Clinical paperValue of post-resuscitation electrocardiogram in the diagnosis of acute myocardial infarction in out-of-hospital cardiac arrest patients☆
Introduction
Sudden out-of-hospital cardiac arrest (OHCA) is a severe condition with a poor survival, estimated at 33% in 19901 and 38% in 19972 in patients who were admitted to the hospital. Recent data from large studies estimate mortality rate between 58% and 86% at one month after admission to the hospital in 3,853 OHCA patients,3 and 71% in 24,132 patients admitted to intensive care units (ICU) after in-hospital or OHCA.4
It has been suggested that acute myocardial infarction (AMI) is one of the main causes of OHCA, and two studies showed that coronary angioplasty significantly improved survival rate in this setting.2, 5 Even if the role of coronary angioplasty in OHCA is still under debate,6, 7, 8, 9 making the diagnosis and treating an ongoing AMI as early as possible after OHCA would appear crucial.
One of the main criteria for AMI diagnosis in non-cardiac arrest patients is ST-elevation on electrocardiogram (ECG),10 but in patients resuscitated from OHCA, ECG changes may be difficult to interpret due to false positive and false negative results.2, 5 Indeed, acute ischemia–reperfusion syndrome after return of spontaneous circulation (ROSC) may cause myocardial injury, leading to significant ECG changes even in the absence of AMI.11, 12 Therefore, it has been suggested that ST-elevation on ECG was not contributive.2, 5 Conversely, ST-elevation had good positive (PPV) and negative (NPV) predictive values for AMI diagnosis in another study.6
Even though the diagnostic value of the ST-elevation is uncertain in the OHCA setting, we hypothesised that ECG changes may still be useful as a triage method for establishing the indication for emergency coronary angiogram (ECA). We performed a study aiming to identify ECG criteria that improve selection for ECA of the patients undergoing AMI. The need for triage is justified by the fact that not all OHCA patients benefit from the ECA7, 8 and by the limited availability and the cost of the technique. We therefore analysed different ECG criteria of patient selection, including several ECG changes in addition to ST-elevation, such as ST-depression or wide QRS complex, which are known to occur during AMI.13
Section snippets
Methods
In Paris, France, the mobile emergency medical system is based in five hospitals in the city. One centre dispatches ambulances carrying resuscitation equipment and physicians trained in emergency medicine. The ambulances reach the scene in approximately 18 min, and are generally preceded by fire-fighters trained in basic life support, who reach the OHCA scene in approximately 8.5 min.14 Patients effectively resuscitated are transferred to hospitals. In our centre, all OHCA patients with stable
Patient characteristics
The selection of the included population and the final outcome are shown in Fig. 1. Most patients were men aged 56 (48–67) y.o., and 18% had previous history of coronary artery disease. Most OHCA occurred in public places (60%). The median no flow and low flow were 3 and 20 min respectively. The initial rhythm was ventricular fibrillation (VF) in 50% of the patients (Table 1).
OHCA was caused in 36% of the cases by AMI, in 23% by ischemic heart disease without AMI (chronic coronary occlusion,
Discussion
In this series of 165 patients, the most important finding is the 100% sensitivity of the combined/extended ECG criteria for the selection of patients with AMI. This is the first evaluation of such ECG criteria in patients resuscitated from an OHCA. Few studies evaluated the characteristics of the ECG for the diagnosis of AMI in the setting of OHCA, due to the difficulties in the diagnosis of AMI by other methods.26, 28
AMI was found in 36% of our patients, being the most frequent cause of OHCA,
Conclusion
In OHCA, without obvious non cardiac cause, due to its excellent sensitivity, the combined/extended ECG criteria comprising the presence of ST-elevation and/or depression and/or LBBB and/or non-specific wide QRS and/or RBBB are easily applicable and could help in identifying patients who may benefit from ECA. Future studies are needed to confirm their value.
Conflict of interest statement
None.
Funding sources
None.
Acknowledgement
The authors wish to thank Mrs. Felicity Neilson for reviewing the English.
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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2011.04.023.
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These authors contributed equally to this work.