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 Joo 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 hearts 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 its 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
|Contact: David March|
Johns Hopkins Medical Institutions