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Giving beta-blockers to patients about to undergo coronary artery bypass grafting (CABG) was not associated with improved perioperative outcomes, an observational analysis showed.

The rate of mortality and several other outcomes within 30 days of the operation did not differ significantly between patients who received a beta-blocker in the 24 hours before surgery and those who did not, according to , of the Cardiopulmonary Research Science and Technology Institute in Plano, Texas, and colleagues.

And new-onset atrial fibrillation was slightly but significantly greater in the patients who received a beta-blocker (21.50% versus 20.10%; OR 1.09, 95% CI 1.06-1.12), the researchers reported online in .

"On the surface, these observational study data stand in contrast to the endorsed National Quality Forum standards that mandate preoperative beta-blocker use before CABG procedures," they wrote, noting that the findings are consistent with studies of patients undergoing noncardiac surgery, as well.

"A prospective randomized trial with careful attention to adequate dosing and specific drug type may help to answer this question [in cardiac surgery]," they wrote.

Commenting on the study, Alan Markowitz, MD, chief surgical officer at UH Case Medical Center, said, the study "puts a serious dent in a practice that we normally pursue for virtually everyone undergoing coronary bypass surgery. It will make us step back and really reconsider whether we need to give everyone a beta-blocker. It's in a philosophy of one-size-fits-all and perhaps we should more specifically decipher who would benefit the most rather than [use] just a blanket administration of this drug."

He added that he doesn’t think the recommendations for preoperative beta-blockade in patients undergoing CABG should be rescinded, "but they should be modified with a much broader study that eliminates some of the limitations of this study."

The use of beta-blockers before CABG has been associated with reduced perioperative mortality in prior observational studies conducted in the 1990s, and the practice was adopted as a national quality standard in 2007. However, no randomized trials have examined the utility of preoperative beta-blockade and more recent observational studies have raised questions about its use.

The current analysis, which used data from the database (STS-NCD), included 506,110 adult patients who underwent nonemergent CABG at 1,107 U.S. hospitals from 2008 through 2012. The researchers excluded patients who had a myocardial infarction in the 21 days before the operation -- because these patients are known to derive benefits from beta-blockers -- and those with high-risk presenting symptoms.

Overall, 86.24% of the patients received a beta-blocker in the 24 hours before surgery, with the rate increasing from 80.15% in 2008 to 92.72% in 2012.

In a propensity score-matched analysis, there were no significant differences between patients who did and those who did not receive a beta-blocker for several perioperative outcomes:

• Mortality: 1.12% versus 1.17% (OR 0.96, 95% CI 0.87-1.06)
• Permanent stroke: 0.97% versus 0.98% (OR 0.99, 95% CI 0.89-1.10)
• Prolonged ventilation for more than 24 hours: 7.01% versus 6.86% (OR 1.02, 95% CI 0.98-1.07)
• Any reoperation: 3.60% versus 3.69% (OR 0.97, 95% CI 0.92-1.03)
• Renal failure: 2.33% versus 2.24% (OR 1.04, 95% CI 0.97-1.11)
• Deep sternal wound infection: 0.29% versus 0.34% (OR 0.86, 95% CI 0.71-1.04)

The researchers said the higher rate of atrial fibrillation seen in the beta-blocker group "seems counterintuitive and is in contrast to guidelines for the treatment of atrial fibrillation."

"Because the STS-NCD only collects data on preoperative beta-blocker use (within 24 hours of the incision) as a yes/no field, we are unable to determine whether the timing, the dose given, or other unrecorded covariates may contribute to this observation," they wrote.

They acknowledged some additional limitations of the study, including the lack of information on beta-blocker type and physiologic response, the 30-day follow-up period, and the inability to determine why beta-blockers were not used in some of the patients.

In an accompanying editorial, , of Massachusetts General Hospital in Boston, raised other issues as well.

Short-term mortality rates after CABG have been driven so low in contemporary patients, he said, that mortality may not be the most appropriate endpoint to assess the utility of preoperative beta-blockade.

"The effect of beta-blockade on longer-term survival or a composite of nonfatal outcomes may provide additional insights," he said.

Also, the database used did not include information on whether patients were on long-term beta-blocker therapy, on the exact timing of and protocol for administration of the drugs, and on the use of the antiarrhythmic amiodarone, which could have confounded the results.

A further issue was that the propensity-matching process resulted in a cohort of patients taking beta-blockers that had lower rates of comorbidities and a lower surgical risk compared with the larger group.

"They are not representative of the broader population of beta-blocker patients, and this difference may affect the generalizability of the study's findings," Shahian said.

"The study by Brinkman and colleagues is an important and hypothesis-generating observational analysis," he concluded. "However, owing to the limitations discussed above, continued adherence to current ACC/AHA guidelines regarding preoperative beta-blockade in CABG surgery, together with good medical judgment, is advisable."

"Additional randomized and observational studies, including new variables in STS-ND version 2.8, might shed further light on this issue," he said.

From the American Heart Association:

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