Parental Atrial Fibrillation Increases Risk in Offspring,
Finds NHLBI’s Framingham Heart Study
Having a parent with atrial fibrillation (AF) strongly
increased an offspring’s risk of developing
this heart rhythm disorder, according to a study of
participants in the National Heart, Lung, and Blood
Institute’s (NHLBI) Framingham Heart Study.
The risk doubled for offspring with at least one parent
with AF compared to offspring whose parents did not
have the condition. The study of 2,243 adults, published
in the June 16 issue of The Journal of the American
Medical Association, is the first to find a genetic
connection for AF in a community sample.
“This important research finding will need to
be confirmed but it opens up a new avenue of research
on atrial fibrillation. Now scientists can start looking
at genetic factors that might contribute to AF –
searching for the genes involved in this increasingly
common disorder,” said Barbara Alving, M.D.,
acting director of the NHLBI, one of the components
of the National Institutes of Health.
The study’s findings strongly support the notion
that AF has genetic underpinnings. Most cases of AF
occur in older people. The disorder affects about
1 in every 10 persons aged 80 and over. In the new
study, the risk of AF tripled when both parents and
the offspring were under age 75. The risk also tripled
when the analysis was limited to offspring who had
no clinically apparent heart disease.
“Disorders with a genetic component often occur
at a younger age or in the absence of major diseases
like heart disease that trigger the condition,”
said the study’s lead investigator Caroline
Fox, M.D. M.P.H., of the Framingham Heart Study.
Atrial fibrillation is the most common heart rhythm
disorder in the U.S., affecting more than 2 million
adults. The prevalence of the condition is rising
and scientists predict that about 5.6 million Americans
will have the disorder by 2050. Known causes of AF
include abnormalities in the heart’s structure
and long-term uncontrolled high blood pressure.
AF occurs when electrical signals in the heart's upper
chambers (the atria) are fired in a very fast, uncontrolled
manner. Electrical signals then arrive in the heart's
lower chambers (the ventricles) in an erratic pattern,
creating an irregular heartbeat and affecting the
heart’s ability to pump blood. Atrial fibrillation
can produce symptoms including palpitations, an unexplained,
rapid heartbeat, lightheadedness, or occasionally
chest pain. It can also be asymptomatic. AF can lead
to complications such as stroke and congestive heart
failure. Treatment via drugs, surgery or devices,
is designed to slow the heart rate and/or restore
normal rhythm, and to prevent stroke. Blood-thinning
medications (anticoagulants) are an important means
of preventing stroke in AF patients.
The Framingham Offspring study of AF involved 1165
women and 1078 men whose parents were members of the
“original” Framingham Heart Study. The
offspring were at least 30 years of age and free of
atrial fibrillation at the first exam. Offspring and
original study participants had routine clinic exams,
including physical examinations, interviews, lab tests,
and electrocardiograms.
AF in both offspring and original “parental”
participants was confirmed by an electrocardiogram.
Parental cases occurred from 1949-2002 and offspring
AF cases occurred from 1983-2002.
When the Framingham researchers analyzed the data,
they found that 30 percent of participants had at
least one parent with AF. Seventy offspring (23 women)
developed AF during the study at a mean age of 62
years. When stated in terms of 1000 persons per year,
the results indicate that the number of offspring
developing AF would be 4.5 if a parent had AF and
3 if parents did not have AF.
Fox cautioned that the Framingham findings should
not alarm people who have a parent with AF. “AF
with or without a family history is a common condition
in the elderly. Our findings indicate to the scientific
community that we need more research on the genetic
mechanisms of AF and how they interact with environmental
influences,” she said.
Fox added that Framingham scientists hope to conduct
further research into the genetic basis of AF.
Study limitations, noted Fox, include the small number
of offspring cases of AF and a predominantly Caucasian
group of participants.
To interview Dr. Fox about this study, please call
the NHLBI Communications Office at 301-496-4236 or
e-mail
NHLBInews@nhlbi.nih.gov.
NHLBI is part of the National Institutes of Health
(NIH), the Federal Government’s primary agency
for biomedical and behavioral research. NIH is a component
of the U.S. Department of Health and Human Services.
NHLBI press releases and fact sheets, including a
fact sheet on arrhythmias, can be found online at
www.nhlbi.nih.gov. |