People given a blood pressure drug known as a beta blocker to reduce heart risks before surgery were one-third more likely to die within a month and had double the risk of stroke compared with those given a dummy pill, Canadian researchers said on Monday.
The study is the largest, most rigorous to date looking at whether beta blockers do more harm than good in reducing surgery-related risks. Other, smaller studies have had mixed results.
“There is a real potential that beta blockers are causing serious harm in the surgical setting,” said Dr. P.J. Devereaux of McMaster University in Ontario, whose study appears in the journal The Lancet.
“If my mother was undergoing surgery and given a beta blocker, I would be extremely upset based on this evidence.”
The findings challenge the long-held belief that giving people a beta blocker before major surgery protects them from heart risks brought on by the stress of the procedure.
Surgery often raises levels of a stress hormone known as catecholamine, which drives up a person’s blood pressure and heart rate. “Beta blockers block the effects of increased catecholamines, so the physiological rationale would say they would be beneficial to people,” Devereaux said in a telephone interview.
He and colleagues set out to test this idea. They studied more than 8,000 patients in 23 countries at 190 hospitals who were undergoing major surgery unrelated to the heart. People in the study had or were at risk for clogged arteries.
Half were given the beta blocker metoprolol, sold by AstraZeneca as Toprol XL, two to four hours before and 30 days after their surgery. The other half got a placebo.
The doctors were looking for heart complications such as heart-related death, non-fatal heart attacks or a heart-stopping event known as cardiac arrest in which the person survived.
While the study did find people given the drug had fewer heart attacks and abnormal heart rhythms, they also were more likely to die or have a stroke.
The researchers said for every 1,000 people with similar risks undergoing non-cardiac surgery, the drug could prevent 15 people from having a heart attack, three from needing a shock to restore a normal heart beat, and seven from developing a type of heart rhythm known as atrial fibrillation.
But eight more people would die, five would have a stroke, 53 percent would have abnormally low blood pressure and 42 percent would have an abnormally slow heart beat.
“This is an important study because, although the beta blocker reduced the number of heart attacks that occurred following surgery, it caused more strokes, thus on balance causing more harm than good,” Peter Weissberg, medical director of the British Heart Foundation, said in a statement.
“This is why it is so important to undertake large clinical trials rather than assuming drugs will only do what is expected of them.”
Devereaux, who first presented his findings at the American Heart Association meeting in November, said he expects the study to stir debate about whether it is still wise to give patients a beta blocker before a major surgery.
“It is telling us something we didn’t realize in the past,” he said.