ST-Segment Deviation Analysis Of The Admission 12-Lead Electrocardiogram As An Aid To Early Diagnosis Of Acute Myocardial Infarction With A Cardiac Magnetic Resonance Imaging Gold Standard
Excerpt of article from the Journal of the American College of Cardiology, Vol. 50, No. 11, 2007.
Thomas N. Martin, MD, Bjoern A. Groenning, MD, Heather M. Murray, MSC, Tracey Steedman, BSC, John E. Foster, PHD, Alex T. Elliot, PHD, Henry J. Dargie, MD, Ronald H. Selvester, MD, Olle Pahlm, MD, PHD, Galen S. Wagner, MD
Glasgow, United Kingdom; Long Beach, California; Lund, Sweden; and Durham, North Carolina
The purpose of this study was to validate existing 12-lead electrocardiographic (ECG) ST-segment elevation myocardial infarction (STEMI) criteria in the diagnosis of acute myocardial infarction (AMI) and the application of similar ST-segment depression (STEMI-equivalent) criteria with contrast-enhanced cardiac magnetic resonance imaging (ceMRI) as the diagnostic gold standard.
The admission ECG is the cornerstone in the diagnosis of AMI, and ceMRI is a new diagnostic gold standard that can be used to validate existing and novel 12-lead ECG criteria.
One hundred fifty-one consecutive patients with their first hospital admission for chest pain underwent ceMRI. The 116 patients without ECG confounding factors were included in this study, and AMI was confirmed in 58 (50%). The admission ECG was evaluated on the basis of the lead distribution of ST-segment deviation according to current American College of Cardiology/European Society of Cardiology (ACC/ESC) guidelines.
A sensitivity of 50% and specificity of 97% for AMI were achieved with the currently applied ST-segment elevation criteria. Consideration of ST-segment depression in addition to elevation increased sensitivity for detection of AMI from 50% to 84% (p 0.0001) but only decreased specificity from 97% to 93% (p 0.50). There were no significant differences in AMI location or size between patients meeting the 12-lead ACC/ESC ST-segment elevation criteria and those only meeting the ST-segment depression criteria.
In patients admitted to hospital with possible AMI, the consideration of both ST-segment elevation and depression in the standard 12 lead-ECG recording significantly increases the sensitivity for the detection of AMI with only a slight decrease in the specificity. (J Am Coll Cardiol 2007;50:1021–8)
It is important to achieve a rapid and accurate diagnosis regarding acute myocardial infarction (AMI) in patients with symptoms suggestive of an acute coronary syndrome (ACS), and the initial electrocardiogram (ECG) is the cornerstone of this decision-making process.
Troponin T or I are very sensitive markers for AMI and are now part of routine clinical practice in the diagnosis of patients with symptoms suggesting ACS. However, the infarction is in progress by the time the current routine biomarkers are detectable in venous blood. In addition, the noncardiac causes for troponin release are well documented (1). Contrast-enhanced magnetic resonance imaging (ceMRI) with its high spatial resolution for clinical detection of AMI provides a unique gold standard for evaluation of more universally available diagnostic methods (2). Indeed, location, transmurality, and size of AMI can also be determined with precision and reproducibility (3).
Clinical decisions for initiating reperfusion therapy are typically based on ECG criteria developed in the GUSTO (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Arteries) series of trials (4); slightly revised criteria have more recently been introduced by the American College of Cardiology and the European Society of Cardiology (ACC/ESC) (5). However, it is well recognized that the sensitivities of these sets of 12-lead ECG criteria are suboptimal (6,7) An example of this deficiency is the routine under-detection of acute posterolateral myocardial infarction (MI) that is the typical result of occlusion of the left circumflex coronary artery (LCx) (8). The adverse risk associated with non–ST-segment elevation myocardial infarction (NSTEMI) is well documented (9), but many trials have failed to demonstrate the benefits of thrombolysis on the basis of alternative non–ST-segment elevation criteria (10–13). With the emergence of more targeted treatments such as percutaneous coronary intervention, the potential role of the admission ECG as a triage tool is increased.
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