A study of patients with life-threatening symptoms of heart failure showed that one-half had a little-understood form of the disorder, report researchers from Wake Forest University Baptist Medical Center in this week's New England Journal of Medicine.
"There's very little information about how to treat problems with the filling of the heart's main pumping chamber, the type of heart failure half of these patients had," said William C. Little, M.D., chief and professor of cardiology at WFUBMC. "Our study emphasizes how common this disorder may be and the need for additional research to determine the best therapy."
Doctors previously believed that most heart failure was a weakening of the heart muscle that kept it from pumping enough blood (systolic heart failure). In recent years, however, they have recognized a second form of the disorder: the heart can empty normally, but doesn't fill with enough blood (diastolic heart failure). The result is the same - the body does not get enough oxygen-rich blood for its needs. The most common symptom is shortness of breath.
For the study, Little and colleagues evaluated 38 patients who were admitted to the hospital with severe shortness of breath because of fluid buildup in their lungs - a life-threatening symptom of heart failure. All of the patients also had high blood pressure.
To determine which type of heart failure the patients had, the researchers used ultrasound technology to measure - both before and after treatment - the percentage of blood the heart emptied with each beat. A normal heart can pump 50 percent or more of its volume with each beat.
The researchers theorized that in patients with systolic heart failure, the measurement, called the ejection or emptying fraction, would improve after treatment. In patients with diastolic failure, there would be no change in the emptying fraction because their dysfunction was in filling the heart.
"This was the first study to measure the emptying fraction both before and after treatment so we would know what caused the problem," said Little. "Standard protocol is to measure the emptying fraction after treatment, and if the heart pumps normally, it is possible that the emptying had improved because of the patient's treatment."
In contrast, the WFUBMC study found that the emptying of the main pumping chamber was equally good during the acute problem and after treatment.
Currently, diastolic heart failure is treated with the same drugs used to treat systolic failure. But physicians don't know what treatments are best because little research has been done on diastolic heart failure.
"Heart failure is the number one cause of hospitalization for people age 65 and older in the United States," said Dalane W. Kitzman, M.D., associate professor of cardiology, and one of the study's co-authors. "Yet for one type, we don't know a lot about how to treat it and how the disease progresses." Little said the WFUMBC study shows that diastolic heart failure is a common cause of pulmonary edema (fluid in the lungs) and needs more attention. WFUBMC is currently conducting five studies to evaluate several drugs (ACE inhibitors and angiotensin receptor blockers) and exercise as treatments for the disorder. The currently reported study was supported by the National Institute on Aging, as are two of the ongoing studies.
In the United States, about 5 million people have heart failure and an additional 450,000 are diagnosed with it annually. It is one of the largest health problems in the developed world.
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Journal
New England Journal of Medicine