Data collection and AHRE detection
All patients underwent baseline clinical history-taking, 12-lead ECG recording, chest X-ray imaging, transthoracic echocardiography, and blood sampling as basic examinations prior to DDD pacemaker implantation. All of the CIEDs implanted had the capacity to record AHREs; 32 devices were manufactured by St. Jude Medical (Saint Paul, MN, USA), 25 devices were manufactured by Medtronic (Minneapolis, MN, USA), 18 devices were manufactured by Biotronik (Berlin, Germany), 15 devices were manufactured by Ela Medical (Montrouge, France), and 11 devices were manufactured by Boston Scientific (Marlborough, MA, USA). All patients were assessed at six-month intervals after the initial device check performed one week postimplantation. Clinical data including the presence of AHREs during the preceding six-month period were collected at each follow-up visit via device interrogation. An AHRE was defined as any episode of sustained atrial tachyarrhythmia (>5 min and >170 bpm) detected through the atrial lead (Figure 2).13 The atrial sensing threshold was set at 0.5 mV. To detect the existence of AHRE, a cutoff of five minutes or greater was employed in this study for the exclusion of over-diagnosis of various atrial signals such as far-field oversensing and/or sinus tachycardia.13 Other atrial noises were excluded by checking the intracardiac ECGs stored in the pacemakers as much as possible.3 We classified the study population as patients with and without new-onset AHRE during the initial one year after CIED implantation.