title: Prevalence and prognosis of unrecognized myocardial infarction determined by cardiac magnetic resonance in older adults.
abstract: BACKGROUND
  Unrecognized myocardial infarction (MI) is prognostically important. Electrocardiography (ECG) has limited sensitivity for detecting unrecognized MI (UMI).
  
  
  OBJECTIVE
  Determine prevalence and mortality risk for UMI detected by cardiac magnetic resonance (CMR) imaging or ECG among older individuals.
  
  
  METHODS
  ICELAND MI is a cohort substudy of the Age, Gene/Environment Susceptibility-Reykjavik Study (enrollment January 2004-January 2007) using ECG or CMR to detect UMI. From a community-dwelling cohort of older individuals in Iceland, data for 936 participants aged 67 to 93 years were analyzed, including 670 who were randomly selected and 266 with diabetes.
  
  
  METHODS
  Prevalence and mortality of MI through September 1, 2011. Results reported with 95% confidence limits and net reclassification improvement (NRI).
  
  
  RESULTS
  Of 936 participants, 91 had recognized MI (RMI) (9.7%; 95% CI, 8% to 12%), and 157 had UMI detected by CMR (17%; 95% CI, 14% to 19%), which was more prevalent than the 46 UMI detected by ECG (5%; 95% CI, 4% to 6%; P < .001). Participants with diabetes (n = 337) had more UMI detected by CMR than by ECG (n = 72; 21%; 95% CI, 17% to 26%, vs n = 15; 4%; 95% CI, 2% to 7%; P < .001). Unrecognized MI by CMR was associated with atherosclerosis risk factors, coronary calcium, coronary revascularization, and peripheral vascular disease. Over a median of 6.4 years, 30 of 91 participants (33%; 95% CI, 23% to 43%) with RMI died, and 44 of 157 participants (28%; 95% CI, 21% to 35%) with UMI died, both higher rates than the 119 of 688 participants (17%; 95% CI, 15% to 20%) with no MI who died. Unrecognized MI by CMR improved risk stratification for mortality over RMI (NRI, 0.34; 95% CI, 0.16 to 0.53). Adjusting for age, sex, diabetes, and RMI, UMI by CMR remained associated with mortality (hazard ratio [HR], 1.45; 95% CI, 1.02 to 2.06, absolute risk increase [ARI], 8%) and significantly improved risk stratification for mortality (NRI, 0.16; 95% CI, 0.01 to 0.31), but UMI by ECG did not (HR, 0.88; 95% CI, 0.45 to 1.73; ARI, -2%; NRI, -0.05; 95% CI, -0.17 to 0.05). Compared with those with RMI, participants with UMI by CMR used cardiac medications such as statins less often (36%; 95% CI, 28% to 43%, or 56/157, vs 73%; 95% CI, 63% to 82%, or 66/91; P < .001).
  
  
  CONCLUSIONS
  In a community-based cohort of older individuals, the prevalence of UMI by CMR was higher than the prevalence of RMI and was associated with increased mortality risk. In contrast, UMI by ECG prevalence was lower than that of RMI and was not associated with increased mortality risk.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT01322568.
authors.affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Erik B
authors.initials: EB
authors.lastname: Schelbert
authors.forename: Jie J
authors.initials: JJ
authors.lastname: Cao
authors.forename: Sigurdur
authors.initials: S
authors.lastname: Sigurdsson
authors.forename: Thor
authors.initials: T
authors.lastname: Aspelund
authors.forename: Peter
authors.initials: P
authors.lastname: Kellman
authors.forename: Anthony H
authors.initials: AH
authors.lastname: Aletras
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Dyke
authors.forename: Gudmundur
authors.initials: G
authors.lastname: Thorgeirsson
authors.forename: Gudny
authors.initials: G
authors.lastname: Eiriksdottir
authors.forename: Lenore J
authors.initials: LJ
authors.lastname: Launer
authors.forename: Vilmundur
authors.initials: V
authors.lastname: Gudnason
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Arai
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D050197:Atherosclerosis / Q000150:complications; D016022:Case-Control Studies; D015331:Cohort Studies; D048909:Diabetes Complications; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D008279:Magnetic Resonance Imaging; D008297:Male; D009203:Myocardial Infarction / Q000150:complications / Q000175:diagnosis* / Q000401:mortality*; D015995:Prevalence; D011379:Prognosis; D012306:Risk