CMRI Indicates Most Heart Attacks in Elderly May Go Unrecognized
Among test group, 17% had ‘unrecognized myocardial infarction;’ only 9.7% had been thought to have had MI
Sept. 5, 2012 – New research using cardiac magnetic resonance imaging suggests that many older people may have suffered
heart attacks that went undetected. The study compared the prevalence and prognosis of recognized and unrecognized myocardial infarction (MI)
diagnosed with CMR vs. electrocardiography (ECG) in older diabetic and non-diabetic participants.
Using CMR imaging among older adults in Iceland, researchers estimated the prevalence of unrecognized heart attacks,
which is associated with an increased risk of death, according to a study in the September 5 issue of the Journal of the American Medical
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“The prevalence and prognosis of unrecognized myocardial infarction (MI; heart attack) in older people with and without
diabetes may be higher than previously suspected in population studies.
“Advances in MI detection, such as cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement (LGE), are
more sensitive than prior methods. Ascertaining the prevalence of unrecognized MI (UMI) in these groups is relevant because age and diabetes
increase the risks of coronary heart disease," according to background information in the article.
'Pathologic studies indicate that subclinical coronary plaque rupture occurs frequently, particularly in diabetic
individuals, which may culminate in a high prevalence of UMI.”
Erik B. Schelbert, M.D., M.S., of the National Institutes of Health, Bethesda, Md., and colleagues conducted a study to
compare the prevalence and prognosis of recognized and unrecognized MI diagnosed with CMR vs. electrocardiography (ECG) in older diabetic and
From a community-dwelling group of older individuals in Iceland, data for 936 participants ages 67 to 93 years were
analyzed, including 670 who were randomly selected and 266 with diabetes. The median (midpoint) age was 76 years, and 52 percent of the
participants were women.
A total of 91 of 936 participants (9.7%) had “recognized myocardial infarction” (RMI), and the CMR found that 157 (17%)
had “unrecognized myocardial infarction (UMI).
Those with diabetes had a higher prevalence of UMI found by CMR than those without diabetes (72 participants - 21%, vs.
85 participants - 145%).
The cardiac magnetic resonance, which detected 157 (17%) of the previously undetected heart attacks, was more successful
than the use of ECG, which found only 46 (5%) with UMI.
“In the randomly sampled cohort (670), 61 participants (9%) had RMI and 97 (14%) had UMI by CMR whereas only 35 (5
percent) had UMI by ECG, significantly less than UMI by CMR,” the authors write.
MI that went unrecognized by CMR was associated with atherosclerosis risk factors, coronary calcium, coronary
revascularization, and peripheral vascular disease.
Over a median follow-up of 6.4 years, 30 of 91 participants with RMI died (33%), and 44 of 157 with UMI by CMR died (28%
percent), which were both significantly higher rates than the 17 percent with no MI who died (119/688).
After adjusting for age, sex, diabetes, and RMI, UMI by CMR remained associated with mortality (absolute risk increase,
8%), but UMI by ECG was not associated with mortality (absolute risk increase, -2%).
The researchers add that they observed more use of aspirin, β-blocker, and statin medications in those with UMI found by
CMR compared with those without MI.
“Yet the use of cardiac medications was significantly less in those with UMI compared with those with RMI. Roughly half
of those with UMI were taking aspirin, whereas less than half were taking statins or β-blockers.”
The authors suggest that several factors may contribute to the high prevalence of UMI.
“First, subclinical coronary plaque rupture occurs frequently, particularly in diabetic individuals. Cardiac magnetic
resonance may detect the myocardial sequelae of coronary plaque rupture or coronary plaque erosion that either spontaneously reperfused or
“Second, symptom variation in acute MI may lead patients or their clinicians to attribute MI symptoms to noncardiac
‘Third, given their propensity to be clinically detected, RMI may be more severe than UMI and impart greater lethality.”
The researchers also say, “This investigation also suggests limitations in current prevention strategies. Herein we
report a burden of MI in community-dwelling older individuals that is higher than previously appreciated.
“The burden of UMI was higher than the total burden of recognized MI, and prescription of cardioprotective medications
was less than for participants with RMI.
‘The high prevalence of MI specifically in individuals with diabetes confirms their increased vulnerability. Less than
one-third of those with UMI by CMR had prior revascularization to establish coronary disease and trigger secondary prevention strategies.
Detection of UMI by CMR may provide an opportunity to optimize treatment for these vulnerable individuals, but further study is needed to
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