Cardiology/original researchThe Accuracy of an Out-of-Hospital 12-Lead ECG for the Detection of ST-Elevation Myocardial Infarction Immediately After Resuscitation
Introduction
It is estimated that about one third of all patients experiencing an acute myocardial infarction die out of hospital in the field.1, 2, 3 Often, the so-called sudden cardiac death is the first and only symptom of coronary heart disease. Substantial progress has been made in the treatment of acute myocardial infarction in recent years. Different reperfusion strategies, newly developed antiplatelet agents, antithrombins, and improved preventive therapies have reduced inhospital mortality of myocardial infarction. However, there has been almost no reduction of the out-of-hospital case-fatality rate.4, 5
The prognosis of out-of-hospital cardiac arrest is poor, with a survival rate of less than 10%.6 Epidemiologic studies on the cause of arrest in patients with sudden cardiac death are difficult because autopsy rates are low in most countries and nearly zero in some countries such as Germany. Ventricular fibrillation, the most common arrhythmia underlying sudden cardiac death in adults, is triggered by cardiac ischemia.7 Correspondingly, in most patients, sudden cardiac death is caused by severe coronary heart disease.8, 9, 10 However, it is unclear in which percentage of patients sudden cardiac death is actually caused by acute ST-elevation myocardial infarction (STEMI).
The sensitivity of an out-of-hospital 12-lead ECG for the routine diagnosis of STEMI is about 70%, with an approximately 90% specificity in patients.11, 12, 13, 14, 15, 16, 17, 18 Prolonged ischemia, medication, and electrical countershocks during resuscitation may induce ECG alterations of variable extent, which may reduce its diagnostic reliability.19, 20 ST elevation (or a presumably new left bundle-branch block in symptomatic patients) in 2 or more contiguous leads in the ECG is by definition the principal diagnostic criterion of STEMI. According to the guidelines, reperfusion therapy in STEMI should be initiated as soon as possible after verification of the diagnosis.21, 22
To our knowledge, it has not yet been investigated whether it is possible to establish the diagnosis of STEMI with sufficient reliability on the basis of an ECG recorded immediately after the return of spontaneous circulation after out-of-hospital resuscitation from sudden death of assumed cardiac origin. We sought to determine the test characteristics of an out-of-hospital ECG registered immediately after return of spontaneous circulation.
Section snippets
Study Design
For the purpose of this prospective study, sudden cardiac death was defined as sudden and unexpected circulatory arrest of assumed cardiac origin, irrespective of the duration of preceding symptoms. Patients in whom resuscitation was attempted for clearly noncardiac reasons (eg, trauma, suicide, intoxication) were excluded from the study. If a noncardiac cause for resuscitation was recognized retrospectively, the patient was also excluded from the analysis.
Setting
Consecutive patients were included by
Results
From June 2002 to August 2004, we observed a total of 808 patients with an out-of-hospital cardiac arrest. Fifteen patients were primarily excluded from the study because of noncardiac causes of arrest (4 drowning, 4 intoxication, 7 trauma). One patient was retrospectively excluded because of diagnosis of intoxication. None of the patients had signs of myocardial infarction during the hospital course. In 362 patients, the resuscitation attempt was unsuccessful, and in 340 patients no
Limitations
Our study has several limitations. First, the registration of out-of-hospital ECG and interpretation was done by experienced physicians (two thirds internists and one third anesthesiologists). It remains unclear whether other providers may achieve similar or identical results. An alternative to ECG interpretation could be radio or telephone transmission to a hospital-based physician who may also decide on specific therapeutic procedures.
Second, a selection bias of patients cannot be excluded.
Discussion
In this study, we wanted to evaluate the significance of a standard 12-lead ECG registered immediately after successful out-of-hospital resuscitation in relation to the final diagnosis of acute ST-elevation myocardial infarction. This study was not designed or powered to differentiate between different patient groups prone to the underlying qualifying event for the out-of-hospital sudden cardiac death (eg, non ST-elevation myocardial infarction or STEMI). Previous studies have demonstrated a
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Cited by (0)
Supervising editor: Judd E. Hollander, MD
Author contributions: DM, JB, and H-RA participated in the design of the study. DM, LS, and H-RA participated in patient recruitment. DM, LS, and JB conducted patient follow-up. DM, LS, and H-RA participated in preparation of the manuscript. DM 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 that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.
Publication dates: Available online August 22, 2008.
Reprints not available from the authors.