Why does isosorbide dinitrate and hydralazine work in treating congestive heart failure in african americans?

Results from the African-American Heart Failure Trial suggested a strong improvement. I just want to know whether there are any biological justifications found.

Seems all very muddy at this stage but there are some findings....

Firstly in 2001, the prevalence of HF was 40% more common in black males than white males (3.5% vs 2.3%) and twice as common in black females as white females (3.1% vs 1.5%).

In this debate, one issue that is commonly confused is the difference between race and ancestry. Ancestry refers to objective genetic relationships between individuals and among populations, whereas race has always been a somewhat arbitrary definition of population boundaries. For example, while an individual might have ancestors from Europe, Africa, and North America, he or she still might be categorized as an African American. Therefore, race captures some biological information about ancestry, but it is not equivalent to ancestry.

Yet clinicians often want to know whether it is valid and reliable to use race as a proxy to infer an individual's genetic risk for disease and treatment response. Whether race matters is, however, complicated because it depends on the relationship between the genetic risk factor, ancestry, and race. For example, beta-blockers and angiotensin-converting enzyme (ACE) inhibitors for hypertension treatment may not work as well, on average, in African Americans compared with European Americans, but both types of drugs appear to work perfectly well in a large fraction of African Americans and poorly in some European Americans.

The observation might be explained by a hypothetical genetic predictor of positive response to ACE inhibitors that is common in European Americans but that is also present in some African Americans because of admixture and absent in some European Americans. In such a case, the best predictor of treatment response might be the presence of the variant (ie, direct testing); the next best might be an accurate estimator of genetic ancestry, and race might be only a poor predictor of genetic risk and therefore treatment response.