Etiology of Out-of-Hospital Cardiac Arrest Among Patients Presenting to the Emergency Department of a Tertiary Care Hospital in Bhutan: A Prospective Cohort Study.

Background: High mortality rates following out-of-hospital cardiac arrest (OHCA) make identification of its etiology vital for prevention. In low-resource settings, limited access to diagnostics and clinical autopsy often prevents definitive conclusions. This study aimed to describe the presumed etiology of OHCA cases presenting to a tertiary emergency department (ED) in Bhutan. Methods: A prospective cohort study was conducted from August 1, 2023, to July 31, 2024, in the ED of the National Referral Hospital, Bhutan. All patients presenting with OHCA were included and followed until hospital discharge, death, or the end of the study period. Data were extracted from patient records and analyzed using STATA Version 18. Results: Of the 110 OHCA patients, 59.1% ( Conclusion: Most OHCA cases were medical in origin, with the majority classified as presumed cardiac/unknown due to the absence of a specific etiology after available evaluation. These findings highlight challenges in etiological classification in resource-limited settings. Strengthening postresuscitation diagnostic evaluation, standardized post-ROSC protocols, access to clinical autopsy where feasible, and development of a nationwide OHCA registry may improve etiological classification and guide future preventive strategies.