Sudden Cardiac Death: Epidemiology, Circadian Variation, and Triggers Karim D. Mahmoud, BSc, Bart J.G.L. de Smet, MD, Felix Zijlstra, MD, Charanjit S. Rihal, MD, and David R. Holmes Jr, MD Abstract: Sudden cardiac death (SCD) remains a major health issue accounting for over 5% of annual mortality in the Western world. There are several causes of SCD, most commonly, coronary artery disease. Although identifying the prodrome of SCD has attracted considerable interest, a large propor- tion of patients die before any medical contact is established. SCD onset seems to follow a circadian pattern, most likely because of exposure to endoge- nous and exogenous triggers. The aim of the present report is to review the current knowledge of epide- miology, patterns of onset, and triggers of SCD and present directions for future research with a focus on coronary artery disease. (Curr Probl Cardiol 2011; 36:56-80.) S udden cardiac death (SCD) remains a major health issue accounting for a significant percentage of all cardiac deaths. Furthermore, the lack of warning symptoms in SCD seems to preclude the opportunity for preventive treatment. A thorough knowl- edge of epidemiology, circadian variation, and possible triggers is essential for optimizing the possible treatment strategies to lower the incidence of SCD. Grant sponsors (to KDM): Netherlands Heart Foundation (The Hague, the Netherlands), Groningen University Fund (Groningen, the Netherlands), Marco Polo Fund (Groningen, the Netherlands), Jan Kornelis de Kock Foundation (Groningen, the Netherlands). Curr Probl Cardiol 2011;36:56-80. 0146-2806/$ – see front matter doi:10.1016/j.cpcardiol.2011.01.002 56 Curr Probl Cardiol, February 2011