When reading the ECG of a patient presenting with cardiopulmonary complaints, the most important duty of acute care clinicians is to determine whether there is evidence of an acute coronary occlusion (ACO).
Patients with an ACO need immediate reperfusion therapy via cardiac catheterization with percutaneous coronary intervention or fibrinolysis. Traditional instruction has taught that patients with an ACO will demonstrate ST-segment elevation (STE) in contiguous leads on the ECG. These cases are referred to as ST-segment elevation myocardial infarction (STEMI).
Unfortunately, traditional guidance to look for STE has largely led to a dichotomy in how we have cared for patients emergently: Patients with STE in contiguous leads (presumed STEMI) have received immediate reperfusion therapy, and patients without STE in contiguous leads have simply received antiplatelet and antianginal therapy and, at best, nonemergent cardiac catheterization. The only widely accepted exception to this was when posterior STEMI was suspected. This type of STEMI tends to produce ST-segment depression in the right precordial leads; therefore, when this pattern is found, we have been taught to obtain posterior leads to verify the presence of posterior STEMI and initiate acute reperfusion therapy.
For the past two decades, however, studies have demonstrated that ACO does not always produce the classic STE in contiguous leads
