From the Guidelines
Diagnosis of Myocardial Infarction (MI)
The diagnosis of a myocardial infarction (MI) requires ST-segment elevation of at least 1 mm (0.1 mV) in two or more contiguous leads, with higher thresholds in leads V2 and V3, specifically 2 mm (0.2 mV) for men and 1.5 mm (0.15 mV) for women 1.
- The European Society of Cardiology (ESC) and the American College of Cardiology (ACC) endorse these criteria for the diagnosis of ST-elevation myocardial infarction (STEMI) 1.
- The American Heart Association (AHA) also supports these guidelines, emphasizing the importance of prompt diagnosis and treatment of STEMI 1.
- It is essential to note that these criteria are used in the context of symptoms consistent with myocardial ischemia, such as persistent chest pain, and that the diagnosis of STEMI should be made based on a combination of clinical presentation and electrocardiographic findings 1.
- In cases where the electrocardiogram (ECG) is equivocal or does not show evidence to support the clinical suspicion of MI, ECGs should be repeated, and when possible, compared with previous recordings 1.
- The use of right precordial leads (V3R and V4R) and posterior chest leads (V7 to V9) may be helpful in identifying right ventricular involvement and posterior MI, respectively 1.
- Immediate treatment for STEMI may include aspirin 162-325 mg orally, clopidogrel 600 mg orally, and consideration for urgent reperfusion therapy such as thrombolysis or primary percutaneous coronary intervention (PCI).
From the Research
ST Elevation Myocardial Infarction (MI) Diagnosis
- The amount of ST elevation necessary for a myocardial infarction (MI) is not explicitly stated in the provided studies 2, 3, 4, 5, 6.
- However, it is well accepted that early reperfusion is beneficial in patients with acute myocardial infarction presenting with ST elevation (STE) 4.
- The American College of Cardiology/American Heart Association guidelines for the treatment of STE acute myocardial infarction (STEMI) emphasize that the physician at the emergency department should make reperfusion decisions within 10 minutes of performing the initial electrocardiogram (ECG) 4.
Differentiation between STEMI and Nonischemic ST Elevation
- Not all ECGs with STE necessarily reflect transmural infarction from acute thrombotic occlusion of an epicardial coronary artery, as a large number of patients presenting with compatible symptoms have baseline STE 4.
- Differentiating between true STEMI and nonischemic ST elevation (NISTE) may be difficult, and further studies are needed to assess the ability of various ECG criteria to accurately differentiate between STEMI and NISTE 4.
Management of STEMI
- The use of adjuvant therapy with antiplatelet and anticoagulant agents is essential to enhance the results of reperfusion, and/or maintain vessel patency following either mode of reperfusion 2.
- Reperfusion therapy by primary percutaneous coronary intervention (PCI) reduces mortality and the risk of reinfarction, beyond the benefits achieved by fibrinolysis, especially when the primary PCI is initiated within 90 minutes of first medical contact 2.