Investigators from Johns Hopkins looked at the performance and radiographic anatomy of the hearts of 5,004 men and women with no preexisting cardiac disease, ages 45 to 84, and found that age itself should be considered an independent risk factor for the development of congestive heart failure.
Researchers found that each year as people age, the time it takes for their heart muscles to squeeze and relax grows longer, by 2 percent to 5 percent.
Test results were obtained from study participants who had undergone high-tech magnetic resonance imaging of the heart – tagged MRI – which measures individual muscle segment changes with each heartbeat…
“Our results demonstrate just how the heart plays a losing game of catch-up as people age,” says Susan Cheng, M.D.
Susan Cheng, M.D., a former medicine resident at Hopkins who led the study. “It’s an amazing piece of the puzzle of heart failure that finally singles out the effects of age over better-known risk factors such as high blood pressure in otherwise healthy people and regardless of race.”
“We already knew that the heart is constantly trying to adapt to risk factors, but now we know that this task gets more difficult as the heart ages and loses a little bit of its pumping capacity every year,” says Cheng, now a cardiology fellow in Boston.
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 João 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 heart’s 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 it’s 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 year with heart failure – mostly women over age 50 – have a non-systolic form, in which the ejection fraction appears the same, even though heart function is declining. “Age could be the deciding factor in determining who gets this kind of heart failure,” he says.
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