Heart Pumping Variation Found in Racial Groups
Weaker contractions in black Americans could explain their higher heart-disease rates, study says
MONDAY, March 26, 2007 (HealthDay News) -- The hearts of black Americans contract at a slightly weaker rate than other racial groups, the first large-scale study of its kind has found.
The discovery could help to explain why black Americans experience heart failure at higher rates than other groups of Americans, and could lead to new treatments, the study authors said.
The researchers, from Johns Hopkins University School of Medicine, said muscle contraction in three main regions of the heart was 1 percent to 3 percent weaker in seemingly healthy blacks than in other groups of people.
Conversely, the study also found that Chinese Americans' hearts had a small but consistently stronger squeezing action, said Dr. Veronica Fernandes, a postdoctoral research fellow and lead author of the report.
"We know that African Americans have more hypertensive disease," Fernandes said, referring to high blood pressure. "They have hypertrophied ventricles (thickened heart chambers) compared to Chinese Americans."
The finding could be important in medical treatment of black Americans, she said. "We could detect early clinical disease in people who are asymptomatic and treat them more aggressively," Fernandes said.
The researchers were to present the findings of the study -- called the Multiethnic Study of Atherosclerosis -- Monday at the American College of Cardiology annual meeting, in New Orleans.
The conclusions could be controversial -- as controversial as a 2005 decision by the U.S. Food and Drug Administration to approve a drug for high blood pressure specifically for black Americans. Yet the differences in heart performance uncovered by the study were found regardless of age, gender or presence of risk factors such as high blood pressure, the researchers reported.
MESA includes nearly 7,000 Americans ages 45 to 84 of different racial and ethnic backgrounds with no symptoms of heart disease. They are monitored for development of heart failure, which is a decline in the heart's ability to pump blood. Among the participants, 1,100 had special magnetic resonance imaging (MRI) scans that showed three-dimensional images of the heart that allowed tracking of heartbeat abnormalities.
The researchers have measured more than a dozen heart factors, including thickness of the heart wall, pumping volume, contraction of the heart muscle and risk factors such as high blood pressure.
Muscle contraction in the regions of the heart fed by its three main arteries was found to be weaker in black Americans than in other racial groups. On average, contraction of the anterior front heart wall was 17.5 percent in blacks, 18.5 percent in whites and 19.6 percent in Chinese Americans. Similarly, the posterior heart contracted 12.4 percent in black Americans, compared to 15 percent in Chinese Americans.
"Our results show that genetic and racial factors are clues that can be used in early identification of those more vulnerable to coronary artery disease, heart failure, arrhythmias and sudden cardiac death," said Dr. Joao Lima, associate professor of medicine and radiology at Hopkins and a senior study investigator.
If later MESA results find that weakened contraction is associated with an increased incidence of heart disease and death, periodic MRI scans or echocardiograms might be performed for early detection of problems in black Americans, Fernandes said.
For more about heart failure and its management, visit the American Heart Association.