Heart Disease Research Promising for Patients with High Blood Pressure

After more than a decade of investigative work to see if newer high blood pressure medication was better at preventing heart disease than an older, popular diuretic, researchers at The University of Texas School of Public Health at Houston have concluded that the diuretic chlorthalidone faired better than its challenger, an alpha-blocker called doxazosin.

The multicenter study called the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial, or ALLHAT, was funded by the National Heart, Lung and Blood Institute in 1993 to compare the benefits of four drugs, including chlorthalidone and doxazosin. A detailed analysis of the study results were published recently in the Annals of Internal Medicine.

The UT-Houston School of Public Health was awarded a $103.2 million contract from the National Heart, Lung and Blood Institute to coordinate ALLHAT, making it the largest contract ever awarded to UT-Houston. The final results of the entire ALLHAT study will be presented later this year.

Two years ago, UT-Houston researchers showed that study participants who took chlorthalidone cut their risk of heart failure in half, compared to those who took doxazosin. The institute halted the doxazosin part of the study early based on the findings.

Barry R. Davis, M.D., Ph.D., professor of biometry at the UT-Houston School of Public Health and director of the school’s Coordinating Center for Clinical Trials, reported that giving high blood pressure patients additional medications diminished but did not increase the risk of heart failure in patients on doxazosin compared with those on chlorthalidone.

“We wanted to know if the higher risk of heart failure seen with doxazosin compared with chlorthalidone could be explained by differences in blood pressure or the use of additional antihypertensive drugs. We found that the diuretic was superior to the alpha blocker in preventing heart failure,” Davis said. “We also found that the difference in the two treatment modes made very little difference.”

The study followed 42,418 patients, age 55 and older, with high blood pressure and at least one of several cardiovascular disease risk factors, such as diabetes or a history of stroke. The patients were randomly assigned to receive one of four high blood pressure drugs, including chlorthalidone and doxazosin. Researchers examined whether differences between the study groups could be caused by differences in blood pressure or the use of additional drugs.

“The patients who were on chlorthalidone had slightly better blood pressure control than those taking doxazosin. Fewer of them needed additional blood pressure drugs,” Davis said. “Heart failure happened more often in the patients who took doxazosin than in those on chlorthalidone, even after differences in blood pressure control an the use of other drugs were considered.”

Davis says, although the study is conclusive, more studies are needed.

“The study can’t tell us if doxazosin caused heart failure, whether chlorthalidone prevented heart failure, or some combination of both effects,” Davis said. “Our study results showed that higher blood pressure with doxazosin versus chlorthalidone did not explain most of the increased risk for heart failure. The risk diminished but did not disappear when other antihypertensive drugs are used.”

More than 4.6 million Americans suffer from heart failure, a leading cause of disability and death in the United States. It is the most common hospital diagnosis among people age 65 and older. More than 50 million Americans have high blood pressure, with African-Americans disproportionately afflicted by the condition.

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