WINSTON-SALEM, N.C. –April 27, 2015 – Refining
the results of a 2013 study, researchers
have found that atrial fibrillation, or irregular heartbeat, is associated with
only one type of heart attack – the more common of the two types.
study, led by Elsayed Z. Soliman, M.D., director of the Epidemiological
Cardiology Research Center at Wake Forest Baptist Medical Center, is published
in the April 27 online issue of the American Heart Association journal Circulation.
fibrillation, or a-fib, is the most prevalent heart rhythm disorder, affecting
as many as 6 million Americans, and has long been known to be a risk factor for
stroke. The 2013 study led by Soliman was the first to show that a-fib also
increased the risk of heart attack, by 70 percent overall and by even higher
rates in women and African-Americans.
study sought to shed light on the mechanisms underlying the atrial
fibrillation-heart attack link by examining the association between a-fib and
the two types of heart attack. To accomplish this, Soliman and his team reviewed
the histories of 14,462 people who were part of the Atherosclerosis Risk in
Communities (ARIC) study, a National Heart, Lung and Blood Institute-funded research
project that began in 1987 and included follow-up through 2010. Their
investigation not only confirmed that atrial fibrillation increased the risk of
heart attack – by 63 percent overall, with a higher rate in women – but also
determined that this association was limited to the type of heart attack known
attacks are divided into two types according to the severity of cardiac muscle
damage. NSTEMI (non-ST segment elevation myocardial infarction) is the less
severe type, occurring when a blood clot partly clogs a coronary artery and
only a portion of the heart muscle supplied by that artery is damaged. A STEMI
(ST segment elevation myocardial infarction) heart attack happens when an
artery is completely blocked by the blood clot, which causes damage to
virtually all of the heart muscle supplied by that artery. Of the approximately
735,000 heart attacks recorded in the United States each year, roughly
two-thirds are NSTEMI.
said the finding that atrial fibrillation was associated only with NSTEMI heart
attacks suggests that factors contributing to partial blockage of the coronary
arteries or increased oxygen demand, such as sudden increase in heart rate, are
more likely to explain the association between a-fib and heart attack than
those factors linked to total blockage caused by the migration of a blood clot to
a coronary artery from the site of its formation.
results have important implications for management of the risk of heart attack
in people with atrial fibrillation,” Soliman said. “For example, blood thinners
that are commonly prescribed to people with a-fib to prevent stroke may not be
as effective in preventing heart attacks in this population.”
Atherosclerosis Risk in Communities Study was carried out as a collaborative
study supported by National Heart, Lung, and Blood Institute contracts HHSN268201100005C,
HHSN268201100006C, HHSN268201100007C, HHSN268201100008C, HHSN268201100009C,
HHSN268201100010C, HHSN268201100011C, and HHSN268201100012C, with additional
funds by grant 09SDG2280087 from the American Heart Association.
are Wesley T. O’Neal, M.D., and Zhu-Ming Zhang, M.D., Wake Forest Baptist; Faye
Lopez, M.P.H., Lin Y. Chen, M.D., Lindsay Bengston, Ph.D., and Alvaro Alonso,
M.D., Ph.D., University of Minnesota; Laura Loehr, M.D., Ph.D., University of
North Carolina at Chapel Hill; and Mary Cushman, M.D., University of Vermont.