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Wednesday, July 19, 2006
Mayo Clinic Study Suggests Emergence of New Most Common Form of Heart Failure
ROCHESTER, Minn. -- Data from a 15-year period show that the prevalence of a particular type of heart failure -- heart failure with preserved ejection fraction, also known as diastolic heart failure -- is increasing. This type of heart failure now accounts for more than half of heart failure cases, according to Mayo Clinic research published in the July 19 issue of the New England Journal of Medicine. An editorial accompanies this research, as well as another study on the same topic.
Nearly 5 million Americans are living with heart failure. Heart failure refers to symptoms of shortness of breath, exercise intolerance and fluid retention, which occur when heart function is impaired.
Heart failure may be associated with reduced pumping function as measured by the ejection fraction (systolic heart failure) or reduced relaxing function with preserved ejection fraction (diastolic heart failure). These two types of heart dysfunction cause exactly the same symptoms. Measurement of heart function, usually with an echocardiogram, is needed to distinguish between the two forms of heart failure.
The Mayo study indicates that now more than half of heart failure cases are due to diastolic heart failure. Of note, diastolic heart failure disproportionately affects women, particularly elderly women.
"These data confirm that heart failure with preserved ejection fraction, also know as diastolic heart failure, is a growing concern," says Margaret Redfield, M.D., lead author of the study and director of Mayo Clinic's Heart Failure Clinic. "Nearly all previous studies of therapies for heart failure have excluded patients with diastolic heart failure. This type of heart failure is poorly understood. It is possible that therapies for this type of heart failure will need to be very different from those which are of benefit in systolic heart failure."
The proportion of heart failure cases caused by diastolic heart failure increased from 38 percent to 47 percent to 54 percent in three consecutive five-year periods during a study of 4,596 patients who were discharged with a heart failure diagnosis at the two Mayo Clinic hospitals in Olmsted County, Minn., from 1987 through 2001. Among heart failure patients, the prevalence of diseases that cause diastolic heart failure and worsen its symptoms -- including hypertension, atrial fibrillation and diabetes -- also increased over the study period.
The increase in the proportion of diastolic heart failure was due to increases in the number of diastolic heart failure cases with no change in the number of systolic heart failure cases. On average, mortality rates for the two forms of heart failure were very similar. Importantly, while improvements in survival rates over the study period were seen for systolic heart failure, no such improvement was observed for diastolic heart failure, Dr. Redfield says.
"There are a number of likely reasons why patients with systolic heart failure are doing better," she says. "Research has helped us discover many therapies for systolic heart failure -- drugs, devices and surgical procedures -- to counteract the mechanisms that cause or worsen systolic heart failure, and we've seen the proven benefit of those therapies in large scale clinical trials. This approach now needs to be expanded to the other half of the heart failure epidemic, patients with diastolic heart failure."
Co-authors of the paper are Theophilus Owan, M.D.; David Hodge, M.S.; Regina Herges; Steven Jacobsen, M.D., Ph.D.; and Veronique Roger, M.D., M.P.H.
Source / Credit: Mayo Clinic
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