Consideration of Pitfalls in and Omissions from the Current ECG Standards for Diagnosis of Myocardial Ischemia/Infarction in Patients Who Have Acute Coronary Syndromes

Pitfalls have been identified in the current standards for use of the ECG in patients presenting with symptoms of acute coronary syndromes to identify those who have probable acute coronary thrombosis-induced myocardial ischemia/infarction. Indeed, there are pitfalls in every aspect of standards for the use of this common but inexpensive method for diagnosing this common but critical clinical problem. The acute ischemia/infarction diagnostic criteria require identification of two contiguous leads, even though the classic display fails to present the limb leads in the same orderly sequence as the chest leads. These criteria require the presence of ST elevation even though acute occlusion of several branches of the coronary arteries, and even of the main left coronary artery, can produce only ST depression in the 12 lead ECG. These criteria have continued to be age and gender nonspecific until corrected in new standards documents. There have been inconsistencies in the terms used to designate the involved myocardial regions, with retention of terms such as "posterior," even though myocardial imaging methods have documented more in-vivo correct alternative terms. Algorithms for identification of key aspects of the ischemia/infarction process including extent, acuteness, and severity that are too detailed for routine manual application have not been incorporated into commercial ECGs, even though they have been well documented in the literature for 10 to 20 years. Additional studies are needed to validate these indices using non-ECG reference standards. Unfortunately historical time from symptom onset is not a sufficiently accurate estimate of the time of the acute coronary occlusion, and formerly available clinical imaging methods have lacked the precision to serve as standards for ischemia/infarction extent and severity. As additional studies of these indices emerge, future working groups of the international cardiovascular societies will have the opportunity to consider their adoption as new standards for ECG evaluation of individuals who have acute coronary syndromes and who might benefit from reperfusion before their ischemic myocardium undergoes irreversible infarction.