Elsevier

Annals of Emergency Medicine

Volume 64, Issue 2, August 2014, Pages 176-186.e9
Annals of Emergency Medicine

Cardiology/review article
Systematic Review and Meta-analysis of the Benefits of Out-of-Hospital 12-Lead ECG and Advance Notification in ST-Segment Elevation Myocardial Infarction Patients

https://doi.org/10.1016/j.annemergmed.2013.11.016Get rights and content

Study objective

To present a review of out-of-hospital identification of ST-segment elevation myocardial infarction patients transported by emergency medical services with 12-lead ECG and advance notification versus standard or no cardiac monitoring.

Methods

EMBASE, PubMed, and the Cochrane Library were searched, using controlled vocabulary and keywords. Randomized controlled trials and observational studies were included. Outcomes included short-term mortality (≤30 days), door-to-balloon/needle time and/or first medical contact–to-balloon/needle time. Pooled estimates were determined, where appropriate. Results were stratified by percutaneous coronary intervention or fibrinolysis.

Results

The search yielded 1,857 citations, of which 68 full-texts were reviewed and 16 studies met the final criteria: 15 included data on percutaneous coronary intervention and 3 on fibrinolysis (2 included both). Where percutaneous coronary intervention was performed, out-of-hospital 12-lead ECG and advance notification was associated with a 39% reduction in short-term mortality (8 studies; n=6,339; risk ratio 0.61; 95% confidence interval 0.42 to 0.89; P=.01; I2=30%) compared with standard or no cardiac monitoring. Where fibrinolysis was performed, out-of-hospital 12-lead ECG and advance notification was associated with a 29% reduction in short-term mortality (1 study; n=17,026; risk ratio 0.71; 95% confidence interval 0.54 to 0.93; P=.01). First medical contact–to-balloon, door-to-balloon, and door-to-needle times were consistently reduced, though large heterogeneity generally precluded pooling.

Conclusion

The present study adds to previous reviews by identifying and appraising the strength and quality of a larger body of evidence. Out-of-hospital identification with 12-lead ECG and aadvance notification was found to be associated with reductions in short-term mortality and first medical contact–to-balloon, door-to-balloon, and door-to-needle time.

Introduction

In patients with ST-segment elevation myocardial infarction (STEMI), ischemic time has been shown to be positively associated with mortality.1, 2, 3, 4, 5, 6 In an effort to reduce ischemic time, many ambulances are now equipped to rapidly identify and triage a STEMI patient with the use of an out-of-hospital 12-lead ECG and advance notification. Out-of-hospital 12-lead ECG is a Class I recommendation from the American Heart Association/American College of Cardiology and is similarly recommended by the Canadian Cardiovascular Society.7, 8

Editor's Capsule Summary

What is already known on this topic

Rapid treatment of ST-elevation myocardial infarction decreases mortality and produces better outcomes.

What question this study addressed

This meta-analysis of 16 observational studies of out-of-hospital 12-lead ECG compared with 3-lead or no monitoring was performed to refine the estimated mortality benefit in the percutaneous coronary intervention era and the temporal benefit from first (out-of-hospital) medical contact to reperfusion.

What this study adds to our knowledge

Out-of-hospital 12-lead ECG was associated with a 39% reduction in relative risk of 30-day mortality for percutaneous coronary intervention patients and a 21- to 78-minute reduction in first medical contact–to-balloon time.

How this is relevant to clinical practice

The existing literature confirms an important mortality benefit of out-of-hospital 12-lead ECG and advance emergency department notification in the percutaneous coronary intervention era, limited as in all meta-analyses by the validity of the individual studies and absence of publication bias.

These recommendations were largely based on historical studies and previous reviews of the utility of out-of-hospital 12-lead ECG, but they had considerable imprecision in pooled mortality effectiveness estimates,9, 10 perhaps owing to the limited number of included studies.11, 12 Similarly, these reviews were primarily based on studies before the era of out-of-hospital triage of STEMI patients for percutaneous coronary intervention, which may enhance the effect of STEMI recognition. Finally, these reviews also included studies investigating out-of-hospital combination fibrinolysis with facilitated percutaneous coronary intervention. Current treatment guidelines, however, recommend against full-dose fibrinolytic therapy followed by routine, immediate percutaneous coronary intervention and recommend only selective use of facilitated strategies.13, 14

When assessing interventions to reduce mortality in STEMI patients, previous reviews have focused on the surrogate time-to-reperfusion outcomes of door-to-needle or door-to-balloon times.10, 15 However, in recognition that emergency medical services (EMS) play an important role in the continuum of STEMI patient care, first medical contact–to-balloon or first medical contact–to-needle time—measured from the time EMS first assesses the patient—may be a preferred measure of system performance.3, 4, 8

Despite these limitations, the strong recommendations for out-of-hospital 12-lead ECG have had an influence on its implementation in the United States, Canada, and around the world. Although the use of out-of-hospital 12-lead ECG has expanded significantly in the last 10 years, not all ambulances have this capability and thus not all STEMI patients receive an out-of-hospital 12-lead ECG.16, 17, 18

The objective of the current review was to address the aforementioned issues and present an updated review of the literature related to out-of-hospital identification of STEMI patients transported by EMS with 12-lead ECG and advance notification compared with standard or no cardiac monitoring (no out-of-hospital identification and no advance notification).

Section snippets

Materials and Methods

Reporting of the present review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.19

A search strategy was constructed with controlled vocabulary (Medical Subject Headings or Emtree) and key words focusing on the concepts of “electrocardiogram,” “advance notification,” “emergency medical services,” and “myocardial infarction.” The search was limited to English-language publications and studies of humans. Search strategies are presented in Appendix

Results

The literature search was completed December 2012, with updates until March 2013. A flow diagram of the literature search results is presented in Figure 1. After duplicates were removed, there were 1,338 unique citations. The full texts of 68 citations were screened,11, 12, 16, 17, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77,

Limitations

The present review has several limitations. Observational studies limit the quality of evidence; however, a number of studies were identified and there were no serious threats of inconsistency, imprecision, or methodological bias that would further downgrade evidence from a low quality.

Few included studies reported short-term mortality for patients who received percutaneous coronary intervention or fibrinolysis as well as first medical contact–to-reperfusion times. It is not clear whether

Discussion

We have conducted a systematic review and meta-analysis of out-of-hospital identification of STEMI patients transported by EMS with 12-lead ECG and advance notification compared with standard cardiac monitoring. Out-of-hospital 12-lead ECG and advance notification was associated with reductions in short-term mortality, first medical contact–to-balloon time, door-to-balloon time, and door-to-needle time. Overall, the quality of the evidence was low, largely because of the observational study

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    Please see page 177 for the Editor's Capsule Summary of this article.

    Supervising editor: Keith A. Marill, MD

    Author contributions: JN, JMB, MW, and DO conceived the study. JN designed and conducted the study. JMB, MW, and DO supervised all aspects of the study. KC contributed substantially with the screening process. JN drafted the article and all authors contributed substantially to its revision. JN takes responsibility for the paper as a whole.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist.

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