Recent findings emphasize that a haplotype (HapK) confers a modest risk of myocardial infarction in European-Americans, but confers a three-fold larger risk in African-Americans, according to multi-center research from deCODE Genetics (www.decode.gom), Emory University, the National Cancer Institute, the Icelandic Heart Association, and others.
The HapK variation is found in 27% of the Icelandic population, only 6% of African-Americans, and is very rare in Africans. If genetics was the primary risk factor for myocardial infarctions, the risk for African-Americans would be significantly lower, Dr. Graves asserts.
Dr. Collins, however, says "that conclusion cannot be supported by existing scientific evidence. More than one genetic variation likely contributes to the risk of myocardial infarction and many of those genetic variations have yet to be discovered."
"The popular media represented that finding as a race-based factor for heart attack," Dr. Graves says, although the study's investigators explained clearly that the increased risk could be either genetic or environmental. The gene associated with HapK causes inflammation in arteries, which, in turn, is influenced by one's disease state, emotional state, and other factors.
The acknowledged poorer outcomes among African-Americans with heart failure were behind last June's FDA approval of BiDil for the treatment of heart failure in African-American patients.
As Manuel Worcel, M.D., CMO, NitroMed (www.nitromed.com), elaborates, studies showed "a stronger efficacy in African-Americans than in Caucasians, but it is not only effective in African-Americans."
The African-American Heart Failure Trial found that BiDil decreased the risk of mortality by 43% in African-Americans. Broader studies are being planned to identify why BiDil, administered with such background therapies as ACE inhibitors or beta blockers, is effective in this population and to determine whether it is also effective in other populations.
Experts have hypothesized that its effectiveness in an African-American population is based on its effectiveness against hypertension, the form of heart disease most common among African-Americans. Dr. Worcel says its success is based upon the fact that BiDil is a vasodilator with nitric oxide-enhancing properties. "Where genomics can play a role, I don't know.
"Be very careful in saying that genes determine things," Dr. Worcel cautions. "Humans have a way of getting around what our genes say." In heart disease, he suspects patients' environments play a pivotal role.