Unrecognized MI, identified through cardiac magnetic resonance, or CMR, conferred similar rates of all-cause mortality vs. recognized MI within 10 years, as well as increased risk for nonfatal MI and HF compared with no MI, according to a study published in JAMA Cardiology.
“In a cohort of community-dwelling, elderly individuals, [unrecognized] MI by CMR had higher rates of death, nonfatal MI and heart failure than no MI at 10-year follow-up,” Tushar Acharya, MD, of the NHLBI, and colleagues wrote. “After an initial period of quiescence, the [unrecognized] MI mortality rate increased substantially, catching up to [recognized] MI mortality.”
To investigate the long-term outcomes of unrecognized MI compared with recognized MI and no MI, researchers conducted the ICELAND MI study from 2004 to 2006, using a subset of the AGES-Reykjavik prospective cohort (n = 935; mean age, 76 years; 52% women; 17% with unrecognized MI; 10% with recognized MI).
Participants were categorized as having recognized MI, unrecognized MI or no MI.
The primary outcome was all-cause mortality. Secondary outcomes included major adverse cardiac events (defined as mortality, MI and HF), nonfatal MI and HF.
Participants were followed for up to 13.3 years. During this time, there were 424 deaths.
Researchers found that, at 3 years, mortality rates were not significantly different between the unrecognized MI group and the no MI group (3% for both) and were lower than the recognized MI group (9%).
At 5 years, mortality rates increased in the unrecognized MI group and were higher than the no MI group (13% vs. 8%), but remained lower than the recognized MI group (19%).
By 10 years, the mortality rate in the unrecognized MI group was 49%, higher than the 30% in the no MI group (P <.001) and similar to the recognized MI group (51%).
After the researchers adjusted for age, sex and diabetes, it was determined that, at 10 years, compared with no MI, unrecognized MI conferred increased risk for death (HR = 1.61; 95% CI, 1.27-2.04), major adverse cardiac events (HR = 1.56; 95% CI, 1.26-1.93), MI (HR = 2.09; 95% CI, 1.45-3.03) and HF (HR = 1.52; 95% CI, 1.09-2.14).
Furthermore, the risk for death (HR = 0.99; 95% CI, 0.71-1.38) and major adverse cardiac events (HR = 1.23; 95% CI, 0.91-1.66) in unrecognized MI was not statistically different compared with recognized MI at 10 years.
“Being more prevalent than [recognized] MI, [unrecognized] MI constitutes an underappreciated public health problem,” the researchers wrote. “Whether early detection of [unrecognized] MI by CMR could allow for the institution of risk factor management and thus reduce the associated long-term risks merits further investigation.”
Robert O. Bonow
CMR identifies smaller MIs
In a related editorial, Robert O. Bonow, MD, MS, MACC, Max and Lilly Goldberg Distinguished Professor of Cardiology and professor of medicine at Northwestern University Feinberg School of Medicine and past president of the American Heart Association, wrote: “It is noteworthy that the prevalence of [recognized] MI in the Rotterdam Study and the prevalence in the current Icelandic study are quite similar (11.4% and 10%, respectively), but the prevalence of [unrecognized] MI was considerably lower in the Rotterdam Study (6% compared with 17%, respectively). Thus, Acharya et al show that [unrecognized] MI has a higher prevalence than [recognized] MI, which was not the case in the Rotterdam study. This is presumably because CMR identifies smaller MIs than are detectable by electrocardiography, a finding that has been shown in numerous previous reports. The current study also has the advantage of assessing infarct size and left ventricular function, and indeed individuals with [unrecognized] MI have smaller infarct sizes, less LV remodeling and higher LV ejection fractions than those with [recognized] MI.” – by Melissa J. Webb
Disclosures: Acharya and Bonow report no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.