Generally healthy African Americans may be at higher risk of heart failure because of racial variations in heart muscle's pumping ability, a Johns Hopkins study suggests.
Scientists have known for nearly a decade that African Americans have higher rates of hospitalization for heart failure than other major U.S. racial or ethnic groups, but until now they have had limited information other than socio-economic and demographic characteristics to explain why this is so.
In what is believed to be the first, large-scale analysis of racial or ethnic differences in certain kinds of heart function, a team of Hopkins cardiologists found that muscle contraction in three main regions of the heart was on average weaker by 1 percent to 3 percent in African Americans, regardless of age, gender or existing risk factors, such as high blood pressure.
The Hopkins findings are among the first conclusions to emerge from the long-term Multiethnic Study of Atherosclerosis, or MESA for short. MESA is monitoring nearly 7,000 men and women, age 45 to 84, of different ethnic backgrounds and with no existing symptoms of heart disease to determine who develops heart failure and dies from it, and who does not.
In the study, to be presented March 26 at the American College of Cardiology's annual Scientific Sessions in New Orleans, the Hopkins team also found that Chinese Americans, hearts had a consistently, if mildly stronger squeezing function, of a similar magnitude than those of other racial or ethnic groups.
Researchers say that heart disease among Chinese Americans is less of a problem than in African Americans, although there is yet no direct evidence of a protective effect of stronger contraction in Chinese Americans.
Another surprise finding was that hearts in Chinese Americans contract more quickly than those of other ethnic groups. Three of four heart walls were fully squeezed on average 20 milliseconds to 30 milliseconds faster than in Hispanics, and were more than 10 milliseconds faster than in either African Americans or Caucasians.
According to senior study investigator and cardiologist Jo'o Lima, M.D., M.B.A., "even without showing symptoms, people can still be at risk of having heart trouble. And a slower or faster heartbeat is not normal."
"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, or those in more need of early treatment - or those at less risk and less likely to need early intervention."
Lima, an associate professor of medicine and radiology at The Johns Hopkins University School of Medicine and its Heart Institute, says MESA has already confirmed for both men and women that changes in one particular region of the heart - the top, front wall of the left ventricle - were linked to the greatest declines in heart function. (For details on that report, go to http://www.hopkinsmedicine.org/Press_releases/2005/08_22_05.html .)
Nearly all participants in the MESA study had an initial cardiac magnetic resonance imaging test, and more than 1,100 participants in the six-city investigation had a special, so-called tagged MRI performed. Developed at Hopkins, the computer program better analyzes three-dimensional, computer images of each heart and can track gradual abnormalities during each heartbeat.