Association of Unrecognized MI With Long-Term Outcomes
What are the long-term outcomes of unrecognized myocardial infarction (UMI) detected by cardiac magnetic resonance (CMR) compared with clinically recognized myocardial infarction (RMI) and no myocardial infarction (MI)?
The investigators assessed 935 participants of the population-based, prospectively enrolled ICELAND MI cohort study (patients aged 67-93 years) with CMR at baseline (from January 2004-January 2007) and followed up for up to 13.3 years. The primary outcome was all-cause mortality. Secondary outcomes were a composite of major adverse cardiac events (MACE: death, nonfatal MI, and heart failure). 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.
Of 935 participants, 452 (48.3%) were men; the mean (standard deviation) 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 < 0.001). After adjusting for age, sex, and diabetes, UMI by CMR had an increased risk of death (hazard ratio [HR], 1.61; 95% confidence interval [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) versus RMI.
The authors concluded that all-cause mortality of UMI was higher than no MI, and within 10 years from baseline, evaluation was equivalent with RMI.
This study reports that UMI by CMR had higher rates of death, nonfatal MI, and heart failure than no MI at 10-year follow-up. Furthermore, after an initial period of relative quiescence, the UMI mortality rate increased substantially, catching up to RMI mortality. Since UMI is more prevalent than RMI, UMI appears to be an unrecognized public health challenge. Whether an expensive test like CMR provides incremental value over an electrocardiogram for diagnosis of UMI and whether appropriate risk factor management may ameliorate the associated long-term risks of UMI needs further study.
Keywords: Acute Coronary Syndrome, Diagnostic Imaging, Electrocardiography, Geriatrics, Heart Failure, Magnetic Resonance Imaging, Myocardial Infarction, Myocardial Ischemia, Outcome Assessment (Health Care), Risk Factors, Secondary Prevention
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