Review of:M ller D, Schnitzer L, Brandt J, et al: "The accuracy of an out-of-hospital 12-lead ECG for the detection of ST-elevation myocardial infarction immediately after resuscitation." Annals of Emergency Medicine. 52(6):658-64, 2008.
This study from an EMS agency in Berlin attempted to determine the predictive value of a 12-lead ECG obtained immediately following return of spontaneous circulation (ROSC) after cardiac arrest resuscitation. The 12-leads were interpreted by on-scene physicians, and a second 12-lead was obtained at the emergency department (ED). The diagnosis of myocardial infarction (MI) was confirmed in 84% of the 77 patients who survived to hospital admission. The sensitivity of the out-of-hospital ECG was 88% (95% confidence interval [CI] 74% to 96%), the specificity 69% (95% CI 51% to 83%), the positive predictive value 77% (95% CI 62% to 87%) and the negative predictive value 83% (95% CI 64% to 87%). The accuracy of the out-of-hospital ECG and that registered on admission was the same.
The diagnosis of MI was confirmed by characteristic ECG changes, diagnostic cardiac enzyme levels, angiographic evidence and/or autopsy findings. Of the patients, the diagnosis of 44 was made by a combination of these criteria with 20 patients undergoing angiography.
The authors conclude, "The diagnosis of STEMI can be established in the field immediately after return of spontaneous circulation in most patients. This may enable an early decision about reperfusion therapy, ie, immediate out-of-hospital thrombolysis or targeted transfer for percutaneous coronary intervention."
This study provides further confirmation that sudden cardiac arrest is often caused by acute MI. There has been debate as to whether the ischemia that occurs during cardiac arrest can cause the STEMI changes in the 12-lead, and while this can't be completely excluded, this study would seem to refute that.
The fact that the ED and EMS 12-leads were the same would indicate that there is no need to add this procedure, which is time and manpower intensive, to our protocols. However, this study suggests that we should be transporting all patients with ROSC to facilities with primary intervention capability. With the growing amount of literature supporting post-resuscitation hypothermia and delivery to a cardiac arrest center, this study further confirms that if we're going to save their hearts, it's going to be with emergent catheterization because the complication associated with lytics would be increased following prolonged CPR.
One last interesting note on this article is that the physicians used 1 mm of ST elevation in the inferior leads but 2 mm in the precordial leads for diagnosis of infarction. Studies have shown that using 1 mm for both increases the sensitivity but captures a significant number of additional STEMIs. It would be interesting to know how this would've impacted the 77 patients in this study.