Evidence now exists, researchers at Johns Hopkins
report, to support a dramatic change in the way hundreds of
thousands of Americans with a form of heart failure should
be treated.
In a follow-up to previous work, Hopkins cardiologists
say that patients with nonsystolic heart failure may
benefit more from pacemakers to speed up the heartbeat
rather than from continual long-term use of beta blockers,
drugs that slow down the heartbeat.
It is estimated that almost half the 550,000 Americans
newly diagnosed each year with heart failure have the
nonsystolic form.
"Cardiologists are constantly being forced to rethink
heart failure because one size does not fit all," said
senior study investigator David Kass, the Abraham and
Virginia Weiss Professor of Cardiology at the School of
Medicine and its
Heart Institute. "We really have to be careful about
how we diagnose and approach its treatment.
"We also need to understand all facets and
manifestations of the disease because we are seeing
ever-increasing numbers of older adults who have heart
failure, mostly women over age 50, whose heart pumping
appears to be normal. And their cases are clearly different
from traditional, systolic heart failure, where pumping
function is depressed. However, almost all of the research
over the last three decades has applied only to those with
systolic heart failure," Kass said.
Nonsystolic heart failure is characterized by fairly
normal function of the heart's pumping action, or so-called
ejection fraction, when a person is at rest. This action
falters, however, once daily physical activity begins and
the heart becomes increasingly unable to squeeze out
sufficient blood flow to energy-starved muscles. Even
small tasks, such as getting dressed in the morning, can
leave people exhausted and short of breath. Until now, Kass
noted, researchers had thought the problem was that these
hearts could simply not relax properly, a
so-called failure of their diastolic function.
The Hopkins team plans to launch within the next year
a national study of the use of pacemakers in patients with
this form of the disorder, which is sometimes referred to
as heart failure with preserved ejection fraction or as
heart failure with normal ejection fraction.
In some cases, a combination of drug and device may
work best to control the disease, speeding up the heartbeat
at times, slowing it down at other times.
The latest report from the Johns Hopkins team,
published in the journal Circulation online Nov. 6,
follows presentation of its initial findings at last year's
Scientific Sessions of the American Heart Association.
People with the more common, systolic form of the
disease have a pumping function that is evenly depressed
and weakened at all times, not just with exercise or
activity. Beta blockers have been proven widely effective
in minimizing the stresses placed on the failing heart
during physical activity, when the body needs to more
quickly squeeze out blood to the rest of the body.
The Johns Hopkins study is believed to be one of the
first to do a head-to-head comparison of those with
nonsystolic heart failure and patients with similar medical
histories — including high blood pressure, a
relatively high ejection fraction and overgrown hearts
— but no major symptoms of heart failure. The group
studied was relatively small, Kass said, and involved
mostly African-Americans from the Baltimore region.
Nineteen older men and women with initial symptoms of
nonsystolic heart failure were compared to 17 patients with
no early signs of the disease. African-Americans are at
particular risk for this kind of nonsystolic heart
failure.
When all pedaled at increasing levels on a stationary
bike, their hearts filled with blood in a similar way.
However, heart function quickly differed in two key
measures that explained why those with nonsystolic heart
failure could not exercise.
Hearts of participants in the nonsystolic group failed
to keep up, beating on average 44 percent less quickly
during exercise than those of participants without heart
failure. Also during exercise, blood vessels in the heart
failure group did not dilate or expand as much to meet the
increased energy demands from the body's muscles. The
corresponding resistance to blood flow dropped 28 percent
in controls as blood vessels relaxed but dropped only 19
percent in the heart failure group.
In their planned study next year, the Johns Hopkins
scientists will monitor more than 80 men and women with
mild to moderate nonsystolic heart failure. Half will be
taking traditional beta blocker medications, the most
commonly prescribed treatment, while the rest will not. All
will be implanted with a pacemaker and perform exercise
tests to see if their symptoms get better — or are
possibly even reversed.
If the new study validates the preliminary work, Kass
predicts that his research could change the practice
guidelines about how beta blockers and pacemakers are used
in this form of heart failure.
The American Heart Association estimates that more
than 5 million Americans have some form of congestive heart
failure, marked by symptoms such as shortness of breath and
fatigue.
Funding for the reported study was provided by the
National Institutes of Health and the Peter Belfer
Laboratory Foundation. Other researchers were Barry Borlaug
(lead), Vojtech Melenovsky, Laura Shively, Kristy Swigert
and Lewis Becker.
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