['Atrial fibrillation (AF) is the most frequent tachyarrhythmia in patients with a permanent pacemaker. Angiotensin II receptor antagonists have a protective effect against the occurrence of AF in patients with heart diseases. This study aimed to assess the effectiveness of olmesartan in the prevention of new-onset AF and AF burden in atrioventricular block (AVB) patients with dual-chamber (DDD) pacemaker implantation.', 'This was a single-center, prospective, randomized, single-blind, controlled clinical study. A total of 116 AVB patients, who received DDD pacemakers implantation with the percentage of ventricular pacing (VP%) ≥40% from April 22, 2011 to December 24, 2012, were prospectively randomized to olmesartan group (20 mg per day; n = 57) or control group (n = 59). Patients were followed up using pacemaker programming, 12-lead electrocardiography in the intrinsic sinus rhythm, laboratory examinations, and transthoracic echocardiography at 24 months. Atrial high rate events (AHREs) were defined as 180 beats/min over a minimum of 5 min. AF burden was calculated by the number of hours with AHREs divided by the number of measurement hours.', 'Ten (17.5%) patients in the olmesartan group and 24 patients (40.7%) in the control group occurred new-onset AF, and the difference between two groups was statistically significant (P = 0.04). AF burden was lower in olmesartan group than that in control group (8.02 ± 3.10% vs. 13.66 ± 6.14%, P = 0.04). There were no significant differences in mean days to the first occurrence of AHREs and mean cumulative numbers of AHREs between two groups (P = 0.89 and P = 0.42, respectively). Moreover, olmesartan group had smaller values of maximal P-wave durations and P-wave dispersion (PD) after 24 months follow-up compared with the control group (109.5 ± 7.4 ms vs. 113.4 ± 7.1 ms, P = 0.00; and 40.6 ± 4.5 ms vs. 43.3 ± 4.4 ms, P = 0.02, respectively). Left ventricular end-diastolic diameter and left ventricular ejection fraction were not significantly different between two groups (both P > 0.05).'] Does olmesartan reduce New-onset Atrial Fibrillation and Atrial Fibrillation Burden after Dual-chamber Pacemaker Implantation in Atrioventricular Block Patients?