Incidence, Survival and EMS-treatment of Out-of-Hospital Cardiac Arrests Related to Exercise

The Danish Emergency Medical System (EMS) introduced a nationwide registry of electronic medical reports in 2016.(1) This report system allows electronic searches and thereby the opportunity to identify subgroups of out-of-hospital cardiac arrests (OHCA). Thus, this novel reporting enables the possibility to investigate new characteristics in OHCA related to exercise.

Exercise and physical activity have been shown to reduce the risk of cardiovascular disease, in spite of this, exercise can be related to a transient increased risk of cardiac events including sudden cardiac arrest.(2) Literature have reported low annual incidences of OHCA related to exercise between 0.48 - 2.1 per 100.000 person-years. (3-7) With the proportion of OHCA related to exercise of 0.3 - 7 % of all OHCA's (4,8,9). No standardized definition of timeframe concerning OHCA related to exercise is established, but throughout the literature onset of symptoms is defined to be during or up to one hour after exercise(4,5,10,11). Overall survival rates among previous studies varies from 11 - 46.2 % (6,12), a 30-day survival rate between 5.5 - 58 % (8,13) and a survival to discharge between 15.7 - 77 % (4,5,9,10,14). Yet, data is assessed in different countries with different health care systems, in different subgroups of age and lastly throughout different periods of time. This suggests further investigations and cohesion to standardized reporting, advocating for the Utstein Reporting Template. (15) Despite conflicting results regarding survival, there is consensus that exercise related OHCA has a better prognosis compared to OHCA not related to exercise. (4-6,8-10,16,17) Another consistent finding is younger age among patients suffering from OHCA related to exercise compared to other OHCA's. (5,6,9,10,17)

The etiology is often classified as either of (presumed) cardiac etiology or of non-cardiac etiology. (15) The Utstein Model suggests a method of which the pathogenesis is categorized under either medical (presumed cardiac or unknown or other medical i.e., gastro-intestinal bleed, anaphylaxis etc.) or traumatic cause, drug overdose, drowning, electrocution or asphyxia (external). If more than one cause is potential, the most likely should be noted.(18) In addition, it is suggested, that OHCA related to exercise often is caused by a presumed cardiac etiology. (4,5,7).

A better understanding and enhanced knowledge of the epidemiology of OHCA during exercise, could be useful for appropriate handling of these situations, thus this study aims to:

• Report the national incidence of exercise related OHCA's among cases attended by the Danish Medical Emergency System (EMS).
• To assess survival defined as return of spontaneous circulation (ROSC) and 30-day survival
• Finally, to evaluate aspects associated with better outcome including localization, observation of occurrence, bystander CPR, initial rhythm, use of defibrillator and patient demographics.