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While patients with three or four heart risk factors should still be given beta-blockers before an operation, people with no risk for heart disease shouldn't get the medications because it might lower the odds of a good outcome, the researchers reported.
Previously these drugs were thought to protect the heart during an operation, but their ability to lower blood pressure caused some patients without heart risk factors to develop dangerously low blood pressure and die from strokes, said lead researcher Dr. Mark Friedell, chairman of the department of surgery at the University of Missouri-Kansas City School of Medicine.
"Patients who have significant cardiac risk factors benefit from beta-blockers started before surgery, but patients who don't have any cardiac risk factors do worse when beta-blockers are started before surgery," he said.
Beta-blockers are used to lower blood pressure and slow the heart.
Friedell said that patients with one or two heart risk factors showed no benefit from beta-blockers. However, those with three or four risk factors benefited significantly from the drug.
Conversely, patients with no heart risk factors who were given a beta-blocker were 1.2 times more likely to die during the study period than those not given the drug.
"Beta-blockers should not be started before surgery on those with no cardiac risk factors," he said.
However, Friedell cautioned that patients already taking a beta-blocker should continue to take it before, during and after surgery.
The report was published online May 27 in the journal JAMA Surgery.
For the study, Friedell's team collected data on more than 325,000 patients. Just over 96 percent of the study patients had non-cardiac surgery and nearly 4 percent had heart surgery. Among all of the patients, 43 percent were given a beta-blocker.
Of the patients who did not get a beta-blocker, 0.5 percent of those who had no heart risk factors died within 30 days after surgery, as did 1.4 percent of those with one or two risk factors and 6.7 percent of those with three to four risk factors, the researchers found.
For those who did get a beta-blocker, 1 percent of those with no heart risk factors died, as did 1.7 percent of those with one or two risk factors and 3.5 percent of those with three to four risk factors, the findings showed.
Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, said, "The use of beta-blocker therapy to reduce the risk of cardiovascular events in patients undergoing non-cardiac surgery has been controversial, with guideline recommendations having undergone substantial revision in recent years."
Initial small studies suggested significant benefits with beta-blockers, but some of these trials were later found to be unreliable, added Fonarow, who was not involved with the new study.
"A more recent, large clinical trial showed lower risk of heart attack and stroke and death with beta-blocker therapy [in patients with heart risk factors], but higher risk of low blood pressure, stroke, and death [in patients without heart risk factors]," Fonarow said. "Earlier studies have suggested a benefit in patients with cardiac risk factors but potential harm in low-risk patients."
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