Elsevier

Resuscitation

Volume 83, Issue 11, November 2012, Pages 1358-1362
Resuscitation

Clinical paper
Out-of-hospital cardiac arrest outcomes stratified by rhythm analysis,☆☆

https://doi.org/10.1016/j.resuscitation.2012.03.033Get rights and content

Abstract

Background

Survival data for out-of-hospital cardiac arrest (OHCA) victims initially in PEA or asystole who convert to a shockable rhythm during attempted resuscitation, relative to an initial shockable rhythm, have never been previously reported. This study was done to assess OHCA outcomes among a large cohort of adults in the CARES dataset stratified by three rhythm categories: initial shockable (IS), converted shockable (CS), and never shockable (NS).

Methods

The study was IRB approved. All adult index events at participating sites (2005–2010) were study eligible. All patient data elements were provided. Odds ratios of CS and NS status for survival to hospital discharge were calculated via multivariate logistic regression that adjusted for demographics, site, resuscitation initiators, AED use, and other covariates.

Results

There were 40,274 OHCA records submitted to the CARES registry during the study period. After exclusions, our final sample size was 30,939 (7404 IS [23.9%], 3225 CS [10.4%], 20,310 NS [65.7%]). Raw survival rates of CS and NS patients were similar (4.7% vs. 4.1%, respectively; p = 0.08) but significantly lower than IS patients (26.9%; p < 0.001). The adjusted OR of survival to hospital discharge for CS was 0.17 (95%CI: 0.14, 0.20) and for NS it was 0.17 (95%CI: 0.15, 0.18) with IS as the referent.

Conclusion

After OHCA, the survival rate for CS victims is significantly lower than for IS patients. These findings suggest that CS and IS are different entities and that alternatives to existing resuscitation algorithm tailored to patients with CS should be investigated.

Introduction

Cardiopulmonary arrest is defined by one of four rhythms on surface electrocardiogram: pulseless ventricular tachycardia (pVT), ventricular fibrillation (VF), pulseless electrical activity (PEA), or asystole. Two of these, pVT and VF, are classified as shockable rhythms while PEA and asystole are non-shockable rhythms. Among out-of-hospital cardiac arrest (OHCA) patients with a first recorded rhythm (FRR) of PEA or asystole, conversion to a shockable rhythm can occur during attempted resuscitation.

Currently, when a non-shockable rhythm converts to a shockable rhythm during resuscitation efforts, immediate defibrillation (aka rescue shock [RS]) is recommended, regardless of arrest duration or underlying myocardial physiology. There are no treatments specifically directed at pVT/VF under these circumstances.

Controversy exists regarding the appropriateness of this approach because alternatives have never been studied. The authors of a recent study have suggested that such patients derive no benefit from defibrillation attempts and that new treatment strategies may be necessary.1 Results from three subsequent studies contradict this assertion,2, 3, 4 and conclude that current treatment recommendations are adequate.5

This study was done to compare resuscitation outcomes in OHCA among a large cohort of adults in the Cardiac Arrest Registry to Enhance Survival (CARES [https://mycares.net]) dataset stratified by three rhythm categories: initial shockable (IS), converted to shockable (CS), and never shockable (NS) to help clarify this issue. We hypothesized that outcomes in OHCA would vary based upon the first recorded ECG rhythm as follows: the most favorable outcomes would occur after a FRR of pVT/VF, intermediate outcomes would occur in patients with FRR of PEA or asystole who subsequently receive a defibrillation attempt during resuscitation efforts, and the worst outcomes would occur after persistent PEA or aystole.2, 3, 4

Section snippets

Methods and statistical analysis

The study was reviewed and approved by the Baystate Health Institutional Review Board (BH-10-223) through expedited review.

Results

There were 40,274 OHCA records submitted to the CARES registry during the study period. After non-cardiac etiology arrests (1867 trauma, 1175 respiratory, 206 drowning, 26 electrocution, and 3306 other) and cases of missing hospital outcomes (n = 8380) were screened out, 31,894 OHCA records were provided for evaluation. Further excluding patients under the age of 18 and those with missing or unknown mortality outcome (n = 885), missing or unspecified FRR (n = 47), and missing or “no resuscitation

Discussion

This is the first large-scale study done to compare resuscitation outcomes in OHCA among adults stratified by all 3 of the rhythm groups (IS, CS, and NS). We found that outcomes in OHCA vary based upon the first recorded ECG rhythm. The most favorable outcomes occur after a FRR of pVt/VF, and less favorable outcomes occur in patients with FRR of PEA or asystole whether or not a defibrillation attempt occurs during resuscitation efforts.

Currently, the treatment of CS and IS rhythms do not

Conclusion

We conclude that for OHCA, the survival rate for converted shockable cardiac arrest victims is significantly lower than for initial shockable patients based on a rigorous multivariable analysis on a large, validated database of recent OHCA cases. Further, stratification by non-shockable first recorded rhythm types suggests differences between subgroups as well. These findings support the contention that converted shockable and initial shockable rhythms may not be the same. The major implication

Conflict of interest statement

None of the authors have a conflict of interest to report.

Acknowledgements

The Cardiac Arrest Registry to Enhance Survival (CARES) is funded by grant support from the Center for Disease Control and Prevention (CDC) MM-0917-05. The American Association of Medical Colleges is the grant administer of CARES. This analysis was funded by a project grant from the Laerdal Foundation for Acute Care Medicine.

References (13)

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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2012.03.033.

☆☆

Prior presentation: The American Heart Association Resuscitation Science Symposium. November 2010. Chicago, IL. The National Association of EMS Physicians. January 2011. Bonita Springs, FL.

1

For the CARES Surveillance Group.

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