Analysis Questions Use of Beta-Blockers Before CABG

June 19, 2014

DALLAS, TX — Patients undergoing coronary artery bypass graft (CABG) surgery treated with a beta-blocker had no significant improvement in 30-day postoperative outcomes compared with those who didn't receive the drugs, according to a new retrospective analysis[1].

Although the American College of Cardiology/American Heart Association (ACC/AHA) guidelines state that the preoperative use of beta-blockers is a class I recommendation to reduce the risk of postoperative atrial fibrillation and is also a National Quality Forum indicator of quality care, researchers found no evidence of benefit on multiple end points, including the risk of operative mortality, permanent stroke, prolonged ventilation, and any reoperation, among others.

In fact, patients who received beta-blockers within 24 hours of surgery had higher rates of new-onset atrial fibrillation when compared with patients who did not. Among those who received beta-blockers, there was a 9% significantly higher relative risk and a 1.4% higher absolute risk of postoperative atrial fibrillation.

"Beta-blockers are an important and effective tool in the care of patients undergoing cardiac surgery in specific clinical scenarios," write Dr William Brinkman (Cardiopulmonary Research Science and Technology Institute, Dallas, TX) and colleagues in their report, published online June 16, 2014 in JAMA: Internal Medicine. However, their recommendation for use in all patients before CABG, especially without adequately ascertaining clinical drug levels, might not improve outcomes. "A prospective randomized trial with careful attention to adequate dosing and specific drug type may help to answer this question."

Data From the STS

The study included 506 110 patients from the Society of Thoracic Surgeons national adult cardiac database, of whom more than 86% received beta-blockers at least 24 hours before CABG. Given the differences in patient characteristics between those who received beta-blockers and those who did not, the researchers conducted a propensity-matched analysis that included 138 542 patients (69 271 patients in each arm).

In the covariate-adjusted analysis that included the entire cohort and the propensity-matched analysis, investigators did not observe any benefit to beta-blocker use in the preoperative setting. The risk of atrial fibrillation, however, was significantly higher among those who received a beta blocker.

30-Day Outcomes in Beta-Blocker–Treated Patients vs Those Not Treated

Outcome Odds ratio (95% CI)
Operative mortality 0.96 (0.87–1.06)
Permanent stroke 0.99 (0.89–1.10)
Prolonged ventilation 1.02 (0.98–1.07)
Reoperation 0.97 (0.92–1.03)
Renal failure 1.04 (0.97–1.11)
Deep sternal infection 0.86 (0.71–1.04)
Atrial fibrillation 1.09 (1.06–1.12)

In an editorial, Dr David Shahian (Massachusetts General Hospital, Boston) believes the present study raises more questions than it answers and should be considered hypothesis-generating until further studies can be performed[2]. The retrospective analysis, he points out, has a number of limitations, including the low mortality rate among patients undergoing CABG. At just 1%, short-term mortality rates might not be sensitive enough to detect the benefit of beta-blocker use.

Patients who had an MI occur 21 days before a CABG procedure were excluded from the analysis, notes Shahian. As a result, patients with STEMI and non-STEMI undergoing isolated CABG were eliminated from the analysis. In addition, there was no assessment of the efficacy of beta-blockade in the STS database

And finally, but importantly, there is a wide selection of data supporting the use of preoperative beta-blockers. "In contrast to the present report, almost 30 randomized studies demonstrate the value of perioperative beta-blockade in reducing the incidence of AF after cardiac surgery," he writes. For the time being, Shahian says that continued adherence to the clinical guidelines, along with sound medical judgment, is recommended.

The authors and editorialist report no conflicts of interest.

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