Funding Acknowledgements Type of funding sources: None. Introduction Despite the recent advancements in the management of Complete Heart Block (CHB), the aetiology of CHB is still idiopathic in most of the cases. Our study explores this hitherto untouched aspect of complete heart block. Purpose We aimed to assess the aetiological profile of Complete Heart Block patients in our study. Methods The study population consisted of 60 patients with complete heart block aged between 30 to 80 years, attending as an inpatient in ER. Oxidative stress was measured by serum MDA, serum GSH, serum Catalase activity and serum SOD activity. Antioxidant activity was obtained by measuring the levels of serum total antioxidant capacity. Inflammatory stress was measured by IL-5 and TNF-alpha levels. These values were compared to 30 healthy controls with no prior history of smoking and diabetes mellitus. Results The mean age of the patient was 62.48 ± 7.98 years and the gender distribution was 37 males and 23 females out of 60 patients. The mean value of serum MDA (ng/mL) in cases is 1451.26 ± 206.32, and in controls, the mean value is 1197.98 ± 234.71 (p= Conclusions During a complete heart block, SOD (p=0.891), CAT (p=0.003), GSH (p=0.027) and total antioxidant (TAOC) (p=0.025) were significantly decreased in cases, compared to healthy controls, thus suggesting that the elevated levels of oxidative free radicals causes endothelial dysfunctioning. The increase in ROS was observed by a highly significant increase of malondialdehyde (MDA) (p=