Even though it's standard medical practice, prescribing beta blockers the day before heart patients are scheduled for bypass surgery may not improve results, a new study suggests.
In fact, their use 24 hours before bypass surgery may result in slightly higher rates of a heart rhythm abnormality called atrial fibrillation, the study authors said. Beta blockers are commonly prescribed to lower blood pressure by slowing the heart.
"Beta blockers are useful in specific clinical scenarios, but their use is not associated with improved outcomes in bypass surgery," said study lead researcher Dr. William Brinkman, who's with the Cardiopulmonary Research Science and Technology Institute in Dallas.
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The findings were published in the June 16 online issue of JAMA Internal Medicine.
But one heart specialist said the findings don't prove that beta blockers can produce adverse results, and their use before bypass surgery should continue until future studies suggest otherwise.
For the study, Brinkman's team used the Society of Thoracic Surgeons National Adult Cardiac database to review over 506,000 patient records from 2008 through 2012. These patients were having non-emergency heart bypass surgery, and none had had a heart attack in the previous 21 days or any other high-risk symptoms.
The researchers found that 86 percent of the patients were given beta blockers the day before the operation. There was no difference in the rate of deaths from the surgery, or in the rates of stroke or kidney failure or infections at the site of the surgery between those who were given beta blockers and those who weren't.
However, use of beta blockers was associated with a slightly increased risk of atrial fibrillation, a potentially fatal irregular heartbeat. Among patients who received beta blockers, 21.5 percent developed atrial fibrillation, compared with 20.1 percent of patients who did not get them, the study found.
Since beta blockers didn't improve outcomes in this study, Brinkman said he doesn't think they should be given just before bypass surgery as a matter of course. Doctors and hospitals, however, are given quality ratings based on whether they give beta blockers before such surgery.
"This study questions this 'quality indicator,'" Brinkman said. "We are not saying that beta blockers are harmful, but they should be used for specific clinical reasons. Just because something is easy to measure doesn't mean that it is a quality indicator."
Dr. David Shahian is vice president of the Center for Quality and Safety at Massachusetts General Hospital in Boston and author of an accompanying editorial in the journal. He said the study findings are "interesting and certainly warrant further investigation. However, they are at odds with most other studies of this subject."
Other studies have found that beta blockers before a bypass operation reduce the risk of atrial fibrillation before, during and after surgery. And atrial fibrillation can lead to problems such as stroke, which may affect long-term survival, Shahian said.
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"This study was not able to take into account the specific beta blocker, the dose, and how long before surgery it was started. These are important factors that may affect the results of this study," he said.
Until this issue is settled, Shahian said he advises doctors to continue to follow accepted guidelines and give patients beta blockers before bypass surgery, "combined with good medical judgment regarding individual patients."