The researchers also found that while mortality rates within the first 30 days after treatment were similar between the two ethnic groups, African-Americans were more likely to suffer a major bleeding event or a stroke.
Importantly, differences between Caucasians and African-Americans in terms of patient characteristics and cardiovascular risk factors accounted for only a portion of the disparity in long-term mortality outcomes, according to Duke cardiologist Rajendra Mehta, M.D.
"No matter what patient or treatment feature we adjusted for statistically, this disparity in long-term outcomes still remained," said Mehta, who presented the results of the Duke analysis Nov.9, 2004, at the American Heart Association's annual scientific sessions in New Orleans.
"There has to be something else going on that we don't fully understand," Mehta said. "In order to improve the outcomes for African-American heart attack patients, we feel that there should be prospective clinical study to help us understand what these factors may be and how best to address them."
While the current analysis was not designed to uncover the reasons for these differences, behind, Mehta said he suspects a combination of socio-economic factors, including compliance with long-term drug therapy, mistrust of the medical system, and lack of medical insurance.
According to Mehta, health professionals have assumed African-Americans with coronary artery disease suffer worse outcomes because of their higher prevalence of risk factors, such as hypertension and diabetes, delays in seeking care, lower quality of care and access issues.
However, most studies addressing these questions have involved small numbers of patients or included patients with a wide range of heart disease.
The Duke team chose to focus on a specific group of patients who suffered a kind of heart attack known as an acute ST-elevation myocardial infarction (STEMI). This categorization, based on an electrocardiogram test, is the most severe form of heart attack with the worst short-term outcomes as well as long-term outcomes.
STEMI patients are typically treated quickly in the hospital with clot-busting drugs to restore blood flow to the heart. Many then receive a subsequent angioplasty procedure or coronary artery bypass surgery.
For its analysis, the team pooled data from five different multi-center clinical trials of fibrinolytic, or clot-busting, agents. Of the 32,419 patients in the analysis, 5.1 percent were African-American.
"We found that, when compared to the Caucasian patients, the African-Americans tended to be younger, more likely female, had higher prevalence of cardiovascular risk factors, and were more likely to have higher blood pressure and heart rates," Mehta said. "However, African-Americans also tended to have arteries that responded better to treatment, more likely to have less severe coronary artery disease, and were less likely to have multi-vessel disease."
The researchers found that 6.7 percent of African-Americans had died within thirty days after treatment, compared to 6.6 percent of Caucasian patients. Furthermore, 5 percent of additional African-American patients had died within one year after treatment, compared to 2.9 percent of additional Caucasians.
"What we found particularly intriguing was that African-Americans had worse outcomes despite their average younger age," Mehta continued. The African-Americans were on average 57 years old, compared to 61.1 for Caucasians. "It is well-known that older age is one of the strongest predictors of adverse outcomes for heart attack patients."
The 5.1 percent participation rate of African-Americans in the trials from which the data was drawn is consistent with the historical range of 2 percent to 9 percent African-American participation of in other cardiology trials, Mehta said. African-Americans make up approximately 13 percent of the U.S. population.
"It has been shown that African-Americans are hesitant to participate in clinical trials and that there is a lack of trust in the medical profession, when compared to Caucasians," Mehta said. "This trend is seen more so in certain regions of the country."
Because of the historical under-representation of African-Americans in clinical trials, Mehta said that there is a paucity of data that might help explain the disparity in outcomes. He added that clinical trials involving large numbers of African-Americans will be required to gain reliable data on the epidemiology and biology of heart disease.
"Our data, combined with that gathered from previous studies, show a significant difference in the clinical features and patterns of care between African-Americans and Caucasians," Mehta said. "These differences, coupled with poorly understood genetic, biologic and other socio-economic factors appear to result in higher mortality rates for African-Americans.
"This data also shows that just treating the heart attack acutely may not be enough," he continued. "We also need to focus on improving such issues as compliance, access to care, and trust in the health care system."
The five clinical trials from which data was drawn were GUSTO-I, GUSTO-IIb, GUSTO-III, ASSENT-2 and ASSENT-3. Mehta's analysis was supported by the DCRI.
Other members of the Duke team were SeeHyang Sohn, Karen Pieper and Christopher Granger, M.D. David Marks, M.D., Medical College of Wisconsin, Milwaukee, was also a member of the team.