Unrecognised myocardial infarction (UMI) may be more prevalent than previously suspected.  Although several population studies have described the prevalence of UMI based on ECG findings, this method has limited sensitivity.  Cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement has been extensively validated for the detection of myocardial infarction.  The aim of this study was to determine the prevalence and prognosis of recognised and unrecognised MI diagnosed with CMR in a elderly population, and to compare these findings with the use of ECG.

Data from 936 individuals (aged 67 to 93 years) from a community-dwelling cohort of older individuals in Iceland were analysed; 670 were randomly selected, and 266 had diabetes.  The main outcome measures were the prevalence and mortality of MI up until September 2011.

91 of the 936 (9.7%) participants where known to have had an MI (recognised MI (RMI)).  157 patients had UMI detected by CMR (17%), which was more prevalent than the 46 UMI detected by ECG (5%; P<.001).  Amongst those with diabetes (n=337), UMI was more commonly detected by CMR than ECG (21% vs. 4%; P<.001).  Over a median of 6.4 years, 33% of participants with recognised MI died, and 28% with unrecognised MI died; both of these were higher than the 17% of patients with no MI who died.  Unrecognised MI by CMR improved risk stratification for mortality over RMI, and after adjusting for age, sex, and a history of MI, UMI by CMR remained associated with mortality and significantly improved risk stratification for mortality, however UMI as detected by ECG did not.

Conclusions:

In this community study of older individuals, the prevalence of unrecognised MI on cardiac MRI was higher than the prevalence of recognised MI and was associated with increased mortality risk.

• Schelbert EB, Cao JJ, Sigurdsson S et al.  Prevalence and Prognosis of Unrecognized Myocardial Infarction Determined by Cardiac Magnetic Resonance in Older Adults.  JAMA 2012;308:890-897.