peutic purposes has increased worldwide. Recently, several studies reported that moderate to high doses (0.5-20 Gy) of radiation exposure were associated with an increased risk of cardiovascular diseases, such as ischemic heart disease, congestive heart disease, rheumatic valvular disease, and hypertensive heart disease. [13][14][15] With regard to radiation-associated conducting system abnormalities and arrhythmias, there are case reports of advanced sick sinus syndrome, atrioventricular block, and bundle branch block long after radiotherapy with high doses >30 Gy. 16 Of 48 Hodgkin disease survivors who received mediastinal irradiation (27-52 Gy), 74.5% had conduction abnormalities or arrhythmia on resting electrocardiograms (ECGs) 6-27 years after irradiation. 17 A recent report found that among cancer patients, the prevalence of AF was higher A trial fibrillation (AF) is the most common arrhythmia in clinical practice. The prevalence and incidence of AF increase with age. 1-3 AF is associated with an increased risk of ischemic stroke, congestive heart failure, reduced quality of life, and mortality. 4-6 AF is a multifactorial disease affected by both environmental and genetic factors. 7 Past studies have established various risk factors for AF, such as aging, male sex, hypertension, obesity, diabetes, hyperthyroidism, alcohol consumption, smoking tobacco, hyperuricemia, and organic heart diseases. 7-9 As possible underlying pathways, there is emerging evidence linking inflammation and oxidative stress to the pathogenesis of AF through atrial fibrosis and electrical and structural remodeling. [10][11][12] The use of ionizing radiation for diagnostic and thera-