STEMI Diagnosis and Management

Definition and Classification

The American College of Cardiology and American Heart Association define STEMI as new ST elevation at the J point in at least 2 contiguous leads of ≥2 mm (0.2 mV) in men or ≥1.5 mm (0.15 mV) in women in leads V2-V3, and/or ≥1 mm (0.1 mV) in other contiguous chest or limb leads 1, 2
Patients presenting with ST segment depression alone are classified as having either unstable angina or NSTEMI, not STEMI, according to the American Heart Association 3
The American College of Cardiology recommends classifying patients with ST depression alone as NSTEMI if cardiac biomarkers exceed the upper limit of normal with clinical presentation consistent with ischemia 4
The American Heart Association recommends classifying patients with ST depression alone as unstable angina if biomarkers remain normal 5, 6

The American College of Cardiology identifies true posterior MI (posterobasal infarction) as a STEMI-equivalent, characterized by ST depression in ≥2 precordial leads (V1-V4) that is maximal in V3-V6, without ST elevation in other leads 4, 2
The American Heart Association notes that this pattern represents acute occlusion of the posterior descending artery or left circumflex artery, and qualifies for immediate reperfusion therapy (fibrinolysis or primary PCI) 4, 7
Posterior chest leads (V7-V9) showing ST elevation confirm the diagnosis of true posterior MI, according to the American College of Cardiology 4

The American Heart Association states that ST depression ≥0.5 mm (0.05 mV) indicates higher risk than isolated T-wave changes or normal ECG, and that greater magnitude and number of leads with ST depression correlate with worse outcomes 5, 6
The American College of Cardiology recommends early invasive strategy and antiplatelet therapy for patients with ST depression 7
The American Heart Association advises against activating STEMI protocols for STE-aVR with multilead ST depression without confirming acute occlusion, and recommends urgent (rather than emergent) catheterization 1, 2

The American College of Emergency Physicians suggests that right ventricular involvement with inferior STEMI shows ST elevation in right-sided leads with reciprocal changes in lateral leads 8

The American Heart Association indicates that the presence of reciprocal changes does not alter the fundamental STEMI management algorithm but signals higher-risk anatomy requiring meticulous attention to complete revascularization strategies 9, 10, 11

The American College of Cardiology recommends primary PCI within 90 minutes as the preferred reperfusion strategy regardless of reciprocal changes 9, 10
The American College of Cardiology suggests fibrinolysis within 30 minutes if PCI-capable facility cannot be reached within 90 minutes 9, 10
The American Heart Association advises aspirin 162-325 mg chewed immediately unless absolute contraindication 9, 10
The American College of Cardiology recommends clopidogrel 75 mg daily should be added to aspirin in all STEMI patients with or without reciprocal changes 9, 10
The American College of Cardiology indicates that duration of clopidogrel varies by stent type: bare-metal stent (≥1 month, ideally 1 year), drug-eluting stent (1 year) 10, 11
Isolated ST depression in V1-V4 with upright terminal T-waves represents true posterior STEMI and qualifies for immediate reperfusion therapy, according to the American College of Emergency Physicians 8