Beta-blockers work by blocking the hormone adrenaline from reaching the beta-adrenergic receptors of cells in the sympathetic nervous system, which controls basic heart functions. This allows the drugs to slow the heartbeat and lower blood pressure. Long- term treatment with beta-blockers has long been standard therapy for many heart patients.
There are two types of beta-adrenergic receptors, beta-1 and beta-2.
Now, a study of 735 patients treated for heart attack or unstable angina found that variant versions of the gene for beta-2 affected survival of those given the drugs. No such effect was found for the beta-1 gene.
"We identified high-, intermediate- and low-risk groups that had particular variations in these genes, which interact with beta-blocker drugs," said co-researcher Howard L. McLeod, a professor of medicine, genetics, molecular biology and pharmacology at Washington University School of Medicine, in St. Louis.
The researchers published their findings in the Sept. 28 issue of the Journal of the American Medical Association.
People with two specific variants of the beta-2 gene are at greatest risk, the study found -- those with variants designated 79 CC and 46 AA. An estimated 39 percent of Americans carry the 79CC version, and 16 percent carry the 46 AA version.
Patients carrying those variants who were given beta-blockers were at an up to five times higher risk of death during the three years of the study, compared with those with other versions of the gene, the researchers reported. No genetic effect on survival was found for patients who did not get beta-blockers.
"These data, while provocative, should not immediately alter current practice," said Dr. David E. Lanfear, lead author of the report, who was at Washington University when the study was done and is now a cardiologist at Henry Ford Hospital in Detroit. He said studies have shown that beta-blockers reduce the amount of heart muscle that dies in a heart attack and prolong survival for most patients.
McLeod agreed, noting that his university's hospitals are still prescribing beta-blockers for patients sent home after treatment for acute coronary syndrome, an umbrella term that covers heart attack and unstable angina.
"Until we can verify that our data are correct and -- more important -- what these patients really need, we are prescribing beta-blockers," he said.
The same investigators are already beginning a larger study along the same lines, funded in part by the National Institutes of Health. They plan to enroll 4,500 people treated for heart attacks at 20 medical centers around the country. Researchers will evaluate their heart function, quality of life and survival on the basis of variation in the beta-adrenergic genes and other genes that are potentially important in heart disease.
Another study scheduled to begin at Washington University will look for the appropriate treatments for patients whose genetic makeup might make beta-blocker use hazardous, McLeod said.
More information
For more on drugs used to lower blood pressure, visit the American Heart Association.
And people who eat adequate amounts of fruit and vegetables -- five to nine servings daily -- may cut their cancer risk in half compared to those who don't.
To increase your consumption, the Virginia Department of Health suggests you:
- Eat fruit or drink 100 percent fruit juice for breakfast.
- Have a fruit or vegetable snack every day.
- Buy fresh, frozen, canned and dried fruits and vegetables.
- Steam or microwave vegetables for dinner.
