Metoprolol prophylaxis against postoperative atrial fibrillation increases length of hospital stay in patients not on pre-operative β blockers: the β blocker length of stay (BLOS) trial

Postoperative atrial fibrillation (AF) is a common complication of heart surgery, affecting 20–40% of patients. In recent guidelines of the American Heart Association and the European Society of Cardiology, β blocker (BB) treatment has been recommended as a first line choice for the prevention of postoperative AF.1 Although the efficacy of re-administration of BB to post-cardiac surgery patients has been evaluated, the effectiveness of prophylactic BB in patients without prior BB treatment has not been adequately studied. In order to evaluate whether preoperative BB use affects the outcome of prophylactic BB treatment after heart surgery, an analysis was performed using the data of the largest double blind, placebo controlled, randomised trial of prophylactic BB treatment (metoprolol) for reduction in hospital length of stay following heart surgery, known as the β blocker length of stay (BLOS) study.2 In the BLOS study 1000 patients undergoing elective open heart surgery were randomised equally to metoprolol (100–150 mg/day) or double blind placebo, started within 12 hours of arrival in the intensive care unit (ICU) after surgery. The patients were followed for postoperative AF, length of hospital stay, and cost of in-hospital care. …