ObjectivesPostoperative atrial fibrillation (POAF) is the most common complication after cardiac surgery and affects around 30% of patients. Variable guidelines from multiple organisations exist for the prevention of POAF after cardiac surgery. We conducted a survey of UK practice was conducted to define “usual care” for a platform trial of interventions to prevent POAF after cardiac surgery. To provide context for the survey, we reviewed all current guidelines for the prevention and management of AF after cardiac surgery. DesignOnline survey and literature review SettingSurvey: All 35 UK National Health Service Cardiac Surgery Centres. Literature Review: Guidelines from specialist societies and other guideline making organisations from the UK, Europe and North America. ParticipantsEstablished link network of researchers. Measurements and Main ResultsReview: Five relevant guidelines were identified. All guidelines recommend β-blockade for prevention of AF after cardiac surgery. Treatment of AF is recommended using either rate or rhythm control. Cardioversion is recommended only for the haemodynamically unstable patient. Patients who remain in AF for over 48 hours should be considered for anticoagulation. Patients should be followed up within 60 days to review the need for anti-arrhythmic and anticoagulant therapy. Survey: 31/35 (89%) of centres responded. 11 of 31 (35.5%) centres followed local guidance for prevention of POAF, 4 (13%) centres followed Society of Cardiovascular Anesthesiologists / European Association of Cardiothoracic Anaesthesia guidelines, 4 (13%) followed UK National Institute of Health and Care Excellence guidance and 4 followed “other” guidance. 8 of 31 (26%) followed no guidelines to prevent POAF. 28 of 31 (90%) centres did not risk-stratify their patients for POAF. Most centres (23/31, 74%) do not have a care-package in place to prevent POAF, but 14 of 31 (45%) try in some way to prevent AF in patients presenting in sinus rhythm. The most common interventions to prevent POAF are β-blocker use post-operatively (23/31, 74%), use of magnesium (20/31, 64.5%) and maintaining a serum K+ ≥4.5mmol/L (26/31, 84%). ConclusionsGuidance to prevent AF after cardiac surgery clusters around the use of β-blockade. Although patients in the UK do not appear to be risk-assessed for POAF, the main interventions used to prevent it are similar; β-blockade and maintenance of serum K+ and Mg2+ levels.