African-American women & heart health.

Although death rates from cardiovascular disease have dropped in the general population over the past 30 years, they've remained fairly steady among African Americans, particularly African-American women.

There are numerous reasons for the higher incidence of mortality from cardiovascular disease in African Americans, including economic issues, access to medical care and lifestyle issues, genetic differences also play a role, notes Atlanta cardiologist Jayne Middlebrooks, MD, director of cardiology, Health Screen America, and a member of the Association of Black Cardiologists.

For instance, studies suggest that part of the reason for the disparities in rates of heart disease may be differences in how African Americans process salt and use renin, an enzyme secreted by the kidneys, resulting in high rates of hypertension.

Additionally, studies suggest that African Americans may produce less nitric oxide in their blood vessels and destroy it too quickly. Nitric oxide is critical to insure the proper functioning of blood vessels and blood cells, and plays a role in heart failure, rates of which are twice as high among African Americans. (26)

Such genetic differences help explain the fact that drugs like ACE inhibitors and angiotensin receptor blockers often don't work as well in blacks. They also help explain why a drug that showed little benefit when tested on a primarily white population had such an extraordinary effect when tested only on black participants.

The drug is BiDil, an experimental combination of two already approved drugs, isosorbide dinitrate (Isordil), which provides nitric oxide, and hydralazine (Apresoline), which helps the body better use nitric oxide.

In the study, called the African-American Heart Failure Trial, 525 African Americans with advanced heart failure received BiDil, along with standard treatment for heart failure and another 525 half received a placebo along with standard treatment. The trial was stopped prematurely in July 2004 after analysis showed death rates in those receiving BiDil were 43 percent lower than those receiving placebo. (26)

Publication of the study in the New England Journal of Medicine in November 2004 ignited a storm of controversy, with many experts worrying about the implications of using drugs based on race alone.

Dr. Middlebrooks understands the concern, but doesn't think it's relevant. "I think America in general is trying to get away from dividing everyone by race," she says. "So if you look at a study that only looked at African Americans, there's always going to be a subset of people who are going to raise their eyebrows and be somewhat concerned about that. But I think this is important research that really needed to be done. So many of the medications that come out are used by African Americans because our incidence of hypertension and heart disease is higher than the average white American and our life expectancy is less."

The study itself was co-sponsored by the Association of Black Cardiologists, which posted a notice on its Web site noting that "African Americans suffer disproportionately from heart failure and that new clinical data and new medicines are needed to address the problem. The fact that African Americans are underrepresented in clinical trials is also a compelling reason for us to participate in these investigations." (27)

While Dr. Middlebrooks definitely believes that African Americans are undertreated when it comes to heart disease, she doesn't think it's because of some prejudice on the part of the medical establishment. "We're undertreated because we don't seek medical care as early as we should, and then once we do, we don't manage the chronic condition the way we should," she says.

References

(26) Taylor Al., Ziesche S, Yancy C, et al. African-American Heart Failure Trial Investigators. Combination of isosorbide dinitrate and hydralazine in blacks with heart failure. N Engl J Med. 2004 Nov 11;351(20):2049-57.

(27) Frequently Asked Questions About The A-Heft Trial Background For Abc Members. Association of Black Cardiologists. http://www.abcardio.org/article_trial.html.