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Importance The NAVIGATE ESUS randomized clinical trial found that 15 mg of rivaroxaban per day does not reduce stroke compared with aspirin in patients with embolic stroke of undetermined source (ESUS); however, it substantially reduces stroke risk in patients with atrial fibrillation (AF). Objective To analyze whether rivaroxaban is associated with a reduction of recurrent stroke among patients with ESUS who have an increased risk of AF. Design, Setting, and Participants Participants were stratified by predictors of AF, including left atrial diameter, frequency of premature atrial contractions, and HAVOC score, a validated scheme using clinical features. Treatment interactions with these predictors were assessed. Participants were enrolled between December 2014 and September 2017, and analysis began March 2018. Intervention Rivaroxaban treatment vs aspirin. Main Outcomes and Measures Risk of ischemic stroke. Results Among 7112 patients with a mean (SD) age of 67 (9.8) years, the mean (SD) HAVOC score was 2.6 (1.8), the mean (SD) left atrial diameter was 3.8 (1.4) cm (n = 4022), and the median (interquartile range) daily frequency of premature atrial contractions was 48 (13-222). Detection of AF during follow-up increased for each tertile of HAVOC score: 2.3% (score, 0-2), 3.0% (score, 3), and 5.8% (score, >3); however, neither tertiles of the HAVOC score nor premature atrial contractions frequency impacted the association of rivaroxaban with recurrent ischemic stroke (P for interaction = .67 and .96, respectively). Atrial fibrillation annual incidence increased for each tertile of left atrial diameter (2.0%, 3.6%, and 5.2%) and for each tertile of premature atrial contractions frequency (1.3%, 2.9%, and 7.0%). Among the predefined subgroup of patients with a left atrial diameter of more than 4.6 cm (9% of overall population), the risk of ischemic stroke was lower among the rivaroxaban group (1.7% per year) compared with the aspirin group (6.5% per year) (hazard ratio, 0.26; 95% CI, 0.07-0.94;Pfor interaction = .02). Conclusions and Relevance The HAVOC score, left atrial diameter, and premature atrial contraction frequency predicted subsequent clinical AF. Rivaroxaban was associated with a reduced risk of recurrent stroke among patients with ESUS and moderate or severe left atrial enlargement; however, this needs to be independently confirmed before influencing clinical practice.

IMPORTANCE: New-onset postoperative atrial fibrillation (POAF) is a common complication of coronary artery bypass graft (CABG) surgery. However, the long-term risk of thromboembolism in patients who develop POAF after CABG surgery remains unknown. In addition, information on stroke prophylaxis in this setting is lacking. OBJECTIVE: To examine stroke prophylaxis and the long-term risk of thromboembolism in patients with new-onset POAF after first-time isolated CABG surgery compared with patients with nonsurgical, nonvalvular atrial fibrillation (NVAF). DESIGN, SETTING, AND PARTICIPANTS: This cohort study used data from a clinical cardiac surgery database and Danish nationwide registries to identify patients undergoing first-time isolated CABG surgery who developed new-onset POAF from January 1, 2000, through June 30, 2015. These patients were matched by age, sex, CHA(2)DS(2)-VASc score, and year of diagnosis to patients with nonsurgical NVAF in a 1 to 4 ratio. Data analysis was completed from February 2017 to January 2018. MAIN OUTCOMES AND MEASURES: The proportion of patients initiating oral anticoagulation therapy within 30 days and the rates of thromboembolism. RESULTS: A total of 2108 patients who developed POAF after CABG surgery were matched with 8432 patients with NVAF. In the full population of 10 540 patients, the median (interquartile range) age was 69.2 (63.7-74.7) years; 8675 patients (82.3%) were men. Oral anticoagulation therapy was initiated within 30 days postdischarge in 175 patients with POAF (8.4%) and 3549 patients with NVAF (42.9%). The risk of thromboembolism was lower in the POAF group than in the NVAF group (18.3 vs 29.7 events per 1000 person-years; adjusted hazard ratio [HR], 0.67; 95% CI, 0.55-0.81; P

This study aims to quantify the incidence of atrial fibrillation in patients at high risk for but without previously known atrial fibrillation using an insertable cardiac monitor.