by Phyllis Hanlon, Contributing Writer
Few studies have examined whether race makes a difference in how often pulmonary hypertension (PH) occurs and what causes it. These questions prompted a specialist team at Vanderbilt University Medical Center, an accredited Pulmonary Hypertension Care Center (PHCC), to explore the issue. Overall, the team found that the African American race was associated with a 41 percent increased risk for PH and 24 percent increased mortality among those who already have PH.
Bin Q. Yang, M.D., in Vanderbilt’s Department of Medicine, led the study, which sought to examine whether being an African American can increase one’s risk for developing PH, and whether African Americans are at increased risk of death.
According to the authors, this study included 4,576 patients; 3,990 (87.2 percent) were Caucasian and 586 (12.8 percent) were African American. Dr. Yang and his colleagues used a de-identified version of the Vanderbilt electronic medical record system that contains information about more than 2.5 million people who have been to Vanderbilt University Medical Center. All patients had been referred to Vanderbilt’s outpatient and inpatient units for right heart catheterization. After the authors reviewed the data, they found the African American group was younger than the Caucasian group by an average of eight years. They also noted that the African American group had higher heart failure rates and more metabolic syndrome features, including hypertension (high blood pressure), diabetes, obesity and higher creatinine (elevated levels of this compound can signal kidney disease or a malfunctioning kidney). The African American group also was more likely to be taking anti-hypertensive medication to lower systemic blood pressure or diuretics, a water pill that also helps to lower blood pressure.
In addition to reviewing the Vanderbilt data, the authors examined findings from the Jackson Heart Study, a very large trial in metropolitan Mississippi that investigated cardiovascular disease and genetic factors that might be associated with high blood pressure, heart disease, stroke, diabetes and other diseases in African Americans. As part of this study, patients underwent echocardiography, which showed that PH is related to an increase in hospitalization for heart failure, the authors reported.
In the Vanderbilt study, Dr. Yang and his colleagues did not investigate how PH develops in African American patients. However, they referred to the Jackson Heart Study’s finding that a substance called endothelin-1 causes the blood vessels to narrow. Endothelin receptor antagonists (ERAs), which block endothelin from causing the blood vessels to constrict, are one type of PH-specific medication. African Americans tend to release three times more endothelin than Caucasians and potentially might not respond as well to ERAs, the authors added.
In spite of some conclusive findings, this study does have limitations, the authors noted. Since the patients in this study were referred, it is unclear how many patients of African American descent or other racial/ethnic minorities live in the community and have PH. The authors also did not have access to data about socioeconomic or health insurance status, which explains some of the differences found in the study. Finally, the information about other diseases participants in the data analysis had, in addition to PH, came from International Classification of Diseases, Ninth Revision (ICD-9) coding, which has been known to be inaccurate in diseases like PH. As a result, if patients with PH also have other medical conditions that are not accurately captured, the findings might be incorrect.
In spite of these shortcomings, the findings are important, according to the authors. They asserted that the conclusions could be generalized since they used a very large sample size that included all patients undergoing right heart catheterization. They concluded that their findings demonstrated a need for further study on the genetic, environmental and molecular (atoms or small particles) factors that may influence the development of PH in African Americans, and the observed differences in outcomes.
The authors suggested that going forward, any studies that look at PH, including pulmonary arterial hypertension (PAH) or PH due to left heart disease, should include African American participants as a subgroup.
The research findings were published earlier this year in Pulmonary Circulation. The National Institutes of Health, the American Heart Association and the Gilead Pulmonary Arterial Hypertension Scholars Award Program provided support for the study.