The effectiveness of preoperative beta blockers in reducing inhospital mortality rate in patients with LVEF less than 30% is uncertain.609,617 (Level of Evidence: B) See Online Data Supplement 25 for additional data on beta blockers. Because beta blockers have been shown to reduce the inci- dence of postoperative AF in CABG patients who are receiving them preoperatively604,605,608 (Section 5.2.5), the STS and AHA recommend that they be administered preoperatively to all patients without contraindications and then be continued post- operatively.618,619 Despite this recommendation, uncertainty ex- ists about their efficacy in subjects not receiving them preoper- atively; in this patient population, their use appears to lengthen hospital stay and not to reduce the incidence of postoperative AF.604,607 Their efficacy in preventing or treating perioperative myocardial ischemia is supported by the results of observational studies and small RCTs.612 614 Although a meta-analysis of available data did not show an improvement in outcomes with perioperative beta blockers,615 observational analyses suggest that preoperative beta-blocker use is associated with a reduction in perioperative deaths.609 611 Another analysis of data from 629 877 patients reported a mortality rate of 2.8% in those receiving beta blockers versus 3.4% in those not receiving Few data are available on the pharmacokinetic disposition of beta blockers in the early postoperative period, when an alteration in gastrointestinal perfusion may adversely affect their absorption after oral administration. 