NEW YORK (Reuters Health) – Many patients with acute MI have risk factors for shock, which increase the likelihood of adverse outcomes with early initiation of beta-blocker therapy, according to a report in the American Heart Journal online April 13.

The findings “are consistent with current recommendations for avoiding early beta-blocker treatment for patients with acute MI,” the authors state.

Beta-blockers reduce mortality in patients following acute MI, note Dr. Michael C. Kontos, at Virginia Commonwealth University in Richmond, and colleagues, but data on early acute use of beta-blockers post-MI are conflicting.

To investigate this issue, they examined data on 10,891 patients with ST-elevation MI (STEMI) and 21,822 with non-ST-segment MI (NSTEMI) who received beta-blockers within 24 hours of presentation.

“We analyzed the use and impact of beta-blockers stratified by variables associated with increased risk for shock specified in the recent guidelines: age >70 years, symptoms >12 hours (STEMI patients), systolic blood pressure 110 beat/min on presentation,” the team explains.

At least one risk factor for shock was present in 63% of the NSTEMI patients and 45% of the STEMI patients, the researchers found. With increasing numbers of risk factors, the likelihood of in-hospital cardiogenic shock or death increased, for both STEMI and NSTEMI patients, according to the report.

In addition, rates of cardiogenic shock and death were increased in patients with a history of CHF or an ejection fraction <40%.

To look at the effect of timing, the patients were further classified as having received beta-blockers in the emergency department or after leaving the ED, and as having started beta-blocker therapy before or after primary PCI in the case of STEMI patients.

On multivariate analysis, NSTEMI patients who were given beta-blockers in the ED had a greater risk for the composite of cardiogenic shock or death (odds ratio 1.23; p=0.0016), while treatment with beta-blockers before primary PCI in STEMI patients was associated with similarly increased risk (OR 1.30; p=0.025), Dr. Kontos and colleagues report.

They conclude, “Our data support current guidelines that indicate that caution should be used when giving beta-blockers to high-risk patients early during the initial acute care period.”

Reference:
Treatment and outcomes in patients with myocardial infarction treated with acute ?-blocker therapy: Results from the American College of Cardiology’s NCDR®
Am Heart J 2011.