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Senior Citizen Health & Medicine
Like All Aging Body Parts the Heart Changes Shape,
Shrinks and Loses Function
Senior citizens see heart pumping slow up to five percent a
year
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 “It’s an amazing piece of the puzzle of heart
failure that finally singles out the effects of age over better-known
risk factors such as high blood pressure in otherwise healthy people and
regardless of race,” Susan Cheng MD |
|
Nov. 5, 2007 - Researchers at Johns Hopkins have
evidence from a study of older Americans to explain why the supposedly
natural act of aging is by itself a very potent risk factor for
life-threatening heart failure. They have found that for each year a
person ages, the time it takes for their heart muscles to squeeze and
relax grows longer by two to five percent.
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Health & Medicine |
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The study was presented yesterday at the American
Heart Association’s (AHA) annual Scientific Sessions in Orlando.
The Hopkins team analyzed more than a half-dozen
measurements of heart structure and pumping function to assess minute
changes in the hearts of 5,004 men and women, age 45 to 84, of different
ethnic backgrounds and with no existing symptoms of heart disease.
Test results were obtained from study participants
who had undergone high-tech magnetic resonance imaging of the heart -
tagged MRI - which measures individual muscle segment changes with each
heartbeat.
The findings, researchers say, offer insight into
the root causes of heart failure. They are especially valuable now as
millions of baby boomers in America move into their 60s, a time when
most signs and symptoms of heart problems first appear.
Estimates show that more than 5 million Americans
have some from of congestive heart failure, marked by symptoms such as
shortness of breath and fatigue.
“Our results demonstrate just how the heart plays a
losing game of catch-up as people age,” says Susan Cheng, M.D., a former
medicine resident at Hopkins who led the study.
“It’s an amazing piece of the puzzle of heart
failure that finally singles out the effects of age over better-known
risk factors such as high blood pressure in otherwise healthy people and
regardless of race.”
“We already knew that the heart is constantly
trying to adapt to risk factors, but now we know that this task gets
more difficult as the heart ages and loses a little bit of its pumping
capacity every year,” says Cheng, now a cardiology fellow in Boston.
She says the findings could lead to diagnostic
tests to identify those whose hearts are aging faster than others,
enabling preventive drug therapy, pacemakers, or lifestyle changes to
slow or even reverse the deleterious effects.
Hopkins cardiologist João Lima, M.D., the senior
study investigator, says effects of aging have been hard to determine
because of inherent flaws in using standard criteria to assess heart
function.
The current gold standard, he says, is the heart’s
ejection fraction, a ratio of the amount of blood pumped out with each
heartbeat to the total volume of blood available for pumping. An
ejection fraction of 50 percent to 65 percent is considered normal.
Study results showed that ejection fraction
actually rose by 0.01 percent with every year. But Lima calls this
figure misleading because the total amount of blood available for
pumping, the bottom number in the ratio, decreases as the size of the
heart cavity shrinks and heart walls thicken, falsely boosting test
results when heart function is actually failing.
 When researchers separated the numbers, the actual
amount of blood pumped out by the heart fell by 8 milliliters per year,
says Lima, an associate professor at The Johns Hopkins University School
of Medicine and its Heart Institute.
The flaw in using ratios, he notes, also helped to
mask the gradual shrinkage of heart muscle mass. Researchers found that
heart muscle mass declined by on average 0.3 grams per year. This
occurred even though heart wall thickness had expanded and despite an
increase in another standard measure of heart function, the ratio of
left ventricular mass to blood volume, which went up by 5 milligrams per
milliliter each year.
Lima says it’s important not to be misled by
existing tests for heart function, especially ejection fraction ratios,
when diagnosing patients.
He points out that almost half of the 550,000
Americans newly diagnosed each year with heart failure - mostly women
over age 50 - have a non-systolic form, in which the ejection fraction
appears the same, even though heart function is declining.
“Age could be the deciding factor in determining
who gets this kind of heart failure,” he says.
“This study highlights how the aging heart’s
anatomy and function change hand in hand over time, similar to arteries
stiffening, bones weakening from loss of calcium, and kidney function
declining,” says Lima.
“Physicians and patients need to recognize it as a
process that can be accelerated by risk factors or possibly slowed down
by healthy lifestyle choices and sound medical care.”
The next step, researchers say, is to look for
so-called biological markers, usually blood proteins, which can track
the effects of the aging process on heart shape and function and to
measure these markers, so that a test specific to aging of the
cardiovascular system can be developed.
Study participants from six centers across North
America were drawn from a larger pool of 7,000 ethnically diverse
adults, including African Americans, Chinese Americans, Caucasians and
Hispanics - all monitored to see who develops heart failure. Started in
2000, the Multiethnic Study of Atherosclerosis (MESA) is set to run for
another six years. It is the first large-scale analysis of racial or
ethnic differences in heart function. So far, 79 study participants have
developed congestive heart failure.
Editor's Notes:
Funding for this study comes from the National
Heart, Lung and Blood Institute, a member of the National Institutes of
Health.
Besides Lima and Cheng, other Hopkins investigators
involved in this study were Verônica Fernandes, M.D., Ph.D.; and David
Bluemke, M.D., Ph.D. In recognition of her research, Cheng is among the
finalists nominated to receive the distinguished Samuel L. Levine Award
for young investigators at the AHA conference.
(Presentation title: Age-Related Differences in
Left Ventricular Structure and Function, the Multiethnic Study of
Atherosclerosis.)
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