Elsevier

Resuscitation

Volume 81, Issue 2, February 2010, Pages 175-181
Resuscitation

Clinical paper
Out-of-hospital cardiac arrest frequency and survival: Evidence for temporal variability

https://doi.org/10.1016/j.resuscitation.2009.10.021Get rights and content

Abstract

Aim

Some cardiac phenomena demonstrate temporal variability. We evaluated temporal variability in out-of-hospital cardiac arrest (OHCA) frequency and outcome.

Methods

Prospective cohort study (the Resuscitation Outcomes Consortium) of all OHCA of presumed cardiac cause who were treated by emergency medical services within 9 US and Canadian sites between 12/1/2005 and 02/28/2007. In each site, Emergency Medical System records were collected and analyzed. Outcomes were individually verified by trained data abstractors.

Results

There were 9667 included patients. Median age was 68 (IQR 24) years, 66.7% were male and 8.3% survived to hospital discharge. The frequency of cardiac arrest varied significantly across time blocks (p < 0.001). Compared to the 0001–0600 hourly time block, the odds ratios and 95% CIs for the occurrence of OHCA were 2.02 (1.90, 2.15) in the 0601–1200 block, 2.01 (1.89, 2.15) in the 1201–1800 block, and 1.73 (1.62, 1.85) in the 1801–2400 block. The frequency of all OHCA varied significantly by day of week (p = 0.03) and month of year (p < 0.001) with the highest frequencies on Saturday and during December. Survival to hospital discharge was lowest when the OHCA occurred during the 0001–0600 time block (7.3%) and highest during the 1201–1800 time block (9.6%). Survival was highest for OHCAs occurring on Mondays (10.0%) and lowest for those on Wednesdays (6.8%) (p = 0.02).

Conclusion

There is temporal variability in OHCA frequency and outcome. Underlying patient, EMS system and environmental factors need to be explored to offer further insight into these observed patterns.

Introduction

Out-of-hospital cardiac arrest (OHCA) is a significant public health problem, with the North American incidence of EMS-treated cardiac arrest estimated to be 52.1 per 100,000 people.1 Understanding the chronobiology of OHCA is important to clarify the immediate precipitants of sudden cardiac death, develop preventative strategies, and to optimize resource planning for the prehospital and in-hospital response to cardiac arrest.

Several potential triggers for cardiac arrest have demonstrated circadian variability. Examples include physical activity, psychological stress, increases in heart rate, blood pressure and sympathetic tone, reduced fibrinolytic activity, and increased platelet aggregation.2 Epidemiological reports support underlying chronobiological mechanisms for cardiac arrest, demonstrating circadian,3, 4, 5, 6, 7, 8, 9, 10 circaseptan8, 9, 11 and circannual8, 9 variability in the frequency of OHCA. However, few studies have used a geographically diverse, population-based prospective registry of EMS-attended cardiac arrest as the basis for reporting. Furthermore, few studies have investigated whether survival from OHCA varies according to time of day, day of week or month of year. Patient characteristics, arrest circumstances, and treatment could vary according to time period and could in turn influence the likelihood of survival.12

The objective of this investigation was to evaluate temporal variability in the frequency and outcome of OHCA in a large, heterogeneous and unselected population.

Section snippets

Methods

Ethics approval for this study was obtained from 74 US Institutional Review Boards and 34 Canadian Research Ethics Boards as well as 26 EMS Services Institutional Review Boards.

Description of the cohort

There were 23,313 OHCAs occurring within the 9 participating ROC sites from December 1, 2005 to February 28 2007. Four hundred fifty cases (1.9%) were excluded for missing data. Only 57.5% of these patients were treated by EMS. Nine thousand six hundred sixty-seven patients met criteria for inclusion in the study (Fig. 1). Overall survival to hospital discharge was 8.3%.

Demographics, cardiac arrest characteristics and EMS response characteristics by time block are shown in Table 1. The initial

Discussion

In this large, population-based, multisite study using data from the Resuscitation Outcomes Consortium Epistry—Cardiac Arrest, we observed temporal variability in OHCA occurrence and outcome. These temporal observations provide a framework to advance our understanding of the triggers of OHCA. Such a framework can potentially improve resuscitation care through EMS resource planning and cardiac arrest research which incorporates this phenomenon as a potential variable affecting the risk for

Conclusion

In the Resuscitation Outcomes Consortium Epistry database, there is evidence for circadian variability in OHCA frequency with a daytime excess of out-of-hospital cardiac arrests an overnight nadir. Although OHCA frequency also varies significantly by day of week and month of year with most occurring on Saturdays and during December, there are no clear trends with respect to weekday versus weekend or across seasons of the year. Survival to hospital discharge varies by hour of day and is least

Conflict of interest statement

Steven Brooks, Robert Schmicker, Thomas Rea, Laurie Morrison, Ritu Sahni, Denise Griffiths, Scott Emerson and George Sopko have no disclosures relevant to this manuscript.

Tom P. Aufderheide is a paid consultant for Medtronics Inc. and JoLife. He sits on the Board of Directors for Take Heart America. He has received honoraria from EMS Today.

Daniel P. Davis has received an unrestricted research grant from Zoll Medical for an investigator-initiated study. He is a paid consultant to Cardinal Health.

Acknowledgements

The Resuscitation Outcome Consortium (ROC) is supported by a series of cooperative agreements to 10 regional clinical centers and one data Coordinating Center (5U01 HL077863, HL077881, HL077871 HL077872, HL077866, HL077908, HL077867, HL077885, HL077885, HL077863) from the National Heart, Lung and Blood Institute in partnership with the National Institute of Neurological Disorders and Stroke, The Canadian Institutes of Health Research (CIHR)—Institute of Circulatory and Respiratory Health,

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