Temporal variation in out-of-hospital cardiac arrest with validated cardiac cause

Objective. Temporal variations in the occurrence of out-of-hospital cardiac arrest (OHCA) have been shown. Most previous studies have in common that they include individuals whom have received cardiopulmonary resuscitation (CPR) and thus excluding a great number of all the actual cases of OHCA when conducting a study. Therefore the aim of this study was to describe temporal variations of OHCA, regardless of whether CPR was performed or not. Design. All individuals aged 25-74 years in northern Sweden, 1989-2009, who suffered an out-of-hospital cardiac arrest with validated myocardial infarction aetiology (OHCA-V), regardless of whether CPR was performed or not, were included in this study, which resulted in 3357 individuals. Results. Regarding the diurnal variation, a daytime excess of OHCA-V was seen, with most occurring between 12:00-17:59 (29%) closely followed by the 06:00-11:59 time block (27%). In terms of the weekly variation, most OHCA-V was seen on Saturdays (17%), while January (11%), followed by December (9%), saw the highest incidence of the months. Conclusion. A temporal variation in OHCA-V is seen even when including cases where no CPR is attempted. However, this variation differs in some aspects to what some previous studies have shown, in that no clear morning or Monday peaks were seen. In order to explore potential triggers and underlying factors that influence OHCA, more studies like these are needed, preferably following standardized inclusion criteria and definitions of OHCA to better be able to compare results, all in order to develop the best possible preventive strategies.