Silent heart attacks—also known as unrecognized myocardial infarctions (MI)—that show up only on magnetic resonance imaging (MRI) are associated with an increased risk of death over the long term compared with recognized MI, researchers are reporting. Their study contributes to growing evidence that these silent heart attacks are not benign and should be taken seriously.
The study, part of the ICELAND MI cohort study, included 935 community-dwelling older people in Iceland. Those unaware of MI until baseline cardiac MRI had the same 3 percent risk of death at 3 years as peers without any MI, while both groups were at lower risk than patients with a known history of MI. After 10 years, the risk of death increased for those with silent heart attacks, nearly equaling the 10-year mortality risk for those with clinically diagnosed (recognized) heart attacks. At that point, 30 percent of those who had no MI at baseline had died, compared to 49 percent of those with unrecognized MI and 51 percent of those with recognized MI.
"Being more prevalent than recognized MI, unrecognized MI constitutes an underappreciated public health problem," wrote study co-author Andrew Arai, MD, chief of the Advanced Cardiovascular Imaging Laboratory at NHLBI, and his colleagues. "Whether early detection of unrecognized MI by cardiac MRI could allow for the institution of risk factor management and thus reduce the associated long-term risks merits further investigation." The study, partly funded by NHLBI, appeared in JAMA Cardiology.