Researchers at Johns Hopkins have reported evidence 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 patients with non-systolic 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 of the 550,000 Americans newly diagnosed each year with heart failure have the non-systolic form.
"Cardiologists are constantly being forced to rethink heart failure because one size does not fit all," says senior study investigator David Kass, M.D., a professor at The Johns Hopkins University 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 says.
Non-systolic 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 notes, researchers had long 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 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 Hopkins team, to be published in the journal Circulation online Nov. 6, follows presentation of their 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 Hopkins study is believed to be one of the first to do a head-to-head comparison of those with non-systolic 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 says, and involved mostly African Americans from the Baltimore region: Nineteen older men and women with initial symptoms of non-systolic heart failure were compared to 17 patients with no early signs of the disease. African Americans are at particular risk for this kind of non-systolic 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 non-systolic heart failure could not exercise.
Hearts of participants in the non-systolic 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 only dropped 19 percent in the heart-failure group.
In their planned study next year, the Hopkins scientists will monitor more than 80 men and women with mild to moderate, non-systolic 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 their 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 from 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 involved in this study, conducted solely at Hopkins, were lead researcher Barry Borlaug, M.D.; Vojtech Melenovsky, M.D., Ph.D.; Laura Shively, R.N., B.S.N; Kristy Swigert, R.N., B.S.N.; and Lewis Becker, M.D. Kass is also the Abraham and Virginia Weiss Professor of Cardiology at Hopkins.
Materials provided by Johns Hopkins Medical Institutions. Note: Content may be edited for style and length.
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