Objective: To determine the type and pattern of arrhythmic events following the 2012 Ahar-Varzegan Earthquake among patients implanted with cardiac defibrillators (ICDs) in East Azarbaijan province.Methods: In a prospective cohort study, conducted in East Azerbaijan Province of Iran, 132 patients were enrolled in two comparison groups according to the region of residence i.e., earthquake region (n= 98) and non-earthquake (n= 34) region in 2012. Data were collected for those meeting standard criteria for sustained ventricular arrhythmias (VAs), or supraventricular tachycardias (SVTs) and triggered ICD therapies, either shock or anti-tachycardia pacing (ATP). The state version of the State-Trait Anxiety Inventory (STAI-S) was used to assess general symptoms of anxiety in both groups.Results: Males comprised 81.1% of the participants. Mean age of the participants was 59.7 ±15 years. The frequency of patients with sustained VAs increased significantly after the earthquake (p=0.008). There were more VAs (mean 2.16 vs. 6.23; p=0.008) and they occurred earlier (6th vs. 16th day; p= 0.01) in the earthquake area. The mean frequency of SVTs and the total number of delivered ICD therapies were similar between groups. Differences in anxiety levels were not significant between groups but there was a trend for presence of greater number of patients with anxiety (p=0.07) and the relative severity of anxiety (p=0.08) in the earthquake area.Conclusion: In the earthquake area, the mean frequency of VAs increased and they occurred earlier in the earthquake area. The stress of anxiety might have served as a trigger for these events.