocardial infarction (RMI) and no myocardial infarction (MI).

Design, Setting, and Participants  Participants of the population-based, prospectively enrolled ICELAND MI cohort study (aged 67-93 years) were characterized with CMR at baseline (from January 2004-January 2007) and followed up for up to 13.3 years. Kaplan-Meier time-to-event analyses and a Cox regression were used to assess the association of UMI at baseline with death and future cardiovascular events.

Main Outcomes and Measures  The primary outcome was all-cause mortality. Secondary outcomes were a composite of major adverse cardiac events (MACE: death, nonfatal MI, and heart failure).

Results  Of 935 participants, 452 (48.3%) were men; the mean (SD) age of participants with no MI, UMI, and RMI was 75.6 (5.3) years, 76.8 (5.2) years, and 76.8 (4.7) years, respectively. At 3 years, UMI and no MI mortality rates were similar (3%) and lower than RMI rates (9%). At 5 years, UMI mortality rates (13%) increased and were higher than no MI rates (8%) but still lower than RMI rates (19%). By 10 years, UMI and RMI mortality rates (49% and 51%, respectively) were not statistically different; both were significantly higher than no MI (30%) (P < .001). After adjusting for age, sex, and diabetes, UMI by CMR had an increased risk of death (hazard ratio [HR], 1.61; 95% CI, 1.27-2.04), MACE (HR, 1.56; 95% CI, 1.26-1.93), MI (HR, 2.09; 95% CI, 1.45-3.03), and heart failure (HR, 1.52; 95% CI, 1.09-2.14) compared with no MI and statistically nondifferent risk of death (HR, 0.99; 95% CI, 0.71-1.38) and MACE (HR, 1.23; 95% CI, 0.91-1.66) vs RMI.

Conclusions and Relevance  In this study, all-cause mortality of UMI was higher than no MI, but within 10 years from baseline evaluation was equivalent with RMI. Unrecognized MI was also associated with an elevated risk of nonfatal MI and heart failure. Whether secondary prevention can alter the prognosis of UMI will require prospective testing.

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