Study questions use of pre-CABG beta blockade

By Anne Harding

NEW YORK (Reuters Health) - A national database analysis shows little benefit from giving beta blockers before coronary artery bypass grafting (CABG) surgery.

"This calls into question the use of the preoperative beta blocker as a quality indicator, which is something a lot of doctors are under pressure to do," Dr. William Brinkman of the Cardiopulmonary Research Science and Technology Institute in Dallas, the first author of the study, told Reuters Health in a telephone interview.

The findings were published online June 16 in JAMA Internal Medicine.

Based on retrospective analyses reported in the late 1990s that found benefits of preoperative beta blockade in CABG, beta blockers before CABG have been used as a quality standard since 2007, potentially affecting both surgeon and hospital reimbursement, Dr. Brinkman and his team note in their paper.

However, they add, there have not been prospective randomized studies looking at the benefit of the drugs before surgery.

To investigate whether empirical beta blockade before CABG reduces mortality, the researchers looked at data from the Society of Thoracic Surgeons National Adult Cardiac database on more than half a million patients treated at 1,107 hospitals between 2008 and 2012. Most - 86% - had received beta blockers within 24 hours before surgery. All had undergone non-emergent surgery. The investigators excluded patients who had myocardial infarction within 21 days of surgery or other high-risk presenting symptoms.

A propensity-matched analysis of 138,542 patients (69,271 in each group) found no significant difference between patients who did and did not receive beta blockers in rates of operative mortality, permanent stroke, prolonged ventilation, reoperation, renal failure, or deep sternal wound infection. But patients who received beta blockers had a significantly higher risk of new-onset atrial fibrillation (21.5% vs 20.1%, p<0.001).

"Beta blockers are very useful drugs. We're not saying that they're bad, but you need to use them in specific clinical scenarios," Dr. Brinkman said. Measuring quality based on use of beta blockers in all CABG patients is "not good medicine," he added. "The guidelines are simplistic, and just because you can measure something easily doesn't mean that it's quality."

Dr. David Shahian of Massachusetts General Hospital in Boston wrote an editorial accompanying the study. "Any time you have one study that contradicts the findings of many previous studies, you have to put it in context, and I certainly would not recommend that anybody change current practice based on the results of this one study," he told Reuters Health in a telephone interview.

"It's hypothesis-generating and certainly merits further investigation, but the protective effects of beta blockade have been extremely well documented in dozens of studies, particularly with respect to reduction of atrial fibrillation, and the fact that in this study the incidence of atrial fibrillation was actually increased in patients who received beta blockers is in and of itself enough to question the validity of the study," Dr. Shahian added.

The current analysis could not include information on how beta blockers were administered, which ones were used, and how long patients took them before surgery, because this information was not available, according to Dr. Shahian. This information will be added to the Society of Thoracic Surgeons Adult Cardiac Surgery database in the future to make more detailed analyses possible, he added. "With those additional pieces of information it may be possible to shed some further light on this question," Dr. Shahian said.

"The evidence clearly indicate that the longer you can start administering the beta blocker before surgery the more effective and safer they will be," he added. "If practitioners are simply giving an intravenous dose immediately before surgery and not titrating to the optimal heart rate and blood pressure, that may not achieve the desired effect."

Dr. Shahian noted that Dr. Brinkman and his team excluded higher-risk patients from their analysis, who actually may benefit the most from pre-CABG beta blockade.

"I would strongly urge that providers continue to adhere to the ACA/AHA guidelines and as with any guidelines, you exercise good clinical judgment when applying that guideline to an individual patient," he said.

SOURCE: http://bit.ly/1nkmjKB

JAMA Intern Med 2014.

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