WINSTON-SALEM, N.C. – Genes play a significant role in heart function, and may partly determine who develops the most common form of heart failure, report researchers from Wake Forest University Baptist Medical Center and colleagues in this month's Hypertension, a journal of the American Heart Association. "We asked the question what determines differences in heart function from person to person," said Dalane W. Kitzman, M.D., a cardiologist from Wake Forest. "We found a significant portion is actually determined by your genes – who is your mother and father. Gene influences were as powerful or even more so than blood pressure level, age, gender, weight, where you live or whether you have diabetes."
Also participating in the research were the University of Minnesota, Boston University School of Medicine, University of Alabama-Birmingham, University of Utah, Washington University School of Medicine and Weill Medical College of Cornell University. In their study of 574 groups of siblings, the researchers used ultrasound to measure how efficiently participants' hearts refilled with blood after each squeezing heart beat. They found that family relationships explained a significant portion – as much as half – of variability in the heart's filling, which is known as diastolic function. This was the first study to examine the relationship between heart function and heart structure within family members.
"Our research suggests that when you're born your diastolic function may already be programmed," said Kitzman. "A significant part of whether you have good, moderate or poor diastolic function may be determined by genes."
Significantly impaired diastolic function is associated with hypertension, coronary artery disease and the most common type of congestive heart failure. The study included primarily persons with hypertension – it is known that many such patients eventually develop congestive heart failure. The researchers speculate that the effects of genes, longstanding hypertension, and aging could combine to set the stage for diastolic heart failure. In other cases, abnormal filling can directly cause heart failure, which could also be influenced by genes.
With diastolic heart failure, the heart does not fill completely with blood. The most common symptom is shortness of breath. "It's a relatively new concept that there may be a genetic component to heart failure," said Kitzman. "We previously thought that diastolic heart failure was caused by hypertension and aging. It is now becoming clear that those two factors don't explain it all – a genetic component may be equally important."
The study was part of the Hypertensive Genetic Epidemiology Network Study (HyperGen), which aims to identify the genetic contributions to hypertension. Participants were enrolled at four centers: Minneapolis, Minn., Salt Lake City, Utah, Forsyth County, N.C., and Birmingham, Ala. The researchers are now analyzing the participants' DNA in hopes of identifying genetic regions responsible for diastolic function. In the United States, about 5 million people have heart failure and an additional 550,000 are diagnosed with it annually. It is one of the largest health problems in the developed world.
In previous research of older adults living in four U.S. communities, Kitzman and colleagues showed that more than half of those with heart failure had diastolic heart failure. Among women with heart failure, 67 percent had diastolic failure, compared to 42 percent of men. The other type of heart failure, systolic heart failure, is caused by a weakened heart muscle that prevents it from pumping enough blood. With both types, the body doesn't get enough oxygenated blood to meet its needs.
The standard treatments for systolic heart failure include water pills and medications that cause the blood vessels to widen or increase the force of the heart's contractions. The diastolic form of heart failure has been recognized as a separate condition only recently, so there has been little research into its treatment. Researchers at Wake Forest are currently conducting several research studies on the most effective treatments for diastolic heart failure.
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